Weighted Cebysev-Ostrowski type inequalities

In account of the famous Cebysev inequality, a rich theory has appeared in the literature. We establish some new weighted Cebysev type integral inequalities. Our proofs are of independent interest and provide new estimates on these types of inequalities.     

Facile green synthesis of gold nanoparticles using leaf extract of antidiabetic potent Cassia auriculata

A simple biological method for the synthesis of gold nanoparticles (AuNPs) using Cassia auriculata aqueous leaf extract has been carried out in the present study. The reduction of auric chloride led to the formation of AuNPs within 10 min at room temperature (28°C), suggesting a higher reaction rate than chemical methods involved in the synthesis. The size, shape and elemental analysis were carried out using X-ray diffraction, TEM, SEM-EDAX, FT-IR and visible absorption spectroscopy. Stable, triangular and spherical crystalline AuNPs with well-defined dimensions of average size of 15-25 nm were synthesized using C. auriculata. Effect of pH was also studied to check the stability of AuNPs. The main aim of the investigation is to synthesize AuNPs using antidiabetic potent medicinal plant. The stabilizing and reducing molecules of nanoparticles may promote anti-hyperglycemic if tested further.     

Synthesis of functionalized arylpyridines and -pyrimidines by domino [4+2]/retro [4+2] cycloadditions of electron-rich dienes with alkynylpyridines and -pyrimidines

Aryl-substituted pyridines and pyrimidines were prepared by [4+2] cycloadditions of alkynyl-substituted pyridines and -pyrimidines with electron-rich dienes. The reactions proceed by formation of a bridged cycloadduct and subsequent thermal extrusion of ethylene. The pyridine moiety plays a crucial role for the success of the reaction.     

Role of added counterions in the micellar growth of bisquaternary ammonium halide surfactant (14-s-14): 1H NMR and viscometric studies

The change in the morphology of a series of dicationic gemini surfactants C(14)H(29)(CH(3))(2)N(+)-(CH(2))(s)-N(+)(CH(3))(2)C(14)H(29), 2Br(-) (14-s-14; s=4-6) on their interaction with inorganic (KBr, KNO(3), KSCN) and organic salts (NaBenz, NaSal) have been thoroughly investigated by means of (1)H NMR spectral analysis and the results are well supported by viscosity measurements. The presence of salt counterions results in structural transition (spherical to nonspherical) of gemini micelles in aqueous solution. With an increase in salt concentration all the three gemini surfactants showed changes in their aggregate morphology. This change is dependent on the nature and size of the added counterion. The effect of inorganic counterions on the micellar growth is observed to follow the Hofmeister series (Br(-) < NO(3)(-) < SCN(-)). The roles of organic counterions are discussed on the basis of probable solubilization sites of the substrate molecule in the gemini micelles, showing more growth in case of Sal(-) than Benz(-). The results are confirmed in terms of the obtained values of chemical shift (δ), line width at half height (lw), and relative viscosity (η(r)). Also, the growth of micelles was most pronounced for the gemini surfactant with the shortest spacer (s=4). This was attributed to the unique molecular structure of gemini surfactant micelles having flexible polymethylene spacer chain linking the twin polar headgroups.     

Interface control and photovoltaic properties of n-type silicon/metal junction by organic dye

The electronic parameters and photovoltaic properties of the Au/methylene blue/n-Si diodes were investigated by current-voltage and capacitance-conductance-frequency techniques. The diode exhibits a non-ideal behavior due the series resistance, organic layer and oxide layer. The barrier height (1.04 eV) of the Au/methylene blue/n-Si is higher than that of Au/n-Si Schottky diode (0.83 eV) due to an excess barrier formed by organic layer. The interface state density of the diode was determined using a conductance technique and was found to be 3.25 × 10¹² eV⁻¹ cm⁻². The diode shows a photovoltaic behavior with a maximum open circuit voltage V_oc of 0.23 V and short-circuit current I_sc of 20.8 μA under 100 mW/cm². It is evaluated that Au/methylene blue/n-Si is an organic-on-inorganic photodiode with the obtained electronic parameters and methylene blue organic dye controls the interface and electrical properties of conventional metal/n-type silicon junction.     

Controlling of electronic parameters of GaAs Schottky diode by poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol) organic interlayer

The electronic properties of metal-organic semiconductor-inorganic semiconductor structure between GaAs and poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol) organic film have been investigated via current-voltage and capacitance-voltage methods. The Au/PEDOT/n-GaAs contact exhibits a rectification behavior with the barrier height of 0.69 eV and ideality factor value of 3.94. The barrier height of the studied diode (0.67 eV) is lower than that of Ni/n-GaAs/In (0.85 eV) and Au/n-GaAs/In Schottky diodes. The decrease in barrier height of Au/n-GaAs/In Schottky diode is likely to be due to the variation in the space charge region in the GaAs. The obtained results indicate that control of the interfacial potential barrier for metal/n-GaAs diode was achieved using thin interlayer of the poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol).     

In situ Raman and UV-vis spectroscopic studies of polypyrrole and poly(pyrrole-2,6-dimethyl-β-cyclodextrin)

Polypyrrole (PPy) and poly(pyrrole-2,6-dimethyl-β-cyclodextrin) [P(Py-β-DMCD)] films prepared by potential cycling in aqueous acidic solutions on indium tin oxide (ITO)-coated glass and gold electrodes were studied by in situ UV-vis and Raman spectroscopy. Characteristic UV-vis and Raman bands were identified and their dependencies on the electrode potential have been discussed. Spectroelectrochemical results reveal differences both in the position of the spectral bands and their potential dependence for PPy and P(Py-β-DMCD) films indicating interactions between polymer chains and CDs during electropolymerization process. The films were also characterized by cyclic voltammetry and FT-IR spectroscopy.     

Study of cylindrically symmetric solutions in an $$f(R)$$ gravity background

Theoretical and Mathematical Physics - We investigate static cylindrically symmetric solutions of the Weyl and Gödel space–times in the framework of modified $$f(R)$$ gravity. With this...