Thermally evaporated Ag nanoparticle films for plasmonic enhancement in organic solar cells: effects of particle geometry

We report on the simple fabrication of Ag NP films via thermal evaporation and subsequent annealing. The NPs are formed on indium tin oxide electrodes, coated with PEDOT:PSS and implemented into PCPDTBT:PC70BM solar cells. Scanning electron microscopy and atomic force microscopy are used to determine the size distributions and surface coverage of the NP film. We apply finite‐difference time‐domain techniques to model the optical properties of different nanoparticle films and compare this with the absorption properties of the organic active layer. The simulations demonstrate that the absorption and scattering efficiency of the particles are very sensitive to particle geometry. Solar cells prepared with window electrodes containing NP layers with less surface coverage, show a 14.8% improvement in efficiency. We discuss variations in the external quantum efficiency of the devices in terms of forward scattering and parasitic absorption losses induced by the NP layer. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

An interesting route using electron-beam lithography and photolithography to pattern submicron interdigitated electrodes array for sensing applications

Journal of the Iranian Chemical Society - Increasing the interest in the silicon-based devices resulted in developing new methods and techniques to achieve advanced and more reliable designs and...     

A Spiderweb‐Like Metal–Organic Framework Multifunctional Foam

Processing metal–organic frameworks (MOFs) into hierarchical macroscopic materials can greatly extend their practical applications. However, current strategies suffer from severe aggregation of MOFs and limited tuning of the hierarchical porous network. Now, a strategy is presented that can simultaneously tune the MOF loading, composition, spatial distribution, and confinement within various bio‐originated macroscopic supports, as well as control the accessibility, robustness, and formability of the support itself. This method enables the good dispersion of individual MOF nanoparticles on a spiderweb‐like network within each macrovoid even at high loadings (up to 86 wt %), ensuring the foam pores are highly accessible for excellent adsorption and catalytic capacity. Additionally, this approach allows the direct pre‐incorporation of other functional components into the framework. This strategy provides precise control over the properties of both the hierarchical support and MOF.     

Chitosan surface modified hydrogel as a therapeutic contact lens

Therapeutic contact lenses have attracted significant attention during the last decades. In this study, we used chitosan‐conjugated poly(2‐hydroxyethyl methacrylate) (PHEMA) for contact lens application. We aimed to increase affinity of anionic drugs, which are used in treatment of eye diseases. In this regard, we evaluated delivery of the small molecule anionic drug, ascorbic acid from the chitosan‐conjugated PHEMA. Chitosan immobilization improves drug loading efficiency and induces sustained release of ascorbic acid. The chitosan modified hydrogel also reduces the biofouling of tear fluid components. Our results showed that surface modification by chitosan inhibits protein and bacterial deposition on the contact lens. Protein absorption analysis revealed that neat PHEMA adsorbed tear proteins at a density of 28.4 ± 4.4 μg/cm², whereas the chitosan‐conjugated hydrogel adsorbed tear proteins at a density of 18.5 ± 1.8 μg/cm². Moreover, the neat PHEMA bacterial adhesion had a mean CFU value of 273 ± 27. However, a significant decrease in the number of bacterial colonies was observed in the chitosan group with a CFU value of 9 ± 6.     

Nonlinear bending behavior of orthotropic Mindlin plate resting on orthotropic Pasternak foundation using GDQM

Rectangular plates resting on elastic foundations are operational activities of large transportation aircraft on runways, footings, foundation of spillway dam, civil building in cold regions, and bridge structures. Hence, in the present work, nonlinear bending analysis of embedded rectangular plates is investigated based on orthotropic Mindlin plate theory. The elastic medium is simulated by orthotropic Pasternak foundation. Adopting the nonlinear strain–displacement relation, the governing equations are derived based on energy method and Hamilton’s principle. The generalized differential quadrature method is performed for the case when all four ends are clamped supported. The influences of the plate thickness, shear-locking, elastic medium constants, and applied force on the nonlinear bending of the rectangular plate are studied. Results indicate that increasing the plate thickness decreases the deflection of the plate. It is also observed that increasing the applied force increases the deflection of the plate. Furthermore, considering elastic medium decreases deflection of the plate, and the effect of the Pasternak-type is higher than the Winkler-type on the maximum deflection of the plate. Also, it is found that the present results have good agreement with previous researches.     

