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11.
Chakrapani V Pendyala C Kash K Anderson AB Sunkara MK Angus JC 《Journal of the American Chemical Society》2008,130(39):12944-12952
Charge transfer between diamond and an electrochemical redox couple in an adsorbed water film has recently been shown to pin the Fermi level in hydrogen-terminated diamond. Here we show that this effect is a more general phenomenon and influences the properties of other semiconductors when the band lineup between the ambient and electronic states in the semiconductor is appropriate. We find that the luminescent intensities from GaN and ZnO change in different, but predictable, ways when exposed to HCl and NH3 vapors in humid air. The effect is reversible and has been observed on single crystals, nanowires, flakes, and powders. These observations are explained by electron exchange between the oxygen electrochemical redox couple in an adsorbed water film and electronic states in the semiconductor. This effect can take place in parallel with other processes such as defect formation, chemisorption, and surface reconstruction and may play an important, but previously unrecognized, role when electronic and optical measurements are made in air. 相似文献
12.
Jayakrishna Khatei Naresh Babu Pendyala K.S.R. Koteswara Rao 《Journal of luminescence》2010,130(12):2512-2515
The photoluminescence (PL) properties of nano- and micro-crystalline Hg1?xCdxTe (x≈0.8) grown by the solvothermal method have been studied over the temperature range 10–300 K. The emission spectra of the samples excited with 514.5 nm Ar+ laser consist of five prominent bands around 0.56, 0.60, 0.69, 0.78 and 0.92 eV. The entire PL band in this NIR region is attributed to the luminescence from defect centers. The features like temperature independent peak energy and quite sensitive PL intensity, which has a maximum around 50 K is illustrated by the configuration coordinate model. After 50 K, the luminescence shows a thermal quenching behavior that is usually exhibited by amorphous semiconductors, indicating that the defects are related to the compositional disorder. 相似文献
13.
Muralidhar P Krishna N Kumar MM Rao CB Rao DV 《Chemical & pharmaceutical bulletin》2003,51(10):1193-1195
Chemical examination of the marine sponge Iotrochota baculifera of the Indian Ocean furnished a sphingolipid (1), a new glycosphingolipid (iotroridoside-B, 2) and a four-component mixture of sphingolipids (3a-d) with two new components. Structure elucidation was carried out by spectral and chemical methods. 相似文献
14.
Naresh Babu Pendyala 《Journal of luminescence》2008,128(11):1826-1830
We report the type and nature of the surface states in PbS quantum dots grown in poly vinyl alcohol by the colloidal technique. Mercaptoethanol (C2H5OSH) capping and the molar ratio of Pb:S were used as parameters to understand the origin of the surface state related photoluminescence. From absorption and photoluminescence measurements, it was observed that increasing Lead concentration resulted in bigger nanoparticles with broad size distribution. However, the increase in sulfur concentration helped in the formation of smaller nanoparticles with narrow size distribution. Passivation studies also revealed that the origin of the bands below 1.1 eV was sulfur related. Thus these experiments indicated that sulfur played an important role, not only in size selectivity, but also in controlling defects in PbS quantum structures. Temperature dependent PL studies on different samples with various Pb:S molar ratios and with mercaptoethanol treated gave an insight into the nature of the surface states. Based on these results, we explain the origin of the surface states and proposed a model for different PL bands. The observed temperature-dependent trends of PL intensity (decreasing in Pb:S::1:1, increasing in S terminated and anomalous behavior in samples with excess of Pb) is attributed to the dominant mid-gap states and the results are consistent with carrier redistribution and recombination statistics involved in the quantum structures. 相似文献
15.
Mihir K. Chaudhuri Pradip C. Paul Pendyala Srinivas 《Journal of Chemical Sciences》1994,104(4):479-481
A new and direct route tobis(acetylacetonato)dioxouranium(VI) dihydrate, UO2(C5H7O2)2·2H2O, based upon the reaction of UO3·4H2O with acetylacetone (C5H8O2), is described. 相似文献
16.
