Application of HPLC and MALDI-TOF MS for studying as-synthesized ligand-protected gold nanoclusters products

Yan Zhang, Shaomin Shuang*, Chuan Dong, Chung Keung Lo, Man Chin Paau, Martin M F CHOI

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

75 Citations (Scopus)

Abstract

Samples of polydisperse gold nanoclusters (AuNCs) protected with monolayers of N-acetyl-L-cysteine (NAC) have been chromatographically separated by a C18 column (4.6 mm × 250 mm) using a gradient elution program with a mobile phase of methanol (MeOH)/water containing tetrabutylammonium fluoride (Bu 4N+F-) and sodium chloride. The effects of Bu4N+F- and MeOH on the separation have been investigated in detail. In conjunction with absorbance-based, fluorescence, and electrochemical detectors, the elution order of these water-soluble AuNCs is confirmed according to their core size in an ascending order. The onset oxidation potential closely follows the core size of AuNC. The separated fractions from high-performance liquid chromatography (HPLC) were collected and analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry to determine the number of Au atoms in the fractions. The sizes of AuNCs in some selected HPLC fractions were also assessed by transmission electron microscopy and high-resolution transmission electron microscopy. Photoluminescence spectra of the fractions show that the luminescent shift in the visible/near-infrared region does not follow with the core size of AuNC. More importantly, the proposed HPLC methodology has been successfully applied to analyze various polydisperse AuNC products synthesized from different gold-to-ligand mole ratios (Au/ NAC) and reaction temperatures. The results confirm that larger Au/NAC and higher temperature will produce larger core size AuNCs products with narrower dispersity. In addition, AuNC samples obtained from various synthesis reaction times were analyzed by our HPLC methodology, demonstrating that the reaction's behavior follows the nucleation-growth- disintegration process.

Original languageEnglish
Pages (from-to)1676-1685
Number of pages10
JournalAnalytical Chemistry
Volume81
Issue number4
DOIs
Publication statusPublished - 15 Feb 2009

Scopus Subject Areas

  • Analytical Chemistry

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