Proceedings of Spie the International Society For Optical Engineering, Aug 1, 2010
Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Lang... more Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Langmuir-Blodgett technique. Initial studies of Langmuir-Blodgettry were done with arachidic acid to optimize monolayer deposition parameters. Hydrophilic and hydrophobic glass substrates were prepared and coated with arachidic acid. SERS monolayer substrates were then made from Ag nanostructures. Deposition of Ag nanoparticles using the Langmuir Blodgett technique resulted in
We present materials development in fabricating thin film devices for the conversion of wind ener... more We present materials development in fabricating thin film devices for the conversion of wind energy as a sustainable energy source. We demonstrate the feasibility of piezoelectric polymer thin film devices to harvest wind energy in a miniature wind tunnel. Using an example of prototype device based on polyvinylidene fluoride (PVDF) thin film devices, we are able to obtain electrical power from the wind’s energy through the mechanical deformation of PVDF, such as that obtained from the films flapping in the wind. We have obtained a preliminary result of 1 mW power (at 15 mph wind) with a single layer of PVDF of 4 x 2 inches and 50 μm in thickness sandwiched between two thin gold electrode films. Additionally, the fracturing of metallic electrodes over time from the induced strain of this application lead to the significance of examining carbon nanotubes as compliant electrodes offering better mechanical properties while maintaining necessary electrical properties.
ABSTRACTThis study presents a materials development of composite electrode materials of graphene ... more ABSTRACTThis study presents a materials development of composite electrode materials of graphene oxide (GO) and transition metal oxide nanostructures. Reduced graphene oxide (rGO) films were obtained by electrophoretic deposition (EPD) onto a conductive substrate. Co3O4 and MnO2 nanostructures were synthesized to form composites with rGO. Graphene materials, with high electrical conductivity, high specific surface area and excellent mechanical properties are ideal for a host of electrical applications. The properties of metal oxides like Co3O4 and MnO2 has allowed for increased energy density, while rGO increases charge storage and transport in the electrical double layer at the electrode/electrolyte interface. Graphene and metal oxide composites offer increased energy density and capacitance compared with traditional double layer supercapacitors.
The paper present a multimode optical fiber based solar lighting and photovoltaic multifunctional... more The paper present a multimode optical fiber based solar lighting and photovoltaic multifunctional device. TiO2, PbS and conducting polymer poly(3-hexylthiophene) (P3HT) were coated on the optical core surface as active photovoltaic layers, with ITO and LiF/Al electrodes. The guided sunlight in the multi-moded fiber was totally internal reflected depending on the incident angle and the evanescent light mode from scattered radiation of light was absorbed by the active layer to generate the electric current. The optical-electrical behaviors such as the short circuit current, filling factor, and open circuit voltage were studied. Furthermore, optical loss and the evanescent field at the interface between the optical fiber core and ITO electrode thin layer was discussed in relation to the coupling light from the guiding medium to the devices. Comparison studies of chemical and physical thin film coating on optical fibers are discussed. In particular, we obtained in situ growth of quantum...
Great focus has been directed towards double-layer capacitance and Faradic, redox reactions becau... more Great focus has been directed towards double-layer capacitance and Faradic, redox reactions because of their long device lifetimes and their high power densities, respectively. Our novel approach to combining these mechanisms in a tri-layered composite electrode promises to increase the energy densities of the device, without sacrificing the supercapacitance and the high power densities attributed with it. Initial analysis of the interfacial interactions of graphene oxide (GO) and manganese oxide (MnO2) were promising. This paper aims to further demonstrate the tri-layered composite by forming a layer of reduced graphene oxide (rGO) on MnO2 nanowires and cobalt oxide nanorods. We have successfully created the first of a kind supercapacitor electrode material as a scalable device. In this paper, in addition to analysis of the composite electrode, we present modifications to the traditional electrophoretic deposition process and optimizations to the thermal reduction of GO in order to...
