Browsing by Author "Biswajit Ray"

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Biocompatible thermoresponsive N-isopropyl-N-(3-(isopropylamino)-3-oxopropyl)acrylamide-based random copolymer: synthesis and studies of its composition dependent properties and anticancer drug delivery efficiency
(Royal Society of Chemistry, 2022) Sourov Mondal; Archana Kumari; Kheyanath Mitra; Abhineet Verma; Satyen Saha; Biswajit Maiti; Ranjeet Singh; Partha Pratim Manna; Pralay Maiti; Hironobu Watanabe; Masami Kamigaito; Biswajit Ray
A new acrylamide monomer, N-isopropyl-N-(3-(isopropylamino)-3-oxopropyl)acrylamide (M3i), consisting of both isopropyl and isopropylamidopropyl moieties, has been synthesized from isopropylamine and N-isopropylacrylamide via an aza-Michael addition reaction followed by amidation with acryloyl chloride. The homopolymer of M3i (polyM3i) and a series of random copolymers of M3i and poly(ethylene glycol)methyl ether acrylate (PEGA: CH2 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 CHCO2(CH2CH2O)nMe, Mn = 480, n = 9 on average) with varying compositions have been synthesized via reversible addition-fragmentation chain transfer polymerization using 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) as well as 1-phenylethyl phenyl dithioacetate (PEPD) as a RAFT agent. These polymers have been characterized by 1H NMR, FTIR, GPC, UV-Vis, fluorescence, TGDTA, DSC, DLS, and TEM techniques. A lower critical solution temperature (LCST) and glass transition temperature (Tg) for polyM3i prepared using DDMAT were observed at 17 and 133 °C, respectively, while for a polymer formed using PEPD, no LCST was observed until 0 °C and its observed Tg was found at 127.3 °C. The polymers are thermally stable up to 300 °C. Upon an increase in the M3i content in the copolymers, LCST decreases, Tg increases, and the apparent hydrodynamic diameter decreases. Moreover, the effects of concentration and the addition of urea and sodium chloride on the LCST of the copolymer with an LCST close to body temperature were studied. Owing to the incorporation of PEGA, a higher critical micellar concentration and larger TEM particle size of this copolymer were observed with respect to those of polyM3i. The usefulness of the micelles of the copolymers as nano-carriers for the drug doxorubicin was explored. The in vitro tumoricidal activity of the micelles of the doxorubicin-loaded copolymers was also assessed against Dalton's lymphoma cells. © 2022 The Royal Society of Chemistry.
Brominated Graphene as Mimetic Peroxidase for Sulfide Ion Recognition
(American Chemical Society, 2017) Shikha Singh; Kheyanath Mitra; Aparna Shukla; Rajshree Singh; Ravi Kumar Gundampati; Nira Misra; Pralay Maiti; Biswajit Ray
Brominated graphene (GBR) with ∼3% bromine content has shown novel peroxidase mimetic activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Optimum activity has been observed at pH 4.48 and after a minimum ∼30 min of equilibration time. Among the different analytes studied using the sensor combining TMB, H2O2, and GBR in phosphate buffer of pH 4.48, the S2- ion has effectively shown a short duration of sensing (∼2 min) within the detection range of 0.04-1 mM. A calibration curve for S2- ion estimation has been constructed with the experimental linearity in 0.04-0.4 mM range and having the limit of detection (LOD) value of 25.3 μM. A standard addition experiment has validated the method. A paper strip sensor has been fabricated for successful detection of S2- ion. © 2016 American Chemical Society.
