Synthesis and Characterization of pH-Responsive Organic–Inorganic Hybrid Material with Excellent Catalytic Activity

A review on Ag nanoparticles fabricated in microgels

In recent years, there has been growing interest in the composites of multi-responsive microgels and silver nanoparticles. This innovative hybrid system harnesses the responsive qualities of microgels while capitalizing on the optical and electronic attributes of silver nanoparticles. This combined system demonstrates a rapid response to minor changes in pH, temperature, ionic strength of the medium, and the concentration of specific biological substances. This review article presents an overview of the recent advancements in the synthesis, classification, characterization methods, and properties of microgels loaded with silver nanoparticles. Furthermore, it explores the diverse applications of these responsive microgels containing silver nanoparticles in catalysis, the biomedical field, nanotechnology, and the mitigation of harmful environmental pollutants.

Catalytic innovations: Improving wastewater treatment and hydrogen generation technologies

The effective reduction of hazardous organic pollutants in wastewater is a pressing global concern, necessitating the development of advanced treatment technologies. Pollutants such as nitrophenols and dyes, which pose significant risks to both human and aquatic health, making their reduction particularly crucial. Despite the existence of various methods to eliminate these pollutants, they are not without limitations. The utilization of nanomaterials as catalysts for chemical reduction exhibits a promising alternative owing to their distinguished catalytic activity and substantial surface area. For catalytically reducing the pollutants NaBH4 has been utilized as a useful source for it because it reduces the pollutants quiet efficiently and it also releases hydrogen gas as well which can be used as a source of energy. This paper provides a comprehensive review of recent research on different types of nanomaterials that function as catalysts to reduce organic pollutants and also generating hydrogen from NaBH4 methanolysis while also evaluating the positive and negative aspects of nanocatalyst. Additionally, this paper examines the features effecting the process and the mechanism of catalysis. The comparison of different catalysts is based on size of catalyst, reaction time, rate of reaction, hydrogen generation rate, activation energy, and durability. The information obtained from this paper can be used to steer the development of new catalysts for reducing organic pollutants and generation hydrogen by NaBH4 methanolysis.

Fabrication of NIPMAM based polymer microgel network assisted rhodium nanoparticles for reductive degradation of toxic azo dyes

The aim of this study was to prepare poly-N-isopropylmethacrylamide-co-acrylic acid-acrylamide [p-(NIPMAM-co-AA-AAm)] via precipitation polymerization in an aqueous medium. Rhodium nanoparticles were formed in the microgel network by an in-situ reduction technique with the addition of sodium borohydride as a reducing agent. Pure p-(NIPMAM-co-AA-AAm) and hybrid microgels [Rh-(p-NIPMAM-co-AA-AAm)] microgels were examined by using UV-Visible, FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), DLS (Dynamic Light Scattering) and XRD (X-Ray Diffraction) techniques. The catalytic activities of the hybrid microgel [Rh-(p-NIPMAM-co-AA-AAm)] for the degradation of azo dyes such as alizarin yellow (AY), congo red (CR), and methyl orange (MO) were compared and the mechanism of the catalytic action by this system was examined. Various parameters including the catalyst amount and dye concentration influenced the catalytic decomposition of azo dyes. In order to maximize the reaction conditions for the dye's quick and efficient decomposition, the reaction process was monitored by spectroscopic analysis. The rate constants for reductive degradation of azo dyes were measured under various conditions. When kapp values were compared for dyes, it was found that [Rh-(p-NIPMAM-co-AA-AAm)] hybrid microgels showed superior activity for the degradation of MO dyes compared to the reductive degradation of CR and AY.

Silver-assisted reduction of nitroarenes by an Ag-embedded curcumin/melamine-functionalized magnetic nanocatalyst

In the current study, we introduce a hybrid magnetic nanocomposite comprised of curcumin (Cur), iron oxide magnetic nanoparticles (Fe₃O₄ MNPs), melamine linker (Mel), and silver nanoparticles (Ag NPs). Initially, a facile in situ route is administrated for preparing the Fe₃O₄@Cur/Mel-Ag effectual magnetic catalytic system. In addition, the advanced catalytic performance of the nanocomposite to reduce the nitrobenzene (NB) derivatives as hazardous chemical substances were assessed. Nevertheless, a high reaction yield of 98% has been achieved in short reaction times 10 min. Moreover, the Fe₃O₄@Cur/Mel-Ag magnetic nanocomposite was conveniently collected by an external magnet and recycled 5 times without a noticeable diminish in catalytic performance. Therefore, the prepared magnetic nanocomposite is a privileged substance for NB derivatives reduction since it achieved notable catalytic activity.

Swift catalytic reduction of hazardous pollutants by new generation microgels

In this manuscript, we report for the first time a new generation microgel synthesis without using any divinyl functionalized cross-linker. A new generation less crosslinked microgel structure has been achieved by optimizing the amount of N-hydroxy methyl acrylamide (NHMA) and using a fixed amount of styrene (St), acrylic acid (AA) and N-vinyl pyrrolidone (NVP) via a free radical emulsion solution polymerization technique. Poly(NHMA) works as a hydrophilic as well as a crosslinking agent. Furthermore, microgels have been upgraded into a composite by incorporation of Ag nanoparticles for catalytic reduction applications. Microgels and their composites have been characterized by EDAX, FT-IR, particle size analyzer, SEM, TEM, TGA, UV-vis spectroscopy and XRD. Methylene blue (MB) dye and p-nitrophenol (PNP) were chosen as model hazardous pollutants for catalytic reduction applications. Microgels efficiently adsorb both pollutants over the surface and microgel_Ag composites dramatically reduced both pollutants in the non-toxic form at room temperature by using smaller doses of NaBH₄.

