Unconventional photoelectron spectroscopic studies : PES of some transient species and reactive molecules

A fast pumping, versatile photoelectron spectrometer suitable for the study of transient species and reactive molecules has been designed, constructed and tested. The photoelectron spectra of seventeen such compounds (CS, SO, S₂O, HN=NH, DN=MD, CH₃N = NH, HCP, OCSe, SCSe, CSe₂> O₃, FNO, CINO, BrNO, HMO₃, C1MO₂ and FNO₂) have been obtained. The individual spectra have been assigned by using information supplied from vibrational analysis, by comparison with molecular orbital calculations and with related molecules. The experimental Franck-Condon factors have been utilized to estimate the geometries of the ionic states, and the procedure has been found to be quite reliable. The study has shown the potential of photoelectron spectroscopy in providing information on the electronic structure of transient species and reactive molecules, information that is difficult to obtain by other spectroscopic techniques.Science, Faculty ofChemistry, Department ofGraduat

Preparation of novel cuprous oxide-fullerene[60] core-shell nanowires and nanoparticles via a copper(I)-assisted fullerene-polymerization reaction

A copper(I) (Cu(I))-assisted fullerene (C-60)-polymerization method has been developed for the seamless coating on nanosized objects of cuprous oxide (Cu2O), forming novel Cu2O-C-60 core-shell nanostructures. It is based on a reaction Of C-60 and ethyl isocyanoacetate to form polymerized fulleropyrolines, catalyzed by and thus coated on the Cu2O nanomaterials. Cu2O nanoribbons and nanocubes were used in this work to demonstrate the nanocoating method. The Cu2O-C-60 core-shell nanostructures were characterized comprehensively, revealing a uniform, covalently polymerized C-60 shell that closely sheaths the Cu2O nanostructures. Details of the Cu(I)-assisted C-60-Polymerization process are proposed, which combines the solution chemistry and surface chemistry Of C-60. The Cu2O cores in the composite nanocubes could be removed, yielding monodispersed C-60 nanoboxes. Preliminary measurements demonstrated enhanced photocurrent of the Cu2O-C-60 nanoribbons arrayed on Cu foil compared to that of the Cu2O nanoribbons

Upconversion and Downconversion Fluorescent Graphene Quantum Dots: Ultrasonic Preparation and Photocatalysis

A facile ultrasonic route for the fabrication of graphene quantum dots (GQDs) with upconverted emission is presented. The as-prepared GQDs exhibit an excitation-independent downconversion and upconversion photoluminescent (PL) behavior, and the complex photocatalysts (rutile TiO₂/GQD and anatase TiO₂/GQD systems) were designed to harness the visible spectrum of sunlight. It is interesting that the photocatalytic rate of the rutile TiO₂/GQD complex system is <i>ca.</i> 9 times larger than that of the anatase TiO₂/GQD complex under visible light (λ > 420 nm) irradiation in the degradation of methylene blue

Coupling surface plasmon resonance of gold nanoparticles with slow-photon-effect of TiO2 photonic crystals for synergistically enhanced photoelectrochemical water splitting

The slow photon effect of a photonic crystal (PC) is a promising characteristic for tuning light-matter interactions through material structure designing. A TiO2 bi-layer structure photoanode was constructed by fabricating a TiO2 PC layer through a template-assisted sol-gel process on a TiO2 nanorod array (NR) layer. Gold nanoparticles (Au NPs) with an average size of about 10 nm were deposited in situ into the TiO2 bi-layer structure. The extended photoelectrochemical (PEC) water splitting activity in visible light was ascribed to the energetic hot electrons and holes that were generated in the Au NPs through the excitation and decay of surface plasmons. By alternating the characteristic pore size of the TiO2 PC layer, the slow photon region at the red edge of the photonic band gap could be purposely tuned to overlap with the strong localized surface plasmon resonance (SPR) region of Au NPs. The matching slow photon effect of TiO2 PC (with a characteristic pore size of 250 nm) intensified the SPR responses (central at 536 nm) of Au NPs. Consequently, more hot electrons were generated in the Au NPs and injected into the conduction band of TiO2, resulting in improved PEC water splitting efficiency in the visible light region. Under simulated sunlight illumination, the photoconversion efficiency of the well matching Au/TiO2 photoanode approached 0.71%, which is one of the highest values ever reported in Au/TiO2 PEC systems. The work reported here provides support for designing coupling plasmonic nanostructures with PC-based materials to synergistically enhance PEC water splitting efficiency

Selective Growth of Dual-Color-Emitting Heterogeneous Microdumbbells Composed of Organic Charge-Transfer Complexes

We report a simple yet versatile solution route for constructing heterojunctions from luminescent organic charge-transfer (CT) complexes through a two-step seeded-growth method. Using this method, we achieved anisotropic and selective growth of anthracene–1,2,4,5-tetracyanobenzene (TCNB) complexes onto the tips of naphthalene–TCNB microtubes, resulting in the formation of microdumbbells. Significantly, the two-component microdumbbells appear as dual-color-emitting heterojunctions arising from integration of two distinct color-emitting materials. We further elucidated the two-step seeded-growth mechanism of the dumbbell-like organic heterostructures on the basis of structural analysis of the two crystals and surface–interface energy balance. In principle, the present synthetic route may be used to fabricate a wide range of sophisticated dual- or multicolor-emitting organic heterostructures via judicious choice of the CT complexes