Photoacoustic Spectroscopy of Titanium Dioxide, Niobium Pentoxide, Titanium:Niobium, and Ruthenium-Modified Oxides Synthesized Using Sol-Gel Methodology.

The aim of this work was the development and morphological/chemical, spectroscopic, and structural characterization of titanium dioxide, niobium pentoxide, and titanium:niobium (Ti:Nb) oxides, as well as materials modified with ruthenium (Ru) with the purpose of providing improvement in photoactivation capacity with visible sunlight radiation. The new materials synthesized using the sol-gel methodology were characterized using the following techniques: scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), photoacoustic spectroscopy (PAS), and X-ray diffraction (XRD). The SEM-EDS analyses showed the high purity of the bases, and the modified samples showed the adsorption of ruthenium on the surface with the crystals' formation and visible agglomerates for higher calcination temperature. The nondestructive characterization of PAS in the ultraviolet visible region suggested that increasing calcination temperature promoted changes in chemical structures and an apparent decrease in gap energy. The separation of superimposed absorption bands referring to charge transfers from the ligand to the metal and the nanodomains of the transition metals suggested the possible absorption centers present at the absorption threshold of the analyzed oxides. Through the XRD analysis, the formation of stable phases such as T-Nb16.8O42, o-Nb12O29, and rutile was observed at a lower temperature level, suggesting pore induction and an increase in surface area for the oxides studied, at a calcination temperature below that expected by the related literature. In addition, the synthesis with a higher temperature level altered the previously existing morphologies of the Ti:Nb, base and modified with Ru, forming the new mixed crystallographic phases Ti2Nb10O29 and TiNb2O7, respectively. As several semiconductor oxide applications aim to reduce costs with photoexcitation under visible light, the modified Ti:Ru oxide calcined at a temperature of 800 °C and synthesized according to the sol-gel methodology used in this work is suggested as the optimum preparation point. This study presented the formation of a stable crystallographic phase (rutile), a significant decrease in gap energy (2.01 eV), and a visible absorption threshold (620 nm).

Structural, Optical and Dielectric Properties of Some Nanocomposites Derived from Copper Oxide Nanoparticles Embedded in Poly(vinylpyrrolidone) Matrix.

Polymer nanocomposite films based on poly(vinyl pyrrolidone) incorporated with different amounts of copper oxide (CuO) nanoparticles were prepared by the solution casting technique. The PVP/CuO nanocomposites were analyzed by X-ray diffractometry (XRD), scanning electron microscopy, UV-Visible absorption spectroscopy and dielectric spectroscopy. The XRD analysis showed that the monoclinic structure of cupric oxide was maintained in the PVP host matrix. The key optical parameters, such as optical energy gap Eg, Urbach energy EU, absorption coefficient and refractive index, were estimated based on the UV-Vis data. The optical characteristics of the nanocomposite films revealed that their transmittance and absorption were influenced by the addition of CuO nanoparticles in the PVP matrix. Incorporation of CuO nanoparticles into the PVP matrix led to a significant decrease in band gap energy and an increase in the refractive index. The dielectric and electrical behaviors of the PVP/CuO nanocomposites were analyzed over a frequency range between 10 Hz and 1 MHz. The effect of CuO loading on the dielectric parameters (dielectric constant and dielectric loss) of the metal oxide nanocomposites was also discussed.

The coupled WO3-AgBr nanocatalyst, part II: Synthesis, characterization, and the boosted photocatalytic activity towards metronidazole in an aqueous solution.

The AgBr and WO3 nanoparticles (NPs) were synthesized and coupled, and the coupled AgBr-WO3 binary catalyst, as well as the individual AgBr and WO3 NPs, were then characterized by XRD, FTIR, DRS, and SEM-EDX. XRD results showed the formation of orthorhombic WO3 cubic AgBr crystals. The crystallite sizes of 45, 28, and 45 nm were estimated by the Scherrer formula for the as-prepared AgBr, WO3, and AgBr-WO3 catalysts, respectively. The DRS study estimated band gap energies using both absorption edge wavelengths and the Kubelka-Munk model. The band gap energies of 2.72, 3.06, and 2.92 eV were obtained for the direct electronic transitions of AgBr, WO3, and AgBr-WO3. The ECB (potential position) of AgBr and WO3 were estimated to be 0.01 and 0.52 V, while their EVB values were 2.60 and 3.55 V, respectively. Typical FTIR absorption bands of W‒OH, the W‒O‒W, and AgBr bonds have appeared at 1637 cm-1, 823 (and 766) cm-1, and 1384 cm-1, respectively. The pHpzc of 4 was estimated for the individual and coupled catalysts. In studying the photocatalytic activity of the catalysts in the photodegradation of metronidazole (MNZ) a boosted activity was achieved for the coupled system. This increased activity depends on the maximum AgBr:WO3 mole ratio in a 1:3 mol ratio. Grinding time applied to prepare the coupled catalyst has also varied the photocatalytic activity.

