Metallization of Porous Silicon Nanodisks for Matrix-Free Laser Desorption/Ionization Mass Spectrometry

X. Zhou, H-J Wu, F. Zhang, X. Liu
The Methodist Hospital Research Institute, US

Keywords: porous silicon, metallization, matrix-free laser desorption/ionization

Summary:

Monodisperse pSiNDs are fabricated by the combination of photolithography and electrochemical etching of the crystalline silicon. The pSiNDs are then metallized by electroless plating of noble metal nanoparticles in the pores of the pSiNDs. We have successfully applied this methods to fabricate Au, Ag, and Pt plated pSiNDs. UV-Vis spectroscopy was utilized to monitor the metallization process of pSiNDs. The different levels of surface plasmon resonance (SPR) indicate the size and density of metal nanocrystals in pSiNDs. Hence, the absorption spectra provide the direct information of the metallization level. In addition, scanning electron microcopy (SEM) and transmission electron microscopy (TEM) were used to measure the metal nanocrystals in the pSiNDs. The size, morphology and distribution of the metal nanocrystals can be controlled by tuning the concentration, temperature and reaction time, as well as the selection of capping agents. Using polyvinylpyrrolidone (PVP) as the capping agent and the second reducing agent, 10-20nm Au nanocrystals were uniformly deposited in pSiNDs. The metallized pSiNDs were used for matrix-free laser desorption/ionization mass spectrometry. The metallized pSiNDs strongly enhanced the laser desorption/ionization. Comparing to non-metallized pSiNDs, the metallized pSiNDs resulted in higher resolution spectra.