[Show abstract][Hide abstract] ABSTRACT: Surface modification of multiwall carbon nanotubes (MWCNT) was carried out by radio frequency (RF) plasma discharges of oxygen and nitrogen gases to improve their dispersibility. Various oxygen and nitrogen containing functional groups were incorporated as a result of plasma treatment and were confirmed through Fourier transform infrared spectroscopy (FTIR). The effect of plasma treatment on structural properties and morphology changes of MWCNTs was analyzed by Raman, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The morphological studies indicate that untreated MWCNT exists as closely packed with highly entangled bundle. During the plasma treatment, MWCNT tubes get disentangled. XRD, Raman and TEM confirmed the absence of any surface damage during plasma treatment. Functionalized carbon nanotubes exhibit high zeta potential values indicating their good dispersibility in water. The method offers a direct and dry means for functionalization of MWCNT without affecting the structure of MWCNT.
[Show abstract][Hide abstract] ABSTRACT: The development of green composites using different natural fiber reinforcements is an area of active research to reduce the environmental footprint. These composites have serious limitations with high water absorption and reduced mechanical strength. The objective of this work is to develop polymeric green composite form natural reinforcements — jute and rice husk, with improved water resistance and flexural characteristics. Rice husk and jute mat were chemically treated with acrylic acid and sodium hydroxide. The effective treatment conditions such as treatment temperature, time and concentration of the chemical to minimize water absorption, were determined. The effective acrylic acid concentration, temperature and time for acrylic treatment process were 10 volume percent, 60 °C and 4 hours for rice husk and 10 volume percent, 90 °C and 6 hours for jute mat respectively. The flexural properties were also reported for the composites. The surface chemistry, surface morphology and composition (hydroxyl, cellulose and hemicelluloses content) of the treated and untreated natural reinforcements were also analysed. It was observed that the acrylic treatment reduced the water absorption of the composites significantly with marginal reduction on mechanical property. Alkali treatment (using sodium hydroxide) improved the flexural strength of the rice husk reinforced composite, however it exhibits an adverse effect on water resistance properties.
Fibers and Polymers 04/2015; 16(4):902-910. DOI:10.1007/s12221-015-0902-3 · 0.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper reviews the recent advances in the field of polymer adhesion aided by plasma in biomedical field. The first part of the paper discusses the latest techniques available to improve the adhesion properties of polymers with a special focus on their application in biomedicine.
The mechanism of plasma surface modification has been described in the subsequent section. Methods by which plasma can enhance the adhesiveness of polymers have been divided into three categories: plasma surface modification, plasma deposition, and plasma nano/micro-structuring. Special attention
has been given to the enhancement of cell adhesion and proliferation, immobilization of bioactive molecules, and reduction in protein adsorption and platelet adhesion. The concluding section briefly compares all the techniques and sheds light onto some of the major challenges faced by this
[Show abstract][Hide abstract] ABSTRACT: Biotechnology continues to offer routes for many exciting and unique products. Researchers genetically altered goats with a spider gene. These goats produce milk that contains a protein that can be extracted to produce biosteel fibers for use in bulletproof vests. It is referred to as “biosteel” to highlight its strength comparable to steel. This review paper describes the important aspects of produced dragline spider silk proteins via cell culture techniques using silk genes derived from two species of weaving spiders. These fibers were tested for a number of mechanical properties and compared to natural spider silk. In effect, fibers of biosteel were able to absorb similar amounts of energy as natural spider silk by stretching further. As opposed to most other synthetic fibers, biosteel is ecofriendly both in terms of its composition and production process.
[Show abstract][Hide abstract] ABSTRACT: The surface property of a material plays an important role in determining its field of application. Polyurethane (PU) provides a good interface between material science and biomedicine as it is widely being used for biomedical applications as catheters, artificial vein etc. The extent of wetability and adhesion of this material determines its blood and bio compatibility inside the body. This study aims at improving the surface energy of PU by RF plasma treatment using three different gases: Argon (Ar), Nitrogen (N2) and Oxygen (O2). It was found that the water contact angle of O2 treated PU was the least because of the additional functionality introduced by the incorporation of O-H bond. The untreated and treated substrates for all the gases were measured for water, formamide and di iodomethane contact angle with the help of a static contact angle Goniometer. The incorporation of new functionalities was estimated by plasma diagnosis using Optical Emission Spectrophotometer (OES) and Fourier Transform Infrared Spectroscopy (FTIR) of the untreated and treated substrates. The extent of etching of the PU substrates was imaged using a Scanning electron Microscope (SEM) and the roughness parameter was estimated using a contact stylus Surface Profilometer. The roughness was found to be increased after the plasma treatment due to etching away of the substrate by the bombardment of ionic species generated in the plasma. Thus it can be concluded that the RF plasma treatment of PU with appropriate gas leads to significant reductions in contact angle making the surface hydrophilic and improving the bio compatibility (by proper adhesion to cells) and blood compatibility (by providing good wetting for blood) for use in biomedical applications.
