tailieunhanh - báo cáo hóa học: " Surface charges and optical characteristic of colloidal cubic SiC nanocrystals"

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: Surface charges and optical characteristic of colloidal cubic SiC nanocrystals | Li et al. Nanoscale Research Letters 2011 6 454 http content 6 1 454 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Surface charges and optical characteristic of colloidal cubic SiC nanocrystals Yong Li 1 2 4 Changxin Chen3 Jiang-Tao Li1 Yun Yang1 and Zhi-Ming Lin1 Abstract Colloidal cubic silicon carbide SiC nanocrystals with an average diameter of nm have been fabricated by anisotropic wet chemical etching of microsized cubic SiC powder. Fourier transform infrared spectra show that these cubic SiC nanocrystals contain carboxylic acid SiH CH and CHx groups. UV Vis absorption and photoluminescence PL spectroscopy clearly indicate that water and ethanol colloidal suspensions of the as-fabricated colloidal samples exhibit strong and above band gap blue and blue-green emissions. The cubic SiC nanocrystals show different surface charges in water and ethanol solutions due to the interaction of water molecules with polar Si-terminated surfaces of cubic SiC nanocrystals. The results explain the distinctive optical characteristics of colloidal cubic SiC nanocrystals in water and ethanol and reveal that quantum confinement and surface charges play a great role in determining the optical characteristics of colloidal cubic SiC nanocrystals. Keywords cubic SiC nanocrystals surface charges photoluminescence quantum confinement Introduction Silicon carbide SiC is an important wide band gap semiconductor with superior properties such as excellent thermal conductivity high breakdown field strength and excellent physical and chemical stability 1-4 . It has been found to have applications in many harsh conditions including high temperature high power and high frequency 5 For instance SiC has been commercially applied for optoelectronic devices such as photodiodes and light-emitting diodes which emit throughout the visible spectrum into ultraviolet 6 . Its peculiar electronic properties make it a promising material for .