Self-cleaning electrochemical sensors based on TiO2/Ag nanoparticles/SiO2 multilayers

Electroanalytical sensors based on nanomaterials are becoming increasingly popular, owing to their high sensitivity and low detection limits. However, their application, especially in the biomedical field, is hindered by fouling and passivation of the sensing surfaces, due to the surface adsorption of interferents, analytes and by-products, which can cause the irreversible deactivation of the sensing apparatus [1,2]. We have developed a new strategy to impart self-cleaning properties to the sensor surface, exploiting the photocatalytic activity of a top coating based on nanometric TiO2. The top layer also imparts mechanical and chemical resistance to the sensor core, based on noble metal nanoparticles self-assembled on an oxide bottom layer (SiO2/FTO). The role of the oxide layer porosity in enhancing the detection limit was also explored, introducing controlled porosity by an inverse opal approach. The sensor was tested for the detection of a series a relevant biomedical analytes (catecholamine neurotransmitters), showing low detection limits in simulated body fluids. The cleaning procedure can be performed directly on site, in the solution of interest, with a LED torch, allowing the use of this sensor in remote integrated monitoring systems and flow analysis.