3rd International Conference on Laser and Plasma Applications in Materials Science, Indian Institute of Technology Kharagpur, Indian Institute of Technology Kanpur, and Centre de Développement des Technologies Avancées , Algeria; 01/2015
[Show abstract][Hide abstract] ABSTRACT: Antimicrobial properties of nanoparticles have been studied extensively since past few years. Studies have shown that ZnO exhibits antimicrobial activity but there is very limited amount of literature which aims at applying these nanoparticles over the polymeric substrates (used as implants) and then testing for its antimicrobial activity. This work provides a comprehensive idea about the practical applicability of ZnO nanoparticles coated over Polymethyl methacrylate (PMMA) substrates (used in biomedical implants) and then testing for its desired antimicrobial applications. This study deals with the synthesis of ZnO nanoparticles (NPs) using sol gel technique, its characterization using Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Brunauer–Emmett–Teller (BET) and Fourier Transform Infrared (FTIR) spectroscopy. The synthesized nanoparticles had an average size of approximately 22 nm and were nearly spherical in shape. The synthesized nanoparticles were then coated onto argon plasma treated polymethyl methacrylate (PMMA) substrates and then assessed for their antimicrobial activity using zone of inhibition test. The presence of a sharp zone, as shown in Figure 1, suggested the good antimicrobial activity of these particles when coated over polymeric biomedical implants.
Nano-engineering in Medicine Workshop, All India institute of Medical Science Delhi, http://www.nature.com/natureevents/science/events/26427-Nanoengineering_in_Medicine; 12/2014
[Show abstract][Hide abstract] ABSTRACT: The effect of temperature pre-exposure on locomotion and chemotaxis of the soil-dwelling nematode Caenorhabditis elegans has been extensively studied. The behavior of C. elegans was quantified using a simple harmonic curvature-based model. Animals showed increased levels of activity, compared to control worms, immediately after pre-exposure to 30°C. This high level of activity in C. elegans translated into frequent turns by making 'complex' shapes, higher velocity of locomotion, and higher chemotaxis index ([Formula: see text]) in presence of a gradient of chemoattractant. The effect of pre-exposure was observed to be persistent for about 20 minutes after which the behavior (including velocity and [Formula: see text]) appeared to be comparable to that of control animals (maintained at 20°C). Surprisingly, after 30 minutes of recovery, the behavior of C. elegans continued to deteriorate further below that of control worms with a drastic reduction in the curvature of the worms' body. A majority of these worms also showed negative chemotaxis index indicating a loss in their chemotaxis ability.
PLoS ONE 10/2014; 9(10):e111342. DOI:10.1371/journal.pone.0111342 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Rice mill effluent contains high concentration of organic and inorganic substances leading to significant source of pollution. The effluent has high Biological oxygen demand (BOD), Chemical oxygen demand (COD), and Total Dissolved solid (TDS). The major advantage of electrocoagulation is that it avoids the usage of any chemicals and so there is no need for neutralizing agents. The effective performance of this technique in the treatment of rice mill wastewater has been investigated using a combination of aluminum and iron electrodes. After the treatment, BOD, COD, and dissolved solids were sufficiently reduced. In addition, it was found that an increase in the current density enhanced the speed of the treatment significantly and the Fe-Fe electrode combination gave the highest removal efficiency.
