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Stacking Fault Nucleation in Films of Vertically Oriented Multiwall Carbon Nanotubes by Pyrolysis of Ferrocene and Dimethyl Ferrocene at a Low Vapor Flow Rate
Cocoa Pod Husk Carbon Family for Biogas Upgrading: Preliminary Assessment Using the Approximate Adsorption Performance Indicator
Development and Characterization of Biomass-Derived Carbons for the Removal of Cu²⁺ and Pb²⁺ from Aqueous Solutions
Adsorption of Asymmetric and Linear Hazardous Gases on Graphene Oxides: Density Functional Study
Fluorination to Enhance the Tribological Properties of Carbonaceous Materials

Journal Description

C — Journal of Carbon Research

C — Journal of Carbon Research is an international, scientific, peer-reviewed, open access journal on carbon research, published quarterly online by MDPI. The Spanish Carbon Group (GEC) is affiliated with C — Journal of Carbon Research and its members receive discounts on article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within ESCI (Web of Science), Scopus, CAPlus / SciFinder, and other databases.
Journal Rank: JCR - Q2 (Materials Science, Multidisciplinary)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 23.7 days after submission; acceptance to publication is undertaken in 2.8 days (median values for papers published in this journal in the second half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 3.9 (2023); 5-Year Impact Factor: 4.0 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2311-5629

Latest Articles

21 pages, 5290 KiB

Open AccessArticle

Historical Drivers and Reduction Paths of CO₂ Emissions in Jiangsu’s Cement Industry

by Kuanghan Sun, Jian Sun, Changsheng Bu, Long Jiang and Chuanwen Zhao

C 2025, 11(1), 20; https://doi.org/10.3390/c11010020 - 5 Mar 2025

With global climate challenges intensifying, the cement industry, as a major CO₂ emitter, has attracted significant attention regarding its emission reduction potential and strategies. Advanced economies like the European Union use carbon pricing to spur innovation, while emerging countries focus on incremental [...] Read more.

With global climate challenges intensifying, the cement industry, as a major CO₂ emitter, has attracted significant attention regarding its emission reduction potential and strategies. Advanced economies like the European Union use carbon pricing to spur innovation, while emerging countries focus on incremental solutions, such as fuel substitution. Combining LMDI decomposition and the LEAP model, this study examines Jiangsu Province as a test bed for China’s decarbonization strategy, a highly efficient region with carbon intensity 8% lower than the national average. Historical analysis identifies carbon intensity, energy mix, energy intensity, output scale, and economic effects as key drivers of emission changes. Specifically, the reduction in cement production, real estate contraction, lower housing construction, and reduced production capacity are the main factors curbing emissions. Under an integrated technology strategy—including energy efficiency, fuel and clinker substitution, and CCS—CO₂ emissions from Jiangsu’s cement sector are projected to decrease to 17.28 million tons and 10.9 million tons by 2060 under high- and low-demand scenarios, respectively. Clinker substitution is the most significant CO₂ reduction technology, contributing about 60%, while energy efficiency gains contribute only 3.4%. Despite the full deployment of existing reduction methods, Jiangsu’s cement industry is expected to face an emissions gap of approximately 10 million tons to achieve carbon neutrality by 2060, highlighting the need for innovative emission reduction technologies or carbon trading to meet carbon neutrality goals. Full article

(This article belongs to the Section Carbon Cycle, Capture and Storage)

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Full article ">Figure 1
<p>Geographical area map of Jiangsu Province.</p> Full article ">Figure 2
<p>LMDI-LEAP composite model logic diagram.</p> Full article ">Figure 3
<p>The energy consumption and CO<sub>2</sub> emissions of Jiangsu’s cement industry (2012–2022).</p> Full article ">Figure 4
<p>Effects of driving forces for CO<sub>2</sub> emissions increment in Jiangsu’s cement industry (the definition of the relevant parameters can be found in the nomenclature).</p> Full article ">Figure 5
<p>Cement yield and related factors analyzed by (<b>a</b>) FAI and (<b>b</b>) Gompertz models.</p> Full article ">Figure 6
<p>Changes in cement CO<sub>2</sub> emissions trends in high-demand setting: (<b>a</b>) technology freezing (<b>b</b>) energy efficiency improvement; (<b>c</b>) fuel substitution; (<b>d</b>) clinker substitution; (<b>e</b>) CCS technology application; (<b>f</b>) technology integration.</p> Full article ">Figure 7
<p>Changes in cement CO<sub>2</sub> emissions trends under low-demand setting: (<b>a</b>) technology freezing; (<b>b</b>) energy efficiency improvement; (<b>c</b>) fuel substitution; (<b>d</b>) clinker substitution; (<b>e</b>) CCS technology application; (<b>f</b>) technology integration.</p> Full article ">Figure 8
<p>Different technology-related CO<sub>2</sub> emissions reduction scenarios of cement industry, (<b>a</b>) High-demand setting and (<b>b</b>) Low-demand setting.</p> Full article ">Figure 9
<p>Influence of technology variables on emission reduction potential under integrated-technology scenario: (<b>a</b>) fuel substitution, (<b>b</b>) clinker substitution, (<b>c</b>) CCS diffusivity, and (<b>d</b>) high technical level.</p> Full article ">

22 pages, 10051 KiB

Open AccessArticle

Reuse of Activated Carbons from Filters for Water Treatment Derived from the Steam Cycle of a Nuclear Power Plant

by Beatriz Ledesma Cano, Eva M. Rodríguez, Juan Félix González González and Sergio Nogales-Delgado

C 2025, 11(1), 19; https://doi.org/10.3390/c11010019 - 3 Mar 2025

Nuclear energy has a great impact on the global energy mix. In Spain, it supplies over 20% of current energy requirements, demonstrating the relevance of nuclear power plants. These plants generate different types of waste (apart from radioactive) that should be managed. For [...] Read more.

Nuclear energy has a great impact on the global energy mix. In Spain, it supplies over 20% of current energy requirements, demonstrating the relevance of nuclear power plants. These plants generate different types of waste (apart from radioactive) that should be managed. For instance, the activated carbon included in filters (which neutralize isotopes in a possible radioactive leakage) should be periodically replaced. Nevertheless, these activated carbons might present long service lives, as they have not undergone any adsorption processes. Consequently, a considerable amount of activated carbon can be reused in alternative processes, even in the same nuclear power plant. The aim of this work was to assess the use of activated carbons (previously included in filters to prevent possible radioactive releases in primary circuits) for water treatment derived from the steam cycle of a nuclear power plant. A regeneration process (boron removal) was carried out (with differences between untreated carbon and after treatments, from S_BET = 684 m² g⁻¹ up to 934 m² g⁻¹), measuring the adsorption efficiency for ethanolamine and triton X-100. There were no significative results that support the adsorption effectiveness of the activated carbon tested for ethanolamine adsorption, whereas a high adsorption capacity was found for triton X-100 (q_L1 = 281 mg·g⁻¹), proving that factors such as porosity play an important role in the specific usage of activated carbons. Full article

(This article belongs to the Special Issue Carbon-Based Materials Applied in Water and Wastewater Treatment)

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Figure 1
<p>Distribution of nuclear power plants around the world [<a href="#B10-carbon-11-00019" class="html-bibr">10</a>].</p> Full article ">Figure 2
<p>Example of the role of activated carbon in a nuclear power plant.</p> Full article ">Figure 3
<p>Scheme for boron removal in a column.</p> Full article ">Figure 4
<p>Experimental scheme for pyrolysis of activated carbon.</p> Full article ">Figure 5
<p>Nitrogen gas adsorption–desorption isotherms for different activated carbons.</p> Full article ">Figure 6
<p>SEM images for ACApyrolysis activated carbon at different magnification levels: (<b>a</b>) 200 times; (<b>b</b>) 1500 times; (<b>c</b>) 2500 times.</p> Full article ">Figure 7
<p>FT-IR absorption bands for ACApyrolysis.</p> Full article ">Figure 8
<p>Calibration curve for B determination.</p> Full article ">Figure 9
<p>Comparison between different concentrations for B removal.</p> Full article ">Figure 10
<p>Amount of desorbed B over time with different HCl concentrations: (<b>a</b>) 0.1 M; (<b>b</b>) 0.05 M. Adjustment to pseudo-first- and pseudo-second-order models.</p> Full article ">Figure 11
<p>Adsorption isotherm of TX-100 on ACApyrolysis.</p> Full article ">Figure 12
<p>Kinetic curve of TX-100 adsorption from ACApyrolysis.</p> Full article ">

17 pages, 4652 KiB

Open AccessArticle

A New Monohydrogen Phosphate-Selective Carbon Composite Membrane Electrode for Soil Water Samples

by Ozlem Tavukcuoglu, Vildan Erci, Fatih Ciftci, Ibrahim Isildak and Muhammed Zahid Kasapoglu

C 2025, 11(1), 18; https://doi.org/10.3390/c11010018 - 1 Mar 2025

This study focused on developing a novel composite phosphate-selective electrode for on-site and real-time applications using a silver polyglutaraldehyde phosphate and carbon nanotube (CNT) matrix. CNT-silver polyglutaraldehyde phosphate compound was synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray [...] Read more.

