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Siddharth Ghosh

Publications and source records attributed to Siddharth Ghosh.

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Single-molecule motion control

Achieving dynamic manipulation and control of single molecules at high spatio-temporal resolution is pivotal for advancing atomic-scale computing and nanorobotics. However, this endeavour is critically challenged by complex nature of atomic and molecular interactions, high-dimensional characteristics of nanoscale systems, and scarcity of experimental data. Here, we present a toy model for controlling single-molecule diffusion by harnessing electrostatic forces arising from elementary surface charges within a lattice structure, mimicking embedded charges on a surface. We investigate the interplay between quantum mechanics and electrostatic interactions in single molecule diffusion processes using a combination of state-dependent diffusion equations and Green's functions. We find that surface charge density critically influences diffusion coefficients, exhibiting linear scaling akin to Coulombic forces. We achieve accurate predictions of experimental diffusion constants and extending the observed range to values reaching up to 6000 $\mu\text{m}^2\text{ms}^{-1}$ and 80000 $\mu\text{m}^2\text{ms}^{-1}$. The molecular trajectories predicted by our model bear resemblance to planetary motion, particularly in their gravity-assisted acceleration-like behaviour. It holds transformative implications for nanorobotics, motion control at the nanoscale, and computing applications, particularly in the areas of molecular and quantum computing where the trapping of atoms and molecules is essential. Beyond the state-of-the-art optical lattice and scanning tunnelling microscopy for atomic/molecular manipulation, our findings give unambiguous advantage of precise control over single-molecule dynamics through quantum manipulation at the angstrom scale.

physics.atm-clus

Superfluidic nature of self-driven nanofluidics at liquid-gas interfaces

Self-driven nanofluidic flow at the liquid-air interface is a non-intuitive phenomenon. This flow behaviour was not driven by classical pressure difference or evaporation only. Depending on the position of the nanofluidic pore we can observe flow and no-flow with chaotic behaviour. In this paper, we study the nonlinear dynamics of a confined nanopore system at the liquid-air interface. The finite-range interactions between the interacting species are quantified with a corresponding critical velocity of the system. This is visualised using the finite element method and analysed mathematically with the Landau criterion. We found the formation of Bose-Einstein-like condensates due to the transport through nanofluidic pores. We show that systems with more than one nanofluidic pore with a sub-100 nm diameter create a highly nonlinear and complex. The approximation of relevant classical systems to existing quantum mechanical systems divulges new results and corrections at a fundamental level. We explain the formation of oscillating condensate within the system in the liquid phase. The high velocity near the specific boundaries of the system, the sudden disappearance of oscillations, and its dependence on evaporation are explored. This transition of classical mechanics with the outlook of quantum mechanics leaves several open questions for further investigation in the field of quantum nanofluidics.

quant-ph

Transport of aerosols and nanoparticles through respirators and masks

In several countries wearing multiple surgical masks or N95 respirators was mandatory in public during the COVID pandemic. In this study, we investigated the transportation and filtering mechanism of heterogeneous nanoparticles and viruses through surgical masks and N95 respirators. We conducted experiments in vitro using aerosol spray paints containing nanoparticles and validated the findings in vivo on a human volunteer. Scanning electron microscopy was employed to analyse the transportation and distribution of nanoparticles in different mask layers and on pristine silicon substrates placed on human skin. We provide analytical insights into the pressure distribution and fluid velocity profiles within the complex polymer network. Remarkably, our results showed that both single surgical masks and N95 respirators demonstrated similar efficiency in filtering colloidal and jet-stream nanoparticles in the air. These comprehensive findings have significant implications for policymakers in defining regulations for airborne pandemics and air pollution control.

physics.bio-ph

Feynman-Enderlein Path Integral for Single-Molecule Nanofluidics

Single-molecule motions in the nanofluidic domain are extremely difficult to characterise because of various complex physical and physicochemical interactions. We present a method for quasi-one-dimensional sub-diffraction-limited nanofluidic motions of fluorescent single molecules using the Feynman-Enderlein path integral approach. This theory was validated using the Monte Carlo simulation to provide fundamental understandings of single-molecule nanofluidic flow and diffusion in liquid. The distribution of single-molecule burst size can be precise enough to detect molecular interaction. The realisation of this theoretical study considers several fundamental aspects of single-molecule nanofluidics, such as electrodynamics, photophysics, and multi-molecular events/molecular shot noise. We study {molecules within (an order of magnitude of) realistic lengthscale for organic molecules, biomolecules, and nanoparticles where 1.127~nm and 11.27~nm hydrodynamic radii of molecules were driven by a wide range of flow velocities ranging from $0.01~μ$m/s to $10~μ$m/s. It is the first study to report distinctly different velocity-dependent nanofluidic regimes.

