tailieunhanh - báo cáo hóa học: " Intense ultraviolet emission from needle-like WO3 nanostructures synthesized by noncatalytic thermal evaporation"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Intense ultraviolet emission from needle-like WO3 nanostructures synthesized by noncatalytic thermal evaporation | Park et al. Nanoscale Research Letters 2011 6 451 http content 6 1 451 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Intense ultraviolet emission from needle-like WO3 nanostructures synthesized by noncatalytic thermal evaporation Sunghoon Park Hyunsu Kim Changhyun Jin and Chongmu Lee Abstract Photoluminescence measurements showed that needle-like tungsten oxide nanostructures synthesized at 590 C to 750 C by the thermal evaporation of WO3 nanopowders without the use of a catalyst had an intense nearultraviolet NUV emission band that was different from that of the tungsten oxide nanostructures obtained in other temperature ranges. The intense NUV emission might be due to the localized states associated with oxygen vacancies and surface states. Background Tungsten oxide is of particular interest owing to its outstanding electrochromic optochromic and gas chromic properties 1-3 which make it a promising candidate for applications in smart windows wide-angle high-contrast displays gas and temperature sensors 4-6 . Tungsten oxide in bulk form has been studied extensively over the past few decades. Nevertheless there are relatively few reports on tungsten oxide nanostructures. In particular little is known about the luminescence properties of tungsten oxide nanostructures possibly because tungsten oxide is an indirect band gap semiconductor with low-emission efficiency. Two strong emissions from tungsten oxide nanostructures near-ultraviolet NUV emission and blue emission have been reported 7-12 . Nevertheless there is still some controversy regarding the origins of the two emissions. Niederberger et al. 7 suggested that the blue emission from WO3 nanoparticles in an ethanol solution was due to a band-to-band transition. Luo et al. 8 also reported that the NUV and blue emissions from the WO3 - x nanowire network were due to the state of oxygen vacancies and a band-to-band transition respectively. On the other hand .