Song L Prey JD Xue J Kanter P Manzotti C Bombardelli E Morazzoni P Pendyala L 《Rapid communications in mass spectrometry : RCM》2005,19(24):3617-3625
In this report, electrospray ionization tandem mass spectrometry (ESI-MS/MS) for a pharmacokinetic study of IDN 5390, a novel C-seco taxane derivative, which is under preclinical evaluation, has been investigated. Our results showed that IDN 5390 and other taxanes including paclitaxel and IDN 5109 could ionize well in not only positive-, but also in negative-ion mode. Under collision-induced dissociation (CID) conditions, these compounds could fragment into similar M- (molecular), T- (taxane ring) and S- (side chain) series ions. In positive-ion ESI, the formation of both T- and S-series ions involved the breaking of the C-13 ester bond. In negative-ion ESI, however, while the formation mechanism of S-series ions remained the same, the breaking of the C-1' carboxylic ester bond resulted in T-series ions. At optimum collision energy (CE) values, M-, T- and S-series ions of IDN 5390 in both positive- and negative-ion ESI-MS/MS spectra had good intensity. This phenomenon makes both positive- and negative-ion ESI-MS/MS good methods for IDN 5390 metabolite structural characterization, i.e. to reveal the location of modification groups in IDN 5390 metabolites versus IDN 5390 either on the side chain or the taxane ring. A liquid chromatography (LC)/ESI-MS/MS method using the multiple-reaction monitoring (MRM) technique was thereafter developed to quantify IDN 5390 in dog plasma using paclitaxel as internal standard. The method was validated using a concentration range between 5 and 1000 ng/mL and had a limit of detection of 1 ng/mL. The inter-day %CV (%coefficient of variation) of the calibration standards ranged between 4.36 and 9.64%, the intra-day %CV of the calibration standards between 0.61 and 13.44%, and the mean % accuracy of the quality control samples at the low, middle and high end of the concentration curves were 12.5, 6.8 and 9.6%, respectively. 相似文献
17.
Ravi Kumar Vuradi Navaneetha Nambigari Pushpanjali Pendyala Srinivas Gopu Laxma Reddy Kotha Deepika G Vinoda Rani M Satyanarayana Sirasani 《应用有机金属化学》2020,34(3):e5332
A set of novel mononuclear polypyridyl complexes of Ru (II) with N – N donar ligands 1, 10 phenanthroline (phen), 2, 2′ bipyridine (bpy), 4, 4′-dimethyl 2, 2′ bipyridine (dmb) and an intercalating ligand (bnpip = 2-(4-butoxy-3-nitrophenyl)-1H-imidazo [4,5-f] [1,10] phenanthroline) have been synthesized and characterized by various spectral methods. The RT - PCR assays suggest that ruthenium (II) complexes inhibit MCF-7, breast cancer cell line by inducing apoptosis via inhibition of cell cycle check points cyclin D, cyclin E and also upregulation of caspase 8 (protein involved in late Apoptosis). Further the binding potency of Ru (II) complexes were investigated using various spectroscopic techniques like UV–visible, fluorescence and viscosity studies. The complex binds to DNA in an intercalative mode as confirmed by viscosity data with differential binding strength. All complexes show cleavage of the pBR322 DNA through a singlet oxygen production. Theoretical evidence via docking of the complex with DNA reveals the significant residues of binding as guanine. 相似文献
18.
Stereoselective Total Synthesis of Iso‐Cladospolide B and the 12 Membered‐Macrolactone (6S,12R)‐6‐Hydroxy‐12‐methyloxacyclododecane‐2,5‐dione
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Pendyala Venkata Arun Kumar Venkata Satyanarayana Mallula Palakodety Radha Krishna 《Helvetica chimica acta》2015,98(8):1115-1126
Total syntheses of iso‐cladospolide B ( 1 ) and the 12‐membered macrolactone (6S,12R)‐6‐hydroxy‐12‐methyloxacyclododecane‐2,5‐dione ( 2 ), a non‐natural product, were achieved from a common intermediate starting from commercially available 1,9‐nonane diol. 相似文献