Below is a list of our frequently asked questions related to SERS, SERS substrates, storage, treatment, signal enhancement and more. If your question is not answered here, please do not hesitate to contact us.
A Silmeco SERS substrate, called a SERStrate, is essentially a silicon wafer coated with a metal like gold or silver (or a custom metal of choice). The silicon wafer is made up of a special structure – ag/au coated nano-pillars – which facilitates molecular sensing (Raman scattering). The SERS substrates can be used to detect extremely small amounts of various chemicals, hormones, explosives, subcellular structures and more.
As a rule of thumb Ag (silver) offers the best signal enhancement. The enhancement factor is typically 10x – 100x larger compared to Au (gold).
Generally no. Doing so will cause the substrate nanopillars to lean and produce unwanted results.
Only one side of the SERS substrate is suitable for the measuring. The side is coated with either gold or silver (or a custom coating on special requests). You can identify the correct active side by looking at the colors of either side of the substrate. SERS substrates with gold coating have a “brownish/bronze/reddish” color tone. Silver SERS substrates have a light/beige tone.
Do not touch the active side of the substrate with your fingers, scratch it or use the substrates in a dusty environment – doing so will produce unreliable results.
Gold SERS substrates have a “brownish/bronze/reddish” color tone. Silver substrates have a light/beige color tone. If the silver substrates exhibits a very dark color they have most likely become oxidized.
The Ag and Au SERS substrates can be immersed totally in any liquid.
No – the SERS substrates do not contain any additional layers or film. The SERS substrates can be used without any washing, sonication etc. Treating the SERS substrates prior to analyte deposition can produce unreliable results so this is not recommended.
One can try spin coating material on the SERS substrate and then evaporating the solvent. This is not an usual way of doing it, and will require some experimentation to get satisfactory results. The reasons are that (i) the spin coating would create unusual “hot spots” (depending on spin coating parameters), and (ii) depending on how high is the temperature (>200C is dangerous to nanostructures), solvent evaporation would affect silver/gold nanostructures. Therefore, this kind of material/analyte deposition requires experimentation but it might work.
Opened (Ag) 3-4 weeks before oxidation
Un-opened (Ag): 1+ year.
Our substrates (both Ag and Au) are cleanroom-packaged with nitrogen gas. Ag substrates can be stored for up to 6-9 months in this atmosphere. Over time, the Ag substrates would slowly oxidize and only a minor performance drop at internal laboratory testing has been detected. The substrates are still perfectly usable even after 1 year. Unless you want to study something that binds with Ag and you do not want the surfaces to become silver oxide, oxidation is not found to pose a major problem. Once a package is opened, Ag substrates would oxidize within 3-4 weeks, but still provide good results according to internally conducted tests.
The SERS substrates should be stored at room temperature or below. The bag in which the SERS substrates are shipped is filled with an inert gas. Once you open the package we recommend that you store the SERStrates in a vacuum/inert (argon / nitrogen) atmosphere, preferably in an exicator – however this is not a requirement for the SERS substrates to produce good results (please refer to the previous question for more info).
Typically we see customers use water, ethanol and isopropanol solvents.
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