Laser-based micro-spectrochemical analysis in forensic and security applications

Prof. José R. Almirall

Department of Chemistry and Biochemistry and International Forensic Research Institute

Florida International University, Miami FL USA

www.ifri.fiu.edu

Analytical Chemistry with LIBS

sample is ablated by pulsed laser beam with sufficient energy to excite/ionize the material = breakdown thresholdtypically peak power energies of 10-100 mJ/pulse

are focused to an intensity of 1010-1012 W/cm2

Nd:YAG laser (1064 nm, 8 ns)

spectrometer

Laser-Induced Breakdown

Spectroscopy

Courtesy of the Army Research Laboratory

Advantages of LIBS for Materials Detection and Identification

• Real-time, true standoff detection capability– conventional nanosecond LIBS has been demonstrated at

distances >100 meters, residue explosives at 50 meters• No sample preparation required, single-shot analysis of residues has

been demonstrated• High Sensitivity (ng), High Specificity (typically >95% True Positives,

<5% False Positives, when using advanced chemometrics)• Elemental Fingerprinting (broadband high resolution spectrometer

capable of detecting most elements on periodic table in each laser shot) • LIBS provides universal materials detection/characterization• LIBS works on various states of unknown materials- solids/residues,

liquids, aerosols, vapors.

Courtesy of the Army Research Laboratory

LIBS Sensor Suite & Applications

LIBS Probe for Humanitarian Demining

THREATDETECTED

Standoff detection

MP-LIBS

Underwater

Navy Ships- 300 m standoff

Suitcase LIBS “Lab-in-Field”

Spectrometer

Remote/Fiber-Optic LIBS

Robo-LIBSOptics

Data Processing

0

500

1000

1500

2000

2500

3000

200 400 600 800

Wavelength (nm)

Inte

nsity

(a.u

.)

Laser

Courtesy of the Army Research Laboratory

Typical LIBS Spectra of Explosives

Single-shot double pulse standoff (30 m) spectra of explosive residues on aluminum

Courtesy of the Army Research Laboratory

Explosive-containing Mixtures, 25 meters, double pulse

Threshold

Courtesy of the Army Research Laboratory

Maryland Attempted Bank Robbery

Glass is evidence of association – LIBS Analysis

8

Association between fragments in a bank robbery case –confirmed by LA-ICP-MS

266 nm laser

CSI, Las Vegas episode: “What’s eating Gil Grisham”

Acknowledgements• Almirall research group

Dr. Benjamin NaesTatiana TrejosErica CahoonSarah JantziEmily SchenkAlejandra Flores (IUPUI)

• National Institute of Justice for funding LIBS research (2005-IJ-CX-K069)

•

• Army Research Office - STIR grant for LIBS research

• Dr. Andrzej Miziolek of the Army Research Laboratory, APG

• American Chemical Society and Optical Society of America