Drop coating deposition Raman (DCDR) spectroscopy: fundamentals and potential applications

Raman spectroscopy has developed significantly since its discovery and has become an important analytical vibrational technique for investigating the sample's chemical and structural properties. Today, great emphasis is placed on detecting low-concentrated samples of small volumes, which is a problematic task considering the weak intensity of the Raman signal. To improve the sensitivity significantly, resonance Raman spectroscopy and surface-enhanced Raman spectroscopy were employed. However, they face certain limitations and cannot generally be applied to any molecule. Here, we focus on drop coating deposition Raman (DCDR) spectroscopy that offers a general solution. DCDR lies in a droplet deposition of a liquid sample on an ideally solvophobic substrate where the subsequent drying process results in a preconcentrated deposit. After focusing on the preconcentrated dried parts in the deposit under the Raman micro-spectrometer, this offers high-quality classical Raman spectra even from a low-concentrated sample. Besides the overview of the method, its potential and the applications to biomolecules, biologically significant molecules and contaminants will be discussed.