Combined effects of holes and winglets on chevron plate-fins to enhance the performance of a plate-fin heat exchanger working with nanofluid

ABSTRACT

The current work reports an experimental study on hydrothermal improvement in a chevron plate-fin heat exchanger combined with holes and winglets. The experiments are performed for water flow through a test square duct fitted with enhanced chevron plate-fins for the Reynolds number from 4000 to 10000. Characteristics of the enhanced chevron plate-fins include three waviness aspect ratios and four different arrangements of holes and winglets at a constant diameter of holes and width/height of winglets. An overall performance factor is applied to obtain the optimal geometry. Then, only the optimal geometries are applied to find out the effect of Al₂O₃/water nanofluid flow on the performance of a plate-fin heat exchanger. In comparison to simple chevron plate-fins, the enhanced ones would increase the Nusselt number by a factor between 1.05% and 1.6%. In addition, simultaneous application of the optimal enhanced chevron plate-fins and the nanofluid could increase the Nusselt number. The best working conditions of this system are detected for the nanofluid at a weight fraction of 0.3%.     

Magnetic field dependence optical properties of GaN/AlN multiple quantum wells

In this work, we have investigated the optical properties of some multiple quantum wells under the influence of an external magnetic field and (for the first time) number of wells. We have retained the total length of the structure constant which is technologically important. Then we have detected a blue shift in the absorption peak positions due to the application of the magnetic field and a red shift due to the increasing of the number of wells. The red shift is only seen in the multiple quantum wells with odd number of wells and the absorption peaks of the multiple quantum well with even number of wells are not changed.     

Role of the velocity frame of reference in thermodiffusion in liquid mixtures

The role and significance of the velocity frame of reference in the interpretation, modeling and formulation of thermodiffusion in multicomponent liquid mixtures were investigated, focused on the nonequilibrium thermodynamics modeling approach. The effect of the velocity frame of reference on the phenomenological equations and thermodiffusion coefficients and expressions is explored. Theoretically and also by the aid of representative calculations, it is shown that while in binary mixtures transformation from one frame to another does not affect the sign and magnitude of the thermodiffusion coefficients, in multicomponent mixtures (ternary and higher), even the sign of the thermodiffusion coefficients may change when an alternative frame is used. This implies that in multicomponent mixtures for either experimental data or model estimations, the employed velocity frame for the thermodiffusion coefficients plays an important role in calculations. The Soret coefficients and the thermodiffusion factors are independent of the frame of reference.     

Structural and electronic properties of pyrrolidine-functionalized [60]fullerenes

We have investigated energetic, geometric, electronic, and field emission properties of three recently synthesized fulleropyrrolidines based on the density functional theory method B3LYP/6-31G(d). Fulleropyrrolidines show higher conductivity, and solubility in water, and smaller work function in comparison with the pristine C₆₀ fullerene. The functionalization of C₆₀ with different pyrrolidines containing 3NH₂, NO, or NO₂ groups transforms it to an n-type semiconductor. The functionalization can also dramatically enhance the electrophilicity of the C₆₀ about 23–37%. Moreover, it should be mentioned that the work function is mainly influenced by the pyrrolidine containing 3NO₂ group whereas the conductivity is largely affected by the one containing 3NH₂ functionality.     

H-point standard addition method for simultaneous spectrophotometric determination of Co(II) and Ni(II) by 1-(2-pyridylazo)2-naphthol in micellar media

A very simple and selective spectrophotometric method for simultaneous determination of Co(II) and Ni(II) by 1-(2-pyridylazo) 2-naphthol (PAN), in micellar media, using H-point standard addition method (HPSAM) is described. The ligand and its metal complexes (Co(II)-PAN and Ni(II)-PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. Formation of both the complexes was complete within 10 min at pH 9 (adjusted by ammonia buffer). The linear range was 0.10-2.00 microg ml(-1) for Co(II) and 0.05-1.50 microg ml(-1) for Ni(II). The relative standard deviation (R.S.D.) for the simultaneous determination of 0.50 microg ml(-1) each of Co(II) and Ni(II) was 2.32 and 3.13%, respectively. Interference effects of common anions and cations were studied and the method was applied to simultaneous determination of Co(II) and Ni(II) in alloy samples. The method was compared with derivative spectrophotometric method.