Catalytic Reactions on the Surface of Ag Nanoparticles: A Photochemical Effect and/or Molecule Property?

Using time-dependent surface-enhanced Raman scattering (TDSERS), we demonstrate the surface-catalyzed oxidation of 3-hydroxy anthranilic acid (HAA) to its azo derivatives. No external source either in the form of laser excitation or heat was required for the surface-catalyzed reaction, which clearly established that thermal energy alone was sufficient. But the possibility of enhanced reaction rate due to the surface plasmon resonance could not be ignored. To mimic in vivo conditions that prevail in healthy and unhealthy cells, SERS measurements were recorded under different environmental conditions. It is shown that the surface-catalyzed azo formation and its isomerization were strongly dependent on the external conditions, namely, temperature, pH, and environment. A plausible mechanism based on electron transfer to the adsorbed O₂ is proposed for the <i>trans–cis</i> isomerization. This study can lead toward a new strategy of surface-catalyzed reactions not only for the synthesis of azo dyes but also to distinguish between the normal and abnormal cells

Interaction between Quantum Dots of CdTe and Reduced Graphene Oxide: Investigation through Cyclic Voltammetry and Spectroscopy

Cyclic voltammetry has been used to investigate the interaction between reduced graphene oxide (r-GO) and CdTe quantum dots (Q-CdTe). For that, the composite of Q-CdTe with r-GO (r-GO-CdTe) was prepared by carrying out the reduction of graphene oxide and the synthesis of Q-CdTe simultaneously, in a single bath. r-GO-CdTe was characterized by UV–visible, steady state fluorescence, time-resolved fluorescence, X-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM). Cyclic voltammetry was employed to determine the quasi-particle gap and band edge parameters of Q-CdTe and r-GO-CdTe. The blue shifts in the quasi-particle gap of r-GO-CdTe have been attributed to the strong interaction of graphene with CdTe. These interactions were further verified by time-resolved fluorescence and Raman spectroscopy which suggested strong electronic coupling between Q-dots and graphene