No abstract

Raman spectroscopy is one of the most used biodetection techniques. However, its usability is hampered in the case of low concentrated substances because of the weak intensity of the Raman signal. To overcome this limitation, the use of drop coating deposition Raman spectroscopy (DCDRS), in which the liquid samples are allowed to dry into well-defined patterns where the non-volatile solutes are highly concentrated, is appropriate. This significantly improves the Raman sensitivity when compared to the conventional Raman signal from solution/suspension. As DCDRS performance strongly depends on the wetting properties of substrates, we demonstrate here that the smooth hydrophobic plasma polymerized fluorocarbon films prepared by magnetron sputtering (contact angle 108°) are well-suited for the DCDRS detection of liposomes. Furthermore, it was proved that even better improvement of the Raman signal might be achieved if the plasma polymer surfaces are roughened. In this case, 100% higher intensities of Raman signal are observed in comparison with smooth fluorocarbon films. As it is shown, this effect, which has no influence on the profile of Raman spectra, is connected with the increased hydrophobicity of nanostructured fluorocarbon films. This results in the formation of dried liposomal deposits with smaller diameters and higher preconcentration of liposomes.

Thiram, a widely known fungicide, has evinced a negative impact on the environment and human health that led to the banning of its use in plant protection products on all commodities in the European Union. Therefore, there is a need for monitoring possible illicit use, which requires sensitive and accurate detection methods. In this study, the behavior of thiram in different phases was investigated in order to better understand its properties. Raman spectra were obtained from thiram in the solid state as a crystalline powder, dissolved in different solvents, and from dried deposits using the drop coating deposition Raman (DCDR) method. The analyses of acquired Raman spectra revealed evidence of hydrogen bonding between thiram and chloroform in the solution phase. The reliability and sensitivity of DCDR measurements were also highlighted, with high‐quality spectra obtained from a dried pattern from droplet at a 40 μM concentration. Moreover, the study identified the most abundant conformer of intact (undegraded) thiram molecule and enabled reliable band assignment and vibrational analysis based on DFT simulations, providing a better understanding of the compound's properties. The results also suggested that thiram can be coordinated to silver in nanostructured SERS active substrates not only in the degraded form but also in the undegraded form. Overall, this study provides valuable insights into thiram's behavior and can be helpful in the further development of efficient and effective methods for its detection and analysis.