The development of SERS substrates for chemical detection of specific analytes requires appropriate selection of plasmonic metal and the surface where it is deposited.Here we deposited Ag nanoplates on three substrates: i) conventional SiO 2 /Si wafer, ii) stainless steel mesh and iii) graphite foils. The SERS enhancement of the signal was studied for Rhodamine 6G (R6G) as common liquid phase probe molecule. We conducted a comprehensive study with =532, 633 and 785 nm on all the substrates.The best substrate was investigated, at the optimum laser 785 nm, for gas phase detection of dimethyl methyl phosphonate (DMMP), simulant of the G-series nerve agents, at a concentration of 2.5 ppmV (14 mg/m 3 ). The spectral fingerprint was clearly observed; with variations on the relative intensities of SERS Raman bands compared to bulk DMMP in liquid phase reflects the DMMP-Ag interactions. These interactions were simulated by Density Functional Theory (DFT) calculations and the simulated spectra matched with the experimental one. Finally, we were detected the characteristics DMMP fingerprint with hand-held portable equipment. These results open the way for the application of SERS technique on real scenarios where robust, light-weight, miniaturized and simple to use and cost-effective tools are required by first responders.

No abstract

Inactivation of Listeria monocytogenes and Escherichia coli by citric (10-150 g L −1 ) and lactic (1-60 mL L −1 ) acids at different temperatures (4, 20, 40 • C) has been investigated. Bactericidal effect of both acids was dependent on time and temperature of exposure and acid concentration. Survival curves of L. monocytogenes treated by lactic acid were concave downward and those treated by citric acid were linear. On the other hand, survival curves of E. coli treated by both organic acids were concave upward. Shape of survival curves depended on the type of acid but not on the treatment temperature. A mathematical model based on the Weibull distribution accurately described the kinetics of inactivation of both microorganisms by both acids. This model allowed quantification and comparison of the acid resistance of L. monocytogenes and E. coli. Lactic acid was more effective than citric acid and E. coli was more sensitive to both acids than L. monocytogenes.

Inactivation of Yersinia enterocolitica by chlorine (0.6 to 20 ppm) was investigated in distilled water and in tryptic soy broth (TSB, 0.015%) at different temperatures (4, 20, and 40 degrees C). In distilled water, chlorine inactivation of Y. enterocolitica was enhanced by increasing the temperature from 4 to 20 degrees C, and survival curves were described by a model that assumed first-order kinetics followed by tailing in which the microbial concentration remained constant. The presence of TSB increased chlorine resistance of Y. enterocolitica, and survival curves were concave downward. These survival curves were described by a model based on the Weibull distribution. Chlorine decay in distilled water was independent of temperature and of the initial concentration of available chlorine and was modeled by first-order reaction kinetics. Chlorine decay in TSB was independent of the initial chlorine concentration but depended on the treatment temperature and was modeled by the addition of two first-order decay equations. The increased resistance of Y. enterocolitica to chlorine in TSB was not due only to the chlorine demand by the TSB components. These components protected Y. enterocolitica cells from the antimicrobial effect of chlorine.