Department of Chemistry

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, have published a research article titled “Study of Shell Thickness Dependent Charge Transfer Dynamics in Green Emitting Core/Shell Giant Quantum Dots” Nature Index journal, “Inorganic Chemistry” published by The American Chemical Society having an impact factor of 5.1.

About the paper:

The superior photostability enables green-emitting graded alloy core/shell giant quantum dots (g-QDs) for optoelectronic application. However, it is essential to understand how the shell thickness affects interfacial charge separation. This work explores the impact of shell thickness on photoinduced electron transfer (PET) and photoinduced hole transfer (PHT) with an electron acceptor benzoquinone and a hole acceptor phenothiazine, respectively. The four graded alloy core/shell green-emitting g-QDs with different shell thicknesses were synthesised. The PET and PHT rate constants were obtained from photoluminescence and PL-lifetime decay measurement. Our study concludes that g-QDs with a diameter ~7.14 show a substantial improvement in charge transfer than g-QDs ≥ 8.5 nm in diameter. Similarly, the PET and PHT rates are 3.7 and 4.1 times higher for 7.14 nm g-QDs than for the 10.72 nm sample. The calculated electron and hole transfer rate constant (ket/ht) of g-QD with 7.14 nm in diameter are 10.80 × 107 s-1 and 14 × 107 s-1, which shows 8.5 and 8 times higher compared to g-QDs with a 10.72 nm in diameter.

Industrial implications:

More importantly, these results highlight the impact of shell thickness on the excited state interactions of green-emitting g-QDs and conclude that g-QDs with a relatively thin shell can be a better choice as photoactive materials for photocatalysts, photodetectors, and solar cells.

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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

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 honoured to host Dr Satheesh Ellipilli as a DST- Ramanujan Fellowship Faculty and facilitate his research for the next five years.

Ramanujan Fellowship is one of the most prestigious scientific fellowships that is offered to the Indian scientists working abroad. This fellowship is offered by Science and Engineering Research Board (SERB) to encourage scientists of Indian origin to return and research in an Indian institute/University.

SERB offers the scientists Rs 1,35,000/- per month along with research grant of Rs 7,00,000/- per annum and Rs 60,000/- per annum for overhead charges.

Dr. Satheesh Ellipilli obtained his PhD from Indian Institute of Science Education and Research, Pune. He worked as a postdoctoral researcher in The Ohio State University (Columbus, USA), Emory University (Atlanta, USA), and The University of Utah (Salt Lake City, USA).

Dr. Satheesh Ellipilli has extensive experience in the field of nucleic acid chemistry, particularly, focusing on utilization of RNA nanotechnology for cancer therapy using RNAi therapeutics in combination with small molecule drugs.

He has made numerous publications in some of the most renowned journals like Journal of Organic Chemistry, Journal of Controlled Release, Chemical Communications, Bioconjugate Chemistry, Organic and Biomolecular Chemistry, and Chemical Review to name a few.

Having Dr Ellipilli with us for the duration of his fellowship is a golden learning opportunity and a pleasure to be the host institution for his work. We hope that our students and scholars develop stronger research ethics and acumen in his company.