Phase-transfer-assisted synthesis of cysteine-Ag nanoparticles/graphene oxide nanocomposite and its enhanced performance in antibiosis and biosensing.

We report a facile, rapid, phase-transfer-assisted process to prepare Ag nanoparticles (AgNP) loaded graphene oxide (GO) nanocomposite, by using cysteine as a highly-effective phase transfer agent for AgNP movement from organic phase to water and subsequently as a covalent linkage for immobilizing AgNP on GO. The obtained c-Ag/GO nanocomposite possesses high nanoparticle loading efficiency, small particle size and monodispersity, strong binding force and good water dispersibility, which endow it with great potential in a variety of bio-applications. To illustrate potentail application, c-Ag/GO and its derivatives c-Ag/rGO were used for antibiosis and biosensing, respectively. The c-Ag/GO composite demonstrates high antibacterial activity against E. coli with a minimal bactericidal concentration of 10 μg ml-1. The biosensor based on c-Ag/rGO exhibits rapid and sensitive response for uric acid detection with a detection limit of 0.025 μM, a sensitivity of 5.76 μA mM-1 and a wide linear range of 0.025 ∼ 2250 μM. The comparative analysis with relevant nanocomposites also reveals the precedence of c-Ag/GO in these applications, thus highlighting the advantages of the developed preparation method for c-Ag/GO.