Enhanced antibacterial activity of tetramethylguanidinium-conjugated linear polyethylenimine polymers

In the present study, varying amounts of tetramethylguanidinium moiety have been conjugated to linear polyethylenimine to obtain linear polyethylenimine-tmg (LPTG) polymers. Incorporation of hydrophobic and highly basic moiety in the polymeric backbone resulted in the significant improvement in the antibacterial activity which was confirmed by zone of inhibition and MIC assays. Further, the results of transmission electron microscopy and confocal studies revealed that the projected LPTG polymers possessed higher antibacterial activity than the native polymer. In addition, these modified polyethylenimine (PEI) polymers were capable of reducing auric chloride into stable gold nanoparticles. These polyamine-stabilized gold nanoparticles can be used in various biomedical applications.     

Thermodynamic and Surface Properties of Aqueous 1-Dodecyl-3-Methylimidazolium Chloride [C12mim][Cl] Solution in the Presence of a Series of Inorganic Salts

The micellization behavior of amphiphiles is a well-analyzed physicochemical phenomenon, which can be easily influenced by various parameters such as pressure, temperature, and the presence of different additives. Inorganic salts are able to affect the thermodynamic and surface properties of amphiphiles significantly. The effect of a series of salts as additives namely lithium chloride (LiCl), potassium chloride (KCl), sodium chloride (NaCl), sodium bromide (NaBr), and sodium iodide (NaI) on interfacial chemical characteristics of the surface-active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium chloride [C₁₂mim][Cl] in aqueous solution were examined through conductance, surface tension, fluorescence, ¹H NMR, and dynamic light scattering measurements. The interfacial and thermodynamic parameters of all investigated SAIL-salt systems were evaluated from surface tension and conductance measurements, respectively. A detailed analysis of the microenvironment of the micelles and the size of the micelles was done using ¹H NMR and dynamic light scattering measurements.     

Investigation of structural,optical, and magnetic properties of Nd-doped Sr2SnO4 Ruddlesden Popper oxide

The samples of Sr_2-xNd_xSnO₄ with x = 0, 0.01, 0.02, 0.04, 0.06, and 0.10 were synthesized by a high-temperature solid-state ceramic route. Rietveld refining of X-ray diffraction results showed that all the synthesized compositions are single phase under tetragonal crystal structure. The presence of functional group and local structure has been studied using FTIR and Raman spectroscopy, respectively. XPS study of samples showed the presence of oxygen vacancy and interstitial oxygen in the sample. Optical band gap of samples analyzed by UV-Vis spectra gradually increases with dopant concentration, and Photoluminescence (PL) spectroscopy study showed most intense emission around 1064 nm. Room-temperature magnetic hysteresis curve in sample SSN2 showed ferromagnetism, slowly decreasing with Nd and becoming antiferromagnetic for higher compositions. Utilizing the absorption state observed in PL as metastable state makes it promising candidate for laser and IR detector application and the ferromagnetic/antiferromagnetic nature of sample makes it suitable candidate for spintronics device applications.     

Combustion synthesis of compounds in the Y2O3-Al2O3 system

In the Y₂O₃-Al₂O₃ system, compounds Y₃Al₅O₁₂ (yttrium aluminum garnet, YAG), YAlO₃ (yttrium aluminum perovskite, YAP), and Y₄Al₂O₉ (yttrium aluminate monoclinic, YAM) are well known. YAG and YAP are of considerable technological importance. Conventional solid-state reaction techniques require high sintering temperatures (above 1800°C) to prepare phase-pure compounds. Though several soft chemical routes have been explored for synthesis of YAG, YAP and YAM, most of these methods are complex. Moreover, phase-pure materials are not obtained in one step and prolonged annealing at temperatures around 1000°C is necessary. In this paper, one-step combustion synthesis of these compounds is reported using a modified procedure and employing mixed (glycine + urea) fuel. Phosphors based on Ce³⁺ activation were also prepared and exhibited characteristic photoluminescence.     

Effect of bacterial inoculum ratio in mixed culture for decolourization and detoxification of pulp paper mill effluent

BACKGROUND: Effluent released from industry is a mixture of various pollutants. For the degradation of complex pollutants, mixed bacterial cultures can be more effective than a single culture. This study investigated the balance of bacterial populations in a mixed culture for maximum reduction of pollutants. RESULTS: This study deals with the degradation and detoxification of pulp paper mill effluent (PPME) by three bacterial strains, i.e. Serratia marcescens, Serratia liquefaciens and Bacillus cereus in different ratios, and found that two ratios, 4:1:1 and 1:4:1, were effective for the degradation of PPME. These ratios reduced the various pollution parameters. Enzyme bioassay revealed that more enzyme was produced during degradation for the ratio 4:1:1. High performance liquid chromatography (HPLC) analysis showed that the ratio 4:1:1 degraded 95% of lignin and related compounds, and chlorophenols up to 98%, whereas ratio 1:4:1 reduced lignin by 84% and chlorophenols by 58% after 7 days incubation. Degradation products were confirmed by gas chromatography–mass spectrometry (GC‐MS) analysis. A seed germination bioassay on Phaseolous mungo L. revealed that toxicity was reduced by the ratio 4:1:1. CONCLUSION: Due to variable potential of different bacteria show variation in their growth pattern at any contaminated site. This study shows that an appropriate ratio of mixed cultures is required for maximum degradation and detoxification of PPME. Copyright © 2012 Society of Chemical Industry     

Synthesis of nanocrystalline cerium oxide by high energy ball milling

We have synthesized pure nanocrystalline CeO₂ powders of nearly spherical shape using high-energy attritor ball mill. Milling parameters such as the milling speed of 400 rpm, ball to powder ratio (40:1), milling time (30 h) and water cooled media were determined to be suitable for synthesizing nanosize (～10 nm) powders of CeO₂. The powders after milling for various durations (up-to 50 h) were characterized by X-ray Diffraction, Scanning Electron Microscopy, Energy-dispersive X-ray Spectrometry and Transmission Electron Microscopy. An average particle size of 10 nm was obtained at 30 h milling, after which the particle agglomeration started, and a mixture of nanocrystalline and amorphous phase was observed after 50 h milling.     