This study focused on developing a novel composite phosphate-selective electrode for on-site and real-time applications using a silver polyglutaraldehyde phosphate and carbon nanotube (CNT) matrix. CNT-silver polyglutaraldehyde phosphate compound was synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The potentiometric performance of the composite phosphate-selective electrode was then investigated. The results demonstrated that the composite phosphate-selective electrode exhibited good sensitivity, with a linear response in the concentration range of 1.0 × 10⁻⁴ to 1.0 × 10⁻² M for phosphate ions. The electrode also showed high selectivity towards phosphate ions compared to other anions, such as chloride and nitrate. Additionally, the electrode displayed a quick response time of less than 15 s, making it suitable for real-time measurements. The electrode was applied to surface and soil water samples. The results obtained from the water samples showed a strong correlation with those obtained from the preferred spectrophotometry method, highlighting the potential of the developed electrode for on-site and continuous monitoring of phosphate and offering an efficient and practical solution for various fields that require phosphate detection. Full article

(This article belongs to the Special Issue Carbon-Based Materials Applied in Water and Wastewater Treatment)

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Full article ">Figure 1
<p>(<b>a</b>) FTIR spectrum of Ag-pGAP, CNT, and CNT-Ag-pGAP. (<b>b</b>) TGA graphs of Ag-pGAP and CNT-Ag-pGAP.</p> Full article ">Figure 2
<p>SEM images of (<b>a</b>) Ag-pGAP, (<b>b</b>) CNT, and (<b>c</b>) CNT/Ag-pGAP.</p> Full article ">Figure 3
<p>XRD spectra of Ag-pGAP, CNT, and CNT/Ag-pGAP.</p> Full article ">Figure 4
<p>Potentiometric behavior of composite phosphate-selective electrode prepared with Ag-pGAP of composition.</p> Full article ">Figure 5
<p>(<b>a</b>) Potentiometric behavior of the composite phosphate-selective electrode with Composition 2 towards ions HPO<sub>4</sub><sup>2−</sup>, Cl<sup>−</sup>, CH<sub>3</sub>COO<sup>−</sup>, Cu<sup>2+</sup>, SO<sub>4</sub><sup>2−</sup>, HCO<sub>3</sub><sup>−</sup>, and NO<sub>3</sub><sup>−</sup> (<b>b</b>) Calibration graph employed for determining the selectivity coefficient of the composite phosphate-selective electrode of Composition 2.</p> Full article ">Figure 6
<p>Reproducibility assessment of the composite phosphate-selective electrode with Composition 2, fabricated using Ag-pGAP.</p> Full article ">Figure 7
<p>Response time of the composite phosphate-selective electrode prepared with Ag-pGAP, utilizing Composition 2.</p> Full article ">Figure 8
<p>Bland–Altman plot obtained for the phosphate values for the comparison of measurement techniques.</p> Full article ">Figure 9
<p>Regression plot obtained for the phosphate values for the comparison of measurement techniques. CI and PI represent 95% confidence intervals and prediction intervals, respectively.</p> Full article ">

15 pages, 10623 KiB

Open AccessArticle

Optical Transitions Dominated by Orbital Interactions in Two-Dimensional Fullerene Networks

by Haonan Bai, Xinwen Gai, Yi Zou and Jingang Wang

C 2025, 11(1), 17; https://doi.org/10.3390/c11010017 - 25 Feb 2025

Fullerenes are a class of highly symmetric spherical carbon materials that have attracted significant attention in optoelectronic applications due to their excellent electron transport properties. However, the isotropy of their spherical structure often leads to disordered inter-sphere stacking in practical applications, limiting in-depth [...] Read more.

Fullerenes are a class of highly symmetric spherical carbon materials that have attracted significant attention in optoelectronic applications due to their excellent electron transport properties. However, the isotropy of their spherical structure often leads to disordered inter-sphere stacking in practical applications, limiting in-depth studies of their electron transport behavior. The successful fabrication of long-range ordered two-dimensional fullerene arrays has opened up new opportunities for exploring the structure–activity relationship in spatial charge transport. In this study, theoretical calculations were performed to analyze the effects of different periodic arrangements in two-dimensional fullerene arrays on electronic excitation and optical behavior. The results show that HLOPC₆₀ exhibits a strong absorption peak at 1050 nm, while TLOPC₆₀ displays prominent absorption features at 700 nm and 1300 nm, indicating that their electronic excitation characteristics are significantly influenced by the periodic structure. Additionally, analyses of orbital distribution and the spatial electron density reveal a close relationship between carrier transport and the structural topology. Quantitative studies further indicate that the interlayer interaction energies of the HLOPC₆₀ and TLOPC₆₀ arrangements are −105.65 kJ/mol and −135.25 kJ/mol, respectively. TLOPC₆₀ also exhibits stronger dispersion interactions, leading to enhanced interlayer binding. These findings provide new insights into the structural regulation of fullerene materials and offer theoretical guidance for the design and synthesis of novel organic optoelectronic materials. Full article

(This article belongs to the Special Issue High-Performance Carbon Materials and Their Composites)

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Full article ">Figure 1
<p>Structural diagram of HLOPC<sub>60</sub> (<b>A</b>) and TLOPC<sub>60</sub> (<b>B</b>).</p> Full article ">Figure 2
<p>(<b>A</b>) Absorption spectrum of HLOPC<sub>60</sub>. S<sub>3</sub> (<b>B</b>), S<sub>19</sub> (<b>C</b>), S<sub>70</sub> (<b>D</b>), S<sub>82</sub> (<b>E</b>) and S<sub>144</sub> (<b>F</b>) are the CDDs of each excited state. The red and blue isosurfaces represent the electron and hole, respectively.</p> Full article ">Figure 3
<p>(<b>A</b>) Absorption spectrum of TLOPC<sub>60</sub>. S<sub>29</sub> (<b>B</b>), S<sub>50</sub> (<b>C</b>), S<sub>134</sub> (<b>D</b>), S<sub>152</sub> (<b>E</b>) and S<sub>176</sub> (<b>F</b>) are the CDDs of each excited state. The red and blue isosurfaces represent the electron and hole, respectively.</p> Full article ">Figure 4
<p>Empty orbitals (<b>A</b>) and occupied orbitals (<b>B</b>) that make major contributions in each excited state of HLOPC<sub>60</sub>.</p> Full article ">Figure 5
<p>Empty orbitals (<b>A</b>) and occupied orbitals (<b>B</b>) that make major contributions in each excited state of TLOPC<sub>60</sub>.</p> Full article ">Figure 6
<p>(<b>A</b>) Real-space functions (electron density (i), energy density (ii), potential energy density (iii), Laplacian electron density (iv), Hamiltonian kinetic energy (v), and electron localization function (vi)) at critical points. Grey and red represent HLOPC<sub>60</sub> and TLOPC<sub>60</sub>, respectively. (<b>B</b>) Schematic representation of bond critical points (blue), ring critical points (red), and cage critical points (green) in HLOPC<sub>60</sub> and TLOPC<sub>60</sub>, where (i–iii) are three different directions of HLOPC<sub>60</sub>; (iv–vi) are the three different directions of TLOPC<sub>60</sub>.</p> Full article ">Figure 7
<p>(<b>A</b>) Van der Waals potential of HLOPC<sub>60</sub> and TLOPC<sub>60</sub>. The He atom is the probe atom. The blue isosurface represents regions where the van der Waals potential is significantly negative, and the small green ball is the van der Waals potential minimum point. (<b>B</b>) Interlayer interactions between bilayer HLOPC<sub>60</sub> and TLOPC<sub>60</sub>.</p> Full article ">

17 pages, 51050 KiB

Open AccessArticle

Towards Environmentally Friendly Buildings: An Assessment of the Mechanical Properties of Soil Mixtures with Graphene

by Federico Iorio Esposito, Paola Gallo Stampino, Letizia Ceccarelli, Marco Caruso, Giovanni Dotelli and Sergio Sabbadini

C 2025, 11(1), 16; https://doi.org/10.3390/c11010016 - 19 Feb 2025

This study investigates the potential of graphene-based additives to improve the mechanical properties of compacted soil mixtures in rammed-earth construction, contributing to the development of environmentally friendly building materials. Two distinct soils were selected, combined with sand at optimized ratios, and treated with [...] Read more.

This study investigates the potential of graphene-based additives to improve the mechanical properties of compacted soil mixtures in rammed-earth construction, contributing to the development of environmentally friendly building materials. Two distinct soils were selected, combined with sand at optimized ratios, and treated with varying concentrations of a graphene liquid solution and a graphene-based paste (0.001, 0.005, 0.01, 0.05, and 0.1 wt.% relative to the soil-sand proportion). The effects of these additives were analyzed using the modified Proctor compaction and unconfined compressive strength (UCS) tests, focusing on parameters such as optimum water content (OWC), maximum dry density (MDD), maximum strength (q_u), and stiffness modulus (E). The results demonstrated that graphene’s influence on compaction behavior and mechanical performance depends strongly on the soil composition, with minimal variation between additive types. In finer soil mixtures, graphene disrupted particle packing, increased water demand, and reduced strength. In silt–sandy mixtures, graphene’s hydrophobicity and limited interaction with fines decreased water absorption and preserved density but likewise led to diminished strength. Conclusions from the experiments suggest a possible interaction between graphene, soil’s finer fraction, and potentially the swelling and non-swelling clay minerals, providing insights into the complex interplay between soil properties. Full article

(This article belongs to the Topic Application of Graphene-Based Materials, 2nd Edition)

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<p>Additive used: (<b>a</b>) GUP ADMIXTURE (GUP); (<b>b</b>) Graphene paste (GSL).</p> Full article ">Figure 2
<p>Experimental setup for Proctor compaction test. (<b>a</b>) Proctor machine; (<b>b</b>) The mold positioned on the machine; (<b>c</b>) The rammer compacting the soil inside the mold; (<b>d</b>) The sample is leveled inside the mold; (<b>e</b>) Extraction of the sample; (<b>f</b>) The final sample extracted from the mold.</p> Full article ">Figure 3
<p>Experimental setup for unconfined compressive strength (UCS) test. (<b>a</b>) TRITECH Load Frame for UCS test; (<b>b</b>) Sample during the test; (<b>c</b>) Sample after failure.</p> Full article ">Figure 4
<p>Samples preparation for unconfined compressive strength (UCS) test. (<b>a</b>) Proctor cylinder on hand-driven load frame; (<b>b</b>) Coring procedure; (<b>c</b>) UCS samples in the curing chamber.</p> Full article ">Figure 5
<p>Verified water content (%) of ABS Mix and GSL series with respect to the reference optimum water content (OWC) of the ABS Mix (7.10%). Two distinct portions of the sample were tested for water content. The name of the sample consists of the soil name, followed by the percentage and the abbreviation of the additive (e.g., ABS 0.005% GSL).</p> Full article ">Figure 6
<p>Proctor compaction test results for ABS mixtures. (<b>a</b>) ABS Mix; (<b>b</b>) ABS 0.001% GUP; (<b>c</b>) ABS 0.005% GUP; (<b>d</b>) ABS 0.01% GUP; (<b>e</b>) ABS 0.05% GUP; (<b>f</b>) ABS 0.1% GUP. The soil saturation curves (Sr) are reported, indicating different degrees of saturation from 0.5 to 1.</p> Full article ">Figure 7
<p>Proctor compaction test results for T2 mixtures. (<b>a</b>) T2 Mix; (<b>b</b>) T2 0.01% GUP; (<b>c</b>) T2 0.05% GUP; (<b>d</b>) T2 0.1% GUP. The soil saturation curves (Sr) are reported, indicating different degrees of saturation from 0.5 to 1.</p> Full article ">Figure 8
<p>Unconfined compressive strength (UCS) results. (<b>a</b>) ABS mixtures with GUP additive; (<b>b</b>) ABS mixtures with GSL additive; (<b>c</b>) T2 mixtures with GUP additive. The name of the sample consists of the soil name, followed by the percentage and the abbreviation of the additive (e.g., ABS 0.001% GUP).</p> Full article ">Figure 8 Cont.
<p>Unconfined compressive strength (UCS) results. (<b>a</b>) ABS mixtures with GUP additive; (<b>b</b>) ABS mixtures with GSL additive; (<b>c</b>) T2 mixtures with GUP additive. The name of the sample consists of the soil name, followed by the percentage and the abbreviation of the additive (e.g., ABS 0.001% GUP).</p> Full article ">Figure 9
<p>Results from the unconfined compressive strength (UCS) test. (<b>a</b>) Maximum stress, q<sub>u</sub>, with varying graphene concentration; (<b>b</b>) Stiffness modulus, E, with varying graphene concentration.</p> Full article ">Figure 9 Cont.
<p>Results from the unconfined compressive strength (UCS) test. (<b>a</b>) Maximum stress, q<sub>u</sub>, with varying graphene concentration; (<b>b</b>) Stiffness modulus, E, with varying graphene concentration.</p> Full article ">Figure 10
<p>Comparison between the two graphene-based additives of unconfined compressive strength results in ABS and T2. The name of the sample consists of the soil name, followed by the percentage and the abbreviation of the additive (e.g., ABS 0.001% GUP).</p> Full article ">

