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We have synthesized epitaxially grown freestanding FeSi nanowires (NWs) on an m-Al 2 O 3 substrat... more We have synthesized epitaxially grown freestanding FeSi nanowires (NWs) on an m-Al 2 O 3 substrate by using a catalyst-free chemical vapor transport method. FeSi NW growth is initiated from FeSi nanocrystals, formed on a substrate in a characteristic shape with a specific orientation. Cross-section TEM analysis of seed crystals reveals the crystallographic structure and hidden geometry of the seeds. Close correlation of geometrical shapes and orientations of the observed nanocrystals with those of as-grown NWs indicates that directional growth of NWs is initiated from the epitaxially formed seed crystals. The diameter of NWs can be controlled by adjusting the composition of Si in a Si/C mixture. The epitaxial growth method for FeSi NWs via seed crystals could be employed to heteroepitaxial growth of other compound NWs.
We have developed a Au nanowires (NWs)-on-chip surface-enhanced Raman scattering (SERS) multiplex... more We have developed a Au nanowires (NWs)-on-chip surface-enhanced Raman scattering (SERS) multiplex sensor that can sensitively detect multiple toxic metal ions. Most importantly, the reporter elimination method simplified the detection procedure to a single step, which has been much desired for remote environmental monitoring. This sensor has several notable features. First, it shows high reproducibility based on well-defined single-crystalline Au NWs. Second, single-NW-sensors that can detect a specific metal ion are combined for multiplex sensing of metal ions. Third, when a sample solution is put onto the NWs-on-chip sensor, a decrease in the SERS signal of a specific NW-sensor identifies the target metal ion. Simple, rapid, sensitive and quantitative detection of metal ions becomes possible through the measurement of the SERS signals. We successfully detected ions of mercury (Hg 2+ ), silver (Ag + ), and lead (Pb 2+ ) coexisting in the same solution by using this sensor.
A recent theoretical study suggested that Ag 2 Te is a topological insulator with a highly anisot... more A recent theoretical study suggested that Ag 2 Te is a topological insulator with a highly anisotropic Dirac cone. Novel physics in the topological insulators with an anisotropic Dirac cone is anticipated due to the violation of rotational invariance. From magnetoresistance (MR) measurements of Ag 2 Te nanowires (NWs), we have observed Aharanov−Bohm (AB) oscillation, which is attributed to the quantum interference of electron phase around the perimeter of the NW. Angle and temperature dependences of the AB oscillation indicate the existence of conducting surface states in the NWs, confirming that Ag 2 Te is a topological insulator. For Ag 2 Te nanoplates (NPLs), we have observed high carrier mobility exceeding 22 000 cm 2 /(V s) and pronounced Shubnikov−de Haas (SdH) oscillation. From the SdH oscillation, we have obtained Fermi state parameters of the Ag 2 Te NPLs, which can provide valuable information on Ag 2 Te. Understanding the basic physics of the topological insulator with an anisotropic Dirac cone could lead to new applications in nanoelectronics and spintronics.
Optical antennas interface an object with optical radiation and boost the absorption and emission... more Optical antennas interface an object with optical radiation and boost the absorption and emission of light by the objects through the antenna modes. It has been much desired to enhance both excitation and emission processes of the quantum emitters as well as to interface multiwavelength channels for many nano-optical applications. Here we report the experimental implementation of an optical antenna operating in the full visible range via surface plasmon currents induced in a defect-free single-crystalline Ag nanowire (NW). With its atomically flat surface, the long Ag NW reliably establishes multiple plasmonic resonances and produces a unique rainbow antenna radiation in the Fresnel region. Detailed antenna radiation properties, such as radiating near-field patterns and polarization states, were experimentally examined and precisely analyzed by numerical simulations and antenna theory. The multiresonant Ag NW nanoantenna will find superb applications in nano-optical spectroscopy, high-resolution nanoimaging, photovoltaics, and nonlinear signal conversion.
a] subtle variations in the prominent intrinsic transport properties. . It includes a comparison ... more a] subtle variations in the prominent intrinsic transport properties. . It includes a comparison of the theoretical calculations with the experimental results, MR curves at high-temperature regions, and MR curves of Fe 0.7 Co 0.3 Si NW.