Multi-functional organic–inorganic hydrogel microspheres as efficient catalytic system for reduction of toxic dyes in aqueous medium

Poly(N-isopropylacrylamide-acrylamide-methacrylic acid) [p(NAM)] colloidal particles were synthesized and stabilized in aqueous medium. Ag nanoparticles were fabricated inside the p(NAM) system by in-situ reduction of Ag+ ions with NaBH4 to obtain Ag-p(NAM) organic–inorganic hybrid with fascinating catalytic properties. Various characterization techniques including XRD, FTIR, DLS, TEM and UV–visible spectroscopy were used to confirm the fabrication of p(NAM) and Ag-p(NAM) in aqueous medium. Loading of silver nanoparticles into the p(NAM) does not affect responsive properties of the colloidal system. Ag-p(NAM) system was used as catalyst for reduction of toxic dyes including methyl orange (MO) and Congo red (CR) from aqueous medium. Ag-p(NAM) catalyzed reduction of dyes was carried out under different reaction conditions to explore the catalytic process of degradation. The Ag-p(NAM) catalytic system is recyclable and reusable with almost same catalytic activity up to four cycles.

Recyclable polymer microgel stabilized rhodium nanoparticles for reductive degradation of para-nitrophenol

The purpose of present work is to fabricate rhodium nanoparticles in Poly(N-isopropylmethacrylamide-acrylic acid) [p(NMAA)] microgel system. Synthesized polymer [p(NMAA)] microgels and rhodium nanoparticles loaded [Rh-p(NMAA)] microgels were analyzed by FTIR (Fourier Transform Infra-red) spectroscopy, XRD (X-ray Diffraction) analysis and UV/Vis (Ultraviolet–Visible) spectroscopy. Catalytic reductive conversion of P-nitrophenol (P-Nph) into P-aminophenol (P-Aph) via Rh-p(NMAA) was used to evaluate the catalytic activity of the hybrid microgel [Rh-p(NMAA)]. Kinetic study of catalytic reductive conversion of P-Nph was explored by considering various reaction parameters. It was found that the value of first order observed rate constant (k obs) was varied from 0.019 to 0.206 min−1 with change in concentration of sodium borohydride (SBH) from 3 to 14 mM at given temperature. However, further increment in concentration of SBH from 14 to 17 mM, reduced the value of k obs from 0.206 to 0.156 min−1. The similar dependence of k obs on concentration of P-Nph was observed at specific concentration of SBH and Rh-p(NMAA) at constant temperature. Kinetic study reveals that conversion of P-Nph to P-Aph takes place on the surface of rhodium nanoparticles (RhNPs) by adopting different reactions intermediates and obeys the Langmuir-Hinshelwood mechanism. Reduction efficiency of recycled Rh-p(NMAA) catalytic system was also measured and no significant reduction in the percentage catalytic activity was obtained up to four cycles for P-Nph conversion into P-Aph.

Silver nanoparticles stabilized in polymer hydrogels for catalytic degradation of azo dyes

Fabrication of poly-(N-isopropylmethacrylamide-co-methacrylic acid) [p(NMA)] microgels to be utilized as microreactors to synthesize stable Ag nanoparticles for catalytic reductive degradation of dyes has been addressed in this work. Both p(NMA) microgel and Ag-p(NMA) hybrid microgel systems have been analyzed by Fourier transform infra-red and Dynamic light scattering, Ultraviolet-Visible spectroscopy, X-ray diffraction and Transmission electron microscopy. Catalytic activity of Ag-p(NMA) towards reductive degradation of Congo Red (CR), Methyl Orange (MO) and Alizarin Yellow (AY) was investigated under different operating conditions. Spectrophotometry was employed to check the progress of reaction while the rate constant (k_app) value of degradation reaction was determined under various conditions to optimize reaction parameters for rapid and economical degradation of these dyes. An increase in k_app value was observed by increasing feed content of dye up to a certain value that decreases again by further increment in dye concentration which reflects that catalysis follows Langmuir-Hinshelwood mechanism. A gradual increase in the k_app value was also observed with increasing quantity of hybrid microgel used as a catalyst. By comparing k_app values of degradation of aforementioned dyes, it was found that Ag-p(NMA) hybrid microgel gives better activity for MO dye degradation in comparison to catalytic degradation of CR and AY.

Palladium nanoparticles-anchored dual-responsive SBA-15-PNIPAM/PMAA nanoreactor: a novel heterogeneous catalyst for a green Suzuki–Miyaura cross-coupling reaction

Palladium nanoparticles-anchored dual-responsive SBA-15-copolymer nanoreactor was developed as a novel heterogeneous catalyst for green Suzuki–Miyaura cross-coupling reaction.

Hybrid Microgels for Catalytic and Photocatalytic Removal of Nitroarenes and Organic Dyes From Aqueous Medium: A Review

Polymer microgels loaded with inorganic nanoparticles have gained much attention as catalytic systems for reduction of toxic chemicals. Enhanced catalytic properties of hybrid microgels are related to the stimuli responsive nature of microgels and extraordinary stability of nanoparticles within network of polymer microgels. Catalytic properties of hybrid microgels can be tuned very easily by slight variation in environmental conditions. Herein we have reviewed catalytic reduction of toxic chemicals such as nitroarenes and organic dyes in the presence of appropriate hybrid microgel catalytic systems under different operating conditions of reaction. Recent advancements in catalytic behavior of hybrid microgels with special emphasis on their ability to catalytically degrade various toxic chemicals has been presented in this review.