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

Layered double hydroxides (LDHs) have been combined with graphene and/or carbon nanotubes to prepare new composite materials with fascinating electrochemical features. For the first time, this work describes the development of an electrosynthesis protocol that allows the deposition of thin films of a Ni/Al LDH on glassy carbon electrodes previously modified with carbon nanomaterials. Three different approaches (potentiostatic, galvanostatic, and potentiodynamic) were investigated to identify the best procedure. In all cases the potentiodynamic synthesis exhibits better reproducibility than the potentiostatic one which is the most used in the literature. The reliability of the synthesis protocol was evaluated by performing the LDH electro-deposition using glassy carbon electrodes modified with multiwalled carbon nanotubes and/or electrochemically reduced graphene oxide arranged in five configurations. XRD and SEM analysis confirmed the LDH formation. Cyclic voltammetry shows the graphene presence ensured a large electrochemically active area with values 3 times higher than the one observed for an LDH deposited on a bare glassy carbon. Moreover, impedance electrochemical spectroscopy highlights that carbon nanomaterials play a key role in reducing the charge transfer resistance. In fact, it decreases from 2800 K Omega recorded for LDH deposited on bare glassy carbon to about 600 Omega for the best composite material. The materials were tested for glucose electrooxidation which was exploited for the fabrication of a sensor with high sensitivity (2.6 A M-1 cm(-2) for the best device) and low limit of detection (0.6 mu M for the best device).