Molecular imaging of banknote and questioned document using solvent-free gold nanoparticle-assisted laser desorption/ionization imaging mass spectrometry.
Direct chemical analysis and molecular imaging of questioned documents in a non/minimal-destructive manner is important in forensic science. Here, we demonstrate that solvent-free gold-nanoparticle-assisted laser desorption/ionization mass spectrometry is a sensitive and minimal destructive method for direct detection and imaging of ink and visible and/or fluorescent dyes printed on banknotes or written on questioned documents. Argon ion sputtering of a gold foil allows homogeneous coating of a thin layer of gold nanoparticles on banknotes and checks in a dry state without delocalizing spatial distributions of the analytes. Upon N(2) laser irradiation of the gold nanoparticle-coated banknotes or checks, abundant ions are desorbed and detected. Recording the spatial distributions of the ions can reveal the molecular images of visible and fluorescent ink printed on banknotes and determine the printing order of different ink which may be useful in differentiating real banknotes from fakes. The method can also be applied to identify forged parts in questioned documents, such as number/writing alteration on a check, by tracing different writing patterns that come from different pens.
Department of Chemistry and Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, People's Republic of China.
Ho-Wai
HW
Tang
Melody Yee-Man
MY
Wong
Sharon Lai-Fung
SL
Chan
Chi-Ming
CM
Che
Kwan-Ming
KM
Ng
D004396:Coloring Agents / Q000737:chemistry; D004282:Documentation; D044707:Forensic Sciences / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D006236:Handwriting; D007281:Ink; D007834:Lasers; D013058:Mass Spectrometry / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry*
D004396:Coloring Agents; D006046:Gold