Volume 239, Issue 6 - Special Issue: Solar Water Splitting And Artificial Photosynthesis (SWAP), Part 7; Guest Editors: Kevin Bethke, Jeyanthinath Mayandi and Smagul Karazhanov

In this study, Ni-doped ZnO (NZ) and Ni–Mn dual-doped ZnO (NMZ) NPs were synthesized by hydrothermal method. Various analytical techniques, such as XRD, UV–vis, FTIR, PL, SEM, EDAX, and HR-TEM, were employed to investigate the effect of doping transition metal ions in the ZnO lattice. The powder X-ray diffraction (XRD) patterns confirmed a hexagonal structure with average crystallite sizes of 30.66 nm and 27.09 nm for NZ and NMZ nanoparticles, respectively. Tauc’s plot showed that the energy bandgap was redshifted to 2.9 from 2.8 eV by doping transition metal ions in ZnO. The photoluminescence spectrum displayed various peaks, indicating the emission behaviour of the nanomaterials. The photocatalytic performance of the catalysts was tested under visible light sources against Crystal Violet (CV) dye. The degradation efficiency, for NMZ achieved a maximum degradation efficiency of 91.1 %. Antibacterial activity was evaluated against gram-positive ( B. subtilis and S. aureus ) and gram-negative ( E. coli and P. aeruginosa ) bacteria. The NMZ exhibited higher photocatalytic and antibacterial activity than NZ.

This study investigates the photocatalytic efficacy of core–shell CeO 2 /TiO 2 nanocomposite (CT-NC) synthesized via solution combustion synthesis. Various characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV–visible spectroscopy (UV), photoluminescence spectroscopy (PL), Raman spectroscopy, field emission scanning electron microscopy (FESEM) along with energy-dispersive spectroscopy (EDS) analysis and high-resolution transmission electron microscopy with selected area electron diffraction (HRTEM-SAED) were employed to analyze the nanomaterials. XRD pattern confirmed the realization of cubic and tetragonal phases of CeO 2 and TiO 2 . The vibrational modes observed below 800 cm −1 confirmed the metal-oxygen bonds of the synthesized samples. The energy bandgap (E g ) of CT-NC, as estimated from UV–vis spectra, reduced to 2.28 eV, resulting in a significant enhancement of the photocatalytic activity. The various emission peaks in the visible region due to the oxygen vacancies facilitated the generation of Reactive Oxygen Species (ROS). EDS analysis confirmed the presence of elements and the purity of the samples. Furthermore, CT-NC demonstrated remarkable dye degradation efficiency, achieving a maximum efficiency of 98.15 % under visible light irradiation for 120 min. This enhanced activity is attributed to the Advanced Oxidation Process (AOPs). Overall, the results highlight the potential of CT-NC as an efficient photocatalyst for environmental remediation.

Photocatalysis has a significant role in water remediation. During the process of photocatalysis, catalysts face different problems, such as instability and inefficiency. Here, we are introducing a new method, ‘nonlinearity kinetics’, which will help to identify this kind of problem during photocatalytic activity. We are considering Ag 3 PO 4 @TiO 2 to study nonlinear disorder kinetics. Ag 3 PO 4 is a highly photoactive compound with an inherent photocorrossive nature. Here, it addresses the challenge of pure Ag 3 PO 4 by transforming composite materials to Ag 3 PO 4 @TiO 2 and by studying its nonlinear kinetics during photocatalysis. The Ag 3 PO 4 @TiO 2 underwent preliminary characterisation. Increment of crystalline nature studied through XRD. FESEM and TEM analysed morphological alignment and diffraction patterns. The functional behaviour of oxygen, Ag, Ti and P–O–P were identified through the FT-IR spectra. The reduced optical band gap Ag 3 PO 4 @TiO 2 was 2.9 eV Obtained from the UV–visible spectra. Photocatalysis activity was performed, and newly introduced disorder kinetics were observed. The nonlinear fit of the kinetics shows a shift over time (intercept value of linear fit −0.27) that indicates the corrosive characteristics. For an efficient catalyst, this value must be equivalent to zero. The photocorrossive disorder kinetics study demonstrates the disorder and nonlinearity of the catalyst and catalytic medium when it does not fit with a linear fit. To identify a disorder, it is important to look at the disorder kinetics of analysis.

Biodegradable (green) materials have been gained momentous attention and extensively used for environmental restoration as a result of recent environmental legislations. The current study involved treating Pithecellobium dulce seed pod (PSD) powder with acetic acid to look examined the possibility of using treated P. dulce (PD) to remove Reactive Red 195-A from its aqueous solution. The treated material was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), differential thermal analysis (DTA), and thermo gravimetric analysis (TGA). Different constraining factors, such as dye concentration, temperature, contact time, and solution pH, and sorbent dose were examined using batch adsorption trials. Further, the Freundlich and Temkin, alongside the Langmuir equations were employed to analyze the different isotherms. The results showed that Temkin isotherm was found to be validated by the experimental findings on RRD adsorption by the prepared adsorbent. The findings exposed that the adsorbing process tailed pseudo-second order kinetic model, as demonstrated by a correlation coefficient R 2 greater than 0.90. According to thermodynamic investigations, adsorption was endothermic and took place spontaneously. The findings suggested that the seed pod of the PD plant might be a cheaper substitute for the chemical adsorbents used to remove dyes.

