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Chakravarty S.,Institute of Advanced Study in Science and Technology IASST | Datta A.,Assam University | Sen Sarma N.,Institute of Advanced Study in Science and Technology IASST
Journal of Materials Chemistry C | Year: 2017

Polyvinyl alcohol formaldehyde (PVF)-based composites are synthesized and applied for rapid detection and quantification of sulphur dioxide (SO2) vapours by electrical impedance measurements. A series of polymeric composites, namely PVF/single-walled carbon nanotubes (PVFCNTs), PVF/carbon nanoparticles (PVFCNPs), PVF-coumarin-6 (PVFCOU), PVF/thiophene (PVFTH) and PVF/cytochrome-6-oxidase (PVFCY), are synthesized in high yields by a simple one-pot approach. These were characterized by FT-IR, AC conductivity and FESEM. The composites were then used for the impedimetric detection of SO2 vapours, and the sensitivity was found to follow the order: PVFCOU > PVFTH > PVF. The current vs. voltage (I-V) curves further demonstrated a second-order decrease in conduction for PVFCOU upon exposure to SO2 vapours. Amongst the synthesized composites, PVFCOU exhibited an excellent response time of 3 s for 400 ppt SO2, with a limit of detection of 1.15 ppb. Our findings demonstrate, for the first time, an AC electrical impedance-based SO2 detection, using the PVFCOU polymeric composite. In addition, this polymeric composite fulfills the dual function of highly efficient sensing and analyte sequestration. Thus, PVFCOU may be an ideal cost-effective solid-state sensor material for onsite vapour sensing applications. © The Royal Society of Chemistry.


Bordoloi S.,Institute of Advanced Study in Science and Technology IASST | Basumatary B.,Institute of Advanced Study in Science and Technology IASST | Saikia R.,Institute of Advanced Study in Science and Technology IASST | Das H.C.,Oil India Ltd
Journal of Chemical Technology and Biotechnology | Year: 2012

Background: The aim of this study was to assess the suitability of Axonopus compressus for the removal of petroleum hydrocarbons from contaminated soil. An experiment was conducted with crude oil contaminated soil to evaluate the degradation of this crude oil in pots in the presence of A. compressus for 360 days. Study of the degradation of total petroleum hydrocarbon (TPH), its accumulation in roots and shoots, plant growth and biomass production and most probable number (MPN) was conducted at 60 day intervals. Result: In the presence of contaminants, plant biomass and height were significantly reduced. TPH was reduced by 70% in TA (fertilized soil) and 40% in TC (unfertilized soil). In the unvegetated pots, the reduction of TPH was 11% in TB (fertilized soil) and 9% in TD (unfertilized soil), which was attributed to microbial action and natural attenuation. Degradation was significantly greater in vegetated pots than in unvegetated pots (P < 0.05). Conclusion: A. compressus enhanced biodegradation of crude oil in soil under the conditions of this experiment. The addition of fertilizer further enhanced the degradation process. © 2012 Society of Chemical Industry.


Basumatary B.,Institute of Advanced Study in Science and Technology IASST | Saikia R.,Institute of Advanced Study in Science and Technology IASST | Bordoloi S.,Institute of Advanced Study in Science and Technology IASST | Das H.C.,Oil India Ltd | Sarma H.P.,Gauhati University
Journal of Chemical Technology and Biotechnology | Year: 2012

Background: Contamination of soil and sediments with petroleum hydrocarbons (PHCs) is a serious global problem and environmental concern. Therefore, remediation of soil, water, and sediments is a great challenge for research in this field. This study aims to use two types of sedge species, Cyperus odoratus L. and Cyperus laevigatus L. for phytoremediation of crude oil contaminated soil. The study includes the evaluation of plant height, root length, total petroleum hydrocarbon (TPH) degradation in soil, TPH accumulation in plants grown in fertilized and unfertilized pots and most probable number (MPN). Results: The presence of high concentrations of TPH negatively affected the health and survival of plants. A better result for degradation of TPH was found in fertilized soil (C. odoratus: 78%, C laevigatus: 73%) than in unfertilized soil (C. odoratus: 45%, C. laevigatus: 43%) during the 360 day study. In unplanted pots, the reduction of TPH was 11% in fertilized soil and 9% in unfertilized soil. TPH accumulation by plants and MPN were statistically significant. Conclusion: TPH degradation in soil considered together with the accumulation levels in roots and shoots as well as biomass production suggest that these plants could be used for phytoremediation. Furthermore, inorganic fertilizer amendments in soil showed positive effect on petroleum hydrocarbon degradation and its accumulation in plants. © 2012 Society of Chemical Industry.


