All solution processable organic photovoltaic cells using DMDCNQI as an organic N-type buffer layer

Organic photovoltaic cells consisting of ITO/PEDOT-PSS/P3HT:PCBM/TiO(x)/DMDCNQI/Al have been fabricated by using dip-coated DMDCNQI layer as a cathode buffer material. We have investigated the physical effects of charge transfer complex and wettability of DMDCNQI between TiO(x)/P3HT:PCBM layer and Al cathode electrode on the performance of organic photovoltaic cell. The photovoltaic cell fabricated with a dip-coated DMDCNQI layer exhibited almost similar performance compared to the device using conventional evaporated DMDCNQI layer. Especially, the power conversion efficiency of the prepared organic photovoltaic cell using TiO(x)/DMDCNQI layer was improved to 3.1%, which is mainly due to the decrease in the low contact resistance of organic-metal interface.     

Source-detector calibration in three-dimensional Bayesian optical diffusion tomography

Optical diffusion tomography is a method for reconstructing three-dimensional optical properties from light that passes through a highly scattering medium. Computing reconstructions from such data requires the solution of a nonlinear inverse problem. The situation is further complicated by the fact that while reconstruction algorithms typically assume exact knowledge of the optical source and detector coupling coefficients, these coupling coefficients are generally not available in practical measurement systems. A new method for estimating these unknown coupling coefficients in the three-dimensional reconstruction process is described. The joint problem of coefficient estimation and three-dimensional reconstruction is formulated in a Bayesian framework, and the resulting estimates are computed by using a variation of iterative coordinate descent optimization that is adapted for this problem. Simulations show that this approach is an accurate and efficient method for simultaneous reconstruction of absorption and diffusion coefficients as well as the coupling coefficients. A simple experimental result validates the approach.     

Graphene–Ruthenium Complex Hybrid Photodetectors with Ultrahigh Photoresponsivity

The maximum responsivity of a pure monolayer graphene‐based photodetector is currently less than 10 mA W^?1 because of small optical absorption and short recombination lifetime. Here, a graphene hybrid photodetector functionalized with a photoactive ruthenium complex that shows an ultrahigh responsivity of ≈1 × 10⁵ A W^?1 and a photoconductive gain of ≈3 × 10⁶ under incident optical intensity of the order of sub‐milliwatts is reported. This responsivity is two orders of magnitude higher than the precedent best performance of graphene‐based photodetectors under a similar incident light intensity. Upon functionalization with a 4‐nm‐thick ruthenium complex, monolayer graphene‐based photodetectors exhibit pronounced n‐type doping effect due to electron transfer via the metal?ligand charge transfer (MLCT) from the ruthenium complex to graphene. The ultrahigh responsivity is attributed to the long lifetime and high mobility of the photoexcited charge carriers. This approach is highly promising for improving the responsivity of graphene‐based photodetectors.     

Zirconium oxide nanotube surface prompts increased osteoblast functionality and mineralization

Electrochemical formation of tunable nanoscale oxide layers on biomedical metallic surfaces has recently drawn much attention in biomaterials research. In this study, we report on the cellular response to a unique vertically aligned, laterally spaced nanotube nanostructure made of zirconium oxide (ZrO₂) fabricated by anodization. The growth, morphology, and functionality of osteoblasts cultured on ZrO₂ nanotubes have been investigated. The initial adhesion and spreading was considerably improved on the nanotube surface as compared to a flat zirconium (Zr) surface without a nanostructure. The morphology of the adhered cells on the nanotube surface elicited a highly organized cytoskeleton with crisscross patterned actin, which was lacking on the flat Zr. Increased alkaline phosphatase activity levels and the formation of calcified extracellular matrix implied improved osteoblast functionality and mineralization on the nanotube substrate. This in vitro study suggests that the ZrO₂ nanotubes provided an enhanced osteoblast response and demonstrated their apparent role in providing a platform for bone growth.     

