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The present study aimed to synthesize poly(acrylic acid) hydrogel embedded with magnetic cobalt (Co) nanoparticles and to investigate their potential in adsorption and catalysis. The hydrogel was prepared by facile free radical polymerization reaction and Co nanoparticles were fabricated within hydrogel by reducing Co (II) ions using NaBH4 as reducing agent. Co nanoparticles within hydrogel system imparted magnetic properties to the resulting composite gel and also increased the adsorption capacity. The swelling study of hydrogel was carried out by gravimetric analysis. Different functional groups were identified by Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy analysis was done to investigate dispersion of Co nanoparticles in hydrogel. The bare hydrogel along with Co nanoparticles loaded gel were tested as adsorbent systems for the removal of a cationic dye (methylene blue) from aqueous solution. 95% removal of methylene blue was achieved with a highest adsorption capacity of 836.5 mg/g of adsorbent. The famous adsorption isotherms were used to evaluate adsorption data. Results showed that Freundlich isotherm model was followed with R2 value of 0.95. The hydrogel was also used for catalytic reduction in a toxic pollutant, i.e., 4-nitrophenol. Experimental data for 4-nitrophenol reduction followed pseudo first order kinetics model. Activation energy and apparent rate constant were calculated as 9.24 kJ/mol and 0.24 min−1, respectively. Recycling of the magnetic poly(acrylic acid) hydrogel fabricated with Cobalt nanoparticles was carried out for four consecutive cycles and no significant loss in catalytic activity was observed.

Homopolymer bulk hydrogel of methacrylic acid was synthesized through a new single-step facile rout and used as a template for the fabrication of nickel (Ni) nanoparticles and as adsorbent to remove methylene blue (MB) and Rhodamine-6G (Rh-6G) from water. The Ni nanoparticles containing composite hydrogel was applied as catalyst for the degradation of a nitro compound. The carboxylic groups acted as highly efficient adsorption sites and their high degree was responsible for the removal of huge amounts of MB and Rh-6G from water. The maximum adsorption capacity of poly (methacrylic acid) hydrogel was 685 mg g−1 for MB and 1571 mg g−1 for Rh-6G. The adsorption data of MB was best fitted with Langmuir adsorption isotherm while that of Rh-6G with Temkin adsorption isotherm. Catalytic property of prepared hydrogel integrated with Ni nanoparticles was evaluated by using it as a catalyst for the degradation of 4-nitrophenol (4-NP). The apparent rate constant (k app) observed in this study for the reduction of 4-NP was as high as 0.038 min−1. It was found that this catalyst system can be used repetitively with a slight decrease in catalytic activity.

Anionic hydrogel was prepared by free radical copolymerization of acrylamide and acrylic acid. The anionic groups acted as adsorption sites to load Ni(II) ions and the subsequent reduction of loaded Ni(II) ions into nanoparticles enabled the prepared hydrogels to act template for the preparation of nanostructured Ni particles. The characteristics of the prepared hydrogel and hydrogel–nickel nanoparticle composite were studied with Fourier transform infrared spectroscopy, transmission electron microscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy and X-ray diffraction technique. Swelling behaviour of hydrogel in aqueous medium was analysed by gravimetric analysis. Catalytic performance of the prepared poly(acrylamide-co-acrylic acid)–nickel nanoparticle hydrogel composite was investigated in the reduction of 4-nitrophenol (4-NP). Effects of temperature and catalyst dose on the reduction rate were also studied. Activation energy (Ea) for the reduction of 4-NP was found to be 43.46 kJ/mol. A maximum reduction rate of 0.40 min−1 was observed at room temperature.

Design of effective and efficient nanoscale sensor for the selective monitoring of hydrogen peroxide (H 2 O 2 ) in environmental samples is of great requirement to avoid several diseases; not only but also include diabetes, cancer, cardiovascular disorders, aging and Alzheimer. Herein, we report the fabrication of highly stable silver nanoparticles (Ag NPs) with three different phases (i.e spherical (Sp), star (St) and pyramidal (Py)) via simple wet chemical approach. Among all the three phases, St-Ag-NPs with more exposed catalytic active sites, poor dipolar non-radiative plasmons multipoles and large number of surface defects which in turn enhance ion(s) diffusion between electrode-electrolyte interfaces; shows highest performance in terms of linear range, limit of detection and sensitivity. We observe no interference between electro-active organic compounds (ascorbic acid (AA), uric acid (UA), dopamine (DA) and glucose) and inorganic (NaCl, KCl, Na 2 SO 4 and K 2 SO 4 ) species on the as-fabricated St-Ag-NPs based electrode. Furthermore, We were able to account for the amount of H 2 O 2 generated in the discharged water (effluent) from a poultry firm using the designed St-Ag-NPs based electrode over a wide linear range (∼5 mM) in the presence of co-existing electro-active species. These results show reliability of our designed electrode as useful sensing materials for the detection and monitoring of H 2 O 2 mismanagement in an immediate environment.

The transition metal complexes (Cu(II) and Co(II)) of ferrocene-based thiosemicarbazones hitherto were synthesized (compounds 13–39) by the condensation of different thiosemicarbazides with acetylferrocene in presence of catalytic amount of acetic acid, characterized and their inhibitory potential against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) was evaluated. Both the ligands and their metal complexes in general showed moderate to potent inhibition activity against the said enzymes. All the Cu(II) complexes were found more potent than their respective ligands or with complexes of other metals. Similarly, the studied Co(II) complexes also showed potent inhibition of enzymes inhibition and was found even higher than the standard “Eserine” but with slightly higher IC50 values than that of Cu(II) complexes. In silico studies supported the structure activity relationship of the compounds.

The applications of thioureas in crystal engineering have increased dramatically over the past few years. However, their analogs namely N-imino thioureas/thiosemicarbazones are largely ignored, despite the fact that these can be more interesting with respect to crystal engineering applications due to the presence of an additional N-imino moiety. Aiming to highlight their importance in crystal engineering/supramolecular chemistry, three structurally related coumarin–thiosemicarbazone hybrids (3a–3c) have been designed, synthesized and crystallographically characterized. All of the compounds showed a general preference for the adoption of the cis, trans conformation around the central thiourea moiety; a conformation which is ideal for the formation of a dimeric hydrogen-bonded R22(8){⋯H–N–CS}2 synthon as the building block. Therefore, this dimeric synthon is observed in all of the compounds, regardless of the formation of layered to cage-like three dimensional supramolecular networks depending on different substituents. The prevalence of the cis, trans conformation and the robustness of the thioamide dimer synthon in thiosemicarbazones indicate its potential use as a design element in crystal engineering.

Arsenic and nitrate are ill-famed environmental pollutants that are responsible for various lethal diseases. Their removal from drinking water is very essential. In present study, newly synthesized alumina supported nano zero- valent zinc (Alumina-nZvZ) has been tested to remove arsenic and nitrate. Quantitative analyses of arsenic have been performed spectrophotometrically and while that of nitrates ions colorimetrically. After optimization of time and amount of adsorbent, Langmuir, Freundlich and D-R isotherms were applied to determine different parameters for the assessment of adsorption. Synthesized samples were characterized by scanning electron microscopy (SEM) to evaluate porosity and void size. Alumina coated with reduced ZnCl2 showed better efficiency for removal of arsenic and nitrate ions. Kinetics of adsorption was evaluated by using pseudo first-order and pseudo second-order rate equations.