High laser-fluence deposition of organic materials in water ice matrices by “MAPLE”

Matrix assisted pulsed laser evaporation (MAPLE) is a deposition technique for organic material. Water ice was used as a matrix for the biotechnologically important guest material, polyethylene glycol (PEG), for concentrations from 0.5 to 4 wt.%. The target was irradiated with 6 ns laser pulses at 355 nm at a fluence of 2.5-12 J/cm2. Even at this high fluence, Fourier transform infrared spectroscopy (FTIR) indicates a chemical structure of the deposit close to that of the un-irradiated PEG. Matrix assisted laser desorption and ionization (MALDI) and gel permeation chromatography (GPC) show that the mass distribution of the deposited PEG is similar to that of the starting material. Optical pictures of the films show particle structures of PEG of a size up to 5-10 μm. The deposition rate measured with a quartz crystal microbalance is typically of the order of 1 ng/(cm2 shot).