26 pages, 6250 KiB

Open AccessArticle

Activated Carbon Ammonization: Effects of the Chemical Composition of the Starting Material and the Treatment Temperature

by Silvia da C. Oliveira, Romulo C. Dutra, José J. L. León, Gesley A. V. Martins, Alysson M. A. Silva, Diana C. S. de Azevedo, Rafaelle G. Santiago, Daniel Ballesteros-Plata, Enrique Rodríguez-Castellón and Marcos J. Prauchner

C 2025, 11(1), 15; https://doi.org/10.3390/c11010015 - 19 Feb 2025

N-containing carbon-based materials have been employed with claimed improved performance as an adsorbent of acidic molecules, volatile organic compounds (VOC), and metallic ions; catalyst; electrocatalyst; and supercapacitor. In this context, the present work provides valuable insights into the preparation of N-doped activated carbons [...] Read more.

N-containing carbon-based materials have been employed with claimed improved performance as an adsorbent of acidic molecules, volatile organic compounds (VOC), and metallic ions; catalyst; electrocatalyst; and supercapacitor. In this context, the present work provides valuable insights into the preparation of N-doped activated carbons (ACs) by thermal treatment in NH₃ atmosphere (ammonization). A commercial AC was submitted to two kinds of pretreatment: (i) reflux with dilute HNO₃; (ii) thermal treatment up to 800 °C in inert atmosphere. The original and modified ACs were subjected to ammonization up to different temperatures. ACs with N content up to ~8% were achieved. Nevertheless, the amount and type of inserted nitrogen depended on ammonization temperature and surface composition of the starting material. Remarkably, oxygenated acidic groups on the surface of the starting material favored nitrogen insertion at low temperatures, with formation of mostly aliphatic (amines, imides, and lactams), pyridinic, and pyrrolic nitrogens. In turn, high temperatures provoked the decomposition of labile aliphatic functions. Therefore, the AC prepared from the sample pre-treated with HNO₃, which had the highest content of oxygenated acidic groups among the materials submitted to ammonization, presented the highest N content after ammonization up to 400 °C but the lowest content after ammonization up to 800 °C. Full article

(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)

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Full article ">Figure 1
<p>Usual oxygenated and nitrogenated functional groups present in ACs (elaborated considering references [<a href="#B14-carbon-11-00015" class="html-bibr">14</a>,<a href="#B15-carbon-11-00015" class="html-bibr">15</a>,<a href="#B16-carbon-11-00015" class="html-bibr">16</a>,<a href="#B17-carbon-11-00015" class="html-bibr">17</a>,<a href="#B18-carbon-11-00015" class="html-bibr">18</a>,<a href="#B19-carbon-11-00015" class="html-bibr">19</a>,<a href="#B20-carbon-11-00015" class="html-bibr">20</a>]).</p> Full article ">Figure 2
<p>Illustration of the effect provoked by the pair of lone electrons of nitrogen in N-containing carbon-based structures: (<b>a</b>) sp<sup>3</sup> N; (<b>b</b>) pyridinic N; (<b>c</b>) pyrrolic N; (<b>d</b>) quaternary N; (<b>e</b>) resonance in aromatic amines.</p> Full article ">Figure 3
<p>Scheme presenting the performed treatments and respective labels attributed to the obtained samples.</p> Full article ">Figure 4
<p>(<b>a</b>) N<sub>2</sub> adsorption–desorption isotherms and (<b>b</b>) corresponding PSD curves (closed and open symbols correspond to the adsorption and desorption branches, respectively).</p> Full article ">Figure 5
<p>HR-XPS C 1<span class="html-italic">s</span> and O 1<span class="html-italic">s</span> core level spectra.</p> Full article ">Figure 6
<p>TPD profiles of WV.</p> Full article ">Figure 7
<p>(<b>a</b>) CO<sub>2</sub> and (<b>b</b>) CO-TPD profiles of WV and respective deconvoluted peaks.</p> Full article ">Figure 8
<p>(<b>a</b>) CO<sub>2</sub> and (<b>b</b>) CO-TPD profiles.</p> Full article ">Figure 9
<p>HR-XPS N 1<span class="html-italic">s</span> core level spectrum for the AC modified by nitrification (WVAc).</p> Full article ">Figure 10
<p>HR-XPS N 1<span class="html-italic">s</span> core level spectra for the ammonized ACs.</p> Full article ">Figure 11
<p>CO<sub>2</sub>- (red lines) and CO-TPD (black lines) profiles of ammonized samples (the scale was kept the same in order to facilitate comparisons).</p> Full article ">Figure 11 Cont.
<p>CO<sub>2</sub>- (red lines) and CO-TPD (black lines) profiles of ammonized samples (the scale was kept the same in order to facilitate comparisons).</p> Full article ">Figure 12
<p>(<b>a</b>,<b>c</b>,<b>e</b>) N<sub>2</sub> adsorption–desorption isotherms of the ammonized samples and (<b>b</b>,<b>d</b>,<b>f</b>) the corresponding PSD curves (for the sake of comparison, the isotherms and PSD curves of the respective starting materials were included; closed and open symbols correspond to the adsorption and desorption branches, respectively).</p> Full article ">Figure 12 Cont.
<p>(<b>a</b>,<b>c</b>,<b>e</b>) N<sub>2</sub> adsorption–desorption isotherms of the ammonized samples and (<b>b</b>,<b>d</b>,<b>f</b>) the corresponding PSD curves (for the sake of comparison, the isotherms and PSD curves of the respective starting materials were included; closed and open symbols correspond to the adsorption and desorption branches, respectively).</p> Full article ">

13 pages, 7070 KiB

Open AccessArticle

Porous Polysulfone/Activated Carbon Capsules as Scaffolds for Enzyme Immobilization

by Magdalena Olkiewicz, Josep M. Montornes, Ricard Garcia-Valls, Iwona Gulaczyk and Bartosz Tylkowski

C 2025, 11(1), 14; https://doi.org/10.3390/c11010014 - 17 Feb 2025

Enzymes play a vital role in various industrial sectors and are essential components of many products. Hybrid enzyme-polymeric capsules were developed using polysulfone-activated carbon capsules as scaffolds. The polysulfone-activated carbon capsules with an average diameter of 2.55 mm were fabricated by applying a [...] Read more.

Enzymes play a vital role in various industrial sectors and are essential components of many products. Hybrid enzyme-polymeric capsules were developed using polysulfone-activated carbon capsules as scaffolds. The polysulfone-activated carbon capsules with an average diameter of 2.55 mm were fabricated by applying a phase inversion precipitation method. An increase in the amount of immobilized enzymes was observed with growth of activated carbon amount in polysulfone matrix. Enzyme immobilization was confirmed by the Bradford method, while Viscozyme^® L activity in carboxymethyl cellulose hydrolysis to glucose was measured by the Reducing Sugar DNS method. The recycling of the hybrid Viscozyme^® L-polysulfone/activated carbon capsules, and their reuse for subsequent cellulose hydrolysis was investigated and demonstrated repeatability of results. Full article

(This article belongs to the Special Issue Carbon-Based Polymer Composites: Synthesis, Processing, Characterization and Applications)

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<p>Optical micrographs of C1 and C5 capsules.</p> Full article ">Figure 2
<p>ESEM micrographs of surface morphologies of C1–C5 capsules.</p> Full article ">Figure 3
<p>ESEM micrographs of cross-section morphologies of C1–C5 capsules.</p> Full article ">Figure 4
<p>FT-IR spectra of pure polysulfone (PSF), activated carbon (Carbon), and capsules C1 (0% carbon) and C5 (20% carbon).</p> Full article ">Figure 5
<p>Enzyme Immobilization results.</p> Full article ">Figure 6
<p>ESEM micrographs of surface and cross-section morphologies of C5 capsule before and after enzyme immobilization.</p> Full article ">Figure 7
<p>Results of cellulose hydrolysis by pure and immobilized enzymes.</p> Full article ">Scheme 1
<p>A scheme of cellulose hydrolysis by enzyme.</p> Full article ">

9 pages, 3924 KiB

Open AccessEditor’s ChoiceArticle

Nanoparticle Air Filtration Using MXene-Coated Textiles

by Prastuti Upadhyay, Stefano Ippolito, Bita Soltan Mohammadlou, Michael S. Waring and Yury Gogotsi

C 2025, 11(1), 13; https://doi.org/10.3390/c11010013 - 12 Feb 2025

Nanoparticles with aerodynamic diameters of less than 100 nm pose serious problems to human health due to their small size and large surface area. Despite continuous progress in materials science to develop air remediation technologies, efficient nanoparticle filtration has appeared to be challenging. [...] Read more.

