Single Si nanowire (diameter ≤ 100 nm) based polarization sensitive near-infrared photodetector with ultra-high responsivity.

We report the fabrication and optical response of boron-doped single silicon nanowire-based metal-semiconductor-metal photodetector. Typical single nanowire devices with diameter of ∼80-100 nm and electrode spacing of ∼1 μm were made using electron-beam lithography from nanowires, grown by a metal-assisted chemical etching process. A high responsivity, of the order of 10(4) A W(-1), was observed even at zero bias in a single nanowire photodetector with peak responsivity in the near-infrared region.

Electric field driven destabilization of the insulating state in nominally pure LaMnO3.

We report an electric field driven destabilization of the insulating state in nominally pure LaMnO3 single crystal with a moderate field which leads to a resistive state transition below 300 K. The transition is between the insulating state in LaMnO3 and a high resistance bad metallic state that has a temperature independent resistivity. The transition occurs at a threshold field (Eth) that shows a steep enhancement on cooling.

Effective Mass-Driven Structural Transition in a Mn-Doped ZnS Nanoplatelet.

Mn doping in ZnS nanoplatelets has been shown to induce a structural transition from the wurtzite to the zinc blende phase. We trace the origin of this transition to quantum confinement effects, which shift the valence band maximum of the wurtzite and zinc blende polymorphs of ZnS at different rates as a function of the nanocrystal size, arising from different effective hole masses in the two structures. This modifies the covalency associated with Mn incorporation and is reflected in the size-dependent binding energy difference for the two structures.

Ab initio study of the phonon spectrum, entropy and lattice heat capacity of disordered Re-W alloys.

The Re(1-x)W(x) alloy is formed by continuous neutron bombardment of W, the core material making up the shield in fusion devices. Here, we present an ab initio study of the lattice dynamical properties of this commercially important alloy. The dynamical (force constant) matrix was obtained through a first-principles, density functional perturbation theory.

Anomalous dynamics of solutions of nonionic micelles in water.

In addition to a previous theory on the coupling between noncritical concentration fluctuations and elementary chemical processes, an alternative treatment is presented which allows for a closed-form solution of ultrasonic attenuation spectra. This analytical form is first compared to a previous model and also to experimental spectra of binary liquid mixtures. The broadening of the spectra is briefly discussed in terms of molecular interactions and of the ratio of the relaxation times of the chemical equilibrium and of the diffusion of fluctuations.

Growth of atomically smooth films of metal-arachidates by Langmuir-Blodgett technique.

In this paper, we report synthesis of atomically smooth Ni-arachidate films using Langmuir-Blodgett technique. The interaction between arachidic acid monolayer and nickel ion has been investigated as a function of subphase pH by measuring the compression isotherms at the air/water interface. As the pH is increased, the compressible liquid (L2) phase is observed over a smaller range of surface pressure (pi) and area/mol (A) until at high enough pH the L2 phase is altogether absent.

Transport properties of nanoparticles of complex oxides: likely presence of Coulomb blockade at low temperature.

In this paper we report transport properties at low temperatures (3 K < or = T < or = 300 K) in nanostructured functional oxides. Electrical resistivity in the nanoparticles of La0.5CoO3 (LSCO), a ferromagnet, show a gradual change-over from a completely metallic state (in the bulk sample) to a completely insulating state (in the sample with the smallest particle size of approximately 35 nm), while still remaining a ferromagnet, albeit with a lower Tc.

Investigation of very low-frequency noise in ferromagnetic nickel nanowires.

In this paper we report very low-frequency (0.1 mHz-1.0 Hz) resistance fluctuation (noise) in Nickel nanowires of diameter 20 nm in the temperature range 77 K-300 K.

Changes in thermodynamic properties of DNA base pairs in protein-DNA recognition.

The mechanism of protein-DNA recognition, particularly the induced fit mechanism, is poorly understood due to ineffective analysis of the protein-DNA complex crystal structures. It is expected that upon protein binding the DNA becomes structurally more rigid. However, a previous analysis (W.

Bulk viscosity universality and scaling function near the binary liquid consolute point.

The hydrodynamical equations and the notion of a frequency dependent complex specific heat near the critical point of binary liquids are used to obtain an expression for the low-frequency bulk viscosity. In this way the interrelations between different theoretical models, treating the critical sound attenuation from either a specific heat or a bulk viscosity approach, are made evident. The general structure of the bulk viscosity relation agrees with that of Onuki [Phys.

Role of solvation dynamics in the kinetics of solvolysis reactions in microreactors.

In this contribution we attempt to correlate the dynamical states of water molecules in reverse micelles with a solvolysis reaction in accordance with the activation energy barrier crossing model at the micellar interface. Precise measurement of the different dynamical states of water molecules at the reverse micellar interface with various degrees of hydration is achieved through temperature-dependent solvation dynamics of coumarin 523. The rotational anisotropy studies along with a wobbling-in-cone analysis show that the probe residing at the micellar interface pointing towards the core water experiences less microviscosity at elevated temperature.