We report the spectroscopic characterization of excited electronic states of KRb by combining spe... more We report the spectroscopic characterization of excited electronic states of KRb by combining spectra from molecular beam (MB) experiments with those from ultracold molecules (UM) formed by photoassociation (PA) of ultracold atoms. Spectra involving the 1 1 P, 2 3 S + , and b 3 P states in a strongly perturbed region have been identified. This approach provides a powerful method to identify the vibrational levels of the excited electronic states perturbed globally by neighboring electronic states. This is because the two sets of spectra from the UM and the MB experiments probe the same energy region from very different initial electronic states. The UM experiments utilize high v 0 0 levels of the a 3 S + state with large internuclear separations, while the MB experiments utilize low v 0 0 levels of the ground X 1 S + state with near-equilibrium internuclear separations. Only the O = 1 levels of the 2 3 S + and b 3 P states are observed in the MB spectra, while the O = 0 À , 1 levels of the 2 3 S + state and the O = 0 AE , 1, 2 levels of the b 3 P state are observed in the UM spectra. ; Fax: +1 860 4863346;
We present herein a silver nanostructure-assisted sensing platform which consists of a combined s... more We present herein a silver nanostructure-assisted sensing platform which consists of a combined structure of Ag nanowire (NW) and nanodot (ND) array. Highly enhanced fluorescence from fluorophore is attributed to a strongly coupled optical near-field interaction between proximately located Ag NW and NDs. We obtained enhanced fluorescence intensity with up to 140 folds, as contrasted from background intensity, reaching a theoretical maximum value. On the other hand, fluorescence lifetime was greatly reduced to 0.27 ns (from 2.17 ns for the same fluorophores without nanostructure). This novel platform can be a promising utility for optical imaging and labeling of biological systems with a great sensitivity. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
b S Supporting Information G raphene has extraordinary properties such as ultrahigh carrier mobil... more b S Supporting Information G raphene has extraordinary properties such as ultrahigh carrier mobility, large light transmission, and flexibility. 1À7 Moreover, low intrinsic spinÀorbit coupling, long spin diffusion lengths, and vanishing hyperfine interaction features of graphene make it a promising medium for spin transport. 8À10 Integrating semiconducting, metallic, or ferromagnetic nanowire (NW) arrays on the graphene surface would offer a good opportunity to combine superb material properties of graphene into a greater variety of applications. 11À20 For optimum performance of the integrated devices, it is critical to have excellent contact between graphene and the NWs, especially for spin transport. To achieve an atomically well-defined interface, epitaxial integration is most desirable. Ferromagnetic metallic NWs epitaxially grown on graphene will form a solid contact between the NW and graphene, thereby allowing effective spin injection from the ferromagnetic NW to graphene. A solid interface between the NWs and graphene will also enable effective field emission (FE) of the NW emitters. Iron germanide NWs are one of the ideal materials to integrate with graphene for such advanced applications as they exhibit low resistivity and room-temperature ferromagnetism and they are compatible with existing complementary metal oxideÀsemiconductor (CMOS) technologies. 21À25 Herein, we report synthesis of ferromagnetic and metallic Fe 1.3 Ge NWs vertically aligned on few-layer graphene in a large area without using any catalysts. To the best of our knowledge, this is the first report on the epitaxial growth of NWs on graphene. Because efficient spin injection and transport could be possible in the Fe 1.3 Ge NWs epitaxially grown on graphene, the NWÀgraphene hybrid structure can play an important role for graphene-based spintronic
A multi-layer nanogap array composed of three linearly aligned gold nanogaps is fabricated for a ... more A multi-layer nanogap array composed of three linearly aligned gold nanogaps is fabricated for a surface-enhanced Raman spectroscopy (SERS) substrate. The overall process for the proposed structure is simple and reliable with the use of a photolithography-free fabrication process, which includes only deposition and etching. Chemical vapor deposition (CVD) is employed to form a uniform and highly controllable nanogap array. The nanogap width, a crucial parameter in SERS, is determined by the sacrificial film thickness of CVD. Experiments on nanogap width and polarization angle dependence are carried out to characterize the fabricated multi-layer nanogap array as an SERS substrate.