Devi G.,Institute of Advanced Study in Science and Technology IASST | Devi A.,Institute of Advanced Study in Science and Technology IASST | Bhattacharyya K.G.,Gauhati University
Environmental Science and Pollution Research | Year: 2016

Analyses of fine particulates (PM2.5) from the upper Assam oil fields of India indicated considerable presence of higher hydrocarbons (C22–C35) and heavy metals, Cd, Co, Cr, Cu, Ni, Pb, and Zn. This has raised serious concern for the sustainability of the exotic Muga (Antheraea assama) silk production, which has been a prime activity of a large number of people living in the area. The Muga worm feeds on the leaves of Machilus bombycina plant, and the impacts of air quality on its survival were further investigated by analyzing the leaves of the plant, the plantation soil, and the Muga cocoons. PM2.5 content in the air was much more during the winter due to near calm conditions and high humidity. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and gas chromatography-mass spectrometer (GC-MS) analysis of PM2.5 showed the presence of higher alkanes (C22–C35) that could be traced to crude oil. Cr, Ni, and Zn were found in higher concentrations in PM2.5, M. bombycina leaves, and the plantation soil indicating a common origin. The winter has been the best period for production of the silk cocoons, and the unhealthy air during this period is likely to affect the production, which is already reflected in the declining yield of Muga cocoons from the area. SEM and protein analyses of the Muga silk fiber produced in the oil field area have exhibited the deteriorating quality of the silk. This is the first report from India on hydrocarbons and associated metals in PM2.5 collected from an oil field and on their possible effects on production of silk by A. assama. © 2015, Springer-Verlag Berlin Heidelberg.


Gogoi N.,Institute of Advanced Study in Science and Technology IASST | Chowdhury D.,Institute of Advanced Study in Science and Technology IASST
Journal of Materials Chemistry B | Year: 2014

Novel carbon dot coated alginate beads (CA-CD) exhibiting superior stability and swelling properties have been successfully prepared. CA-CD show exceptional stability in ambient condition and are stable at room atmosphere and temperature even after 60 days. Moreover, CA-CD show excessive swelling in comparison to calcium alginate (CA) beads. The beads were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and optical microscopy. The CA and CA-CD beads were investigated for their use as pH dependent sustained drug delivery vehicles taking tetracycline (TC) and tetracycline associated with β-cyclodextrin (β-TC) as model drug systems. It was observed that TC loading was 35% and 77% with CA and CA-CD, respectively. Tetracycline associated with β-cyclodextrin (β-TC) shows 48% loading for CA and much greater loading (as high as 90%) for CA-CD. At pH 1, CA-CD and CA beads show maximum drug release with TC cumulative release of 70% and 37% at 96 h, respectively. However, the delivery rates at pH 1 were slower in case of tetracycline associated with β-cyclodextrin (β-TC) loading showing 61% release for CA-CD and 22% for CA after 96 h. Thus, CA-CD can be suitably used as an effective drug delivery vehicle with maximum release obtained at pH 1 emphasizing its use in the gastrointestinal tract where pH is low. Also, the use of β-cyclodextrin with the drug as an inclusion complex renders the CA and CA-CD beads useful for slow and long-term drug administration. This journal is © the Partner Organisations 2014.


