RESUMEN
Self-powered ultraviolet (UV) photodetectors have attracted considerable attention in recent years because of their vast applications in the military and civil fields. Among them, self-powered UV photodetectors based on p-n heterojunction low-dimensional nanostructures are a very attractive research field due to combining the advantages of low-dimensional semiconductor nanostructures (such as large specific surface area, excellent carrier transmission channel, and larger photoconductive gain) with the feature of working independently without an external power source. In this review, a selection of recent developments focused on improving the performance of self-powered UV photodetectors based on p-n heterojunction low-dimensional nanostructures from different aspects are summarized. It is expected that more novel, dexterous, and intelligent photodetectors will be developed as soon as possible on the basis of these works.
RESUMEN
Lignocellulosic fiber (LCF)/CaCO3 (CG)/thermoplastic starch (TPS) composites were prepared by blending LCF/CG hybrid (82/18, g/g) with glycerin and corn starch in different weight ratios (0/35/100, 27/35/100, 54/35/100 and 81/35/100, g/g/g) at 130â, which were then characterized by rheology, XRD, SEM and DSC analysis, tensile test and soil burial test. When the dosage of LCF/CG was not more than 54 g, LCF and CG in LCF/CG/TPS composites were well dispersed, and the corresponding composites had better rheological properties. XRD results showed that the crystallinity of TPS in the presence of LCF/CG was significantly reduced after melt blending process, which caused by the inhibition effect of LCF on the crystallization of TPS. The tensile test results showed that the tensile strength, modulus and elongation at break of LCF/CG/TPS composite were better than those of pure TPS. Besides, due to the looser structures, LCF/CG/TPS composites biodegraded faster than pure TPS.
RESUMEN
The effects of both organically modified montmorillonite (OMMT) and Ni(2)O(3) on the carbonization of polypropylene (PP) during pyrolysis were investigated. The results from TEM and Raman spectroscopy showed that the carbonized products of PP were mainly multiwalled carbon nanotubes (MWNTs). Surprisingly, a combination of OMMT and Ni(2)O(3) led to high-yield formation of MWNTs. X-ray powder diffraction (XRD) and GC-MS were used to investigate the mechanism of this combination for the high-yield formation of MWNTs from PP. Brønsted acid sites were created in degraded OMMT layers by thermal decomposition of the modifiers. The resultant carbenium ions play an important role in the carbonization of PP and the formation of MWNTs. The degradation of PP was induced by the presence of carbenium ions to form predominantly products with lower carbon numbers that could be easily catalyzed by the nickel catalyst for the growth of MWNTs. Furthermore, carbenium ions are active intermediates that promote the growth of MWNTs from the degradation products with higher carbon numbers through hydride-transfer reactions. The XRD measurements showed that Ni(2)O(3) was reduced into metallic nickel (Ni) in situ to afford the active sites for the growth of MWNTs.
