爆炸物中化学组成检测方案(激光拉曼光谱)

Forensics 03 Direct Raman Mapped Imagingof Explosive Materials Introduction Raman Microscopy has become anestablished tool in the analysis of surfaces andsolid phase particles. The latest automatedtechnology has enabled analysts to studycontaminants and surface structure with ease.Forensics csi(entistsand Ilaw enforcementagencies have a pparticular interest in theverification of the presence of explosives on asurface and to characterise the distribution ofindividual componentswithini anexplosivematerial. Peviously， destructive methods of analysissuch as chromatography and massspectroscopy and qualitative techniques suchas AFMhave afforded some information.However， these techniques either requiredestructive and lengthy extraction proceduresor provide little or no direct characterisation ofthe sample. In comparison， the Raman microscope canprovide non-destructive， in-situ， highly specificspectral and distribution information. We report here a brief study of a surfacecontaminated with an explosive containing twotypical components， RDX and PETN. Instrumentation The LabRam 1B confocal Raman microscopewasused to analyse and interrogate thesuspect surface. The LabRam is a compactand rugged single stage Raman spectrometersystem that incorporates integral microscope，CCD video camera and holographic notch filtertechnology. It was configured with the patentedLaser line scanning facility and an automatedmotorised XY scanning stage to enable a full2-D Raman map to be obtained. An internalHeNe laser and secondary 532 nm laser werealso included in the instrument although， forthis work only the HeNe laser was used. Dueto theunique optical performances insensitivity and real confocality， the LabRamwas able to build up a Raman mapped imageofthe explosivematerialwith aspatialresolution of around 1 pm. Figure 1. The Confocal LabRAM 1B AnalyticalRaman Microscope System from HORIBAJobin Yvon. Seen here with high and low resolution dualgrating option， Integral confocal microscope，CCD video camera， Internal HeNe laser andautomated motorised XY mapping stage. Experimental Digitisedwhite lighttvvideo images wereacquired on the LabRAM system to visuallyinterrogate the sample surface and identifypossible explosive contamination. 2-D Raman maps were set up to produce a fullanalysis of the defined area and obtainingcomplete Raman spectra from each micron ofthe surface. The Windows LabSpec softwarewasableto ffirstly determinespectralcharacteristics of the different components andthen produce a Raman image detailing thelocalisation of the active explosive componentsand the binder. Results The Digitised white light video image ofnagthe sample areato be analysedisshown in Figure 2. It can be seen clearlythat there is some contamination on thesurface. The box indicates the area thatwas defined for the 2-D Raman map.The size of the mapped area is 20 x 30um with a step size interval of 0.5um. Characteristic Sspectra for eachcomponentt offtthe explosive wereobtained (Figure 3). The v(C-H) stretch Raman bands in thespectral region 2800-3200 cm’wereused to produce a Raman image andillustrate the localisation of all of thesuspectmaterial， theexplosiveandbinder components. (Figure 2). The components RDX and PETN weremapped individually and superimposedtoo illustrate the：localisationn of thedifferent particles of eeaacchh explosivecomponent (Figure 4). The binder was then mapped to confirmthe distribution of tthe inert material.(Figure 4) Figure 3： Raman spectra for the differentcomponents in the explosive material. Figure 2. White light video image (left) ofcontaminated surface. The box indicates theareadefinedfortheRamanMapping.Associated Raman mapped image (right) fromthev(C-H) stretch Raman bands in the spectralregion 2800- 3200 cm'. Figure 4 ： Raman mapped image for the twoactive components red RDX and green PETN(left) and Raman mapped image for the inertbinder (right). Summary Fromi the：1resultss obtainedbyy theconfocal Raman mapping it is possibleto distinguish three main components intheeexplosivecontamination.Thesehave been confirmed as RDX， PETNand binder. It can be seen that there is a closepositional correlation between the whitelight image and the images generated byRaman mapping. The Ramann aanalysisfor this workk wasconducted at Instruments Jobin Yvon UK andthe applications laboratory of the Jobin YvonRaman Division， Lille， France. We are gratefulto Edouard Da Silva and Myriam Moreau atDilor and especiallyto DERAforthecollaboration， samples and advice inconducting this work. ORIBAExplore the future ORIBAExplore the future From the results obtained by the confocal Raman mapping it is possible to distinguish three main components in the explosive contamination. These have been confirmed as RDX, PETN and binder.It can be seen that there is a close positional correlation between the white light image and the images generated by Raman mapping.