The Proterozoic carbonate stromatolites of the Pahrump Group from the Crystal Spring formation ex... more The Proterozoic carbonate stromatolites of the Pahrump Group from the Crystal Spring formation exhibit interesting layering patterns. In continuous vertical formations, there are sections of chevron-shaped stromatolites alternating with sections of simple horizontal layering. This apparent cycle of stromatolite formation and lack of formation repeats several times over a vertical distance of at least 30 m at the locality investigated. Small representative samples from each layer were taken and analysed using X-ray diffraction (XRD), X-ray fluorescence (XRF), environmental scanning electron microscopy - energy dispersive X-ray spectrometry, and were optically analysed in thin section. Optical and spectroscopic analyses of stromatolite and of non-stromatolite samples were undertaken with the objective of determining the differences between them. Elemental analysis of samples from within each of the four stromatolite layers and the four intervening layers shows that the two types of la...
Raman spectroscopy has promising potential for future Mars missions as a non-contact detection te... more Raman spectroscopy has promising potential for future Mars missions as a non-contact detection technique for characterizing organic material and mineralogy. Such a capability will be useful for selecting samples for detailed analysis on a rover and for selecting samples for return to Earth. Stromatolites are important evidence for the earliest life on Earth and are promising targets for Mars investigations. Although constructed by microorganisms, stromatolites are organo-sedimentary structures that can be large enough to be discovered and investigated by a Mars rover. In this paper, we report the Raman spectroscopic investigations of the carbonate mineralogy and organic layering in a Precambrian (~1.5 Gyr old) stromatolite from the Crystal Spring Formation of Southern California. Ultraviolet (UV: 266 nm), visible (514 nm, 633 nm), and near-infrared (NIR: 785 nm, 1064 nm) Raman spectra are presented. We conclude that 1064 nm excitation is the optimal excitation wavelength for avoiding intrinsic fluorescence and detecting organic carbon within the carbonate matrix. Our results confirm that NIR Raman spectroscopy has important applications for future Mars missions.
Instruments, Methods, and Missions for Astrobiology XIII, 2010
Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Lang... more Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Langmuir-Blodgett technique. Initial studies of Langmuir-Blodgettry were done with arachidic acid to optimize monolayer deposition parameters. Hydrophilic and hydrophobic glass substrates were prepared and coated with arachidic acid. SERS monolayer substrates were then made from Ag nanostructures. Deposition of Ag nanoparticles using the Langmuir Blodgett technique resulted in
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2012
ABSTRACT This study presents composite electrode materials based on graphene oxide (GO) and trans... more ABSTRACT This study presents composite electrode materials based on graphene oxide (GO) and transition metal oxide nanostructures for supercapacitor applications. Electrophoretic deposition of GO on a conductive substrate was used to form reduced graphene oxide (rGO) films through chemical reduction. The specific capacitance of the rGO was calculated up to 117 F/g at 100 mV/s scan rate from KOH (1 M) electrolyte using an Ag/AgCl reference electrode. The strong interaction of GO with Co3O4 and MnO2 nanostructures was demonstrated in the self-assembled Langmuir–Blodgett monolayer composite, showing the potential to fabricate thin film supercapacitor electrodes without using binder materials. This two-step process is nontoxic and scalable and holds promise for improved energy density from redox capacitance in comparison with the conventional double layer supercapacitors.
ABSTRACT We report a new facile route for preparing surface-enhanced Raman scattering (SERS) subs... more ABSTRACT We report a new facile route for preparing surface-enhanced Raman scattering (SERS) substrates with tailored enhancement mechanisms. Silver nanowires were assembled using the Langmuir–Blodgett (LB) technique and further processed via galvanic replacement reactions (GRRs). The GRRs provided an efficient method to decrease the spectral noise caused by the capping agent polyvinylpyrrolidone. A decrease in noise along with the addition of gold nanostructures to the system revealed Raman signals from nonfluorescent molecules associated with a charge-transfer mechanism. The GRR LB substrates exhibited ultrasensitive SERS ability with a detection limit as low as 8 nM using 4-aminothiophenol, partially due to the strong chemical binding between the SERS substrates and probe molecules. Furthermore, the GRRs provide a facile route in tailoring SERS substrates to target molecules in a controlled manner.
