Dr Nimai Mishra, Assistant Professor, Department of Chemistry, SRM University-AP, Andhra Pradesh, along with his research group comprising of students pursuing PhD under him, Ms V.G.Vasavi Dutt and Mr Syed Akhil has published a research article titled Cesium Lead Bromide Perovskite Nanocrystals as a Simple and Portable Spectrochemical Probe for Rapid Detection of Chlorides in the Journal ChemistrySelect (Publisher: Wiley-VCH on behalf of Chemistry Europe, Impact Factor-2.2).

Chloride anions are widely abundant in water and when they combine with calcium, potassium, and magnesium, they form chloride salts. However, the higher concentrations badly affect the environment by causing severe dehydration and even plant death. High concentrations of sodium chloride exhibit the potential of corrosive damage thereby releasing toxic metals from plumbing fixtures. Hence, there is a need to monitor the concentration levels of chloride salts in water. Several techniques like titration, spectrophotometry, ion chromatography, electrochemistry, etc have been reported to date. Despite the high accuracy and precision of these techniques, they involve expensive instrumentation and is out of reach from on-site detection. Hence, it is necessary to look for simple, portable, and cost-effective strategies for the detection of chlorides in the water.

In this article, Dr Mishra’s research group demonstrated that the wide spectral tunability of CsPbBr3 perovskite nanocrystals (NCs) via instantaneous and facile anion exchange, make them a suitable candidate for chloride detection. Rapid anion-exchange processes between CsPbBr3 perovskite NCs and different chloride solutions were carried out in ambient conditions. The resultant anion-exchanged CsPbCl3-xBrx NCs preserved the structural properties and exhibited a remarkable blue shift in photoluminescence spectra. This forms a basis for the detection of chloride ions in water. This has been applied with the limit of detection up to 100 µM. The detection strategies were not only limited to the direct addition of chloride solutions to NCs, but they also showed a visual colour change under UV light when the chloride solution is drop-casted on CsPbBr3 films that are deposited on glass substrates. Furthermore, the detection strategy is established by drop-casting CsPbBr3 NCs onto paper strips that are pre-soaked in chloride solutions. A considerable blue shift in fluorimetry proves them to be an excellent sensing medium as practical spectrochemical probes for on-site detection of chlorides. Based on this, a colour chart and selectivity chart to access the presence of chlorides and their concentration is also demonstrated.

Read the full paper here

SRM University-AP could not be more proud to announce that Dr S Mannathan, Head of Department of Chemistry has made it to the top 5% in the list of the Most Cited Authors by the Royal Society of Chemistry. It is inspiring to have a faculty member in our midst whose work has helped and facilitated the research of so many others.

Dr Mannathan obtained his doctorate from National Tsing Hua University, Taiwan. His research interests primarily lie in Metal-catalyzed organic transformation reactions, Multicomponent reactions, and Asymmetric synthesis. His research followed by scientists all over the world leading him to become one of the top 5% authors in terms of citations

In the field of Transition Metal Complexes as Catalysts in Organic Reactions, he particularly leans towards ‘Nickel-and cobalt-catalyzed three-component coupling and reductive coupling reactions’, and ‘Palladium-catalyzed reductive arylation’. Similarly, in Asymmetric Synthesis, he favours research into ‘Asymmetric reductive Heck reaction for the synthesis of chiral indanones’, and ‘Synthesis of bicyclic tertiary alcohols and its related asymmetric version via reductive [3+2] cycloaddition reaction by using chiral cobalt complexes.’

About the top 5% most cited paper:

In this work, he reported the synthesis and application of a Zn-Bp-BTC MOF (Bp – 4,4′-bipyridine; BTC – 1,3,5-benzene tricarboxylic acid; MOF – metal organic framework) as a heterogeneous catalyst for mediating organic reactions. Initial reaction conditions were optimized for the Knoevenagel condensation reaction using Zn-Bp-BTC as a heterogeneous catalyst. Various factors such as the effect of solvent, temperature and catalyst loading were evaluated. Although the reaction proceeded at room temperature using methanol as the solvent, 60 °C offered the best yield in a shorter duration. Under optimized reaction conditions, a wide range of α,β-unsaturated dicyano compounds were prepared from the corresponding carbonyl precursor and malononitrile, the active methylene counterpart. A systematic investigation was also carried out to assess the role of the ligand and metal salt in the Knoevenagel condensation reaction. It was found that the Zn-Bp-BTC MOF catalyzed the reaction efficiently in comparison to its analogue Zn-BTC MOF and precursor Zn(NO 3 ) 2 ·6H 2 O. Finally, catalytic recycling and stability studies showed that the catalyst is able to mediate the reaction for up to five consecutive cycles without undergoing any significant chemical or morphological changes. Further, the catalyst was tested for its efficacy in a multicomponent reaction (MCR). An MCR with the Zn-Bp-BTC MOF as the catalyst afforded good yields and there was no reaction in the absence of the catalyst. Similarly, the catalyst was tested for its efficiency in benzimidazole synthesis.

