Visible-light induced effective and sustainable remediation of nitro organics pollutants using Pd-doped ZnO nanocatalyst.

Nitroaromatic compounds represent a class of highly toxic pollutants discharged into aquatic environments by various industrial activities, posing significant threats to ecological integrity and human health due to their persistent and hazardous nature. In this study, Pd-doped ZnO nanoparticles were investigated as a potential solution for the degradation of nitro organics, offering heightened photocatalytic efficacy and prolonged stability. The synthesis of Pd-doped ZnO NPs was achieved via the hydrothermal method, with subsequent analysis through XRD spectra and XPS confirming successful Pd doping within the ZnO matrix. Characterization through FESEM and HRTEM unveiled the heterogeneous morphologies of both undoped and Pd-doped ZnO nanoparticles. Additionally, UV-vis and PL spectroscopy provided insights into the optical properties, chemical bonding, and defect structures of the synthesized Pd-doped ZnO NPs. Pd doping induces a redshift in ZnO's absorption spectra, reducing the bandgap from 3.12 to 2.94 eV as Pd concentration rises from 0 to 0.2 wt.%. The photocatalytic degradation, following pseudo-first-order kinetics, achieved 90% nitrobenzene abatement (200 µg/L, pH 7) under visible light within 320 min with a catalyst loading of 16 µg/mL. The photocatalytic efficacy of 0.08 wt% Pd-doped ZnO (k = 0.058 min⁻1) exhibited a 25-fold enhancement compared to bare ZnO (k = 3.1 × 10-4 min-1). Subsequent quenching and ESR experiments identified hydroxyl radicals (OH•) as the predominant active species in the degradation mechanism. Mass spectrometry analysis unveiled potential breakdown intermediates, illuminating a plausible degradation pathway. The investigated Pd-doped ZnO nanoparticles demonstrated reusability for up to five successive treatment cycles, offering a sustainable solution to nitro organics contamination challenges.

Enhanced Visible-Light Photodetection with Undoped and Doped ZnO Thin-Film Self-Powered Photodetectors.

Photodetection plays an essential role in the visible-light zone and is important in modern science and technology owing to its potential applications in various fields. Fabrication of a stable photodetector remains a challenge for researchers. We demonstrated a high-response/recovery and self-powered undoped ZnO (UZO) and Cu-doped ZnO (CZO) thin film-based visible-light photodetector fabricated on a cost-effective Si substrate using reactive cosputtering. The structural, morphological, and optical properties of CZO and UZO thin films have been examined using X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and photoluminescence spectroscopy. The results of the CZO/n-Si photodetector compared with those of the undoped ZnO (UZO)/n-Si photodetector show that the CZO/n-Si exhibits a higher on/off ratio, responsivity, and detectivity than UZO/n-Si. Also, the CZO/n-Si photodetector shows high stability and reproducibility over 20 cycles after 180 days. A relative study of CZO/n-Si- and UZO/n-Si-based photodetectors reveals the enhanced performance of the CZO/n-Si photodetector, which has a high on/off ratio of ∼300 with a high specific detectivity of 2.8 × 1010 Jones for 75 mW visible light. The prepared self-powered CZO/n-Si/Ag thin film-based visible-light photodetector paves the way for the development of high-performance photodetector designs.

Surface functionalized silver-doped ZnO nanocatalyst: a sustainable cooperative catalytic, photocatalytic and antibacterial platform for waste treatment.

