Metallic silver nanoparticles coated with titanium dioxide were synthesized via a simple route. The chemical
reduction of Ag+ to Ago was followed with the controlled polymerization of TiO2 to produce very small size and
narrow distribution of nanoparticles produced the desired TiO2/Ag colloidal suspensions. The prepared nanoparticles
were characterized by UV-VIS absorption and by Energy Dispersive X-ray Spectroscopy. The spectrum of the
suspension of normal Ag nanoparticles had a surface plasmon resonance peaked at 420 nm arising from particles
characteristic of Ag colloidal dispersions. Similar surface plasmon absorptions due to Ag nanoparticles were
observed for the suspension of Titania coated Ag nanoparticles, but at longer wavelength than for the suspension of
Ag nanoparticles. This absorption shift ( +15 to +20 nm) is caused by refractive index of Titania and suggests
coverage of Ag nanoparticles with Titania. TiO2/Ag colloids were used to measure Raman spectra in capillary tubes
at different excitation sources to observe the enhancement of the Raman signatures of solution of TNT and DNT at
different pH values. At pH = 10.3 TNT showed an increase of the NO2 stretching mode at the 1365 cm-1 in
comparison with the other pHs and the solution without colloids. In addition, the band ca. 1213 cm-1 and NO2 (1370
cm-1) band were shifted from their normal positions.
FTIR, Raman spectroscopy and Surface Enhanced Raman Scattering (SERS) requires a minimum of sample allows
fast identification of microorganisms. The use of this technique for characterizing the spectroscopic signatures of
these agents and their stimulants has recently gained considerable attention due to the fact that these techniques can
be easily adapted for standoff detection from considerable distances. The techniques also show high sensitivity and
selectivity and offer near real time detection duty cycles. This research focuses in laying the grounds for the
spectroscopic differentiation of Staphylococcus spp., Pseudomonas spp., Bacillus spp., Salmonella spp.,
Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae, and E. coli, together with identification of their
subspecies. In order to achieve the proponed objective, protocols to handle, cultivate and analyze the strains have
been developed. Spectroscopic similarities and marked differences have been found for Spontaneous or Normal
Raman spectra and for SERS using silver nanoparticles have been found. The use of principal component analysis
(PCA), discriminate factor analysis (DFA) and a cluster analysis were used to evaluate the efficacy of identifying
potential threat bacterial from their spectra collected on single bacteria. The DFA from the bacteria Raman spectra
show a little discrimination between the diverse bacterial species however the results obtained from the SERS
demonstrate to be high discrimination technique. The spectroscopic study will be extended to examine the spores
produced by selected strains since these are more prone to be used as Biological Warfare Agents due to their
increased mobility and possibility of airborne transport. Micro infrared spectroscopy as well as fiber coupled FTIR
will also be used as possible sensors of target compounds.
The majority of explosives found in antipersonnel and antitank landmines contain 2,4,6-trinitrotoluene (TNT).
Chemical sensing of landmines and Improvised Explosive Devices (IED) requires detecting the chemical
signatures of the explosive components in these devices. Nanotechnology is ideally suited to needs in microsensors
development by providing new materials and methods that can be employed for trace explosive
detection. This work is focused on modification of nano-scaled colloids of titanium dioxide (Titania: anatase,
rutile and brookite) and thin layer of the oxides as substrates for use in Enhanced Raman Scattering (ERS)
spectroscopy. Ultrafine particles have been generated by hydrothermally treating the sol-gel derived hydrous
oxides. ERS spectra of nanocrystalline anatase Titania samples prepared with different average sizes: 38 nm
(without acid), 24 nm (without acid) and 7 nm (with HCl). Bulk phase (commercial) and KBr were also used to
prepare mixtures with TNT to look for Enhanced Raman Effect of the nitroaromatic explosive on the test
surfaces. The studies clearly indicated that the anatase crystal size affects the enhancement of the TNT Raman
signal. This enhancement was highest for the samples with Titania average crystal size of 7 nm.
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