In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfolia... more In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfoliated graphene via the formation of dibromocyclopropyl adducts. This is achieved using a basic-aqueous/organic bi-phasic reaction mixture to decompose the dibromocarbene precursor, bromoform, in conjunction with a phase transfer catalyst to facilitate ylide formation and carbene migration to graphene substrates. DBC-functionalized graphene (DBC-graphene) was characterized using a range of spectroscopic and analytical techniques to confirm the covalent nature of functionalization. Modified optical and electronic properties of DBC-graphene were investigated using UV-vis spectroscopy, analysis of electrical I-V transport properties and using non-contact terahertz time-domain spectroscopy (TTDS). The implications of the carbene functionalization of graphene are considered in the context of scalable radical functionalization methodologies for bulk-scale graphene processing and controlled band-gap manipulation of graphene.
The area of terahertz science and applications has grown dramatically in the last 30 years. Instr... more The area of terahertz science and applications has grown dramatically in the last 30 years. Instrumental platforms for THz measurements have also proliferated, and now include laser-based, electronic, opto-electronic, and microwave photonics devices. As the field matured, metrology and standardization have gained focused attention, resulting in an increasing number of publications and a book devoted to the subject. However, these have been primarily focused on photonic-based free-space techniques and their particular demands and issues. This paper presents a brief review of metrology requirements for active THz electronic devices, the available instrumentation, state of the art, and challenges.
ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of... more ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of textiles are shown to have different THz optical properties, which may be employed to combat textile counterfeiting.
A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon a... more A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon absorption peaks with the increase of S content is shown to have complex transformation, which should be considered in the design of dispersion equations for THz applications.
ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are inve... more ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are investigated using THz time-domain spectroscopy, Raman, FTIR and ellipsometry. The optical properties are related to modifications in the crystal structure.
A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. D... more A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. Different types of crystals are shown to have different THz optical properties and anisotropy, which may be employed for THz applications.
Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate g... more Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate glasses. New glass compositions doped with Pr3+-ions were fabricated using controlled atmosphere melting and casting techniques. The optical properties of new bulk glasses were studied by spectruscopic techniques. The significance of an empirically derived total loss curve for bulk glass is examined for the design of a 1.3 µm amplifier. The concentration effects of Pr3+-ions as a dopant in the glass were studied, and its absorption cross-section measured to establish the ground state absorption in bulk glass. The thermal stability of mixed halide glasses was studied by differential scanning calorimetry. and an appraisal of their devitrification behaviour is presented.
Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs an... more Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs and GaSex-1Sx and other nonlinear optical crystals in the FIRand THz regimes using the classic Maker Fringe and Z-scan techniques. The Z-scan measurements were conducted successfully, in both the FIRand THz regimes, and the measurement results in the FIR were found to be in reasonable agreement with the available literature [7, 8, 9]. Wecan conclude that multi-photon absorption in the FIR is no more an impediment to pumping, GaSe based, nonlinear frequency conversiondevices that in the near-IR.
Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host ... more Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host for 1.3µm Pr3+-doped optical fibre amplifier. We report the crystallization behaviour of the mixed halide glasses while reheated above their glass transition temperature. The effect of impurities in the starting raw materials on the quality of the bulk glass is reported. The OH- absorption was monitored by FTIR technique, and related to the lifetime of the 1G4 excited state in Pr3+-doped glass. The thermal stability of the glass was studied from heat treatment data using a differential scanning calorimeter.
In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfolia... more In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfoliated graphene via the formation of dibromocyclopropyl adducts. This is achieved using a basic-aqueous/organic bi-phasic reaction mixture to decompose the dibromocarbene precursor, bromoform, in conjunction with a phase transfer catalyst to facilitate ylide formation and carbene migration to graphene substrates. DBC-functionalized graphene (DBC-graphene) was characterized using a range of spectroscopic and analytical techniques to confirm the covalent nature of functionalization. Modified optical and electronic properties of DBC-graphene were investigated using UV-vis spectroscopy, analysis of electrical I-V transport properties and using non-contact terahertz time-domain spectroscopy (TTDS). The implications of the carbene functionalization of graphene are considered in the context of scalable radical functionalization methodologies for bulk-scale graphene processing and controlled band-gap manipulation of graphene.
The area of terahertz science and applications has grown dramatically in the last 30 years. Instr... more The area of terahertz science and applications has grown dramatically in the last 30 years. Instrumental platforms for THz measurements have also proliferated, and now include laser-based, electronic, opto-electronic, and microwave photonics devices. As the field matured, metrology and standardization have gained focused attention, resulting in an increasing number of publications and a book devoted to the subject. However, these have been primarily focused on photonic-based free-space techniques and their particular demands and issues. This paper presents a brief review of metrology requirements for active THz electronic devices, the available instrumentation, state of the art, and challenges.
ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of... more ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of textiles are shown to have different THz optical properties, which may be employed to combat textile counterfeiting.
A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon a... more A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon absorption peaks with the increase of S content is shown to have complex transformation, which should be considered in the design of dispersion equations for THz applications.
ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are inve... more ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are investigated using THz time-domain spectroscopy, Raman, FTIR and ellipsometry. The optical properties are related to modifications in the crystal structure.
A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. D... more A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. Different types of crystals are shown to have different THz optical properties and anisotropy, which may be employed for THz applications.
Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate g... more Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate glasses. New glass compositions doped with Pr3+-ions were fabricated using controlled atmosphere melting and casting techniques. The optical properties of new bulk glasses were studied by spectruscopic techniques. The significance of an empirically derived total loss curve for bulk glass is examined for the design of a 1.3 µm amplifier. The concentration effects of Pr3+-ions as a dopant in the glass were studied, and its absorption cross-section measured to establish the ground state absorption in bulk glass. The thermal stability of mixed halide glasses was studied by differential scanning calorimetry. and an appraisal of their devitrification behaviour is presented.
Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs an... more Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs and GaSex-1Sx and other nonlinear optical crystals in the FIRand THz regimes using the classic Maker Fringe and Z-scan techniques. The Z-scan measurements were conducted successfully, in both the FIRand THz regimes, and the measurement results in the FIR were found to be in reasonable agreement with the available literature [7, 8, 9]. Wecan conclude that multi-photon absorption in the FIR is no more an impediment to pumping, GaSe based, nonlinear frequency conversiondevices that in the near-IR.
Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host ... more Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host for 1.3µm Pr3+-doped optical fibre amplifier. We report the crystallization behaviour of the mixed halide glasses while reheated above their glass transition temperature. The effect of impurities in the starting raw materials on the quality of the bulk glass is reported. The OH- absorption was monitored by FTIR technique, and related to the lifetime of the 1G4 excited state in Pr3+-doped glass. The thermal stability of the glass was studied from heat treatment data using a differential scanning calorimeter.
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