Samadhan P. Pawar

A quantum dot-based dual fluorescent probe for recognition of mercuric ions and N-acetylcysteine: “On–Off–On” approach

A mercaptopropionic acid-capped cadmium sulfide quantum dot (MPA-CdS QD) based dual fluorescent “On–Off–On” probe was designed and applied for sensitive and selective monitoring of mercuric ions (Hg2+) and N-acetylcysteine (NAC) in aqueous solution. In the mercuric ion detection, the fluorescence of MPA-CdS QDs decreased with increasing amount of Hg2+. This is because of the binding of mercuric ions to mercaptopropionic on the surface of quantum dots and the electron transfer from the photoexcited MPA-CdS QDs to mercuric ions. Subsequently, upon the successive addition of NAC, the fluorescence of MPA-CdS QDs is recovered due to the high binding affinity of NAC with mercuric ions; NAC can form a more stable complex with mercuric ions in aqueous solution, and this releases the fluorescent MPA-CdS QDs. The strategy was simply achieved by measuring the changes in the fluorescence intensity of QDs. The present results suggest that the developed method has several advantages such as being simple, straightforward, and highly sensitive, ease of operation and cost effectiveness and is used for simultaneous determination of two analytes in aqueous media. The linear response range was obtained over the range of 25–225 ng mL−1 and 0.05–0.9 μg mL−1 with a low detection limit of 25.2 ng mL−1 and 0.092 μg mL−1 for Hg2+ ions and NAC, respectively. The developed probe was successfully applied for the determination of Hg2+ and NAC in real samples with satisfactory results.

Synthesis of nickel sulfide as a promising electrode material for pseudocapacitor application

In the present investigation, in addition to pseudocapacitor application, the growth of interconnected nanorods/nanoplates of nickel sulfide (NiS) on a titanium (Ti)-substrate has been explored. An additive-free synthesis is performed by using a simple chemical bath deposition method. Structure and morphology of as-prepared NiS films are characterized by various characterization techniques such as X-ray diffraction, field effect scanning electron microscopy, high resolution transmission electron microscopy, and selected area electron diffraction etc. Electrochemical properties of the NiS thin film electrodes are studies by means of cyclic voltammetry and galvanostatic charge–discharge spectra obtained in 1 M aqueous KOH electrolyte. The NiS electrode demonstrates the notable pseudocapacitive activities including high specific capacitance (788 F g−1 at 1 mA cm−2), good rate capability (640 F g−1 at 50 mA cm−2), excellent cycling stability (98% retention after 1000 cycles) and high energy density (27.4 W h kg−1) as well as good power density (3.05 kW kg−1). Such an empirical performance is mostly due to the interconnected-type surface of NiS, which provides fast electron and ion transport. The obtained results indicate that the NiS thin film is a capable candidate as an electrode material for supercapacitor application.

CdS nanocrystals as fluorescent probe for detection of dolasetron mesylate in aqueous solution: Application to biomedical analysis

A simple and straightforward method for the determination of dolasetron mesylate (DM) in aqueous solution was developed based on the fluorescence quenching of 3-Mercaptopropionic acid (MPA) capped CdS quantum dots (QDs). The structure, morphology, and optical properties of synthesized QDs were characterized by using UV-Vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. Under the optimum conditions, the MPA-CdS QDs fluorescence probe offered good sensitivity and selectivity for detecting DM. The probe provided a highly specific selectivity and a linear detection of DM in the range of 2–40 µg/mL with detection limit (LOD) 1.512 µg/mL. The common excipients did not interfere in the proposed method. The fluorescence quenching mechanism of CdS QDs is also discussed. The developed sensor was applied to the quantification of DM in urine and human serum sample with satisfactory results.