Dr Mannathan did this research in collaboration with Dr. Kathiresan Murugavel, Scientist, Electro Organic Division, CSIR-Central Electrochemical Research Institute (Govt of India), Karaikudi.

SRM University-AP is pleased to announce that Dr Nimai Mishra, Assistant Professor, Department of Chemistry, SRM University-AP, Andhra Pradesh, along with his research group comprising of students pursuing PhD under him, Mr Rahul Singh, Mr Syed Akhil, and Ms V.G.Vasavi Dutt, has published a research article titled “Shell thickness-dependent photostability studies of green-emitting “Giant” quantum dots” in the journal Nanoscale Advances (The Royal Society of Chemistry) with an impact factor of ~4.533.

About the research:

Highly efficient green-emitting core/shell giant quantum dots have been synthesized through a facile “one-pot” gradient alloy approach. Furthermore, an additional ZnS shell was grown using the “Successive Ionic Layer Adsorption and Reaction” (SILAR) method. Due to the faster reactivity of Cd and Se compared to an analogue of Zn and S precursors it is presumed that CdSe nuclei are initially formed as core and gradient alloy shells simultaneously encapsulate the core in an energy-gradient manner and eventually thick ZnS shells were formed. Using this gradient alloy approach, we have synthesized four different sized green-emitting giant core-shell quantum dots to study their shell thickness-dependent photostability under continuous UV irradiation, and temperature-dependent PL properties of nanocrystals. There was a minimum effect of the UV light exposure on the photostability after a certain thickness of the shell. The QDs diameter of ≥ 8.5 nm shows substantial improvement in photostability compared to QDs with a diameter ≤ 7.12 nm when continuously irradiated under the strong UV light (8 W/cm2, 365 nm) for 48 h. The effect of temperature on the photoluminescence intensities was studied with respect to shell thickness. There were no apparent changes in PL intensities observed for the QDs ≥ 8.5 nm, on the contrary, for example, QDs with < 8.5 nm in diameter (for ~7.12 nm) show a decrease in PL intensity at higher temperatures ̴90°C.

More importantly, these results highlight the synthesized green-emitting gradient alloy QDs with superior optical properties can be used for highly efficient green emitters and are potentially applicable for the fabrication of green LEDs.

Read the full paper: https://pubs.rsc.org/en/content/articlelanding/2021/NA/D1NA00663K

The Department of Chemistry is glad to announce that Dr J P Raja Pandiyan has published a paper titled ” Microfluidics and surface-enhanced Raman spectroscopy, a win-win combination?” in the journal ‘Lab on a Chip’ having an impact factor of 6.79 in collaboration with researchers from different universities across India, Germany, and Japan.

Abstract of the Research

With the continuous development in nanoscience and nanotechnology, analytical techniques like surface-enhanced Raman spectroscopy (SERS) render structural and chemical information of a variety of analyte molecules in ultra-low concentration. Although this technique is making significant progress in various fields, the reproducibility of SERS measurements and sensitivity towards small molecules are still daunting challenges. In this regard, microfluidic surface-enhanced Raman spectroscopy (MF-SERS) is well on its way to join the toolbox of analytical chemists. This review article explains how MF-SERS is becoming a powerful tool in analytical chemistry. We critically present the developments in SERS substrates for microfluidic devices and how these substrates in microfluidic channels can improve the SERS sensitivity, reproducibility, and detection limit. We then introduce the building materials for microfluidic platforms and their types such as droplet, centrifugal, and digital microfluidics. Finally, we enumerate some challenges and future directions in microfluidic SERS. Overall, this article showcases the potential and versatility of microfluidic SERS in overcoming the inherent issues in the SERS technique and also discusses the advantage of adding SERS to the arsenal of microfluidics.

About the Raman Research Group at SRM AP

Raman spectroscopy, invented by Sir CV Raman in 1928 and got Nobel Prize in 1930, is a vibrational spectroscopic technique that works based on the principle of inelastic scattering of light. Surface-Enhanced Raman spectroscopy (SERS) is one of the modern analytical techniques which can detect chemical and biomolecules in an ultra-low concentration. The research group is working on the development of the SERS technique to address the issues in food, environmental, energy and biological science.

The newly developed SERS substrates are mainly used for the detection of biological samples for disease diagnosis, food samples to ensure food safety, water samples to study the contamination and pollution rate. These studies can make meaningful social changes and improvements.