Effect of different catalysts and growth temperature on the photoluminescence properties of zinc silicate nanostructures grown via vapor-liquid-solid method

We explore the photoluminescence properties of zinc silicate(Zn_(2)SiO_(4)) nanostructures synthesized by vapor-liquidsolid(VLS)mode of growth using three different catalysts(Sn,Ag,and Mn).Different catalysts significantly influence the growth rate which in turn has an impact on the structure and hence the photoluminescence of the prepared zinc silicate nanostructures.Zn_(2)SiO_(4) has a wide bandgap of about 5.5 eV and in its pure form,it does not emit in visible region due to its inner shell electronic transitions between the 3 d5 energy levels.However,the incorporation of different catalysts(Sn,Ag and Mn)at different growth temperatures into the Zn_(2)SiO_(4) crystal growth kinetics provides wide visible spectral range of photoluminescence(PL)emissions.PL analysis shows broad multi-band spectrum in the visible region and distinct colors(red,yellow,green,blue,cyan and violet)are obtained depending on the crystalline structure of the prepared nanostructures.The allowed transitions due to the effect of different catalysts on zinc silicate lattice offer a huge cross-section of absorption that generates strong photoluminescence.The correlation between the structural and optical properties of the synthesized nanostructures is discussed in detail.The synthesized photoluminescent nanostructures have potential applications in solidstate lighting and display devices.

Photoanode Activity of ZnO Nanotube Based Dye-Sensitized Solar Cells

Vertical ZnO nanotube (ZNT) arrays were synthesized onto an indium doped tin oxide (ITO) glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron microscopy (SEM) showed formation of well-faceted hexagonal ZNT arrays spreading uniformly over a largearea. X-ray diffraction (XRD) of ZNT layer showed substantially higher intensity for the (0002) diffractionpeak, indicating that the ZnO crystallites were well aligned with their c-axis. Profilometer measurements ofthe ZNT layer showed an average thickness of ～7 μm. Diameter size distribution (DSD) analysis showedthat ZNTs exhibited a narrow diameter size distribution in the range of 65–120 nm and centered at ～75nm. The photoluminescence (PL) spectrum measurement showed violet and blue luminescence peaks thatwere centered at 410 and 480 nm, respectively, indicating the presence of internal defects. Ultra-violet (UV)spectroscopy showed major absorbance peak at ～348 nm, exhibiting an increase in energy gap value of 3.4 eV.By employing the formed ZNTs as the photo-anode for a dye-sensitized solar cell (DSSC), a full-sun conversion efficiency of 1.01% was achieved with a fill factor of 54%. Quantum efficiency studies showed the maximumof incident photon-to-electron conversion efficiency in a visible region located at 520–550 nm range.

Why the hydrothermal fluorinated method can improve photocatalytic activity of carbon nitride

Carbon nitride(CN) photocatalysts have attracted much attention due to their excellent photocatalytic properties.And hydrothermal fluorination is a common method to improve the photocatalytic effect of CN photocatalyst.Here,the influence of the band gap was first revealed of fluorination and hydroxylation of CN photocatalyst based on the first theoretical principle.Here,the effect of fluorination and hydroxylation on the CN band gap was discussed for the first time using the first theoretical principle.With F atoms and OH doping,the band gap of CN was significantly improved,conduction band and valence band moved up.Then,F-CN photocatalyst with F atoms and OH was successfully synthesized by a hydrothermal fluorinated method.Next,the reasons why F-CN photocatalyst was more effective than that of traditional CN photocatalyst were fully discussed.From the photocatalytic effect of photocatalyst(12,593.2 μmolg^(-1) h^(-1)to the morphology(super-small nanosheets),structure(homojunctions),composition(metal-free),specific surface area(54.1 m^(2)/g),visible light absorption response(AQE is10.9% at 420 nm) and photo-induced carrier life(14.13 ns).Therefore,this work has a great guiding effect on the development of CN photocatalyst.

Fabrication of titania thin film with composite nanostructure and its ability to photodegrade rhodamine B in water

A titania nanorod filmwas synthesized by direct oxidation of metallic Ti with hydrogen peroxide solution under a low temperature.Titania nanoparticles were then filled into the gaps among the nanorods through an infiltration sol-gel procedure to form a composite titania film with an ordered nanostructure.X-ray diffraction spectra indicate that the composite film was a mixture of anatase and rutile while the titania film obtained by only using a sol-gel procedure was pure anatase.Field emission scanning electron microscopy observations show that titania nanoparticles were embedded into the titania nanorod film.Photoluminescence spectra suggest the enhanced separation of electron and hole pairs for the obtained composite titania film over the corresponding titania nanorod film.The composite titania film exhibited improved ability to photodegrade rhodamine B in water compared with the titania nanorod film.The apparent photodegradation rate constant,fitting a pseudo-first-order,was 3 times of that obtained by the sol-gel derived titania film at the same weight.The improved photocata-lytic activity for the composite titania film could be attributed to the enhanced separation of electron and hole pairs due to the embedding of the titania nanoparticles within the titania nanorods.

Effects on the emission discrepancy between two-dimensional Sn-based and Pb-based perovskites

Two-dimensional (2D) Sn-based perovskites are a kind of non-toxic environment-friendly emission material with low photoluminescence quantum yields (PLQYs) and enhanced emission linewidths compared to that of 2D Pb-based perovskites.However,there is no work systematically elucidating the reasons for the differences in the emission properties.We fabricate (BA)_(2)SnI_(4)and (BA)_(2)PbI_(4)having different defect densities and different exciton-phonon scattering intensities.We also reveal that 2D Sn-based perovskites have stronger exciton-phonon scattering intensity and higher defects density,significantly broadening the emission linewidth and accelerating the exciton relaxation process,which significantly reduces the PLQY of 2D Sn-based perovskites.