Pooja Devi

Selective electrochemical sensing for arsenite using rGO/Fe3O4 nanocomposites.

Herein, we report rGO/Fe3O4 nanocomposites (NCs) free from noble metals, synthesized by facile one step chemical reduction method, for electrochemical detection of arsenite in water by square wave anodic stripping Voltammetry (SWASV). The synthesized NCs were characterized for its optical, morphological and structural properties. The NCs modified glassy carbon (GCE), NCs/GCE, electrodes showed a higher sensitivity (0.281μA/ppb) and lower LOD (0.12ppb) under optimized experimental conditions. The proposed NCs/GCE electrodes show no interference towards arsenite species in the presence of common cationic interferants, namely, Cu(II), Pb(II), Ni(II), Co(II), Cd(II), Cr(II), Zn(II), etc. In addition, the proposed electrode demonstrates a good stability, reproducibility and potential practical application in electrochemical detection of arsenite.

Waste derivitized blue luminescent carbon quantum dots for selenite sensing in water

Herein, we report an environmental friendly, facile, and completely green synthetic method for producing carbon quantum dots (CQDs) from whey, a major dairy waste. The as-prepared monodispersed diameter CQDs exhibit blue luminescence with noteworthy quantum yield (~11.4%) and excitation dependent emission behaviour. Nuclear magnetic resonance (NMR) analysis reveals the presence of aromatized carbon peaks, leading to polymerized CQDs diameter architecture during whey pyrolysis. The X-ray and selected area electron diffraction patterns confirm their amorphous nature. Further, we demonstrate, these CQDs as an effective sensor probe for selective selenite monitoring in water upon functionalization with appropriate ligand. The functionalized GCQDs probe is shown to detect selenite with high sensitivity in 10-1000ppb detection range. Further it is selective for selenite over other relevant ions (such as Cu2+, As3+, As5+, Pb2+, Ni2+, Se6+, Cl-, Br-, NO3-, NO2- and F-) and displays a sub-ppb detection limit at 1.1% relative standard deviation.

Ultrasensitive and Selective Sensing of Selenium Using Nitrogen-Rich Ligand Interfaced Carbon Quantum Dots

This work reports a label-free, ultrasensitive, and selective optical chemosensory system for trace level detection of selenite (SeO32-), the most toxic form of selenium, in water. The probe, i.e., carbon quantum dots (CQDs), is designed from citric acid by means of pyrolysis and is interfaced with a newly synthesized nitrogen-rich ligand to create a selective sensor platform (functionalized CQDs, fCQDs) for selenite in a water matrix. Spectral (NMR, UV-vis, photoluminescence, Raman, and Fourier transform infrared analyses) and structural (high-resolution transmission electron microscopy) characteristics of the designed new probe were investigated. The developed sensor exhibits high sensitivity (limit of detection = 0.1 ppb), a wide detection range (0.1-1000 ppb range, relative standard deviation: 3.2%), and high selectivity even in the presence of commonly interfering ions reported to date, including Cl-, NO3-, NO2-, Br-, F-, As(V), As(III), Cu2+, Pb2+, Cd2+, Zn2+, Sr2+, Rb2+, Na+, Ca2+, Cs+, K+, Mg2+, Li+, NH4+, Co2+, etc. The observed selectivity is due to designed ligand characteristics in terms of strong Se-N chemistry. Ultrafast spectroscopic analysis of the fCQDs in the absence and presence of selenite was studied to understand the sensing mechanism. The sensor was successfully exemplified for real water samples and exhibits comparative performance to conventional ion channel chromatography as well as flame atomic absorption spectroscopy for selenite analysis. The promising results pave ways for realization of a field deployable device based upon a developed probe for selenite quantification in water.

Synthesis of silica/Au core- shell nanostructures by galvanic replacement of silica/Ag in aqueous and alkaline medium

We present here a facile one-step method for the synthesis of silica/Au core-shell nanostructures by exploiting the potential difference of AuCl4− and Ag in aqueous as well as alkaline media. Initially, silica/Ag core-shell nanostructures were synthesised by coating Ag nanoparticles on silica core (size ∼150 nm) in a two-step process (seeding and growth) and were characterised for their morphological, structural and optical behaviours. A complete coverage of silica core with Ag nanoparticles was seen from scanning electron microscope and transmission electron microscope images. The presence of resonance peaks in the optical spectrum manifests the nature of the shell (thin shell ∼413 and 650 nm, thick shell ∼434 nm). Galvanic replacement of silica/Ag core-shell nanostructures in chloroauric acid solution (HAuCl4) was studied in both the aqueous and alkaline medium, where an aqueous environment results into fast and effective replacement as compared to an alkaline medium, which has been confirmed from optical absorption studies. The optical studies showed that in an alkaline environment, on galvanic replacement of Ag with Au, the individual absorption peak of Ag (∼414 nm) and Au (∼520 nm) disappeared, whereas new absorption wavelengths in higher region (600–800 nm) of electromagnetic spectrum were observed. A detailed mechanism is proposed for the same to explain this behaviour. A range of novel new plasmonic core-shell nanomaterials can be synthesised as an intermediate of this facile one-step reaction.

