My active research works are related to:

# Long-range interaction between exciton-polariton condensates,

# Non-dissipative single-molecule-detection,

# Dynamic heterogeneity of protein, 

# Opto-mechano-electronics of  2D materials, 

# Single-molecule nanofluidics, 

# Persistent-current in resistive nanomaterials.

Single-electron controlled motion of single molecules

In the domain of single-molecule dynamics, we investigate the impact of electrostatic forces on molecular motion. Our study delves into the interplay between quantum mechanics and electrostatic interactions, resulting in trajectories reminiscent of planetary motion and gravity-assisted acceleration. By employing state-dependent diffusion and Green's functions, we establish a robust theoretical foundation that explains quantum control over molecules. We find that surface charge density critically influences diffusion coefficients, following linear scaling similar to Coulombic forces. Our research extends the range of observed diffusion coefficients, reaching up to 6000 μm^2/ms. These findings have practical applications in materials science and molecular engineering. This study advances our understanding of molecular motion and highlights the potential for precise control over single-molecule dynamics through quantum manipulation-an exploration at the nanoscale. [Verma et al. 2023]

Single-molecule nanofluidics

Trapping single molecule in liquid solution is challenging due to their fast diffusion (for eg. Rhodamine 6G, an organic dye molecule's diffusion coefficient is ~280 µm^2/s). We have built a modified version of anti-Brownian electro kinetic trap and tried to trap single molecules.  Despite various efforts, trapping of a single molecule cannot be achieved for prolonged duration [Kumbhakar et al. 2014].  We decided to bring some extra muscles in the fluidic system, which will not allow the single molecule to go out of detection volume. Suppressing the diffusion in two dimensions and keeping one dimension free for mobile single molecules were required for this. Developing such fluidic system was not straightforward because the fluidic channels should have a diameter much less than the focal diameter i.e. the detection region (minimum of 400 nm). I have developed a nanofabrication method which is capable of producing multiple nanofluidic channels simultaneously with a diameter ranging from 30 nm to 100 nm. I have successfully performed single molecule experiment inside these nanochannels [Ghosh et al. 2020] 

Single-photon emissions

Single photon sources can be identified not only by photon antibunching but also by defocused imaging. Previously, we found using defocused imaging that carbon nanodots and ZnO nanorods show single-photon emission behaviour using defocused imaging. Defocused imaging is also useful to identify the orientation of the dipole or in other words orientation of nanomaterials. Information on the orientation of nanomaterials is not only useful to the electrodynamic interaction at the surface but also useful in manipulating the sensing or detection efficiency (from the biomolecular sensing perspective). 

Molecular quantum mechanics of light-matter interactions  

We used time-dependent density functional tight-binding calculation (TD-DFTB) to identify the structure of the atomic structure of the carbon nanodots with single-photon emission behaviour. We named a particular kind of carbon nanodots as graphene quantum dots (GQD). The photophysical behaviour of GQD shows a significant dependence on its structure (edge termination, shape, and number of atoms).

Nanomechanics

Solid state

We created a novel ZnO nanorods which show ultra-high piezoelectric as well as ferroelectric behaviour (ZnO is intrinsically a non-ferroelectric material with density functional piezoelectric response). While studying their electromechanical behaviour of individual single ZnO nanorods, Dr Ghosh's nanorods repeatedly showed a significant discrepancy from earlier reports. With this motivation, we have recently shown that atomic defects play a significant role in the mechanics of nanostructures [Ghosh et al. 2016]. Our finding is based on atomic force microscopy, hight resolution transmission electron microscopy, and large-scale atomistic simulation. Until our study, the role of defects was neglected while studying single-crystalline nanomaterials. 

Soft-matter

We have developed an AFM correlated electron microscopy-based method to study the nanotribology of articular cartilage, which contains a fragile complex network collagen fibres [Ghosh et al. 2012]. The aim of the study was to avoid measuring measurement induced artefacts on the soft and complex surface of cartilage. We developed a three-dimensional image reconstruction technique which contains high-resolution information from electron microscopy. The nanoscale information provided by the method have a potential impact on the arthritis research.

PortOscope: Portable optical microscopy

For public awareness, forensic application, and to excavate the history of astro-optics, we are developing a portable microscope which I call Protoscope. The project involves serious research and scrutiny of various optical elements and mechanical designing where I intend to use structural optimisation.