Sanjay Jha

One-pot green synthesis of carbon dots by using Saccharum officinarum juice for fluorescent imaging of bacteria (Escherichia coli) and yeast (Saccharomyces cerevisiae) cells.

We are reporting highly economical plant-based hydrothermal method for one-pot green synthesis of water-dispersible fluorescent carbon dots (CDs) by using Saccharum officinarum juice as precursor. The synthesized CDs were characterized by UV-visible, fluorescence, Fourier transform infrared (FT-IR), dynamic light scattering (DLS), high-resolution transmission electron microscopic (HR-TEM), and laser scanning confocal microscopic techniques. The CDs are well dispersed in water with an average size of ~3 nm and showed bright blue fluorescence under UV-light (λex=365 nm). These CDs acted as excellent fluorescent probes in cellular imaging of bacteria (Escherichia coli) and yeast (Saccharomyces cerevisiae).

Preparation of multicolor emitting carbon dots for HeLa cell imaging

We have synthesized biocompatible fluorescent carbon dots (CDs) by a one-step hydrothermal method using Solanum tuberosum (potato) as a raw material. The CDs were characterized by UV-visible, fluorescence, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), dynamic light scattering (DLS) and high-resolution transmission electron microscopic (HR-TEM) techniques. We found that the carbonization of potato at ∼170 °C for 12 h produces highly fluorescent CDs of 0.2–2.2 nm size. The synthesized CDs are well dispersed in water and exhibited strong blue and bright blue emissions under UV illumination (λex = 302, 365 nm). The CDs showed a strong emission peak at 455 nm at an excitation wavelength of 374 nm. The CDs acted as fluorescent probes for multicolor (blue, green and red) imaging of HeLa cells and the CDs did not induce cell death, which indicates that the CDs are biocompatible and nontoxic to HeLa cells. Therefore, the CDs can be used as probes for cell-imaging applications in vitro and in vivo.

One-step green synthetic approach for the preparation of multicolor emitting copper nanoclusters and their applications in chemical species sensing and bioimaging.

One-step green microwave synthetic approach was developed for the synthesis of copper nanoclusters (Cu NCs) and used as a fluorescent probe for the sensitive detection of thiram and paraquat in water and food samples. Unexpectedly, the prepared Cu NCs exhibited strong orange fluorescence and showed emission peak at 600 nm, respectively. Under optimized conditions, the quenching of Cu NCs emission peak at 600 nm was linearly proportional to thiram and paraquat concentrations in the ranges from 0.5 to 1000 µM, and from 0.2 to 1000 µM, with detection limits of 70 nM and 49 nM, respectively. In addition, bioimaging studies against Bacillus subtilis through confocal fluorescence microscopy indicated that Cu NCs showed strong blue and green fluorescence signals, good permeability and minimum toxicity against the various bacteria species, which demonstrates their potential feasibility for chemical species sensing and bioimaging applications.

Microwave-assisted synthesis of water-soluble Eu3+ hybrid carbon dots with enhanced fluorescence for the sensing of Hg2+ ions and imaging of fungal cells

In this work, a fluorescent nanosensor based on Eu3+ hybrid carbon dots (Eu3+-CDs) was fabricated by single-step microwave heating using ethylenediaminetetraacetic acid (EDTA), L-cysteine and europium(III) nitrate as reagents. The as-synthesized Eu3+ hybrid CDs exhibited a characteristic fluorescence emission peak at 427 nm upon excitation at a wavelength of 343 nm. Upon the addition of Hg2+ ions, the emission peak of the Eu3+ hybrid CDs was quenched and a linear relationship was observed between the fluorescence quenching intensity and the concentration of Hg2+ ions in the range of 5.0–250 μM with a detection limit of 2.2 μM. The developed nanosensor not only enables selective and sensitive detection of Hg2+ ions but also offers excellent applications in the confocal imaging of fungal cells (Fomitopsis sp.), which holds great promise in biomedical applications.

One-step eco-friendly approach for the fabrication of synergistically engineered fluorescent copper nanoclusters: sensing of Hg2+ ion and cellular uptake and bioimaging properties

Herein, a single-step eco-friendly synthetic method was established for the fabrication of synergistically engineered fluorescent copper nanoclusters (Cu NCs) using curcuma root (Curcuma longa L.) extract (curcuminoids) as a template. These Cu NCs are water-soluble and emitted bright blue fluorescence under UV light illumination at 365 nm. The synergistically engineered Cu NCs exhibited an emission peak at 440 nm with quantum yield of 7.2%. Due to their optical properties, a new fluorescent analytical strategy has been developed for the sensing of Hg2+ ions and used to evaluate cellular uptake and bioimaging properties on cancer cells (RIN-5F and MDAMB231) and fungal cells (Penicillium citrinum). It was interestingly observed that Hg2+ ion effectively quenched the emission peak of Cu NCs at 440 nm, which indicates that Cu NCs act as a fluorescent sensor. Taking advantage of this, a novel fluorescent Hg2+ sensor has been established, which showed a linear range of 0.0005–25 μM with a detection limit of 0.12 nM at room temperature. Furthermore, Cu NCs exhibited good selectivity for Hg2+ against other inorganic species, and the potentiality of the method was demonstrated by detecting Hg2+ ions in water samples. Furthermore, Cu NCs act as probes for imaging of two cancer cells (RIN-5F and MDAMB231) and fungal cells (Penicillium citrinum), and the cell viability results reveals their nontoxic nature.