Experimental Investigation for Performance Study of Wire Electrochemical Spark Cutting of Silica Epoxy Nanocomposites

Purpose

Polymer Nanocomposites are advanced engineering composites with enhanced properties. These materials play a central role in various industrial sectors. The growing awareness of the key parameters (which influence the physical properties) with different combination of matrix-reinforcement, are making them more attractive in various applications. Machining of these materials is a challenging task for engineers with their properties (hardness and brittleness) due to various combinations of matrix-reinforcement. Therefore, the aim of present work is to investigate the machining behaviour of Silicon Dioxide (silica) Epoxy Nanocomposite due to straight cutting by using Wire Electrochemical Spark Cutting (WECSC) process.

Method

A specific number of experiments were conducted based on one parameter at-a-time approach to study the effect of influencing input parameters.

Result

The effect of various process parameters namely voltage supply, electrolyte concentration, wire velocity, pulse-on time and silica particle concentration (Cp) such as 3%, 4% and 5% (weight percent) on performance measures such as material removal rate (MRR) and surface roughness were demonstrated experimentally.

Conclusion

WECSC has been found effective technique for cutting of Silicon Dioxide Epoxy Nanocomposite. It is reported that MRR increases with decrease in silica particle concentration in Silicon Dioxide Epoxy Nanocomposite.

     

Tuning of Cloud Point by the Nature of Surfactant Headgroup: Influence of Counterion and Additives

Work was performed to distinguish the role of sulfonate (–SO₃ ^?) and sulfate (–OSO₃ ^?) with respect to the micellization and clouding phenomenon in ionic surfactant solutions. The clouding phenomenon is a recent addition to the conventional one observed with nonionic surfactants. Three ionic surfactants [sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and sodium dodecylsulfonate (SDSo)] are chosen and the effects of added tetra-n-pentylammonium bromide (TPeAB) and benzyl tributylammonium bromide (BTAC) have been studied on micellization and clouding behaviors in aqueous solution. Based on critical micelle concentration (CMC) and cloud point (CP) measurements, the following order has been observed: SDBS < SDS < SDSo. Though both SDBS and SDSo contain sulfonate groups, they are found at the two ends of the ordering. Therefore, the role of the phenyl ring is also having importance in clouding phenomena. For a typical surfactant, TPeAB was found to be more effective than BTAC. Based on the CP studies, two compositions of SDSo + TPeAB/BTAC were chosen and the effects of different additives (carbohydrate, amino acid, and l-ascorbic acid) on the CP were investigated. Additive may either decrease or increase CP, depending on the structure of the counterion or additive. The present work shows a few novelties: (1) headgroup/counterion dependence of CP and (2) hydrophobicity of counterion/surfactant has an important bearing on the phenomenon. The data can be utilised in improving cloud point extraction methodologies (CPEMs).     

Study of crystal structure,dielectric, magnetic and magnetoelecrtic properties of xCoFe2O4-(1-x)Na0.5Bi0.5TiO3 composites

Multiferroic composites of spinel ferrite and ferroelectric xCoFe₂O₄ – (1-x)Na_0.5Bi_0.5TiO₃ (with x = 0.10,0.30,0.50) were efficiently prepared by standard solid state reaction mechanism. X-ray diffractometer was used to analyze crystal structure of the prepared composites. The observed XRD patterns of the composites comprise peaks of both the phases i.e. ferrite and ferroelectric, with no sign of secondary peaks. Rietveld refinement of XRD data further confirms the coexistence of these two phases with cubic (Fd3m) and rhombohedral (R3c) symmetry corresponding to ferrite and ferroelectric phase respectively. The 3-dimensional overview of crystal structure of pure CoFe₂O₄ and Na_0.5Bi_0.5TiO₃ and of composite 0.50CoFe₂O₄?0.50Na_0.5Bi_0.5TiO₃ is generated by using refined parameters. The dielectric constant (ε´) and dielectric loss (tanδ) values were recorded as a function of frequency ranging from 100?Hz to 7?MHz and at different temperatures. Both ε´ and tanδ follow dispersion pattern at lower frequencies while show frequency independent behavior at higher frequencies. The magnetic evaluation carried by analyzing M-H hysteresis loop reveals the ferrimagnetic characteristics of these composites. The highest value of magnetic moment is 1.12μ_B observed for composite 0.50CoFe₂O₄ – 0.50Na_0.5Bi_0.5TiO_3. Magnetoelectric (ME) voltage coefficient (α) was also demonstrated to observe the interaction between ferrite and ferroelectric phases. The highest value of α (72.72μV/Oe cm) is obtained for low ferrite composition 0.10CoFe₂O₄ – 0.90Na_0.5Bi_0.5TiO₃, which suggests the dependence of magnetoelectric response on the resistivity of the composites.