Saikia R.R.,Institute of Advanced Study in Science and Technology IASST | Deka S.,Institute of Advanced Study in Science and Technology IASST
Environmental Science and Pollution Research | Year: 2013

Accumulation of oily sludge is becoming a serious environmental threat, and there has not been much work reported for the removal of hydrocarbon from refinery tank bottom sludge. Effort has been made in this study to investigate the removal of hydrocarbon from refinery sludge by isolated biosurfactant-producing Pseudomonas aeruginosa RS29 strain and explore the biosurfactant for its composition and stability. Laboratory investigation was carried out with this strain to observe its efficacy of removing hydrocarbon from refinery sludge employing whole bacterial culture and culture supernatant to various concentrations of sand-sludge mixture. Removal of hydrocarbon was recorded after 20 days. Analysis of the produced biosurfactant was carried out to get the idea about its stability and composition. The strain could remove up to 85 ± 3 and 55 ± 4.5 % of hydrocarbon from refinery sludge when whole bacterial culture and culture supernatant were used, respectively. Maximum surface tension reduction (26.3 mN m-1) was achieved with the strain in just 24 h of time. Emulsification index (E24) was recorded as 100 and 80 % with crude oil and n-hexadecane, respectively. The biosurfactant was confirmed as rhamnolipid containing C8 and C10 fatty acid components and having more mono-rhamnolipid congeners than the di-rhamnolipid ones. The biosurfactant was stable up to 121 °C, pH 2-10, and up to a salinity value of 2-10 % w/v. To our knowledge, this is the first report showing the potentiality of a native strain from the northeast region of India for the efficient removal of hydrocarbon from refinery sludge. © 2013 Springer-Verlag Berlin Heidelberg.


Gogoi B.,Institute of Advanced Study in Science and Technology IASST | Paul N.,Institute of Advanced Study in Science and Technology IASST | Chowdhury D.,Material Nanochemistry Laboratory | Sarma N.S.,Institute of Advanced Study in Science and Technology IASST
Journal of Materials Chemistry C | Year: 2015

The detection of an ultra-trace amount of picric acid has attracted substantial attention from the perspective of health, safety and environment. Due to its very low vapour pressure, the detection of picric acid vapour is quite challenging in comparison to that of the liquid phase. In this work, we have overcome this problem by developing layer by layer polymer detectors and an electronic prototype for instant detection of a ppm level concentration of picric acid vapour via impedance spectroscopy. The detectors constitute mainly two polymer layers with poly-cholesteryl methacrylate sulfonated hexene as the two outer layers and a copolymer of 2-vinyl pyridine with acrylonitrile as the middle layer. In the presence of the analyte, the detectors undergo a steep decrease in impedance within a few seconds. The thickness of the individual polymer layers plays a vital role and it was observed that the detector with thinner outer layers (0.25 mm) is more efficient as it shows about a 99% decrease in the impedance for 0.334 ppm of picric acid vapour within 10 seconds. The method is selective, the effect of varying humidity is negligible and the detection limit was found to be 0.006 ppm. Moreover, the detectors show reproducible results and are also consistent for a long period. Using these detectors, we have designed an electronic prototype for visual detection of picric acid at room temperature. Unlike other sophisticated techniques the prototype is simple, portable, and cost effective and can be used for the detection of higher grade explosives with various implications such as homeland security, forensic and criminal investigations and remediation of explosive manufacturing sites. © The Royal Society of Chemistry.


Gogoi N.,Institute of Advanced Study in Science and Technology IASST | Chowdhury D.,Institute of Advanced Study in Science and Technology IASST
Journal of Nanoscience and Nanotechnology | Year: 2014

