Abstrakt
Drop coating deposition Raman (DCDR) method - as a special method of Raman spectroscopy - is based on evaporation of solvent from a small droplet of studied solution or suspension. Drying of a droplet with a pinned contact line on a hydrophobic substrate typically leads to the accumulation of dissolved material in the ring-shaped pattern [1].
By using a confocal Raman microspectrometer, the acquisition of Raman spectra of good quality from the pre-concentrated analyte ring is possible. Because of this, the DCDR technique enables to measure samples at very low initial concentrations and small volumes with high sensitivity in comparison with conventional Raman measurements.
It was shown that it is a very useful tool to detection of different biologically important molecules, e.g. lipids, as major components of biological membranes [2]. The shape of dried pattern, which is formed after the complete evaporation of the volative phase of the solution is influenced not only by the properties of the solution but it depends also on the substrate characteristics such as wettability and roughness that governs the droplet drying dynamics.
We focused our attention on liposome suspension dried on nanostructured hydrophobic substrates with different roughness. These substrates are prepared by a novel method that is based on the deposition of arrays of nanoparticles (Cu or Ag) fusing a gas aggregation source and subsequent overcoating of such prepared substrates by sputter-deposited thin C:F film.
The nanoroughness and with it connected wettability of produced coatings is controlled by the number of nanoparticles in the base layer including an option of a gradient surface coverage. It was shown that in the case of liposome suspension the nanoroughness leads to stronger preconcentration as well as to the reduction of the ring diameter, i.e. two parameters crucial for the DCDR measurements.