Synthesis of ultrasmall platinum nanoparticles and structural relaxation

Chao Liu; Gao Li; Douglas R Kauffman; Guangsheng Pang; Rongchao Jin

doi:10.1016/j.jcis.2014.02.022

Synthesis of ultrasmall platinum nanoparticles and structural relaxation

J Colloid Interface Sci. 2014 Jun 1:423:123-8. doi: 10.1016/j.jcis.2014.02.022. Epub 2014 Feb 28.

Authors

Chao Liu¹, Gao Li², Douglas R Kauffman³, Guangsheng Pang⁴, Rongchao Jin⁵

Affiliations

¹ Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave, Pittsburgh, PA 15213, USA; State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, 2699 Qianjin Street, Changchun, Jilin 130012, China. Electronic address: anna.liuchao@gmail.com.
² Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave, Pittsburgh, PA 15213, USA. Electronic address: gaoli@andrew.cmu.edu.
³ National Energy Technology Laboratory (NETL), United States Department of Energy, Pittsburgh, PA 15236, USA. Electronic address: Douglas.Kauffman@CONTR.NETL.DOE.GOV.
⁴ State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, 2699 Qianjin Street, Changchun, Jilin 130012, China. Electronic address: panggs@jlu.edu.cn.
⁵ Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave, Pittsburgh, PA 15213, USA. Electronic address: rongchao@andrew.cmu.edu.

PMID: 24703677
DOI: 10.1016/j.jcis.2014.02.022

Abstract

We report the synthesis of ligand-protected, ultrasmall Pt nanoparticles of ∼1 nm size via a one-phase wet chemical method. Using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), we determined the mass of the nanoparticles to be ∼8 kDa. Characterization of the Pt nanoparticles was further carried out by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), optical absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS). Interestingly, we observed a large structural relaxation in the 8kDa nanoparticles (i.e. lattice parameter elongation by +10%) compared to bulk platinum. XPS analysis revealed a positive shift of Pt 4f core level energy by approximately +1 eV compared with bulk Pt, indicating charge transfer from Pt to S atom of the thiolate ligand on the particle. Compared to bulk Pt, the 5d band of Pt nanoparticles is narrower and shifts to higher binding energy. Overall, the ∼1 nm ultrasmall Pt nanoparticles exhibit quite distinct differences in electronic and structural properties compared to their larger counterparts and bulk Pt.

Keywords: 8kDa; Nanoclusters; Pt; Thiolate; Ultrasmall nanoparticles.