A three-dimensional nickel-doped reduced graphene oxide composite for selective separation of hemoglobin with a high adsorption capacity

Abstract

A three-dimensional nickel-doped reduced graphene oxide composite (Ni-rGO) was prepared via one-step reduction, self-assembly of oxide graphene with Ni²⁺ and ethylenediamine, and freeze drying. The composite was characterized by using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, surface charge analysis and so on. The composite was demonstrated to be an efficient adsorbent for separating hemoglobin selectively. When 1 mg of the Ni-rGO composite was used to adsorb hemoglobin in 1.0 mL Britton–Robinson buffer solution at pH 7.0 with 1 mol L⁻¹ NaCl, the adsorption efficiency of hemoglobin was 98.5%. The adsorption behavior of the Ni-rGO composite for hemoglobin fits with the Langmuir adsorption model well, and a theoretical maximum adsorption capacity was 18 468.6 mg g⁻¹ for hemoglobin. The retained hemoglobin on Ni-rGO could be readily eluted by using cetyltrimethyl ammonium bromide solution at pH 11, giving rise to a recovery of 93.6%. Circular dichroism spectra illustrated that there was virtually no change in the conformation of hemoglobin after the adsorption/desorption process. The selective isolation of hemoglobin from human whole blood using the three-dimensional Ni-rGO was well demonstrated by sodium dodecyl sulfate polyacrylamide gel electrophoresis assay.