Shubhadeep Pal

Bio: Shubhadeep Pal is an academic researcher from Tata Institute of Fundamental Research. The author has contributed to research in topics: Graphene & van der Waals force. The author has an hindex of 15, co-authored 32 publications receiving 641 citations. Previous affiliations of Shubhadeep Pal include Saha Institute of Nuclear Physics & Weizmann Institute of Science.

Hydrogen Evolution Reaction Activity of Graphene–MoS2 van der Waals Heterostructures

Abstract: Determining a suitable noble-metal-free catalyst for hydrogen evolution reaction (HER) by photoelectrocatalytic (PEC) water splitting is an enduring challenge. Here, the molecular origin of number of layers and stacking sequence-dependent PEC HER performance of MoS2/graphene (MoS2/GR) van der Waals (vdW) vertical heterostructures is studied. Density functional theory (DFT) based calculations show that the presence of MoS2 induces p-type doping in GR, which facilitates hydrogen adsorption in the GR side compared to the MoS2 side with ΔGH closer to 0 eV in the MoS2/GR bilayer vertical stacks. The activity maximizes in graphene with monolayer MoS2 and reduces further for bilayer and multilayers of MoS2. The PEC HER performance is studied in various electrodes, namely, single-layer graphene, single- and few-layered MoS2, and their two different types of vertical heterojunctions having different stacking sequences. The graphene on top of MoS2 sequence showed the highest photoresponse with large reaction curren...

Length-Dependent Electron Spin Polarization in Oligopeptides and DNA

Abstract: The effect of spin polarization in conduction and in electric field-induced polarization was measured for double-stranded DNA oligonucleotides and oligopeptides of different lengths. These measurem...

Transparent flexible lithium ion conducting solid polymer electrolyte

Abstract: Recent safety threats concerning conventional liquid electrolyte-based Li-ion batteries invoke the search for high ionic conductivity solid electrolytes (SEs) for solid state batteries. Here, the development of a multifunctional polymer SE (ionic conductivity ∼0.03 mS cm−1) is demonstrated and this SE is endowed with other exotic properties such as high Li-ion transport number (∼0.69) with large electrochemical window (2–5 V), high mechanical robustness and flexibility (Young's modulus ∼1 MPa), visible light transparency (∼85%), and hydrophobicity (contact angle > 100°). Here poly(ethylene oxide) (PEO) and polydimethylsiloxane (PDMS) based polymer complex serves as the Li-ion transport membrane, and lithium perchlorate (LiClO4) as the Li source. The ‘salting in’ phenomenon, induced by the ClO4−–PEO interactions, modifies the crystalline melting temperature of PEO leading to the amorphization of the PEO–PDMS matrix and hence to a high Li-ion conductivity by microstructure modifications. This transparent and flexible SE is shown for its applicability in flexible symmetric capacitors and Li-ion cells without the use of liquid electrolyte interfaces.

Fluorographene based Ultrasensitive Ammonia Sensor

Abstract: Single molecule detection using graphene can be brought by tuning the interactions via specific dopants. Electrostatic interaction between the most electronegative element fluorine (F) and hydrogen (H) is one of the strong interactions in hydrogen bonding, and here we report the selective binding of ammonia/ammonium with F in fluorographene (FG) resulting to a change in the impedance of the system. Very low limit of detection value of ~0.44 pM with linearity over wide range of concentrations (1 pM–0.1 μM) is achieved using the FG based impedance sensor, andthisscreen printed FG sensor works in both ionized (ammonium) and un-ionized ammonia sensing platforms. The interaction energies of FG and NH3/NH4+ are evaluated using density functional theory calculations and the interactions are mapped. Here FGs with two different amounts of fluorinecontents −~5 atomic% (C39H16F2) and ~24 atomic% (C39H16F12) - are theoretically and experimentally studied for selective, high sensitive and ultra-low level detection of ammonia. Fast responding, high sensitive, large area patternable FG based sensor platform demonstrated here can open new avenues for the development of point-of-care devices and clinical sensors.

