Debashis Bandyopadhyay

Deep-blue host materials for thermally activated delayed fluorescence (TADF) are usually ranked on a few molecular numbers, on the assumption that the isolated molecule anticipates the film. We test that assumption for three phosphine-oxide hosts, S1, S3 and S4, by reading protocol-locked descriptors of the dilute solution, the evaporated film, the powder and the bulk side by side, each with its uncertainty, next to a separate density-functional layer. The descriptors fall into families that rank the hosts differently: film-gap and thermal descriptors place the multi-arm S4 host first, emission and order descriptors place the compact carbazole S1 host first, and band-tail and voltammetric descriptors do not separate the two. The split appears between the molecule and the film: the two hosts emit alike as dilute molecules, yet the S4 film absorption edge lies 0.33 eV higher. Calculations validated against the measured infrared and NMR spectra show frontier levels that move far more with the functional than between hosts. Film gap and thermal robustness must therefore be measured and assessed separately from emissive quality.

Deep-blue host materials for thermally activated delayed fluorescence (TADF) are usually ranked on a few molecular numbers, on the assumption that the isolated molecule anticipates the film. We test that assumption for three phosphine-oxide hosts, S1, S3 and S4, by reading protocol-locked descriptors of the dilute solution, the evaporated film, the powder and the bulk side by side, each with its uncertainty, next to a separate density-functional layer. The descriptors fall into families that rank the hosts differently: film-gap and thermal descriptors place the multi-arm S4 host first, emission and order descriptors place the compact carbazole S1 host first, and band-tail and voltammetric descriptors do not separate the two. The split appears between the molecule and the film: the two hosts emit alike as dilute molecules, yet the S4 film absorption edge lies 0.33 eV higher. Calculations validated against the measured infrared and NMR spectra show frontier levels that move far more with the functional than between hosts. Film gap and thermal robustness must therefore be measured and assessed separately from emissive quality.

Janus Nb ₂ COS MXene exhibits excellent structural stability, low alkali-ion diffusion barriers, and high storage capacities, making it a promising anode material for next-generation Li-, Na-, and K-ion batteries.

We present the mechanical, electronic and optical properties of LAGO perovskite under an applied strain. The results are promising for solar cells and piezoelectric devices.

We report ab initio and model-Hamiltonian investigations of THz magnon propagation in a transition metal adatom decorated one-dimensional nanoscale strip derived from a holey graphyne (HGY) sheet. Using density functional theory (DFT) for the ab initio study of the system and then applying a tight binding model through Wannier functions, we obtain localized magnetic moments that can be studied using the Heisenberg spin model and linear spin wave theory. Our results show magnon propagation in the material with velocities reaching up to 5.5 km s⁻¹ along with bandgaps that can be tuned by up to 10% using an external magnetic field. These findings suggest that transition metal decorated one-dimensional HGY nanostrips act as atomically thin magnonic crystals with field tunable transmission bands, making them promising platforms for next-generation magnonic and wave-based computing devices operating in the terahertz range. Experimental realization through bottom–up synthesis, combined with spin wave spectroscopy or scattering measurements, could open new opportunities for exploring ultrafast spin dynamics in these materials.

We developed a hybrid ML-DFT framework for rapid screening of drug-nanomaterial interactions (MAE 0.075 eV, DFT-validated). PDOS/Bader analyses reveal charge transfer/coupling mechanisms, enabling scalable ML-driven nanomaterial therapeutics design.

Efficient identification of promising drug candidates for nanomaterial-based delivery systems is essential for advancing next-generation therapeutics. In this work, we present a synergistic framework combining density functional theory (DFT) and machine learning (ML) to explore the adsorption behavior and electronic interactions of drugs on a novel 2D graphene allotrope, termed Graphsene (GrS). Graphsene, characterized by its porous ring topology and large surface area, offers an excellent platform for efficient adsorption and strong electronic coupling with drug molecules. A dataset comprising 67 drugs adsorbed on various 2D substrates was employed to train the ML model, which was subsequently applied to predict suitable drug candidates for GrS based on molecular size and adsorption energy criteria (database link provided in a later section). The ML model exhibited robust predictive accuracy, achieving a mean absolute error of 0.075 eV upon DFT validation, though its sensitivity to initialization highlighted the need for larger and more diverse datasets. DFT-based analyses, including adsorption energetics, projected density of states (PDOS), and Bader charge calculations, revealed pronounced charge transfer and electronic coupling between the drug molecules and the GrS surface, elucidating the fundamental nature of drug-substrate interactions. The study reveals that the integrated DFT-ML strategy offers a rapid, cost-efficient approach for screening and understanding drug-nanomaterial interactions, paving the way for data-driven design of advanced nanomaterial-enabled drug delivery systems.

We present a first--principles density functional theory (DFT) study of transition metal (TM = Ti, Cr, Mn, Fe, Co, Ni) functionalized two--dimensional polyaramid (2DPA) to explore their structural, electronic, and magnetic properties. Mechanical parameters, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and Pugh ratio, together with phonon dispersion, confirm the mechanical and dynamic stability of all doped systems. Electronic structure analysis shows strong binding of Co, Cr, Fe, Ni, and Ti with formation energies between --1.15 eV and --2.96 eV, while Mn binds more weakly (--0.67 eV). TM doping introduces new electronic states that reduce the band gap, with Fe-doped 2DPA exhibiting the lowest value of 0.26 eV. The systems display predominantly ferromagnetic ordering, with magnetic moments of 1.14 μB (Co), 3.57 μB (Cr), 2.26 μB (Fe), 4.19 μB (Mn), and 1.62 μB (Ti). These results demonstrate that TM--doped 2DPA possesses tunable magnetic and electronic characteristics, highlighting its potential for spintronic applications.