Cell proliferation influenced by matrix compliance of gelatin grafted poly(D,L-Lactide) three dimensional scaffolds
(Elsevier B.V., 2018) Chelladurai Karthikeyan Balavigneswaran; Sanjeev Kumar Mahto; Arun Kumar Mahanta; Rajshree Singh; Mahalingam Rajamanickam Vijayakumar; Biswajit Ray; Nira Misra
Surface and mechanical properties of the biomaterials are determinants of cellular responses. In our previous study, star-shaped poly(D,L-Lactide)-b-gelatin (ss-pLG) was reported for possessing improved cellular adhesion and proliferation. Here, we extended our investigation to establish the cellular compatibility of gelatin-grafted PDLLA with respect to mechanical properties of biological tissues. In this view, linear PDLLA-b-gelatin (l-pLG) was synthesized and tissue-level compatibility of 1-pLG and ss-pLG against fibroblasts (L929), myoblasts (C2C12) and preosteoblasts (MG-63) was examined. The cell proliferation of C2C12 was significantly higher within l-pLG scaffolds, whereas L929 showed intensified growth within ss-pLG scaffolds. The difference in cell proliferation may be attributed to the varying mechanical properties of scaffolds; where the stiffness of l-pLG scaffolds was notably higher than ss-pLG scaffolds, most likely due to the variable levels of gelatin grafting on the backbone of PDLLA. Therefore, gelatin grafting can be used to modulate mechanical property of the scaffolds and this study reveals the significance of the matrix stiffness to produce the successful 3D scaffolds for tissue engineering applications. © 2018 Elsevier B.V.
Colorimetric detection of hydrogen peroxide and cholesterol using Fe3O4-brominated graphene nanocomposite
(Springer Science and Business Media Deutschland GmbH, 2022) Jaydeep Singh; Rajshree Singh; Shikha Singh; Kheyanath Mitra; Sourov Mondal; Sambhav Vishwakarma; Biswajit Ray
Fe3O4-brominated graphene (Fe3O4-GBR) nanocomposites were synthesized via an in situ method using the precursors FeSO4.7H2O and GBR in different (1:1, 1:2, 2:1, 1:5, 1:10, 1:20, and 5:1) weight ratios at pH 11.5. The Fe3O4-GBR (1:5) nanocomposite in combination with H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB) showed swift and superior intrinsic peroxidase mimetic enzyme activity compared with the other Fe3O4-GBR composites, GBR and Fe3O4, as observed by colorimetry. It was characterized using high-resolution scanning electron microscopy (HRSEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Its catalytic activity was optimized by varying different parameters, and the optimum conditions for peroxidase mimetic activity were observed using 100 μL Fe3O4-GBR (1 mg/mL), 50 μL TMB (1 mg/mL), and 200 μL H2O2(1 mM) in 400 μL of acetate buffer of pH 2.3 at 30 °C temperature. Kinetic analysis has revealed the Michaelis–Menten kinetic behavior of peroxidase activity with Michaelis–Menten constants (Km) and maximum initial velocities (Vmax) of 0.082 mM and 14.1 nMs−1 respectively, for H2O2 and 0.086 mM and 5.1 nMs−1, respectively for TMB. The limit of detection and linear range were found to be 49.6 μM and 100–880 μM, respectively, for H2O2 and 41.9 μM and 47.6–952.3 μM, respectively, for cholesterol. On this basis, a simple, swift, sensitive, selective, and reproducible colorimetric assay to detect cholesterol levels in blood serum samples using Fe3O4-GBR nanocomposite has been developed. Thus, Fe3O4-GBR composite as compared to Fe3O4 and GBR has shown better peroxidase mimicking activity for biosensing. Graphical abstract: [Figure not available: see fulltext.] © 2022, Springer-Verlag GmbH Germany, part of Springer Nature.
Colorimetric detection of hydrogen peroxide and glucose using brominated graphene
(Royal Society of Chemistry, 2017) Shikha Singh; Kheyanath Mitra; Rajshree Singh; Archana Kumari; Susanta Kumar Sen Gupta; Nira Misra; Pralay Maiti; Biswajit Ray
Very recently, we have reported a novel peroxidase mimetic material, brominated graphene (GBR) having ∼3% bromine content, which, in combination with H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB), has shown the property of S2- ion recognition (Anal. Chem., 2017, 89, 783-791). In the present work, we further have investigated the kinetic assay and colorimetric sensing ability of GBR towards hydrogen peroxide (H2O2) and glucose. The Michaelis-Menten constants (Km) and maximum initial velocities (Vmax) of GBR have been found to be 10.98 mM and 3.60 × 10-8 M s-1, respectively, for H2O2 and 0.83 mM and 0.68 × 10-8 M s-1, respectively, for TMB. A sensor combining TMB and GBR has been fabricated, which, upon addition to H2O2 or glucose with glucose oxidase solution at pH 4.48, showed colorimetrically a significant increase in the oxidation of TMB. The fabricated sensor system has displayed linearity for H2O2 and glucose estimation in the range 0.50-5.00 mM and 40-100 mM, respectively, and the corresponding limits of detection are found to be 0.417 and 28.41 mM, respectively. The present sensor system is also highly reproducible and selective. The results of real samples using this colorimetric method have been found to be comparable with the conventional auto-analyser method. © The Royal Society of Chemistry 2017.
