Role of precursors on the photophysical properties of carbon nitride and its application for antibiotic degradation.

In this paper, we provide a comprehensive evaluation of graphitic carbon nitride (C3N4) powders derived from the four different precursors melamine, cyanamide, thiourea, and urea for the photocatalytic degradation of tetracycline (TC) antibiotic under sunlight irradiation. The powders were synthesized by employing the conventional thermal decomposition method. The synthesized powders were examined using different characterization tools for evaluating the photophysical properties. The degradation profile revealed that urea-derived C3N4 showed the highest activity while melamine-derived C3N4 showed the least activity. The TC degradation efficiency of the photocatalyst was found to be influenced more by the surface area values despite extended absorption by melamine in the visible light region. Stability tests on urea-derived C3N4 and others were checked by four runs of TC degradation under sunlight irradiation. The synthesized C3N4 powders also confirmed the dominance of urea-derived powders for cyclic stability.

TEMPO-Oxidized Nanocellulose Fiber-Directed Stable Aqueous Suspension of Plasmonic Flower-like Silver Nanoconstructs for Ultra-Trace Detection of Analytes.

The synthesis of shape-tuned silver (Ag) nanostructures with high plasmon characteristics has become of significant importance in in vitro diagnostic applications. Herein, we report a simple aqueous synthetic route using 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized nanocellulose fibers (T-NCFs) and trisodium citrate (TSC) that results in anisotropically grown flower-like Ag nanoconstructs (AgNFs). A detailed investigation of the concentration and sequence of the addition of reactants in the formation of these anisotropic Ag structures is presented. Our experimental results show that the mechanism underlying the formation of AgNFs is facilitated by the synergistic action of T-NCFs and TSC on the directional growth of Ag nuclei during the primary stage, which later develop into a flower-like structure by the ripening of larger particles consuming smaller Ag particles. As a result the final structure comprises flower-like morphology over which several smaller Ag particles (of size <10 nm) are adhered. The aqueous AgNF colloid exhibits high stability (ζ = -69.4 mV) and long shelf-life at neutral pH (>4 months) by the efficient capping action of T-NCFs. Further, an as-synthesized nanoconstructs shows excellent surface-enhanced Raman scattering activity, which enables ultrasensitive detection of p-aminothiophenol with a concentration down to 10 aM (10-17 M) in a reproducible way. This biosupported synthesis of stable aqueous colloids of AgNF may find potential applications as a biomedical sensing platform for the trace level detection of analyte molecules.