Nanoparticles with aerodynamic diameters of less than 100 nm pose serious problems to human health due to their small size and large surface area. Despite continuous progress in materials science to develop air remediation technologies, efficient nanoparticle filtration has appeared to be challenging. This study showcases the great promise of MXene-coated polyester textiles to efficiently filter nanoparticles, achieving a high efficiency of ~90% within the 15–30 nm range. Using alkaline earth metal ions to assist textile coating drastically improves the filter performance by ca. 25%, with the structure–property relationship thoroughly assessed by electron microscopy and X-ray computed tomography. Such techniques confirm metal ions’ crucial role in obtaining fully coated and impregnated textiles, which increases tortuosity and structural features that boost the ultimate filtration efficiency. Our work provides a novel perspective on using MXene textiles for nanoparticle filtration, presenting a viable alternative to produce high-performance air filters for real-world applications. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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<p>Schematic illustration for the production of (<b>a</b>) Ti<sub>3</sub>C<sub>2</sub>- and (<b>b</b>) Ti<sub>3</sub>C<sub>2</sub>/Mg(II)-coated textile air filters.</p> Full article ">Figure 2
<p>Scanning electron microscopy images of (<b>a</b>) uncoated textile, (<b>b</b>) Ti<sub>3</sub>C<sub>2</sub>-coated textile, (<b>c</b>) Ti<sub>3</sub>C<sub>2</sub>/Mg (II)-coated textile. (<b>d</b>) Elemental mappings collected on Ti<sub>3</sub>C<sub>2</sub>/Mg (II)-coated textile.</p> Full article ">Figure 3
<p>(<b>a</b>,<b>b</b>) Typical 2D cross-sectional Micro-CT images of Ti<sub>3</sub>C<sub>2</sub>-coated textile (MXene: gray; textile: fibrous lines). (<b>c</b>,<b>d</b>) Typical 2D cross-sectional Micro-CT images of Ti<sub>3</sub>C<sub>2</sub>/Mg(II)-coated textile (MXene/Mg(II): gray; textile: fibrous lines). (<b>e,f</b>) Three-dimensional Micro-CT images of Ti<sub>3</sub>C<sub>2</sub>-coated textile in unit space (gray). (<b>g,h</b>) Three-dimensional Micro-CT image of Ti<sub>3</sub>C<sub>2</sub>/Mg(II)-coated textile in unit space (green).</p> Full article ">Figure 4
<p>(<b>a</b>) A schematic of the filtration testing setup, where the samples are sandwiched between two red clamps inside a vacuum chamber (bottom). Then, this is filled with an aerosol of NaCl particles entering from the aerosol inlet (left), and data are collected by a particle analyzer (FMPS, right). (<b>b</b>) The filtration efficiency (<span class="html-italic">η</span>) of the NaCl aerosol for the uncoated textile and Ti<sub>3</sub>C<sub>2</sub>-and Ti<sub>3</sub>C<sub>2</sub>/Mg(II)-coated textile within a particle range from 5.6 nm to 560 nm.</p> Full article ">

13 pages, 2081 KiB

Open AccessEditor’s ChoiceCommunication

Diffusion-Improved Recrystallization of Ammonia Doping to Enhancing the Optoelectronic and Thermoelectric Effects of Multi-Junction Carbon Nanotube Paper Diodes

by Jih-Hsin Liu and Cheng-Jhe Yen

C 2025, 11(1), 12; https://doi.org/10.3390/c11010012 - 12 Feb 2025

This study focuses on fabricating flexible multi-junction diodes using carbon nanotubes (CNTs) as the base material, employing doping engineering and recrystallization-driven thermal diffusion techniques to enhance optoelectronic and thermoelectric properties. N-type CNTs are synthesized through ammonia doping and combined with intrinsic P-type CNTs [...] Read more.

This study focuses on fabricating flexible multi-junction diodes using carbon nanotubes (CNTs) as the base material, employing doping engineering and recrystallization-driven thermal diffusion techniques to enhance optoelectronic and thermoelectric properties. N-type CNTs are synthesized through ammonia doping and combined with intrinsic P-type CNTs to create PN multi-junction “buckypaper”. Post-diffusion processes improve junction crystallinity and doping gradients, significantly boosting the rectification ratio and optoelectronic and thermoelectric response. The device follows the superposition principle, achieving notable increases in thermoelectric and photovoltaic outputs, with the Seebeck coefficient rising from 5.7 μV/K to 24.4 μV/K. This study underscores the potential of flexible carbon-based devices for energy harvesting applications and advancing optoelectronic and thermoelectric systems. Full article

(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)

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Full article ">Figure 1
<p>(<b>a</b>) Flexible buckypaper fabricated from multi-walled carbon nanotubes (MWCNTs), along with (<b>b</b>) schematic illustrations of various junction stacking configurations and the corresponding (<b>c</b>) EDS analysis of buckypaper fabricated from MWCNTs pre-doped with 28% concentrated ammonia solution at 450 °C for one hour. (<b>d</b>) EDS analysis of the buckypaper subjected to a subsequent post-diffusion process at 600 °C for one hour.</p> Full article ">Figure 2
<p>(<b>a</b>) Raman spectrum of carbon nanotube powder pre-doped with 28% concentrated ammonia solution at 450 °C for one hour, and (<b>b</b>) Raman spectrum of the corresponding buckypaper (BP) after undergoing a post-diffusion process at 600 °C for one hour.</p> Full article ">Figure 3
<p>(<b>a</b>) Current–voltage (I-V) characteristics of single-junction and 15-junction diodes fabricated from ammonia-doped N-type CNT powder and intrinsic P-type CNT powder, measured before and after the post-diffusion process. (<b>b</b>) I-V characteristics of a single-junction diode in a series configuration after post-diffusion. (<b>c</b>) I-V characteristics of a 15-junction diode in a series configuration after post-diffusion. (<b>d</b>) Capacitance-voltage (C-V) characteristics of the single-junction diode after post-diffusion. (<b>e</b>) C-V characteristics of the 15-junction diode after post-diffusion.</p> Full article ">Figure 4
<p>(<b>a</b>) Thermoelectric voltage characteristics of single-junction and 15-junction diodes fabricated from ammonia-doped N-type CNT powder and intrinsic P-type CNT powder, measured both before and after the post-diffusion process, as well as their thermoelectric voltage responses in an electrical series configuration. (<b>b</b>) Thermoelectric voltage measurement system. (<b>c</b>) Photoelectric response of a single-junction diode in an electrical series configuration after post-diffusion. (<b>d</b>) Photovoltaic measurement system.</p> Full article ">

17 pages, 4446 KiB

Open AccessArticle

TiO₂/SWCNts: Linear and Nonlinear Optical Studies for Environmental Applications

by Saloua Helali

C 2025, 11(1), 11; https://doi.org/10.3390/c11010011 - 26 Jan 2025

A series of single-walled carbon nanotube/titanium dioxide (SWCNTs/TiO₂) composites were prepared by the incorporation of various concentrations (0, 5, 10, 20 V.%) of SWCNTs in TiO₂. The prepared solutions were successfully formed on silicon and quartz substrates using the [...] Read more.

A series of single-walled carbon nanotube/titanium dioxide (SWCNTs/TiO₂) composites were prepared by the incorporation of various concentrations (0, 5, 10, 20 V.%) of SWCNTs in TiO₂. The prepared solutions were successfully formed on silicon and quartz substrates using the sol–gel spin-coating approach at 600 °C in ambient air. The X-ray diffraction method was used to investigate the structure of the samples. The absorbance and transmittance data of the samples were measured using a UV–vis spectrophotometer. Through the analysis of these data, both the linear and nonlinear optical properties of the samples were examined. Wemple–DiDomenico’s single-oscillator model was used to calculate the single-oscillator energy and dispersion energy. Finally, all samples’ photocatalytic performance was studied by the photodegradation of methylene blue (MB) in an aqueous solution under UV irradiation. It is found that the photocatalytic efficiency increases when increasing the SWCNT content. This research offers a new perspective for the creation of new photocatalysts for environmental applications. Full article

(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)

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<p>Transmittance and reflectance spectra of TiO<sub>2</sub> and for SWCNTs/TiO<sub>2</sub> composites for different percentages, 5%, 10%, 20%, of SWCNTs.</p> Full article ">Figure 2
<p>The absorption coefficient, α, spectra of TiO<sub>2</sub> and for 5%, 10%, 20% SWCNTs/TiO<sub>2</sub> composites.</p> Full article ">Figure 3
<p>(αhν)<sup>1/2</sup> versus energy for (<b>a</b>) TiO<sub>2</sub>, (<b>b</b>) TiO<sub>2</sub>-(5%) SWCNTs, (<b>c</b>) TiO<sub>2</sub>-(10%) SWCNTs, and (<b>d</b>) TiO<sub>2</sub>-(20%) SWCNTs.</p> Full article ">Figure 4
<p>The spectra of refractive index versus wavelength for pure TiO<sub>2</sub> and TiO<sub>2</sub>-SWCNTs composites.</p> Full article ">Figure 5
<p>The (n<sup>2</sup> − 1)<sup>−1</sup> vs. (hν)<sup>2</sup> curve for pure TiO<sub>2</sub> and for 5%, 10%, 20% SWCNTs/TiO<sub>2</sub> composites.</p> Full article ">Figure 6
<p>The relation between n<sup>2</sup> as a function of λ<sup>2</sup> of TiO<sub>2</sub> and for 5%, 10%, 20% SWCNTsTiO<sub>2</sub>.</p> Full article ">Figure 7
<p>The variation in (<b>a</b>) real part, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>ε</mi> </mrow> <mrow> <mn>1</mn> </mrow> </msub> </mrow> </semantics></math>, (<b>b</b>) imaginary part, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>ε</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> </mrow> </semantics></math>, of dielectric constant as a function of photon energy for TiO<sub>2</sub> and for 5%, 10%, 20% SWCNTs-TiO<sub>2</sub> composites.</p> Full article ">Figure 8
<p>The spectra of (<b>a</b>) optical conductivity and (<b>b</b>) electrical conduction of TiO<sub>2</sub> and for 5%, 10%, 20% SWCNTs-TiO<sub>2</sub> composites.</p> Full article ">Figure 9
<p>The variation in χ<sup>(1)</sup>, χ<sup>(3)</sup>, and n<sub>2</sub> as a function of concentration of SWCNTs.</p> Full article ">Figure 10
<p>The XRD patterns of pure TiO<sub>2</sub> and 5%, 10%, 20% SWCNTs-TiO<sub>2</sub> composites.</p> Full article ">Figure 11
<p>UV–vis absorption spectra showing the photocatalytic activity of TiO<sub>2</sub> and SWCNTs/TiO<sub>2</sub> composites regarding photocatalytic degradation of MB in water.</p> Full article ">Figure 12
<p>The variation in photocatalytic efficiency of SWCNTs-TiO<sub>2</sub> composites.</p> Full article ">Figure 13
<p>Mechanism of photocatalytic activity of SWCNTs/TiO<sub>2</sub> composites towards degradation of MB dye.</p> Full article ">

14 pages, 7961 KiB

Open AccessEditor’s ChoiceArticle

Markedly Enhanced Photoluminescence of Carbon Dots Dispersed in Deuterium Oxide

by Corneliu S. Stan, Adina Coroaba, Conchi O. Ania, Cristina Albu and Marcel Popa

C 2025, 11(1), 10; https://doi.org/10.3390/c11010010 - 22 Jan 2025

In this work, we report some surprisingly interesting results in our pursuit to improve the photoluminescent emission of Carbon Dots (CDs) prepared from various precursors. By simply replacing the regular water with deuterium oxide (D₂O) as a dispersion medium, the emission [...] Read more.