Metal ion sensing and light activated antimicrobial activity of aloe-vera derived carbon dots

Carbon dots (CDs) have emerged out as a potential material amongst the carbon family for a wide range of applications including chemical/biological sensing, photocatalysis, bioimaging, etc. The green synthesis of these CDs from natural sources is gaining the significant interest of peer community for their wide utility. Herein, we present a facile one-step pyrolysis method for CDs synthesis from Aloe-Vera extract, which show bright blue luminescence under UV light with a quantum yield of 12.3%. Further, ex-situ morphological, structural and optical characterizations reveal their high quality and excitation independent emission behavior with the presence of carboxyl, hydroxyl functional groups. Furthermore, these CDs were studied for Fe(III) sensing in water without any surface modifications and assessed for their light activated antibacterial activity against E.Coli and Staphylococcus aureus.

Can Yoga-Based Diabetes Management Studies Facilitate Integrative Medicine in India? Current Status and Future Directions

Background: India is fast becoming the diabetic capital in the world according to a recent report. Patients with diabetes are at increased risk of mortality due to diabetic complications, which has enormous implications for the health budget. Objectives: The main objective of this review is to provide an overview of the work carried out in the world, including modern and traditional approaches for the prevention and management of diabetes and reducing the chances of onset of further complications via cost-effective lifestyle interventions and integrative medicine. Material and Methods: We performed a literature search from various databases like PubMed, Scopus, Google scholar, etc., using the keywords diabetes, prediabetes, MCI and prediabetes, diabetes and yoga, diabetes. Results: Upon reviewing the published articles, it was noticed that one of the most neglected complications of diabetes, namely cognitive dysfunction, which is characterized by a pattern of vascular dementia and Alzheimer disease (AD), has been largely ignored, and there has been no large study investigating the role of yoga intervention in diabetes and/or associated cognitive impairment. Conclusion: The review article opens new paradigms for researchers to evaluate the connection between diabetes and AD through a yoga-based national campaign on diabetes. This paves the way towards the goal of integrative medicine.

Formation of low-dimensional GaN on trenched Si(5 5 12), probed by STM and XPS

We report the formation of self-assembled nanostructures of GaN, with controlled size and shape on the trenched planar Si (5 5 12) surface. Adsorbing low coverages of Ga on Si (5 5 12) forms 1D arrays of Ga adatoms. The Ga adsorbed Si surface is annealed to 300 °C, which results in the formation of Ga 2D nanoparticles (NPs). These Ga NPs were exposed to various fluence of energetic 2 keV ions followed by annealing which yields GaN nanostructures self-assembled along the direction. These studies were performed in ultrahigh vacuum using in situ scanning tunneling microscopy and ex situ x-ray photoelectron spectroscopy, to observe the structural and chemical evolution of the interface.

Novel carbon/manganese oxide nanocomposite for electrochemical detection of arsenic in water- a step towards portable real time sensor

Arsenic (As), is a worldwide societal & environmental threat and therefore requires continuous monitoring in the natural water resources. Although, many opto/electrochemical techniques based on, macro, micro and nanostructures have been developed for the detection of As3+ ions, with advantages of high selectivity, sensitivity, and fast response. Yet, most of them are commercially unavailable, expensive and requires harsh operational conditions. Herein, we report ours first results on novel nanocomposite (NC) material, reduced graphene oxide (rGO)/manganese oxide (MNO2), for sensitive and selective detection of As (III) in water. The novel MnOx/rGO nanocomposite based working electrode is fabricated by one step electrochemical reduction method and characterized for its optical, structural and electrical properties. Results demonstrated a reduction peak at -1.4 V in sodium sulfate electrolyte, confirming simultaneous reduction of manganese and grapheme oxide (GO) on GO modified glassy carbon electrode. Preliminary sensing results revealed, sensitivity of fabricated electrode towards As (III) by appearance of stripping peak at ~ 0.26 V in square wave anodic stripping voltammetry (SWASV). Furthermore, sensing parameters such as time, pH, and deposition potential are optimized, which are recorded to design a portable embedded system for As (III) sensing.

Isotherm behavior studies of silica nanoparticles: Role of surfactant concentration and particle size

In the present work, the effect of the surfactant concentration and particle size on the 2D assembly and corresponding isotherms of the silica nanoparticles at the air/water interface is studied and reported using Langmuir-Blodgett (LB) technique. Silica nanoparticles (NPs) of different sizes (30 nm & 150 nm) were synthesized by Stöbers method and were characterized to determine their sizes and dispersity using scanning electron microscopy. As-synthesized NPs were hydrophobized to varying extents through addition of varying amounts (0.5 mg to 1.5 mg) of cationic surfactant, cetyltrimethylammoniumbromide (CTAB). The lift off area (area/particle) and corresponding yield was found to be very low for 30 nm sized particles. The yield in case of 150 nm sized particles participating in monolayer formation is found to be much higher implying a more optimal interaction with surfactant in the studied concentration range. The low yield at small particle size can be attributed to the partial surface modification of particles.