Crosslinked anionic polymer encapsulation formed on Fe3O4 nanoparticles has been found to be selective towards the least hydrated competing anions.

Chitosan (CSN) and its derivatives are being exploited for their potential role in agriculture in mitigating environmental stress factors. The present study was aimed to enhance the synthesis of chitosan (CSN)-based silver nanoparticles (Ag NPs) using γ-irradiated chitosan (IR-CSN) and to study the antimicrobial activity of IR-CSN–Ag NPs. The chitosan–silver nanocomposites (CSN–Ag NPs) were prepared by employing the green synthesis method using normal chitosan (high molecular weight (MW), NL-CSN) and oligochitosans (low MW, IR-CSN). The latter was derived by irradiation with γ rays ( 60 Co) at 100 kGy dose to obtain a lower MW (approximately 25 kDa). NL-CSN and IR-CSN (0.0–2.5% w/v) were amalgamated with different concentrations of silver nitrate (0.0–2.5% w/v) and vice versa. The UV–visible spectra displayed a single peak in the range of 419–423 nm, which is the characteristic surface plasmon resonance (SPR) for Ag NPs. The physicochemical properties were assessed using different methods such as transmission electron microscopy (TEM), Fourier transform infrared (FTIR), zetasizer, elemental (CHNS) analysis, etc. The degree of Ag NP synthesis was more in IR-CSN than NL-CSN. The in vitro disc diffusion assay with IR-CSN–Ag NPs exhibited a significantly higher antimicrobial activity against Escherichia coli . Further evaluation of the antifungal activity of IR-CSN and Ag NPs showed a synergistic effect against chickpea wilt ( Fusarium oxysporum f. sp. ciceris ). The study has provided a novel approach for the improved synthesis of CSN–Ag nanoparticle composites using γ-irradiated chitosan. This study also opens up new options for the development and deployment of γ-irradiated chitosan–silver nanocomposites for the control of phytopathogens in sustainable agriculture.

The nano‐gel like aggregates consisting of Fe3O4@PAA−Pd(II) has been formed by interparticle crosslinking via amide bonds. The chemical and physical structures and superparamagnetic properties of thus formed Fe3O4@PAA−Pd(II) have been characterized. The catalytic activity of the Fe3O4@PAA−Pd(II) in 22 different examples of Mizoroki‐Heck coupling reactions has been found to be excellent under solvent free condition in the presence of base at 100 0C. The turn over number and turn over frequency of Fe3O4@PAA−Pd(II) are found to be 304787 and 67730 h−1, respectively, with no significant deterioration of catalytic activity after five successive cycles of the catalyst. X‐ray photoelectron spectroscopy has been used to understand the mechanism and changes in the catalyst during reaction. However, the reaction of chlorobenzene, bromobenzene and substituted iodo compounds such as p‐iodophenol, p‐iodobenzoic acid with acrylates/acrylamides are not successful in the presence of Fe3O4@PAA−Pd(II) suggesting that the reaction with acidic substrates and substrates, prone to deprotonation, are not suitable for the above transformation with the optimized reaction conditions used for aryl iodide.

Polymer‐encapsulated magnetite nanoparticles bearing Hexamethylenetetramine (Fe3O4@HMTA) have been developed for catalysing the aza‐Michael addition to form β‐amino compounds. The effects of solvent, amount and reuse on catalytic activity of the Fe3O4@HMTA have been studied. The catalytic activity of the Fe3O4@HMTA has not deteriorated during successive recycling. Eight different substrates have been subjected to aza‐Michael additions, and yields of the products in the range of 50–90 % have been observed in the presence of catalyst depending upon the substituent groups in the reactants. The formation of a single chiral adduct by reacting a acrylamide derivative of l‐proline benzyl ester with morpholine seems to suggest that the reaction conditions preclude the racemization of products.