Sunlight-activated near-infrared phosphorescence as a viable means of latent fingermark visualisation

- Fingermarks were developed using a doped zinc gallogermanate powder.
- The fingerprint powder is both highly fluorescent and phosphorescent in the NIR.
- Excitation is induced from UV through to red wavelengths.
- Sunlight may be used to “charge” the powder for NIR phosphorescent activity.
- These optical properties facilitate complete background removal during fingerprint imaging.

The chromium-doped zinc gallogermanate, Zn3Ga2Ge2O10:0.5%Cr3+, was prepared and modified for use as a near-infrared (NIR) luminescent fingerprint dusting powder. The optical properties of this material are illustrated and have been shown to offer versatility and promise in terms of overcoming troublesome backgrounds during latent fingermark examination and imaging. The highly fluorescent NIR emission of the powder allows inherently fluorescent and patterned substrate backgrounds to be mitigated, whilst the phosphorescent nature of the material allows all conceivable background interference to be removed, whilst also constituting the first reported use of a NIR phosphor for latent fingermark enhancement and imaging.

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