H ow would individual atoms in material actually move under mechanical force? In crystalline mate... more H ow would individual atoms in material actually move under mechanical force? In crystalline materials, microscopic atomic movements over one another during a mechanical process are inherently related with macroscopic mechanical properties. 1À4 To decipher the deformation mechanism on an atomic scale, however, defect-induced complex interactions that would seriously puzzle the whole mechanical process should be greatly reduced. 4À8 Fabricating defect-free material can be possible by reducing its size below a certain critical value. 9 Defect-free metal nanowires (NWs) are ideal model systems to explore tensile properties at the nanoscale, since they are free of complex interactions and have well-defined geometries and high aspect ratios. 10 While atomistic simulations have interestingly predicted strong but ductile behavior of single-crystalline metal NWs through deformation twinning, 11À13 only a few experimental studies have been reported on tensile processes of metal NWs, 14À16 of which the plastic deformation has not been observed yet. The successful tensile experiment should meet highly stringent requirements including preparation of samples of extreme crystallinity, delicate manipulation, and an exact alignment of the NW along the tensile force.
Development of a rapid, sensitive, and multiplex pathogen DNA sensor enables early diagnosis and,... more Development of a rapid, sensitive, and multiplex pathogen DNA sensor enables early diagnosis and, subsequently, the proper treatment of infectious diseases, increasing the possibility to save the lives of infected patients. Here, the development of an ultrasensitive and multiplex pathogen DNA detection method that combines a patterned Au nanowire (NW)-on-fi lm surface-enhanced resonance Raman scattering (SERRS) sensor with an exonuclease III-assisted target DNA recycling reaction is reported. Multiple probe DNAs are added to the target DNA solution, and among them, only the complementary probe DNA is selectively digested by exonuclease III, resulting in the decrease in its concentration. The digestion process is repeated by recycling of target DNAs. The decrease of the complementary probe DNA concentration is detected by SERRS. Combining the high sensitivity of the NW-on-film sensor and the target recycling reaction signifi cantly improves DNA detection performance, resulting in the detection limit of 100 f M corresponding to 3 amole. By positioning Au NWs at specifi c addresses, multiple pathogen DNAs can be identified in a single step. Clinical sample tests with multiple genomic DNAs of pathogens show the potential of this sensor for practical diagnosis of infectious diseases.
We show that the multiplicative product of a molecular-beam excitation spectrum and an ultracold-... more We show that the multiplicative product of a molecular-beam excitation spectrum and an ultracold-molecule excitation spectrum, with a frequency offset appropriate to the initial ultracold-molecule level, provides the relative rate of stimulated Raman transfer (SRT) from a given high rovibrational level to the lowest rovibronic level, i.e., the v = 0,J = 0 level of the ground electronic state for photoassociated (and magnetoassociated) ultracold molecules. This product spectrum clearly indicates the optimal pathways for SRT, even when the two component spectra are completely unassigned. We illustrate this specifically for the case of KRb.
Surface-enhanced Raman scattering (SERS) of graphene on a
SiO2ACHTUNGTRENUNG(300 nm)/Si substrat... more Surface-enhanced Raman scattering (SERS) of graphene on a
SiO2ACHTUNGTRENUNG(300 nm)/Si substrate was investigated by depositing Au nanoparticles using thermal evaporation. This provideda maximum enhancement of 120
times for single-layer graphene at 633 nm excitation. SERS spectra andscan images of single-layer and fewlayer graphene were acquired. Singlelayer graphene provides much larger SERS enhancement compared to fewlayergraphene, while in single-layer graphene the enhancement of the G
band was larger than that of the 2D band. Furthermore, the D bands were identified in the SERS spectra; these bands were not observed in a normal Raman spectrum without Au deposition. Appearance of the D band is ascribed to the considerable SERS enhancement and not to an Au deposition- induced defect. Lastly, SERS enhancement of graphene on a transparent glass substrate was compared with
that on the SiO2ACHTUNGTRENUNG(300 nm)/Si substrate to exclude enhancement by multiple reflections between the Si substrate and deposited Au nanoparticles. The contribution of multiple reflections to total enhancement on the SiO2- ACHTUNGTRENUNG(300 nm)/Si substrate was 1.6 times outof average SERS enhancement factor, 71 times.
