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

Abstract

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.

Recent advances in linear and nonlinear Raman spectroscopy. Part VII

“…Baclig and co‐workers reported low‐resolution Raman spectroscopy over a wide spectral range with a single‐diffraction order arrayed‐waveguide grating . Huang, Farquharson, and co‐workers described the measurement of the SERS of melamine and other molecules using a 1550‐nm (retina‐safe) laser …”

Achieving optimal SERS through enhanced experimental design

“…The selection of laser excitation wavelength has a significant impact on experimental capabilities, and whilst typically visible excitation is used (e.g. 488, 514.5, 532 and 633 nm), SERS has been reported from the near UV (325 nm), the near IR (785 and 830 nm) as well as recently at even longer wavelengths such as 1064, 1280 and 1550 nm . This selection process is often determined by a need to compromise between minimising sample fluorescence and maximising scattering efficiencies (especially if resonance is also used).…”

The on‐site/remote Raman analysis with mobile instruments: a review of drawbacks and success in cultural heritage studies and other associated fields

“…At present, most of the Table‐top Raman spectrometers equipped with solid state (air‐cooled) laser source(s) may be moved from room‐to‐room . In many cases, under the supervision of a Raman expert, 1 h or less is necessary to prepare/assemble the instrument(s).…”

“…The spray of metal nanoparticles (surface enhancement Raman spectroscopy promoter) tested at the laboratory after sampling could be a solution to improve the potential of on‐site Raman measurements. Alternative routes are the use of infrared excitation (miniaturised 1064‐nm Fourier transform infrared Raman instruments preventing the excitation of fluorescence or retina‐safe 1550‐nm excitation) or blue excitation (laser surface cleaning). Careful data processing is mandatory, and the increasing use of chemometric techniques able to extract reliable data from ‘bad’ spectrum is expected.…”