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Pan A.,Jadavpur University | Naskar B.,Jadavpur University | Prameela G.K.S.,Central Research Institute for Physics | Kumar B.V.N.P.,Central Research Institute for Physics | And 3 more authors.
Langmuir | Year: 2012

Mixed aquo-organic solvents are used in chemical, industrial, and pharmaceutical processes along with amphiphilic materials. Their fundamental studies with reference to bulk and interfacial phenomena are thus considered to be important, but such detailed studies are limited. In this work, the interfacial adsorption of sodium dodecylsulfate (SDS, C12H 25SO4-Na+) in dioxane-water (Dn-W) and methanol-water (Ml-W) media in extensive mixing ratios along with its bulk behavior have been investigated. The solvent-composition-dependent properties have been identified, and their quantifications have been attempted. The SDS micellization has been assessed in terms of different solvent parameters, and the possible formation of an ion pair and triple ion of the colloidal electrolyte, C12H25SO4-Na+ in the Dn-W medium has been correlated and quantified. In the Ml-W medium at a high volume percent of Ml, the SDS amphiphile formed special associated species instead of ion association. The formation of self-assembly and the energetics of SDS in the mixed solvent media have been determined and assessed using conductometry, calorimetry, tensiometry, viscometry, NMR, and DLS methods. The detailed study undertaken herein with respect to the behavior of SDS in the mixed aquo-organic solvent media (Dn-W and Ml-W) is a new kind of endeavor. © 2012 American Chemical Society.

Bhange P.,CSIR - National Chemical Laboratory | Bhange P.,Korean University of Science and Technology | Bhange D.S.,CSIR - National Chemical Laboratory | Bhange D.S.,Shivaji University | And 3 more authors.
Applied Catalysis A: General | Year: 2011

The synthesis of Al-SBA-15 under milder acidic conditions were made through an adjusting the molar H2O/HCl ratio which indicate the formation of Si-O-Al linkages that lead to isomorphous substitution of Si4+ by some Al3+ ions. By adjusting the H2O/HCl molar ratio, Al gets incorporated into the lattice of SBA-15, which is evidenced by XRD, N 2 adsorption, TEM, 29Si and 27Al MAS NMR spectroscopic data. Aluminium incorporated SBA-15 samples retained both structural and textural properties of SBA-15. The 27Al MAS NMR confirms that a large proportion of the Al is inserted into tetrahedral positions within the framework. The Al3+ ions could assume a tetrahedral coordination and be part of the hexagonal structure of silica in Al-SBA-15. In the present study, we have examined the effectiveness of Al-SBA-15, as an acid catalyst for the esterification of acetic acid and in benzylation of anisole. The high activity of Al-20 sample in esterification reaction has been attributed to isolated, generally tetrahedrally coordinated, framework Al species. While in benzylation of anisole, the best result was achieved with Al-5 catalyst. The selectivity for benzylanisole increases and that for dibenzylether decreases with increase in the Si/Al ratio of Al-SBA-15. © 2011 Elsevier B.V.

Bernido C.C.,Central Research Institute for Physics | Carpio-Bernido M.V.,Central Research Institute for Physics | Escobido M.G.O.,Asian Institute of Management
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2014

Fluctuations in a time series for tropical cyclone tracks are investigated based on an exponentially modified Brownian motion. The mean square displacement (MSD) is evaluated and compared to a recent work on cyclone tracks based on fractional Brownian motion (fBm). Unlike the work based on fBm, the present approach is found to capture the behavior of MSD versus time graphs for cyclones even for large values of time. © 2014 Elsevier B.V.

