Green synthesis of silver nanoparticle by <Emphasis Type="Italic">Penicillium purpurogenum</Emphasis> NPMF: the process and optimization

An eco-friendly microbial method for synthesis of silver colloid solution with antimicrobial activity is developed using a fungal strain of Penicillium purpurogenum NPMF. It is observed that increase in concentration of AgNO₃ increases the formation of silver nanoparticle. At 5 mM concentration highly populated polydispersed nanoparticles form. Furthermore, change in pH of the reaction mixture leads to change in shape and size of silver nanoparticles. At lower pH two peaks are observed in the absorption spectra showing polydispersity of nanoparticles. However, highly monodispersed spherical nanoparticles of 8–10 nm size form with 1 mM AgNO₃ concentration at pH 8. Antimicrobial activity of nanoparticles is demonstrated against pathogenic gram negative bacteria like Escherichia coli and Pseudomonas aeruginosa, and gram positive bacteria like Staphylococcus aureus. The antimicrobial activity of silver nanoparticles obtained at different initial pH show strong dependence on the surface area and shape of the nanoparticles.     

Radio frequency plasma enhanced chemical vapor based ZnO thin film deposition on glass substrate: A novel approach towards antibacterial agent

In the present study, the structural, optical and antibacterial properties of ZnO thin films are reported. ZnO thin films are deposited on borosilicate glass substrates by radio frequency plasma enhanced chemical vapor deposition (PECVD) using oxygen as process gas. The crystallinity of the deposited films is improved upon annealing at 450 °C in air for 1.5 h and the polycrystalline nature of the films is further confirmed by selected area electron diffraction. The particle size of the annealed film (thickness 476 nm) is found to be ∼34 nm from the transmission electron microscopic observation. Energy dispersive X-ray spectrum indicates the stoichiometric deposition of ZnO films. The films are highly transparent (transmittance >85%) in the visible region of electromagnetic spectrum. The films exhibit excellent antibacterial effect towards the growth of Escherichia coli and Pseudomonas aeruginosa.     

Importance of steric effect and evaluation of quantitative structure reactivity relationship (QSRR) in the quaternization reaction of benzothiazoles and phenacyl bromide

The kinetics of reaction of substituted 2-aminobenzothiazoles and phenacyl bromide have been followed conductometrically and in some cases, argentometrically. Both the methods produced almost the same rate constants. Substituents at position 5 of the benzothiazole nucleus behave like para substituents of the benzene ring. A correlation with Hammett σ_p substituent constants has been obtained with a rho value of ?1.04. The rate data of quaternization reaction of 4, 5, and 6 substituted 2-aminobenzothiazoles with phenacyl bromide have been correlated with F_k, R_k, and V_w values by multiple regression analysis with the equation suggested by Williams and Norrington and modified by us. The values are found to correlate well with the equation, log k = ?4.4979 ? 0.4815f_jF_k + 0.5933r_jR_k ? 0.0277V_w.     

Raman scattering in organic superconductor (BEDT-TTF)2 I 3: A model study

An interpretation of the Raman data of the organic superconductor (BEDT-TTF)₂ I ₃ is given, based on the modified charge bag model for superconductivity. The Raman intensities are calculated at zero temperature both in the normal as well as the superconducting (SC) states. The scattering due to charge carriers as well as the phonons are taken into account. The results show a constant intensity background which reduces on going from the normal to the superconducting state. Similarly, the loss of intensity, broadening and softening of the frequency of a low lying phonon on going from the normal to the SC state are predicted. All these features are in qualitative agreement with the observed Raman data.     

Reversal in solvatochromism in some novel styrylpyridinium dyes having a hydrophobic cleft

The influence of solvent polarity on the electronic transition of four different N-hexadecyl styrylpyridinium dyes has been investigated in 15 solvents. The E(T)(30) scale has been used to propose a quantitative approach towards the relative stability of the electronic ground and excited state species. The extents of contribution of dipolar aprotic solvents towards the solvation of the excited species have been determined to be 42-48% for some of the dyes. Instead of a steady solvatochromism, all the dyes suffer a reversal in solvatochromism. The transitions of the solvatochromism, referred to as solvatochromic switches, are found to be at E(T)(30) values of approximately 50 for methyl and N,N-dimethylamino substituted dyes while at 37.6 for hydroxyl substituted dye and approximately 45 for 4-(1-methyl-2-phenylethenyl) pyridinium dye. A reversal in the trend of solvent effect in the later dye corresponding to 4-(4-methyl styryl)pyridinium dye has been attributed to an analogy of series and parallel electron flow.     

