Designing functionalized gold surfaces and nanostructures for Laser Desorption Ionisation Mass Spectrometry

• Functionalized gold surfaces characterized by means of parallel angle-resolved XPS.
• AuNPs as matrix in LDI-MS analysis of low molecular weight biomolecules.
• Functionalized AuNPs to increase LDI performance by introducing a proton donor agent.

The present work is aimed at developing gold nanostructures functionalized with antenna systems to exploit the synergistic nanostructure/antenna desorption-ionization efficiency. A potential Matrix-Assisted Laser Desorption Ionisation (MALDI) organic matrix has been modified introducing specific functional groups or molecular linker and used as a capping agent for gold nanostructures.In particular, conjugated naphthyl-thio-derivative, i.e. 4-mercaptonaphthalene-1,8-dicarboxylic acid, was synthesized and characterized by means of nuclear magnetic resonance, UV–visible and X-ray photoelectron spectroscopies. Afterwards, the thio-derivative was used as covalent surface modifier for flat gold surfaces and nanostructured gold films. These surfaces were thoroughly characterized by means of parallel angle-resolved X-ray photoelectron spectroscopy to obtain quantitative information about elemental composition, chemical speciation, and in-depth distribution of the target chemical functional groups. Finally the compound was preliminarily tested as a non-conventional matrix in Laser Desorption Ionisation Mass Spectrometry (LDI-MS) analysis of low molecular weight biomolecules in order to assess its capability of acting as the antenna system and proton donor after covalent bonding to gold nanomaterials.