A molecular picture of diffusion controlled reaction: role of microviscosity and hydration on hydrolysis of benzoyl chloride at a polymer hydration region.

In this study, we have attempted to explore the molecular mechanism associated with a diffusion controlled reaction at a polymer hydration region by monitoring temperature-dependent solvolysis reaction of benzoyl chloride (BzCl) in water-poly(ethylene glycol) mixture at low water concentration. BzCl being highly hydrophobic resides in the vicinity of the PEG surface and the reaction takes place at the interface. Temperature-dependent solvolysis allows one to estimate the overall Arrhenius type activation energy barrier associated with the reaction.

Entropy production theorems and some consequences.

The total entropy production fluctuations are studied in some exactly solvable models. For these systems, the detailed fluctuation theorem holds even in the transient state, provided initially that the system is prepared in thermal equilibrium. The nature of entropy production during the relaxation of a system to equilibrium is analyzed.

Structural transitions in a crystalline bilayer: the case of Lennard-Jones and Gaussian core models.

We study structural transitions in a system of interacting particles arranged as a crystalline bilayer, as a function of the density ρ and the distance d between the layers. As d is decreased a sequence of transitions involving triangular, rhombic, square and centred rectangular lattices is observed. The sequence of phases and the order of transitions depends on the nature of the interactions.

Exploration of the dynamical evolution and the associated energetics of water nanoclusters formed in a hydrophobic solvent.

Exploration of the intermolecular binding energy in nanometer-sized small water clusters in hydrophobic solvents and its evolution with the increase in the cluster size until bulk-type geometry is reached constitute a fascinating area of research in contemporary chemical/biological physics. In this contribution we have used femtosecond/picosecond-resolved solvation dynamics and fluorescence anisotropy techniques to explore the dynamical evolution of water clusters in dioxane continuum as a function of water concentration. We have also used temperature dependent picosecond-resolved solvation dynamics in order to explore the magnitude of the intermolecular bonding energy in the water clusters in bulk dioxane.

Modulation of dynamics and reactivity of water in reverse micelles of mixed surfactants.

In this contribution, we attempt to correlate the change in water dynamics in a reverse micellar (RM) core caused by the modification of the interface by mixing an anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and a nonionic surfactant, tetraethylene glycol monododecyl ether (Brij-30), at different proportions, and its consequent effect on the reactivity of water, measured by monitoring the solvolysis reaction of benzoyl chloride (BzCl). The dimension of the RM droplets at different mixing ratios of AOT and Brij-30 (X(Brij-30)) has been measured using dynamic light scattering (DLS) technique. The physical properties of the RM water have been determined using Fourier transform infrared spectroscopy (FTIR) and compressibility studies, which show that with increasing X(Brij-30), the water properties tend toward that of bulk-like water.

Effects of nondenumerable fixed points in finite dynamical systems.

The motion of a spinning soccer ball brings forth the possible existence of a whole class of finite dynamical systems where there may be a nondenumerably infinite number of fixed points. They defy the very traditional meaning of the fixed point that a point on the fixed point in the phase space should remain there forever, for, a fixed point can evolve as well! Under such considerations one can argue that a free-kicked soccer ball should be nonchaotic.

Temperature-dependent solvation dynamics of water in sodium bis(2-ethylhexyl)sulfosuccinate/isooctane reverse micelles.

In this paper, for the first time, we report a detailed study of the temperature-dependent solvation dynamics of a probe fluorophore, coumarin-500, in AOT/isooctane reverse micelles (RMs) with varying degrees of hydration (w0) of 5, 10, and 20 at four different temperatures, 293, 313, 328, and 343 K. The average solvation time constant becomes faster with the increase in w0 values at a particular temperature. The solvation dynamics of a RM with a fixed w0 value also becomes faster with the increase in temperature.

Hydration in protein folding: thermal unfolding/refolding of human serum albumin.

Human serum albumin (HSA) is known to undergo both reversible and irreversible thermal unfolding and refolding, depending upon the experimental conditions (end temperature) at neutral pH. In this report we have used high precision densimetric and ultrasonic measurements to determine the apparent specific volume (phi v) and compressibility (phi k) of HSA at different unfolded and refolded states at two different end temperatures, 55 degrees C and 70 degrees C. The unfolded and refolded states were characterized using dynamic light scattering (DLS), circular dichroism (CD), picosecond-resolved fluorescence decay, and anisotropy of the single-tryptophan residue in HSA (Trp214).

Effect of size reduction on charge ordering in La0.5Ca0.5MnO3.

In this paper we report size-induced collapse of charge ordering in nanoparticles of La0.5Ca0.5MnO3 (LCMO).

Temperature-dependent hydration at micellar surface: activation energy barrier crossing model revisited.

In recent years, the validity of the activation energy barrier crossing model at the micellar surface brings notable controversy (Sen, P.; Mukherjee, S.; Halder, A.