Dielectric and electrical properties of a tungsten bronze tantalate ceramic

Using high temperature solid state reaction the polycrystalline sample of K₂Pb₂Dy₂W₂Ti₄Ta₄O₃₀ was prepared. Single-phase compound formation was confirmed by preliminary X-ray structural analysis. The surface morphology recorded by scanning electron microscope at room temperature exhibits a dense uniform grain distribution on the surface of the sample. Ferroelectricity in the material is confirmed by the variation of polarization with temperature. The temperature and frequency dependence of electrical parameters (impedance, modulus, conductivity, etc.) of the material exhibits a strong correlation with its microstructure (i.e., bulk, grain boundary, etc.) and electrical properties. A typical Arrhenius behavior was observed in the temperature dependence of dc conductivity. The nature of frequency dependence of ac conductivity obeys Jonscher's universal power law. The variation of current with temperature shows that the material has high pyroelectric coefficient and figure of merit, thus making it useful for pyroelectric sensors with working temperature upto 500 °C.     

Synthesis,radiolabelling and biodistribution of HYNIC-Tyr<Superscript>3</Superscript> octreotide: a somatostatin receptor positive tumour imaging agent

In vivo imaging of tumours using radiolabelled somatostatin (SST) analogues has become an accepted clinical tool in oncology. HYNIC-Tyr³ octreotide and Tyr³ octreotide were synthesized by FMOC solid-phase peptide synthesis using a semi-automated synthesizer. These were analyzed and purified by RP-HPLC, mass spectroscopy, IR spectroscopy, ¹H NMR and ¹³C NMR. The prochelator 6-BOC-HYNIC was also synthesised and characterised indigenously. HYNIC-Tyr³ octreotide was labelled with ^99mTc using Tricine and EDDA as coligand by SnCl₂ method. Labelling with ^99mTc was performed at 100 °C for 15 min and radiochemical analysis by ITLC and HPLC methods. The radiochemical purity of the complex was over 98% and log p value was found to be −1.27 ± 0.12. The stability of radiolabelled peptide complex was checked at 37 °C up to 24 h. Blood clearance and protein-binding study was also performed. In vivo biodistribution studies in rat showed uptake of ^99mTc-HYNIC-TOC in kidney than any other organs. The blood clearance was faster with rapid excretion through kidneys and relatively low uptake in liver.     

Solubilization and stabilization of fullerene C60 in presence of poly(vinyl pyrrolidone) molecules in water

Solubilizing C₆₀ molecules in an aqueous medium is highly imperative in processing them in different forms of ionic or nonionic liquids, nanofluids, films and other derivatives. In this investigation, we report a facile chemical route using polymer molecules of poly(vinyl pyrrolidone) (PVP) which mediate C₆₀ molecules dissolving in water in a stable solution at room temperature. Poly(vinyl pyrrolidone) molecules, soluble in water as well as many organic liquids such as n-butanol, ethanol, or DMF, can be useful for transferring C₆₀ molecules from a non-aqueous to an aqueous system. A broad optical absorption arises over 270–520 nm when C₆₀ molecules are dissolved in water, 0.001–0.065 g/L in presence of 20–120 g/L PVP molecules. It consists of a strong π → π* absorption band (relatively sharp) lying at 294 nm in C(sp²) electrons from PVP-surface modified C₆₀ molecules followed by a broad charge transfer band which extends up to 520 nm. Upon a suitable surface modification, the C₆₀ molecules conquer enhanced optical absorption in both kinds of the bands. Dynamic light scattering reveals an average hydrodynamic length 181.5 nm and a polydispersity index 0.506 after a typical loading 0.065 g/L C₆₀. A zeta potential ?8.3 mV with a surface conductivity 0.064 mS/cm at 6.5 pH describes a negatively charged surface structure, showing an n-electron transfer from C=O (PVP) to a nanosurface in surface modified C₆₀ molecules in a weak donor–acceptor complex. Water soluble C₆₀ in presence of a biocompatible compound like PVP is useful for biological, medicinal, and other applications.