A biosensor based on an array of vertically aligned carbon nanofibers (CNFs) grown by plasma enha... more A biosensor based on an array of vertically aligned carbon nanofibers (CNFs) grown by plasma enhanced chemical vapor deposition is found to be effective for the simultaneous detection of dopamine (DA) and serotonin (5-HT) in the presence of excess ascorbic acid (AA). The CNF electrode outperforms the conventional glassy carbon electrode (GCE) for both selectivity and sensitivity. Using differential pulse voltammetry (DPV), three distinct peaks are seen for the CNF electrode at 0.13 V, 0.45 V, and 0.70 V for the ternary mixture of AA, DA, and 5-HT. In contrast, the analytes are indistinguishable in a mixture using a GCE. For the CNF electrode, the detection limits are 50 nM for DA and 250 nM for 5-HT.
Raman spectroscopy has promising potential for future Mars missions as a non-contact detection te... more Raman spectroscopy has promising potential for future Mars missions as a non-contact detection technique for characterizing organic material and mineralogy. Such a capability will be useful for selecting samples for detailed analysis on a rover and for selecting samples for return to Earth. Stromatolites are important evidence for the earliest life on Earth and are promising targets for Mars investigations. Although constructed by microorganisms, stromatolites are organo-sedimentary structures that can be large enough to be discovered and investigated by a Mars rover. In this paper, we report the Raman spectroscopic investigations of the carbonate mineralogy and organic layering in a Precambrian (~1.5 Gyr old) stromatolite from the Crystal Spring Formation of Southern California. Ultraviolet (UV: 266 nm), visible (514 nm, 633 nm), and near-infrared (NIR: 785 nm, 1064 nm) Raman spectra are presented. We conclude that 1064 nm excitation is the optimal excitation wavelength for avoiding intrinsic fluorescence and detecting organic carbon within the carbonate matrix. Our results confirm that NIR Raman spectroscopy has important applications for future Mars missions.
Facile and reproducible SERS signals from Shewanella oneidensis were obtained utilizing silver na... more Facile and reproducible SERS signals from Shewanella oneidensis were obtained utilizing silver nanoparticles (AgNPs) and silver nanowires (AgNWs). Additionally, SERS images identify the distribution of SERS hot-spots. One important observation is the synergistically enhanced SERS signal when AgNPs and AgNWs are used in conjunction, due to constructively enhanced electromagnetic field.
Proceedings of Spie the International Society For Optical Engineering, Aug 1, 2010
Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Lang... more Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Langmuir-Blodgett technique. Initial studies of Langmuir-Blodgettry were done with arachidic acid to optimize monolayer deposition parameters. Hydrophilic and hydrophobic glass substrates were prepared and coated with arachidic acid. SERS monolayer substrates were then made from Ag nanostructures. Deposition of Ag nanoparticles using the Langmuir Blodgett technique resulted in
We present materials development in fabricating thin film devices for the conversion of wind ener... more We present materials development in fabricating thin film devices for the conversion of wind energy as a sustainable energy source. We demonstrate the feasibility of piezoelectric polymer thin film devices to harvest wind energy in a miniature wind tunnel. Using an example of prototype device based on polyvinylidene fluoride (PVDF) thin film devices, we are able to obtain electrical power from the wind’s energy through the mechanical deformation of PVDF, such as that obtained from the films flapping in the wind. We have obtained a preliminary result of 1 mW power (at 15 mph wind) with a single layer of PVDF of 4 x 2 inches and 50 μm in thickness sandwiched between two thin gold electrode films. Additionally, the fracturing of metallic electrodes over time from the induced strain of this application lead to the significance of examining carbon nanotubes as compliant electrodes offering better mechanical properties while maintaining necessary electrical properties.
ABSTRACTThis study presents a materials development of composite electrode materials of graphene ... more ABSTRACTThis study presents a materials development of composite electrode materials of graphene oxide (GO) and transition metal oxide nanostructures. Reduced graphene oxide (rGO) films were obtained by electrophoretic deposition (EPD) onto a conductive substrate. Co3O4 and MnO2 nanostructures were synthesized to form composites with rGO. Graphene materials, with high electrical conductivity, high specific surface area and excellent mechanical properties are ideal for a host of electrical applications. The properties of metal oxides like Co3O4 and MnO2 has allowed for increased energy density, while rGO increases charge storage and transport in the electrical double layer at the electrode/electrolyte interface. Graphene and metal oxide composites offer increased energy density and capacitance compared with traditional double layer supercapacitors.
