Papers by Gourab Bhattacharjee
arXiv: Materials Science, 2017
Intermetallic compounds Zr9Ni11 and Hf9Ni11 have been studied by time-differential perturbed angu... more Intermetallic compounds Zr9Ni11 and Hf9Ni11 have been studied by time-differential perturbed angular correlation (TDPAC) spectroscopy. Multiphase components have been found in both these compounds. In Zr9Ni11, the phase Zr9Ni11 is found to be predominant (89%) at room temperature. Besides this, a secondary phase due to Zr8Ni21 is found (11%). From temperature-dependent TDPAC studies, it is found that Zr9Ni11 is unstable at higher temperature (>773 K). At 773 K, Zr9Ni11 partially decomposes to Zr7Ni10 and at 973 K, it is completely decomposed to ZrNi and Zr7Ni10. This compositional phase change from Zr9Ni11 to ZrNi and Zr7Ni10 is not reversible and we do not retrieve Zr9Ni11 at remeasured room temperature. In stoichiometric Hf9Ni11, the phase HfNi is found to be predominant (81%) while the phase due to Hf9Ni11 is found as a minor phase (19%). However, no compositional phase change at higher temperature is found in Hf9Ni11. After heating the sample at 873 K, the same two phases of ...
RSC Advances, 2021
Aggregation of intrinsically disordered as well as the ordered proteins under certain premises or... more Aggregation of intrinsically disordered as well as the ordered proteins under certain premises or physiological conditions leads to pathological disorder.
Chemistry – A European Journal, 2021
The design and development of soft biomaterials based on amino acid and short-peptide have gained... more The design and development of soft biomaterials based on amino acid and short-peptide have gained much attention due to their potent biomedical applications. A slight alteration in the side-chain of single amino acid in a peptide or protein sequence has a huge impact on the structure and function. Phenylalanine is one of the most studied amino acids, which contains an aromatic phenyl group connected through a flexible -CH 2 - unit. In this work, we have examined whether flexibility and aromatic functionality of phenylalanine (Phe) are important in gel formation of model gelator Fmoc-Phe-OH or not. To examine this hypothesis, we synthesized Fmoc-derivatives of three analogues unnatural amino acids including cyclohexylalanine, phenylglycine, and homophenylalanine; which are slightly varied from Phe. Interestingly, all these three new analogues formed hydrogels in phosphate buffer at pH 7.0 having different gelation efficacy and kinetics. This study suggests that the presence of aromatic side-chain and flexibility are not mandatory for the gelation of the model gelator. Newly synthesized unnatural amino acid derivatives have also exhibited promising antimicrobial activity towards gram-positive bacteria by inhibiting cellular oxygen consumption. We further determined the biocompatibility of these amino acid derivatives by using a hemolysis assay on human blood cells. Overall studies described the development of single amino acid-based new injectable biomaterials with improved antimicrobial activity by the slight alteration in the side-chain of amino acid.
People have the ability to speak in riddles, and as non-native speakers, we call these riddles-id... more People have the ability to speak in riddles, and as non-native speakers, we call these riddles-idioms. Idioms make part of the vast family of fi gurative expressions in language (along with metaphors, similes, proverbs, etc.). They are very well known to the native speakers, but are rather confusing for those acquiring English as the second language. Learning idioms is not easy, but once understood, it can be a lot of fun to use them especially while speaking to englishmen. On the other hand, idioms should be used carefully and only when you are sure of their meaning. The aim of this paper is to give defi nition of idiom as well as some examples of idioms more or less frequently used in English language to avoid ambiguities. For the purpose of this paper, I narrowed it down on idioms containing color expressions, giving the meaning, origin (in case it was attainable) and examples.