The five-membered heterocycle pyrazole has two nitrogen atoms next to each other. Natural items and pharmaceuticals using pyrazole as the nucleus have demonstrated a wide range of biological activity. Medications with pyrazole cores may have better pharmacokinetics and pharmacological effects than medicines with similar heterocyclic rings. This is because the pyrazole core has unique physicochemical properties. In this study, 5-amino-3-(2,5-dimethoxyphenyl)-1-isonicotinoyl-2,3-dihydro-1H-pyrazole-4-carbonitrile is synthesized and characterized by means of spectrum and quantum chemical techniques. Using UV–vis absorption technique, Fourier transform infrared (FT-IR), and Fourier transform Raman (FT-Raman) techniques, the spectroscopic properties were examined. There were two regions visible in the experimental Raman as well as infrared spectra: 4,000–400 cm −1 along with 4,000–100 cm −1 . The ideal molecular shape, vibrational frequencies, infrared intensity levels, and scattering from Raman were all assessed using density functional theory. The 13 C (carbon) and 1 H (proton) chemical shifts of the molecule were determined using nuclear magnetic resonance (NMR). The TD-DFT scheme was utilized to figure out speculative ultraviolet values and compare them to oscillator strength, electron excitation energies, and spectrum data from experiments. It is evident from the predicted HOMO-LUMO band separation energies that the transmission of charge takes place within a molecule’s structure. The chemical reactivity of the molecule has been calculated along with other global descriptive properties. Scientists investigated how charges move and the density of electrons inside a molecule using NBO analysis of the chemical they were studying. After examining the molecular electrostatic potential (MEP), a 3D picture was created that shows the compound’s nucleophilic and electrophilic areas. In addition to meeting all pertinent pharmacokinetic requirements, 5-amino-3-(2,5-dimethoxyphenyl)-1-isonicotinoyl-2,3-dihydro-1H-pyrazole-4-carbonitrile is also readily absorbed by the gastrointestinal system. Additionally, the chemical that was synthesized had a positive interaction with the target proteins of treatments for viruses, asthma, and heart failure, as shown by molecular docking.

In the present study, the structural and electrochemical properties on Ni–CuCo 2 O 4 (0 ≤  x  ≤ 10 %) was studied for the use of active electrode materials in asymmetric supercapacitors prepared by a simple hydrothermal process. The synthesized material’s morphology shows that the nanosheets are assembled with an average diameter of about 50 nm, and the X-ray diffraction results show the spinel cubic structure with the space group of Fd-3mz (No. 227). CuCo 2 O 4 electrodes exhibit a high specific capacitance for the electrodes because of the abundant redox reactions of Co 2+ /Co 3+ and Co 3+ /Co 4+ , and Ni at the Co site has displayed exceptional charge-discharge and cyclic stability properties. The electrochemical studies show that the Ni doped CuCo 2 O 4 electrode has the highest pseudocapacitive nature, with ultra-specific capacitances of 803 F g −1 , 889 F g −1 , 924 F g −1 , and 1,086 F g −1 at 1 A g −1 respectively for pure, 2, 6, and 10 % Ni doped CuCo 2 O 4 electrodes. Further, the excellent rate capability with 82 % capacitance retention and 92.3 % Coulombic efficiency were realized after 1,000 cycles. Moreover, the M-H study at room temperature showed paramagnetic behaviour. Additionally, the electrochemical and magnetic characteristics of the CuCo 2 O 4 system is expected to improve as the doping quantity of Ni increased. This study may pave the way for enhanced properties of Ni doped CuCo 2 O 4 for futuristic hybrid devices applications.

The study focuses on the green synthesis of silver nanoparticles (AgNPs) using Arachis hypogaea L. seed peel extract (AHSPE) and evaluates their photocatalytic activity against Rhodamine B and Congo Red dyes. The synthesis involved reducing aqueous silver metal ions with AHSPE, characterized by various techniques including UV–visible spectroscopy, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and FT-Raman spectroscopy. UV–visible spectroscopy indicated characteristic absorption peaks at 428 and 439 nm, confirming the formation of AgNPs. XRD analysis revealed an average particle size of 4.77–5.6 nm. FT-IR spectra identified biomolecules such as amines, peptides, amides, lactones, and polyphenols in the extract, acting as reducing and capping agents, thereby stabilizing the AgNPs. SEM analysis showed pristine silver nanoparticles with diameters ranging from 1 to 10 µm. The biosynthesized AgNPs demonstrated strong photocatalytic activity in degrading Rhodamine B and Congo Red dyes. This method did not use any synthetic reagents, making it an environmentally safe and cost-effective alternative for synthesizing silver nanoparticles. The process aligns with green chemistry principles, offering potential applications in photocatalysis and environmental cleanup. The study underscores the importance of biosynthesized nanoparticles due to their unique biological properties and the role of plant secondary metabolites in facilitating green synthesis.

