Effect of interface traps on Debye thickness semiconductor films

The presence of the boundary interface trapping states and their role in determining the properties of Debye thickness thin semiconductor films, are demonstrated experimentally, using PbTe films deposited on mica. These charged states could not be observed earlier and be studied directly, because of the screening by the relatively high carrier density of the ordinary PbTe. Thin, Debye length thickness, PbTe films with a high concentration of interface trapping centers, possess an extraordinary high resistance. In this case the thermostimulated capacitor discharge method can be successfully applied to determine the energy of these levels, their carrier capture cross-sections and their donor- or acceptor-like character. The experimental results and theoretical calculations are discussed.     

Electroaddressable Selective Functionalization of Electrode Arrays: Catalytic NADH Detection Using Aryl Diazonium Modified Gold Electrodes

We report the application of 4‐nitrophenyl diazonium modified electrodes towards the electrochemical detection of NADH. Selective activation of individual electrodes on a 5 element array by electro‐addressable conversion of nitro groups to amines and subsequent EDC/NHS crosslinking to the NADH oxidant, pyrroloquinoline quinone (PQQ), is demonstrated. Inactivated electrodes retained nitro functionality and were protected against non‐specific adsorption and mild chemical reactions. Electrodeposition conditions were used to control nitrophenyl film thickness and showed that while increased film thickness leads to greater functionalization density of PQQ, it also results in decreased electron transfer kinetics. The electrodeposition protocol can therefore serve as a method to control electrode functionalization density and film electron transfer kinetics. We believe this simple technique for selective electrode functionalization may facilitate the development of next generation multianalyte electrochemical sensors.     

Electrodeposition of Dye-Doped Titania Thin Films

We extend our novel low-voltage electrochemical method for oxide thin film formation from sol-gel monomers to include entrapment of organic molecules within the films. We also describe an extension of the method to titania thin films, which are obtained from titanium tetra-n-propoxide in alcoholic solutions by applying potentials in the range of +2.0 to ?1.4 V to indium tin oxide electrodes. The film thickness (ranging between 20–1000 nm) is controllable by changing either the potential or the duration of its application. We demonstrate that this electrochemical method provides a convenient way for entrapment of organic dopants within the film. Four dyes were used for that purpose: Basic Blue 41, methylene-blue, tris(2,2′-bipyridine)iron(II) and tris(2,2′-bipyridine)ruthenium(II).     

Electrochemically induced sol-gel deposition of zirconia thin films

A novel electrochemical method for deposition of ZrO(2) thin films is described. The films, 50-600 nm thick, were obtained by applying moderate positive or negative potentials (+2.5 V to -1.5 V versus SHE) on conducting surfaces immersed in a 2-propanol solution of zirconium tetra-n-propoxide [Zr(OPr)(4)] in the presence of minute quantities of water (water/monomer molar ratios in the range of 10(-5) to 10(-1)), which was the limiting reagent. Oxidative electrochemical formation of solvated H(+) and reductive formation of OH(-) catalyze the hydrolysis and condensation of the metal alkoxide precursor. The magnitude of the applied potential and its duration provide a convenient way of controlling the film thickness. The films consist of an amorphous phase, as revealed by XRD measurements. The effects of different parameters, such as the applied potential and its duration, the amount of added water and the current-time characteristics, were studied. A mechanism for the electrodeposition of the zirconia films which is in accordance with our findings is proposed.     

Ship routing and scheduling in the new millennium

We review research on ship routing and scheduling and related problems during the new millennium and provide four basic models in this domain. The volume of research in this area about doubles every decade as does the number of research outlets. We have found over a hundred new refereed papers on this topic during the last decade. Problems of wider scope have been addressed as well as more specialized ones. However, complex critical problems remain wide open and provide challenging opportunities for future research.     

Core–Shell PbI2@WS2 Inorganic Nanotubes from Capillary Wetting

Multiwall WS ₂ nanotube templates were used as hosts to prepare core–shell PbI₂@WS₂ nanotubes by a capillary‐wetting method. Conformal growth of PbI₂ layers on the inner wall of the relatively wide WS₂ nanotubes (i.d. ca. 10 nm) leads to nanotubular structures which were not previously observed in narrow carbon nanotube templates. Image simulation after structural modeling (see picture) showed good agreement with the experimental HRTEM image.

     

How many matrices can be spectrally balanced simultaneously?

We prove that any ? positive definite d × d matrices, M₁,...,M_?, of full rank, can be simultaneously spectrally balanced in the following sense: for any k < d such that ? ≤ \(\ell \leqslant \left\lfloor {\frac{{d - 1}}{{k - 1}}} \right\rfloor \), there exists a matrix A satisfying \(\frac{{{\lambda _1}\left( {{A^T}{M_i}A} \right)}}{{Tr\left( {{A^T}{M_i}A} \right)}} < \frac{1}{k}\) 1/k for all i, where λ₁(M) denotes the largest eigenvalue of a matrix M. This answers a question posed by Peres, Popov and Sousi ([PPS13]) and completes the picture described in that paper regarding sufficient conditions for transience of self-interacting random walks. Furthermore, in some cases we give quantitative bounds on the transience of such walks.     

Aggregation and dispersion of small hydrophobic particles in aqueous electrolyte solutions

The effect of salts on the solvent-induced interactions between hydrophobic particles dispersed in explicit aqueous solution is investigated as a function of the salt's ionic charge density by molecular dynamics simulations. We demonstrate that aggregates of the hydrophobic particles can be formed or dissolved in response to changes in the charge density of the ions. Ions with high charge density increase the propensity of the hydrophobic particles to aggregate. This corresponds to stronger hydrophobic interactions and a decrease in the solubility (salting-out) of the hydrophobic particles. Ions with low charge density can either increase or decrease the propensity for aggregation depending on whether the concentration of the salt is low or high, respectively. At low concentrations of low charge density ions, the aggregate forms a "micelle-like" structure in which the ions are preferentially adsorbed at the surface of the aggregate. These "micelle-like" structures can be soluble in water so that the electrolyte can both increase the solubility and increase aggregation at the same time. We also find, that at the concentration of the hydrophobic particles studied (approximately 0.75 m), the aggregation process resembles a first-order transition in finite systems.     

The synthesis of a phosphadecalone system

The 2-phosphabicyclo[4.4.0]decan-5-onic system (2) was synthesized by a double Michael addition of phenylphosphine to propenylcyclohexenyl ketone (1). This dienone (1) can be prepared starting from either cyclohexanone by a known method, or from cyclohexene by its acylation with crotonic anhydride in the presence of SnCl₄. The NMR of the phosphine and several of its derivatives in comparison with the aza analog, as well as the Mass spectra fragmentation pattern, are discussed,     

Atrazine degradation by Pseudomonas strain ADP entrapped in sol-gel glass

Sol-gel entrapment was evaluated as a method for immobilization of an atrazine degrading Pseudomonas. It was found that the bacterium lost much of its atrazine degrading activity upon immobilization. However, partial activity could have been restored by amendment of nutrients. Bacteria immobilized using a prehydrolysis technique for the preparation of the sol-gel, retained better activity in comparison to bacteria immobilized using a composite calcium alginate/sol-gel procedure. Further study is underway to improve the activity of sol-gel entrapped bacteria.