Fabrication of hierarchically organized nanocomposites of Ba/alginate/carboxymethylcellulose/graphene oxide/Au nanoparticles and their catalytic efficiency in o-nitroaniline reduction

Abstract

Composite gels of Ba/Alginate(Alg)/Carboxymethyl Cellulose (CMC) were prepared by dissipative convective phenomenon. Graphene oxide (GO) and Au nanoparticle (Au-NPs) were successfully encapsulated into polysaccharide matrix. The resulting composite gels were characterized by Fourier Transform Infra-red spectrometry (FTIR), Raman spectroscopy, Powder X-Ray diffractometer (PXRD) technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Rheological and Mechanical behaviors of composite gels were also investigated. The resulting composite gels were tested for the reduction of o-nitroaniline (o-NA), to 1, 2-benenediamine in presence of NaBH4. Ba/Alg/CMC/GO/Au composite gels shows reduction of o-NA within 3 min with a rate constant of 0.45s -1 and composite can be recycled up to 4 successive cycles. IntroductionPolymer matrixes have advantage in tuning the guest-host interaction for furnishing well defined spatial distribution, highlighting kinetic stability for metal nanoparticles and also can provide good mechanical properties for the composites. Polymeric hydrogels create considerable interest because of their high degree of shrinking and swelling properties that are controlled by stimuli such as solvent polarity, solutes, pH, temperature, electric field and light. 1-3 Among polymeric hydrogels, natural polysaccharides (alginate, chitosan, cellulose, starch etc.) based composite hydrogels have attracted great interest in the field of biomedical and environmental applications due to their biocompatible, biodegradable and non-toxic abilities. 4-6 Sodium alginate (Na-Alg) is a binary heteropolymer containing varying proportions of 1,4-linked α-L guluronic acid (G-blocks) and β-D-mannuronic acid (M-blocks) units in a pyranose form, arranged in linear blocks. 7 Anisotropically ordered capillaries and micrometer sized pores have been formed in alginate based polyelectrolyte solution by dissipative convective phenomenon followed by freeze drying technique. 8-9 Khan et al. have successfully synthesized composite gel sponges of alginate/Carboxymethyl cellulose encapsulated with various nanoparticles and crosslinked with calcium (Ca). 10 Carboxymethylcellulose (CMC) is a water-soluble anionic linear polysaccharide and made up of linear β-(1→4)-linked glycanes that exhibit polyelectrolyte characteristics due tothe presence of weakly acidic groups. 11 CMC has a tremendous potential for use in site-specific or controlled-release drug delivery systems owing to its high biocompatibility, biodegradability, and low immunogenicity. [12][13] Recently, carboxymethylcellulose (CMC) and sodium alginate (Na-Alg) based novel superabsorbent hydrogel has been synthesized using methylenebisacrylamide (MBA) as a crosslinking agent. 14 An effective approach for improving properties and potential applications of alginate based composites is to form organic-inorganic composites through incorporation of nanofillers, such as clays, metal nanoparticles (Au, Ag, Fe3O4, TiO2, SiO2), carbon nanotubes and graphene oxide h...

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