The different dyes used and discharged in industrial settings and microbial pathogenic issues have raised serious concerns about the content of bodies of water and the impact that dyes and microbes have on the environment and human health. Efficient treatment of contaminated water is thus a major challenge that is of great interest to researchers around the world. In the present work, we have fabricated functionalized silver-doped ZnO nanoparticles (Ag-doped ZnO NPs) via a hydrothermal method for wastewater treatment. X-ray photoelectron spectroscopy analysis confirmed the doping of Ag with ZnO NPs, and X-ray diffractometry analysis showed a decreasing trend in the crystallite size of the synthesized ZnO NPs with increased Ag concentration. Field emission scanning electron microscopy study of pure ZnO NPs and Ag-doped ZnO NPs revealed nanocrystal aggregates with mixed morphologies, such as hexagonal and rod-shaped structures. Distribution of Ag on the ZnO lattice is confirmed by high-resolution transmission electron microscopy analysis. ZnO NPs with 4 wt% Ag doping showed a maximum degradation of ∼95% in 1.5 h of malachite green dye (80 mg L-1) under visible light and ∼85% in 4 h under dark conditions. Up to five successive treatment cycles using the 4 wt% Ag-doped ZnO NP nanocatalyst confirmed its reusability, as it was still capable of degrading ∼86% and 82% of the dye under visible light and dark conditions, respectively. This limits the risk of nanotoxicity and aids the cost-effectiveness of the overall treatment process. The synthesized NPs showed antibacterial activity in a dose-dependent manner. The zone of inhibition of the Ag-doped ZnO NPs was higher than that of the pure ZnO NPs for all doping content. The studied Ag-doped ZnO NPs thus offer a significant eco-friendly route for the effective treatment of water contaminated with synthetic dyes and fecal bacterial load.

Ocimum sanctum Leaf Extract-Assisted Green Synthesis of Pd-Doped CuO Nanoparticles for Highly Sensitive and Selective NO2 Gas Sensors.

In view of facile, cost-effective, and environmentally friendly synthetic methods, palladium-doped copper oxide (Pd-CuO) nanoparticles have been synthesized from Ocimum sanctum (commonly known as "Tulsi") phytoextract for gas-sensing applications. The structural, morphological, and compositional properties of Pd-doped CuO nanoparticles were studied using various techniques such as XRD, FESEM, XPS, and EDX. The characterization results confirmed the doping of Pd on CuO nanoparticles, and Pd-CuO nanostructures appear as nanoflakes in FESEM analysis. The gas-sensing response of Pd (1.12 wt %)-CuO nanoflake-based sensor was measured at 5-100 ppm concentration of different gases, NO2, H2S, NH3, and H2, at 125 °C. Gas-sensing tests reveal that the sensitivity of the sensor were 81.7 and 38.9% for 100 and 5 ppm concentrations of NO2, respectively, which was significantly greater than that of pure CuO. The response and recovery times of the sensor were 72 and 98 s for 100 ppm of NO2 gas, while they were 90 and 50 s for 5 ppm NO2. The calculated limit of detection (LOD) value of the sensor is 0.8235. This appealing LOD is suitable for real-time gas detection. The gas sensor was found to exhibit excellent selectivity toward NO2 gas and repeatability and stability in humid (80%) conditions. The Pd doping in CuO nanostructures plays a significant role in escalating the sensitivity and selectivity of CuO-based NO2 gas sensor suitable to work at low operating temperatures.

Bioinspired palladium-doped manganese oxide nanocorns: a remarkable antimicrobial agent targeting phyto/animal pathogens.

Microbial pathogens are known for causing great environmental stress, owing to which emerging challenges like lack of eco-friendly remediation measures, development of drug-resistant and mutational microbial strains, etc., warrants novel and green routes as a stepping stone to serve such concerns sustainably. In the present study, palladium (Pd) doped manganese (II, III) oxide (Mn3O4) nanoparticles (NPs) were synthesized using an aqueous Syzygium aromaticum bud (ASAB) extract. Preliminary phytochemical analysis of ASAB extract indicates the presence of polyphenolics such as phenols, alkaloids, and flavonoids that can act as potential capping agents in NPs synthesis, which was later confirmed in FTIR analysis of pure and Pd-doped Mn3O4 NPs. XRD, Raman, and XPS analyses confirmed the Pd doping in Mn3O4 NPs. FESEM and HRTEM study reveals the mixed morphologies dominated by nanocorns appearance. Zeta potential investigation reveals high stability of the synthesized NPs in colloidal solutions. The developed Pd-doped Mn3O4 NPs were tested against two fungal phytopathogens, i.e., Sclerotinia sclerotiorum and Colletotrichum gloeosporioides, known for causing great economic losses in yield and quality of different plant species. The antifungal activity of synthesized Pd-doped Mn3O4 NPs displayed a dose-dependent response with a maximum of ~92%, and ~72% inhibition was recorded against S. sclerotiorum and C. gloeosporioides, respectively, at 1000 ppm concentration. However, C. gloeosporioides demonstrated higher sensitivity to Pd-doped Mn3O4 NPs upto 500 ppm) treatment than S. sclerotiorum. The prepared NPs also showed significant antibacterial activity against Enterococcus faecalis. The Pd-doped Mn3O4 NPs were effective even at low treatment doses, i.e., 50-100 ppm, with the highest Zone of inhibition obtained at 1000 ppm concentration. Our findings provide a novel, eco-benign, and cost-effective approach for formulating a nanomaterial composition offering multifaceted utilities as an effective antimicrobial agent.

