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Structural Dynamics of Short Ligands on the Surface of ZnSe Semiconductor Nanocrystals
Hongxing Hao1, Jingwen Ai1, Chenxiao Shi1
1Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710119, China.
Abstract:
ZnSe semiconductor nanocrystals (NCs) with a size comparable to their Bohr radius are synthesized, and the native capping agents with long hydrocarbon tails are replaced with short thiocyanate (SCN) ligands through a ligand exchange method. The structural dynamics of SCN ligands on the surface of ZnSe NCs in solution is investigated by ultrafast infrared spectroscopy. Vibrational population relaxation of SCN ligands is accelerated due to the specific interaction with the positively charged sites on the surface of NCs. The orientational anisotropy of the bound SCN ligands decayed at a rate much faster than that in the control solution containing Zn2+ cations. From the wobbling-in-the-cone model analysis, we found that the SCN ligand undergoes wobbling orientational diffusion with a relatively large cone semiangle on the surface of ZnSe NCs, and the overall orientational diffusion of bound SCN is found to be strongly dependent on the size of ZnSe NCs.
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