Conducting nano-channels in an induced piezoelectric polymeric matrix using swift heavy ions and subsequent functionalization
(2012) Karun Kumar Jana; Biswajit Ray; Devesh K. Avasthi; Pralay Maiti
Nanohybrids of poly(vinylidene fluoride) with layered silicates have been synthesized by melt extrusion and nano-channels have been fabricated by swift heavy ion (SHI) irradiation followed by chemical etching of the selective amorphous zones in the latent tracks. The channel diameter was reduced to 30 nm in the presence of nanoclay in the nanohybrid, making it suitable for membrane applications. Grafting with styrene was carried out inside the nano-channels using the free radicals created by the SHI exposure. Sulphonation on the grafted polystyrene was carried out to increase the conductivity of the membrane to the semiconducting range through ion channel conduction. The grafting and sulphonation inside the nano-channels were confirmed through spectroscopic techniques viz. NMR, FTIR, UV and molecular weight measurements. The dimensions of the channels are controlled by the SHI fluence and thereby dictates the properties including 10 orders of magnitude higher conductivity by creating a greater number of channels and hence increasing the surface area required for enhanced grafting and sulphonation. The hetero-junction and nano-channel conduction was demonstrated through STM measurements showing that the superior conduction depends on the relative extent of grafting and sulphonation in pure PVDF and the nanohybrid. The matrix PVDF crystallizes in the piezoelectric β-phase in the presence of nanoclay and promotes the formation of smart membranes. © 2012 The Royal Society of Chemistry.
Controlled drug release through regulated biodegradation of poly(lactic acid) using inorganic salts
(Elsevier B.V., 2017) Sunil Kumar; Shikha Singh; Sudipta Senapati; Akhand Pratap Singh; Biswajit Ray; Pralay Maiti
Biodegradation rate of poly(lactic acid) (PLA) has been regulated, both increase and decrease with respect to the biodegradation of pure PLA, by embedding meager amount of inorganic salts in polymer matrix. Biodegradation is performed in enzyme medium on suspension and film and the extent of biodegradation is measured through spectroscopic technique which is also verified by weight loss measurement. Media pH has been controlled using trace amount of inorganic salt which eventually control the biodegradation of PLA. High performance liquid chromatography confirms the hydrolytic degradation of PLA to its monomer/oligomer. Induced pH by metal salts show maximum degradation at alkaline range (with calcium salt) while inhibition is observed in acidic medium (with iron salt). The pH of media changes the conformation of enzyme which in turn regulate the rate of biodegradation. Thermal degradation and increment of modulus indicate improvement in thermo-mechanical properties of PLA in presence of inorganic salts. Functional stability of enzyme with metal salts corresponding to acidic and alkaline pH has been established through a model to explain the conformational changes of the active sites of enzyme at varying pH influencing the rate of hydrolysis leading to regulated biodegradation of PLA. The tuned biodegradation has been applied for the controlled release of drug from the polymer matrix (both sustained and enhanced cumulative release as compared to pure polymer). The cell proliferation and adhesion are influenced by the acidic and basic nature of polymeric material tuned by two different inorganic salts showing better adhesion and proliferation in calcium based composite and, therefore, suggest biological use of these composites in biomedical applications. © 2017 Elsevier B.V.
