Poly(N-isopropylacrylamide)-chitosan nanogels for nanotechnological and catalytic applications

Polymer nanogels consisting of poly(N-isopropylacrylamide) and chitosan [P(NC)] were synthesized using a free radical precipitation polymerization technique in an aqueous environment. This process involved the polymerization of N-isopropylacrylamide (NIPAAM) with chitosan (CS) and a cross-linker. These P(NC) nanogels were utilized as nano-reactors for the synthesis of gold nanoparticles (AuNPs), which were formed within the polymeric network through an in-situ reduction process using tetrachloroauric acid [H(AuCl₄)] as precursor salt and sodium borohydride (NaBH₄) as the reductant. Various analytical methods, including Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA), Ultraviolet–visible spectroscopy (UV–Vis), and Fourier transform infrared spectroscopy (FTIR), were employed to confirm the formation of P(NC) nanogels and the incorporation and durability of AuNPs within the P(NC) nanogels. The AuNPs loaded P(NC) nanogels were utilized as catalysts for the reduction of 4-nitrophenol (4-NiP) into 4-aminophenol (4-AmP) in the presence of NaBH₄. This system was also used to degrade a number of dyes including methylene blue (MB), methylene orange (MO), rhodamine B (RhB), brilliant blue (BB) and eosin Y ((EY) by using NaBH₄ as a reducing agent. The Au-P(NC) catalyst exhibited remarkable efficiency, facilitating the fast reduction of 4-NiP and degradation of dyes within a very short interval of time. This system stands out for its economic usage, as even a small quantity of it can efficiently reduce toxic pollutants like 4-NiP and dyes. The results of the reactions highlighted exceptional yield, emphasizing the effectiveness and recyclability of the Au-P(NC) hybrid nanogels as highly capable catalysts.