Papers by Suprakas Sinha Ray
Crystallization behavior, kinetics and morphology of environmentally friendly polymer nanocomposites using biodegradable polymer matrices and clay/carbon nanotube (CNT) reinforcements
Environmentally Friendly Polymer Nanocomposites, 2013
Most environmentally friendly polymers are semicrystalline and, therefore, the physical and mecha... more Most environmentally friendly polymers are semicrystalline and, therefore, the physical and mechanical properties of these polymers are controlled by the crystallization process. Hence, it is necessary to study the effects of nanofillers on the crystallization behavior, that is, the morphology and kinetics of the environmentally friendly polymer matrices to establish the structure–property relationships in these nanocomposites. This chapter analytically summarizes the effects of nanoparticles in clay or carbon nanotube-containing environmentally friendly nanocomposites on parts of the crystallization process, such as the crystal growth behavior and crystallization kinetics.
Thermal stability and flammability of environmentally friendly polymer nanocomposites using biodegradable polymer matrices and clay/carbon nanotube (CNT) reinforcements
Environmentally Friendly Polymer Nanocomposites, 2013
The homogeneous dispersion of nanoparticles in a biodegradable polymer matrix also enhances the t... more The homogeneous dispersion of nanoparticles in a biodegradable polymer matrix also enhances the thermal degradation temperature and flammability of environmentally friendly polymer nanocomposites. Thermogravimetric analysis is the main technique used to study the thermal stability of polymeric materials, and the cone calorimeter test is one of the most extensively used bench-scale methods for studying the flammability properties of polymeric materials. This chapter highlights the effects of incorporation of clay and carbon nanotube dispersions on the thermal stability and flammability of biodegradable polymers.
South African Journal of Science, 2010
Carbohydrate Polymers, 2017
Nanoparticles were isolated from tef and maize starch modified with added stearic acid after past... more Nanoparticles were isolated from tef and maize starch modified with added stearic acid after pasting at 90 °C for 130 min. This was followed by thermo-stable alphaamylase hydrolysis of the paste. The resultant residues were then characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic laser scattering particle size distribution (DLPSD), atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). XRD and DSC showed that the isolated residues consisted of amylose-lipid complexes. These complexes were type II with melting temperature above 104 °C. DLPSD, AFM and HRTEM showed that the isolated tef and maize starch residues consisted of nanoparticles which became more distinct with increased hydrolysis time. The isolated tef and maize nanoparticles had distinct particles of about 3-10 nm and 2.4-6.7 nm, respectively and the yield was about 24-30%. The results demonstrated that distinct (physically separate) nanoparticles of less than 10 nm can be isolated after formation during pasting of tef and maize starch with stearic acid. The production and isolation of the nanoparticles uses green chemistry principles and these nanoparticles can be used in food and non-food systems as nanofillers.
Nonisothermal crystallization kinetics of poly(ethylene terephthalate) nanocomposites
Journal of Nanoscience and Nanotechnology, May 1, 2008
ABSTRACT The article deals with the melting and nonisothermal crystallization behavior of neat po... more ABSTRACT The article deals with the melting and nonisothermal crystallization behavior of neat poly (phenylene sulphide) (PPS) and its composites with a thermotropic liquid crystalline polymer (TLCP)—Vectra A950, prepared by melt mixing and probed by differential scanning calorimetry. The various macrokinetic models namely, the Ozawa, the modified Avrami, the Tobin, and the Mo models were applied to describe the crystallization kinetics under nonisothermal conditions. The kinetic crystallizabilty of PPS/TLCP composites calculated using the approach of Ziabicki varies depending on these two composite composition-induced effects. Similarly Mo model predicts that to obtain a higher degree of crystallizabilty for PPS/TLCP composites, a higher cooling rate should be used. The effective energy barrier based on the differential isoconversional method of Friedman is found to be an increasing