Antibacterial agents are essential to maintain the health of living beings. The misuse and overuse of antibiotics have led to the development of resistance against antibiotics in microbes. To address this issue, efficient, cost-effective, and biocompatible alternatives for conventional antibiotics need to be developed. Reduced graphene oxide (rGO), ZnO, and their composite have been identified as being efficient in disinfecting bacterial strains. The synthesis of rGO, ZnO, and their composite is usually a multi-step, time-consuming process that uses harmful reagents and catalysts. In this study, we prepared rGO from sucrose and rGO/ZnO composite from sucrose and zinc acetate by a single-step heating process. The method is green, eco-friendly and only uses commonly available non-hazardous precursors for preparation. The characterisation techniques, XRD, XPS, FE-SEM, and HR-TEM, displayed the formation of rGO and ZnO in the samples. The antibacterial efficiency of the samples rGO, the composites ZG-10, ZG-40, ZG-60 and ZnO (ZG-100) were evaluated against Gram-positive and Gram-negative bacterial strains using the agar disc diffusion method. The samples showed remarkable bactericidal activity against all the tested bacterial strains, and their zone of inhibition was comparable to that of conventional antibiotics. Different samples are proven to be effective for different bacterial strains. The sample rGO was found to be more efficient in inhibiting Escherichia coli with a zone of inhibition of 19.5 mm, whereas the ZG-10 composite exhibited superior efficiency against Pseudomonas aeruginosa with a zone of inhibition of 20.5 mm. The sample ZG-100 showed high disinfection efficiency against Staphylococcus aureus and Salmonella enteritidis with zones of inhibition of 22.8 and 23 mm, respectively. The minimum inhibitory concentration and cytotoxicity of the samples were also tested. From the analysis, the tested samples demonstrate strong antibacterial efficacy and less cytotoxicity, positioning them as a promising material for biomedical applications.

Harnessing solar energy through flat-plate solar water heating systems offers an efficient and sustainable solution for residential water heating needs. This study aims to assess and compare the thermal efficiency of two flat-plate solar water heating systems designed for residential use: one with a heat exchanger and one without. Each system features a flat-plate collector with a dark absorber, a transparent cover to reduce heat losses, and a heat-transport fluid. A thin copper sheet with a selective coating forms the absorber. According to the standards of the Indian Ministry of New and Renewable Energy (MNRE), the evaluation revealed that the system without a heat exchanger achieved a higher efficiency (50 %) compared to the system with a heat exchanger (46 %). This device demonstrated notably lower thermal loss efficiency relative to previous studies, as evidenced by heat loss coefficients of 2.89, 2.66, 1.77, and 2.13 W/m 2  k. Despite the higher efficiency of the system lacking a heat exchanger, the importance of heat exchangers in mitigating issues related to water hardness must be acknowledged. This study offers novel insights into the design and optimization of solar water heating systems, highlighting the trade-offs between efficiency and practical considerations.

Developing a sustainable non-noble hybrid electrocatalyst for effective electrocatalysis is the most crucial task; particularly in sustainable hydrogen energy production in the realm of energy conversion. In this work, effective thermal pyrolysis process followed by phosphorization strategy was employed to prepare and fabricate ZIF-67 (Zeolitic imidazole) assisted Co 2 P/N doped carbon electrocatalyst for hydrogen evolution reaction (HER). The optimized Co 2 P/N–C electrocatalyst exhibited hollow porous nanostructures as confirmed from the scanning electron microscopy. The achieved porous nanostructure improved the efficiency of the charge and mass transportation which is confirmed by the BET analysis, has high surface area value of 94.731 m 2 /g. In addition, a transition metal atom can regulate reactants adsorption and desorption capacity by modulating Co and P electronic configuration. The electrochemical studies of fabricated ZIF-67 derived Co 2 P/N–C electrode were analyzed using 1.0 M alkaline potassium hydroxide (KOH) medium in 3 electrode system process. Whilst, optimizing the pyrolysis temperature during the phosphorization will remarkably enhance the favourable characteristics of the hydrogen generation. Notably, the optimized ZIF-67 derived Co 2 P/NC at 350 °C electrode exhibited low overpotential (135 mV) at minimum 10 mA/cm 2 and low 120.3 mV/dec Tafel slope. Besides, electrode stability at 10 mA/cm 2 current density was verified by chronoamperometry test. Hence, this study furnishes the potential technique for the development of advanced hybrid MOF electrocatalyst as a successful alternative on large scale.