In this work, we report some surprisingly interesting results in our pursuit to improve the photoluminescent emission of Carbon Dots (CDs) prepared from various precursors. By simply replacing the regular water with deuterium oxide (D₂O) as a dispersion medium, the emission intensity and the subsequent quantum efficiency of the radiative processes could be markedly enhanced. The present study was performed on our previous reported works related to CDs; in each case, the preparation path was maintained accordingly. For each type of CD, the emission intensity and the absolute photoluminescence quantum yield (PLQY) were highly improved, with, in certain cases, more-than-doubled values being recorded and the gain in performance being easily noticeable with the naked eye even in plain daylight. For each type of CD dispersed in regular water and heavy water, respectively, the photoluminescent properties were thoroughly investigated through Steady State, lifetime, and absolute PLQY. To further elucidate the mechanism involved in the photoluminescence intensity enhancement, samples of D₂O and H₂O dispersed CDs were embedded in a crosslinked Poly(acrylic acid) polymer matrix. The investigations revealed the major influence of the deuterium oxide dispersion medium over the PL emission properties of the investigated CDs. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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<p>PL emission of the NHF-CDs dispersed in (<b>a</b>) water, (<b>b</b>) deuterium oxide.</p> Full article ">Figure 2
<p>PL emission of the NHS-CDs dispersed in (<b>a</b>) water, (<b>b</b>) deuterium oxide.</p> Full article ">Figure 3
<p>PL emission of the AW-CDs dispersed in (<b>a</b>) water, (<b>b</b>) deuterium oxide.</p> Full article ">Figure 4
<p>PL emission of the Fe-CDs dispersed in (<b>a</b>) water, (<b>b</b>) deuterium oxide.</p> Full article ">Figure 5
<p>Observed PL emission intensity of the NHF-CDs/monomer/crosslinker/photoinitiator/D<sub>2</sub>O mixture (<b>a</b>) prior and (<b>b</b>) post-polymerization.</p> Full article ">Figure 6
<p>The typical time-resolved fluorescence decay profiles of the (<b>A</b>) NHF-CDs/H<sub>2</sub>O, (<b>B</b>) NHF-CDs D<sub>2</sub>O, (<b>C</b>) NHS-CDs/H<sub>2</sub>O, (<b>D</b>) NHS-CDs/D<sub>2</sub>O, (<b>E</b>) Fe-CDs/H<sub>2</sub>O, (<b>F</b>) Fe-CDs/D<sub>2</sub>O, (<b>G</b>) AW-CDs/H<sub>2</sub>O, and (<b>H</b>) AW-CDs/D<sub>2</sub>O samples.</p> Full article ">Figure 6 Cont.
<p>The typical time-resolved fluorescence decay profiles of the (<b>A</b>) NHF-CDs/H<sub>2</sub>O, (<b>B</b>) NHF-CDs D<sub>2</sub>O, (<b>C</b>) NHS-CDs/H<sub>2</sub>O, (<b>D</b>) NHS-CDs/D<sub>2</sub>O, (<b>E</b>) Fe-CDs/H<sub>2</sub>O, (<b>F</b>) Fe-CDs/D<sub>2</sub>O, (<b>G</b>) AW-CDs/H<sub>2</sub>O, and (<b>H</b>) AW-CDs/D<sub>2</sub>O samples.</p> Full article ">Figure 7
<p>Dimensional distribution of freshly prepared/1 week aged of (<b>a</b>) NHF-CDs, (<b>b</b>) NHS-CDs, (<b>c</b>) AW-CDs, and (<b>d</b>) Fe-CDs dispersed in D<sub>2</sub>O.</p> Full article ">

16 pages, 2648 KiB

Open AccessArticle

Raman Spectroscopy of Graphene/CNT Layers Deposited on Interdigit Sensors for Application in Gas Detection

by Stefan-Marian Iordache, Ana-Maria Iordache, Ana-Maria Florea (Raduta), Stefan Caramizoiu, Catalin Parvulescu, Flaviu Baiasu, Irina Negut and Bogdan Bita

C 2025, 11(1), 9; https://doi.org/10.3390/c11010009 - 20 Jan 2025

Graphene/CNT layers were deposited onto platinum electrodes of an interdigitated sensor using radio-frequency magnetron sputtering. The graphene/CNTs were synthesized in an Argon atmosphere at a pressure of (2 × 10⁻²–5 × 10⁻³) mbar, with the substrate maintained at 300 [...] Read more.

Graphene/CNT layers were deposited onto platinum electrodes of an interdigitated sensor using radio-frequency magnetron sputtering. The graphene/CNTs were synthesized in an Argon atmosphere at a pressure of (2 × 10⁻²–5 × 10⁻³) mbar, with the substrate maintained at 300 °C either through continuous heating with an electronically controlled heater or by applying a −200 V bias using a direct current power supply throughout the deposition process. The study compares the surface morphology, carbon atom arrangement within the layer volumes, and electrical properties of the films as influenced by the different methods of substrate heating. X-ray diffraction and Raman spectroscopy confirmed the formation of CNTs within the graphene matrix. Additionally, scanning electron microscopy revealed that the carbon nanotubes are aligned and organized into cluster-like structure. The graphene/CNT layers produced at higher pressures present exponential I–V characteristics that ascertain the semiconducting character of the layers and their suitability for applications in gas sensing. Full article

(This article belongs to the Special Issue New Advances in Graphene Synthesis and Applications)

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27 pages, 17276 KiB

Open AccessReview

PPE Waste-Derived Carbon Materials for Energy Storage Applications via Carbonization Techniques

by Nur Amaliyana Raship, Siti Nooraya Mohd Tawil and Murniati Syaripuddin

C 2025, 11(1), 8; https://doi.org/10.3390/c11010008 - 16 Jan 2025

Starting from the COVID-19 pandemic in early 2020, billions of personal protective equipment (PPE), mainly face masks (FMs), are reported to be worn and thrown away every month worldwide. Most of the waste winds up in landfills and undergoes an incineration process after [...] Read more.

Starting from the COVID-19 pandemic in early 2020, billions of personal protective equipment (PPE), mainly face masks (FMs), are reported to be worn and thrown away every month worldwide. Most of the waste winds up in landfills and undergoes an incineration process after being released into the environment. This could pose a significant risk and long-term effects to both human health and ecology due to the tremendous amount of non-biodegradable substances in the PPE waste. Consequently, alternative approaches for recycling PPE waste are imperatively needed to lessen the harmful effects of PPE waste. The current recycling methods facilitate the conventional treatment of waste, and most of it results in materials with decreased values for their characteristics. Thus, it is crucial to create efficient and environmentally friendly methods for recycling FMs and other PPE waste into products with added value, such as high-quality carbon materials. This paper reviews and focuses on the techniques for recycling PPE waste that are both economically viable and beneficial to the environment through carbonization technology, which transforms PPE waste into highly valuable carbon materials, as well as exploring the possible utilization of these materials for energy storage applications. In conclusion, this paper provides copious knowledge and information regarding PPE waste-derived carbon-based materials that would benefit potential green energy research. Full article

(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)

