Synergistic reduction of nitrophenols by Au-CDs nanoconjugates with NaBH4.

Developing sustainable and innovative approaches for the efficient reduction of nitrophenols is crucial for environmental remediation, for managing health concerns posed by their widespread presence as hazardous pollutants in industrial effluents and contaminated water. We report the use of 12.9 ± 1 nm (TEM data) sized gold carbon dot nanoconjugates (Au@CDs) for catalytic conversion of o, m, p-nitrophenols to aminophenols by sodium borohydride. A simple approach was followed to synthesize ultra-small and highly stable Au@CDs, using citric acid and PEG as reducing and stabilizing agents. X-ray diffraction analysis verified the formation of nano-crystalline nanoconjugates. These nanoconjugates showed a remarkable catalytic activity in the range of 0.22-0.33 s-1(varying with nanoconjugate concentration) which was much higher compared to conventional chemical methods of reduction. All the catalytic reaction experiments were performed at room temperature (27 ± 2 °C). Furthermore, an increase in rate constant was observed with increasing concentration of nanoconjugates. The catalytic activity of Au@CDs nanoconjugates was observed to be in order of m-nitrophenol > o-nitrophenol > p-nitrophenol with apparent rate constant (kaap) values of 0.068, 0.043 and 0.031, respectively. Comparative analysis with GNPs, CDs and Au@CDs nanoconjugates stated that the nanoconjugates had superior catalytic activity. The research can have significant implications in the development of new strategies for environmental remediation and biomedical applications.

Biocompatible gelatin/carbon dot nanocomposite based urea sensor and the effect of nitrogen ion implantation.

In this study, we have fabricated a novel platform for sensing of urea using gelatin/carbon dots nanocomposite system. The sensor electrode was created by depositing the nanocomposite gel onto thin glass plates coated with indium tin oxide (ITO) using the drop casting technique. The behavior of these electrodes was investigated against a number of bioanalytes in the concentration range of 2-20 mM by cyclic voltammetry. The system was observed to be highly selective for urea with a sensitivity of 1.65 µA/mM/cm in the experimental linear range of 2-20 mM. Furthermore, the gelatin/CD-ITO electrode were also subjected to 50 KeV N2+ ion beam irradiation with varying fluence in the range of 1012 to 1016 ions/cm2. Sensing profile of the irradiated samples for urea suggested enhancement in sensitivity to 2 µA/mM cm2, when the ion fluence was 5 × 1015 ions/cm2. This enhancement after irradiation suggests a clear dependence of detection on the fluence of the ion beam. The observed excellent sensitivity of radiation processed nanocomposite material can be used as an enzyme-free platform for urea detection. Additionally, the CDs showed fluorescence quenching on treatment with mere 50 µM urea suggesting the high sensitivity of the platform.