含氮石墨烯量子点的制备及其光学性质研究

doi:10.15541/jim20160227

摘要/Abstract

摘要：

采用水热法一步合成了含氮石墨烯量子点(NGQDs), 通过原子力显微镜(AFM)、透射电镜(TEM)、X射线光电子能谱(XPS)等对NGQDs的形貌和组成进行表征, 并进一步通过紫外-可见光谱(UV-Vis)、荧光光谱(PL)等手段研究了NGQDs的光学性质。AFM和TEM分析结果表明, NGQDs尺寸约为8.9 nm、厚度为0.6 ~2.0 nm (即1~3个碳原子层)。XPS分析结果表明NGQDs中氮含量约为17%, 且氮元素主要以“吡咯N”形式存在。光谱学实验表明, NGQDs的激发光谱与吸收光谱基本一致, 且其发射光谱与激发波长之间不存在依赖关系。此外, NGQDs的量子产率为~18%, 并随着含氮量的增加而增加, 且其荧光寿命衰变曲线可以被拟合成很好的双指数衰变曲线(τ₁=2.93 ns, τ₂=9.00 ns), 表明NGQDs有两种发色源, 即边缘富有含氧官能团的sp²碳簇和含氮五元环-吡咯环。

关键词: 石墨烯量子点, 水热法, 氮掺杂, 光学性质

Abstract:

Graphene quantum dots containing nitrogen (NGQDs) were synthesized by the hydrothermal method. AFM, TEM and XPS were employed to investigate the morphology and composition of NGQDs, and their optical properties were studied by UV-Vis and photoluminescent (PL) spectroscopy. AFM and TEM images showed that NGQDs were about 8.9 nm in size and 0.6-2.0 nm in thickness (1-3 layers graphene). The result of XPS showed that nitrogen content in NGQDs was ~17% and nitrogen existed mainly in the form of "pyrrolic N". Spectroscopy experiments indicated that excitation spectra of NGQDs were similar to their absorption spectra, and their emission spectra were excitation-independent. In addition, quantum yield of NGQDs was calculated to be ~18%, increasing with the content of nitrogen in NGQDs increase. Furthermore, the lifetime decay curve was well fitted to a double exponential decay curve (τ₁=2.93 ns, τ₂=9.00 ns), which indicates that there are two feature chromophores in NGQDs. The chromophores are sp² clusters with oxygen groups and pyrrolic ring.

Key words: graphene quantum dots, hydrothermal method, nitrogen doped, optical properties

中图分类号:

TQ174

张东梅, 田磊, 郭慧林. 含氮石墨烯量子点的制备及其光学性质研究[J]. 无机材料学报, 2016, 31(10): 1123-1128.

ZHANG Dong-Mei, TIAN Lei, GUO Hui-Lin. Preparation and Optical Properties of Graphene Quantum Dots Containing Nitrogen[J]. Journal of Inorganic Materials, 2016, 31(10): 1123-1128.

图/表 11

表1 NGQDs的元素分析结果和量子产率

Table 1 Elements analysis and quantum yield of NGQDs

Sample	C/wt%	N/wt%	H/wt%	Quantum yield (QY)
NGQDs-1	32.90	13.41	6.318	8.50%
NGQDs-2	32.28	15.87	6.469	12.59%
NGQDs-3	35.27	17.29	6.270	18.11%
NGQDs-4	36.52	17.76	6.133	18.24%

图1 NGQDs-3的AFM形貌及高度分布(a)和TEM照片(b)

Fig. 1 AFM image of NGQDs-3 and the height profiles along the line (a) and corresponding TEM image (b)

图2 NGQDs-3的XPS全谱图(a)、C1s谱图(b)和N1s谱图(c)

Fig. 2 XPS survey spectrum (a), C1s spectra (b) and N 1s spectra of NGQDs-3

图3 NGQDs-3傅里叶红外光谱图

Fig. 3 FT-IR spectrum of NGQDs-3

图4 NGQDs的紫外可见光谱图

Fig. 4 UV-Vis spectra of NGQDs

图5 NGQDs 的激发光谱图(a)和发射光谱图(b)

Fig. 5 Excitation spectra (a) and emmision spectra (b) of NGQDs

图6 NGQDs-3在不同激发波长下的发射光谱图

Fig. 6 Emmision spectra of NGQDs-3 at different excitation wavelengths

图7 不同pH时的NGQDs-3荧光光谱图(a)和荧光强度(b)

Fig. 7 PL spectra and intensities of NGQDs-3 at different pH

图8 NGQDs-3 在365 nm紫外灯照射1 h前后(a)和放置一个月前后(b)的荧光光谱图

Fig. 8 PL spectra of NGQDs-3 before and after irradiating in 365 nm UV lamp for 1 h (a) and before and after placing for 1 month (b)

图9 NGQDs-3的荧光寿命衰变曲线

Fig. 9 PL decay curves of NGQDs-3

图10 NGQDs的荧光发光机制示意图

Fig. 10 Schematic diagram of photoluminescence of NGQDs

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