1. What is the best way to prepare samples for the Raman analysis, the sample in question is a colloidal solution. So far I have come across two different methods to do so, (a) To drop cast a sample on a slide and leave it overnight or for a while to dry, (b) To drop cast the sample on a slide and apply heating to dry it either by using an oven or a hot air blower.
2. Regarding the substrate choice what are the protocols that should be followed.
3. Same questions for SERS sample preparation also.
These are a lot of questions and I will be very grateful for your answers.
Thank you.
Dear Bibek,
1. I recommend depositing the sample on a glass slide and waiting for it to cure overnight. Depending on the nature of your colloidal solution, heating could change some of its properties. I also would consider any surface treatments of the slide that may be necessary for ensuring good adhesion.
2. For the substrate, glass slides are usually preferred because, unlike Si for instance, the glass has no defined powerful peaks. you may wish to perform a calibration run on the glass before hand to cancel out noise later.
3. The procedure should be much the same for SERS, but I would pay special attention to ensuring that the glass slide is clean and free of defects.
I hope this helps!
Nathan Zavanelli Thank you for your response, Sir,
I had tried using both the glass slides and silicon substrate, I observed some peaks in the case of the silicon substrate and in glass as well, in the range of 1200 to 1500, on checking I found that the peak in case of the glass substrate was because of the glass slide but I also observed a broad peak in the same range when silicon substrate was used, the broadness and nature of the peak were little different, I have used 785 nm for the excitation. Silicon shows a peak around 520, so could it mean that the peak that I am observing in the range of 1200 to 1500 in the case of the silicon substrate is because of my sample.
For SERS, do I need to dip the sample in analyte solution, or simply dropping the analyte solution on top of the sample substrate will do?
Sr. Bibek, no he trabajado espectroscopia Raman. Creo que ya tienes una buena orientación por profesor Zabanilli. Mi trabajo fundamental ha estado dirigido a la enseñanza de la Química y dentro de ella a métodos de análisis químico pero no para Químicos, sino para éstudiantes de Agronomía, cuyos requerimientos en profundidad y habilidades no son tan grandes como los que tu desarrolla. No obstante aprendo también de la participación en estos intercambios.
You are welcome Bibek Singh
I would recommend running another Raman analysis with just the substrates and comparing this to the observed spectra with the solution. The peaks you are observing could also be due to impurities or the solution itself if they are not logically explained by the colloid.
For SERS, I would first consider the required magnification, especially if the particles are being detected in normal Raman. I have usually seen SERS for ultrasensitive applications, like detecting biomolecules and similar low concentration particles. If SERS is necessary, then the solution can be similarly deposited on top of the nanomaterial reflective surface. There are lots of ways to optimize this process and the SERS surface depending on the application to obtain very high gains, but it is somewhat application specific. The solution should wet well on the surface and be allowed to dry.
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