Journal of Physics D: Applied Physics, 2018
The room temperature resistive switching behavior in 50 keV O+-ion irradiated TiO2−x layers at an... more The room temperature resistive switching behavior in 50 keV O+-ion irradiated TiO2−x layers at an ion fluence of 5 × 1016 ions cm−2 is reported. A clear transformation from columnar to layered polycrystalline films is revealed by transmission electron microscopy with increasing ion fluence, while the complementary electron energy loss spectroscopy suggests an evolution of oxygen vacancy (OV) in TiO2−x matrix. This is further verified by determining electron density with the help of x-ray reflectivity. Both local and device current–voltage measurements illustrate that the ion-beam induced OVs play a key role in bistable resistive switching mechanism.
ACS Applied Bio Materials, 2019
Herein, we are reporting for the first time, the supramolecular hydrogelation of a derivative of ... more Herein, we are reporting for the first time, the supramolecular hydrogelation of a derivative of 3-nitrotyrosine (3-NT), which is an oxidized by-product of tyrosine, produced in presence of reactive nitrogen species (RNS) in the cell. The 9-fluorenylmethyloxycarbonyl (Fmoc) derivative of 3-NT, FNT can form self-supported hydrogels at wide-range of pH (pH 4.5-8.5) at 50 mM phosphate buffer solutions. Hydrogel prepared in pH 7.0 is yellow in colour, transparent and thixotropic in nature. Yellow coloured hydrogel was obtained from colourless hydrogel by changing the pH from 4.5 to 8.5. Moreover, the gelation efficiency of FNT gelator is enhanced by lowering the pH of the buffer solution. pH-Dependent self-assembly properties of the gelator were studied by using UV-Vis, fluorescence, circular dichroism (CD) spectroscopy and wide-angle X-ray diffraction (WXRD) techniques. FE-SEM and TEM studies of the self-assembled FNT hydrogel showed nanofibrillar network structure. Interestingly, the hydrogel showed injectable behaviour in physiological pH. The low cytotoxicity value and high antimicrobial properties of hydrogel indicated that it is a potential material for biomedical applications.
Intermetallic compounds Zr7Ni10 and Hf7Ni10 have been studied by perturbed angular correlation (P... more Intermetallic compounds Zr7Ni10 and Hf7Ni10 have been studied by perturbed angular correlation (PAC) spectroscopy considering the fact that Zr7Ni10 has application as hydrogen storage material in fuel cell. In stoichiometric Zr7Ni10, the phase Zr2Ni7 is found to be dominant (~38%) while a fraction of ~25% is found for the Zr7Ni10 phase at room temperature. In this compound, a phase due to Zr8Ni21 (~10%) is found from room temperature up to 773 K but, this is not found at 873 K and above. In the stoichiometric Hf7Ni10 sample, the phase due to Hf7Ni10 is found as a minor phase (~22%) at room temperature. In this system, no phase of Hf2Ni7 is observed but, a different phase due to HfNi3 is found to be dominant (~62%). It is found that the site fraction of Hf7Ni10 enhances with temperature at the expense of HfNi3 and this phase becomes predominant (~57%) at 673 K and above. The change of phase fractions of HfNi3 and Hf7Ni10 with temperature is found to be reversible. The phase component...
Crystalline phases formed in stoichiometric Zr_9Ni_11 and Hf_9Ni_11 have been studied by perturbe... more Crystalline phases formed in stoichiometric Zr_9Ni_11 and Hf_9Ni_11 have been studied by perturbed angular correlation (PAC) spectroscopy, XRD and TEM/SAED measurements. In Zr_9Ni_11, the phases Zr_9Ni_11 (∼89%) and Zr_8Ni_21 (∼11%) have been found at room temperature from PAC measurements. At 773 K, Zr_9Ni_11 partially decomposes to Zr_7Ni_10 and at 973 K, it is completely decomposed to ZrNi and Zr_7Ni_10. In Hf_9Ni_11, a predominant phase (∼81%) due to HfNi is found at room temperature while the phase Hf_9Ni_11 is produced as a minor phase (∼19%). No compositional phase change at higher temperature is found in Hf_9Ni_11. Phase components found from XRD and TEM/SAED measurements are similar to those observed from PAC measurements. Electric field gradients in Zr_9Ni_11 and Hf_9Ni_11 have been calculated by density functional theory (DFT) using all electron full potential (linearized) augmented plane wave plus local orbitals [FP-(L)APW+lo] method in order to assign the phase components.
