Carbon quantum dots (C QDs)/p-type CuAlO2/n-type ZnO photoelectric bilayer film composites were prepared by a simple route, through which ZnO films were sputtered on crystal quartz substrates and CuAlO2 films were prepared by sol–gel on ZnO films and then these bilayer films were composited with C QDs on their surface. The characterization results indicated that C QDs were well combined with the surface of the CuAlO2 films. The photovoltage and photocurrent of these bilayer film composites were investigated under illumination and darkness switching, which demonstrated to be significantly enhanced compared with those of the CuAlO2/ZnO bilayer films. Through analysis, this enhancement of the photoconductivity was mainly attributed to C QDs with unique up-converted photoluminescence behavior.Keywords: carbon quantum dots; photoelectric; p−n junction; transmittance; up-converted photoluminescence;

Carbon quantum dots/TiO2 nanotubes composites were prepared by a simple technical route through which TiO2 nanotubes prepared by electrospinning were dispersed in carbon quantum dots solution, and dried at 80 °C. The results indicated that the TiO2 nanotubes composites were combined with the carbon quantum dots. The photocatalytic activity of the carbon quantum dots/TiO2 nanotubes composites was investigated by the degradation of rhodamine B under visible light irradiation, and it was demonstrated to be significantly enhanced compared with that of pure TiO2 nanotubes. Through analysis, this enhancement of visible light photocatalytic activity was attributed to the carbon quantum dots with the unique up-converted photoluminescence behavior.

Water-soluble, fluorescent carbon dots (CDs) have been successfully synthesized from waste paper. The as-prepared CDs, with an amorphous structure and small particle size, exhibit good photostability, high photoluminescence quantum yields (PLQYs) and fairly low toxicity, which indicate potential applications in the field of biolabelling.

•We fabricated Cd2V2O7 and CdCO3 via a facile method.•We characterized the microstructure and chemical state of the Cd2V2O7 and CdCO3.•We researched the optical property of the Cd2V2O7 and CdCO3.•The Cd2V2O7 and CdCO3 show unique visible light emissions.Cadmium vanadium oxides (Cd2V2O7) and Cadmium carbonates (CdCO3) were synthesized via a facile hydrothermal method. X-ray diffraction (XRD), Raman spectroscopy, infrared spectrometer (IR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the structure, morphology and chemical state of the samples, respectively. The photoluminescence (PL) properties of the as-synthesized Cd2V2O7 and CdCO3 were measured at room temperature using an excitation wavelength of 325 nm. The Cd2V2O7 shows two visible light emission centers located at 589 and 637 nm, which are supposed to be relevant to local defects in Cd2V2O7. The CdCO3 shows three emission centers located at 408, 530 and 708 nm, which are supposed to be relevant to the electron transition from the conduction band to valence band and defect related energy level.Cd2V2O7 and CdCO3 were prepared via a facile hydrothermal method, which show unique visible light emissions ((a) for Cd2V2O7 and (b) for CdCO3).

Highly photoluminescent carbon dots with a PL quantum yield of 9.3% have been prepared via a simple one-step synthesis route using waste paper as a novel carbon source. The as-prepared carbon dots have good water solubility, well distributed particle size and acceptable fluorescence lifetime. Besides, due to high photostability and biocompatibility, the obtained carbon dots are demonstrated as excellent probes in cellular imaging.

Three types of hollow urchinlike α-MnO2 nanostructures, namely, columnar nanorod clusters, tetragonal nanotube clusters, and tetragonal nanorod clusters, have been synthesized through a facile hydrothermal method. The microstructure and morphologies of the resulting materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected-area electron diffraction, and the microwave absorption properties of these nanostructures were investigated in terms of complex permittivity and permeability. The results indicate an obvious magnetic loss in the manganese oxide/paraffin wax composites. The tetragonal nanorod clusters exhibit enhanced microwave absorption properties compared with columnar nanorod clusters and tetragonal nanotube clusters, which result from proper electromagnetic impedance matching. These urchinlike manganese oxide nanostructures are considered to have great potential applications as microwave absorbents.

