Nanoparticle TiO₂ films prepared by pulsed laser deposition: Laser desorption and cationization of model adsorbates

Titanium dioxide is a low-cost photocatalytic material in the chemical industry. This work provides extended insights into the use of TiO₂ nanostructures in laser-assisted laser desorption ionization (LDI) of small peptides and synthetic polymers. The investigation evaluates the interfacial morphologies in the nanoscale that enhance the LDI efficiency in nanoparticle-assembled TiO₂ films prepared by femtosecond and nanosecond pulsed laser deposition (PLD) at different laser wavelengths. It is shown that PLD provides robust substrates yielding LDI pulse energy thresholds and signal/noise ratios in the mass spectra for detection of cationized adducts that can be comparable to those obtained with TiO₂ nanoparticle suspensions and with conventional organic matrices. The best LDI performance is found for nanosecond PLD crystalline substrates of the anatase polymorph and for femtosecond PLD amorphous substrates, with average nanoparticle sizes in both cases in the range of 25-55 nm.