Fluorotellurite glass codoped with erbium and ytterbium was elaborated through the melting-quenching route. Through the DSC and Raman measurements, the investigated glass samples presented high thermal stability and low phonon energy, respectively. By using the laser excitation at 488 nm, the downconversion mechanism in the Er³⁺/Yb³⁺ system was investigated and the energy transfers implicated in the emissions of erbium and ytterbium ions were discussed based on the different cross-relaxation processes. The addition of ytterbium resulted in an effective energy transfer from the excited ⁴S_3/2/²H_11/2 state of Er³⁺ ions to the emitting ²F_5/2 state of Yb³⁺ ion, which considerably enhanced NIR emissions at 1000 nm and reduced experimental lifetimes of  ⁴S_3/2/²H_11/2 states. Through luminescence decay analysis, the maximum values of quantum efficiency (η_QE) and energy transfer efficiency (η_ET) were estimated as 61.2% and 161.2%, respectively. This result indicates that the proposed glasses can convert visible photons into NIR emissions at 1000 nm suitable to improve the spectral response of crystalline silicon PV cells.

The size and density of nanopits, generated at the surface of their top layer, strongly affect the electrical and optical properties of AlGaN-based structures. Therefore, the control of the layer quality evolution as a function of the nanopits size/density is a crucial issue to enhance the device performance. In this paper, the effects of the nanopits diameter observed at the surface of AlGaN on carrier dynamics are systematically investigated. The variation of nanopits diam-eter is achieved through thermal annealing of a set of AlGaN/GaN heterostructures at different temperatures. The samples are characterized using the scanning electron microscope (SEM), energy-dispersive x-ray, high-resolution x-ray diffraction, photoluminescence (PL), and time-resolved PL spectroscopies. SEM images have revealed an increase in the nanopits diameter with increasing annealing temperature. In addition, we observed a linear development in the yellow luminescence intensity, accompanied by a deterioration in the PL decay times due to an increase in the density of point-defect complexes that act as nonradiative recombination centers. We also performed temperature-dependent PL measurements to study the impact of the nanopits diameter on electron–phonon scattering processes. Both electron-acoustic- and electron-longitudinal optical phonon interactions enhance with increasing nanopits diameter.

Copper indium sulfide (CIS), zinc sulfide (ZnS) and CIS/ZnS nano-adsorbents (NAs) encapsulated with mercaptopropionic acid (MPA) were synthesized and characterized with different techniques, and finally tested for the adsorption/photodegradation of methyl blue dye (MB) in aqueous solution under UV irradiation. Structural and optical properties of the nanocrystals were determined via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscopic, UV–Visible and photoluminescence spectroscopy. CIS/ZnS showed a specific surface area of 24.06 cm² g⁻¹ and an adsorption capacity of 27.71 mg g⁻¹ for MB. MB adsorption kinetic was found to follow the pseudo-second order kinetic model and the Langmuir-Freundlich model was the best model to describe the adsorption isotherms. Taking into account the statistical physics analysis and the theoretical meaning of the parameters, the Hill model with one activation energy presented the best prediction of the experimental data, indicating that MB dye adsorption occurred by the formation of a monolayer and that MB interaction with CIS/ZnS were characterized by only one activation energy. The calculated adsorption energy varied from 19.38 to 20.04 kJ mol⁻¹ suggesting that the adsorption occurred via physical interactions via a multimolecular adsorption process. The photodegradation activity of the core–shell NAs under UV irradiation showed better efficiency than the bare core and Shell NAs thus indicating that ZnS recovery improved the degradation power of the CIS nano-adsorbents (97 %). In summary, these eco-friendly NAs are highly promising materials for efficient wastewater treatment to face water pollution caused by organic compounds via adsorption and photodegradation processes.

We report the microstructure, optical properties and high photocatalytic performance, with correlations between them, of coprecipitated and post-annealed ZnO nanoparticles. The obtained ZnO single phase after post annealing at different temperatures (200–600 °C) was identified by X-ray diffraction (XRD) and its morphology was investigated by transmission electron microscopy (TEM). The TEM results indicate a gradual growth of the spherical-like nanoparticles to nanorod-like shapes by post annealing with common nanorods shape by annealing at 600 °C. XRD Rietveld refinements indicated that the global structure parameters such as lattice constants, bond lengths, and oxygen position are slightly affected by the post annealing. While the crystallite size and number of unit cells per a particle gradually increase, the dislocation density, micro-strain and residual stress gradually decrease by the post annealing with a further change at annealing temperature of 500 °C, indicating correlations to the particles shape. Based on optical absorbance measurements, it was found that the optical energy gap gradually decreases from 3.22 to 2.89 eV by increasing the annealing temperature up to 600 °C. After a period up to 90 min of irradiation, photo-catalytic efficiency of up to 95 % was observed in the photo-degradation of methylene blue. In addition, the nanoparticles annealed at low temperature showed better performance in the photo-degradation of methylene blue. The observed high photocatalytic performance is discussed in correlation to the microstructure and optical properties of the investigated samples.