Correction: Enhanced activity and chlorine protection in prolonged seawater electrolysis using MoS2/sulfonated reduced graphene oxide (Sustainable Energy and Fuels (2025) 9 (4300-4319) DOI: 10.1039/D5SE00541H)
(Royal Society of Chemistry, 2025) Prerna Tripathi; Renna Shakir; Amit Kumar Verma; Jeyakumar Karthikeyan; Biswajit Ray; Akhoury Sudhir Kumar Sinha; Shikha K. Singh
The authors regret that the details of the affiliations were not correct in the original manuscript. The corrected affiliations for this paper are as shown herein. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © 2025 The Royal Society of Chemistry.
Dextrin and polyurethane graft copolymers as drug carrier: Synthesis, characterization, drug release, biocompatibility and in-vitro toxicity
(Elsevier Ltd, 2021) Aparna Shukla; Swapan Maity; Biswajit Ray; Pralay Maiti
Chemical modification of dextrin with polyurethane as a graft has been synthesized for controlled drug release for longer time period by maintaining the hydrophobic–hydrophilic balance. Estimation of the degree of grafting is visualized from the integrated peak area in the NMR spectra. Particle nature of dextrin is converted into strip like morphology in polyurethane graft dextrin copolymers as obvious from atomic force microscopy. Drug release study of graft copolymers through in vitro studies indicates sustained drug release behavior as compared to pristine dextrin and specific interactions between polymer and drug have been verified through spectroscopic techniques. Biocompatibility of the graft copolymers has been revealed using cellular studies on cancerous HeLa cells through MTT assay and cell adhesion. Further, the cytotoxicity or the cell killing efficiency has been demonstrated resulting in significant cell mortality using the developed graft copolymers. © 2021
Doxorubicin loaded pH responsive biodegradable ABA-type Amphiphilic PEG-b-aliphatic Polyketal-b-PEG block copolymer for therapy against aggressive murine lymphoma
(Elsevier Inc., 2020) Sumit Kumar Hira; Kheyanath Mitra; Prateek Srivastava; Shikha Singh; Sambhav Vishwakarma; Ranjeet Singh; Biswajit Ray; Partha Pratim Manna
A novel ABA-type polyethylene glycol (PEG)-b-polyketal (PK)-b-PEG block copolymer was synthesized via click reactions between the monoazido-monomethoxy-PEG and dialkyne terminated aliphatic polyketal with no carboxylic/amide linkages. Formation of the novel block copolymer was confirmed by 1H NMR, GPC, TGA, and DSC studies. The formed copolymer has shown faster degradation at acidic pH. Self-assembly of this block copolymer (average size 6.2 nm) was assessed by fluorescence study using pyrene as a probe. Doxorubicin loaded block copolymeric micelles (69.9 nm) have shown pH dependent elevated drug release at pH 6.4, indicating its potential as a pH responsive nano-carrier for anticancer therapy. The nano-sized copolymer demonstrated tumoricidal activities against the lymphoma of murine and human origin with significant levels of growth inhibition and apoptosis. Therapy with doxorubicin loaded copolymer reduced the tumor size and augmented the life span of the tumor bearing animals with improved histopathological parameters, compared with the untreated control. © 2019 Elsevier Inc.
Effect of Isotacticity of Linear Poly(N-isopropylacrylamide) on its Gelation in Benzyl Alcohol
(Springer India, 2016) Chandra Sekhar Biswas; Kheyanath Mitra; Shikha Singh; Dinesh K Patel; Biswajit Maiti; Pralay Maiti; Biswajit Ray
Thermoreversible gelation of three different isotactic linear poly(N-isopropylacrylamide) (PNIPAM)s having meso dyad (m) values 62, 68 and 81% has been observed in benzyl alcohol. All the gels were transparent in nature. SEM image of the dried gels showed fibrillar network morphology. Melting temperature of the gels gradually increased with the increase in the concentration. XRD data of dry polymers and their corresponding dry gels showed shifting in the peak positions. Rheological study showed that stronger gels were formed with increasing isotacticity of PNIPAM while lower isotactic sample exhibited typical polymer melt rheology. The formation of a plunge in the storage modulus as well as in the viscosity plot at the same frequency range indicates the reversible nature of the structure breaking/reformation under frequency sweep. Moreover, the mechanical strength of the gel decreased with increase in temperature. UV-Vis kinetic study also indicated the change in the conformation and aggregation of PNIPAM chains during gelation. Molecular modelling calculation showed that the number of solvent molecules involved in forming gel (polymer-solvent compound) decreased with the increase in the isotacticity of the polymer. Gelation rate of these gels was studied as a function of temperature, concentration and isotacticity using test-tube tilting method. It increased with the increase in the concentration and isoacticity of the polymer, and with the decrease in the temperature. Critical gelation concentration of the gel gradually increased with the decrease in the isotacticity and with the increase in the temperature. All these experimental results indicated that gelation occurs presumably through polymer-solvent compound formation. [Figure not available: see fulltext.] © 2016, Indian Academy of Sciences.