Effect of silver doping on the band gap tuning of tungsten oxide thin films for optoelectronic applications.

In the cutting-edge world, semiconductor metal oxides usually tend to have a high optical band gap (>3.0 eV), significantly acceptable for potential optoelectronic applications. The present study discusses the synthesize of pristine tungsten trioxide (WO3) and Silver (Ag) doped WO3 (Ag: WO3) thin films onto a glass substrate at 450 °C, with varying concentrations of Ag doping (2, 4, 6, 8 and 10 at.%) using a simple Spray Pyrolysis Technique. Field emission scanning electron microscopy (FESEM) analysis showed the presence of particles in the WO3 and Ag: WO3 materials. The X-ray diffraction (XRD) pattern confirmed that the samples' hexagonal structure remained intact. In addition, Rietveld refinement was used for the samples to study the crystal structure meticulously. Because of the surface plasmon resonance effect, the samples' distinguishing characteristics were visible in their optical nature. For pristine WO3, the experimental band gap was determined to be 3.20 eV, and for varying doping concentrations, it was found to be 3.15 eV-2.90 eV, respectively. Furthermore, the fracture has remained imperceptible at elevated concentrations, resulting in a substantial influence on the optical characteristics of 10% Ag: WO3 thin films. The estimated redox potential for 2% Ag: WO3 shows a considerable influence of the band edge potential of the Conduction Band (CB) and Valance Band (VB). The activation energy was determined using temperature-dependent electrical resistivity and exhibited an ohmic nature. The synthesized material exhibited a negative temperature coefficient (NTC) effect at higher concentrations of doping, suggesting its potential applicability as a thermistor. A comprehensive analysis of this present study indicates that Ag can be a viable candidate for doping on WO3 thin films for use in optoelectronic devices.

Band Gap and Polarization Tuning of Ion-Doped XNbO3 (X = Li, K, Na, Ag) for Photovoltaic and Energy Storage Applications.

Using a microscopic model and Green's function theory, we have calculated the band gap energy and the polarization of LiNbO3, KNbO3, AgNbO3, and NaNbO3. The effects by substitution of different ions at A or/and B sites for doping concentration x = 0-0.1 are studied. The observed different tuning of these properties is discussed for the possibility of photovoltaic and energy storage applications of these compounds. They should have a large polarization and narrow band gap. It is shown that the band gap of all substances decreases or increases with increasing Fe or Zn dopant at the Nb site, respectively. But the substitution, for example, of Ba at the A site, leads to different behaviors of these materials. The polarization increases by Ba doping at the A site and decreases by Fe doping at the Nb site. For example, by Ba/Fe, Ba/Ni co-doping (Ba at the A site and Fe, Ni at the B site) we observe both an enhanced polarization and reduced band gap.

One-pot synthesis, structural investigation, antitumor activity and molecular docking approach of two decavanadate compounds.

Two bases-decavanadates coordination compounds [(C6H13N4)2][Mg(H2O)6]2[O28V10].6H2O (1) and [(C7H11N2)4][Mg(H2O)6][O28V10].4H2O (2) have been synthesized and well characterized using vibrational spectroscopy (infrared), UV-Visible analysis and single crystal X-ray diffraction technique. The formula unit, for both compounds, is composed by the decavanadate [V10O28]6-, hydrated magnesium ion, a counter anion and free water molecules. The transition metal adopts octahedral geometries in both compound (1) and (2). The existence of a multitude of hydrogen bonding interactions for both compounds provides a stable three-dimensional supramolecular structure. Optical absorption reveals a band gap energy indicating the semi-conductive nature of the compound. In this study, the cytotoxic and the anti-proliferative activities of compounds (1) and (2) on human cancer cells (U87 and MDA-MB-231) were investigated. Both compounds demonstrated dose-dependent anti-proliferative activity on U87 and MDA-MB-231 with respective IC50 values of 0.82 and 0.31 µM and 1.4 and 1.75 µM. These data provide evidence on the potential anticancer activity of [(C6H13N4)2][Mg(H2O)6]2[O28V10].6H2O and [(C7H11N2)4][Mg(H2O)2][O28V10].4H2O. Molecular docking of the compounds was also examined. Molecular docking studies were performed for both compounds against four target receptors and revealed better binding affinity with these targets in comparison to Cisplatin. Moreover, molecular docking investigations suggest that these compounds may function as potential inhibitors of proteins in brain and breast cells, exhibiting greater efficiency compared to Cisplatin.

Enhanced thermal conductivity of plasma generated ZnO-MgO based hybrid nanofluids: An experimental study.

