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.

‘Energy Conversion & Management’ is a journal that belongs to the top 2% of the “Renewable Energy, Sustainability, and the Environment” subject category. Publishing a paper with an impact factor of 9.7 in such a journal is a considerable achievement. Assistant Professors Dr Sabyasachi Chakrabortty and Dr Mahesh Kumar Ravva and their PhD scholar Ms Mounika Sai Ambati from the Department of Chemistry have accomplished this by publishing a paper titled Photovoltaic/Photo-Electrocatalysis Integration for Green Hydrogen: A review in this Q1 journal.

Abstract of the research

Solar light-driven hydrogen generation via water splitting is essential to combat global warming and CO2 emission. The production of hydrogen from fossil fuels produces massive amounts of CO2. Developing a sustainable and eco-friendly approach to hydrogen production is the need of the hour. Photoelectrochemical water splitting is a clean way to produce hydrogen by using water. The hydrogen generated through water splitting is referred to as Green Hydrogen. Photoelectrochemical water splitting uses metal oxides as photocathode/anode. The challenges that occur here are stability, low efficiency, and large-scale development (reusable electrodes are essential). Hence, the primary goal is to demonstrate photoelectrodes using different metal oxides by in-situ doping of different metals to detect the challenges.

Cesium lead halide perovskite nanocrystals (PNCs) belong to the flourishing research area in the field of photovoltaic and optoelectronic applications because of their excellent optical and electronic properties. Mainly, Cesium lead bromide (CsPbBr3) NCs with bright green photoluminescence (PL) and narrow full-width at half-maximum (FWHM) of <25 nm are the most desirable for television displays and green-emitting LEDs. However, challenges with respect to CsPbBr3 PNCs‘ stability, limit their usage in practical applications. The recent findings of Dr Nimai Mishra and his research team assert that surface passivation with an additional ligand could be an excellent, easy, and facile approach to enhancing the photoluminescence and stability of PNCs.

Dr Nimai Mishra, Assistant Professor, Department of Chemistry, along with his research group comprising of students pursuing PhD under him, Dr V G Vasavi Dutt, Mr Syed Akhil, Mr Rahul Singh, and Mr Manoj Palabathuni have published their research article titled “Year-Long Stability and Near-Unity Photoluminescence Quantum Yield of CsPbBr3 Perovskite Nanocrystals by Benzoic Acid Post-treatment“ in The Journal of Physical Chemistry C (A Q1 journal published by ‘The American Chemical Society’) having an impact factor of ~4.2.

In this article, the research group addresses the stability issues of green-emitting CsPbBr3 PNCs with simple post-treatment using benzoic acid (BA). A remarkable improvement in PLQY from 69.8% to 97% (near unity) was observed in benzoic acid-treated CsPbBr3 PNCs. The effective surface passivation by benzoic acid is also apparent from PL decay profiles of BA-CsPbBr3 PNCs. The long-term ambient stability and stability against ethanol of BA-CsPbBr3 PNCs are also well presented in the research. The PL intensity of untreated CsPbBr3 PNCs is completely lost within five months since the synthesis date, while ̴ 65% of initial PL intensity is preserved for BA-CsPbBr3 PNCs even after one year.

Furthermore, BA-CsPbBr3 PNCs exhibits excellent photo-stability where 36% of PL is retained while PL is completely quenched when the PNCs are exposed to 24 hours of continuous UV irradiation. Importantly, BA-CsPbBr3 PNCs show excellent stability against ethanol treatment as well. Finally, green, emitting diodes using BA-CsPbBr3 PNCs are fabricated by drop-casting NCs onto blue-emitting LED lights. Thus a simple benzoic acid posttreatment further presents the scope of use of these materials display technologies.

Surface-enhanced Raman Spectroscopy (SERS) is a nuanced chemical technique that amplifies the Raman scattering of molecules by utilising plasmonic nanostructured materials. SERS operates as a powerful detection tool that allows for the structural fingerprinting of a molecule. The ultra-high sensitivity and selectivity of the process offer it a vast array of applications in surface and interface chemistry, nanotechnology, biology, biomedicine, food science, environmental analysis and other areas.

Dr J P Raja Pandiyan and his PhD scholar, Ms Arunima Jinachandran from the Department of Chemistry have been keenly involved in exploring the possibilities of SERS technology in food science and other fields. The safety and quality concerns related to food were the primary reasons that impelled them to step into this domain. Their article “Surface-enhanced Raman spectroscopy for food quality and safety monitoring” was published in the book Nanotechnology Applications for Food Safety and Quality Monitoring, published by Elsevier. The article was published in collaboration with Dr Selvaraju Kanagarajan from the Swedish University of Agricultural Sciences.

As an analytical technique, SERS possesses several advantages such as non-destructive, sensitive, and selective. In the chapter, the necessity, and applications of SERS in food science are elaborately discussed. They have also discussed all the possible food contaminants and how to identify them using SERS to ensure food quality. This book will serve as an enlightening read to research groups who are working on Raman, surface-enhanced Raman spectroscopy, analytical chemistry, and food quality analysis.

The Department of chemistry has always been a dynamic space for innovative and inspiring research. Recently, Assistant Professor Dr Nimai Mishra published his fifteenth research paper from SRM university-AP as a corresponding author. The paper is titled Post-synthesis Treatment with Lead Bromide for Obtaining Near Unity Photoluminescence Quantum Yield and Ultra-Stable Amine Free CsPbBr 3 Perovskite Nanocrystal and is published in the Q1 journal, The Journal of Physical Chemistry C with an impact factor of 4.2. The research group is comprised of Dr Mishra’s PhD students Mr Syed Akhil, Dr V G Vasavi Dutt, and Mr Rahul Singh. This is the group’s fifth consecutive article published in the American Chemical Society.

About the article

The article reports Ultra-Stable and Near Unity Photoluminescence Quantum Yield Amine Free CsPbBr 3 Perovskite Nanocrystal Post-synthesis Treatment with Lead Bromide. Herein, the researchers have introduced a simple lead bromide (PbBr 2 ) post-treatment process to achieve the near-unity PLQY (>95 %) in amine-free CsPbBr 3 PNCs. Furthermore, PbBr 2 treatment enables these materials to drastically improve stability in different environmental conditions (polar solvents, light, and heat). In addition, a green-emitting down- converted light-emitting diode was fabricated using PbBr 2 treated amine-free CsPbBr 3 PNCs, which shows its considerable prospects for display applications. Thus, the results of the research will promote these PbBr 2 treated amine-free inorganic perovskite nanocrystals for commercial development in optoelectronic applications.

Explanation of the research

Cesium lead halide perovskite nanocrystals (PNCs) have been the flourishing area of research in the field of photovoltaic and optoelectronic applications because of their excellent optical and electronic properties. Mainly, cesium lead bromide (CsPbBr 3 ) NCs with bright green photoluminescence (PL) and narrow full-width at half-maximum (FWHM) of < 25 nm is the most desirable for television displays and green-emitting LEDs. Improving the photoluminescence quantum yields (PLQYs) and optimizing the stability have been challenging tasks to promote cesium lead halide (CsPbX3; X=Cl, Br and I) perovskite nanocrystals (PNCs) for real optoelectronic applications. In recent years, the amine- free synthesis route has become an option for making stable CsPbX 3 PNCs.

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