function of relative degree of melt conversion. The effect is explained in terms of nucleation theory proposed by Wunderlich to crystallization of polymers. The Lauritzen–Hoffman parameters are estimated using G = 1/t0.5 effective activation energy equation proposed by Vyazovkin and Sbirrazzuoli. The Kg values estimated from latter equations are more comparable with values obtained using isothermal crystallization data than 1/t0.5 method. Furthermore, the kinetic analysis using this equation shows a regime transition from regime II to regime III for 100/00, 90/10, 80/20 PPS/TLCP composites, basically attributed to reduced mobility of PPS chains in composites. This regime II to III transition is accompanied by a morphological transition from defective spherulitic sheaf-like structures to ordered sheaf-like structures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1070–1100, 2010
Ceramic Engineering and Science Proceedings, 2011
This work describes a comparison between two chemical functionalization strategies for the amine ... more This work describes a comparison between two chemical functionalization strategies for the amine functionalization of multi walled CNTs. In the first procedure, the CNTs are functionalized in direct amination process that avoids the use of strong acids or acid chloride unlike the conventional functionalization methods whereas the second method is a two step procedure involving mild acid treatment followed by amidation. Both procedures allow not only to control of amine content on the CNT surface but also to obtain remarkable degree of fictionalization. The functionalization of CNTs is confirmed by analytical techniques like scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The modified CNTs with optimum amine content are used to prepare Polylactide (PLA) /CNT nanocomposites with improved properties through solution casting method.
Beyond Poiseuille: Over-limiting Fluid Flows through Macroscopically Long Carbon Nanochannels 1 S... more Beyond Poiseuille: Over-limiting Fluid Flows through Macroscopically Long Carbon Nanochannels 1 S. SINHA RAY, A.L. YARIN, Dept of Mech. and Industrial Engr., UIC -Nanotubes and nanochannels have tremendous potential in various fields like drug delivery, DNA segregation, capillary electrophoresis etc. Except coelectrospinning all the methods result in nanotubes sufficiently small in diameter (1-100 nm) but not longer than several micron precluding easy manipulation making them almost unsuitable for installing in nanofluidic devices for studying fluid flow characteristics. In this work we developed macroscopically long (∼1 cm) carbon nanochannels and studied flow characteristics in them. Then, we demonstrated that bi-layer flows of liquid and gas can result in an over-limiting regime, where a higher flow rate of liquid can be achieved as compared to the case when the same liquid flows through the same tube subjected to the same pressure drop and occupies the whole bore. This paradoxical result is because the less viscous gas layer can flow much faster than the underlying liquid layer and entrain the latter via a significant shear stress. The present results show that the over-limiting liquid flows through nanotubes, seemingly resembling a deviation from the no-slip condition, in reality are entrained by a rapidly moving gas layer in bi-layer liquid/gas flows. This quasi-slip phenomenon happens in relatively large nanotubes (∼500 nm) where the no-slip condition holds with sufficient accuracy, which can be beneficial in micro-and nanofluidics, nanoreactors and drug delivery systems, which are the current goals of this team.
A record of amphidelphic reflexed ovaries in Helicotylenchus dihystera (Nematoda: Hoplolaimidae)
Indian Journal of Nematology, 1982
Ceramic engineering and science proceedings, Nov 15, 2011
The new metal-free phthalocyanine 2 and metallophtalocyanines 3, 4, 5, 6 containing 9-flourene me... more The new metal-free phthalocyanine 2 and metallophtalocyanines 3, 4, 5, 6 containing 9-flourene methanol units on peripheral positions have been synthesized by cyclotetramerization reaction of a corresponding nitrile compound. The metal-free phthalocyanine 2 was synthesized in dry n-pentanol by a classical method. Hovewer, metal phthalocyanines complexes 3, 4, 5, 6, were synthesized by the reaction of dinitrile derivative 2 in DMAE, by microwave irradiation. The structure of the new compounds were characterized by using spectroscopic data and elemental analysis.
