Huge Milestone for University: Six papers by Chemistry Department published in a single volume of ACS' Journal of Physical Chemistry Letters (Nature Index)

The Department of Chemistry at the School of Natural Sciences, Shiv Nadar Institute of Eminence (SNIoE) fosters a dynamic environment for innovative research and hands-on learning. Committed to advancing chemical knowledge and addressing societal challenges, the Department also ensures that the discoveries in its laboratories are disseminated through publication in respected peer-review journals. Of course, anyone familiar with academic publishing knows how competitive this environment is, and how hard it is to get a paper published. This makes the Department’s most recent milestone—having six papers accepted for publication in the same volume of ACS Journal of Physical Chemistry Letters—all the more impressive.

Two of these papers are co-authored by Dr. Debdas Ray, Associate Professor, SNIoE. In the first paper, alongside doctoral students Suvendu Dey, Raktim Deka, Manoj Upadhyay, and Sreerang Peethambaran at the Department of Chemistry, SNIoE, Dr. Ray has pursued a solution to a long-standing challenge in organic semiconductors: the emission of white light from a single component.

To date, white light emitters consist of mixtures of organometallic and/or organic compounds that emit light at different wavelengths. However, such emitters are difficult to design and produce since the energy transfer processes between compounds must be carefully considered and controlled.

To tackle this limitation, Dr. Ray and his team engineered an organic molecule, a phenothiazines−diphenyl quinoline conjugate, which emits white light through delayed fluorescence. This white light stems from two independent delayed emission channels, blue and orange in colour, that cover the entire visible spectrum of 410–800 nm. Worth noting, the proposed material can be synthesised at a low cost in ambient conditions, making it an attractive option for applications that require white light. “Ongoing research in white organic light emitting materials aims to revolutionise lighting technologies, potentially leading to widespread adoption of energy-efficient WOLED solutions and significant environmental benefits within the next decade,” remarks Dr. Ray.

His second paper, co-authored with Raktim Deka and Manoj Upadhyay of the Department of Chemistry, SNIoE, is about organic photothermal switching materials, which undergo reversible changes in response to specific light and heating. More specifically, the researchers focused on how to harvest energy from photoexcited triplet states in reversible manner as phosphorescence—a form of delayed emission in the order of microseconds to seconds. To date, such phenomena have not been reported in solid state due to limiting effects that occur in condensed states. Surprisingly, through strategic substitutions in organic compounds, Dr. Ray and colleagues demonstrated the first reversible ambient phosphorescence switching in a condensed state. “Photothermal switching materials could lead to reduced energy consumption in buildings, improved performance in electronics, and enhanced capabilities in data security technologies,” highlights Dr. Ray. “Ultimately, ongoing research in this field offers potential for transformative applications in energy efficiency and comfort, and could potentially revolutionise various aspects of daily life within the next decade.”

It is worth noting that the simultaneous publication of these two papers in ACS Journal of Physical Chemistry Letters marks yet another landmark in Dr. Ray’s career, following his two publications in Nature Indexed Journals in 2018. These accomplishments underline his consistent efforts and dedication to the field of physical chemistry, as well as his commitment to the mission of the Department of Chemistry at SNIoE.

The remaining four papers are co-authored by Dr. Tushar Debnath, a Ramanujan Fellow at the Department of Chemistry, SNIoE. They revolve around the various physical chemical aspects of perovskites—in particular, perovskite nanocrystals/quantum dots. “Quantum dots are tiny materials, only a few nanometres in size, that exhibit different colours based on their size and composition,” explains Dr. Debnath. “They serve as excellent probes for optoelectronic devices and light-emission applications like displays. Moreover, they absorb solar radiation in the entire UV-visible-NIR region, providing an excellent platform for photovoltaics and photocatalysis.”

Of the four papers Dr. Debnath has published, two are the result of collaborative work with Prof. Jochen Feldmann’s group at the Ludwig-Maximilians-Universität (LMU), Munich, Germany. In the first, Prof. Feldmann, Julian G. Mann, Fei He, Quinten A. Akkerman, and Dr. Debnath focus on Ag vacancies in Pb-free double perovskite nanocrystals and how they can create collective vibrations of the crystal lattice which they called ‘localised coherent phonons.’ They studied the different oscillatory modes of these vibrations, which arise after excited charge carriers become bound to Ag vacancies. Their experiments revealed that two phonon modes occur ‘in bulk,’ that is, as synchronised vibrations of the two types of perovskite atoms (Cs and Br) that modulate the bound states. Interestingly, they found that a third type of vibration was present, ascribed to a wave packet localised around Ag vacancies. Together, these phonon modes alter the absorbance profile of the perovskite crystal, which could lead to attractive applications. According to Dr. Debnath, “This optically induced and spatially localised lattice shaking could potentially be useful for initiating photochemical reactions with atomic precision.”

In their second paper, Dr. Debnath, Prof. Feldmann, Quinten A. Akkerman, and Patrick von Schwerin and Markus Döblinger of the Ludwig-Maximilians-Universität (LMU) investigated a promising technique to accurately control the size of spherical quantum dots generated in Mn-doped CsPbCl3 perovskite quantum dots. Through an innovative technique to incorporate the Mn ions into the perovskite, they managed to synthesise quantum dots with narrowly confined sizes, as small as 4 nm. By tuning the size of the quantum dots, they could fine-tune some of their optical properties, including their photoluminescence and absorption profiles. Such fine adjustments would be invaluable for the development of robust and high-quality materials for optoelectronic applications.

Dr. Debnath’s third paper, co-authored with Shamim H. Shah, a research fellow at the Centre for Nanotechnology, Indian Institute of Technology, Guwahati addresses the current lack of research on the nanoheterostructures of perovskite nanocrystals. To tackle this knowledge gap, the team fabricated quantum dot-based heterostructures out of perovskite/ternary chalcogenides and investigated how their energy and charge transfer properties changed depending on the halide used. The researchers remark that the halide-dependent controlled regulation of these properties in nanoarchitectures may find promising optoelectronic, catalytic, and sensing applications.

In the fourth and final paper, Dr. Debnath and his co-authors, Subhashree Sahu and Kalyanasis Sahu from the Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, have focused on turning what’s typically seen as a limitation of perovskites into a powerful tool. “Perovskites are extremely sensitive to water and moisture due to their soft and ionic crystal structure,” he remarks, “which imposes a serious limit on their commercialisation. However, we’ve come up with a way to use this water sensitivity constructively for the chemical transformation of perovskites on the nanoscale, realising tuneable optical properties.” Using reverse micelles as microscopic water containers, the team of researchers managed to transform CsPbBr3 to CsPb2Br5 in a highly controlled fashion, which would be impossible by simply exposing CsPbBr3 to water.

Together, these four groundbreaking studies on the physics and chemistry of perovskites will pave the way to advances in energy generation and storage technology, as well as precision chemical synthesis and catalysis. In particular, the field of solar energy harvesting could greatly benefit from perovskite research, which will be crucial in the ongoing worldwide transition to cleaner energy sources. Ecstatic about his and his colleague’s remarkable achievements, Dr. Debnath says, “Every physical chemist like me dreams of publication in the ACS Journal of Physical Chemistry Letters, which is among the top physical chemistry journals. Undoubtedly, having four papers in the same volume of the journal, all accepted in a span of just 33 days, is a priceless moment in my career. I am thankful to the Department of Chemistry for believing in me, and I would like to make a special mention of my students, colleagues, and collaborators, who were also part of this success.”

Let us congratulate these remarkable researchers for their ingenuity, their exceptional results, and their hard work, which combined have led to this memorable and impressive milestone.