Defect engineered N-S codoped TiO2 nanoparticles for photocatalytic and optical limiting applications: Experimental and DFT insights.

N-S codoped TiO2 nanoparticles (NPs) were synthesized using a sol-gel cum hydrothermal approach, with ammonium sulfate as the nitrogen and sulfur source compound. The calcination temperature was varied from 500 to 700 °C. The pristine samples exhibited a mixed phase of anatase and brookite, while the doped samples exhibited only the anatase phase, as confirmed by X-ray diffraction (XRD) analysis. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of N-H vibrations and S-O bidentate complexation with Ti4+ ions. Electron paramagnetic resonance (EPR) revealed the presence of Ti3+ signals, confirming the creation of oxygen defects in the doped samples. The absorption and emission properties of the samples were investigated using ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. Vibrating sample magnetometry (VSM) analysis confirms the room-temperature ferromagnetic behavior of the N-S doped TiO2, which was attributed to the presence of oxygen vacancies, as evidenced by the EPR and PL results. The N-S doped TiO2 samples demonstrated superior photocatalytic degradation of Rhodamine B (RhB), Methylene Blue (MB), and Congo Red (CR) dyes under visible light illumination compared to the pristine TiO2. This enhanced performance was attributed to the presence of N and S dopants in TiO2, which create new energy levels within the band structure of TiO2, allowing for efficient absorption of visible light and subsequent generation of reactive species for dye degradation. N-S doping modifies the electronic structure of TiO2, enhancing two-photon absorption (TPA). This increased TPA efficiency suggests promising applications in optical devices, such as laser protection systems and optical limiters. Density Functional Theory (DFT) investigation also confirms that the presence of oxygen vacancies generates energy states below the conduction band. This, in turn, benefits the absorption of more visible light during photocatalytic activities and leads to a notable nonlinear absorption in optical limiting. Overall, the N-S doping strategy significantly improves the photocatalytic and optical limiting performance of TiO2 NPs, making them promising candidates for a wide range of applications.

Impact of Erbium (Er) and Yttrium (Y) doping on BiVO4 crystal structure towards the enhancement of photoelectrochemical water splitting and photocatalytic performance.

An efficient BiVO4nanocatalyst with Erbium (Er) and Yttrium (Y) doping was synthesized via a facile microwave irradiation route and the obtained materials were further characterized through various techniques such as p-XRD, FT-IR, FE-SEM, HR-TEM, UV-Vis DRS, PL, LSV, and EISanalysis. The obtained results revealed that the rare metals induce the stabilization of the monoclinic-tetragonal crystalline structure with a distinct morphology. The yttrium doped BiVO4 (Y-BiVO4) monoclinic-tetragonal exhibited anefficient photoelectrochemical water splitting and photocatalytic performanceare compared to bare BiVO4. TheY-BiVO4 indicated increased results of photocurrent of 0.43 mA/cm2and bare BiVO40.24 mA/cm2. Also, the Y-doped BiVO4 nanocatalyst showed the maximum photocatalytic activity for the degradation of MB, MO, and RhB. A maximum degradation of 93%, 85%, and 91% was achieved for MB, MO, and RhB respectively, within 180 min under the visible light illumination. The photocatalytic decomposition of acetaldehyde also was performed. The improved photoelectrochemical water splitting and photocatalytic activity are due to the narrowing the bandgap, leading to extending the photoabsorption capability and reducing the recombination rate of photoexcited electron-hole pairs through the formation inner energy state of the rare earth metals. The current study disclosed that the synthesis of nanomaterials with crystal modification could be a prospectivecontender forhydrogen energy production as well as to the photocatalytic degradation of organic pollutants.To the best of our knowledge, both photocatalytic and photoelectrochemical studies were never been reported before for this type of material.

Investigation of the structural, optical and crystallographic properties of Bi2WO6/Ag plasmonic hybrids and their photocatalytic and electron transfer characteristics.

Effective exploitation of visible-light unique structural and electronic properties has enormously attracted more researchers for photocatalytic systems. Here, we have fabricated an efficient Bi2WO6-Ag plasmonic hybrid via the photoreduction technique and the obtained materials were well characterized with sophisticated instruments. The BW-Ag-1 catalyst showed the maximum photocatalytic activity for the degradation of cationic dyes rhodamine B (RhB) and malachite green (MG) and the rate constant was 2.6 × 10-2 min-1 and 1.6 × 10-2 min-1 respectively, which is the highest among the synthesized catalysts. The enhanced photocatalytic activity could be ascribed to the synergistic effect of surface plasmon resonance caused by Ag NPs, which could enhance the photoabsorption capability, photon scattering, and plasmon resonance energy transfer, and plasmon-induced hot electron transfer (PHET) ensures better photocatalytic performance. In addition, we have evaluated the influence of Ag on Bi2WO6 microspheres with crystallographic and morphological studies, which depict a negligible change in the crystal structure and an increase in the Ag (FCC) phase with an increase in AgNO3 content and the FE-SEM and mapping images disclose the uniform dispersion of Ag on the surface of Bi2WO6. Trapping experiments revealed that the active species for the degradation of MG were superoxide (˙O2-) radicals as the major reactive species with holes being the main instigative species, which are effectively involved in the photo-induced catalytic reaction. Furthermore, we have studied the effect of different pH of MG initial solution and the plasmonic hybrid catalyst depicted high stability and durability even after five successive cycles. In the electrochemical study, the BW-Ag-1 modified glassy carbon electrode (GCE) demonstrated a superior current density due to the redox behavior and smaller resistance revealing the addition of Ag NPs to be beneficial for the catalytic performance.

A versatile effect of chitosan-silver nanocomposite for surface plasmonic photocatalytic and antibacterial activity.

Chitosan-silver (CS-Ag) nanocomposite was green synthesised without the aid of any external chemical-reducing agents. The synthesised nanocomposite was characterised by UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and zeta potential analyser. The particle size of the synthesised CS-Ag nanocomposite was around 20 nm and was found to be thermally stable in comparison with pure chitosan. The prepared nanocomposite acts as a photocatalyst for dye decolourisation, with a maximum of 81% of methyl orange (MO) decolourisation that occurred under visible light irradiation. The kinetics was found to follow pseudo-first-order according to Langmuir-Hinshelwood (L-H) model. The nanocomposite also proved to be an excellent antimicrobial agent against both Gram-positive and Gram-negative bacteria, possessing a broad spectrum of antimicrobial activity. The zone of inhibition ranged between 16.000 ± 1.000 and 19.333 ± 1.155 (mm), proving its high susceptibility than chitosan itself. The minimum inhibitory concentration (MIC) values were from 8 to 64 µg/mL, whereas the minimum bactericidal concentration (MBC) values ranged from 16 to 128 µg/mL, with the highest antibacterial activity shown against Gram-positive Staphlococcus aureus. This report illustrates the eco-friendly approach for the reduction of silver using chitosan as a reducing agent, and its potential to dye decay and microbial contaminants.

Tetraammine(carbonato-κ(2) O,O')cobalt(III) perchlorate.

In the title complex, [Co(CO3)(NH3)4]ClO4, both the cation and anion lie on a mirror plane. The Co(III) ion is coordinated by two NH3 ligands and a chelating carbonato ligand in the equatorial sites and by two NH3 groups in the axial sites, forming a distorted octa-hedral geometry. In the crystal, N-H⋯O hydrogen bonds connect the anions and cations, forming a three-dimensional network.