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Full article ">Figure 1
<p>Personal protective equipment (PPE) gear.</p> Full article ">Figure 2
<p>Flowchart of PPE waste conversion into carbon-based materials and their applications.</p> Full article ">Figure 3
<p>The health influence of FM waste and MP generation in the environment [<a href="#B14-carbon-11-00008" class="html-bibr">14</a>]. Copyright 2023, Elsevier.</p> Full article ">Figure 4
<p>Types of carbonization techniques.</p> Full article ">Figure 5
<p>(<b>a</b>) Procedure of carbonization synthesis combined with ball milling, (<b>b</b>) XRD spectra of amorphous graphitic carbon, SEM images of FM waste for (<b>c</b>) 10 h carbonization time, (<b>d</b>) 10 h carbonization time with heat treatment, and (<b>e</b>) The derived structure of the PP fiber of FM waste into carbon tube [<a href="#B26-carbon-11-00008" class="html-bibr">26</a>]. Copyright 2023, Elsevier.</p> Full article ">Figure 6
<p>(<b>a</b>) Carbonization process of FM waste-derived hard carbon fabrics, (<b>b</b>–<b>d</b>) SEM images of hard carbon fabrics at 1300 °C carbonization temperature with different magnifications, TEM images of hard carbon fabrics at different carbonization temperatures: (<b>e</b>) 1200 °C, (<b>f</b>) 1300 °C, and (<b>g</b>) 1400 °C (the insets and yellow frames are the corresponding SAED) [<a href="#B36-carbon-11-00008" class="html-bibr">36</a>]. Copyright 2023, Elsevier.</p> Full article ">Figure 7
<p>(<b>a</b>) Carbonization process of FM waste-derived carbon nanoparticles, (<b>b</b>) FESEM image, (<b>c</b>) EDS spectra and mapping, (<b>d</b>) FTIR spectra, and (<b>e</b>) XPS spectra of the synthesized carbon [<a href="#B9-carbon-11-00008" class="html-bibr">9</a>].</p> Full article ">Figure 8
<p>(<b>a</b>) Fabrication process of CNT/Ni hybrids using catalytic carbonization, SEM images of CNT/Ni hybrids (<b>b</b>,<b>c</b>) WM/10Ni(OH)<sub>2</sub>/NiCl<sub>2</sub>, (<b>d</b>) WM/20Ni(OH)<sub>2</sub>/NiCl<sub>2</sub>, and (<b>e</b>) WM/50Ni(OH)<sub>2</sub>/NiCl<sub>2</sub>; TEM images of CNT/Ni hybrids from (<b>f</b>) WM/20Ni(OH)<sub>2</sub>/NiCl<sub>2</sub>, (<b>g</b>) WM/50Ni(OH)<sub>2</sub>/NiCl<sub>2</sub>, (<b>h</b>) XRD spectra of CNT/Ni hybrids, and (<b>i</b>) Raman spectra of CNT/Ni hybrids [<a href="#B29-carbon-11-00008" class="html-bibr">29</a>]. Copyright 2021, Elsevier.</p> Full article ">Figure 9
<p>(<b>a</b>) Synthesis process of porous carbon by microwave carbonization technique, (<b>b</b>) XRD, (<b>c</b>) Raman spectra, and (<b>d</b>) pore width of synthesized porous carbon [<a href="#B39-carbon-11-00008" class="html-bibr">39</a>]. Copyright 2022, Elsevier.</p> Full article ">Figure 10
<p>Hydrothermal carbonization technique for synthesizing porous carbon.</p> Full article ">Figure 11
<p>Cyclic voltammetry of porous carbon as cathode electrode (<b>a</b>) P-SO@DMMs-6/S, (<b>b</b>) P-SO@DMMs-8/S, (<b>c</b>) P-SO@DMMs-10/S, (<b>d</b>) rate performance test of P-SO@DMMs/S cathodes, and (<b>e</b>) cycling capacity of P- SO@DMMs/S cathodes [<a href="#B39-carbon-11-00008" class="html-bibr">39</a>]. Copyright 2022, Elsevier.</p> Full article ">Figure 12
<p>(<b>a</b>) Synthesis of hard carbon from FM waste for anodes in Na-ion batteries, (<b>b</b>) cycle profiles, (<b>c</b>) rate capabilities ranging from 0.01 to 0.5 A/g, (<b>d</b>) Ragone plots, and (<b>e</b>) cycling performance [<a href="#B50-carbon-11-00008" class="html-bibr">50</a>]. Copyright 2022, Elsevier.</p> Full article ">Figure 13
<p>(<b>a</b>) Illustration of asymmetric capacitor (<b>b</b>) GCD, (<b>c</b>) EIS, (<b>d</b>) cyclic stability of the carbon thin film electrode, (<b>e</b>) GCD tests performed at 1.3 to 40 A g<sup>−1</sup>, (<b>f</b>) rate performance, (<b>g</b>) cyclic stability, (<b>h</b>) EIS study of the device, (<b>i</b>) specific capacitance vs. energy density, and (<b>j</b>) Ragone’s plot of the supercapacitor device [<a href="#B9-carbon-11-00008" class="html-bibr">9</a>].</p> Full article ">Figure 14
<p>(<b>a</b>) Specific capacitances of the DSM-C and NiO/DSM-C electrodes, (<b>b</b>) specific capacitances of NiO/DSM-C//DSM-C ASCs, and (<b>c</b>) cycling stability at 2 A g<sup>−1</sup> [<a href="#B34-carbon-11-00008" class="html-bibr">34</a>]. Copyright 2021, Elsevier.</p> Full article ">

15 pages, 766 KiB

Open AccessArticle

Monte Carlo Simulation of Aromatic Molecule Adsorption on Multi-Walled Carbon Nanotube Surfaces Using Coefficient of Conformism of a Correlative Prediction (CCCP)

by Alla P. Toropova, Andrey A. Toropov, Alessandra Roncaglioni and Emilio Benfenati

C 2025, 11(1), 7; https://doi.org/10.3390/c11010007 - 14 Jan 2025

Using the Monte Carlo technique via CORAL-2024 software, models of aromatic substance adsorption on multi-walled nanotubes were constructed. Possible mechanistic interpretations of such models and the corresponding applicability domains were investigated. In constructing the models, criteria of the predictive potential such as the [...] Read more.

Using the Monte Carlo technique via CORAL-2024 software, models of aromatic substance adsorption on multi-walled nanotubes were constructed. Possible mechanistic interpretations of such models and the corresponding applicability domains were investigated. In constructing the models, criteria of the predictive potential such as the iIndex of Ideality of Correlation (IIC), the Correlation Intensity Index (CII), and the Coefficient of Conformism of a Correlative Prediction (CCCP) were used. It was assumed that the CCCP could serve as a tool for increasing the predictive potential of adsorption models of organic substances on the surface of nanotubes. The developed models provided good predictive potential. The perspectives on the improvement of the nano-QSPR/QSAR were discussed. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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17 pages, 3233 KiB

Open AccessReview

Fluorination to Enhance the Tribological Properties of Carbonaceous Materials

by Guillaume Haddad, Nadiège Nomède-Martyr, Philippe Bilas, Katia Guérin, Philippe Thomas, Karl Delbé and Marc Dubois

C 2025, 11(1), 6; https://doi.org/10.3390/c11010006 - 7 Jan 2025

This review compiles data from 77 articles on the tribological properties of fluorinated carbons CFx. Covalent grafting of fluorine atoms improves the tribological properties. The C-F bonding plays a key role in reducing friction. The tribological stability of CFx, along with their ability [...] Read more.

This review compiles data from 77 articles on the tribological properties of fluorinated carbons CFx. Covalent grafting of fluorine atoms improves the tribological properties. The C-F bonding plays a key role in reducing friction. The tribological stability of CFx, along with their ability to form protective films from the very first cycles, provides a significant advantage in reducing wear and extending the lifespan of mechanical components. The role of the presence of fluorine atoms, their content, their distribution in the carbon lattice, and the C-F bonding, as well as the dimensionality and the size of the materials, are discussed. Some ways of improving lubrication performance and investigating friction-reducing properties and mechanisms are proposed. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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<p>Our strategies to improve the tribological properties of fluorinated (nano)carbons.</p> Full article ">Figure 2
<p>Ball-on-plane reciprocal tribometer (<b>a</b>) and representative examples of the evolution of the friction coefficient according to the presence of a volatile solvent (<b>b</b>), aspect of the wear scar obtained at 100 cycles of friction (<b>c</b>), and evolution of the Raman spectra during friction (<b>d</b>).</p> Full article ">Figure 3
<p>Friction coefficients of GCBs and Carbon Nanofibers.</p> Full article ">Figure 4
<p>Correlation between the thickness of the fluorinated shell (obtained from TEM; a representative example is given on the left side) and friction coefficient according to the fluorination method, either with molecular fluorine (direct) or atomic fluorine (controlled). Arrows show the region of interest or magnification.</p> Full article ">Figure 5
<p>Friction coefficients of FGCBs (0D), FCNFs (1D), and fluorinated nanodiscs (2D), based on the fluorination rate [<a href="#B44-carbon-11-00006" class="html-bibr">44</a>].</p> Full article ">Figure 6
<p>Evolution of the intrinsic friction coefficient according to the post-fluorination temperature (case of RTFs prepared with the presence of BF<sub>3</sub> and ClF<sub>3</sub> catalysts [<a href="#B17-carbon-11-00006" class="html-bibr">17</a>].</p> Full article ">Figure 7
<p>Evolution of the coefficient of friction with cycle number for raw and thermally exfoliated graphite fluoride [<a href="#B19-carbon-11-00006" class="html-bibr">19</a>].</p> Full article ">Figure 8
<p>Friction coefficients recorded at three cycles for pristine and fluorinated GCBs and CNFs (F/C = 0.9 for both FGCBs and FCNFs).</p> Full article ">Figure 9
<p>(<b>a</b>) Figure AFM topographic image of fiber cut by FIB, (<b>b</b>) topographic profile correlated to the friction coefficient evolution as a function of sliding distance.</p> Full article ">Figure 10
<p>Dispersion of fluorinated nanofibers (CF<sub>0.85</sub>) in organic solvents. Friction coefficient values obtained for mixtures containing fluorinated carbon nanofibers.</p> Full article ">

20 pages, 3964 KiB

Open AccessArticle

Degradation Kinetics, Mechanisms, and Antioxidant Activity of PCL-Based Scaffolds with In Situ Grown Nanohydroxyapatite on Graphene Oxide Nanoscrolls

by Lillian Tsitsi Mambiri and Dilip Depan

C 2025, 11(1), 5; https://doi.org/10.3390/c11010005 - 3 Jan 2025

Polycaprolactone (PCL) degradation is critical in bone tissue engineering, where scaffold degradation must align with tissue regeneration to ensure stability and integration. This study explores the effects of nanofillers, hydroxyapatite (nHA), and graphene oxide nanoscrolls (GONS) on PCL-based scaffold degradation kinetics. Both PHAP [...] Read more.