Hybrid nanofluids (HNFs) of metallic oxide-based nanoparticles (NPs) have been prepared in different basefluids (BFs) employing the thermal plasma technique. NPs of ZnO-MgO were directly dispersed into pristine coolant, engine oil, distilled water (DW), and coconut oil. Plasma was generated between two identical electrodes applying 8.0 kV at the ambient conditions and proved economically viable in preparing stable HNFs. X-ray Diffractometry (XRD) showed ZnO and MgO NPs possessed hexagonal and cubic crystal structures, respectively. The band gap is calculated through UV-visible spectroscopy. The thermal conductivity (TC) of the HNFs has been measured using a thermal conductivity analyzer based on the transient hot wire method. The band gaps of pristine coolant and its HNFs were obtained to be 3.35 eV and 3.33 eV, respectively. In engine oil and its HNFs, band gaps of 3.16 eV and 3.02 eV have been extracted. There appears to be a slight reduction in band gap for coolant and engine oil-based HNFs. The band gap value of coconut oil-based HNFs was 4.05 eV, which showed a higher value than the pristine coconut oil-based HNFs (3.95 eV). The band gap calculated in the case of DW-based HNFs was 3.79 eV. TC of HNFs with volume concentration of 0.019 % for DW, 0.020 % for coolant, 0.016 % for engine oil, and 0.017 % for coconut oil were tested between 20 and 60 °C. An increase in TC was observed with the rise in temperature of the HNFs. Maximum increment in TC was observed at 60 °C for coolant-based HNFs, which was 19 %, followed by DW (18%), coconut oil (18%), and engine oil (16%), respectively. DW-based HNFs can be used as a coolant and optical filter for optoelectronics devices like photovoltaic cells for better performance. The study underscores precise control of NPs size as pivotal for band gap influence. HNFs hold promise as the next-gen heat transfer fluids (HTFs), revolutionizing thermal conductivity across industries. This research lays a firm foundation for plasma-synthesized HNFs' application in enhanced heat transfer and optoelectronic devices. Coolant-based HNFs excel in thermal conductivity, addressing heat transfer challenges.

Effect of Ag and Ni-Doped Cerium Oxide Nanoparticles on the Formation of ROS and Evaluation as an Alternative Physical Sunscreen Material.

CeO2 nanoparticles (nanoceria) were proposed as an alternative physical sunscreen agent with antioxidant properties and comparable UV absorption performance. Green synthesis of nanoceria with Ag and Ni dopants resulted in doped nanoceria with lower catalytic activity and biologically-safe characteristics. The doped nanoceria was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Rancimat Instrument, and UV-Vis Spectrophotometer for SPF (Sun Protection Factor) determination. XRD and TEM analysis showed that nanoceria had been successfully formed in nanoscale-sized with a change in crystallite size due to the crystal defect phenomenon caused by dopant addition. While the Rancimat test and band gap energy analysis were conducted to evaluate the oxidative stability and reactive oxygen species formation, it was confirmed that dopant addition could decrease catalytic activity of material, resulting in Ni-doped Ce with a longer incubation time (11.81 h) than Ag-doped Ce (10.58 h) and non-doped Ce (10.30 h). In-vitro SPF value was measured using the thin layer technique of sunscreen prototype with Virgin Coconut Oil (VCO)-based emulsion, which yielded 10.862 and 5.728 SPF values for 10% Ag-doped Ce and 10% Ni-doped Ce, respectively. The dopant addition of nanoceria could reduce catalytic activity and give a decent in vitro UV-shielding performance test; thus, Ag and Ni-doped nanoceria could be seen as promising candidates for alternative physical sunscreen agents.

Nanolayered Structures and Nanohybrids Based on a Ternary System Co/Ti/Zn for Production of Photo-Active Nanocomposites and Purification of Water Using Light.

Water pollution has emerged as a major challenge for the scientific community because of the rapid expansion of the population and the industrial sector in the world. The current study focuses on introducing a new track for designing new optical nanocomposites for purifying water in addition to providing a new additive for building new nanohybrids. These targets were achieved through building a ternary system of Co/Ti/Zn nanocomposites and nanolayered structures. The Co/Ti/Zn nanolayered structures were prepared and intercalated by different kinds of organic acids: monocarboxylic and dicarboxylic acids. Long chains of organic acids were used to construct series of organic-inorganic nanohybrids. X-ray diffraction, thermal analyses, Fourier Transform Infrared spectroscopy, and scanning electron microscopy confirmed the formation of nanolayered structures and nanohybrids. The optical properties of the nanolayered structure showed that the Co/Ti/Zn LDH became photo-active compared with the usual Al/Zn LDH because of the reduction in the band gap energy from 5.3 eV to 3.3 eV. After thermal treatment, a highly photo-active nanocomposite was produced through observing more reduction for the band gap energy to become 2.8 eV. In addition, the dye of Acid Green 1 completely decomposed and converted to water and carbon dioxide during 17 min of UV radiation by the dual Co/Ti-doped zinc oxide nanocomposite. In addition, the kinetic study confirmed that the high optical activity of the dual Co/Ti-doped zinc oxide nanocomposite accelerated the degradation of the green dyes. Finally, from these results it could be concluded that designing effective nanocomposite for purification of water was accomplished through converting 2D nanolayered structures to a 3D porous structure of Ni/Ti/Zn nanocomposites. In addition, a new additive was achieved for heterostructured hybrids through building new Co/Ti/Zn/organic nanohybrids.