The paper present a multimode optical fiber based solar lighting and photovoltaic multifunctional... more The paper present a multimode optical fiber based solar lighting and photovoltaic multifunctional device. TiO2, PbS and conducting polymer poly(3-hexylthiophene) (P3HT) were coated on the optical core surface as active photovoltaic layers, with ITO and LiF/Al electrodes. The guided sunlight in the multi-moded fiber was totally internal reflected depending on the incident angle and the evanescent light mode from scattered radiation of light was absorbed by the active layer to generate the electric current. The optical-electrical behaviors such as the short circuit current, filling factor, and open circuit voltage were studied. Furthermore, optical loss and the evanescent field at the interface between the optical fiber core and ITO electrode thin layer was discussed in relation to the coupling light from the guiding medium to the devices. Comparison studies of chemical and physical thin film coating on optical fibers are discussed. In particular, we obtained in situ growth of quantum...
Great focus has been directed towards double-layer capacitance and Faradic, redox reactions becau... more Great focus has been directed towards double-layer capacitance and Faradic, redox reactions because of their long device lifetimes and their high power densities, respectively. Our novel approach to combining these mechanisms in a tri-layered composite electrode promises to increase the energy densities of the device, without sacrificing the supercapacitance and the high power densities attributed with it. Initial analysis of the interfacial interactions of graphene oxide (GO) and manganese oxide (MnO2) were promising. This paper aims to further demonstrate the tri-layered composite by forming a layer of reduced graphene oxide (rGO) on MnO2 nanowires and cobalt oxide nanorods. We have successfully created the first of a kind supercapacitor electrode material as a scalable device. In this paper, in addition to analysis of the composite electrode, we present modifications to the traditional electrophoretic deposition process and optimizations to the thermal reduction of GO in order to...
The Proterozoic carbonate stromatolites of the Pahrump Group from the Crystal Spring formation ex... more The Proterozoic carbonate stromatolites of the Pahrump Group from the Crystal Spring formation exhibit interesting layering patterns. In continuous vertical formations, there are sections of chevron-shaped stromatolites alternating with sections of simple horizontal layering. This apparent cycle of stromatolite formation and lack of formation repeats several times over a vertical distance of at least 30 m at the locality investigated. Small representative samples from each layer were taken and analysed using X-ray diffraction (XRD), X-ray fluorescence (XRF), environmental scanning electron microscopy - energy dispersive X-ray spectrometry, and were optically analysed in thin section. Optical and spectroscopic analyses of stromatolite and of non-stromatolite samples were undertaken with the objective of determining the differences between them. Elemental analysis of samples from within each of the four stromatolite layers and the four intervening layers shows that the two types of la...
Raman spectroscopy has promising potential for future Mars missions as a non-contact detection te... more Raman spectroscopy has promising potential for future Mars missions as a non-contact detection technique for characterizing organic material and mineralogy. Such a capability will be useful for selecting samples for detailed analysis on a rover and for selecting samples for return to Earth. Stromatolites are important evidence for the earliest life on Earth and are promising targets for Mars investigations. Although constructed by microorganisms, stromatolites are organo-sedimentary structures that can be large enough to be discovered and investigated by a Mars rover. In this paper, we report the Raman spectroscopic investigations of the carbonate mineralogy and organic layering in a Precambrian (~1.5 Gyr old) stromatolite from the Crystal Spring Formation of Southern California. Ultraviolet (UV: 266 nm), visible (514 nm, 633 nm), and near-infrared (NIR: 785 nm, 1064 nm) Raman spectra are presented. We conclude that 1064 nm excitation is the optimal excitation wavelength for avoiding intrinsic fluorescence and detecting organic carbon within the carbonate matrix. Our results confirm that NIR Raman spectroscopy has important applications for future Mars missions.