Polycaprolactone (PCL) degradation is critical in bone tissue engineering, where scaffold degradation must align with tissue regeneration to ensure stability and integration. This study explores the effects of nanofillers, hydroxyapatite (nHA), and graphene oxide nanoscrolls (GONS) on PCL-based scaffold degradation kinetics. Both PHAP (nHA-PCL) and PGAP (nHA-GONS-PCL) scaffolds exhibited changes to relaxation-driven degradation, as indicated by adherence to the Korsmeyer–Peppas model (R² = 1.00). PHAP scaffolds showed lower activation energies (5.02–5.54 kJ/mol), promoting faster chain relaxation and degradation in amorphous regions. PGAP scaffolds, with higher activation energies (12.88–12.90 kJ/mol), displayed greater resistance to chain relaxation and slower degradation. Differential scanning calorimetry (DSC) revealed that both nanofillers disrupted the crystalline regions, shifting degradation behavior from diffusion-based to relaxation-driven mechanisms in the amorphous zones, which was also reflected by changes in crystallization temperature (Tc) and melting temperature (T_m). Additionally, PGAP scaffolds demonstrated antioxidant potential, which decreased over time as degradation progressed. These results provide a mechanistic understanding of how nanofiller-modulated degradation dynamics can be strategically leveraged to optimize scaffold performance, facilitating precise control over degradation rates and bioactivity. Full article

(This article belongs to the Special Issue Carbon-Based Polymer Composites: Synthesis, Processing, Characterization and Applications)

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Full article ">Figure 1
<p>Weight loss (%) of PPCL, PHAP, and PGAP scaffolds during enzymatic degradation over 35 days.</p> Full article ">Figure 2
<p>(<b>a</b>) Melting temperature (<span class="html-italic">T<sub>m</sub></span>) and (<b>b</b>) crystallization temperature (<span class="html-italic">T<sub>c</sub></span>) of PPCL, PHAP, and PGAP scaffolds at day 0, day 14, and day 21.</p> Full article ">Figure 3
<p>Ester index (A<sub>1725</sub>/A<sub>1162</sub>) of PPCL, PHAP, and PGAP scaffolds during enzymatic degradation over 21 days.</p> Full article ">Figure 4
<p>Activation energy required for the degradation of PPCL, PHAP5, PHAP10, PHAP20, PGAP5, PGAP10, and PGAP20 scaffolds.</p> Full article ">Figure 5
<p>Radical scavenging activity (%) of PGAP scaffolds (PGAP5, PGAP10, PGAP20) on day 0, day 14, and day 21.</p> Full article ">Scheme 1
<p>Mechanism for diffusion-driven chain relaxation.</p> Full article ">Scheme 2
<p>Water plasticizing effect on polymer chains.</p> Full article ">Scheme 3
<p>Mechanisms of hydrolytic and enzymatic degradation of ester bonds in PCL. Surface degradation is influenced by the highly amorphous structure and increased exposure to water, while bulk degradation is constrained by crystalline regions with less water accessibility.</p> Full article ">Scheme 4
<p>Enzyme adsorption resulting in reduced RSA.</p> Full article ">

14 pages, 3865 KiB

Open AccessArticle

Adsorption of Asymmetric and Linear Hazardous Gases on Graphene Oxides: Density Functional Study

by Yongju Kwon, Taeyang Kim, Jaemyeong Choi, Sangeon Lee, Sungmin Cha and Soonchul Kwon

C 2025, 11(1), 4; https://doi.org/10.3390/c11010004 - 2 Jan 2025

The introduction of functional groups, such as graphene oxide, can improve the reactivity between molecules, increasing the potential for their use in many fields such as gas sensing and adsorption. It was reported that that graphene materials are actively utilized in toxic gas [...] Read more.

The introduction of functional groups, such as graphene oxide, can improve the reactivity between molecules, increasing the potential for their use in many fields such as gas sensing and adsorption. It was reported that that graphene materials are actively utilized in toxic gas sensor materials by modifying the surface with their chemical and structural stability. In order to understand the mechanisms of graphene and graphene oxides for adsorbing the hazardous gases, we classified the four gases (H₂S, NH₃, HF and COS) with their phases (two asymmetric and two linear), and conducted density functional theory calculations to determine the adsorption affinity, which represents the binding energy, bond distance, energy charge (Mulliken and Hirshfeld methods) and band gap between the HOMO (Highest Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied Molecular Orbital). The results showed that introducing a functional group enhanced the binding energy with a narrowed band gap in asymmetric gas adsorption (H₂S and NH₃), while the results of the linear gases (HF and COS) showed lowered binding energy with a narrowed band gap. It is judged that the oxygen functional groups can narrow the band gap by introducing localized states between the valence and conduction bands or by forming new hybrid states through interactions with all the gases. However, from the differences in the phases, the linear gases stably interacted with a defect-free, porous and flat structure like with π–π interactions. In short, the theoretical findings confirm that the oxidation functional groups narrowed the band gap with a local interaction; however, linear gases showed enhanced binding energies with pristine graphene, which highlights the importance of surface material selection dependent on the target gases. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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Full article ">Figure 1
<p>The geometry-optimized structure of Graphene. (Unit cell of the 2 × 2 supercell structure of graphene and surface of the 2 × 2 supercell (12.230 Å × 12.230 Å). The supercell of graphene is included for calculating convenience. The lattice vectors (a, b and c) were re-defined, to describe the surface area. The height required to keep the thickness of the vacuum space fixed to 20.000 Å for all calculations, was determined to be 30.000 Å.</p> Full article ">Figure 2
<p>The geometry-optimized structure of Graphene oxide functionalized on pristine graphene (<a href="#carbon-11-00004-f001" class="html-fig">Figure 1</a>). Graphene oxide with (<b>a</b>) epoxy group and (<b>b</b>) hydroxyl group.</p> Full article ">Figure 3
<p>The geometry-optimized structure of pollutants.</p> Full article ">Figure 4
<p>Adsorptive configuration of H<sub>2</sub>S on (<b>a</b>) graphene, (<b>b</b>) graphene oxide with epoxy group (GRO) and (<b>c</b>) graphene oxide with hydroxyl group (GROH).</p> Full article ">Figure 5
<p>Adsorptive configuration of NH<sub>3</sub> on (<b>a</b>) graphene, (<b>b</b>) graphene oxide with epoxy group (GRO) and (<b>c</b>) graphene oxide with hydroxyl group (GROH).</p> Full article ">Figure 6
<p>Adsorptive configuration of HF on (<b>a</b>) graphene, (<b>b</b>) graphene oxide with epoxy group (GRO) and (<b>c</b>) graphene oxide with hydroxyl group (GROH).</p> Full article ">Figure 7
<p>Adsorptive configuration of COS on (<b>a</b>) graphene, (<b>b</b>) graphene oxide with epoxy group (GRO) and (<b>c</b>) graphene oxide with hydroxyl group (GROH).</p> Full article ">

24 pages, 7558 KiB

Open AccessReview

Graphene-Enhanced Piezoelectric Nanogenerators for Efficient Energy Harvesting

by Joydip Sengupta and Chaudhery Mustansar Hussain

C 2025, 11(1), 3; https://doi.org/10.3390/c11010003 - 1 Jan 2025

Graphene-based piezoelectric nanogenerators (PENGs) have emerged as a promising technology for sustainable energy harvesting, offering significant potential in powering next-generation electronic devices. This review explores the integration of graphene, a highly conductive and mechanically robust two-dimensional (2D) material, with PENG to enhance their [...] Read more.

Graphene-based piezoelectric nanogenerators (PENGs) have emerged as a promising technology for sustainable energy harvesting, offering significant potential in powering next-generation electronic devices. This review explores the integration of graphene, a highly conductive and mechanically robust two-dimensional (2D) material, with PENG to enhance their energy conversion efficiency. Graphene’s unique properties, including its exceptional electron mobility, high mechanical strength, and flexibility, allow for the development of nanogenerators with superior performance compared to conventional PENGs. When combined with piezoelectric materials, polymers, graphene serves as both an active layer and a charge transport medium, boosting the piezoelectric response and output power. The graphene-based PENGs can harvest mechanical energy from various sources, including vibrations, human motion, and ambient environmental forces, making them ideal for applications in wearable electronics, and low-power devices. This paper provides an overview of the fabrication techniques, material properties, and energy conversion mechanisms of graphene-based PENGs, and integration into real-world applications. The findings demonstrate that the incorporation of graphene enhances the performance of PENG, paving the way for future innovations in energy-harvesting technologies. Full article

(This article belongs to the Special Issue New Advances in Graphene Synthesis and Applications)

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Graphical abstract
Full article ">Figure 1
<p>Graphene and its derivatives (reproduced with permission from [<a href="#B13-carbon-11-00003" class="html-bibr">13</a>]).</p> Full article ">Figure 2
<p>Different methods of graphene synthesis (reproduced with permission from [<a href="#B26-carbon-11-00003" class="html-bibr">26</a>]).</p> Full article ">Figure 3
<p>Diagrammatic representations of energy harvesters utilizing (<b>a</b>) the piezoelectric effect, (<b>b</b>) the triboelectric effect, (<b>c</b>) the thermoelectric effect, and (<b>d</b>) the pyroelectric effect (reproduced with permission from [<a href="#B46-carbon-11-00003" class="html-bibr">46</a>]).</p> Full article ">Figure 4
<p>Schematic diagram and operating mechanism of tri-layer piezoelectric nanogenerator (reproduced with permission from [<a href="#B91-carbon-11-00003" class="html-bibr">91</a>]).</p> Full article ">Figure 5
<p>(Clockwise from top left) The original photo of the flexible transparent ZnSi<sub>2</sub>O<sub>4</sub>–graphene–piezoelectric nanogenerator device, schematic of the tetragonal crystal structure of Zn<sub>2</sub>SiO<sub>4</sub> nanorods, SEM image of as-grown Zn<sub>2</sub>SiO<sub>4</sub>, piezoelectric output voltage generated from the transparent and flexible nanogenerator under various pressures under forward connection, schematic diagram of the graphene–ZnSi<sub>2</sub>O<sub>4</sub> piezoelectric device (reproduced with permission from [<a href="#B92-carbon-11-00003" class="html-bibr">92</a>]).</p> Full article ">Figure 6
<p>Voltage output generated from (<b>a</b>) finger tapping, (<b>b</b>) finger bending, (<b>c</b>) heel stepping, (<b>d</b>) toe stepping, and (<b>e</b>) knee bending is illustrated, with the inset depicting each motion during energy harvesting. (<b>f</b>) The durability and stability of the piezoelectric nanogenerator (PENG) were evaluated at a frequency of 5 Hz and a strain of 6 N after 1000 and 5000 cycles, followed by an additional two weeks of testing. (<b>g</b>) A full-bridge rectifier circuit was implemented to illuminate the LEDs, as shown in the accompanying photo displaying the circuit connections and the LEDs powered by the PENG. (<b>h</b>) The charging behavior of the 2.2 μF capacitor is also presented (reproduced with permission from [<a href="#B93-carbon-11-00003" class="html-bibr">93</a>]).</p> Full article ">Figure 7
<p>(<b>a</b>) The schematic of the nanogenerator fabrication process. (<b>i</b>) The pristine PU sponge. (<b>ii</b>) The PU sponge coated with GO on both internal and external surfaces. (<b>iii</b>) GO reduced using L-AA to form RGO, with a bottom electrode affixed. (<b>iv</b>) Growth of ZnO nanowires on the RGO surface. (<b>v</b>) A thin sputtered Au layer is applied on top of the sample, along with an attachment of the top electrode. (<b>vi</b>) PDMS is infused within the pores of the nanogenerator structure. Insets in <a href="#carbon-11-00003-f007" class="html-fig">Figure 7</a> depict the microstructure at each stage. (<b>b</b>) A photograph of the fully assembled nanogenerator (reproduced with permission from [<a href="#B94-carbon-11-00003" class="html-bibr">94</a>]).</p> Full article ">Figure 8
<p>Sensing features of the device include (<b>a</b>) finger tapping, (<b>b</b>) walking and jogging, (<b>c</b>) finger bending, and (<b>d</b>) LED activation (reproduced with permission from [<a href="#B96-carbon-11-00003" class="html-bibr">96</a>]).</p> Full article ">Figure 9
<p>(<b>a</b>) Piezoelectric output voltage, (<b>b</b>) output current from the GQDs/PVDF-HFP composite device under vertical compressive force in forward connection, (<b>c</b>) piezoelectric output voltage response during hand/wrist movements, and (<b>d</b>) output voltage generated under breathing conditions (reproduced with permission from [<a href="#B97-carbon-11-00003" class="html-bibr">97</a>]).</p> Full article ">Scheme 1
<p>A schematic representation illustrating the potential of graphene in nanogenerator (NG) fabrication.</p> Full article ">