We report an ultrasensitive and selective single nanowire-on-film (SNOF) surface-enhanced resonan... more We report an ultrasensitive and selective single nanowire-on-film (SNOF) surface-enhanced resonance Raman scattering (SERRS) sensor for Hg2+ detection based on structureswitching double stranded DNAs (dsDNAs). Binding of Hg2+ induces conformational changes of the dsDNAs and let a Raman reporter get close to the SNOF structure, thereby turning on SERRS signal. The well-defined SNOF structure provides a detection limit of 100 pm with improved accuracy in Hg2+ detection. This sensor is stable
over a considerable amount of time and reusable after simple treatment. Since this SNOF sensor is composed of
a single Au NW on a film, development of a multiplex sensor would be possible by employing NWs modified by multiple
kinds of aptamers.
We have synthesized epitaxially grown freestanding FeSi nanowires (NWs) on an m-Al 2 O 3 substrat... more We have synthesized epitaxially grown freestanding FeSi nanowires (NWs) on an m-Al 2 O 3 substrate by using a catalyst-free chemical vapor transport method. FeSi NW growth is initiated from FeSi nanocrystals, formed on a substrate in a characteristic shape with a specific orientation. Cross-section TEM analysis of seed crystals reveals the crystallographic structure and hidden geometry of the seeds. Close correlation of geometrical shapes and orientations of the observed nanocrystals with those of as-grown NWs indicates that directional growth of NWs is initiated from the epitaxially formed seed crystals. The diameter of NWs can be controlled by adjusting the composition of Si in a Si/C mixture. The epitaxial growth method for FeSi NWs via seed crystals could be employed to heteroepitaxial growth of other compound NWs.
We have developed a Au nanowires (NWs)-on-chip surface-enhanced Raman scattering (SERS) multiplex... more We have developed a Au nanowires (NWs)-on-chip surface-enhanced Raman scattering (SERS) multiplex sensor that can sensitively detect multiple toxic metal ions. Most importantly, the reporter elimination method simplified the detection procedure to a single step, which has been much desired for remote environmental monitoring. This sensor has several notable features. First, it shows high reproducibility based on well-defined single-crystalline Au NWs. Second, single-NW-sensors that can detect a specific metal ion are combined for multiplex sensing of metal ions. Third, when a sample solution is put onto the NWs-on-chip sensor, a decrease in the SERS signal of a specific NW-sensor identifies the target metal ion. Simple, rapid, sensitive and quantitative detection of metal ions becomes possible through the measurement of the SERS signals. We successfully detected ions of mercury (Hg 2+ ), silver (Ag + ), and lead (Pb 2+ ) coexisting in the same solution by using this sensor.
A recent theoretical study suggested that Ag 2 Te is a topological insulator with a highly anisot... more A recent theoretical study suggested that Ag 2 Te is a topological insulator with a highly anisotropic Dirac cone. Novel physics in the topological insulators with an anisotropic Dirac cone is anticipated due to the violation of rotational invariance. From magnetoresistance (MR) measurements of Ag 2 Te nanowires (NWs), we have observed Aharanov−Bohm (AB) oscillation, which is attributed to the quantum interference of electron phase around the perimeter of the NW. Angle and temperature dependences of the AB oscillation indicate the existence of conducting surface states in the NWs, confirming that Ag 2 Te is a topological insulator. For Ag 2 Te nanoplates (NPLs), we have observed high carrier mobility exceeding 22 000 cm 2 /(V s) and pronounced Shubnikov−de Haas (SdH) oscillation. From the SdH oscillation, we have obtained Fermi state parameters of the Ag 2 Te NPLs, which can provide valuable information on Ag 2 Te. Understanding the basic physics of the topological insulator with an anisotropic Dirac cone could lead to new applications in nanoelectronics and spintronics.