Materials, 2021
We report the surface stoichiometry of Tix-CuyNz thin film as a function of film depth. Films are... more We report the surface stoichiometry of Tix-CuyNz thin film as a function of film depth. Films are deposited by high power impulse (HiPIMS) and DC magnetron sputtering (DCMS). The composition of Ti, Cu, and N in the deposited film is investigated by X-ray photoelectron spectroscopy (XPS). At a larger depth, the relative composition of Cu and Ti in the film is increased compared to the surface. The amount of adventitious carbon which is present on the film surface strongly decreases with film depth. Deposited films also contain a significant amount of oxygen whose origin is not fully clear. Grazing incidence X-ray diffraction (GIXD) shows a Cu3N phase on the surface, while transmission electron microscopy (TEM) indicates a polycrystalline structure and the presence of a Ti3CuN phase.
Materials Advances
Here, we are reporting for the first time a simple naphthalimide derivative that undergoes assemb... more Here, we are reporting for the first time a simple naphthalimide derivative that undergoes assembly in the J-type manner in the solid, solution and gel state. It shows the aggregation-induced emission property and has been used for cell imaging.
ACS Applied Nano Materials
Spherical gold nanoseed (∼5–6 nm)-induced (but not seed-mediated) silver nanorods (Hy-Au@AgNRs) o... more Spherical gold nanoseed (∼5–6 nm)-induced (but not seed-mediated) silver nanorods (Hy-Au@AgNRs) of variable lengths have been synthesized by a new methodology that shows enhancement in catalytic ac...
Applied Surface Science
Abstract In this report, a comprehensive study on ion beam patterning of Si surface with simultan... more Abstract In this report, a comprehensive study on ion beam patterning of Si surface with simultaneous co-sputtering of stainless steel (SS) has been described. The experiment has been carried out using 500 eV energy Ar+ ion beam sputtering at normal ion incidence by varying the ion fluences. To explore the morphological details, different regions of the samples with respect to the distance from the SS target are probed using AFM and SEM techniques. For an ion fluence above 5 × 10 17 ions/cm2, pronounced nano-dots appear on the surface and with a further increase of fluence up-to 5 × 10 18 ions/cm2, coagulation and nucleation of the nano-dots occur leading to the formation of mound-like structures. Such a kind of patterning mechanism in the presence of metal impurity is governed by the recent theory put forward by Bradley. According to which the interplay between the irradiated surface and the surface impurity leads to the evolution of pronounced nanoscale patterns on the surface. The only required condition for such a mechanism is the formation of immobile chemical bonds on the surface, which in our case is reflected from the occurrence of FeSi2 bond revealed from XPS and TEM analysis.
Nanoscale
The actin cytoskeleton is required for the maintenance of the cell shape and viability of bacteria.
Materials Chemistry and Physics
Abstract Here we report a simple low-cost method to produce surface-enhanced Raman scattering (SE... more Abstract Here we report a simple low-cost method to produce surface-enhanced Raman scattering (SERS) substrates with improved efficiency and high sensitivity towards uric acid and ascorbic acid sensing using non-enzymatic amperometric electrochemical method. Trisoctahedral gold (Au) core-silver (Ag) shell cubical shaped nanoparticles were synthesized simply by varying the surfactant in the reaction medium, and afterwards we made them hollow by galvanic displacement reaction. Spherical core-shell nanoparticles (both solid and hollow) were also prepared to compare results with cubical one. We have performed transmission electron microscopy (TEM) studies to understand the morphology of these nanoparticles and UV–vis–NIR and Raman spectroscopy studies to understand optical properties. We have obtained a huge SERS enhancement (~109) for hollow Au@Ag nanocube using 4-mercapto benzoic acid (4-MBA) as analyte. Because of the very thin Ag shell wall, both core Au and shell Ag interacts with the incoming electromagnetic wave, and also due to the presence of multiple sharp edges and corners in both core and shell part of the nanoparticles there is a large enhancement of the electromagnetic field. We have performed cyclic voltammetry study using the nanoparticles as electrode to understand how interfacial charge transfer and electron accumulation is happening in between an electrode and electrolyte interface and we have obtained a very high current response for hollow core-shell nanocube due to more surface area. High current response with voltage enable us to use hollow core-shell nanocubes as non-enzymatic electrochemical sensor for sensing uric acid (UA) and ascorbic acid (AA). We found a good sensitivity (1.509 μAmM−1cm−2 and 209.027 μAmM−1cm−2 for UA and AA, respectively) and very low detection limit (0.36 μM and 0.019 μM for UA and AA, respectively) towards sensing, which allows us to use Au@Ag hollow nanocube as a good UA and AA sensors.
