Ion-Desorption Efficiency and Internal-Energy Transfer in Surface- Assisted Laser Desorption/Ionization: More Implication(s) for the Thermal-Driven and Phase-Transition-Driven Desorption Process

KM Ng and SL Chau and HW Tang and XG Wei and KC Lau and F Ye and AMC Ng, JOURNAL OF PHYSICAL CHEMISTRY C, 119, 23708-23720 (2015).

DOI: 10.1021/acs.jpcc.5b05957

Fundamental factors governing the ion-desorption efficiency and extent of internal-energy transfer to a chemical thermometer, benzylpyridinium ion (BP(+)), generated in the surface-assisted laser desorption/ionization (SALDI) process, were systematically investigated using noble metal nanopartides (NPs), including AuNPs, AgNPs, PdNPs, and PtNPs, as substrates, with an average particle size of 1.7-3.1 nm in diameter. In the correlation of ion-desorption efficiency and internal- energy transfer with physicochemical properties of the NPs, laser- induced heating of the NPs, which are dependent on their photoabsorption efficiencies, was found to be a key factor in governing the ion- desorption efficiency and the extent of internal-energy transfer. This suggested that the thermal-driven desorption played a significant role in the ion-desorption process. In addition, a stronger binding affinity of BP(+) to the surface of the NPs could hinder its desorption from the NPs, and this could be another factor in determining the ion- desorption efficiency. Moreover, metal NPs with lower melting points could also facilitate the ion-desorption process via the phase- transition process, which could lower the activation barrier (Delta G(#)) of the ion-desorption process by increasing the entropic change (Delta S-#). The study reveals that high photoabsorption efficiency, weak binding interaction with analyte molecule, and low melting point could be critical for the design of SALDI substrates with efficient ion desorption.

Return to Publications page