Ni/Al Layered Double Hydroxide and Carbon Nanomaterial\nComposites for Glucose Sensing

Abstract

Layered\ndouble hydroxides (LDHs) have been combined with graphene\nand/or carbon nanotubes to prepare new composite materials with fascinating\nelectrochemical features. For the first time, this work describes\nthe development of an electrosynthesis protocol that allows the deposition\nof thin films of a Ni/Al LDH on glassy carbon electrodes previously\nmodified with carbon nanomaterials. Three different approaches (potentiostatic,\ngalvanostatic, and potentiodynamic) were investigated to identify\nthe best procedure. In all cases the potentiodynamic synthesis exhibits\nbetter reproducibility than the potentiostatic one which is the most\nused in the literature. The reliability of the synthesis protocol\nwas evaluated by performing the LDH electrodeposition using glassy\ncarbon electrodes modified with multiwalled carbon nanotubes and/or\nelectrochemically reduced graphene oxide arranged in five configurations.\nXRD and SEM analysis confirmed the LDH formation. Cyclic voltammetry\nshows the graphene presence ensured a large electrochemically active\narea with values 3 times higher than the one observed for an LDH deposited\non a bare glassy carbon. Moreover, impedance electrochemical spectroscopy\nhighlights that carbon nanomaterials play a key role in reducing the\ncharge transfer resistance. In fact, it decreases from 2800 KΩ\nrecorded for LDH deposited on bare glassy carbon to about 600 Ω\nfor the best composite material. The materials were tested for glucose\nelectrooxidation which was exploited for the fabrication of a sensor\nwith high sensitivity (2.6 A M^–1 cm^–2 for the best device) and low limit of detection (0.6 μM for\nthe best device).