Optical antennas interface an object with optical radiation and boost the absorption and emission... more Optical antennas interface an object with optical radiation and boost the absorption and emission of light by the objects through the antenna modes. It has been much desired to enhance both excitation and emission processes of the quantum emitters as well as to interface multiwavelength channels for many nano-optical applications. Here we report the experimental implementation of an optical antenna operating in the full visible range via surface plasmon currents induced in a defect-free single-crystalline Ag nanowire (NW). With its atomically flat surface, the long Ag NW reliably establishes multiple plasmonic resonances and produces a unique rainbow antenna radiation in the Fresnel region. Detailed antenna radiation properties, such as radiating near-field patterns and polarization states, were experimentally examined and precisely analyzed by numerical simulations and antenna theory. The multiresonant Ag NW nanoantenna will find superb applications in nano-optical spectroscopy, high-resolution nanoimaging, photovoltaics, and nonlinear signal conversion.
a] subtle variations in the prominent intrinsic transport properties. . It includes a comparison ... more a] subtle variations in the prominent intrinsic transport properties. . It includes a comparison of the theoretical calculations with the experimental results, MR curves at high-temperature regions, and MR curves of Fe 0.7 Co 0.3 Si NW.
We report the spectroscopic characterization of excited electronic states of KRb by combining spe... more We report the spectroscopic characterization of excited electronic states of KRb by combining spectra from molecular beam (MB) experiments with those from ultracold molecules (UM) formed by photoassociation (PA) of ultracold atoms. Spectra involving the 1 1 P, 2 3 S + , and b 3 P states in a strongly perturbed region have been identified. This approach provides a powerful method to identify the vibrational levels of the excited electronic states perturbed globally by neighboring electronic states. This is because the two sets of spectra from the UM and the MB experiments probe the same energy region from very different initial electronic states. The UM experiments utilize high v 0 0 levels of the a 3 S + state with large internuclear separations, while the MB experiments utilize low v 0 0 levels of the ground X 1 S + state with near-equilibrium internuclear separations. Only the O = 1 levels of the 2 3 S + and b 3 P states are observed in the MB spectra, while the O = 0 À , 1 levels of the 2 3 S + state and the O = 0 AE , 1, 2 levels of the b 3 P state are observed in the UM spectra. ; Fax: +1 860 4863346;
We present herein a silver nanostructure-assisted sensing platform which consists of a combined s... more We present herein a silver nanostructure-assisted sensing platform which consists of a combined structure of Ag nanowire (NW) and nanodot (ND) array. Highly enhanced fluorescence from fluorophore is attributed to a strongly coupled optical near-field interaction between proximately located Ag NW and NDs. We obtained enhanced fluorescence intensity with up to 140 folds, as contrasted from background intensity, reaching a theoretical maximum value. On the other hand, fluorescence lifetime was greatly reduced to 0.27 ns (from 2.17 ns for the same fluorophores without nanostructure). This novel platform can be a promising utility for optical imaging and labeling of biological systems with a great sensitivity. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
b S Supporting Information G raphene has extraordinary properties such as ultrahigh carrier mobil... more b S Supporting Information G raphene has extraordinary properties such as ultrahigh carrier mobility, large light transmission, and flexibility. 1À7 Moreover, low intrinsic spinÀorbit coupling, long spin diffusion lengths, and vanishing hyperfine interaction features of graphene make it a promising medium for spin transport. 8À10 Integrating semiconducting, metallic, or ferromagnetic nanowire (NW) arrays on the graphene surface would offer a good opportunity to combine superb material properties of graphene into a greater variety of applications. 11À20 For optimum performance of the integrated devices, it is critical to have excellent contact between graphene and the NWs, especially for spin transport. To achieve an atomically well-defined interface, epitaxial integration is most desirable. Ferromagnetic metallic NWs epitaxially grown on graphene will form a solid contact between the NW and graphene, thereby allowing effective spin injection from the ferromagnetic NW to graphene. A solid interface between the NWs and graphene will also enable effective field emission (FE) of the NW emitters. Iron germanide NWs are one of the ideal materials to integrate with graphene for such advanced applications as they exhibit low resistivity and room-temperature ferromagnetism and they are compatible with existing complementary metal oxideÀsemiconductor (CMOS) technologies. 21À25 Herein, we report synthesis of ferromagnetic and metallic Fe 1.3 Ge NWs vertically aligned on few-layer graphene in a large area without using any catalysts. To the best of our knowledge, this is the first report on the epitaxial growth of NWs on graphene. Because efficient spin injection and transport could be possible in the Fe 1.3 Ge NWs epitaxially grown on graphene, the NWÀgraphene hybrid structure can play an important role for graphene-based spintronic
A multi-layer nanogap array composed of three linearly aligned gold nanogaps is fabricated for a ... more A multi-layer nanogap array composed of three linearly aligned gold nanogaps is fabricated for a surface-enhanced Raman spectroscopy (SERS) substrate. The overall process for the proposed structure is simple and reliable with the use of a photolithography-free fabrication process, which includes only deposition and etching. Chemical vapor deposition (CVD) is employed to form a uniform and highly controllable nanogap array. The nanogap width, a crucial parameter in SERS, is determined by the sacrificial film thickness of CVD. Experiments on nanogap width and polarization angle dependence are carried out to characterize the fabricated multi-layer nanogap array as an SERS substrate.
