2,496 research outputs found
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
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 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, 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 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 (0.3 V).Comment: Accepted in Praman
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
Electrical characteristics of layered palladium alkanethiolates by conducting atomic force microscopy
Current-voltage measurements on individual Pd(II) alkanethiolate nanostructures of varying bilayer thicknesses (hexyl to hexadecyl) employing conducting atomic force microscopy have shown the presence of a low current region near zero bias, the width of which increases with the bilayer thickness. The resistance in this region varies exponentially with the bilayer thickness with a low decay parameter value of 0.2±0.04 Å-1 indicating a long-range nonresonant tunneling through the alkyl chains. The changeover from low current to high current with increasing bias is accompanied by a negative differential resistance feature, which arises due to Pd-S charge transfer
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