Coatings
Ternary carbide in metal matrix composites constitute a big challenge in the industry, and in thi... more Ternary carbide in metal matrix composites constitute a big challenge in the industry, and in this regard their surface treatment is one of the most important issues. Ternary carbide (CuxTiyCz, where x, y and z are integers) thin films are synthesized by magnetron sputtering and characterized with respect to the film depth. X-ray photoelectron spectroscopy (XPS) of Cu-2p and Ti-2p peaks shows the associated shake-up satellite peaks at a smaller film depth; the peak intensity is reduced at a higher depth. The relative intensity of Cu and Ti increases at a larger film depth. The optical band gap varies from 1.83 to 2.20 eV at different film depths.
The Journal of Physical Chemistry C
The role of the single-domain ferrimagnetic nanostructure and the associated surface for many fol... more The role of the single-domain ferrimagnetic nanostructure and the associated surface for many fold magnetic-field-induced surface enhanced transient spin-trajectory modulation is a new venture in m...
DAE SOLID STATE PHYSICS SYMPOSIUM 2018
Palladium nanocubes and gold nano-octahedral core and palladium shell nanocubes are synthesized b... more Palladium nanocubes and gold nano-octahedral core and palladium shell nanocubes are synthesized by seed mediated chemical synthesis. Both the Pd nanocubes and Au@Pd nanocubes are characterized by an analytical Transmission Electron Microscopy and the composition of core-shell nanocubes were analyzed by Energy Dispersive Xray spectroscopy (EDX). The near field electric field distribution around the nanocubes are simulated by FDTD simulation which shows higher electric field around the core shell nanocubes compared to monometallic counterpart due to the insertion of Au core which also results in higher SERS enhancement.
Nanomaterials
We have carried out extensive measurements on novel Fe 3 O 4-γ-Fe 2 O 3 core-shell nanoparticles ... more We have carried out extensive measurements on novel Fe 3 O 4-γ-Fe 2 O 3 core-shell nanoparticles of nearly similar core diameter (8 nm) and of various shell thicknesses of 1 nm (sample S1), 3 nm (sample S2), and 5 nm (sample S3). The structure and morphology of the samples were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The direct current (DC) magnetic measurements were carried out using a superconducting quantum interference device (SQUID). Exchange bias and coercivity were investigated at several temperatures where the applied field was varied between 3 and −3 T. Several key results are obtained, such as: (a) the complete absence of exchange bias effect in sample S3; (b) the occurrence of nonconventional exchange bias effect in samples S2 and S1; (c) the sign-change of exchange bias field in sample S2; (d) the monotonic increase of coercivity with temperature above 100 K in all samples; (e) the existence of a critical temperature (100 K) at which the coercivity is minimum; (f) the surprising suppression of coercivity upon field-cooling; and (g) the observation of coercivity at all temperatures, even at 300 K. The results are discussed and attributed to the existence of spin glass clusters at the core-shell interface.
New Journal of Chemistry
AuCl4-ions are reduced to Au0 inside the pores of CeO2 nanocubes by oleylamine, which has the dua... more AuCl4-ions are reduced to Au0 inside the pores of CeO2 nanocubes by oleylamine, which has the dual role of capping and reducing agent.
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Papers by Gourab Bhattacharjee