Effect of L-menthol chain-end on the optical rotation, chirality, tacticity and thermal properties of polystyrene prepared by ATRP and polyvinylacetates prepared by RAFT polymerization: A molecular weight dependence study
(Elsevier Ltd, 2021) Sambhav Vishwakarma; Archana Kumari; Kheyanath Mitra; Shikha Singh; Zhiyi Song; Masayoshi Bando; Tamaki Nakano; Susanta Kumar Sen Gupta; Biswajit Ray
Two series of L-menthol-tagged homopolymers: one polystyrenes (PSt) and the other polyvinylacetates (PVAc) having different molecular weights have been synthesized via ATRP of styrene, and RAFT polymerization of vinyl acetate, respectively. Optical rotation study has established the magnitude of the optical rotation value for the both polymer series has been found decreasing exponentially with the increase of their molecular weights. CD study has revealed an exponential decrease in the molar ellipiticity values at 235 nm with the increase in the DPs of polymers in both the polymer systems. Formed PSts and PVAcs are atactic and slightly syndiotactic, respectively. With increase in the chain length of the polymers, glass-transition temperature (Tg) values have been found increasing exponentially in both systems. Therefore, living radical polymerization using suitable ATRP initiator or, RAFT agent containing suitable chiral moiety can be useful in inducing chirality in polymers up to high chain length. © 2020 Elsevier Ltd
Effect of n-Alkyl Side Chain Length on the Thermal and Rheological Properties of PolyN-(3-(alkylamino)-N-(3-(isopropylamino)-3-oxopropyl)acrylamide) Homopolymers
(John Wiley and Sons Inc, 2021) Archana Kumari; Sambhav Vishwakarma; Kheyanath Mitra; Chuangbi Chen; Shuming Cui; Biswajit Maiti; Sourov Mondal; Chandra Sekhar Biswas; Pralay Maiti; Florian J. Stadler; Biswajit Ray
Four new N-isopropylacrylamide- and N-n-alkyl amine-based acrylamide monomers, N-(3-(alkylamino)-N-(3-(isopropylamino)-3-oxopropyl) acrylamide (Mn) (n = 4, 8, 10, 12) are successfully synthesized and polymerized via reversible addition-fragmentation chain-transfer polymerization (polyMn, n = 4, 8, 10, and 12), which are characterized by gel permeation chromatography, 1H NMR, Fourier transform infra red spectroscopy, thermo-gravimetry-differential thermal analysis, differential scanning calorimetry (DSC), and rheology. All polymers are thermally stable and undergo a two-step degradation process at ≈280 and ≈375 °C. Glass transition temperature (Tg)s of these polymers decrease gradually from 99.6 to 52.5 °C with increasing n-alkyl side chain length. The rheology of these polymers in melt state agrees to a typical Rouse-melt behavior and allows for confirming the Tg determined from DSC. Benzyl alcohol solution rheology proves a weak structural build-up, in particular for polyM12. Comparison of the quantum chemical calculations of polyMns with n = 4–8 reveals increase in backbone helicity with increasing n-alkyl side chain length. © 2021 Wiley-VCH GmbH.
