Analytical Chemistry, Physical Chemistry and Chemical Engineering Department, Faculty of Sciences, Alcalá University, E-28871 Alcalá de Henares, Madrid, Spain.
Soft Matter. 2018 Jul 25;14(29):6013-6023. doi: 10.1039/c8sm01017j.
The effects of surfactants of different nature (anionic, cationic and non-ionic) and chain length on the morphology, microstructure, thermal stability and electrical resistivity of liquid exfoliated graphene (G) were investigated. Microscopic (SEM and AFM) observations revealed that the thickness of G in the dispersions depended on the surfactant nature: non-ionic surfactants rendered the highest level of exfoliation, whilst dispersions in the cationic ones exhibited fully-covered thicker sheets; the flake thickness increased with increasing surfactant chain length. X-ray diffraction studies indicated an increased interlamellar G spacing with increasing surfactant content. Raman spectra showed an increase in the ID/IG ratio with decreasing G loading. Larger upshifts of the G, 2D and D + G bands were found with increasing surfactant concentration, particularly for dispersions in the cationic surfactants. For the same G/surfactant weight ratio, the electrical resistivity of the dispersions followed the order: cationic > non-ionic > anionic, consistent with the amount of surfactant adsorbed onto G calculated via TGA. It is demonstrated herein that the thermal and electrical properties of liquid exfoliated G can be tuned by varying the surfactant concentration, nature and chain length, which is of great importance for numerous applications like solar power harvesting, high-temperature devices and flexible nanoelectronics.
研究了不同性质（阴离子、阳离子和非离子）和链长的表面活性剂对液相剥离石墨烯（G）的形态、微观结构、热稳定性和电阻率的影响。微观（SEM 和 AFM）观察表明，分散体中 G 的厚度取决于表面活性剂的性质：非离子表面活性剂的剥离效果最高，而阳离子表面活性剂的分散体则呈现出完全覆盖的较厚片层；片层厚度随表面活性剂链长的增加而增加。X 射线衍射研究表明，随着表面活性剂含量的增加，层间 G 间距增加。拉曼光谱显示，随着 G 载量的降低，ID/IG 比值增加。随着表面活性剂浓度的增加，G、2D 和 D + G 带的较大蓝移被发现，尤其是在阳离子表面活性剂的分散体中。对于相同的 G/表面活性剂重量比，分散体的电阻率遵循以下顺序：阳离子>非离子>阴离子，这与通过 TGA 计算得出的吸附在 G 上的表面活性剂的量一致。本文证明了通过改变表面活性剂的浓度、性质和链长可以调节液相剥离 G 的热性能和电性能，这对于太阳能收集、高温器件和柔性纳米电子学等众多应用非常重要。