Bhuvanasree S.R.,CSIR - Central Leather Research Institute | Harini D.,CSIR - Central Leather Research Institute | Rajaram A.,Central Research Institute for Physics | Rajaram R.,CSIR - Central Leather Research Institute
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2013

The present study focuses on the rapid synthesis of gold nanoparticles (AuNP) using the aqueous extract of Cissus quadrangularis (CQE) by microwave irradiation. The UV-Visible spectroscopy of the solution obtained from reduction of hydrogen tetrachloroaurate (HAuCl4) by CQE revealed a sharp surface plasmon resonance (SPR) peak at 530 nm confirming the presence of AuNP. The formation of AuNP was optimal at a pH of 9. The AuNP was characterised by FT-IR, SEM, HR-TEM, SAED, XRD, TGA, DLS and Zeta potential measurements. The results indicated that microwave assisted synthesis produced well dispersed, small sized, uniform nanoparticles when compared to conventional room temperature synthesis. The spherical nanoparticle had an average size of 12.0 ± 3.2 nm as revealed through TEM. The crystalline nature of AuNP was confirmed through HR-TEM, SAED and XRD. The FT-IR and TGA data revealed the presence of the CQE components on the surface of the AuNP particles which serve as the capping agent. Upon incubation, the particles did not lyse the red blood corpuscles (RBCs) indicating that they are biocompatible. A possible mechanism for the formation of AuNP in the presence of CQE is proposed. © 2013 Elsevier B.V. All rights reserved.

Bhange D.S.,CSIR - National Chemical Laboratory | Ramaswamy V.,Central Research Institute for Physics
Microporous and Mesoporous Materials | Year: 2010

In the present investigations we have carried out the high temperature X-ray diffraction (HTXRD) studies on the metallosilicate molecular sieves iron silicalite-1 (FeS-1) samples of different Si/M ratios (Si/Fe = 50, 75, 100 and ∞) for their negative thermal expansion (NTE) behavior. All the samples exhibit NTE behavior in the temperature range 373-773 K. Systematic increase in negative thermal expansion coefficient is observed as a function of increasing Fe content in the MFI framework. Strength of the negative thermal expansion increases in the order Si/Fe = ∞ < 100 < 75 < 50. It is concluded that by changing the composition of the framework of MFI, enhanced negative thermal expansion can be obtained. © 2009 Elsevier Inc. All rights reserved.

Schiller R.,Central Research Institute for Physics | Horvath A.,Central Research Institute for Physics
Journal of Chemical Physics | Year: 2011

The photochemical yield of hydrated electrons as a function of temperature in liquid and supercritical water is treated in terms of energy fluctuations of the medium. The geminate pair, consisting of a positive ion and a hydrated electron, is regarded as a H-like atom embedded in a completely relaxed dielectric continuum. If the local medium energy is larger than the ionization energy of this atom, the electron escapes its geminate partner. By making use of the classical theory of energy fluctuations, escape probability is described by a simple explicit function, the variable of which is a combination of temperature, relative permittivity, and specific heat. First our earlier calculations on the recombination of solvated electrons, produced by ionizing radiation in a number of polar liquids, are improved and then the theory is compared with the experimental results on temperature dependent electron survival by Kratz [S. Kratz, J. Torres-Alcan, J. Urbanek, J. Lindner, and P. Vhringer, Phys. Chem. Chem. Phys. 12, 12169 (2010)]10.1039/c0cp00762e. Two adjustable parameters are needed to achieve reasonable quantitative agreement. © 2011 American Institute of Physics.

Karthikeyan S.,CSIR - Central Leather Research Institute | Anandan C.,National Aerospace Laboratories, Bangalore | Subramanian J.,Central Research Institute for Physics | Sekaran G.,CSIR - Central Leather Research Institute
RSC Advances | Year: 2013

