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Klarite substrates
are fully compatible with most Raman
spectrometers and are available mounted on standard 75mm microscope
slides for ease of handling and compatibility with microscope equipped
Raman systems.
An increasing range of miniature and portable Raman spectrometers
are also available and high quality spectra can be obtained from Klarite.
Optical fibre based sample probes can also be used to record spectra
including both single fibre and fibre bundle based systems.
When using a miniature or portable Raman system it is necessary to
have a mechanical mount to hold the substrate and adjust its position
at the laser focus of the system. D3 are developing a range
of substrate interfaces - please contact us for more information.
Spot size
The spot size and laser power incident on the substrate can vary significantly
between different Raman systems. Tests have shown high quality data
is obtained with a large range of spot sizes from 7mm to <5µm
in diameter. Very small spot sizes less than 5µm that result
from using >50x focusing objectives with microscopes systems should
be avoided as they reduce enhancement.
Laser power
Laser powers from <100µW to >300mW have been shown to
produce excellent Raman spectra with Klarite. Powers at the higher
end of this range are required for larger spot sizes and fibre coupled
systems. Higher powers are unlikely to damage the Klarite surface,
but care should be taken to damage the deposited sample. Due to the
high enhancement of the Klarite surface significantly lower powers
and lower integration times are normally required relative to those
used in regular none enhanced Raman.
Excitation wavelength
Surface enhanced Raman is a wavelength dependent phenomena and current
Klarite substrates are designed to work with red and near infrared
excitation lasers (633-800nm). Use at shorter wavelengths, e.g. 532nm
is possible, however gold absorption at this wavelength can cause
thermal signatures to dominate data unless very low powers of <1mW
are used. For longer wavelengths, e.g 1µm, standard Klarite
will only give a small signal enhancement. For optimum operation D3
recommends using Raman systems with either 785nm or 633nm excitation.
If you are interested in excitation at other wavelengths please contact
us as we have future products in development to expand this operating
range.
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