Highly Sensitive Filter Paper Substrate for SERS Trace Explosives Detection

We report on a novel and extremely low-cost surface-enhanced Raman spectroscopy (SERS) substrate fabricated depositing gold nanoparticles on common lab filter paper using thermal inkjet technology. The paper-based substrate combines all advantages of other plasmonic structures fabricated by more elaborate techniques with the dynamic flexibility given by the inherent nature of the paper for an efficient sample collection, robustness, and stability. We describe the fabrication, characterization, and SERS activity of our substrate using 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and 1,3,5-trinitrobenzene as analytes. The paper-based SERS substrates presented a high sensitivity and excellent reproducibility for analytes employed, demonstrating a direct application in forensic science and homeland security. 1. Introduction In last decade, the potential exposure of civilian and military populations to hazardous materials (chemical, biological, and highly energetic) has attracted attention of authorities, because it has become an increasingly likely scenario. The rapid and accurate detection and identification of possible threats is crucial to neutralize potentially threatening situations. In order to detect and identify these hazards, the ideal technology should exhibit high sensitivity and reproducibility in analyte detection, require little or no sample preparation, and be robust, easy to use, and portable for field operations [1]. A series of analytical methodologies, principally chromatographic and spectrometric techniques, are routinely carried out in specialized laboratories using standard methods to assess chemical and biological hazards. These usually require several steps including sampling, handling, preparation, and analysis, which make the entire process time-consuming and difficult to apply in the field. Raman spectroscopy is a well-suited technique for the identification, characterization, and quantification of unknown targets [2–5]. Raman spectroscopy is particularly advantageous because the technique does not present interferences from water (which is the universal solvent), requires minor or no sample preparation, and produces vibrational information useful as unique spectral signature of the analyte of interest. In addition, the miniaturization of Raman equipment has added robustness to the technique, which has made possible its use in different environments outside the laboratory confinement. However, development of Raman spectroscopy as analytical technique for trace detection of hazardous materials has not been possible, mostly due to the