[Show abstract][Hide abstract] ABSTRACT: Tri-layered reduced graphene oxide with better graphitization was synthesized and functioned using radio frequency N2 and O2 plasma. The layer numbers of reduced graphene oxide were determined by atomic force microscopy (AFM) and x-ray diffraction (XRD). The effect of plasma treatment on crystal structure, surface morphology and chemical composition were studied from XRD, transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), Fourier transforms infrared spectroscopy (FTIR) and Raman spectroscopy. The chemical species present in N2/O2 plasma during functionalization of tri-layered reduced graphene oxide was analyzed by optical emission spectroscopy. Tri-layered reduced graphene oxide and functioned tri-layered reduced graphene oxide exhibits higher electrochemical performance towards ferrocyanide redox reaction than glassy carbon and platinum electrode with much decrease in overpotential. This indicates that tri-layered reduced graphene oxide and N2/O2 functionalized tri-layered reduced graphene oxide are promising working electrodes in the application of electrochemical based biosensor.
[Show abstract][Hide abstract] ABSTRACT: Graphene, a 2D nanomaterial, having large surface area than other carbon based nanomaterials like carbon nanotube, fullerene, graphite and diamond, can be used in wide range of applications in various fields. Inert property of pristine graphene limits its application in biomedical field. The limitation can be overcome by plasma functionalizing graphene which make graphene hydrophilic with less morphological change than chemical functionalization. In this work reduced graphene oxide was synthesized by chemical method and it was functionalized by using oxygen and nitrogen radio frequency plasma. Synthesized reduced graphene oxide was characterized by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Functional group attached over reduced graphene oxide was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The surface area and thermal stability of plasma treated and untreated reduced graphene oxide was studied by using surface area analyzer and thermo gravimetric analyzer.
[Show abstract][Hide abstract] ABSTRACT: Plasma surface modification is a widely accepted technique to enhance the surface properties of polymeric materials. Effect of RF plasma treatment on the surface properties of Polyvinyl chloride (PVC), Polycarbonate (PC) and polypropylene (PP) substrates were observed for three different gases argon, nitrogen and oxygen. Changes in water contact angle were studied by the sessile drop method using Goniometer. Taking a specific case of argon plasma treatment of PVC, surface morphological changes were observed through SEM at various levels of process variables. FTIR analysis was made to investigate the changes in chemical structure of PVC after RF plasma treatment. Optical emission spectroscopic (OES) studies were made to characterize the excitation and ionization process of atomic and molecular species in argon plasma. The experiments were run through central composite design of response surface methodology to optimize and study the effect of power, flowrate and treatment time on the surface energy and weight loss of PVC.
INTERNATIONAL CONFERENCE on ADVANCES IN CHEMICAL ENGINEERING ICACE-2013, National Institute of Technology Raipur, http://www.nitrr.ac.in/icace2013/index.htm; 04/2013
[Show abstract][Hide abstract] ABSTRACT: Surface modification of polypropylene by nitrogen containing plasma was performed in this work in order to improve the wettability which resulted in enhanced biocompatibility and blood compatibility. Various nitrogen containing functional groups as well as oxygen containing functional groups were found to be incorporated to the polymer surface during plasma treatment and post plasma reaction respectively. Wettability of the polymers was evaluated by static contact angle measurement to show the improvement in hydrophilicity of plasma treated polypropylene. Cross linking and surface modification were reported to be dominating in the case of nitrogen plasma treatment compared to degradation. The effect of various process variables namely power, pressure, flow rate and treatment time on surface energy and weight loss was studied at various levels according to the central composite design of response surface methodology (RSM). Except pressure the other variables resulted in increased weight loss due to etching whereas with increasing pressure weight loss was found to increase and then decrease. The effect of process variables on surface morphology of polymers was evaluated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Well spread fibroblast cells on nitrogen plasma treated polypropylene due to the presence of CO, NH2+ and NH+ was observed. Reduced platelet adhesion and increased partial thromboplastin time evidenced the increased blood compatibility.
Materials Science and Engineering C 10/2012; 32(7):1767–1778. DOI:10.1016/j.msec.2012.04.034 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polymers very often do not possess the surface properties needed for these applications. However, they have excellent bulk physical and chemical properties and are inexpensive and easy to process. For these reasons, surface modification techniques which can transform these inexpensive materials into highly valuable finished products have become an important part of the plastics and many other industries. Among the various surface modification methods plasma treatment is a widely accepted technique to modify the surface properties of the materials without affecting their bulk properties, which is also economical and eco-friendly. The effect of plasma treatment on the surface properties of Polyvinyl chloride (PVC), Polycarbonate (PC) and polypropylene (PP) substrates were observed. PVC, PC and PP strips were exposed to Radio frequency (RF) plasma of three different gases argon, nitrogen and oxygen. Contact angle measurements were done on polymer surfaces before and after plasma treatment, to study the wettability changes, by the sessile drop method goniometer at ambient humidity and temperature. Decrease in contact angle was observed after the plasma treatment which increases gradually to a certain point as a result of aging (hysteresis). Surface energy calculations are made by measuring the contact angles, with polar solvents like formamide, and water and non polar solvents like di iodomethane, of plasma treated samples with three different gases. The surface morphology was examined with Scanning Electron Microscope (SEM). FTIR analysis showed the chemical structure of PVC, PC and PP surfaces modified with plasma. Optical emission spectroscopic (OES) measurements were used to characterize the excitation and ionization process of atomic and molecular species in argon, oxygen and nitrogen plasma under different discharge conditions. The mechanism involved in surface modification of PVC, PC and PP is investigated.
