One-pot green synthesis of Ag nanoparticles-graphene nanocomposites and their applications in SERS, H2O2, and glucose sensing

In this contribution, we demonstrate a green, cost-effective, one-pot preparative route toward Ag nanoparticles-graphene (AgNPs-G) nanocomposites in aqueous solution with the use of tannic acid (TA), an environmentally friendly and water-soluble polyphenol, as a reducing agent. Such AgNPs-G nanocomposites were synthesized through one-pot reduction of AgNO3 and GO by TA. We investigated surface enhanced Raman scattering (SERS) and electrochemical properties of the resultant AgNPs-G nanocomposites. It is found that such AgNPs-G nanocomposites show excellent SERS activity as SERS substrates and exhibit notable catalytic performance toward the reduction of H2O2. This enzymeless H2O2 sensor has a fast amperometric response time of less than 2 s. The linear range is estimated to be from 1 x 10(-4) M to 0.01M (r = 0.999) and the detection limit is estimated to be 7 x 10(-6) M at a signal-to-noise ratio of 3. A glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) into chitosan-AgNPs-G nanocomposite film on the surface of a glassy carbon electrode (GCE). This sensor exhibits good response to glucose, and the linear response range is estimated to be from 2 to 10 mM (R = 0.996) at -0.5 V. The detection limit of 100 mu M was achieved at a signal-to-noise ratio of 3. More importantly, we demonstrate successfully its application for glucose detection in human blood serum.