Increase in open circuit voltage by the incorporation of band gap engineered FeS2 nanoparticle within MEHPPV solar cell

In this study we have synthesized and characterized FeS₂ nanoparticles with larger optical band gap (3.19 eV) and high thermal stability by hydrothermal route with capping reagent PEG 400. This high quality FeS₂ nanoparticle with higher band gap energy was applied as semiconducting acceptor in MEHPPV:FeS₂ nanoparticle based hybrid solar cells to improve the open circuit voltage. Variations in the property of FeS₂ have been done and confirmed by XRD, FE-SEM, TEM, FTIR, TGA, UV–VIS spectroscopy and Raman study. Two types of solar cells have been fabricated with structures: ITO/PEDOT:PSS/MEHPPV/Al and ITO/PEDOT:PSS/MEHPPV:FeS₂/Al. The open circuit voltage has been increased from 0.64 to 0.72 V by compositing FeS₂ nanoparticle within MEHPPV matrix.     

The utilization of specific interactions to enhance the mechanical properties of polysiloxane coatings

Moisture-curable polysiloxanes were modified with ionic groups to enable specific interactions between the polysiloxane matrix and silica nanoparticle reinforcement. A trimethoxysilane-functional quaternary ammonium salt (QAS) was used to modify the polysiloxane matrix. A comparison of the mechanical properties of coatings containing QAS modification to analogous coatings without QAS modification showed that QAS modification resulted in a dramatic improvement in mechanical properties of silica nanoparticle-reinforced coatings. QAS modification provided major enhancements in both tensile modulus and toughness. The coatings were characterized using positron annihilation spectroscopy, photo-acoustic FT-IR, differential scanning calorimetry, transmission electron microscope, and atomic force microscopy. The characterization results suggested that the QAS moieties present in the polysiloxane matrix undergo specific interactions with the surface of silica nanoparticles enabling an enhancement in interfacial adhesion between the polymer matrix and the nanoparticles. Most likely, the specific interaction that provided the enhanced mechanical properties was an ion–dipole interaction involving silanol groups present on the surface of the silica nanoparticles. The enhanced modulus and toughness of these polysiloxane materials may enable their application as a fouling-release coating for ship hulls, since current polysiloxane-based fouling release coatings suffer from poor mechanical properties and durability.     

Synthesis and antimicrobial activity of quaternary ammonium-functionalized POSS (Q-POSS) and polysiloxane coatings containing Q-POSS

An array of quaternary ammonium-functionalized POSS (Q-POSS) compounds were synthesized and their antimicrobial properties toward the Gram-negative bacterium, Escherichia coli, and the Gram-positive bacterium, Staphylococcus aureus, determined in aqueous solution. Using Q-POSS compositions that exhibited broad spectrum antimicrobial activity in solution, the utility of the Q-POSS compounds as an antimicrobial additive for polysiloxane coatings was determined. The results of the investigation showed that Q-POSSs possessing a relatively low extent of quaternization and longer alkyl chain lengths provided the highest antimicrobial activity in solution. For polysiloxane coatings containing Q-POSS molecules as an antimicrobial additive, coating surface energy, surface morphology, and antimicrobial properties were found to be strongly dependent on Q-POSS composition. Coatings based on Q-POSSs possessing the lowest extent of quaternization displayed antimicrobial activity while analogous coatings produced using Q-POSSs possessing the highest extent of quaternization showed no antimicrobial activity. The lack of antimicrobial activity exhibited by coatings possessing Q-POSSs with a relatively high extent of quaternization was attributed to agglomeration of Q-POSS molecules through the formation of intermolecular interactions involving the quaternary ammonium moieties. Agglomeration would be expected to reduce diffusivity and inhibit interaction of the Q-POSS molecules with microbial cells.     

