Ultrasensitive nanostructured platform for the electrochemical sensing of hydrazine

Ultrasensitive electrochemical detection of hydrazine using nanosized Au particles self-assembled on a sol-gel-derived 3D silicate network is described. The citrate-stabilized gold nanoseeds (GNSs) were self-assembled on the thiol groups of the silicate network, which was preassembled on a polycrystalline Au electrode. The size of the GNSs on the network was enlarged by a seed-mediated growth approach, and the GNSs were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and electrochemical measurements. The enlarged nanoparticles (GNEs) on the silicate network have a size distribution between 70 and 100 nm and behave as a nanoelectrode ensemble. This nanostructured platform is highly sensitive toward the electrochemical oxidation of hydrazine. A very large decrease in the overpotential (similar to 800 mV) and significant enhancement in the peak currents with respect to the bulk Au electrode were observed without using any redox mediator. The nanostructured platform shows excellent sensitivity with an experimental detection limit (S/N = 11) of 200 pM. The electrocatalytic properties of the nanostructured platform are strongly dependent on the particle coverage on the silicate network. This sensing platform is very stable and can be used for the continuous monitoring of hydrazine. The ultrasensitive nature of the sensor is ascribed to the existence of nanoelectrode ensembles.