Instruments, Methods, and Missions for Astrobiology XIII, 2010
Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Lang... more Robust, tunable Surface enhanced Raman spectroscopy (SERS) substrates were created using the Langmuir-Blodgett technique. Initial studies of Langmuir-Blodgettry were done with arachidic acid to optimize monolayer deposition parameters. Hydrophilic and hydrophobic glass substrates were prepared and coated with arachidic acid. SERS monolayer substrates were then made from Ag nanostructures. Deposition of Ag nanoparticles using the Langmuir Blodgett technique resulted in
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2012
ABSTRACT This study presents composite electrode materials based on graphene oxide (GO) and trans... more ABSTRACT This study presents composite electrode materials based on graphene oxide (GO) and transition metal oxide nanostructures for supercapacitor applications. Electrophoretic deposition of GO on a conductive substrate was used to form reduced graphene oxide (rGO) films through chemical reduction. The specific capacitance of the rGO was calculated up to 117 F/g at 100 mV/s scan rate from KOH (1 M) electrolyte using an Ag/AgCl reference electrode. The strong interaction of GO with Co3O4 and MnO2 nanostructures was demonstrated in the self-assembled Langmuir–Blodgett monolayer composite, showing the potential to fabricate thin film supercapacitor electrodes without using binder materials. This two-step process is nontoxic and scalable and holds promise for improved energy density from redox capacitance in comparison with the conventional double layer supercapacitors.
ABSTRACT We report a new facile route for preparing surface-enhanced Raman scattering (SERS) subs... more ABSTRACT We report a new facile route for preparing surface-enhanced Raman scattering (SERS) substrates with tailored enhancement mechanisms. Silver nanowires were assembled using the Langmuir–Blodgett (LB) technique and further processed via galvanic replacement reactions (GRRs). The GRRs provided an efficient method to decrease the spectral noise caused by the capping agent polyvinylpyrrolidone. A decrease in noise along with the addition of gold nanostructures to the system revealed Raman signals from nonfluorescent molecules associated with a charge-transfer mechanism. The GRR LB substrates exhibited ultrasensitive SERS ability with a detection limit as low as 8 nM using 4-aminothiophenol, partially due to the strong chemical binding between the SERS substrates and probe molecules. Furthermore, the GRRs provide a facile route in tailoring SERS substrates to target molecules in a controlled manner.
A biosensor based on an array of vertically aligned carbon nanofibers (CNFs) grown by plasma enha... more A biosensor based on an array of vertically aligned carbon nanofibers (CNFs) grown by plasma enhanced chemical vapor deposition is found to be effective for the simultaneous detection of dopamine (DA) and serotonin (5-HT) in the presence of excess ascorbic acid (AA). The CNF electrode outperforms the conventional glassy carbon electrode (GCE) for both selectivity and sensitivity. Using differential pulse voltammetry (DPV), three distinct peaks are seen for the CNF electrode at 0.13 V, 0.45 V, and 0.70 V for the ternary mixture of AA, DA, and 5-HT. In contrast, the analytes are indistinguishable in a mixture using a GCE. For the CNF electrode, the detection limits are 50 nM for DA and 250 nM for 5-HT.
Raman spectroscopy has promising potential for future Mars missions as a non-contact detection te... more Raman spectroscopy has promising potential for future Mars missions as a non-contact detection technique for characterizing organic material and mineralogy. Such a capability will be useful for selecting samples for detailed analysis on a rover and for selecting samples for return to Earth. Stromatolites are important evidence for the earliest life on Earth and are promising targets for Mars investigations. Although constructed by microorganisms, stromatolites are organo-sedimentary structures that can be large enough to be discovered and investigated by a Mars rover. In this paper, we report the Raman spectroscopic investigations of the carbonate mineralogy and organic layering in a Precambrian (~1.5 Gyr old) stromatolite from the Crystal Spring Formation of Southern California. Ultraviolet (UV: 266 nm), visible (514 nm, 633 nm), and near-infrared (NIR: 785 nm, 1064 nm) Raman spectra are presented. We conclude that 1064 nm excitation is the optimal excitation wavelength for avoiding intrinsic fluorescence and detecting organic carbon within the carbonate matrix. Our results confirm that NIR Raman spectroscopy has important applications for future Mars missions.
Facile and reproducible SERS signals from Shewanella oneidensis were obtained utilizing silver na... more Facile and reproducible SERS signals from Shewanella oneidensis were obtained utilizing silver nanoparticles (AgNPs) and silver nanowires (AgNWs). Additionally, SERS images identify the distribution of SERS hot-spots. One important observation is the synergistically enhanced SERS signal when AgNPs and AgNWs are used in conjunction, due to constructively enhanced electromagnetic field.
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Papers by Zuki Tanaka