Comparative and sensitivity study of flutter derivatives of selected bridge deck sections,Part 1: Analysis of inter-laboratory experimental data

Aeroelastic coefficients (flutter derivatives) of bridge decks are routinely extracted from wind tunnel section model experiments for the assessment of performance against wind loading. Two distinct methods, developed over the years, are usually employed for this purpose (free or forced vibration). Even though advantages and disadvantages of each technique have been highlighted by numerous researchers, few examples of a systematic comparison of the experimental results are available in the literature. The significance of this study is related to the evaluation of an extended set of experimental data on flutter derivatives, and includes the analysis and interpretation of the differences recorded through the two methods.The motivation for this work emerged from the United States–Japan Benchmark Study on Bridge Flutter Derivatives that Iowa State University (ISU) in the United States and the Public Works Research Institute (PWRI) in Japan, initiated in 2002. Tests were designed to cover a wide range of solid cross sections, from bluff (rectangular prisms) to streamlined, in particular considering the current trend of engineers to use aerodynamically-designed girders for bridges with longer spans. In this paper, a systematic analysis and a comparison of laboratory results of flutter derivatives obtained at both institutions were performed. In a companion paper, a sensitivity study was performed to examine the implications of the perceived dissimilarities among flutter-derivative data sets on the aeroelastic instability of long-span bridges (single-mode and coupled-mode).     

Study on the performance of sub 100 nm LACLATI MOSFETs for digital application

With the help of extensive simulations, we systematically investigated the effects of varying tilt angle of halo implant in sub 100 nm lateral asymmetric channel (LAC) MOSFETs on the reverse short channel effects, the on current and the hot carrier immunity. The devices with large angle tilt implants also show the substantial reduction in the subthreshold swing, improvement in I_ON/I_OFF ratio and significantly the lower junction capacitance as compared to the devices with low angle tilt implant. It is also observed that the subthreshold characteristics do not change as the channel length decreases for such devices. These devices, known as lateral asymmetric channel with large angle tilt implant (LACLATI), will therefore have much improved performance in comparison to a low angle tilt implant LAC devices for digital applications.     

Selective Zinc(II)‐Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

A highly ordered 2D‐hexagonal mesoporous silica material is functionalized with 3‐aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4‐methyl‐2,6‐diformyl phenol. Powder X‐ray diffraction, transmission electron microscopy, N₂ sorption, Fourier transform infrared spectroscopy, and UV‐visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn²⁺ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn²⁺‐bound mesoporous material increases significantly upon addition of various concentrations of Zn²⁺, while the introduction of other biologically relevant (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and environmentally hazardous transition‐metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn²⁺, evident from the large binding constant value (0.87 × 10⁴ M ^?1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn²⁺ from a mixture of ions that contains Zn²⁺ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy.     

Production of boron carbide powder by carbothermal synthesis of gel material

Boron carbide (B₄C) powder has been produced by carbothermal reduction of boric acid-citric acid gel. Initially a gel of boric acid-citric acid is prepared in an oven at 100°C. This gel is pyrolyzed in a high temperature furnace over a temperature range of 1000–1800 °C. The reaction initiation temperature range for B₄C formation is determined by thermal analysis. The optimal pyrolysis temperature of B₄C synthesis is investigated. During pyrolysis, the evaporation of boron-rich phases results in presence of free carbon in B₄C powder. The electron micrographs and particle size analyser reveal the generation of fine B₄C particles.     

High throughput combinatorial characterization of thermosetting siloxane–urethane coatings having spontaneously formed microtopographical surfaces

High throughput combinatorial characterization was performed on thermosetting siloxane–urethane coatings in order to find a correlation between the characterization techniques, surface topography, and adhesion strength of barnacles. A series of coatings having microtopographical surfaces with different domain sizes were prepared based on a thermosetting siloxane–urethane system. This microtopography was formed spontaneously during the film-formation process. These surfaces were characterized by atomic force microscopy (AFM), surface energy, dynamic contact angle, and pseudo barnacle pull-off adhesion and were compared to pure polyurethane (PU) and silicone rubber control. Surface energy and dynamic contact angles were measured by an automated surface energy measurement system and pull-off adhesion values were obtained from a high throughput pull-off adhesion measurement unit. The results were compared with the adhesion strength of barnacles. Presented at the 2006 FutureCoat! conference, sponsored by the Federation of Societies for Coatings Technology, in New Orleans, LA, on November 1–3, 2006.