Hierarchical copper nanocomposites and their applications for catalytic reduction of o-nitroaniline to 1,2-benzenediamine and sensor activities against oxytocin

Cu/Alginate (Alg.)/carboxymethyl cellulose (CMC) hydrogels were synthesized by a dissipative convective process followed by freeze drying method with and without silica, titanium dioxide nanoparticles, and reduced graphene oxide (r-GO). The as-synthesized hydrogels were characterized by Fourier-transform infrared spectrometry, scanning electron microscopy techniques, and powder X-ray diffraction. The mechanical and rheological properties of the hydrogels were also studied. The composite gels were used for the conversion of ortho-nitroaniline (o-NA) to 1,2-benzenediamine in presence of NaBH4. Cu/Alg./CMC/Dex./r-GO composite gel reduced o-NA to 1,2-benzenediamine just in 1.5 min with rate constant 0.50 min−1. The energy of activation (ΔEa), enthalpy change (ΔH≠), entropy change (ΔS≠), and Gibbs free energy change (ΔG≠) of composite Cu/Alg./CMC/Dex./r-GO attributed that the reduction of o-NA to 1,2 benzene diamine is slow process and controlled on the surface of the catalyst Cu/Alg./CMC/Dex./r-GO. Thermodynamic studies confirmed that the rate of reaction increased at higher temperature. Cu/Alg./CMC/Dex./r-GO/GPE showed good sensor activity against oxytocin and determined 0.230 ng/mL of oxytocin in presence of phosphate buffer.