One-step hydrothermal green synthesis of silver nanoparticle-carbon nanotube reduced-graphene oxide composite and its application as hydrogen peroxide sensor

A novel sensing composite of silver nanoparticles (AgNPs)-reduced graphene oxide (rGO)-carbon nanotube (MWCNT) was successfully synthesized by a simple one-step hydrothermal method without reducing agent. Mild reduction of GO was carried out under hydrothermal condition. While most conventional approaches make use of multistep chemical methods wherein strong reducing agents, such as hydrazine, hydroquinone, and sodium borohydride are employed, our method provides the notable advantage of a single-step reaction without employing any toxic solvent or reducing agent by providing a novel green synthetic route to produce the nanocomposites of rGO, carbon nanotube and silver. The results of X-ray diffraction (XRD) and Fourier-transform infrared transmission spectroscopy (FT-IR) confirmed the simultaneous formation of silver nanoparticles in the GO and MWCNT matrix. Field emission scanning electron microscope (FESEM) images and transmission electron microscopy (TEM) showed uniform distribution of nanometer-sized silver nanoparticles and narrow-sized MWCNT on GO sheets, which was achieved using silver ammonia complex as the precursor, instead of the commonly used silver nitrate. The composite exhibited excellent electrocatalytic activity for the reduction of H2O2 with a fast amperometric response time less than 3 s. The electrocatalytic activity for the reduction was strongly affected by the concentration of silver ammonia solution in the nanocomposites, with the best electrocatalytic activity observed for the composite of 6:1 volume ratios of MWCNT–GO (3:1, v/v) to Ag(NH3)2OH (0.04 M). The corresponding calibration curve for the current response showed a linear detection range of 0.1–100 mM (R2 = 0. 9985), while the limit of detection was estimated to be 0.9 μM.