Ceramic Engineering and Science Proceedings, 2011
This paper discusses various properties of Poly(lactide) upon nanocomposite formation with functi... more This paper discusses various properties of Poly(lactide) upon nanocomposite formation with functionalized multiwalled carbon nanotubes (f-MWCNTs). The composite was prepared through melt extrusion technique. Functionalization of carbon nanotubes and possible interaction with PLA chains was investigated through attenuated total reflectance (ATR) Fourier transformed-infrared (FT-IR) and Raman spectroscopies. Scanning electron microscope (SEM) and polarized optical microscope (POM-in melt state) also revealed homogenous dispersion of f-MWCNTs in the PLA matrix with some agglomerates. Melting and crystallization phenomena of the nanocomposite studied through differential scanning calorimeter (DSC), wide angle X-ray scattering (WAXS), and POM show that f-MWCNTs facilitates nucleation and crystal growth of PLA matrix significantly. Thermogravimetric analyses (TGA) reveal that overall thermal stability of PLA matrix improves slightly upon the nanocomposite formation. Thermomechanical analyses also reveal a significant increase in modulus of the nanocomposite at room temperature, which drops suddenly across glass transition temperature. This is an indication of plasticization effect.
Advances in Nanocomposites - Synthesis, Characterization and Industrial Applications, 2011
Impact of non-ionic surfactant chemical structure on morphology and stability of polystyrene nanocomposite latex
Colloid and Polymer Science, 2015
AbstractPolystyrene (PS) colloid particles in presence of non-ionic surfactant-modified clay part... more AbstractPolystyrene (PS) colloid particles in presence of non-ionic surfactant-modified clay particles were prepared by the free-radical polymerization of styrene monomers in emulsion. Three different types of non-ionic surfactants, sorbitan monopalmitate (Span®40), polyethylene glycol octadecyl ether (Brij®S10), and polyoxyethylene (9) nonylphenylether (Igepal®Co-630) were used for the preparation of surfactant-modified clay. High-resolution transmission electron microscopy studies showed that few colloid PS particles with clay mineral layers at the surface were obtained; the particle sizes were observed to be in the micrometer size range, and stable dispersions were obtained when Span®40 and Igepal®Co-630 modified clay minerals were used as stabilizers. The clay mineral particles were observed to be mostly encapsulated by PS latex particles, and a typical morphology was observed when Brij®S10-modified clay was used as a stabilizer. This strategy can be applied to develop stable polymer latex particles via emulsion polymerization. Graphical AbstractThe formation of stable polystyrene colloidal particles using non-ionic surfactant modified clay mineral
Polylactide-Based Nanocomposites
Yu/Biodegradable Polymer Blends, 2009
Page 1. &CHAPTER 16 Polylactide-Based Nanocomposites SUPRAKAS SINHA RAY and JAMES RAM... more Page 1. &CHAPTER 16 Polylactide-Based Nanocomposites SUPRAKAS SINHA RAY and JAMES RAMONTJA National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria 0001, Republic of South Africa 16.1 Introduction 389 ...
Applied Clay Science, 2015
Gram-positive bacteria Silver and zinc oxide nanoparticles This study was conducted to develop no... more Gram-positive bacteria Silver and zinc oxide nanoparticles This study was conducted to develop novel chitosan nanocomposites and to optimize the minimum amount and 23 contact time required to achieve complete inactivation of bacteria in water. Gram-negative Escherichia coli and 24 Gram-positive Enterococcus faecalis bacteria were used to test the antibacterial activity of chitosan cross-linked 25 with glutaraldehyde and chitosan nanocomposites in water. The silver and zinc oxide nanoparticles supported 26 on bentonite were synthesized using microwave-assisted synthesis method. The resulting bentonite-27 supported silver and zinc oxide nanoparticles were dispersed in a chitosan biopolymer to prepare bentonite 28 chitosan nanocomposites. The obtained bentonite chitosan nanocomposites were characterized with BET surface 29 area measurements, FTIR, XRD, ICP-AES and SEM. When using cross-linked chitosan, it was demonstrated that 30 factors such as pH, particle size and surface area influenced the inactivation of bacteria. For instance, the antibac-31 terial activity of cross-linked chitosan was illustrated to increase with an increase in contact time. Meanwhile, an 32 improvement in the inactivation activity was indicated with the introduction of silver and zinc oxide nanoparti-33 cles containing bentonite into the chitosan matrix. Although both silver and zinc oxide containing bentonite 34 chitosan nanocomposites exhibited good antibacterial activity against bacteria, with removal efficiencies of at 35 least 51%, the best antibacterial activity was demonstrated for silver-zinc oxide bentonite chitosan nanocomposite, 36 with a removal efficiency of at least 78%. Furthermore, the antibacterial activity of bentonite chitosan nanocompos-37 ites was identified to be influenced by the amount of material, contact time and bacterial concentration. Finally, 38 leaching tests demonstrated that bentonite chitosan nanocomposites were stable and, consequently, could be 39 effectively used as antibacterial materials for water disinfection.
