摘要
采用混酸（HNO3/H2SO4）化学氧化裁剪法制得S-MWNTs,当样品经过0.1μm的微孔滤膜过滤后,收集滤液得到US-MWNTs,长度约为50 nm.对MWNTs、S-MWNTs和US-MWNTs样品进行荧光特性研究,结果表明S-MWNTs和US-MWNTs都能够产生荧光.S-MWNTs在-500 nm处出现发射峰,最佳激发波长在-310 nm处;而US-MWNTs的发射峰出现蓝移到-460 nm处,并且在相同浓度的情况下其峰的强度远大于S-MWNTs,这可能是MWNTs经过氧化裁剪后其电学性质发生显著的改变所致.由于MWNTs变短导致它的最低空轨道和最高占有轨道之间的能隙增大,使得其捕获激发光的能量增强;同时MWNTs表面的羧酸基团的相对含量也会增大,分散性更好,这样它就可有效的导走光激发生成的电子,减少电子与空穴的复合,光子的利用效率增高,因而荧光现象也随之增强.
S-MWNTs were prepared by thick HNO3/H2SO4 chemical oxidation cutting, when it was filtrated through 0.1 μm teflon filters, the US-MWNTs were obtained from the filtrate. The fluorescent spectra of different MWNTs （raw MWNTs, S-MWNTs and US-MWNTs） in aqueous solution were investigated, the results showed that the S- MWNTs and US-MWNTs could emit the fluorescences the broad emission peak of the S-MWNTs appears at 500 nm and the optimal excitation wavelength centers at 310 nm. However, an interesting feature for these US-MWNTs is. that the intensity of emission peak is enhanced and the peak is slightly blue shifted to 460 nm compared with the S- MWNTs. These results might ascribe that the electronic properties of the MWNTs would famous change through the chemical oxidation cutting, the shortening of the MWNTs would cause the energy bandgap between lowest unoccupied molecular orbital and highest occupied molecular orbital increases, and make US-MWNTs trap more excitation energy. Moreover, the more chemical oxidation cutting of carbon naotubes, the better dispersion and carboxyl-functionalized US-MWNTs. These could lead to the reduction of the e/h＋ recombination and the increase of the photo efficiency, and thus the more intense fluorescence emissions.
出处
《华中师范大学学报（自然科学版）》
CAS
CSCD
2007年第3期398-402,共5页
Journal of Central China Normal University：Natural Sciences
基金
国防部基础研究项目(A1420060185)
信阳师范学院青年骨干教师资助计划(2006).
关键词
化学氧化
超短管
荧光光谱
缺陷
chemical oxidation
US-MWNTs
fluorescence spectra
defect