physics.atm-clus

Ageing related states of complex network formation in areca nuts

Complex pattern formation is an essential characteristic of plants and their ageing, growth, and evolution. Perception of these patterns is an intrinsic nature of plant-dependent animals for coexistence. Areca nut consisting of complex patterns is considered to be addictive for humans and has increased adverse health effects. However, no critical study is performed on the complex pattern of the areca nut. A large number of areca nuts has been studied since 2017 to develop a low-cost tool for the LMICs to categorise areca nuts. We present the first finding to identify similarities among complex networks of differently aged areca nuts by investigating the internal patterns of randomly chosen nuts from the same age group. We developed a smartphone camera-based high-resolution measurement with comprehensive biophysical mathematics and a quantum mechanical concept called density of states (DOS). We found that the DOS can provide a unique coefficient to represent age and ageing together using a single number. The average of these single numbers for less aged nuts and highly aged nuts are 4.9 and 3.8, respectively. If fruit looks aged from its external morphology as well as internal morphology, our method identifies the intrinsic similarities among the ageing networks without implementing any computationally expensive search algorithm. We show clear evidence of the diversity of ageing from relative and absolute colour vision perspectives. We have also conducted further analyses of local DOS, Fourier decomposition, correlation study, spectral decomposition, and structural similarity index.

physics.bio-ph

Active solid-state nanopores: Self-driven flows/chaos at liquid-gas nanofluidic interface

We present a study of self-driven flow dynamics at the liquid-gas interface within nanofluidic pores, devoid of any external driving forces. The investigation centres on the Rayleigh-Taylor instability phenomena occurring in sub-100 nanometre-scale fluidic pores situated within a micrometer-scale water and air domain. This research rigorously validates our flow velocity equation using simulation results while delving into the mass transfer efficiency of these intricate flow structures. Notably, we introduce a concept - an 'active solid-state nanopore' - that exhibits self-driven flow switching behaviour, transitioning between active and passive states without the need for mechanical components. This study reveals highly nonlinear and complex fluid dynamics within nanoscale dimensions, marking an exploration in this domain at room temperature. Implications of self-driven nanofluidics extend across diverse fields, from enhancing biosensors and healthcare applications to advancing net-zero sustainable energy production and contributing to the fundamental understanding of fluid dynamics in confined spaces.

physics.flu-dyn

Towards real-time oxygen sensing: From nanomaterials to plasma

A significantly large scope is available for the scientific and engineering developments of high-throughput ultra-high sensitive oxygen sensors. We give a perspective of oxygen sensing for two physical states of matters - solid-state nanomaterials and plasma. From single-molecule experiments to material selection, we reviewed various aspects of sensing, such as capacitance, photophysics, electron mobility, response time, and a yearly progress. Towards miniaturisation, we have highlighted the benefit of lab-on-chip-based devices and showed exemplary measurements of fast real-time oxygen sensing. From the physical-chemistry perspective, plasma holds a strong potential in the application of oxygen sensing. We investigated the current state-of-the-art of electron density, temperature, and design issues of plasma systems. We also show a numerical aspects of low-cost approach towards developing plasma-based oxygen sensor from household candle flame. In this perspective, we give an opinion about a diverse range of scientific insight together, identifies the short comings, and opens the path for new physical-chemistry device developments of oxygen sensor along with providing a guideline for innovators in oxygen sensing.

physics.chem-ph

High-throughput nanofluidic device for one-dimensional confined detection of single fluorophores

Ensemble averaging experiments may conceal many fundamental molecular interactions. To overcome that, a high-throughput detection of single molecules or colloidal nanodots is crucial for biomedical, nanoelectronic, and solid-state applications. One-dimensional (1D) discrete flow of nanoscale objects is an efficient approach in this direction. The development of simple and cost-effective nanofluidic devices is a critical step to realise 1D flow. This letter presents a nanofabrication technique using shadow-angle-electron-beam-deposition for a high-throughput preparation of parallel nanofluidic channels. These were used to flow and detect DNA, carbon-nanodots, and organic fluorophores. The 1D molecular mass transport was performed using electro-osmotic flow. The 1D flow behaviour was identified and analysed using two-focus fluorescence correlation spectroscopy (2fFCS). A range of flow velocities of single molecules was achieved. The transitions of single molecules or nanodots through the two foci were quantitatively analysed using confocal scanning imaging, correlative photon detection, and burst size distribution analysis. The results suggest an efficient nanofabrication technique is developed to prepare nanofluidic devices. This first demonstration of high-throughput nanochannel fabrication process and using 2fFCS-based single molecule flow detection should have a potential impact on ultra-sensitive biomedical diagnostics and studying biomolecular interactions as well as nanomaterials.

physics.bio-ph