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In recent decades, the textile industry has contributed to continuous pollution in the environment. Synthetic dyes which are commonly found in waste water are azo, sulfur, anthraquinone, triphenylmethyl, indigoid, and phthalocyanine derivatives. These pollutants block the light penetration in water bodies and prevent photosynthesis activity, thereby affecting aquatic life. As an environmental crisis, several technologies have been explored to control pollution. Among all the techniques, the photocatalysis process is considered as a green, simple, and economical process. To improve the photocatalytic activity, researchers worldwide have investigated various photocatalysts such as metal oxides, metal ferrites, and heterostructured nanocomposites. The major goal of this review article is to propose a high-performing, cost-effective hybrid photocatalyst reported to date for prospective azo dye pollutant remediation. This review article also aimed to highlight the challenges and uncertainties associated with dye degradation in the photocatalytic process.

In this present work we have studied the physical, structural, thermal, and optical properties of a new set of alkali zinc boro tellurite glasses doped europium trioxide prepared using the melt-quenching method. X-ray diffraction technique (XRD) and SEM were used to determine the non-crystalline property and microstructure property of the prepared samples. By using MAS-NMR spectroscopy and FTIR spectroscopy, the structural changes in the glasses were revealed. The physical properties were described by considering the densities of glass samples and hence molar volume, polaron radius, and oxygen packing density were measured. Thermal stability of glasses was perceived by performing DSC analysis and values ranges from 145 to 190 °C. Using UV–visible absorption spectra, it was possible to calculate the optical properties. The highest refractive index is found as 2.275 for glass AZBTE0 and the lowest is 2.241 for AZBTE5 glass. The ionic behaviour of the glasses was determined by electronegativity and values lie in the range of 1.51 to 1.688. The outcomes of the physical, thermal, and optical characteristics of glasses are intended for potential uses in optical switching and Europium doped fibre amplifier applications.

Developing the high-efficiency photocatalyst of low-cost synthesis is a more important implication in the field of research. Thus versatile applicable nanomaterial need of search leads us to synthesize WO 3 :TiO 2 (1:2 to 1:8) photocatalysts through the ultra-sonication-assisted co-precipitation method for sensing heavy metal ion (lead) and the degradation of reactive blue 4 dye under visible light irradiation. The synthesized material has been confirmed by the characterization techniques such as powder X-ray diffraction (PXRD) & Rietveld Refinement for the crystal size ranges from 8 to 13 nm. Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) for surface morphology and elemental confirmation. The band gap evaluated from Ultra-violet Visible-Diffuse reflectance spectroscopy (UV-DRS) is 3.1–3.4 eV. Having aggregable size, the photocatalyst WO 3 :TiO 2 (1:6) showed better results when compared to other ratios. Electrochemical sensor action for lead ion detection was conducted by graphite assisted with WO 3 :TiO 2 (1:6) electrode paste in 0.1 M KCl electrolyte. Photocatalytic degradation of reactive blue 4 dye was conducted under visible light and achieved 84% degradation. It shows that the better capacitance value of 24.7 × 10 −2 F/g for WO 3 proves to be a better capacitor application. Graphical Abstract

Trivalent erbium ions doped (48 –  x ) AlPO 4  + 15K 2 O + 12MgF + 20Na 2 O + 5NaF +  x Er 2 O 3 glass samples have been prepared utilizing the melt-quench process and studied to understand the efficacy of Er 3+ ions content on physical, structural and luminescence attributes of host glass. The functional groups of the glass structure such as metaphosphate, orthophosphate and pyrophosphate have been elucidated through Fourier Transform Infrared (FTIR) spectroscopic investigation. The least-square approach was used to calculate the Judd–Ofelt parameter from the oscillator strength of the Er 3+ ion transitions. The luminescence emission data captured in the visible and near-infrared (NIR) province using 380 and 980 nm excitation wavelengths. The up-conversion (recorded at the excitation at 980 nm) of 0.5 Er glass exhibited emission at 664, 550 and 488 nm wavelengths. The decay plots of the studied glass specimens were measured at 980 nm excitation. The McCumber (MC) theory has been implemented to calculate the gain coefficient of the 0.5 Er glass and flat gain curve was drawn for S-band, C-band and L-band. The attributes for optical amplification were ascertained, including the quality factor (0.85), branching ratio (1), stimulated emission cross-section (1.3 × 10 –20 cm 2 ), gain bandwidth (1.26 × 10 –25 cm 3 ) and optical gain (0.394 × 10 –23 cm 2  s) for 0.5 Er glass. The yellowish green light emission ability of the 0.5 Er glass after 980 nm excitation evident through CIE co-ordinates position (x 0.36, y 0.58) at 1931 CIE chromaticity diagram. The spectroscopic and luminescence results endorse that the alumino–phosphate glass specimens loaded with 0.5 mol% of Er 2 O 3 are beneficial for NIR and green light emission applications.