LuytPaper-MacromolMaterEng294(2009)839
Applied Surface Science, 2015
We report the chemical synthesis of various ZnO nanostructures and TiO2 nanoparticles and their d... more We report the chemical synthesis of various ZnO nanostructures and TiO2 nanoparticles and their dispersion in a P3HT matrix. The photoluminescence studies revealed improved charge transport in the active layer of the optimized TiO2 nanoparticles at a wt. ratio of 0.33, which demonstrated enhanced effective exciton dissociation at the interfaces between the P3HT, ZnO and TiO2 domains. The influence of the synthesis reaction time for the various ZnO nanostructures and TiO2 nanoparticles on the solar cell performances was investigated by varying the TiO2 concentration. The device containing a 0.33 wt. ratio of TiO2 nanoparticles in ITO/SnO2/P3HT:ZnO(24-h):TiO2/MoO3/Al ternary system showed a maximum efficiency of 2.84% under AM 1.5G illumination.
Journal of Nanomaterials, 2012
The SnO2/CNT composites were prepared by microwave-assisted wet impregnation at 60°C. The process... more The SnO2/CNT composites were prepared by microwave-assisted wet impregnation at 60°C. The process was optimized by varying the microwave power and reaction time. Raman analysis showed the typical features of the rutile phase of as-synthesized SnO2nanoparticles on CNTs, which was consistent with the results from X-ray diffraction. Enhanced field emission performance was observed for SnO2/CNTs composite prepared by a microwave method when compared to pure CNTs and SnO2/CNTs composite prepared by conventional wet impregnation. The dependence of emission current density on the electric field followed a Fowler-Nordheim relationship.
Chemical Engineering Journal, 2015
The aim of this work was to study the adsorption behavior of the nanosilica-containing hydrogel n... more The aim of this work was to study the adsorption behavior of the nanosilica-containing hydrogel nanocomposite of gum karaya grafted with poly(acrylic acid-acrylamide) (GK-cl-P(AA-co-AAM)) in the adsorption of methylene blue (MB) from aqueous solutions. The hydrogel nanocomposite was synthesized by the base-catalyzed hydrolysis and water condensation reactions of tetraethylorthosilicate in an aqueous medium containing a dispersion of GK-cl-P(AA-co-AAM). Structural and morphological characterizations using Fourier transform infrared spectroscopy, X-ray diffraction, and transmission and scanning electron microscopies supported the formation of the grafted hydrogel polymer of GK and the SiO(sub2)-containing nanocomposite. The Brunauer-Emmett-Teller adsorption studies showed that the surface area and porosity of the hydrogel polymer significantly increased after nanocomposite formation with SiO(sub2). The hydrogel nanocomposite was employed for the removal of MB from an aqueous solution: 96% of the MB was removed with a hydrogel nanocomposite dose of 0.2 g L(sup-1). The adsorption process was found to follow pseudo-second-order kinetics, and the adsorption isotherm was best fitted with the Langmuir monolayer isotherm model with a maximum adsorption capacity of 1408.67 mg g(sup-1), which was much higher than that of the hydrogel polymer. Different adsorption thermodynamic parameters supported the endothermic nature as well as the spontaneity of the adsorption process. The hydrogel nanocomposite showed excellent regeneration capacity in the acidic medium and was successfully used over three adsorption-desorption cycles. Therefore, the GK-cl-P(AA-co-AAM)/SiO(sub2) hydrogel nanocomposite has shown potential as an efficient adsorbent for the highly effective removal of cationic dyes from aqueous solution.
