Probing ligand removal and ordering at quantum dot surfaces using vibrational sum frequency generation spectroscopy

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:537

Article

Watson, Brianna R.¹  Ma, Ying-Zhong²  Cahill, John F.²  Doughty, Benjamin²  Calhoun, Tessa R.¹ 

[1] Univ Tennessee, Dept Chem, Knoxville, TN 37996 USA

[2] Oak Ridge Natl Lab, Div Chem Sci, 1 Bethel Valley Rd, Oak Ridge, TN 37831 USA

关键词: Nonlinear spectroscopy;    Molecular ordering;    Vibrational spectroscopy;    Surface analysis;   

DOI  :  10.1016/j.jcis.2018.11.011

来源: Elsevier

【 摘 要 】

Hypothesis: Controlling nanomaterial interfaces for emerging technologies has driven the need to understand the molecular species located there; however, challenges arise using traditional analytical techniques to directly characterize the molecular structure and local environments of these interfacial species due to their low relative populations. We hypothesized that vibrational sum frequency generation (vSFG) spectroscopy would be uniquely sensitive to the chemical modification of nanoparticle surfaces that is obscured using traditional bulk sensitive methods. Experiments: Octadecylamine ligands were removed from model CdSe quantum dot surfaces using a common precipitation-resuspension procedure with polar protic and aprotic nonsolvents. Vibrational spectra of the ligands at the surface were collected with vSFG to directly probe the ligand ordering and coverage. Photoluminescence (PL), optical absorption, NMR, and mass spectrometry measurements were conducted for comparison. Findings: vSFG was found to be sensitive to subtle changes in ligand disorder over multiple precipitation-resuspension washes, and a limit to the number of ligand molecules removed from the surface and subsequent amount of disorder introduced to their packing was clearly observed. We also find that nonsolvents do not remain associated with the surface after washing. (C) 2018 Elsevier Inc. All rights reserved.

【 授权许可】

Free