Sol-gel spin coating technique was used to develop Zn and Ag co-doped CdO thin films with 3.0 wt% Zn and various Ag doping concentrations. A cubic structure and a preferred orientation along (111) growth plane of samples was confirmed from films diffractograms analysis. The crystallites sizes of the samples were calculated and found about ∼33–44 nm. A further investigation of the structural phase of the films was carried out using Raman spectroscopy. The elemental composition of the films was examined using EDX technique which confirmed the presence of all elements. The collected EDX mapping spectra revealed a successful Zn and Ag co-doping of CdO films with a uniform elemental distribution. A controlled tailoring of the optical band gap of the film was achieved via Zn and Ag co-doping of CdO films. The band gaps of films were obtained from the Uv–vis absorbance spectra and were found to be in the order ∼1.87–2.32 eV. A significant improvement in nonlinear optical parameters was observed for the Zn doped CdO matrix with high Ag doping concentrations where χ⁽³⁾ was estimated to be about 5.52 × 10⁻¹²-4.16 × 10⁻¹² esu and (n₂) ∼1.84 × 10⁻¹¹-1.51 × 10⁻¹⁰ esu; respectively. On the other hand, Hall measurements of the grown films revealed interesting improvements in the carrier concentrations and conductivity. Films I–V characteristics show an ohmic contact with enhanced conducting behavior which suggests that the developed co-doped CdO films are promising for optoelectronics applications.

Studying the linear and non-linear optical properties is critical in terms of technological application, as it aids in developing the semiconducting materials for optoelectronic applications. Consequently, the present studies report the investigation of the influence of thermal annealing on the structural, morphology, linear, and non-linear optical properties of Ge₁₀Se₇₈Ag₁₂ thin films. X-ray diffraction analysis confirmed the amorphous state of Ge₁₀Se₇₈Ag₁₂ composition. The studied composition was annealed at a temperature between the glass transition and crystallization, and the annealing temperature T_an affected the number and intensity of crystalline phases. Some peaks disappeared at 383 K, indicating that this temperature represents a transition in the structure of the studied materials. The morphological changes caused by the thermal treatment were observed by the scanning electron microscopy (SEM). On the other hand, the linear and non-linear optical constants varied with T_an. The band gap was found to decrease from 1.70 to 1.43 eV and then increase to 1.91 eV with increasing the temperature from 363 to 573 K, confirming the presence of structural transition at 383 K. The optical and electrical conductivities were determined and found to vary with the temperature. The present results were analyzed and discussed.

Pure CdO nanostructured thin films and Ag doped with 1.0, 2.0 and 4.0 wt% doping concentrations were fabricated successfully on glass substrates with a cost-effective spin coating technique. The prepared films exhibit a cubic crystal structure oriented along (111) plane. The surface morphology of the pure CdO films shows a cauliflower shape structure, becomes granular, and compact at high Ag doping concentration. Raman spectra of the films reveal LO (longitudinal optical) and TO (transverse optical) vibration modes at 406.80 cm⁻¹ and 566.54 cm⁻¹. The absorption of the films significantly varies with Ag doping concentrations and as a result, the electronic structure of the films is tailored. Moreover, the optical band gaps vary in the range of 1.42–1.70 eV. In addition, the optical parameters n, k were studied in correlation with Ag doping concentrations. The obtained room temperature photoluminescence spectra of the prepared films show a broad peak at ∼350 nm. The third order nonlinear optical parameters of the films were also examined systematically.

Cd and Na co-doped ZnO nanostructured thin films with different doping concentrations were prepared using a sol-gel spin coating technique on glass substrates. The effect of doping with Cd and 1, 2 and 3 wt % Na on the structural, morphological, optical and UV detection properties of the nanostructured ZnO thin films was investigated. The grown co-doped nanostructured thin films exhibit wurtzite structure with preferential growth along the (002) plane. The change in the doping concentration was found to have a considerable effect on the grain size of the prepared films as well as their morphology. A variation in the band gap of the co-doped nanostructured thin films was also observed with changing the doping concentration. The band gap was found to vary in the range from 3.27 to 3.24 eV with increasing Na concentrations. The UV detection performance of the co-doped ZnO nanostructured thin films based UV detector was also investigated and found to strongly depend on the dopants concentrations with an obvious correlation with the variation in the films band gap. The findings of the current study show that a good control of the optical properties and the UV detection performance of the ZnO nanostructured thin films can be achieved through co-doing with Cd and Na with increased potential for their uses in high performance opto-electronic devices.

Zinc sulfide (ZnS) nanoparticles were fabricated using the chemical precipitation method. The X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) techniques were used to investigate the structural parameters of the formed ZnS. The hexagonal crystal structure of the Zn and ZnS phases was formed. The average crystallite size of the ZnS phase is 10.3 nm, which is much smaller than that of the Zn phase (54.5 nm). Several frequencies and phonon modes were detected in the Raman scattering spectrum belonging to the ZnS nanoparticles. The synthesized ZnS nanoparticles were used as catalysts to eliminate the Congo red (CR) dye, with different concentrations, from synthetic wastewater. The impact of the CR dye concentration and shaking period on the adsorption of CR was thoroughly investigated, and various adsorption kinetic models were tested. After 3 h of shaking, the adsorption efficiency reached 26.01% for 40 mg/L CR dye and 27.84% for 20 mg/L CR dye. The adsorption capacities of the CR dye in the presence of ZnS are 16% and 9% for 40 and 20 mg/L, respectively. Based on the correlation factor, the intraparticle diffusion kinetic model was considered the best of the tested models.