Chemference 2012, Indian Institute of Technology Kharagpur; 01/2012
[Show abstract][Hide abstract] ABSTRACT: Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon–oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C–O and –CO functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.
[Show abstract][Hide abstract] ABSTRACT: The Intrauterine Devices (IUDs) are unable to prevent STDs (Sexually Transmitted Diseases) and PIDs (Pelvic Inflammatory Diseases) which seriously restricts their usage. RISUG (Reversible Inhibition of Sperm under Guidance), a potent spermicidal and antimicrobial drug is being coated over copper-T frame (made of polyethylene) by exposing it to vacuum plasma treatment twice to increase the adhesion property of polyethylene. First, the polyethylene alone is exposed to certain process conditions of RF (radiofrequency) plasma which increases the surface roughness by creating micro-and nano-pores (as indicated by scanning electron microscopy and atomic force microscopy). Thereafter RISUG is smeared over the polyethylene of copper-T frame and subjected to the same plasma treatment again. The second plasma treatment causes a "micro-hammering" effect, pushing the drug in the pores and pits formed by the first plasma treatment, resulting in improved bonding. The present study shows that RF plasma treatment alters the surface properties of the copper-T frame without affecting its mechanical properties or primary fabrication.
Journal of Adhesion Science and Technology 01/2011; 25(1-3):151-167. DOI:10.1163/016942410X503285 · 0.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Staphylococcus aureus is one of the most common pathogens responsible for hospital-acquired infections. In this study, S. aureus was exposed to 13.56MHz radiofrequency (RF) plasma generated by two different gases namely nitrogen and nitrogen-oxygen mixture and their sterilization efficacies were compared. Nitrogen plasma had a significant effect on sterilization due to generation of ultraviolet (UV) radiation. However, the addition of 2% oxygen showed enhanced effect on the sterilization of bacteria through nitric oxide (NO) emission and various reactive species. The presence of these reactive species was confirmed by optical emission spectroscopy (OES). Scanning electron microscopy (SEM) analysis was carried out to study the morphological changes of bacteria after plasma treatment. From the SEM results, it was observed that the bacterial cells treated by N(2)-O(2) mixture plasma were severely damaged. As a result, a log(10) reduction factor of 6 was achieved using N(2)-O(2) plasma after 5min treatment with 100W RF power.
International Journal of Pharmaceutics 08/2010; 396(1-2):17-22. DOI:10.1016/j.ijpharm.2010.05.045 · 3.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Radiofrequency discharge of helium gas at low pressure was employed to modify surface properties of polycarbonate. The effects of process parameters on wettability and plasma etching were determined by monitoring surface energy and weight loss, respectively. Quadratic equations for surface energy and weight loss, in terms of process variables, namely power, pressure, flowrate and treatment time were developed. Multiple response optimization was performed using central composite design (CCD) of response surface methodology (RSM) to maximize the surface energy and minimize the weight loss. Helium plasma treated polycarbonate resulted in increased hydrophilicity. From optical emission spectroscopic studies helium was identified as excited and metastable atom and ions which caused surface chemistry and morphology changes. Enhanced biocompatibility in terms of increased cell adhesion and proliferation was observed for all plasma treatment conditions. Confluent cell growth was observed with helium plasma treated polycarbonate. Both reduced platelet adhesion and increased partial thromboplastin time (increased to 204 s from 128 s corresponding to untreated polycarbonate) confirm the improved blood compatibility of plasma treated polycarbonate.
Journal of Adhesion Science and Technology 01/2010; 24(13-14):2237-2255. DOI:10.1163/016942410X511088 · 0.96 Impact Factor