Pallavi Singhal

U(VI) removal using cost-effective (production cost: $14.03 per kg), biocompatible, and superparamagnetic Cinnamomum tamala (CT) leaf extract-coated magnetite nanoparticles (CT@MNPs or CT@Fe₃O₄ nanoparticles) from water resources was studied. From pH-dependent experiments, the maximum adsorption efficiency was found to be at pH 8. Isotherm and kinetic studies were performed and found to follow Langmuir isotherm and pseudo-second order kinetics, respectively. The maximum adsorption capacity of CT@MNPs was calculated to be 45.5 mg of U(VI) per g of nanoparticles (NPs). Recyclability studies suggest that over 94% sorption was retained even after four consecutive cycles. The sorption mechanism was explained by the point of the zero-charge experiment and the XPS measurement. Additionally, calculations using density functional theory (DFT) were carried out to support the experimental findings.

Many applications of quantum dots (QDs); such as solar energy harvesting and toxic ion detection advice to understand the photoluminescence properties of QDs in water. However, this property can vary with concentration, purification and excitation wavelength which is seldom understood and can affect the above mentioned applications. The work carried out in this article demonstrates the effect and importance of these parameters on the photoluminescence properties of water dispersible CdSe/CdS core shell QDs. Three core shell QDs having the same core and shell thickness, but different number of ligands were synthesized. It was observed that the ligand concentration, excitation wavelength and concentration has a profound effect on the emission properties of QDs. The effect of above mentioned parameters on the detection of uranium by QDs was also discussed and it was shown that tuning these parameters can impact the detection limit drastically. A detection limit of 10 ppb was achieved by varying the experimental conditions which is much below than the limit prescribed by World Health Organization for uranium in drinking water suggesting the potential of these dots in sensing application and importance to tune different experimental conditions to achieve at a better detection limit.

Uranium is one of the most toxic and important elements present in the environment, and because of its high toxicity, ultra-trace-level detection is of utmost importance. Many methods were reported earlier for this purpose, but each has its own limitations such as high cost, sophisticated instrumentation, sample processing, and so forth. Herein we have demonstrated an alternate method that is much simpler and can be used for the ultra-trace-level detection of uranium. We have synthesized 3-mercaptopropionic acid (MPA)-capped CdSe/CdS core–shell quantum dots (CSQDs) and used its photoluminescence properties to detect uranium in solution. Steady-state emission studies suggest the luminescence quenching of CSQDs in the presence of uranium. Redox levels of CSQDs and uranium suggests that the electron-transfer process from photoexcited CSQDs to uranium is a thermodynamically viable process, which has subsequently been confirmed by time-resolved studies. A Stern–Volmer plot of CSQDs with uranium suggests that the detection limit of this method is 74.5 ppb. The method has an advantage over other reported methods for being simple and low cost and requiring a small amout of sample processing. To the best of our knowledge, we are reporting for the first time uranium detection using quasi-type II CSQDs and proposing the mechanistic path through luminescence spectroscopy, which in turn helps us to design an efficient detection method.