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Analysis of the atomic structure of CdS magic-size clusters by X-ray absorption spectroscopy

DOI: 10.1039/D0NR05186A DOI Help

Authors: Ying Liu (Diamond Light Source) , Lei Tan (Queen Mary University of London) , Giannantonio Cibin (Diamond Light Source) , Diego Gianolio (Diamond Light Source) , Shuo Han (Sichuan University) , Kui Yu (Sichuan University) , Martin T. Dove (Queen Mary University of London; Wuhan University of Technology; Sichuan University) , Andrei Sapelkin (Queen Mary University of London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nanoscale , VOL 34

State: Published (Approved)
Published: September 2020

Open Access Open Access

Abstract: Magic-size clusters are ultra-small colloidal semiconductor systems that are intensively studied due to their monodisperse nature and sharp UV-vis absorption peak compared with regular quantum dots. However, the small size of such clusters (<2 nm), and the large surface-to-bulk ratio significantly limit characterisation techniques that can be utilised. Here we demonstrate how a combination of EXAFS and XANES analyses can be used to obtain information about sample stoichiometry and cluster symmetry. Investigating two types of clusters that show sharp UV-vis absorption peaks at 311 nm and 322 nm, we found that both samples possess approximately 2[thin space (1/6-em)]:[thin space (1/6-em)]1 Cd[thin space (1/6-em)]:[thin space (1/6-em)]S ratio and have similar nearest-neighbour structural arrangements. However, both samples demonstrate a significant departure from the tetrahedral structural arrangement, with an average bond angle determined to be around 106.1° showing a bi-fold bond angle distribution. Our results suggest that both samples are quasi-isomers – their core structures have identical chemical compositions, but different atomic arrangements with distinct bond angle distributions.

Subject Areas: Materials, Chemistry

Instruments: B18-Core EXAFS