Single- and Multi-Transducer Arrays Employing Nanoparticle Interface Layers as Vapor Detectors for a Microfabricated Gas Chromatograph.

This body of research focuses on improving microsensor arrays used as detectors in Si-microfabricated gas chromatographs (µGC) for the determination of volatile organic compounds (VOCs). By means of such improvements, µGC technology should find wider application in homeland security, disease diagnosis, and environmental monitoring. The microsensors considered here all employ thiolate-monolayer-protected gold nanoparticles (MPN) as vapor sorptive interface layers. The central hypothesis is that by altering the MPN ligand, core size, and/or the underlying transducer, the diversity of responses to VOCs provided by microsensor arrays with MPN interfaces can be improved. The first study evaluated a single transducer (ST) array of MPN-coated chemiresistors (CR) as a µGC detector for three semi-volatile markers of the explosive 2,4,6-trinitrotoluene in the presence of alkane interferences of similar volatility. The effects of flow rate and temperature on chromatographic resolution, sensitivity, and limits of detection (LOD) were assessed. Under optimized conditions, a complete analysis required 95%). These types of sensor arrays can enhance the vapor discrimination of sorption-based detectors utilized in µGC technology, making the analysis of complex VOC mixtures possible.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111430/1/lkamos_1.pd

Recent Developments in the Field of Explosive Trace Detection

Explosive trace detection (ETD) technologies play a vital role in maintaining national security. ETD remains an active research area with many analytical techniques in operational use. This review details the latest advances in animal olfactory, ion mobility spectrometry (IMS), and Raman and colorimetric detection methods. Developments in optical, biological, electrochemical, mass, and thermal sensors are also covered in addition to the use of nanomaterials technology. Commercially available systems are presented as examples of current detection capabilities and as benchmarks for improvement. Attention is also drawn to recent collaborative projects involving government, academia, and industry to highlight the emergence of multimodal screening approaches and applications. The objective of the review is to provide a comprehensive overview of ETD by highlighting challenges in ETD and providing an understanding of the principles, advantages, and limitations of each technology and relating this to current systems

Nanoporous Silica Preconcentrator for Vapor-Phase DMNB, a Detection Taggant for Explosives.

The detection of trace amounts of explosives in the vapor phase is of great importance. Preconcentration of the analyte is a useful technique to lower the detection limit of existing sensors. A nanoporous silica (pSiO2) substrate was evaluated as a preconcentrator for gas-phase 2,3-dimethyl-2,3-dinitrobutane (DMNB), a volatile detection taggant added by law to plastic explosives. After collection in pSiO2, the DMNB vapor was thermally desorbed at 70 °C into a gas chromatography-mass spectrometry sorbent tube. This was analyzed for the total mass of DMNB collected in pSiO2. The loading time and loading temperature of pSiO2 were varied systematically between 15 and 60 min and 5-20 °C, respectively. The preconcentrator's performance was compared to that of a nonporous substrate of the same material as a control. The collection efficiency of pSiO2 was calculated as approximately 20% of the total DMNB that passed over it in 30 min, at a concentration of 0.5 ppm in N2 carrier gas. It had enhancement factors compared to the nonporous substrate of 12 and 16 for 0.5 and 4.1 ppm DMNB, respectively, under the same conditions. No advantage was found with cooling pSiO2 below room temperature during the loading phase, which removes any need for a cooling system to aid preconcentration. The low desorption temperature of 70 °C is an advantage over other preconcentration systems, although a higher temperature could decrease the desorption time.Innovative Research Call in Explosives and Weapons Detection 2016, Cambridge Trus