Zackary Chiragwandi

Solid and soft nanostructured materials: Fundamentals and applications

The scientific work worldwide on nanostructured materials is extensive as well as the work on the applications of nanostructured materials. We will review quasi two-, one- and zero-dimensional solid and soft materials and their applications. We will restrict ourselves to a few examples from partly fundamental aspects and partly from application aspects. We will start with trapping of excitons in semiconductor nanostructures. The subjects are: physical realizations, phase diagrams, traps, local density approximations, and mesoscopic condensates. From these fundamental questions in solid nanomaterials we will move to trapping of molecules in water using nanostructured electrodes. We will also discuss how to manipulate water (create vortices) by nanostructure materials. The second part deals with nanorods (nano-wires). Particularly we will exemplify with ZnO nanorods. The reason for this is that ZnO has: a very strong excitons binding energy (60 meV) and strong photon-excitons coupling energy, a strong tendency to create nanostructures, and properties which make the material of interest for both optoelectronics and for medical applications. We start with the growth of crystalline ZnO nanorods on different substrates, both crystalline (silicon, silicon carbide, sapphire, etc) and amorphous substrates (silicon dioxide, plastic materials, etc) for temperatures from 50 degrees C up to 900 degrees C. The optical properties and crystalline properties of the nanorods will be analyzed. Applications from optoelectronics (lasers, LEDs, lamps, and detectors) are analyzed and also medical applications like photodynarnic cancer therapy are taken up. The third part deals with nano-particles in ZnO for sun screening. Skin cancer due to the exposure from the sun can be prevented by ZnO particles in a paste put on the exposed skin.

MODELLING LIVING FLUIDS WITH THE SUBDIVISION INTO THE COMPONENTS IN TERMS OF PROBABILITY DISTRIBUTIONS

As it follows from the results of C. H. Waddigton, F. E. Yates, A. S. Iberall, and other well-known bio-physicists, living fluids cannot be modelled within the frames of the fundamental assumptions of the statistical-mechanics formalism. One has to go beyond them. The present work does it by means of the generalized kinetics (GK), the theory enabling one to allow for the complex stochasticity of internal properties and parameters of the fluid particles. This is one of the key features which distinguish living fluids from the nonliving ones. It creates the disparity of the particles and hence breaks the each-fluid-component-uniformity requirement underlying statistical mechanics. The work deals with the corresponding modification of common kinetic equations which is in line with the GK theory and is the complement to the latter. This complement allows a subdivision of a fluid into the fluid components in terms of nondiscrete probability distributions. The treatment leads to one more equation that describes the above internal parameters. The resulting model is the system of these two equations. It appears to be always nonlinear in case of living fluids. In case of nonliving fluids, the model can be linear. Moreover, the living-fluid model, as a whole, cannot have the thermodynamic equilibrium, only partial equilibriums (such as the motional one) are possible. In contrast to this, in case of nonliving fluids, the thermodynamic equilibrium is, of course, possible. The number of the fluid components is treated as the number of the modes of the particle-characteristic probability density. In so doing, a fairly general extension of the notion of the mode from the one-dimensional case to the multidimensional case is proposed. The work also discusses the variety of the time-scales in a living fluid, the simplest quantum-mechanical equation relevant to living fluids, and the non-equilibrium nonlinear stochastic hydrodynamics option. The latter is simpler than, but conceptually comparable to, stochastic kinetic equations. A few directions for future research are suggested. The work notes a cohesion of mathematical physics and fluid mechanics with the living-fluid-related fields as a complex interdisciplinary problem.

dc characteristics of a nanoscale water-based transistor

We demonstrate a nanoscale water-based transistor. The presented nanoscale water-based transistor relies on the controlled modification of the pH in deionized water through the base applied electric field. The dc characteristics are presented and studied with a focus on the influence of the base applied electric field, the base electrode design, and their proximity to the sensing emitter and collector nanoelectrodes. The demonstrated water-based nanoscale device is of interest for many bioelectrical applications due to the biocompatibility and the wide usage and presence of water in biological systems.

Vortex rings in pure water under static external electric field

The reproducible development of vortex rings in pure water under the action of a static external electric field is demonstrated. The phenomenon results from the electrochemical decomposition of water. Given the low conductivity of water in the absence of electrolyte, the field-driven buildup of hydroxide ions at the anode becomes essential to the proton release, which in turn is the result of the molecular O-2(g) evolution. Water recombination processes, which have protons flowing in a hydroxide background, as a key ingredient produce the phenomenon

Ultraviolet driven negative current and rectifier effect in self-assembled green fluorescent protein device

UV induced negative current produced at low voltages is reported in a photocurrent rectifier device consisting of a sensing region between two nano Al/Al2O3 electrodes placed 30 nm apart, employing a droplet of enhanced green fluorescent protein as molecular electrolyte. The current-voltage characteristics are discussed in terms of the properties of the thin Al2O3 scale, the position of the Fermi level, the position of the highest occupied molecular orbital-lowest unoccupied molecular orbital gap, and dispersion of states induced by varying dielectric constants.

Robustness of logic gates and reconfigurability of neuromorphic switching networks

Nanoparticle networks with functional molecular links that show current-voltage characteristics (IVC) with negative differential resistance (NDR) can be trained to perform XOR-AND logic gates (Husband et al. [1]; Skoldberg and Wendin [2]). In this work we investigate the robustness of the Nanocell network by removing links until desired logic gates no longer can be configured or operated within our simulation of the network. We present results for the robustness of XOR-AND configured (halfadder) Nanocells, as well as the effects of varying the IVC and NDR characteristics of the linker molecules.