SiO2 photonic crystal were successfully prepared by vertical deposition and then used as a template to fabricate SiO2-ZnO composite photonic crystals on ITO substrates by electrodeposition and subsequent calcination. A number of different deposition times were used. The morphologies of the silica opals and SiO2-ZnO composite photonic crystals were investigated by scanning electron microscopy. It was found that ZnO particles grew randomly on the surfaces of the silica spheres when the deposition time was short. As the deposition time was increased, the ZnO particles grew evenly on the surfaces of the silica spheres so that the interstitial space of the silica template was filled with ZnO particles. Reflectance spectra of the SiO2-ZnO composite crystals revealed that all of the fabricated photonic crystals exhibit a photonic band gap in the normal direction.

The controlled synthesis of ZnO hierarchical structures has been successfully realized in a large scale via a simple hydrothermal method. It was demonstrated that the morphology of the final products was simply tuned by adding different amounts of soluble salt. ZnO microparticles were prepared when no soluble salt was added, whereas microspheres and nanoflowers were selectively prepared in the presence of different amounts of NaF. ZnO nanosheets were obtained when adding appropriate amount of NaCl, Na2SO4, or K2SO4. ZnO nanobelts were obtained in the presence of appropriate amount of sodium citrate (C6H5Na3O7). The photoluminescence (PL) properties of those products were researched, and the origin of the PL was discussed.

The electrochromic (EC) NiOxHy films were fabricated through a facile sol–gel method. The formation of high quality NiOxHy films came from adding the xerogel back into the sol and prolonging the annealing time at gradually increasing temperature up to 250 °C. Scanning electron microscopy and atomic force microscopy characterizations indicated films were compact, homogenous, and smooth. Glance angle X-ray diffraction investigation testified NiOxHy films were of poor crystallization. The Fourier transform infrared, and thermogravimetry and differential thermal analysis showed that films contained the mixture of NiO, Ni(OH)2, NiOOH, water, and organic substance. With the increasing of the xerogel ratio, the optical absorbance and reflectance of films had larger differences between the colored and bleached state, respectively. The film with the xerogel ratio of 1:5 showed excellent EC properties with a transmittance contrast as high as 60.88% at λ = 560 nm, which was higher than other sol–gel nickel oxide films reported.

Transparent conducting oxides CdIn2O4 thin films were prepared by radio-frequency reactive sputtering from a Cd–In alloy target in Ar+O2 atmosphere. By transmission spectrum and Hall measurement for different samples prepared at different substrate temperatures, it could be found that the carrier concentration would increase with the decrease of substrate temperature, but absorption edge showed an abrupt variation from a blue shift to a red shift. Theoretically, the paper formulated the effect of high-density point defects on band structures; it embodied the formation of band tailing, Burstein-Moss shift and band-gap narrowing. The density of holes will influence the magnitude of optical band gap and transmittance of light. Since extrapolation method does not fit degenerate semiconductor materials, a more accurate method of obtaining optical band gap is curve fitting. In addition, ionized impurities scattering is the main damping mechanism of the free electrons in CdIn2O4 films, the density of ionized impurities induced by altering substrate temperature will affect the carriers mobility.

Carbon quantum dots/TiO2 nanotubes composites were prepared by a simple technical route through which TiO2 nanotubes prepared by electrospinning were dispersed in carbon quantum dots solution, and dried at 80 °C. The results indicated that the TiO2 nanotubes composites were combined with the carbon quantum dots. The photocatalytic activity of the carbon quantum dots/TiO2 nanotubes composites was investigated by the degradation of rhodamine B under visible light irradiation, and it was demonstrated to be significantly enhanced compared with that of pure TiO2 nanotubes. Through analysis, this enhancement of visible light photocatalytic activity was attributed to the carbon quantum dots with the unique up-converted photoluminescence behavior.