Effect of tacticity and molecular weight on the rheological properties of poly(N -isopropylacrylamide) gels in benzyl alcohol
(Society of Rheology, 2017) Chandra Sekhar Biswas; Yuhang Wu; Qiao Wang; Lei Du; Kheyanath Mitra; Biswajit Ray; Zhi-Chao Yan; Bing Du; Florian J. Stadler
Two series of different isotactic poly(N-isopropylacrylamide) of number average molar masses (Mn) ∼ 100 000, 200 000 and narrow molar mass distribution are prepared by reversible addition fragmentation chain transfer polymerization. Their thermoreversible, physical gels are prepared in benzyl alcohol and rheologically characterized to assess the effect of tacticity and molar masses on the rheological properties. In general, higher tacticity, higher molar mass, and higher concentration lead to stiffer gels and a sol-gel transition at a higher temperature. The results are interpreted based on partial phase separation leading to stiff but labile spongelike structures. The tacticity influences the strength of the phase separation tendency. Concentration and molar mass determine how far reaching and how connected these domains are. © 2017 The Society of Rheology.
Effects of tacticity and molecular weight of poly(N -isopropylacrylamide) on its glass transition temperature
(2011) Chandra Sekhar Biswas; Vijay Kumar Patel; Niraj Kumar Vishwakarma; Vimal K. Tiwari; Biswajit Maiti; Pralay Maiti; Masami Kamigaito; Yoshio Okamoto; Biswajit Ray
A series of high molecular weight poly(N-isopropylacrylamide) (PNIPAM)s with low polydispersity (Mn = 7.0 × - 104 to 10.2× - 104 g mol-1, PDI = 1.23-1.35) having different isotacticity [meso diad (m) = 47-88%]] was successfully synthesized using the reversible addition-fragmentation chain transfer (RAFT) polymerization method in the presence of different concentrations of Y(OTf)3 Lewis acid. Measurement of the glass transition temperature (Tg) of this high molecular weight isotactic PNIPAM series and the low molecular weight PNIPAM series (Mn = 3.5 × - 104 to 4.0 × - 104 g mol-1, PDI = 1.2-1.3) having different isotacticity [meso diad (m) = 45-72%)] reported earlier by us (Ray et al. Polym. J. 2005, 37, 234) showed that Tg of PNIPAM decreases with increase in its meso diad content (m %) and decrease in its molecular weight. © 2011 American Chemical Society.
Efficacy of polyurethane graft on cyclodextrin to control drug release for tumor treatment
(Academic Press Inc., 2019) Aparna Shukla; Akhand Pratap Singh; Biswajit Ray; Vinod Aswal; Amrita G. Kar; Pralay Maiti
Hydrophilicity of cyclodextrin is controlled through grafting of polyurethane of varying graft density, thereby maintain the hydrophilic-hydrophobic balance, to sustain the drug delivery rate for better tumor treatment. Grafting is verified through nuclear magnetic resonance (1H NMR) and other spectroscopic techniques along with the hydrodynamic volume measurement of grafted species and the degree of substitution has been calculated from the integrated peak areas. Thermal and mechanical stability of the graft copolymers have improved significantly with respect to cyclodextrin and the formation of smaller blobs having larger in number has been obtained from small angle neutron scattering, atomic force microscopy and optical images. Sustained drug delivery has been achieved using graft copolymer as opposed to burst release in pure cyclodextrin and polyurethane and the phenomenon is understood from the specific interactions, as observed though spectroscopic and thermal measurement, between graft copolymer and drug followed by this novel architecture of the graft copolymers. Biocompatibility of graft copolymers has been checked using cellular studies through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell adhesion. Importantly, the cell killing efficiency has been demonstrated by embedding anti-cancer drug in polymer matrices causing mortality rate of 80% using graft copolymer against meagre 20% using pure drug or drug embedded in cyclodextrin and the result is realised from the sustained release of drug from the graft copolymer vis-à-vis burst release in other systems. Cellular studies have been translated into an animal model showing the efficacy of newly developed patch, made of drug embedded in copolymer, towards the significant suppression of tumors in mice as compared to control. Histopathological images and biochemical parameters indicate the normal body organ/blood in copolymer treated mice against severely damaged organ especially liver/blood in the mice treated with pure drug or drug embedded in cyclodextrin arising from burst release. Thus, graft copolymer with unique architecture is found to be an effective drug delivery vehicle for melanoma cancer treatment without side effect. © 2018 Elsevier Inc.
