Gold Nanoparticle-deposited Porous Silicon as Target to Enhance Laser Desorption/Ionization of Molecules

The diversity of silicon types and porous silicon structures brought many challenges to desorption/ionization on silicon(DIOS) (matrix-free mass spectroscopy) such as poor repeatability/reproducibility in data and short shelf-life of the sample target. The porous silicon layer deposited with gold nanoparticles was studied in this work as a sample target to enhance the laser desorption/lonization(LDI) of polyethylene glycol(PEG) and two peptides (oxytocin and angiomax). Passivation of the surface Si-H species by gold nanoparticles increases the shelf-life of the target. The morphologies of porous silicon before and after deposition of gold nanoparticles were examined by field-emission scanning electron microscopy (FE-SEM). The elemental composition of surface species was analyzed by Xray energy dispersive spectroscopy (EDS). Effect of the depogition time on the quantity of gold nanoparticles and also on the signal enhancement was investigated. The desorption/ionization enhancement of molecules may be due to the integration of porous silicon and gold nanoparticles with unique optical and physical properties. This type of sample target combines the advantages of both DIOS and gold nanoparticles.