A silver nanoparticle thin film modified glass substrate as a colourimetric sensor for hydrogen peroxide

In this work, a silver nanoparticle (AgNP) coated glass slide was developed as a device for sensing hydrogen peroxide. AgNPs were synthesised using borohydride reduction with a citrate stabiliser, resulting in a negatively charged stabilised particle surface. The particles were attached to the glass surface using the layer-by-layer (LbL) technique. Poly (diallyldimethylammonium chloride) and poly (styrene sulphonate) were used as cationic and anionic polyelectrolyte layers, respectively. The glass slide was modified with polyelectrolytes leaving a cationic layer on the top surface. The AgNPs were subsequently deposited on the slide via electrostatic interaction. As a result, a dark yellow film of AgNPs was obtained with maximum absorption at 410 nm. Film fabrication based on LbL assembly provided acceptable reproducibility (relative standard deviation = 6.5%). The fabricated film had long-term stability (>6 weeks). A very small quantity of AgNPs was used in this method. Fabrication was performed under ambient conditions. Therefore this fabrication was considered as a green method. The AgNP modified slide was developed to sense hydrogen peroxide. Detection is based upon oxidation of AgNPs by hydrogen peroxide. This results in a change in colour of the film from dark yellow to colourless. Linear calibration was obtained over the range of 1.0--100.0 mM of hydrogen peroxide. The device was successfully used for measuring hydrogen peroxide in urine.