Fabrication Of Molybdenum Oxides With Localized Surface Plasmon Resonances And Their Applications

The interaction between light and matter is the basis of many fundamental physical and chemical processes.Elaborating universal and trustworthy strategies for efficient light harnessing between dielectric and materials is crucially important for new technologies in energy storage and conversion.And nanomaterials have paved unparalleled opportunities for light management,notably from nanoplasmonics.Plasmons are free-electron oscillations in a conductor under irradiation and such oscillations can be strongly confined to a metal-dielectric interface.On account of these so-called localized surface plasmon resonances?LSPR?,efficient light trapping has been achieved through the on-demand design of plasmonic nanoparticles for the purpose of a variety of application domains ranging from optical metamaterials and metasurfaces,biochemical detection,nanophotonics devices,and energy storage and conversion,etc.However,the use of metals always suffers from the inherent absorption losses,which traditionally limit the possible materials to metals such as gold,silver and copper which have high free electron densities in the range 10²³-10²⁰cm^-3,and at the same time the operating frequencies are always constrained to the range of near-infrared,visible and ultraviolet.In contrast to noble metal,there are some other materials that exhibit tunable plasmonic properties,such as graphene,doped semiconductor and transition metal chalcogenides/oxides.In principle,semiconductor nanostructures are expected to exhibit similar size-and shape-tunability of LSPRs as metals.However,a key advantage of using semiconductors for nanoplasmonics is that their free carrier concentrations can be tuned by doping,temperature,and/or phase transitions,allowing the adjusting of LSPR spectrum of the nanocrystal.Molybdenum oxides can exhibit unique LSPR properties because of their outer-d valence electron.In this thesis,we investigate the tunable LSPR in molybdenum oxides,which have been used in photoelectrocatalysis and bio-sensing.The research contents are shown as follows:?1?SC CO₂-Assisted Fabrication of Heterostructures of MoO₃/MoS₂ for Enhanced Photoelectrocatalytic PerformanceBased on the assistance of SC CO₂,we develop an efficient method to locally pattern h-MoO₃ on the ultrathin metallic 1T-MoS₂ nanosheets and obtain the novel heterostructures of h-MoO₃/1T-MoS₂.The enhanced photoelectrochemical performance of the as-prepared heterostructures has been demonstrated.Our study indicates it is originated from the synergistic effect between h-MoO₃ and 1T-MoS₂,i.e.,the strong plasmonic absorption of h-MoO₃ in the visible and NIR region,the excellent electronic conductivity of 1T-MoS₂ and as well as the efficient separation of the photo-induced carriers from the heterostructures.?2?Synthesis of Amorphous Molybdenum Oxide Nanodots with Tunable Localized Surface Plasmon ResonancesIn this work,we design a simple room-temperature chemical reaction route to synthesize amorphous molybdenum oxide(MoO_3-x)nanodots that exhibit strong localized surface plasmon resonances in the visible and near-infrared region.Moreover,tunable plasmon resonances can be achieved in a wide range with the changing surrounding solvent,and accordingly the photoelectrocatalytic activity can be optimized with the varying LSPR peaks.?3?Fabrication of Amorphous Molybdenum Oxide Nanodots with Tunable Localized Surface Plasmon Resonances for biosensingHere we demonstrated that amorphous molybdenum oxide nanodots obtained via a facile sonochemistry approach,exhibit strong localized surface plasmon resonances?LSPR?in the visible and near infrared region.Through variation of their stoichiometric compositions,tunable plasmon resonances could be observed in a wide range,which hinge upon the solvent in the synthetic process.Additionally,in a bovine serum albumin based optical bio-sensing system,the plasmonic semiconductor dots displays superior sensitivity and unique response.Based on the strong LSPR effect and amorphous structure,the signal of Raman spectroscopy can be significantly enhanced,thus achieving detection of trace amounts of chemical and biological molecules.