We demonstrate the in situ identi cation of crack cocaine and cocaine•HC l by using a ber-optic Raman probe and a portable Raman spectrograph. The Raman spectru m of freebase cocaine (crack) is obtained in just seconds without any sample preparation, and differs signi cantly from that of cocaine•HCl. We also show that the Raman spectra of these drugs are easily distinguishable from comm on cutting agents and impurities such as benzocaine and lidocaine. Another advantage of using Raman spectroscop y is that the drugs can be identi ed while contained in transparent containers, such as clear plastic evidence containers that are used to store drug evidence and to maintain chain of custody. W e also demonstrate the in situ Raman identi cation of drugs separated by thinlayer chrom atography. We discuss the utility of surface-enhanced Raman spectroscopy (SERS) in toxicological drug screen ing and present prelim inary SERS data for cocaine in solution using colloidal silver. We believe this to be the rst published SERS spectru m of freebase cocaine.

Nanosecond and femtosecond laser pulses were combined in an orthogonal preablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS) configuration. Even without full optimization of interpulse alignment, ablation focus, large signal, signal-to-noise ratio, and signal-to-background ratio enhancements were observed for both copper and aluminum targets. Despite the preliminary nature of this study, these results have significant implications in the attempt to explain the sources of dual-pulse LIBS enhancements.

In this paper, we report the first time-resolved laser-induced plasma images acquired using a liquid crystal tunable filter (LCTF). We also compare the use of LCTFs and acousto-optic tunable filters (AOTFs) for time-resolved plasma imaging applications in terms of resolution, out-of-band rejection, and image quality. Application of tunable filter technologies to plasma imaging is unlike other spectroscopic imaging methods because of the intense and spectrally broad background generated by a laser-induced plasma. High quality images of the distribution of atomic emission within a laser-induced plasma can be achieved using both AOTFs and LCTFs. However, additional filters are needed for rejection of wavelengths outside the tuning ranges of the devices. Both devices exhibited superior resolution in the lower working range of the filters (∼500 nm) with the LCTF exhibiting superior spectral resolution to the AOTF.

(J.C. Carter). AbstractWe demonstrate the feasibility of using Drop-on-Demand microjet printing technology for fabricating imaging sensors by reproducibly printing an array of photopolymerizable sensing elements, containing a pH sensitive indicator, on the surface of an optical fiber image guide. The reproducibility of the microjet printing process is excellent for microdot (i.e. micron-sized polymer) sensor diameter (92.2±2.2 microns), height (35.0±1.0 microns), and roundness (0.00072 ± 0.00023). pH sensors were evaluated in terms of pH sensing ability (≤2% sensor variation), response time, and hysteresis using a custom fluorescence imaging system. In addition, the microjet technique has distinct advantages over other fabrication methods, which are discussed in detail.

The use of a commercially available filtered fiber-optic Raman probe is discussed for the in situ identification of illicit drugs. This probe is also shown to be useful for remote Raman measurements in a collimated beam geometry. Fiber-optic Raman imaging is discussed using single small-diameter image guides and also image guides with attached imaging GRIN lenses. Finally, a demonstration of remote Raman imaging is presented using a simple modification of the same commercially available Raman probe that was used for illicit drug measurements.

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A simple Raman multipass capillary cell (MCC) is described that gives 12- to 30-fold signal enhancements for non-absorbing gases. The cell is made by coating the inside of 2-mm inner diameter silica capillary tubes with silver. The device is very small and suitable for remote and in situ Raman measurements with optical fibers. Application of the MCC is similar to previously described liquid core waveguides but, unlike the latter devices, the MCC is generally more applicable to a wide range of non-absorbing gases.

We report the first demonstration of surface-enhanced Raman spectroscopy (SERS) detection of para-mercapto benzoic acid (pMBA) and surface-enhanced resonance Raman spectroscopy (SERRS) detection of brilliant cresyl blue (BCB) and cresyl violet perchlorate (CVP) with continuous-wave excitation from a stand-off distance of 15 meters. We further report the first stand-off SERRS detection of BCB and CVP at that same distance in the presence of ambient fluorescent and incandescent/blackbody background light. These preliminary results suggest that it is possible to detect sub-nanomole amounts of material at reasonable distances with eye-safe laser powers using stand-off SERRS and serve as proof-of-concept highlighting the potential extension of stand-off Raman spectroscopy to include SERS and SERRS for remote, eye-safe chemical detection, analysis, and imaging in the presence of ambient background light.