H ow would individual atoms in material actually move under mechanical force? In crystalline mate... more H ow would individual atoms in material actually move under mechanical force? In crystalline materials, microscopic atomic movements over one another during a mechanical process are inherently related with macroscopic mechanical properties. 1À4 To decipher the deformation mechanism on an atomic scale, however, defect-induced complex interactions that would seriously puzzle the whole mechanical process should be greatly reduced. 4À8 Fabricating defect-free material can be possible by reducing its size below a certain critical value. 9 Defect-free metal nanowires (NWs) are ideal model systems to explore tensile properties at the nanoscale, since they are free of complex interactions and have well-defined geometries and high aspect ratios. 10 While atomistic simulations have interestingly predicted strong but ductile behavior of single-crystalline metal NWs through deformation twinning, 11À13 only a few experimental studies have been reported on tensile processes of metal NWs, 14À16 of which the plastic deformation has not been observed yet. The successful tensile experiment should meet highly stringent requirements including preparation of samples of extreme crystallinity, delicate manipulation, and an exact alignment of the NW along the tensile force.
Development of a rapid, sensitive, and multiplex pathogen DNA sensor enables early diagnosis and,... more Development of a rapid, sensitive, and multiplex pathogen DNA sensor enables early diagnosis and, subsequently, the proper treatment of infectious diseases, increasing the possibility to save the lives of infected patients. Here, the development of an ultrasensitive and multiplex pathogen DNA detection method that combines a patterned Au nanowire (NW)-on-fi lm surface-enhanced resonance Raman scattering (SERRS) sensor with an exonuclease III-assisted target DNA recycling reaction is reported. Multiple probe DNAs are added to the target DNA solution, and among them, only the complementary probe DNA is selectively digested by exonuclease III, resulting in the decrease in its concentration. The digestion process is repeated by recycling of target DNAs. The decrease of the complementary probe DNA concentration is detected by SERRS. Combining the high sensitivity of the NW-on-film sensor and the target recycling reaction signifi cantly improves DNA detection performance, resulting in the detection limit of 100 f M corresponding to 3 amole. By positioning Au NWs at specifi c addresses, multiple pathogen DNAs can be identified in a single step. Clinical sample tests with multiple genomic DNAs of pathogens show the potential of this sensor for practical diagnosis of infectious diseases.
We show that the multiplicative product of a molecular-beam excitation spectrum and an ultracold-... more We show that the multiplicative product of a molecular-beam excitation spectrum and an ultracold-molecule excitation spectrum, with a frequency offset appropriate to the initial ultracold-molecule level, provides the relative rate of stimulated Raman transfer (SRT) from a given high rovibrational level to the lowest rovibronic level, i.e., the v = 0,J = 0 level of the ground electronic state for photoassociated (and magnetoassociated) ultracold molecules. This product spectrum clearly indicates the optimal pathways for SRT, even when the two component spectra are completely unassigned. We illustrate this specifically for the case of KRb.
