Microwave-assisted synthesis of carbon dots as reductant and stabilizer for silver nanoparticles with enhanced-peroxidase like activity for colorimetric determination of hydrogen peroxide and glucose.

Abstract

A carbon silver nano-assembly was prepared from silver nanoparticles and carbon dots (AgNP@CD). It was used to quantify hydrogen peroxide and glucose by UV-visible spectroscopy. Banana peels were used to prepare the CDs by a microwave-assisted method. The CDs can be prepared within 5min at 700W. They act as (a) substrate, (b) stabilizer, and (c) reductant to convert silver ions to AgNPs. The nano-assembly was characterized by UV-visible spectroscopy, Fourier-transform infrared spectroscopy, atomic force microscopy, and transmission electron microscopy. The CDs have a particle size of 1.4nm. Photoexcitation of theCDs with a UV lamp of 365nm results inblue fluorescence. The absorption spectra of the CDs show a peak at 205nm along the wide shoulder absorption band. On incorporation ofthe Ag nanoparticles into the CDs matrix, the color of the CDs turns into yellow and an additional absorbance peak at 408nm appears. FTIR spectroscopy shows that different functional groups are present on the CDs. They are responsible for the stabilization of the AgNPs. On exposure to H2O2, the color of the nano-assembly disappears gradually. Hence, the assembly can be used as a colorimetric indicator probe for H2O2 with a linear response in the0.1-100μMconcentration range. It can also be applied to the determination of glucose by using glucose oxidase which causes the formation of H2O2 from glucose. The linear response ranges from 1- 600μM. The detection limits for H2O2 and glucose are 9nM and 10nM, respectively. In our perception, this is the lowest detection limit reported so far. The AgNP@CD nano-assembly does not respond to saccharides, maltose, fructose, and lactose. It can be used to quantify glucose in dilutedblood plasma. Graphical abstractSchematic representation of microwave-assisted synthesis of AgNP@CDs with enhanced-peroxidase like activity for colorimetric determination of hydrogen peroxide and glucose.