Inorganic-organic hybrid copper phosphate nanoflower coated with an upper rim tetra imidazolyl-phenanthroline derivatized calix[4]arene: Synthesis, characterization and its application as peroxidase mimic catalyst

Abstract

An upper rim tetra-imidazolyl-phenanthroline derivatized calix[4]arene conjugate (L) has been synthesized, and characterized by different analytical, spectral, microscopy and diffraction techniques. The incubation of L with CuSO4.5H2O in PBS buffer (20 mM) for 1 h resulted in the formation of nanoflower material. The L coated copper phosphate nanoflowers (L@CuPNF) were characterized by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and Powder X-ray diffraction, and by microscopy techniques. The peroxidase mimetic activity of L@CuPNF were performed and the results were compared with that of the simple CuPNF as control. The peroxidase activity has been demonstrated using three different substrates, viz., tetramethylbenzidine (TMB), ortho-phenylenediamine (OPD) and guaiacol. The progress of the oxidation reaction of the model substrates in the presence of L@CuPNF and H2O2 were demonstrated through absorption spectra measured as a function of time. The changes can be qualitatively gauged from the observed visual colour variation. The oxidized species were identified by measuring the ESI-MS spectrum of the reaction mixture. The rate of oxidation of these substrates in presence of H2O2 is higher when L@CuPNF is used as catalyst and this is much greater than the reaction rate observed with that of the simple CuPNF that were not coated with L. All this supports that the coating of L expedited the peroxidase mimetic activity of the nanoflowers.