Animes Kumar Golder

A four-coordinate Zn(II) complex (1) containing two ligand-based radicals was synthesized by reacting ligand H4Sar(AP/AP) with Zn(ClO4)2·6H2O, and the complex was structurally characterized by X-ray single crystal measurement. The variable-temperature magnetic susceptibility measurement in solid and magnetic moment analysis at 298 K in solution using the Evans method revealed that in the complex, the radical-based unpaired electrons remained uncoupled in solution, while intramolecular antiferromagnetic coupling was realized in the solid state, leading to a diamagnetic ground state. The ligand-based unpaired electrons underwent two one-electron oxidations and two one-electron reductions in the potential range of 0.10 to −1.20 V vs. Fc/Fc+. To leverage ligand-based electron-transfer processes for CO2 reduction, the complex was coated on a graphite electrode surface using Nafion-117, and electrocatalytic CO2 reduction was carried out within the potential range of −0.79 to −1.39 V vs RHE in 0.5 M KHCO3 aqueous solution. This provided value-added C1 (CH3OH and HCOO–) and C2 (CH3COO–, CH3CHO, and CH3CH2OH) products with moderate FE (30–41%), while continuous electrocatalysis at −0.79 V for 8 h rendered mainly CH3CH2OH. Thus, without the involvement of metal-based redox processes and using only the ligand-based electron-transfer events of complex 1, electrocatalytic CO2 reduction was achieved and reported.

Ciprofloxacin (CIP) is commonly found in wastewater, posing challenges for biological treatment systems due to its persistence and inhibitory effects on microbial communities. This study examined the impact and fate of CIP on granular sludge in removing chemical oxygen demand (COD), ammonia-nitrogen (NH4+), and total phosphate (TP) under different redox conditions, as well as the degradation mechanisms of CIP. Results indicated that CIP impacts COD, ammonium and phosphorus removal by granular sludge in a dose-dependent manner. In aerobic conditions, COD removal by granular sludge was strongly inhibited (45-54% COD removal at 15 mg/L CIP) at higher CIP concentrations. Conversely, COD removal was at 66-62% in the presence of 15 mg/L CIP under anaerobic conditions, indicating lower impact of CIP. Ammonium and phosphate removals were higher under aerobic conditions as compared to anaerobic conditions, both impacted by CIP dosing. CIP removal by granular sludge was noticed under both aerobic and anaerobic conditions and at different initial CIP concentrations. CIP removal was highest at 85% under aerobic condition as compared to 60% under anaerobic condition for an applied 1 mg/L CIP dose. LC-MS analysis identified distinct biodegradation pathways with formation of 23 and 26 intermediates, respectively, under aerobic and anaerobic conditions. These findings highlight the importance of biosorption and biodegradation in CIP removal, and negative effects of CIP on COD and nutrient removal by granular sludge under different redox environments, offering insights for optimizing wastewater treatment strategies.

The energy demand is steadily rising, while the availability of natural energy sources is gradually decreasing. The extensive use of these natural energy resources has significantly harmed the environment and human health by increasing carbon emissions. Thus, a system is needed that can mitigate energy demand while remaining environmentally friendly. In this note, the redox flow battery has emerged as a promising candidate. The efficiency of a redox flow battery depends heavily on the performance of the catholyte and anolyte, i.e., their redox potentials and stability. To investigate the reversible redox cycle of a metal ion-coordinated 2-iminosemiquinone radical for the development of a catholyte for a redox-flow battery, a Ni(II)-monoradical complex (1) was synthesized by reacting redox-active H2Rich(AP)N3 ligand with NiCl26H2O. The existence of the 2-iminosemiquinone radical in the complex was warranted by the X-ray single-crystal diffraction study and X-band EPR spectrum analysis. The complex was found to exhibit two oxidation waves and a reduction wave. The first reversible oxidation at 0.465 V vs. Ag/AgCl (Fc/Fc+ = 0.443 V vs. Ag/AgCl), and the second quasi-reversible oxidation at 1.168 V vs. Ag/AgCl were investigated in a 1:4 CH3CN:CH2Cl2 solvent mixture by galvanostatic charge-discharge (GCD) measurements in the potential range of 0 to 1.0 and 0 to 1.70 V vs. Ag/AgCl, respectively, in a static H-cell. A columbic efficiency (CE) of 89% and an energy efficiency (EE) of 80% for the first one-electron oxidation with 72 hours of running time were achieved. For the two successive one-electron oxidations, CE of 90% and EE of 40% were attained, confirming the applicability of complex 1 as a catholyte

Converting CO₂ into valuable fuels through photocatalysis offers a sustainable strategy to address the energy shortage and decrease greenhouse gas emissions. This work studied bio-based Z-scheme SnO₂/CdS heterojunction photocatalysts (5.7 nm, 120.6 m² g^-1; conduction band: -0.96 V) synthesized using analytes found in Aegle marmelos via microwave irradiation for efficient CO₂ reduction into value-added chemicals. The heterojunction demonstrates a notably higher CO₂ adsorption ability (0.4 mmol g^-1) and photocurrent response (0.74 μA cm^-2) than both CdS QDs(bio) and SnO₂(bio). It also improves charge carrier dynamics, as evidenced by 60 and 56.1% reductions in PL intensity and 48.9 and 59.2% increases in charge carrier lifetime, respectively. The Fermi level difference between CdS (-4.51 eV) and SnO₂ (-5.52 eV) creates an internal electric field that promotes charge separation and transport, inhibits recombination, and protects CdS QDs(bio) from photocorrosion (SO₄^2-). Density functional theory analysis reveals that SnO₂ incorporation into CdS reduces the bandgap (2.38 → 2.15 eV), introduces additional electronic states near the Fermi level (E_F), and shifts the conduction band density of states closer to the E_F compared to CdS QDs, indicating a higher density of active states that enhance interfacial charge transfer. The optimized 0.50SnO₂/CdS QDs(bio) heterostructure exhibits outstanding photocatalytic activity for CO₂ reduction, achieving methanol and hydrogen production rates of 675.9/139.5 μmol g^-1 h^-1 (apparent quantum yields of 3.51 and 0.24%) while maintaining its structural and morphological stability.