The persistent organic pollutants and bio diversities (pathogenic and non-pathogenic) present in treated municipal wastewater cause environmental deterioration besides adversely affecting human health. In the present investigation, an attempt was made to treat the municipal wastewater using iron impregnated polyacrylamide (IIPA) powder catalyst in a fluidized reactor. The IIPA catalyst was characterized by carbon, 12.23%, hydrogen, 1.63%, nitrogen, 2.93%, iron, 58%, silicon, 15.25%, surface area 96.66 m2 g -1 and pore diameter, 58.32 Å. IIPA was crystalline with an energy gap of 1.93 eV and it was capable of generating hydroxyl radicals for the oxidation of dissolved organics in municipal wastewater with minimum sludge yield (0.05 g VSS/g of COD). The oxidation of dissolved organics in municipal wastewater by IIPA was carried out under batch and continuous mode operations. The pseudo first order rate kinetic constants for the oxidation of organics in municipal wastewater were found to be 2.2 × 10-2, 3.01 × 10-2, 3.33 × 10-2 and 3.72 × 10-2 min-1. The activation energy for the oxidation of dissolved organics in municipal wastewater was 13.15 kJ mol-1. The pollution parameters BOD5, COD, ammonia, TKN and sulphide were removed from the municipal wastewater by 72.72%, 82.87%, 71.76%, 65.3% and 86.66% respectively. © The Royal Society of Chemistry 2013.

Sindhu K.,CSIR - Central Leather Research Institute | Rajaram A.,Central Research Institute for Physics | Sreeram K.J.,CSIR - Central Leather Research Institute | Rajaram R.,CSIR - Central Leather Research Institute
RSC Advances | Year: 2014

Gold nanoparticles have gained much attention due to their widespread biological and technological applications, and consequently their simpler synthesis via green chemistry has also become of foremost importance. We report the room temperature synthesis of spherical gold nanoparticles using curcumin alone as the reducing and stabilizing agent. The pH is found to have an important role in curcumin solubilisation and subsequent formation of curcumin conjugated gold nanoparticles (cAuNPs). UV-visible studies show that the cAuNPs formed are of uniform size and HRTEM studies confirm spheres of average size 18 nm. The DLS measurements show a particle size of 58 nm. The crystallinity has been determined by HRTEM and XRD. The conjugation of stable curcumin on the cAuNPs is indicated by FTIR spectra which also suggest that the phenolic and enolic groups of curcumin bring about the reduction. The zeta potential value of cAuNPs is -23 mV which is stable for up to 6 months at room temperature. The mechanism of cAuNP formation is inferred to be through temporal evolution. This is the first demonstration where curcumin is solubilized at alkaline pH without using any external agent and is used for reducing HAuCl4 to form cAuNPs. The non toxic nature of the cAuNPs is evidenced through biocompatibility studies using human blood cells. © 2014 The Royal Society of Chemistry.

Bernido C.C.,Central Research Institute for Physics | Carpio-Bernido M.V.,Central Research Institute for Physics
International Journal of Modern Physics B | Year: 2012

The white noise calculus originated by T. Hida is presented as a powerful tool in investigating physical and social systems. Combined with Feynman's sum-over-all histories approach, we parameterize paths with memory of the past, and evaluate the corresponding probability density function. We discuss applications of this approach to problems in complex systems and biophysics. Examples in quantum mechanics with boundaries are also given where Markovian paths are considered. © 2012 World Scientific Publishing Company.

Schiller R.,Central Research Institute for Physics | Horvath A.,Central Research Institute for Physics
Radiation Physics and Chemistry | Year: 2012

Our theory, outlined earlier [Schiller, R., 1990. Ion-electron pairs in condensed polar media treated as H-like atoms. J. Chem. Phys. 92, 5527-5532.], is based on the idea that the electron and its geminate positive ion form a hydrogen-like atom, which can be ionized at the expense of the energy fluctuations in the medium. Temperature, T, static relative permittivity, ε s, and constant-volume molar specific heat, Cvm, play here the decisive role; the combination Tεs2Cvm, is the variable by which the yield can be predicted. The calculations agree with the recent experimental results on the temperature dependent yields of hydrated electrons by Kratz et al. [Kratz, S., Torres-Alcan, J., Urbanek, J., Lindner, J., Vöhringer, P., 2010. Geminate recombination of hydrated electrons in liquid-to-supercritical water studied by ultrafast time-resolved spectroscopy. Phys. Chem. Chem. Phys. 12, 12169-12176.] reasonably well. © 2011 Elsevier Ltd.

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