The oxides of copper (CuxO) are fascinating materials due to their remarkable optical, electrical, thermal and magnetic properties. Nanostructuring of CuxO can further enhance the performance of this important functional material and provide it with unique properties that do not exist in its bulk form. Three distinctly different phases of CuxO, mainly CuO, Cu2O and Cu4O3, can be prepared by numerous synthesis techniques including, vapour deposition and liquid phase chemical methods. In this article, we present a review of nanostructured CuxO focusing on their material properties, methods of synthesis and an overview of various applications that have been associated with nanostructured CuxO.

Nanostructured copper oxide semiconductors : a perspective on materials, synthesis methods and applications

In the present study, nano-structured ZnO and Sn-doped ZnO photocatalysts with high sunlight photocatalytic activity were successfully synthesized through the decomposition of zinc acetate and glucose by microwave heating. The prepared ZnO and Sn-doped ZnO photocatalyst were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectrum (PL), UV–vis absorption spectrum (UV–vis), N 2 adsorption and UV–vis diffuse reflectance spectra (DRS). The results showed that the doping greatly changed the microstructure, morphology and optical properties of ZnO, which may contribute to the enhancement of photocatalytic activity. The sunlight photocatalytic activity of the prepared pure ZnO and Sn-doped ZnO photocatalyst was investigated by the degradation of Methylene Blue (MB) solution under sunlight irradiation. Compared with pure ZnO, 13% higher decolorization rate and 29–52% higher mineralization efficiency were obtained by the Sn-doped ZnO. The results indicated that Sn-doped ZnO had a higher photocatalytic activity and Sn dopant greatly increased the photocatalytic activity of ZnO.

Enhanced sunlight photocatalytic performance of Sn-doped ZnO for Methylene Blue degradation

Study of ZnO sol–gel films: Effect of annealing

Sn doping effects on the electro-optical properties of sol gel derived transparent ZnO films

Pure and Al doped ZnO thin films were fabricated on glass substrates by sol-gel method. It is found that all the thin films have a preferential c-axis orientation. With increase of Al doping, the peak position of the (002) plane is shifted to the low 2θ value. A minimum resistivity of 6.2×10~(-4) Ω·cm is obtained for the film doped with 1.5 % Al. However, the resistivity increases with increasing Al concentration. The bandgap is found to broaden with increasing dopant concentration, and it is found that doping with Al has the effect of shifting the optical absorption to the shorter wavelength, which both cases are attributed to the Burstein-Moss shift.

Al-doping effects on structure, electrical and optical properties of c-axis-orientated ZnO:Al thin films

Undoped and doped ZnO thin films were prepared by sol–gel method and deposited on tin-doped indium oxides (ITO) substrate using spin coating technique. The effects of Sn and Sb dopants on structural and optical properties were investigated. The starting material was zinc acetate dihydrate, 2-methoxyethanol was used as solvent and monoethanolamine (MEA) as stabilizer. ZnO films were doped with 2% and 7% Sn and Sb concentrations. Optical measurements show an important effect of Sn and Sb dopants on optical band gap.

Fabrication and characterization of pure and Sn/Sb-doped ZnO thin films deposited by sol–gel method

A cupric oxide (CuO) nanocrystal-doped NaCl single crystal and a pure NaCl single crystal are grown by using the Czochralski (Cz) method. A number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, optical absorption in the UV—visible range, and photoluminescence (PL) spectroscopy are used to characterize the obtained NaCl and NaCl:CuO crystals. It is observed that the average radius of CuO crystallites in NaCl:CuO crystal is about 29.87 nm, as derived from the XRD data analysis. Moreover, FT-IR and Raman spectroscopy results confirm the existence of the monoclinic CuO phase in NaCl crystal. UV—visible absorption measurements indicate that the band gap of the NaCl:CuO crystal is 434 nm (2.85 eV), and it shows a significant amount of blue-shift (ΔEg = 1 eV) in the band gap energy of CuO, which is due to the quantum confinement effect exerted by the CuO nanocrystals. The PL spectrum of the NaCl:CuO shows a broad emission band centred at around 438 nm, which is consistent with the absorption measurement.

http://iopscience.iop.org/article/10.1088/1674-1056/22/9/098103/pdf

Structural and optical properties of a NaCl single crystal doped with CuO nanocrystals

The effect of Sr doping on the structural, optical, morphological and photocatalytic properties of SnO2 thin films prepared by sol–gel dip-coating method was investigated. Thin films of undoped and Sr-doped (8%) SnO2 were deposited on glass substrates and characterized by x-ray diffraction (XRD), Raman spectroscopy, UV–vis absorption and atomic force microscopy (AFM). Sr-doped (8%) SnO2 thin films have exhibited a higher photocatalytic activity with UV irradiation compared to the undoped SnO2 regarding methylene blue dye degradation.

https://iopscience.iop.org/article/10.1088/2053-1591/aa8deb/pdf

Sol–gel synthesis of Sr-doped SnO2 thin films and their photocatalytic properties

Strontium-doped ZnS nanoparticles (NPs) (1.5, 5 and 9 wt%) were synthesized through a surfactant free hydrothermal method. The structural characterization by X-ray diffraction confirms the synthesis of ZnS, with its two crystalline phases (cubic and hexagonal), without apparition of any peaks related to Sr phases. The crystallite size is affected by Sr doping concentration and was estimated in the range of 2.24–2.51 nm. Furthermore, transmission electron microscopy images show that the NPs have great tendency to aggregate into spherical shapes. Spectroscopy analysis revealed vibration modes specific to ZnS materials on the Raman spectra at about 260 and 345 cm
 $$^{-1}$$
 and on Fourier-transform infrared spectra at 668.9 cm
 $$^{-1}$$
 . Electronic investigation performed by UV–Visible diffuse reflectance spectroscopy showed that the synthesized ZnS NPs are optically transparent in the visible domain and their band gap energy decreases from 3.42 to 3.38 eV with increasing Sr concentration. Finally, the methyl orange degradation rate increases with Sr concentration, revealing an improvement in the photocatalytic properties of Sr-doped ZnS NPs.

/pdf/hydrothermal-synthesis-of-strontium-doped-zns-nanoparticles-580pvrw3az.pdf

M. Sebais

Papers

Fabrication and characterization of pure and Sn/Sb-doped ZnO thin films deposited by sol–gel method

Structural and optical properties of a NaCl single crystal doped with CuO nanocrystals

Sol–gel synthesis of Sr-doped SnO2 thin films and their photocatalytic properties

Hydrothermal synthesis of strontium-doped ZnS nanoparticles: structural, electronic and photocatalytic investigations

Study of structural and optical properties of Sb doped ZnO thin films deposited by spin coating method