Electroprotic reactions

Reactions involving the coupled transfer of electrons and protons are called electroprotic reactions. In this article we briefly describe some of our experiences with electroprotic reaction as a tool for executing interesting chemical transformations.     

Pattern formation of zinc nanoparticles in silica film by electrodeposition

Zinc nanoparticles were grown within gel-derived silica films by applying a direct current voltage. Pattern formation of metallic Zn was studied as a function of applied voltage and metal-silica ratio. Average particle size varied from 5.2 to 20.2 nm by changing the applied voltage and silica concentration. It was found that the transition from fractal to dendritic morphology was possible due to crystalline anisotropy. From high-resolution transmission electron microscopy images and X-ray diffraction pattern a possible model is proposed to explain this observation.     

Structural damage assessment in a cantilever beam with a breathing crack using higher order frequency response functions

Vibration measurements offer an effective, inexpensive and fast means of non-destructive testing of structures and various engineering components. There are mainly two approaches to crack detection through vibration testing; open crack model with emphasis on changes in modal parameters and secondly, the breathing crack model focusing on nonlinear response characteristics. The open crack model based on linear response characteristics can identify the crack only at an advanced stage. Researchers have shown that a structure with a breathing crack behaves more like a nonlinear system, similar to that of a bilinear oscillator and the nonlinear response characteristics can very well be investigated to identify the presence of the crack. In the present study, the bilinear restoring force is approximated by a polynomial series and a nonlinear dynamic model of the cracked structure is developed using higher order frequency response functions. The effect of crack severity on the response harmonic amplitudes are investigated and a new procedure is suggested whereby the crack severity can be estimated through measurement of the first and second harmonic amplitudes.     

Synthesis and fluorescent properties of a new class of heterocycles of isoindole fused imidazoles with phenolic subunits

A new class of heterocycles of isoindole fused imidazoles with phenolic subunits has been readily synthesized by a two-step one-pot reaction. In aprotic solvent they show high fluorescent properties (Phi(F) up to 0.93), but in protic polar solvent fluorescent intensity decreases. They show green fluorescence in weak acidic medium such as acetic acid but lack emission in basic medium. The compounds can also stain human squamous epithelium cells.     

XRD and RBS study of annealing effects in titanium implanted a-silicon films

We have used ion implantation of 30 keV⁴⁸Ti⁺ ions into a-Si films at nominal doses of 10²⁰-10²¹ ions/m² to fabricate coherent silicide layers. Characterization of these layers and study of their annealing behaviour were carried out using XRD and RBS techniques. We find that the layers are a mixture of Ti₅Si₄, TiSi, TiSi₂ and Si. On annealing at relatively lower temperatures (up to ～ 300° C), predominant silicide phases present in the layer are Ti-rich, such as Ti₅Si₄ and TiSi. At higher temperatures, the Ti-rich layer has a tendency to consume unreacted Si from the film and to form a predominantly Si-rich silicide layer. A structure of silicon different from the diamond cubic structure is noticed in these implanted layers.     

Efficient approximately 2 microm Tm3+ -doped tellurite fiber laser

Laser emission in the range of 1.88-1.99 micrim from a Tm3+ -doped tellurite fiber is demonstrated when pumped with a diode-pumped Er3+/Yb3+-doped silica fiber laser operating at 1.57-1.61 microm. This pump source excites the Tm3+ ions directly into the F43 upper laser level and yields an output power of 280 mW with a slope efficiency of 76% in a 99%-12% laser cavity arrangement and a 32 cm long fiber. This result is very close to the Stokes efficiency limit of approximately 80%. This is, to the authors' knowledge, the first demonstration of high efficiency lasing in a tellurite fiber at wavelengths longer than 1.56 microm.     

Tm(3+)/Ho(3+) codoped tellurite fiber laser

Continuous-wave and Q-switched lasing from a Tm(3+)/Ho(3+) codoped tellurite fiber is reported. An Yb(3+)/Er(3+)-doped silica fiber laser operating at 1.6 microm was used as an in-band pump source, exciting the Tm(3+) ions into the (3)F(4) level. Energy is then nonradiatively transferred to the upper laser level, the (5)I(7) state of Ho(3+). The laser transition is from the (5)I(7) level to the (5)I(8) level, and the resulting emission is at 2.1 microm. For continuous wave operation, the slope efficiency was 62% and the threshold 0.1 W; the maximum output demonstrated was 0.16 W. Mechanical Q switching resulted in a pulse of 0.65 microJ energy and 160 ns duration at a repetition rate of 19.4 kHz.     

Simple Chemical Route Synthesis of Fe2O3 Nanoparticles and its Application for Adsorptive Removal of Congo Red from Aqueous Media: Artificial Neural Network Modeling

Nanocrystalline Fe₂O₃ powder was synthesized by a simple chemical route involving FeCl₃ and NaOH. The Fe₂O₃ powder thus prepared was characterized using x-ray diffraction study, scanning electron microscopy, and Fourier transform infrared spectroscopy. The adsorption properties of crystalline Fe₂O₃ powder have been investigated with an aim to explore a possible low cost and efficient way to remove Congo red (CR) from waste water. Fe₂O₃ powder was found as an excellent adsorbent for CR from aqueous medium. Adsorption capacity as much as 203.66 mg g^?1 is reported at room temperature. Effect of different experimental parameters such as reaction pH, initial CR dye concentration, adsorbent dose, and reaction temperature were studied on adsorption capacity of Fe₂O₃ powder and modeled by artificial neural network (ANN). Optimal ANN structure (4–5–1) shows minimum mean squared error (MSE) of 0.00235 and determination coefficient (R²) of 0.991 with Levenberg–Marquardt algorithm. Isotherm analysis of experimental data exhibited better fit to the Langmuir isotherm. The adsorption process was found to follow second-order kinetics as depicted by the analysis of experimental results. Thermodynamic study shows that the adsorption process is endothermic, spontaneous, and thermodynamically favorable in the temperature range of 27°C to 60°C.     

Applications of anisotropic slipline theory with non-uniform lattice rotation

Anisotropic slipline theory, with non-uniform lattice rotation field, is used to discuss new slipline solutions for the plane strain problems of punch indentation and mode 1 stationary crack in a ductile single crystal with piecewise linear yield locus. The proposed solution allows for both linear dislocation arrays and sectors with bulk dislocation density. Such features provide considerable latitude in the number of allowable stress discontinuities, and their orientation, when compared to the solutions which assume uniform lattice rotation.