image: The precursor cluster ions were guided into laser dissociation chamber. A single-shot laser irradiation with a pulse length of 5 ns was applied for the dissociation of ligand-protected cluster precursors and the generation of the complex metal nanoclusters. The complex fragment clusters were cooled down within the dissociation chamber (20 mTorr N2) for about 100 ms and then transferred to the orbitrap analyzer for high-throughput characterization before the arrive of next laser shot (with about 300 ms interval between adjacent shots). view more
Credit: ©Science China Press
This study is led by Dr. Fangjun Wang, Dr. Chunlei Xiao, and Dr. Gao Li from Dalian Institute of Chemical Physics, the Chinese Academy of Sciences. Fangjun Wang and Chunlei Xiao cooperated to build a 193-nm ArF excimer laser-high resolution mass spectrometry system in lab in 2017. They wanted to perform intact protein dissociation for both protein sequence and structure elucidation.
At the same time, Dr. Gao Li prepared a series of atomically precise monolayer-protected metal clusters for catalysis. Gao Li was sought to characterize these ligand-protected clusters by using electrospray mass spectrometry.
When Fangjun Wang and his assistant Dr. Zheyi Liu analyzed the ligand-protected clusters in their electrospray mass spectrometer, by chance, they also tried to irradiate the clusters with a single pulse (5 ns) of 193 nm laser. Surprisingly, they observed almost all the peripheral ligands were stripped away by the laser shot, and the inside metal core was completely dissociated to form numbers of fragment nanoclusters with consecutive sizes.
These exciting results encouraged them to synthesize more ligand-protected metal clusters, then, fragmentate them by 193 nm laser irradiation, and detect the fragment clusters in Orbitrap MS detector. When Au144 precursor cluster was utilized, they observed the generation of multiply charged (2+ and 3+) gold nanoclusters, which has rarely been reported by conventional metal-cluster sources.
By introducing gas reagent such as CO and C2H2 into the mass spectrometer, they further investigate the chemical adsorption activity of more than 400 types of fragment nanoclusters simultaneously. Interestingly, the adsorption activity is step-wisely decreased from Au152+ to Au1402+, and several crucial transition points were clearly observed.
“The 193 nm laser dissociation-high resolution mass spectrometry provides a powerful way for the in-situ generation and global activity profiling of complex metal nanoclusters. Just like the omics studies in life science, and this may also be defined as Metal Nanocluster Omics and may greatly promote the discovery and application of active metal nanoclusters for wide applications”, Fangjun Wang says.
See the article:
In-situ generation and global property profiling of metal nanoclusters by ultraviolet laser dissociation-mass spectrometry
https://doi.org/10.1007/s11426-022-1267-5
Journal
Science China Chemistry