A convenient first aid kit for chemical and biological agents and for radiation exposure.

The chemical and biological warfare agents are extremely toxic in nature. They act rapidly even in very small quantities and death may occur in minutes. Hence, physical and medical protection must be provided immediately to save life or avoid serious injury. A first aid kit has thus been developed for providing immediate relief from chemical and biological warfare agents (FAKCBW) with the objective of easy detection, personal decontamination, antidote for chemical warfare agents (like nerve agents, sulphur mustard, phosgene, cyanide, radiation exposure and bacterial agents), along with basic medication aid for pain, fever and inflammation. The kit box also includes a user friendly handbook with a simple standard operating procedure. In addition, the kit is rugged to withstand normal jerks, vibration and is water-proof.

Nanostructured metal oxide semiconductor-based sensors for greenhouse gas detection: progress and challenges.

Climate change and global warming have been two massive concerns for the scientific community during the last few decades. Anthropogenic emissions of greenhouse gases (GHGs) have greatly amplified the level of greenhouse gases in the Earth's atmosphere which results in the gradual heating of the atmosphere. The precise measurement and reliable quantification of GHGs emission in the environment are of the utmost priority for the study of climate change. The detection of GHGs such as carbon dioxide, methane, nitrous oxide and ozone is the first and foremost step in finding the solution to manage and reduce the concentration of these gases in the Earth's atmosphere. The nanostructured metal oxide semiconductor (NMOS) based technologies for sensing GHGs emission have been found most reliable and accurate. Owing to their fascinating structural and morphological properties metal oxide semiconductors become an important class of materials for GHGs emission sensing technology. In this review article, the current concentration of GHGs in the Earth's environment, dominant sources of anthropogenic emissions of these gases and consequently their possible impacts on human life have been described briefly. Further, the different available technologies for GHG sensors along with their principle of operation have been largely discussed. The advantages and disadvantages of each sensor technology have also been highlighted. In particular, this article presents a comprehensive study on the development of various NMOS-based GHGs sensors and their performance analysis in order to establish a strong detection technology for the anthropogenic GHGs. In the last, the scope for improved sensitivity, selectivity and response time for these sensors, their future trends and outlook for researchers are suggested in the conclusion of this article.

Impregnated silica nanoparticles for the reactive removal of sulphur mustard from solutions.

High surface area (887.3m(2)/g) silica nanoparticles were synthesized using aerogel route and thereafter, characterized by N(2)-Brunauer-Emmet-Teller (BET), SEM and TEM techniques. The data indicated the formation of nanoparticles of silica in the size range of 24-75 nm with mesoporous characteristics. Later, these were impregnated with reactive chemicals such as N-chloro compounds, oxaziridines, polyoxometalates, etc., which have already been proven to be effective against sulphur mustard (HD). Thus, developed novel mesoporous reactive sorbents were tested for their self-decontaminating feature by conducting studies on kinetics of adsorptive removal of HD from solution. Trichloroisocyanuric acid impregnated silica nanoparticles (10%, w/w)-based system was found to be the best with least half-life value (t(1/2)=2.8 min) among prepared systems to remove and detoxify HD into nontoxic degradation products. Hydrolysis, dehydrohalogenation and oxidation reactions were found to be the route of degradation of HD over prepared sorbents. The study also inferred that 10% loading of impregnants over high surface area and low density silica nanoparticles enhances the rate of reaction kinetics and seems to be useful in the field of heterogeneous reaction kinetics.

Biodegradation of phenol in batch culture by pure and mixed strains of Paenibacillus sp. and Bacillus cereus.

