Preparation of AlON Powder by Carbothermal Reduction and Nitridation with Assisting by Silane Coupling Agent.

In the preparation processes of aluminum oxynitride (AlON) powders by carbothermal reduction and nitridation, the homogeneity of mixed raw powders between Al2O3 and C is a critical factor by which the final composition and related properties of AlON transparent ceramic will be decided. In this paper, a silane coupling agent was used as a dispersant to optimize the distribution uniformity of raw material of Al2O3 and C, and the preparation of AlON powder with controllable composition and its distribution is investigated. The results show that the silane dispersant could effectively improve the distribution uniformity of raw material. The silane coupling agent contains functional groups of -SiH3 and -CnH2n+1O. XPS showed that the silane could react with C and Al2O3 to form the Si-C bond and C-Al2O3 bond, respectively. The silane coupling agent provides a connected bridge for raw material powders. When the amount of the silane was 5 wt%, the mixed powder had a great distribution uniformity. The addition of silane coupling agent improved the reactivity of raw materials and decreased the synthesis temperature of AlON. The single-phase AlON powder was obtained after the Al2O3/C mixed powder was kept at 1670 °C for 30 min. Furthermore, the grain size of AlON powder was 100-200 nm with an AlN content of 27.5 mol%. With the increase of holding time to 4 h, the grain size increased to 15 µm, indicating that sintering between particles occurred, which may reduce the sintering activity of the powder.

Near-Infrared Acceptors with Imide-Containing End Groups for Organic Solar Cells.

Near-infrared electron acceptors for organic solar cells (OSCs) mostly contain electron-withdrawing 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) end groups, which can be modified by but limited to phenyl, thienyl, and naphthyl units with halogenated, methyl, and methyloxy substitution. In this work, we employed an imide-containing unit to construct a new IC end group, based on which a series of new electron acceptors were synthesized. The strong electron-deficient nature of imide units enables the new acceptors to show efficient intramolecular charge transfer and hence red-shifted absorption spectra compared to their IC counterparts. These new electron acceptors were applied to OSCs, providing efficiencies of over 17% with a low voltage loss of 0.52 eV. These results demonstrate that the new imide-containing end groups are promising fragments for the construction of near-infrared electron acceptors for high-performance OSCs.

A cyclometalating organic ligand with an Iridium center toward dramatically improved photovoltaic performance in organic solar cells.

Organometallic compounds as photoactive materials are relatively new in organic solar cells. Upon cyclometalation, the octahedral heteroleptic Ir complex TBzIr exhibits significantly enhanced optical-absorption and improved film-morphology compared to the planar organic 2-(5''-hexyl-[2,2':5',2''-terthiophen]-5-yl)benzo[d]thiazole (TBz) ligand. Thus, a dramatically improved power conversion efficiency (PCE) from ∼0 to 3.81% is attained when combined with PC71BM.

Layer-by-layer assembled graphene oxide composite films for enhanced mechanical properties and fibroblast cell affinity.

The mechanical properties of films are of great importance for their use as biocompatible surface coatings or for drug encapsulation and release. In this study, layer-by-layer (LbL) assembled graphene oxide (GO) nanocomposite films were constructed, aimed at improving the mechanical properties of polyelectrolyte multilayer (PEM) films containing poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH). The mechanical properties of the films were evaluated via a nanoindentation technique. It was demonstrated that the elastic modulus (Er) could be improved by up to 181% by one layer of GO deposition in ten bilayers of polyelectrolyte, while the Er value of [(PAH/GO)10/PAH/PSS]30 film showed more than 5-fold enhancement over the native PEM film (PAH/PSS)330. The hardness (H) also increased significantly, from 0.295 GPa to 2.79 GPa for the (PAH/PSS)330 film and the [(PAH/GO)10/PAH/PSS]30 film, respectively. These results support the idea that the mechanical properties of the film could be tuned by varying the number of layers of GO in the multilayer architecture. Furthermore, the effect of the LbL-assembled GO composite films on fibroblast cell behavior was investigated. Cell proliferation and cell adhesion were qualified by MTT assay and fluorescent labeling using an image analysis system. Obviously, when compared with the native PEM films, the cells showed faster proliferation and larger spreading area, and formed more numerous and better organized adhesion points on the GO composite films. This indicated a higher affinity of fibroblasts for the LbL-assembled GO nanocomposites. The strategy promises a new way to construct nanofilms that are simultaneously mechanically rigid and bioactive, which is crucial for cell-contacting biomedical and biotechnological applications.