Surface-enhanced Raman spectra of melamine and other chemicals using a 1550 nm (retina-safe) laser


Stuart Farquharson, Real-Time Analyzers, Inc., 362 Industrial Park Rd, #8, Middletown, CT, USA.



Many trace chemical analyses are being transitioned from the lab to the field, among which is surface-enhanced Raman spectroscopy. Although initial portable Raman analyzers primarily employ 785 nm laser excitation, recent studies suggest longer wavelengths, with an appropriate surface-enhanced Raman-active substrate, may provide equal sensitivity. Furthermore, 1550 nm excitation may provide added safety for the user, in that permanent retina damage does not occur. Here, we show that a reasonable enhancement factor can be obtained for melamine using 1550 nm laser excitation that is nearly equivalent to those obtained using 785 and 1064 nm laser excitation. We also demonstrate that a number of other chemicals of interest can be measured by 1550 nm surface-enhanced Raman scattering, albeit only modest sensitivity is achieved because of instrument limitations, not enhancement factors. Copyright © 2011 John Wiley & Sons, Ltd.