The bacterial strains, Paenibacillus sp. (AY952466) and Bacillus cereus (DQ002384), have proven capacity to degrade lignin and pentachlorophenol. In the present study, both strains were screened at different concentrations of phenol on mineral salt agar medium in the presence of glucose. At optimized condition (pH 7.5 +/- 0.2, 37 +/- 1 degrees C, 120 rpm, 1% glucose w/v), it was observed that both Paenibacillus sp., B. cereus and its mixed culture degraded phenol (500 mg/l) up to 53.86%, 91.63% and 67.76% within 168 h of incubation, respectively. Phenol degradation was routinely monitored spectrophotometrically and further confirmed by HPLC. Catechol and 2-hydroxy muconic semialdehyde were identified as intermediate products from degraded samples using GC-MS. It was also observed that, in the absence of glucose, bacterial strains were unable to utilize phenol indicating the phenomenon of co-metabolism.

Bacterial Compatibility/Toxicity of Biogenic Silica (b-SiO2) Nanoparticles Synthesized from Biomass Rice Husk Ash.

Biogenic silica (b-SiO2) nanopowders from rice husk ash (RHA) were prepared by chemical method and their bacterial compatibility/toxicity was analyzed. The X-ray diffractometry (XRD) patterns of the b-SiO2 nanopowders indicated an amorphous feature due to the absence of any sharp peaks. Micrographs of the b-SiO2 revealed that sticky RHA synthesized SiO2 nanopowder (S1) had clustered spherical nanoparticles (70 nm diameter), while b-SiO2 nanopowder synthesized from red RHA (S2) and b-SiO2 nanopowder synthesized from brown RHA (S3) were purely spherical (20 nm and 10 nm diameter, respectively). Compared to the S1 (11.36 m2g-1) and S2 (234.93 m2g-1) nanopowders, the S3 nanopowders showed the highest surface area (280.16 m2g-1) due to the small particle size and high porosity. The core level of the X-ray photoelectron spectroscopy (XPS) spectra showed that Si was constituted by two components, Si 2p (102.2 eV) and Si 2s (153.8 eV), while Oxygen 1s was observed at 531.8 eV, confirming the formation of SiO2. The anti-bacterial activity of the b-SiO2 nanopowders was investigated using both gram-positive (Escherichia coli) and gram-negative (Staphylococcus aureus) microorganisms. Compared to S2 and S3 silica nanopowders, S1 demonstrated enhanced antibacterial activity. This study signifies the medical, biomedical, clinical, and biological importance and application of RHA-mediated synthesized b-SiO2.

Synthesis and characterization of metal ion imprinted nano-porous polymer for the selective recognition of copper.

Selective recognition of metal ions utilizing metal ion-imprinted polymers (MIIPs) received much importance in diverse fields owing to their high selectivity for the target metal ions. In the present study, a copper ion imprinted polymer was synthesized without an additional complexing ligand or complex with a broad aim to avoid the conventional extra metal ion complexing ligand during the synthesis of MIIP. The complete removal of the copper metal ion from the MIIP was confirmed by AAS and SEM-EDX. SEM image of the MIIP exhibited nano-patterns and it was also found to be entirely different from that of non-imprinted polymer and polymer with copper metal ions. BET surface area analysis revealed more surface area (47.96 m(2)/g) for the Cu(II)-MIIP than non-imprinted control polymer (41.43 m(2)/g). TGA result of polymer with copper metal ion indicated more char yield (18.41%) when compared to non-imprinted control polymer (8.3%) and Cu(II)-MIIP (less than 1%). FTIR study confirmed the complexation between Cu(II)-MIIP and Cu(II) metal ion through carbonyl oxygen of acryl amide. The Cu(II)-MIIP exhibited an imprinting efficiency of 2.0 and it was showing 8% interference from a mixture of Zn, Ni and Co ions. A potentiometric ion selective electrode devised with Cu(II)-MIIP showed more potential response for Cu(II) ion than that was fabricated from non-imprinted polymer.

A rapid field detection method for arsenic in drinking water.

