Diroll Benjamin T, Schaller Richard D
Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL 60615, USA.
Nanoscale. 2019 Apr 25;11(17):8204-8209. doi: 10.1039/c9nr01473j.
Ligand-to-nanocrystal heating and subsequent cooling to the environmental medium is investigated with infrared pump, electronic probe (IPEP) spectroscopy. Compared to solid films, solvated nanocrystals show faster ligand-to-nanocrystal heat equilibration (c. 11 ps versus c. 17 ps). Solvated nanocrystals also display more cooling of the hot ligand-nanocrystal complex on the experimentally measured time-scale, emphasizing the thermally insulating nature of semiconductor nanocrystal solids. Although heating transfer rates among solvents are all between 150 ps and 330 ps, cooling of the nanocrystal-ligand complex is slower, on average, in chlorinated solvents (c. 315 ps) compared to deuterated hydrocarbon solvents (c. 215 ps). Differences between chlorinated and hydrocarbon solvents show the importance of matching the vibrational energies of the solvent and the ligands for increasing the rate of heat transfer. Increases in the cooling time for poorer hydrocarbon solvents, in which nanocrystals aggregated, such as toluene, compared to better solvents, like methylcyclohexane, indicate that penetration of solvent into the ligand layer facilitates improved heat transfer to the matrix.
利用红外泵浦 - 电子探针（IPEP）光谱研究了配体到纳米晶体的加热以及随后向环境介质的冷却过程。与固体薄膜相比，溶剂化纳米晶体显示出更快的配体到纳米晶体的热平衡（约11皮秒对约17皮秒）。在实验测量的时间尺度上，溶剂化纳米晶体还显示出热配体 - 纳米晶体复合物更多的冷却，这突出了半导体纳米晶体固体的隔热性质。尽管溶剂之间的热传递速率都在150皮秒到330皮秒之间，但与氘代烃类溶剂（约215皮秒）相比，纳米晶体 - 配体复合物在氯化溶剂中的冷却平均较慢（约315皮秒）。氯化溶剂和烃类溶剂之间的差异表明，匹配溶剂和配体的振动能量对于提高热传递速率很重要。与较好的溶剂（如甲基环己烷）相比，在较差的烃类溶剂（如甲苯，其中纳米晶体发生聚集）中冷却时间增加，这表明溶剂渗透到配体层中有助于改善向基质的热传递。
