On the Colloidal Stability of Nitrogen-Rich Carbon Nanodots Aqueous Dispersions
On the Colloidal Stability of Nitrogen-Rich Carbon Nanodots Aqueous Dispersions
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DOI：
10.3390/c5040074
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发表时间：
2019-12-01
影响因子：
4.1
通讯作者：
Depeyrot, Jerome
中科院分区：
文献类型：
--
作者：
Fiuza, Thiago;Gomide, Guilherme;Depeyrot, Jerome
本研究报告了富氮碳纳米点（N-CD）水分散体的胶体稳定性。N-CD通过有机前体的热诱导分解合成，并且呈现由β-C3 N4晶体结构组成的内核，该内核被包含各种极性官能团的表面壳包围。通过XRD（X射线衍射）和TEM（透射电子显微镜）测量的组合分析来检查N-CD的尺寸和结构。傅里叶变换红外光谱（FTIR）实验表明，羧基和酰胺基团的存在下，N-CD表面。为了更好地理解胶体稳定性和表面电荷发展之间的关系，zetametry实验应用于N-CD分散体在不同的pH值和恒定的离子强度。随着分散介质的碱化，zeta电位的绝对值的增加与N-CD表面上的羧基的去质子化一致，这与在pH 12下长期胶体稳定性的宏观视觉观察一致。N-CDs表面电荷密度的饱和值通过电位-电导滴定法来评估。羧基相关的表面电荷之间的差异和一个由zeta电位测量点的存在下，除了羧基的N-CD表面上的氧化的氮官能团。这些新的结果揭示了静电排斥机制，允许显着的胶体稳定性的N-CD分散体。
The present survey reports on the colloidal stability of aqueous dispersions of nitrogen-rich carbon nanodots (N-CDs). The N-CDs were synthesized by thermally induced decomposition of organic precursors and present an inner core constituted of a beta-C3N4 crystalline structure surrounded by a surface shell containing a variety of polar functional groups. N-CDs size and structure were checked by combined analysis of XRD (X-ray Diffraction) and TEM (Transmission Electron Microscopy) measurements. FTIR (Fourier-Transform Infrared Spectroscopy) experiments revealed the presence of carboxyl and amide groups on N-CDs surface. Towards a better understanding of the relation between colloidal stability and surface charge development, zetametry experiments were applied in N-CDs dispersions at different pHs and constant ionic strength. The increase of the absolute values of zeta potential with the alkalinization of the dispersion medium is consistent with the deprotonation of carboxyl groups on N-CDs surface, which agrees with the macroscopic visual observations of long-term colloidal stability at pH 12. The saturation value of N-CDs surface charge density was evaluated by means of potentiometric-conductometric titrations. The difference between carboxyl-related surface charge and the one determined by zeta potential measurements point to the presence of oxidized nitrogen functionalities onto the N-CDs surface in addition to carboxyl groups. These novel results shed light on the electrostatic repulsion mechanism that allows for the remarkable colloidal stability of N-CDs dispersions.