Fuel fraud: Succumbs to SERS system

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  • Published: Feb 3, 2014
  • Channels: Raman
thumbnail image: Fuel fraud: Succumbs to SERS system

Silvery stability

SERS could protect garage owners and drivers from fuel fraud. Photo by David Bradley

The details of a patented, stable silver nano-colloid material for use in surface-enhanced Raman spectroscopy (SERS) have been reported by researchers from the University of Lincoln, UK. The system has already demonstrated its utility in portable instrumentation for the identification of fuel fraud.

Lincoln's Peter White and colleagues in the University’s forensic laboratories originally patented the colloidal silver in 2007 and it was at the time acknowledged as the first such stable and reproducible silver material. The team monitored batches for a year to ensure that they continued to meet the demands required of a commercial SERS, such as acceptable shelf-life, good batch-to-batch reproducibility, high enhancement factor in the SERS and to be available at a commercially acceptable price. Details of this system and its potential in other areas of chemical analysis and medical diagnostics are reported by the team in the Journal of Raman Spectroscopy. The team can produce particles with a mean diameter of 20 nanometres and a narrow size distribution of just 10 to 30 nm by reduction of silver nitrate with hydroxylamine phosphate to give a negatively charged phosphate surface on the silver particles. "This is an ultrafast room temperature reaction and with controlled rapid addition and dispersion of reagents," the team says. Characterisation was undertaken using ultraviolet-visible spectroscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, particle size analysis and SERS analyses itself.

Big boost

"I saw the potential for Raman spectroscopy in forensic science and published and patented a number of novel applications including the development of SERS active markers more than 12 years ago," White explains. However, one of the requisite systems was the stable silver colloidal system for commercial applications. "To resolve this problem I knew we had to change the charge of the colloid surface for it to remain stable and in 2007 we finally had our Eureka moment. Up until this point nobody had been able to produce a silver colloid that was stable enough for commercial use. It was a first for the UK and was a definitive piece of research." The system gives a 10-100 million fold enhancement in Raman laser spectroscopy when testing.

Fighting fuel fraud

White points out that governments commonly tax or subsidise fuel products to generate revenues, or stimulate their economies, and both of these practices are subject to fraud. Fuel marking has been shown to be effective in controlling illegal activity. He developed fuel fraud application based on the SERS with DeCipher Pte Ltd, which now uses this technology for measuring markers in fuel to identify and control malpractice and uncover fuel smugglers. The system is operated on a global scale. The SERS instruments used are portable, give high specificity and sensitivity for fuel markers and the analysis is quick, clear and decisive.

Related Links

J Raman Spectrosc, 2014, 45, 32-40: "Preparation and characterisation of a stable silver colloid for SER(R)S spectroscopy"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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