25 pages, 8926 KiB

Open AccessArticle

Development and Characterization of Biomass-Derived Carbons for the Removal of Cu²⁺ and Pb²⁺ from Aqueous Solutions

by Vahid Rahimi, Catarina Helena Pimentel, Diego Gómez-Díaz, María Sonia Freire, Massimo Lazzari and Julia González-Álvarez

C 2025, 11(1), 2; https://doi.org/10.3390/c11010002 - 29 Dec 2024

This research explores the synthesis and application of carbon-based adsorbents derived from olive stones and almond shells as low-cost biomass precursors through carbonization at 600 °C combined with chemical activation using KOH, H₃PO₄, and ZnCl₂ with carbon/activating agent [...] Read more.

This research explores the synthesis and application of carbon-based adsorbents derived from olive stones and almond shells as low-cost biomass precursors through carbonization at 600 °C combined with chemical activation using KOH, H₃PO₄, and ZnCl₂ with carbon/activating agent (C/A) ratios of 1:2 and 1:4 (w/w) at 850 °C for the removal of Cu²⁺ and Pb²⁺ ions from aqueous solutions. The carbons produced were characterized using different techniques including SEM-EDX, FTIR, XRD, BET analysis, CHNS elemental analysis, and point of zero charge determination. Batch-mode adsorption experiments were carried out at adsorbent doses of 2 and 5 g L⁻¹, initial metal concentrations of 100 and 500 mg L⁻¹, and natural pH (around 5) with agitation at 350 rpm and 25 °C for 24 h. KOH-activated carbons, especially at a 1:4 (w/w) ratio, exhibited superior adsorption performance mainly due to their favorable surface characteristics and functionalities. Pb²⁺ was entirely removed (100%) at the highest initial concentration of 500 mg L⁻¹ and an adsorbent dosage of 5 g L⁻¹, while for Cu²⁺, the maximum adsorption efficiency was 86.29% at an initial concentration of 100 mg L⁻¹ and a dosage of 2 g L⁻¹. The results of this study will help advance knowledge in the design and optimization of adsorption processes for heavy metal removal, benefiting industries seeking green technologies to mitigate environmental pollution. Full article

(This article belongs to the Special Issue Carbon-Based Materials Applied in Water and Wastewater Treatment)

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Figure 1

Figure 1
<p>Schematic representation of the adsorption process for the removal of Cu<sup>2+</sup> and Pb<sup>2+</sup> ions.</p> Full article ">Figure 2
<p>SEM images of carbons produced from olive stones. (<b>A</b>) OSC; (<b>B</b>) OSACK1; (<b>C</b>) OSACK2; (<b>D</b>) OSACP1; (<b>E</b>) OSACP2; (<b>F</b>) OSACZ1; (<b>G</b>) OSACZ2. The white, red, and blue marks are indicative of distinct characteristics, namely a porous texture, uniform structural formations, and the presence of primary pores, respectively.</p> Full article ">Figure 3
<p>SEM images of carbons produced from almond shells. (<b>A</b>) ASC; (<b>B</b>) ASACK1; (<b>C</b>) ASACK2; (<b>D</b>) ASACP1; (<b>E</b>) ASACP2; (<b>F</b>) ASACZ1; (<b>G</b>) ASACZ2. The white, red, and blue marks are indicative of distinct characteristics, namely a porous texture, uniform structural formations, and the presence of primary pores, respectively.</p> Full article ">Figure 4
<p>N<sub>2</sub> adsorption–desorption isotherms at −196.15 °C for carbons produced from biomass precursors. (<b>A</b>,<b>C</b>) almond shell-based carbons; (<b>B</b>,<b>D</b>) olive stone-based carbons.</p> Full article ">Figure 5
<p>CO<sub>2</sub> adsorption isotherms at 0 °C. (<b>A</b>) olive stone-based carbons; (<b>B</b>) almond shell-based carbons.</p> Full article ">Figure 6
<p>XRD patterns of carbons produced from biomass precursors. (<b>A</b>) Non-activated carbons; (<b>B</b>) KOH-activated carbons; (<b>C</b>) H<sub>3</sub>PO<sub>4</sub>-activated carbons; (<b>D</b>) ZnCl<sub>2</sub>-activated carbons.</p> Full article ">Figure 7
<p>FTIR spectra of carbons produced from biomass precursors. (<b>A</b>) Non-activated carbons; (<b>B</b>) KOH-activated carbons; (<b>C</b>) H<sub>3</sub>PO<sub>4</sub>-activated carbons; (<b>D</b>) ZnCl<sub>2</sub>-activated carbons.</p> Full article ">Figure 8
<p>Main adsorption mechanisms of carbon adsorbents for the removal of Cu<sup>2+</sup> and Pb<sup>2+</sup> ions.</p> Full article ">Figure 9
<p>Effect of mesopore volume upon adsorption efficiency (initial metal concentration of 500 mg L<sup>−1</sup> and adsorbent dose of 2 g L<sup>−1</sup>).</p> Full article ">

28 pages, 2500 KiB

Open AccessReview

The Advanced Role of Carbon Quantum Dots in Nano-Food Science: Applications, Bibliographic Analysis, Safety Concerns, and Perspectives

by Abdul Majid, Khurshid Ahmad, Liju Tan, Waqas Niaz, Wang Na, Li Huiru and Jiangtao Wang

C 2025, 11(1), 1; https://doi.org/10.3390/c11010001 - 24 Dec 2024

Cited by 1

Carbon quantum dots (CQDs) are innovative carbon-based nanomaterials that can be synthesized from organic and inorganic sources using two approaches: “top-down” (laser ablation, arc discharge, electrochemical, and acidic oxidation) and “bottom-up” (hydrothermal, ultrasound-assisted, microwave, and thermal decomposition). Among these, hydrothermal synthesis stands out [...] Read more.

Carbon quantum dots (CQDs) are innovative carbon-based nanomaterials that can be synthesized from organic and inorganic sources using two approaches: “top-down” (laser ablation, arc discharge, electrochemical, and acidic oxidation) and “bottom-up” (hydrothermal, ultrasound-assisted, microwave, and thermal decomposition). Among these, hydrothermal synthesis stands out as the best option as it is affordable and eco-friendly and can produce a high quantum yield. Due to their exceptional physical and chemical properties, CQDs are highly promising materials for diverse applications, i.e., medicine, bioimaging, and especially in food safety, which is one of the thriving fields of recent research worldwide. As an innovative sensing tool, CQDs with different surface functional groups enable them to detect food contaminants, i.e., food additives in processed food, drug residues in honey, and mycotoxins in beer and flour, based on different sensing mechanisms (IFE, PET, and FRET). This article discussed the sources, fabrication methods, advantages, and limitations of CQDs as a sensing for the detection of food contaminants. In addition, the cost-effectiveness, eco-friendliness, high quantum yield, safety concerns, and future research perspectives to enhance food quality and security were briefly highlighted. This review also explored recent advancements in CQD applications in food safety, supported by a bibliometric analysis (2014–2024) using the PubMed database. Full article

(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)

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Full article ">Figure 1
<p>Two basic approaches for CQD synthesis are the bottom-up method and the top-down method.</p> Full article ">Figure 2
<p>Summarized general sensing mechanism of CQDs in food applications.</p> Full article ">Figure 3
<p>(<b>a</b>) Illustration of five distinct food additives shown with their fluorescence sensing strategies using the LDA approach. Reproduced from [<a href="#B113-carbon-11-00001" class="html-bibr">113</a>] ©Elsevier Science Direct. (<b>b</b>) Illustration of detection of tetracycline (TC) procedure in honey. The HMIP@CD was first dispersed in a sample of diluted honey. After adsorption, the composite was separated by centrifugation and was dispersed in (PBS) followed by fluorescence detection. Reproduced from [<a href="#B120-carbon-11-00001" class="html-bibr">120</a>] ©Elsevier Science Direct. (<b>c</b>) Schematic illustration of CDs for Cr<sub>2</sub>O<sub>7</sub><sup>2−</sup> ions detection by fluorescence quenching through inner filter effect (IFE). Reproduced from [<a href="#B121-carbon-11-00001" class="html-bibr">121</a>] ©Elsevier Science Direct. (<b>d</b>) FRET-based fluorescence detection of ochratoxin A (OTA) in flour and beer. The absorbance spectra of Apt-AgNPs correlated with the cDNA-CD emission spectrum, promoting the FRET between AgNPs and CD and causing the energy transfer to cause the CD’s fluorescence signals to vanish. Reproduced from [<a href="#B122-carbon-11-00001" class="html-bibr">122</a>] ©Elsevier Science Direct.</p> Full article ">Figure 4
<p>(<b>a</b>) The keywords are shown as colored nodes in the network visualization, and the connections between them are shown as edges. This can assist in determining the groups of relevant keywords and the degree of correlation between them. (<b>b</b>) The overlay visualization compares different sets of data, such as the co-occurrence of keywords providing an overlay visualization map from 2014 to 2024.</p> Full article ">

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