Sourov Chandra

Luminescent S-doped carbon dots: an emergent architecture for multimodal applications

A facile route has been developed to synthesise and isolate sulphur doped fluorescent carbon dots for the first time. Such carbogenic quantum dots exhibit a wide band gap of 4.43 eV with a high open circuit voltage (VOC) of 617 mV along with a fill factor (FF) as high as 37%, using phenyl-C60-butyric acid methyl ester (PCBM) as the electron transporting layer. Besides the wide band gap, which is useful in the fabrication of solar cells, sulphur modified carbon dots also exhibit a high fluorescence quantum yield of 11.8% without any additional surface passivation, producing a unique fluorescent probe for further applications. In addition, the particles have a strong tendency to interact with the surface of gold nanoparticles and produce a thin fluorescent layer over their surfaces. Moreover, as they are completely biocompatible in nature, the highly fluorescent S-doped carbon dots have a strong potential for use in bioimaging applications. Interestingly, owing to the presence of oxygen and sulphur functionality, the highly negatively charged particles can easily bind with positively charged DNA-PEI complexes, simply by mixing them, and after interaction with DNA, bright blue fluorescence has been observed under an excitation wavelength of 405 nm .

Tuning of photoluminescence on different surface functionalized carbon quantum dots

A simple microwave assisted route has been formulated to synthesise various surface functionalized carbogenic quantum dots from biodegradable polysaccharides. The photoluminescence (PL) properties of such surface functional carbon quantum dots (CQDs) have been tuned by the in situ addition of high boiling organic solvents during the synthesis of CQDs under microwave irradiation. Several divalent cations have also been added to investigate the variation of PL intensity after cationic modifications. Some straightforward mechanistic approaches have been predicted to rationalize the enhancement or quenching of the fluorescence by the introduction of organic and inorganic substrates.

Rapid microwave synthesis of fluorescent hydrophobic carbon dots

Fluorescent hydrophobic carbon dots (HCDs) have been fabricated from a poloxamer by a simple microwave assisted process within a few minutes for the first time. Small and distinct spherical HCDs emitted bright blue and green fluorescent light depending upon the excitation wavelength and were dispersed easily in a wide variety of organic solvents. HCDs exhibited excellent water resistant behavior with a contact angle of ∼122° enforcing good hydrophobic character which will be quite useful in potential surface applications.

Photochemical Modulation of Biosafe Manganese Nanoparticles on Vigna radiata: A Detailed Molecular, Biochemical, and Biophysical Study

Manganese (Mn) is an essential element for plants which intervenes mainly in photosynthesis. In this study we establish that manganese nanoparticles (MnNP) work as a better micronutrient than commercially available manganese salt, MnSO4 (MS) at recommended doses on leguminous plant mung bean (Vigna radiata) under laboratory condition. At higher doses it does not impart toxicity to the plant unlike MS. MnNP-treated chloroplasts show greater photophosphorylation, oxygen evolution with respect to control and MS-treated chloroplasts as determined by biophysical and biochemical techniques. Water splitting by an oxygen evolving complex is enhanced by MnNP in isolated chloroplast as confirmed by polarographic and spectroscopic techniques. Enhanced activity of the CP43 protein of a photosystem II (PS II) Mn4Ca complex influenced better phosphorylation in the electron transport chain in the case of MnNP-treated chloroplast, which is evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and corresponding Western blot analysis. To the best of our knowledge this is the first report to augment photosynthesis using MnNP and its detailed correlation with different molecular, biochemical and biophysical parameters of photosynthetic pathways. At effective dosage, MnNP is found to be biosafe both in plant and animal model systems. Therefore MnNP would be a novel potential nanomodulator of photochemistry in the agricultural sector.

Room temperature and solvothermal green synthesis of self passivated carbon quantum dots

Highly fluorescent, self passivated carbon quantum dots (CQDs) have been synthesized using PEG-200 at room temperature for the first time followed by solvothermal modification to increase the quantum yield of these nano carbons. At elevated temperature and pressure good surface passivation has been observed. No sophisticated instrument nor passivating agent is required to fabricate these CQDs, making the procedure unique and novel with respect to all the existing protocols. Solvothermally synthesized carbon quantum dots (ST-CQDs) exhibited minimum toxicity and can be used easily for bioimaging.

