Biogenic synthesis of carbon quantum dots from garlic peel bio-waste for use as a fluorescent probe for sensing of quercetin.

Highly fluorescent and water-soluble carbon quantum dots (CQDs) were synthesized from the bio-waste source of garlic peels (renovation of bio-waste into bio-asset) using a controlled carbonization method. Synthesized CQDs were characterized by various analytical methods and explored as a fluorogenic probe for the recognition of quercetin (QT). Ultraviolet-visible (UV-vis) result shows an absorption maximum at 275 nm attributed to the conjugation of C=C and C=O of CQDs and demonstrates a blue emission in the range 330-410 nm. Selectivity was performed with various biomolecules, except for QT, all others do not exhibit any considerable change in the fluorescence of CQDs. On the interaction with QT, emission was completely quenched due to Förster energy transfer (FET), confirming the high selective to QT. Effect of pH, sensitivity, and stability studies displayed excellent results under optimized conditions. The limit of detection (LOD) fluorescent probe was found to be 6.73 µM. Our approach may suggest a new platform for the development of quick and low-cost CQDs-based sensors for environmental and biological purposes.

Naked-Eye Detection of Mercury Ions from Morphological Transition of Silver Nanocubes: Tuning Sensitivity Using Co-Staining Agent.

A simple, low-cost and highly selective nanosensor was developed for naked-eye detection of mercury ions (Hg2+) based on Eosin/silver nanocubes (Eosin/AgNCbs). Silver nanocubes (AgNCbs) were synthesized by polyol assisted chemical method. HR-TEM result shows the formed AgNCbs have a mean diameter of 84±0.005 nM (diagonally measured) and edge length of 55±0.01 nM. XRD result confirms that the AgNCbs are single crystalline in nature with a phase structure of face centered cubic (FCC) of silver. On interaction of Hg2+, AgNCbs exhibits a color change from gray to black up to 16.67 µM of Hg2+ owed to the formation of solid like bimetallic complex of Ag/Hg amalgam. The selectivity of AgNCbs was evaluated with several other toxic metal ions including, Mg2+, Ba2+, Ca4+, Pb2+, Cd4+, Zn2+, Co2+, Cu2+, K+ and Ni2+ and found good selectivity towards Hg2+. The sensitivity of the AgNCbs sensor system was tuned by using Eosin as a co-staining agent. The Eosin/AgNCbs showed a limit of detection of 60±0.050 nM with the color change from orange to purple. The results suggests that the Eosin/AgNCbs nanosensor exhibits good selectivity, sensitivity, repeatability and rapid response, which could be explored for real-time detection of Hg2+ in environmental and biological samples.

Seed-free synthesis of 1D silver nanowires ink using clove oil (Syzygium Aromaticum) at room temperature.

HYPOTHESIS: Silver nanowires (AgNWs) have been demonstrated to be a promising next generation conducting material and an alternative to the traditional electrode (ITO) because of its high conductivity, transparency and stability. Generally, AgNWs are synthesized by chemical method (mainly polyol reduction method) at high temperature in the presence of exotic seeds. The present work aims at the green approach for preparation and characterization of 1D AgNWs ink using clove oil (Syzygium Aromaticum) at room temperature. EXPERIMENTS: AgNWs was prepared by green synthesis using clove oil as reducing as well as capping agent at room temperature. The obtained ink was purified, filtered and redissolved in methanol. FINDINGS: The prepared AgNWs showed an absorption peaks at 350 and 387nm in the UV-vis spectrum due to transverse SPR mode of silver. From the HR-TEM analysis, it was observed that the AgNWs possess an average diameter and length of ∼39±0.01nm and ∼3µm, respectively. The obtained AgNWs are crystalline in nature and are arranged in a perfect crystal lattice orientation, which was confirmed from the selected area electron diffraction studies. Moreover, the X-ray diffraction analysis confirms the face centered cubic structure. The AgNWs coated glass substrate shows an electrical conductivity of ∼0.48×10(6)S/m.