Electrochemical sensing of hydrogen peroxide using brominated graphene as mimetic catalase
(Elsevier Ltd, 2017) Shikha Singh; Monali Singh; Kheyanath Mitra; Rajshree Singh; Susanta Kumar Sen Gupta; Ida Tiwari; Biswajit Ray
Recently we have reported the peroxidase mimicking ability of metal free brominated graphene (GBR) (Analytical Chemistry, 89, 783–791, 2017) at a pH less than 7.2. Here we report the novel catalase mimicking ability of GBR via electrochemical (electro-oxidation) detection of hydrogen peroxide (H2O2) at pH ≥ 7.2. We have fabricated successfully a low cost electrochemical sensor using GBR coated glassy carbon electrode (GCE) [(GBR-GCE)-working electrode] and showed its excellent cyclic voltametry (CV) response towards electro-oxidation of hydrogen peroxide (H2O2), which is so far shown by electrodes made of platinum-group metals like Pt, Ir, Ru etc. Thus, GBR has exhibited the dual mimicking ability as peroxidase and also as catalase under different conditions. A plausible mechanism of sensing of hydrogen peroxide has been proposed involving the formation of perhydroxyl radical (HO2˙) facilitated by GBR-GCE as the electrode. Calibration curves for H2O2 detection using both CV and differential pulse voltametry (DPV) techniques have been constructed over 0.1–10 mM linearity range with the limits of detection of 0.048 and 0.063 mM, respectively. This fabricated electrochemical sensor is highly selective, specific and its response current is least affected by the presence of interfering analytes. The results are found highly reproducible and the use of GBR has also minimized the problem and specificity associated with natural enzymes, as it can easily be stored at room temperature. Real samples have also been successfully analyzed using our fabricated sensor. © 2017 Elsevier Ltd
Electron beam-induced piezoelectric phase in poly(vinylidene fluoride) nanohybrid: EFFECT at the molecular level
(John Wiley and Sons Ltd, 2015) Vimal K Tiwari; Madhab C Rath; Sisir K Sarkar; Vijay K Patel; Biswajit Ray; Biswajit Maiti; Pralay Maiti
A nanohybrid has been synthesized by incorporating organically modified layered silicate in a poly(vinylidene fluoride) (PVDF) matrix. Molecular-level phenomena have been explored after exposing PVDF and its nanohybrid to an electron beam of varying doses. The electron beam interacts with polymer chains and thereby generates different free radicals, the number of which is quite high in nanohybrid as compared to pure PVDF. The stability of free radicals has been confirmed through density functional theory energy minimization, predicting stable β-phase free radicals in the nanohybrid. Quantitative analyses of chain scission, crosslinking and double bond formation are reported and compared after irradiation for both PVDF and its nanohybrid using UV-visible and Fourier transform infrared spectroscopies, sol-gel analyses and gel permeation chromatography, revealing both chain scission and crosslinking phenomena in irradiated PVDF and its nanohybrid, but at higher dose (>90Mrad) crosslinking dominates in the nanohybrid due to more free radicals and proximity of radical chains on top of templated system in the nanohybrid as compared to pure PVDF. The enhanced crosslinking alters the nanostructure causing disappearance of the peak at 2θ ≈ 3°. Moreover, the electron beam induces significant piezoelectric β-phase in the nanohybrid against only α-phase in pure PVDF at a similar dose and raises the possibility for the use of electron-irradiated nanohybrid as an electromechanical device. β-Phase formation is also supported through solid-state NMR, scanning electron microscopy and differential scanning calorimetry studies. The thermal properties in terms of heat of fusion and degradation temperature have been verified indicating steady decrease of melting point and heat of fusion for pure PVDF while considerably less effect is observed for the nanohybrid. The combined effect of chain scission and crosslinking makes both PVDF and its nanohybrid brittle, but with greater stiffness with respect to unirradiated specimens. © 2014 Society of Chemical Industry.
