I have managed to obtain Raman spectra for Aspirin by using the 785 nm laser line, but I have difficulties obtaining a SERS spectrum for Aspirin on the Au/TiO2/WO3 substrates. The following parameters were used for the SERS spectra: Aspirin concentration was 1 mM, 20-30 mg of Au/TiO2/WO3 substrate, 100 microliters of Aspirin were added onto the Au/TiO2/WO3 substrates, the suspension was vortexed, then 50 microliters Aspirin was dropwise added onto the microscope slide. After 10 minutes, the SERS spectra recording was attempted.
Does anyone know how we could obtain SERS spectra for Aspirin on Au/TiO2/WO3 substrates?
Székely István
Before obtaining SERS spectra, you need to check the existence of a plasmon resonance spectrum of the Au/TiO2/WO3 substrate in the visible part of the spectrum. The dispersion of Au nanoparticles gives such a spectrum, but Au/TiO2/WO3 is not yet clear from your question. A lot can be understood under the word substrate. SERS show nanoparticles with plasmons.
Székely István, it may be possible, though it is difficult to tell from your question where you might be running into issues.
- Aspirin needs to bind directly to the semiconductor materials to take advantage of charge transfer SERS, so depending on your synthesis surface ligands may block this interaction. Does the absorption spectrum of the substrate shift when Aspirin is added? If so, then this would suggest that the drug is binding to the surface.
- You can get enhancement from charge transfer and/or plasmon resonance here, but only if the excitation is resonant with these effects. Ideally, you can take advantage of both effects if their resonances overlap.
- It seems from your description that you are drying the material on a microscope slide. It may be the case that the system needs to be in a liquid environment for aspirin to be able to coordinate with the charge transfer sites on the nanoparticles.
Thank you for your answer Yuri Mirgorod!
The plasmon resonance of the Au/TiO2/WO3 composite was in the range of 540-560 nm. In this case the sample is a powder composed of TiO2 and WO3, and on their surface the gold nanoparticles (nanospheres) were deposited.