Heterojunction nanocomposite based strategies provide proven technology in photo catalysis and inactivating bacteria. This article presents a Green mediated combustion process to generate CuO, Cu 2 O, and metallic Cu (3C) along with doping them with Zirconia. The crystallinity, purity and phase formation of the prepared compounds and the effect of doping were characterized using diffraction peaks of the Powder X-ray diffraction (PXRD). Scanning electron microscopy (SEM) reveals visible agglomeration in the morphology in case of all the compounds and X-ray Photoelectron Spectroscopy (XPS) analysis revealed the doping of Zirconia to be in the form of Zr 2+ and Zr 4+ ions. The band gap energy of the nanoparticles 3C (2.0 eV) and Zr-3C (1.8 eV) decreases, as seen by the UV–visible absorption spectroscopy, demonstrating the dopant Zr increases the degradation process by trapping electrons and holes, which prevents the recombination of e–h + pairs. This illustrates Zr-3C efficiency over 3C as a photocatalyst when exposed to UV- light. The photocatalytic performance of Zr-3C on Rhodamine B (RhB) dye was confirmed by the obtained results. Under 105 min of UV-light exposure, the degradation was determined to be 96.5% and 82.5% for Zr-3C and 3C nanoparticles respectively. Under the dark condition the degradation was ~ 10%. Additionally, the degradation rates obtained for the host 3C and Zr-3C are (K = 0.0216 min −1 ) and K = 0.03367 min −1 respectively. The scavenger study revealed that without adding scavengers 96.2% degradation observed. But degradation was only 60% and 20% after the addition of ammonium oxalate and isopropanol, which proves that holes and hydroxyl radicals were primarily the active species responsible. In addition, the supercapacitor nature of the Zr-3C nanocomposite is confirmed by its significant specific capacitance (87.4 F/g) in cyclic voltamogram analysis and charge discharge experiments with a durability of 1600 cycles. Furthermore, the exceptional antibacterial properties of 3C and Zr-3C nanoparticles were examined against S. aureus and E. coli. Zr-3C samples exhibit increased activity of 18 mm and 17 mm diameter zone of inhibition with increase in concentration against strains of Escherichia coli and Staphylococcus aureus bacteria respectively when compared to host 3C nanoparticle.

Efficacy of silver nanoparticles concentration and annealing durations on optical limiting and optical nonlinearities of borate based glasses bearing the composition (79.5– x )B 2 O 3 –15Na 2 O–5La 2 O 3 –0.5Sm 2 O 3 – x AgCl (mol%) was assessed by Z-scan approach under the pumping of visible light (532 nm) in nanosecond regime. The dual photon absorption parameter (α 2 ) was elevated from 0.576 × 10 −11 to 1.201 × 10 −11  m/W with AgCl content from 0 to 0.5 mol%. This α 2 further raised to 1.964 × 10 −11  m/W when the optimized glass host heat treated at 450° C for 25 h. Similarly, the index of nonlinear refraction (n 2 ) was enhanced from 1.642 × 10 −19 to 2.532 × 10 −19 m 2 /W as the AgCl content increased from 0 to 0.5 mol%. This n 2 value in turn monotonously increased to 2.963 × 10 −19 m 2 /W when optimized glass system annealed at 450° C for 25 h. The optical limiting threshold magnitude followed reverse trend compared to α 2 and n 2 . The enhancement in nonlinear optical features and optical limiting efficiencies were related to field stimulated by Ag 0 nanoparticles when excited with high energy radiation. However, the non-uniform local field generated when the glass nanocomposites heated for longer duration resulted the switching of nonlinear absorption. The nonlinear optical and optical limiting results infer the 0.5 mol% AgCl encompassing glass sample annelaed at 450 °C for 25 h is benificail for construction of power optical limiters to operate in the visible range.