In this study, a rapid colorimetric method for arsenic detection was developed. Different reagents containing magnesium turnings in combination with a series of acids were tested for arsine generation. The arsine was then allowed to react with auric chloride on Whatman filter paper No. 3, which in turn changed color. The detection time and detection limit were measured for each acid. Oxalic acid was found to be the most appropriate acid among all the acids used for detection in this study. It took 10 min to detect 10 ppb arsenic concentration and only 1 min to detect concentrations higher than 50 ppb. This method thus reduced the detection time for arsenic and has the potential to develop better field kit.

Breakthrough behavior of diethyl sulphide vapor on active carbon systems.

Breakthrough behavior of diethyl sulphide vapors on carbon systems such as active carbon, NaOH/CrO3/C, NaOH/CrO3/EDA/C and RuCl3/C has been studied by using modified Wheeler equation and the same was used to calculate the pseudo-first-order rate constant (kv) and kinetic saturation of capacity (W(e)) values. Effects of various parameters such as bed height, air flow rate, concentration and temperature on the above parameters have also been studied. Rate constant was found to be increasing with air flow rate, while W(e) was found to be invariable. Both kv and W(e) decreased with the increase in temperature, however, no significant effect on W(e) and kv was observed due to concentration change. The values of kinetic saturation capacity were used to predict the service lives/breakthrough times of carbon beds (when used in filtration systems).

Sulphur mustard vapor breakthrough behaviour on reactive carbon systems.

Breakthrough behaviour of sulphur mustard, the deadliest of persistent chemical warfare agents, on carbon systems such as NaOH/CrO(3)/C, NaOH/CrO(3)/EDA/C and RuCl(3)/C has been studied and the data were compared with that of active carbon. Effects of bed lengths of carbons on breakthrough time have also been correlated. Thereafter, the effects of flow rate of air-sulphur mustard mixture, concentration and temperature on the kinetic parameters such as rate constant (k(v)) and kinetic saturation capacity (W(e)) were analyzed and interpreted by means of modified Wheeler equation. Rate constant was found to be increasing while W(e) was found to be invariable with the increase in air flow rate. Both k(v) and W(e) decreased with the increase of temperature, however, no significant effect on W(e) and k(v) was observed due to concentration change (0.3-0.6 mg/l). The values of kinetic saturation capacity were used to predict the service lives/breakthrough times of carbon beds (when used in filtration systems).

Detoxification reactions of sulphur mustard on the surface of zinc oxide nanosized rods.

Detoxification reactions of sulphur mustard, a deadliest chemical warfare agent were studied on the surface of zinc oxide nanorods at room temperature (32+/-2 degrees C) and the data was compared with that of the bulk ZnO. Prior to the reaction, the nanorods of zinc oxide were synthesized by the hydrothermal method and subsequently characterized by XRD, SEM, TG, N(2) BET, FT-IR. The data revealed the formation of nanorods with diameter ranging from 100 nm to 500 nm with length in microns. Obtained nanomaterial along with bulk ZnO were tested as reactive sorbent for the detoxification of sulphur mustard. Reaction was monitored by GC-FID technique and the reaction products were characterized by GC-MS. Data explores the role of hydrolysis and elimination reactions in the detoxification of sulphur mustard and it also reveals that zinc oxide nanorods and bulk ZnO show the half lives of 8.48 h, 24.75 h in the first 12h and 122.47 h, 177.29 h from 12h to 48 h of the reaction.

DNA-probe-target interaction based detection of Brucella melitensis by using surface plasmon resonance.

Surface plasmon resonance (SPR) immunosensor using 4-mercaptobenzoic acid (4-MBA) modified gold (4-MBA/Au) SPR chip was developed first time for the detection of Brucella melitensis (B. melitensis) based on the screening of its complementary DNA target by using two different newly designed DNA probes of IS711 gene. Herein, interaction between DNA probes and target molecule are also investigated and result revealed that the interaction is spontaneous. The kinetics and thermodynamic results derived from the experimental data showed that the interaction between complementary DNA targets and probe 1 is more effective than that of probe 2. Equilibrium dissociation constant (KD) and maximum binding capacity of analyte (Bmax) values for the interaction of complementary DNA target with the immobilized DNA probes were calculated by using kinetic evaluation software, and found to be 15.3 pM (KD) and 81.02m° (Bmax) with probe 1 and 54.9pM and 55.29m° (Bmax), respectively. Moreover, real serum samples analysis were also carried out using immobilized probe 1 and probe 2 with SPR which showed the applicability of this methodology and provides an alternative way for the detection of B. melitensis in less than 10min. This remarkable sensing response of present methodology offer a real time and label free detection of biological warfare agent and provide an opportunity to make miniaturized sensor, indicating considerable promise for diverse environmental, bio-defence, clinical diagnostics, food safety, water and security applications.

