Insights into thiram fungicide: A comparative study of solution and solid phases through Raman, DCDR, and SERS measurements and DFT simulations
Abstract
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.