Single-Atom Catalysts across the Periodic Table.

Abstract: Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

Vibrio Parahaemolyticus and Related Halophilic Vibrios

Abstract: Approximately 30 years have elapsed since Dr. Fujino's original discovery that Vibrio parahaemolyticus (then termed Pasteurella parahemolytica) was the cause of "summer diarrhea" in Japan. Since that finding, V. parahaemolyticus has been established as a cause of gastroenteritis in numbers and places approaching global proportions. It has been isolated in marine and estuarine areas almost worldwide and despite its halophilic nature, V. parahaemolyticus has been isolated from saline-free waters. The relationship of this organism to the environment reveals a close association with other marine organisms especially copepods on which the Vibrios depend for survival in winter months and growth in summer months. There is a uniquely provocative disparity between human strains of V. parahaemolyticus which are Kanagawa phenomenon (KP) positive and the environmental strains which to a large extent are KP negative, the significance being that pathogenicity is measured according to the Kanagawa phenomenon (hemolytic activity) reaction. The hemolysin of the pathogenic strains is a thermostable, cardiotoxic protein, which thus far has not been implicated in the mechanism(s) which causes human gastroenteritis. The interest in this organism has been widened in recent years by the finding that similar organisms, V. alginolyticus, lactose positive vibrios and group F vibrios also cause serious disease in humans.

Safe water treatment and storage in the home. A practical new strategy to prevent waterborne disease.

Abstract: In many parts of the developing world, drinking water is collected from unsafe surface sources outside the home and is then held in household storage vessels. Drinking water may be contaminated at the source or during storage; strategies to reduce waterborne disease transmission must safeguard against both events. We describe a two-component prevention strategy, which allows an individual to disinfect drinking water immediately after collection (point-of-use disinfection) and then to store the water in narrow-mouthed, closed vessels designed to prevent recontamination (safe storage). New disinfectant generators and better storage vessel designs make this strategy practical and inexpensive. This approach empowers households and communities that lack potable water to protect themselves against a variety of waterborne pathogens and has the potential to decrease the incidence of waterborne diarrheal disease. ( JAMA . 1995;273:948-953)

Double Emulsion-Templated Nanoparticle Colloidosomes with Selective Permeability

Abstract: Colloidosomes are microcapsules whose shell consists of densely packed colloidal particles. Their physical properties such as permeability, mechanical strength, and biocompatibility can be precisely controlled through the proper choice of colloids and preparation conditions for their assembly. The high degree of control over their physical properties makes colloidosomes attractive structures for encapsulation and controlled release of materials ranging from fragrances and active ingredients to molecules produced by living cells. The conventional approach to preparing colloidosomes involves two steps: first, colloidal particles are introduced into the continuous phase of a water-in-oil emulsion. The particles self-assemble at the interface between the two immiscible liquid phases and form a colloidal shell structure. Subsequently, the colloidal shell structures, templated by the water droplets dispersed in the oil phase, are transferred to an aqueous phase either by centrifugation or repeated washing. This strategy has been used to create colloidosomes with particles ranging from 5 nm to several microns in diameter. The colloidosome structures must be mechanically stabilized to successfully transfer them into an aqueous phase; however, even with this stabilization, the transfer processes are not efficient, often leading to damage of the original structure. In addition, the size distribution of colloidosomes prepared by the conventional technique is rather broad, as polydisperse emulsions are typically used as templates. A narrow size distribution for colloidosomes is especially important for the encapsulation of active pharmaceutical ingredients where delivery of an exact amount is critical. Thus, it is important to develop a more convenient and direct means to create monodisperse and fully controllable colloidosomes, in particular, eliminating the transfer step. In this work, we demonstrate that nanoparticle colloidosomes with selective permeability can be prepared from monodisperse double emulsions as templates. Monodisperse