Formation of rectifier with gold nanoclusters

Gold nanoclusters encapsulated with organic molecules are of great interest for its possible applications in the fields of molecular electronics, catalysis and medical science. Here we demonstrate that monolayer and bilayer films of thiol-capped gold nanoclusters can exhibit diode-like properties provided controlled spatial asymmetry exist between two tunnel junctions used to connect a thiol capped gold nanoclusters. Current-voltage characteristics of this rectifier were obtained from conducting probe atomic force microscopy measurements and also from conventional two probe resistance measurements. Systematic x-ray reflectivity and atomic force microscopy measurements were carried out to characterize the spatial asymmetry introduced by a monolayer of fatty acid salt gadolinium stearate used to deposit thiol-capped gold nanocluster molecules on hydrophilic SiO2-Si(001) substrate by Langmuir Blodgett technique. This information was used to explain prominent rectification observed in these nano-structured films.Comment: 13 pages, 3 figure

Optimizing growth conditions for electroless deposition of Au films on Si(111) substrates

Electroless deposition of Au films on Si(111) substrates from fluorinated-aurate plating solutions has been carried out at varying concentrations, deposition durations as well as bath temperatures, and the resulting films were characterized by X-ray diffraction, optical profilometry, atomic force microscopy and scanning electron microscopy. Depositions carried out with dilute plating solutions (<0.1 mM) at 28°C for 30 min produce epitaxial films exhibiting a prominent Au(111) peak in the diffraction patterns, while higher concentrations or temperatures, or longer durations yield polycrystalline films. In both epitaxial and polycrystalline growth regimes, the film thickness increases linearly with time, however, in the latter case, at a rate an order of magnitude higher. Interestingly, the surface roughness measured using atomic force microscopy shows a similar trend. On subjecting to annealing at 250°C, the roughness of the film decreases gradually. Addition of poly (vinylpyrrolidone) to the plating solution is shown to produce a X-ray amorphous film with nanoparticulates capped with the polymer as evidenced by the core-level photoelectron spectrum. Nanoindentation using AFM has shown the hardness of the films to be much higher (∼2.19 GPa) than the bulk value

Giant single crystalline Au microplates

Single crystalline Au(111) surface is the most sought after platform for studying molecular and other inter-esting phenomena. Here we report the synthesis of giant Au(111) single crystalline microplates along with their prototype applications. The single-crystal surfaces are atomically flat and possess areas extending over ∼100,000 μm2. The synthesis method is simple involv-ing a one-step thermolysis process, i.e. heating on a hot plate, of a alkylammonium salt, making the process flow easy and scalable for mass production. Other interesting anisotropic structures such as nanorods and microstars are also obtained by slightly varying the synthetic conditions

A single molecule switch based on two Pd nanocrystals linked by a conjugated dithiol

Tunneling spectroscopy measurements have been carried out on a single molecule device formed by two Pd nanocrystals (dia, $\sim$5 nm) electronically coupled by a conducting molecule, dimercaptodiphenylacetylene. The I-V data, obtained by positioning the tip over a nanocrystal electrode, exhibit negative differential resistance (NDR) on a background M-I-M characteristics. The NDR feature occurs at $\sim$0.67 V at 300 K and shifts to a higher bias of 1.93 V at 90 K. When the tip is held in the middle region of the device, a coulomb blockade region is observed ($\pm\sim$0.3 V).Comment: Accepted in Praman

Inhomogeneous vortex-state-driven enhancement of superconductivity in nanoengineered ferromagnet-superconductor heterostructures

Thin film heterostructures provide a powerful means to study the antagonism between superconductivity (SC) and ferromagnetism (FM). One interesting issue in FM-SC hybrids which defies the notion of antagonistic orders is the observation of magnetic field induced superconductivity (FIS). Here we show that in systems where the FM domains/islands produce spatial inhomogeneities of the SC order parameter, the FIS can derive significant contribution from different mobilities of the magnetic flux identified by two distinct critical states in the inhomogeneous superconductor. Our experiments on nanoengineered bilayers of ferromagnetic CoPt and superconducting NbN where CoPt/NbN islands are separated by a granular NbN, lend support to this alternative explanation of FIS in certain class of FM-SC hybrids.Comment: 5 figure

A fluctuation theory for Markov chains

A fluctuation theory for Markov chains on an ordered countable state space is developed, using ladder processes. These are shown to be Markov renewal processes. Results are given for the joint distribution of the extremum (maximum or minimum) and the first time the extremum is achieved. Also a new classification of the states of a Markov chain is suggested. Two examples are given

Cu K-absorption edge study of cuprate superconductors

Cu K-absorption edges of YBa2Cu3O6.9, Tl2CaBa2Cu2O8 and Bi2CaSr2Cu2O8 show similar features. Copper is mainly in the 2+ state in these cuprates suggesting the likely presence of oxygen holes

A clinical study of mode of delivery and perinatal outcome in iligohydramnios

Background: To evaluate intrapartum sequale of sonographically diagnosed Oligohydrominos such as rate of caesarean section, fetal distress and condition of the new born.Methods: This Prospective observational study was conducted in the department of obstetrics and Gynecology, Navodaya Medical College Hospital and Research Centre between June 2015 to December 2016. The antenatal women with gestational age more than 34 weeks and above, attending our OPD or labor room were included in this study.Results: A total of 140 cases of Oligohydromnias were selected for present study and outcome were assessed. The mean maternal age is 24.42 years. 32.14% cases have delivered vaginally, 67.82% patients went for caesarean sections, 10.7% of babies needed NICU care and 1 was still birth. No adverse maternal complications were observed during the study.Conclusions: Oligohydromnia is one of the frequent complications during labor. The risk of muconium staining of liquor, intrapartum fetal distress, operative delivery and NICU admissions are more in Oligohydromnia cases

Genetic Analysis in Muskmelon (Cucumis melo L.)

Fifty genotypes of muskmelon (Cucumis melo L.) were evaluated for variability, correlation, path analysis and divergence for yield and its contributing characters. Analysis of variance showed significant variation for all the characters, indicating presence of sufficient variability in the material studied. Genotypic correlations were higher than those of their respective phenotypic correlation coefficients in majority of the cases suggesting, that, genotypic correlations were stronger, reliable and free from environmental influences. Path analysis based on genotypic association revealed that number of fruits per plant and moisture percentage was the main yieldattributing characters in fruit yield of muskmelon. Total soluble solids exhibited positive direct effect on fruit yield per plant. Thus, number of fruits per plant, moisture percentage and total soluble solids may be given more weightage for an effective selection to improve fruit yield in muskmelon. On the basis of relative magnitude of D2 values, all the genotypes were grouped in seven clusters. Maximum genetic distance was observed between clusters II and V, while clusters III and VII displayed the lowest degree of divergence. Total soluble sugars followed by total soluble solids and fruit yield per plant contributed the most towards divergence