International Journal of Biological Macromolecules, 2015
Biodegradable hydrogels of gum ghatti (Gg) with a co-polymer mixture of acrylamide (AAm) and meth... more Biodegradable hydrogels of gum ghatti (Gg) with a co-polymer mixture of acrylamide (AAm) and methacrylic acid (MAA) (termed as Gg-cl-P(AAm-co-MAA)) were synthesised by microwave-assisted free radical graft co-polymerisation technique. The hydrogel polymer was characterized by FTIR, SEM, and Brunauer-Emmett-Teller techniques. The Gg-cl-P(AAm-co-MAA) hydrogel was studied as an adsorbent for the removal of methylene blue (MB) and methyl violet (MV) from aqueous solutions. Adsorption of both the dyes followed pseudo-second-order kinetics and Langmuir adsorption isotherm models. The hydrogel polymer adsorbed 98% of MB and 95% of MV from aqueous solution. The Gg-cl-P(AAmco-MAA) maintained its original sorption capacity for three cycles of adsorption-desorption. Furthermore, the hydrogel polymer degraded fully within 50 days in soil compost. In summary, the Gg-cl-P(AAm-co-MAA) hydrogel could be a potential adsorbent for the remediation of dyes from industrial wastewater.
Applied Catalysis A: General, 2015
Nanostructured vanadium-tin oxide (V(sub2)O(sub5)/SnO(sub2)) catalysts with V(sub2)O(sub5) loadin... more Nanostructured vanadium-tin oxide (V(sub2)O(sub5)/SnO(sub2)) catalysts with V(sub2)O(sub5) loading in a range of 5-20 wt% have been synthesized. The V(sub2)O(sub5)/SnO(sub2) nanostructures exhibited effective catalytic performance in the hydroxylation of benzene to phenol using H(sub2)O(sub2) as the terminal oxidant. The structure of the catalysts was studied using various techniques, such as XRD, Raman spectroscopy, SEM, EDX, TEM/HRTEM, STEM-HAADF, and H2-TPR and the adsorption/desorption of nitrogen. The Raman study supported the formation of certain monomeric and polymeric surface vanadium species and a crystalline V(sub2)O(sub5) phase on their respective dehydrated mixed V(sub2)O(sub5)/SnO(sub2) nanostructured catalysts depending on the vanadium loading. TEM studies revealed the morphology of V2O5 and SnO2 to be characterized by the formation of nanoparticles with a size of approximately 20 nm. Moreover, the dispersion of V(sub2)O(sub5) on SnO(sub2) was also found to be influenced by V(sub2)O(sub5) loading where a high loading of 20 wt% exhibited an agglomeration of particles, which affected its catalytic activity. The V(sub2)O(sub5)/SnO(sub2) catalysts resulted in modified redox properties, as evidenced by the H2-TPR results. These structural developments of mixed V(sub2)O(sub5)/SnO(sub2) presented a highly active catalyst for the hydroxylation of benzene to phenol affording up to a 34% conversion, while preserving a phenol selectivity of 96% for a sample of V(sub2)O(sub5)/SnO(sub2) containing 10 wt% V(sub2)O(sub5). The catalytic results indicated that the vanadium content in V(sub2)O(sub5)/SnO(sub2) played an important role not only in improved substrate conversion but also in preserving a high selectivity for phenol. This was also evident from the correlation of the different vanadium phases for pure and composite catalysts with their respective catalytic results. Both polymeric and monomeric vanadium species on an SnO(sub2) surface proved to be critical for the high catalytic performance of the catalyst. The high catalytic performance displayed by V(sub2)O(sub5)/SnO(sub2) can provide opportunities for further development as a green and economical protocol for direct phenol synthesis from benzene hydroxylation with excellent catalyst recyclability.
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Papers by Suprakas Sinha Ray