Plastic antibody for the recognition of chemical warfare agent sulphur mustard.

Molecularly imprinted polymers (MIPs) known as plastic antibodies (PAs) represent a new class of materials possessing high selectivity and affinity for the target molecule. Since their discovery, PAs have attracted considerable interest from bio- and chemical laboratories to pharmaceutical institutes. PAs are becoming an important class of synthetic materials mimicking molecular recognition by natural receptors. In addition, they have been utilized as catalysts, sorbents for solid-phase extraction, stationary phase for liquid chromatography and mimics of enzymes. In this paper, first time we report the preparation and characterization of a PA for the recognition of blistering chemical warfare agent sulphur mustard (SM). The SM imprinted PA exhibited more surface area when compared to the control non-imprinted polymer (NIP). In addition, SEM image showed an ordered nano-pattern for the PA of SM that is entirely different from the image of NIP. The imprinting also enhanced SM rebinding ability to the PA when compared to the NIP with an imprinting efficiency (alpha) of 1.3.

Breakthrough behavior of sulphur mustard vapor on whetlerite carbon.

Sulphur mustard vapor breakthrough behavior on whetlerite carbon has been studied by using modified Wheeler equation. The values of pseudo-first-order rate constant (k(v)) and kinetic saturation capacity (W(e)) were calculated and the effects of various parameters such as bed height, air flow rate, concentration and temperature on the above parameters have also been studied. Rate constant is found to be increasing with air flow rate, while W(e) is found to be invariable. Both k(v) and W(e) decrease with the increase of temperature, however, no significant effect on W(e) and k(v) is observed due to concentration change. The values of kinetic saturation capacity are used to predict the service lives/breakthrough times of carbon beds (when used in filtration systems).

Adsorptive removal of water poisons from contaminated water by adsorbents.

Adsorptive removal of water poisons such as Pb(II), Cu(II), Mn(II), Hg(II), CN(-), microbes, nerve and blister agents (concentration range from 100 to 1000 mg/L) were studied by using adsorbents such as active carbon, impregnated carbon and bentonite loaded fabric strip. Removal of water poisons (99.5%) could be achieved with an optimum stirring time of 5-15 min and weight of adsorbent of 0.8-8.0 g/100mL contaminated water, respectively. However, 85% bentonite loading was found to be most effective for Pb(II) removal. Effect of contaminants concentration was also studied.

In-situ degradation of sulphur mustard and its simulants on the surface of impregnated carbon systems.

Bis-2-chloroethyl sulphide (sulphur mustard or HD) is an extremely toxic and persistent chemical warfare agent. For in situ degradation of HD and its analogues (simulants), i.e., dibutyl sulphide (DBS) and ethyl 2-hydroxyethyl sulphide (HEES), different carbon systems such as 11-molybdo-1-vanadophosphoric acid impregnated carbon (V(1)/C), ruthenium chloride impregnated carbon (Ru/C) and combination of these two (V(1)/Ru/C) were prepared. These carbons were characterized for cumulative micropore volume and surface area by N(2) BET. The kinetics of the in situ degradation of HD and its simulants were studied and found to be following the first order kinetics. Kinetic rate constants and t(1/2) values were determined. Products were characterized using NMR, IR and GC-MS. Reaction products were found to be sulphoxide and sulphone. The combined system, i.e., 11-molybdo-1-vanadophosphoric acid plus ruthenium chloride (V(1)/Ru/C) was found to be best for in-situ degradation of HD and its simulants. In-situ degradation by polyoxometalate based system was found to be stoichiometry based while Ru/C oxidized HD in presence of chemisorbed oxygen. In combined system of V(1)/Ru/C ruthenium worked as a catalyst and polyoxometalate acted as a source of oxygen. Effect of moisture was also studied in combined system. Rate of degradation of HD was found to be increasing with increased percentage of moisture content.