Porous ZnO nanorod for targeted delivery of doxorubicin: in vitro and in vivo response for therapeutic applications

Cancer cell specific targeted delivery (TDD) by porous nanocarrier is on a high role. Here in a simple route for the synthesis of porous ZnO nanorods (ZnO) has been demonstrated. ZnO expressed very high surface area of 305.14 m2 g−1 (SBET) and uniformly distributed pores of 5 nm. In continuation ZnO has been fabricated with 3-aminophosphonic acid followed by folic acid to yield folate conjugated porous ZnO nanorod (ZnO-FA). High surface area, uniformly distributed pores on its surface make the nanocarrier suitable for high drug loading (88%) of the anticancer drug doxorubicin (DOX). A pH triggered drug release was observed with minimum release in pathophysical conditions. In vitro efficacy of DOX loaded ZnO-FA (ZnO-FA-DOX) has been evaluated against breast cancer cells MDA-MB-231, which is not possible alone by DOX or ZnO-FA. Targeted scaffold with pendant –NH2 group has been covalently bonded with fluorescent dye (RITC) for cellular uptake and imaging studies in MDA-MB-231 cells; the possible pathway for cancer regression has also been evaluated. Even in vivo acute and intravenous toxicological evaluation on murine model system complemented biocompatibility of ZnO-FA in TDD. All together we have collaged a template free synthesis of porous ZnO nanorod, successful targeting on to cancer cells, high drug loading, pH triggered drug release, in vitro efficacy of ZnO-FA-DOX against MDA-MB-231 cells and in vivo compatibility as well. We envisioned the future prospect of porous ZnO nanostructures in TDD.

Novel fluorescent matrix embedded carbon quantum dots for the production of stable gold and silver hydrosols

A facile one step route has been developed for the synthesis of highly fluorescent matrix embedded carbon quantum dots (MCQDs) by the assistance of microwave irradiation. The material shows a homogeneous distribution of carbon quantum dots throughout the surfaces of the carbon matrices with an average size of 1 to 3 nm. The synthetic MCQDs can be employed as excellent catalysts during the synthesis of gold and silver nanoparticles.

Copper Nanoparticle (CuNP) Nanochain Arrays with a Reduced Toxicity Response: A Biophysical and Biochemical Outlook on Vigna radiata

Copper deficiency or toxicity in agricultural soil circumscribes a plants growth and physiology, hampering photochemical and biochemical networks within the system. So far, copper sulfate (CS) has been used widely despite its toxic effect. To get around this long-standing problem, copper nanoparticles (CuNPs) have been synthesized, characterized, and tested on mung bean plants along with commercially available salt CS, to observe morphological abnormalities enforced if any. CuNPs enhanced photosynthetic activity by modulating fluorescence emission, photophosphorylation, electron transport chain (ETC), and carbon assimilatory pathway under controlled laboratory conditions, as revealed from biochemical and biophysical studies on treated isolated mung bean chloroplast. CuNPs at the recommended dose worked better than CS in plants in terms of basic morphology, pigment contents, and antioxidative activities. CuNPs showed elevated nitrogen assimilation compared to CS. At higher doses CS was found to be toxic to the plant system, whereas CuNP did not impart any toxicity to the system including morphological and/or physiological alterations. This newly synthesized polymer-encapsulated CuNPs can be utilized as nutritional amendment to balance the nutritional disparity enforced by copper imbalance.

Efficacy of highly water-dispersed fabricated nano ZnO against clinically isolated bacterial strains

Versatile use of zinc oxide nanoparticles (ZNPs) in semiconductors, optical device and solar cells has already been established. Herein we describe synthesis of surface-functionalized ZNP to highly water dispersible constituent and its antibacterial efficiency against clinically isolated bacterial system. ZNP was synthesized by single-step microwave-assisted route using an aqueous buffer solution. Surface of ZNP was functionalized by grafting of phosphonoacetic acid as the coupling agent. Transmission electron microscopy image suggested that functionalized ZNP was smaller in size in comparison with unfunctionalized one. Antibacterial activity against clinically isolated bacterial strains of Escherichia coli, Staphylococcus aureus and Klebseilla sp. was detected with dose dependency. Functionalized ZNP claimed hexagonal crystal structure and exhibited higher dispersibility in aqueous solution which resulted in the production of greater reactive oxygen species and hence destruction of cell membrane leading to its biocidal efficacy. It is worth mentioning that functionalized dispersed fabricated ZNP would be used as potent biocides in medical as well as agricultural sector.