Enhanced activity and chlorine protection in prolonged seawater electrolysis using MoS2/sulfonated reduced graphene oxide
(Royal Society of Chemistry, 2025) Prerna Tripathi; Renna Shakir; Amit Kumar Verma; Jeyakumar Karthikeyan; Biswajit Ray; Akhoury Sudhir Kumar Sinha; Shikha K. Singh
Electrolyzer technology necessitates the use of seawater instead of freshwater to achieve a comprehensive supply of clean and economical energy. However, the tendency of chloride ions (Cl−) to significantly erode the metal surface is a major challenge during seawater electrolysis. Therefore, designing an electrode that is resistant to chloride ions is of great importance to develop an efficient seawater electrolyser. In this work, we present a double layer anode consisting of a molybdenum sulfide electrocatalyst uniformly deposited over sulfonated graphene sheets coated over an Ni foam. The developed electrode (GNiMoOS) helps selectively convert H2O into H2 and O2 rather than chloride (Cl−) ions into ClO− in a seawater environment by resisting corrosion due to the Cl− ions in seawater. The chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) provides solid evidence that the GNiMoOS electrocatalyst blocks the chloride oxidation reaction owing to its distinct resistance to Cl−. In addition, density functional theory (DFT) calculations clearly validated the preference of sulfonic moieties towards OH− compared with Cl− ions, confirming the chlorine repelling properties of the GNiMoOS electrode. The successful in situ functionalisation of sulfonic moieties into the reduced graphene oxide (RGO) skeleton with simultaneous development of flower-like MoS2 was well confirmed using XPS, Raman, SEM, TEM, and FT-IR techniques. GNiMoOS delivered an impressive current density of 100 mA cm−2 for OER and HER at room temperature, requiring remarkably low overpotentials of just 180 mV and 201 mV, respectively. Industrial faradaic current densities (400-600 mA cm−2) were reported with the active electrode at combined overpotentials of ≤600 mV at room temperature. The unique morphology of MoS2 provides more active sites for the HER/OER, while sulfonated functional groups over graphene impart much-needed anticorrosion properties to the system. Moreover, the electrical coupling between MoS2 and RGO can make the electron transfer to RGO easier. Therefore, the synergistic interactions among MoS2, SO3H and RGO lead to improved catalytic activity and prolonged stability. © 2025 The Royal Society of Chemistry.
Enhanced catalytic and antibacterial activities of silver nanoparticles immobilized on poly(N-vinyl pyrrolidone)-grafted graphene oxide
(Royal Society of Chemistry, 2015) Shikha Singh; Ravi Kumar Gundampati; Kheyanath Mitra; K. Ramesh; Medicherla V. Jagannadham; Nira Misra; Biswajit Ray
Poly(N-vinyl pyrrolidone) (PNVP)-grafted graphene oxide (GO) (GO-PNVP) has been synthesized using a GO-based macro-RAFT agent prepared via click reaction of alkyne-terminated RAFT agent (S)-2-(propynyl propionate)-(o-ethyl xanthate) and azide-functionalized GO (GO-N3). FTIR, XPS, Raman, TGA and DSC studies confirmed its formation. Silver nanoparticles are then immobilized on GO-PNVP and GO via in situ reduction of silver nitrate in the presence and absence of glucose at 40 and 95 °C, respectively. FT-IR, UV-Vis, XRD, SEM and TGA studies supported the incorporation of silver (Ag) nanoparticles. Ag nanoparticles immobilized on GO-PNVP are small, spherical and narrowly distributed (homogenous, monodisperse) compared to GO. These nanocomposites are explored as catalysts for the reduction of p-nitrophenol into p-aminophenol and also as antibacterial agents towards Gram(+) S. aureus and Gram(-) E. coli bacteria. Ag nanoparticle immobilized GO-PNVP showed efficient catalytic activity and excellent reusability along with an excellent antibacterial activity. Hence, grafting of PNVP enhances the catalytic and antibacterial properties of GO. © 2015 The Royal Society of Chemistry.