Sonochemical synthesis of PANI-BiVO4-GO semiconductor nanocomposite highly efficient visible-light photocatalytic performance

Abstract

Polyaniline/Bismuth Vanadate/Graphene Oxide (PANI-BiVO₄-GO) or BGPA composite was prepared by sonochemical deposition of bismuth vanadate-graphene oxide (BiVO₄) nanoparticles on the surface of polyaniline (PANI). The best photocatalytic degradation performance was obtained by 5wt% BGPA composites for MB, RhB, and SO dyes, which is approximately 4 times higher than that of 1% BGPA. Meanwhile, the photocatalytic stability of BiVO₄ was significantly improved by introducing PANI into the PANI-BiVO₄-GO composite. The dramatic promotion of the photocatalytic degradation performance and the photocatalytic stability can be attributed to the formation of a heterojunction free electron between PANI and BiVO₄-GO. The existence of those extra free electrons can dramatically enhance the efficiency of the photogenerated electrons, which accelerate the transfer of photogenerated holes from BiVO₄-GO to PANI, and therefore inhibit the self-oxidation of BiVO₄.     

A finite element ductile failure simulation method using stress-modified fracture strain model

This paper proposes a new method to simulate ductile failure using finite element analysis based on the stress-modified fracture strain model. A procedure is given to determine the stress-modified fracture strain as a function of the stress triaxiality from smooth and notched bar tensile tests with FE analyses. For validation, simulated results using the proposed method are compared with experimental data for cracked bar (tensile and bend) tests, extracted from API X65 pipes, and for full-scale burst test of gouged pipes, showing overall good agreements. Advantages in the use of the proposed method for practical structural integrity assessment are discussed.     

Photoelectrocatalytic properties and bactericidal activities of silver-treated carbon nanotube/titania composites

Two types of carbon nanotube/TiO₂ and silver-treated carbon nanotube/TiO₂ electrodes were prepared and characterized by X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray analysis, photoelectrocatalytic activity and antibacterial activity. The photoelectrocatalytic degradation of a methylene blue solution was attributed to the combined effects of the photo-degradation of TiO₂, the electron assistance of carbon nanotube network and the enhancement of silver and was a function of the applied potential. The composites treated with silver showed enhanced photo-degradation of methylene blue, and the photoelectrocatalytic activity increased with increasing amount of silver. The silver-treated carbon nanotube/TiO₂ prepared as bactericides have stronger antibacterial activity against Escherichia coli K-12 than standard ampicillin, tetracycline and carbon nanotube/TiO₂ under sunlight or dark conditions. The presence of silver in the silver-treated carbon nanotube/TiO₂ composites enhanced the inactivation of the E. coli K-12.     

Effects of acicular ferrite on charpy impact properties in heat affected zones of oxide-containing API X80 linepipe steels

This study was concerned with effects of acicular ferrite on Charpy impact properties in heat affected zones (HAZs) of two API X80 linepipe steels containing oxides. In the one steel, Mg and O₂ were additionally added to form a larger amount of oxides than the other steel, which was a conventional X80 steel containing a considerable amount of Al and Ti. Various HAZ microstructures were obtained by conducting HAZ simulation tests under different heat inputs of 35 kJ cm⁻¹ and 60 kJ cm⁻¹. Oxides present in the API X80 linepipe steels were complex oxides whose average size was 1-2 μm, and the number of oxides increased with increasing amount of Mg and O₂. The volume fraction of acicular ferrite present in the steel HAZs increased with increasing number of oxides, and decreased with increasing heat input. When the volume fraction of acicular in the HAZ was higher than 20%, Charpy impact energy at −20 °C was higher than 100 J as the ductile fracture mode was dominant. Particularly in the steel HAZs having a larger amount of oxides, Charpy impact properties were excellent because oxides worked as nucleation sites of acicular ferrite during welding. Charpy impact properties of the HAZs could be well correlated with the volume fraction of acicular ferrite and number of oxides under different heat input conditions.