In this work storage of silver nanoparticles (Ag NPs) in chitosan gel and its subsequent release for catalytic reduction processes is investigated. The generation of small sized metal nanoparticles which acts as catalyst is prerequisite to progress of a catalytic reaction. We show that Ag NPs extracted from chitosan gel are less than 5 nm so very effective in catalysis. Chitosan-Ag nanocomposite gels were prepared from two different approaches. The first approach involves in-situ incorporation of Ag nanoparticles into the reaction mixture while preparing the chitosan hydrogel and termed as chitosan-Ag-in-situ (CH-Ag-I) nanocomposite gel. And, in second approach already prepared chitosan hydrogel was placed in Ag NPs solutions, resulting in adsorption of Ag NPs and thus forming chitosan-Ag-ex-situ (CH-Ag-E) nanocomposite gel. The prepared gels were characterized by UV-Visible spectroscopy, Fourier transformed infra-red spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Scanning electron microscopy (SEM). Swelling studies showed that the CH-Ag-E exhibits efficient water absorption property compared to that of CH-Ag-I. In addition to efficient swelling properties the CH-Ag-E can also act as store house of Ag NPs that can be used to catalyze the reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP) as Ag NPs of this composite can be easily extracted just by treating with sodium borohydride which is not possible in case of CH-Ag-I. The rate of the reaction increases upto 10 fold when CH-Ag-E nanocomposite gel is used as catalyst in comparison to CH-Ag-I. The reduction reaction catalyzed by such Ag NPs follow zero order kinetics and dependent on the size of the Ag NPs loaded in the gel (CH-Ag-E) as well as on the amount of the gel used. We found that smaller is the size of the loaded Ag NPs in CH-Ag-E, more effective it is in catalyzing the reduction reaction. The CH-Ag-E gel also showed reusability with efficient catalysis. Copyright © 2014 American Scientific Publishers All rights reserved.


Borah S.N.,Institute of Advanced Study in Science and Technology IASST | Goswami D.,Institute of Advanced Study in Science and Technology IASST | Lahkar J.,Institute of Advanced Study in Science and Technology IASST | Sarma H.K.,Gauhati University | And 2 more authors.
BioControl | Year: 2015

Fusarium oxysporum f. sp. pisi (van Hall) Snyder & Hansen is an important pathogen of pea that causes wilt. The present study was carried out to evaluate the efficacy of rhamnolipid biosurfactant produced by newly isolated Pseudomonas aeruginosa strain SS14 as an antifungal agent against F. oxysporum f. sp. pisi in Pisum sativum L. The bacterial strain P. aeruginosa SS14 was isolated from crude oil contaminated soil and identified by 16S rDNA sequencing. The biosurfactant was characterized as rhamnolipid by FTIR and LC–MS analyses. Treatment of pea seeds and seedlings under natural conditions of light, temperature and humidity with the rhamnolipid at a concentration of 25 µg ml−1 prior to sowing or planting in pathogen laden soil resulted in complete suppression of characteristic wilt symptoms. The results demonstrate the possibility to develop a sustainable and eco-friendly control measure against F. oxysporum f. sp. pisi which is currently not available. © 2014, International Organization for Biological Control (IOBC).


Goswami D.,Institute of Advanced Study in Science and Technology IASST | Handique P.J.,Gauhati University | Deka S.,Institute of Advanced Study in Science and Technology IASST
Journal of Basic Microbiology | Year: 2014

Pokkah boeng disease on sugarcane caused by the fungus Fusarium sacchari results considerable damage to the crop leading to top rot, the most serious and advanced stage of pokkah boeng, where the growing point is killed and the entire top of the plant dies. In the present study, the effect of rhamnolipid biosurfactant as an antifungal agent against F. sacchari to control pokkah boeng disease was investigated. On the basis of surface tension reduction, 12 bacterial isolates were selected as potent biosurfactant producers and eight of them showed antagonistic effect against F. sacchari. Among the eight, the isolate DS9 was found as the effective inhibitor of the fungus in vitro which was further evaluated using its biosurfactant present in whole culture, cell-free culture supernatant and crude biosurfactant at various concentrations. Reductions of fungal growths were found more with crude biosurfactant. By sequencing 16S rRNA, DS9 was identified as P. aeruginosa and the produced biosurfactant was characterized as rhamnolipid by Liquid Chromatography-Mass Spectrometry (LC-MS) analysis. The rhamnolipid biosurfactant inhibits phytopathogenic fungi F. sacchari and therefore seems to be a good biocontrol agent to control pokkah boeng disease of sugarcane. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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