Features of Silver-Nanoparticle-Based Electrochemical Sensors. Shape and Size Effects

The effect of the shape and size of silver nanoparticles on the electrochemical characteristics of sensors based on them is considered by the example of the hydrogen peroxide (H2O2) determination. A sodium-borohydride-based electrochemical sensor yields a one-fold increase in the analytical signal when H2O2 in a concentration of 1 x 10(-7) M is added. A sensor based on the finest (0.5-17.5 nm) spherical silver nanoparticles obtained using two reducing agents (sodium borohydride and sodium citrate) simultaneously makes it possible to increase the H2O2-determination sensitivity by six orders of magnitude (the detection limit is 0.16 x 10(-13) M). The detectable H2O2-concentration range varies within half an order of magnitude and is (0.8-3.0) x 10(-13) M. A sensor based on silver nanoparticles of various shapes 10-55 nm in size obtained using sodium citrate also exhibits an increase in the H2O2-determination sensitivity by six orders of magnitude (the detection limit is 0.74 x 10(-13) M). This sensor has a detectable H2O2 concentration range within an order of magnitude: (1.0-10.0) x 10(-13) M. The causes of the different sensitivities and detectable H2O2-concentration ranges for the electrochemical sensors are discussed depending on the size and shape of silver nanoparticles. The mechanism of the interaction of adsorbed oxygen with silver nanoparticles on the sensor surface is proposed.