Surface-enhanced Raman scattering (SERS) of graphene on a
SiO2ACHTUNGTRENUNG(300 nm)/Si substrat... more Surface-enhanced Raman scattering (SERS) of graphene on a
SiO2ACHTUNGTRENUNG(300 nm)/Si substrate was investigated by depositing Au nanoparticles using thermal evaporation. This provideda maximum enhancement of 120
times for single-layer graphene at 633 nm excitation. SERS spectra andscan images of single-layer and fewlayer graphene were acquired. Singlelayer graphene provides much larger SERS enhancement compared to fewlayergraphene, while in single-layer graphene the enhancement of the G
band was larger than that of the 2D band. Furthermore, the D bands were identified in the SERS spectra; these bands were not observed in a normal Raman spectrum without Au deposition. Appearance of the D band is ascribed to the considerable SERS enhancement and not to an Au deposition- induced defect. Lastly, SERS enhancement of graphene on a transparent glass substrate was compared with
that on the SiO2ACHTUNGTRENUNG(300 nm)/Si substrate to exclude enhancement by multiple reflections between the Si substrate and deposited Au nanoparticles. The contribution of multiple reflections to total enhancement on the SiO2- ACHTUNGTRENUNG(300 nm)/Si substrate was 1.6 times outof average SERS enhancement factor, 71 times.
We report an ultrasensitive and selective single nanowire-on-film (SNOF) surface-enhanced resonan... more We report an ultrasensitive and selective single nanowire-on-film (SNOF) surface-enhanced resonance Raman scattering (SERRS) sensor for Hg2+ detection based on structureswitching double stranded DNAs (dsDNAs). Binding of Hg2+ induces conformational changes of the dsDNAs and let a Raman reporter get close to the SNOF structure, thereby turning on SERRS signal. The well-defined SNOF structure provides a detection limit of 100 pm with improved accuracy in Hg2+ detection. This sensor is stable
over a considerable amount of time and reusable after simple treatment. Since this SNOF sensor is composed of
a single Au NW on a film, development of a multiplex sensor would be possible by employing NWs modified by multiple
kinds of aptamers.
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Papers by bongsoo kim
SiO2ACHTUNGTRENUNG(300 nm)/Si substrate was investigated by depositing Au nanoparticles using thermal evaporation. This provideda maximum enhancement of 120
times for single-layer graphene at 633 nm excitation. SERS spectra andscan images of single-layer and fewlayer graphene were acquired. Singlelayer graphene provides much larger SERS enhancement compared to fewlayergraphene, while in single-layer graphene the enhancement of the G
band was larger than that of the 2D band. Furthermore, the D bands were identified in the SERS spectra; these bands were not observed in a normal Raman spectrum without Au deposition. Appearance of the D band is ascribed to the considerable SERS enhancement and not to an Au deposition- induced defect. Lastly, SERS enhancement of graphene on a transparent glass substrate was compared with
that on the SiO2ACHTUNGTRENUNG(300 nm)/Si substrate to exclude enhancement by multiple reflections between the Si substrate and deposited Au nanoparticles. The contribution of multiple reflections to total enhancement on the SiO2- ACHTUNGTRENUNG(300 nm)/Si substrate was 1.6 times outof average SERS enhancement factor, 71 times.
over a considerable amount of time and reusable after simple treatment. Since this SNOF sensor is composed of
a single Au NW on a film, development of a multiplex sensor would be possible by employing NWs modified by multiple
kinds of aptamers.
SiO2ACHTUNGTRENUNG(300 nm)/Si substrate was investigated by depositing Au nanoparticles using thermal evaporation. This provideda maximum enhancement of 120
times for single-layer graphene at 633 nm excitation. SERS spectra andscan images of single-layer and fewlayer graphene were acquired. Singlelayer graphene provides much larger SERS enhancement compared to fewlayergraphene, while in single-layer graphene the enhancement of the G
band was larger than that of the 2D band. Furthermore, the D bands were identified in the SERS spectra; these bands were not observed in a normal Raman spectrum without Au deposition. Appearance of the D band is ascribed to the considerable SERS enhancement and not to an Au deposition- induced defect. Lastly, SERS enhancement of graphene on a transparent glass substrate was compared with
that on the SiO2ACHTUNGTRENUNG(300 nm)/Si substrate to exclude enhancement by multiple reflections between the Si substrate and deposited Au nanoparticles. The contribution of multiple reflections to total enhancement on the SiO2- ACHTUNGTRENUNG(300 nm)/Si substrate was 1.6 times outof average SERS enhancement factor, 71 times.
over a considerable amount of time and reusable after simple treatment. Since this SNOF sensor is composed of
a single Au NW on a film, development of a multiplex sensor would be possible by employing NWs modified by multiple
kinds of aptamers.