Abstract:

Carbon quantum dots with uniform size distribution have broad application prospects in the fields of optoelectronic devices, ion detection, nano-sensors, biological imaging and catalyst's due to their good optoelectronic properties. An “ultrafiltration-nanofiltration” bi-membrane method was proposed for the separation and purification of carbon quantum dots (CQDs). The molecular weight cutoff (MWCO) of ceramic ultrafiltration (UF) and nanofiltration (NF) membranes was 2000 and 800 and the corresponding Stocks-Einstein sizes were 2.3 nm and 1.4 nm, respectively. The pure water flux of UF and NF membranes were 140 and 70 L·(m²·h)⁻¹, respectively. The effects of pH on the fluorescence intensity and particle size distribution of CQDs were studied. At pH=3, the carbon quantum dots were well dispersed and the fluorescence intensity is high. The ceramic UF membrane could effectively reject the large grained impurities. The average size of the CQDs in the permeate was about 2 nm with good dispersion and no agglomeration. Ceramic NF membrane played a great role in retention properties to CQDs. Small molecular impurities could be further removed in the concentration and washing process by using NF membrane. After bi-membrane treatment, the emission spectrum changed from multimodal to monomodal distribution, and the peak width narrowed. The luminous purity of CQDs was significantly improved.

Key words: membrane, nanofiltration, ultrafiltration, nanoparticles, carbon quantum dots, purification

摘要：

尺寸分布均一的碳量子点由于其良好的光学特性，在光电设备、离子检测、纳米传感器、生物成像和催化剂等领域具有广阔的应用前景。采用陶瓷膜“超滤-纳滤”双膜法，对微波合成的碳量子点进行分离和纯化。研究了pH对碳量子点料液荧光强度和粒径分布的影响。在pH=3时，碳量子点分散较好，荧光强度较高。陶瓷超滤膜可以有效截留碳量子点料液中的大颗粒杂质，渗透侧的碳量子点平均粒径约为2 nm，分散良好，无团聚现象。陶瓷纳滤膜对碳量子点具有良好的截留性能，在浓缩和水洗过程中可以进一步去除料液中的小分子杂质。经双膜法处理后，发射光谱由多峰分布变为单峰分布，且峰宽变窄，碳量子点的发光纯度得到了明显提高。

关键词: 膜, 纳滤, 超滤, 纳米颗粒, 碳量子点, 纯化