Klarite® FAQ’s

Common FAQ's about Klarite substrates are detailed below. If your question is not included, please contact info@renishawdiagnostics.com with your query.

How do I use the Klarite substrates?

Most experiments are carried out using a drop drying technique, which involves dropping (pipetting) small volumes (~1-20 μl) of analyte solutions onto the surface. In this scenario the solvent should evaporate, naturally depositing the analyte onto the surface. The surface is then read using a Raman spectrometer. Alternatively, if the molecule of interest forms a strong bond with the Klarite surface, then the molecule may be attached simply by immersing the Klarite chip in a beaker containing the analyte solution (note: this is only suitable if the molecule-surface bond is very strong, such as in the case of a thiol). Molecules in the vapour/gaseous phase may also be deposited via spontaneous diffusion.In this process the optimal adsorption conditions depend on the experimental conditions and on the physical characteristics of the vapour/molecules.

A more detailed guide to Klarite use is available:

Slide mounted Klarite - Instructions for Use

Unmounted Klarite - Instructions for Use

What laser excitation wavelengths can be used with Klarite?

Klarite substrates are designed to work best at laser excitations from 633 - 785 nm and above. Since the substrates are gold coated, light absorbance will increase at lower wavelengths and no SERS will be observed.

What type of molecules can be analysed using Klarite?

Small molecules (mw < 500 gmol^-1) with high numbers of functional groups make the best analytes, since these give a high number of sharp intense peaks. As molecules get bigger the spectra tend to get slightly poorer and noisier – such as in the case of proteins and polymers. However, SERS spectra of such analytes can be very usefully interpreted to give structural and conformational information. As analytes get bigger, to the size of whole cells, SERS spectra may still be observed but these will have fewer intense peaks and more noise. However, some very successful work has been done using Klarite on the detection of whole cell organisms such as spores and bacterial cells.

Can the substrates be cleaned / reused?

The substrates are designed to be disposable. We have run several tests on cleaning but, being very sensitive devices, removing any traces of contaminants without affecting the gold surface is extremely challenging. We therefore strongly recommend that the substrates are not re-used.

Is it possible to put more than one sample on the substrates?

Yes, but it will depend on your application or test (e.g. solvent used). For small volumes (~1 µl) of aqueous solutions 5 or more different drops can be deposited on a single 4 mm x 4 mm active area.

What can I expect to see using SERS?

The peaks in a spectrum are specific to particular bonding stretches and vibrations in the molecule of interest. Thus, if required, spectra can be interpreted to gain structural and compositional information on a sample. However, in general SERS is used as an excellent fingerprinting technology. The presence, absence and intensity of peaks specific to any analyte can be observed indicating the presence of the molecule in question.

Why do I only see a small increase in Raman signal when using Klarite?

There could be one of several reasons or a combination of reasons why you only see a small increase in Raman signal, the most common of which are listed below.

• The concentration of your analyte may be too high, causing you to see bulk Raman signals rather then SERS; dilute your analyte solution.
• The microscope objective lens you are using is too high; we recommend 10x or 20x
• You are not properly focussed on the sample; ensure correctly focussed at substrate surface.

What is the shelf life of Klarite substrates? How should they be stored?

Due to the active nature of the surface, current recommended shelf life is in excess of 3 months from shipment when enclosed in the un-opened foil protective packaging at room temperature. The shelf life may be increased in excess of two years provided the product is properly stored.We recommended storing the substrates at freezer temperature (~-15º C or ~5º F).

What effect can temperature have on the substrates?

Klarite substrates should not be exposed to temperatures above 70-80 °C. If working in this temperature window, exposure time should be limited to 20 min. Failure to do this will result in irreversible damage to the surface, and loss of SERS activity. This is of particular importance during potential evaporation steps during sample deposition.

What is the availability/lead time of the Klarite SERS substrates?

We monitor stock carefully and aim to fulfill all orders within 3 working days.