Solution combustion was employed to create a series of ZrO2:Dy3+ (1-11 mol percent) nanoparticles (NPs) using oxalyl dihydrazide (ODH) as the fuel. ZrO2:Dy3+ NPs were subjected to calcination at about 700°C. ZrO2:Dy3+ NPs comprised of 1 to 11 mol% of Dy3+ were characterized by employing the X-ray diffraction (XRD), transmission electron microscopic (TEM), UV-visible, and X-ray photoelectron spectroscopic (XPS) techniques. The crystallite diameters of 1 to 11 mol% ZrO2:Dy3+ NPs were observed to range from 8.1 nm to 16.3 nm, exhibiting spherical shape. According to BET tests, the pore volume of ZrO2:Dy3+ NPs was determined to be 100.129 cm3/g. The mean pore diameter of ZrO2:Dy3+ NPs was determined to be 4.803 nm from the Barrett-Joyner-Halenda (BJH) plot. The photoluminescence and photocatalytic dye degradation properties of ZrO2:Dy3+ NPs were investigated. The acid red 88 (AR88) dye was applied to appraise the photocatalytic activities of the NPs under UV irradiation. ZrO2:Dy3+ NPs with 3 mol% Dy3+ exhibited improvised photocatalytic activity due to the operative departure of charge carriers. The electrochemical examination of ZrO2:Dy3+ NP modified carbon paste electrode in 0.1 N HCl demonstrated considerable redox potential output, as evidenced by cyclic voltammetric and amperometric measurements. The electrochemical sensor studies on ZrO2:Dy3+ NPs exhibited potentiality towards sensing of highly toxic metals like mercury and lead.

The influence of europium (Eu 3+ ) ions on the optical properties of silver lead borate glasses of the x Eu 2 O 3 –(1 – x )Ag 2 O–29PbO–70B 2 O 3 ( x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 mol%) glass system prepared by theconventional melt quenching technique and their physical and optical properties were investigated. The UV absorption spectra were recorded at room temperature in the wavelength range of 200–600 nm. From the absorption edge data, it is found that both the direct and indirect transitions and their values are ranging from 3.19 to 3.54 and 2.50 to 3.07 eV, respectively. The Urbach energy values for these glasses were found to be in the range of 0.39–0.52 eV. The refractive indices have also been evaluated with respect to different molar concentrations of Eu 2 O 3 and their calculated values are ranging from 1.598 to 1.654.

Development of next-generation photonic device necessitates employing vitreous materials with high optical nonlinearities and low optical limiting thresholds. Additionally, the high nonlinear photonic glasses are suitable for nuclear radiation shielding applications. Herein, the borate-based glass specimens bearing significant amounts of heavy metal oxides (Bi.sub.2O.sub.3 and PbO) activated with various quantities of Eu.sub.2O.sub.3 have been explored for optical limiting, nonlinear photonic, and nuclear radiation shielding applications. Efficacy of Eu.sub.2O.sub.3 content on functional features has been assessed and discussed the outcomes in detail. The open aperture Z-scan results unveiled the enhancement in two-photon absorption coefficient and reduction in optical limiting threshold with Eu.sub.2O.sub.3 amount in the glass composition. Further, certain fundamental attenuation factors such as mass attenuation and linear attenuation coefficients were estimated utilizing Phy-X software in the energy ranges between 0.284 and 2.506 MeV. The mass attenuation and the linear attenuation coefficients were found to improve with the inclusion of more and more Eu.sub.2O.sub.3 in the glass compositions. The outcomes of the study clearly revealed that the high Eu.sub.2O.sub.3 activated lanthanum heavy metal borate glasses are productive in optical limiting, nonlinear optical, and gamma radiation shielding strategies to cutoff the high energy electromagnetic and nuclear radiations. The comparative study further validates that the La.sub.2O.sub.3-Bi.sub.2O.sub.3-B.sub.2O.sub.3-Eu.sub.2O.sub.3 glasses are more advantageous than La.sub.2O.sub.3-PbO-B.sub.2O.sub.3-Eu.sub.2O.sub.3 glasses.