Anecdotal evidence from forensic practitioners and studies conducted under controlled conditions have indicated that the reaction between 1,2-indanedione and the amino acids present in latent fingermark deposits is highly susceptible to ambient humidity. The addition of catalytic amounts of zinc chloride to the 1,2-indanedione working solution – usually in the order of 1:25 to 1:4 molar ratio (indanedione:zinc) – significantly improves the colour and luminescence of fingermarks treated under dry conditions but appears to have a negligible effect on fingermarks treated in humid environments. The results presented in this paper confirmed that zinc(II) ions added to the 1,2-indanedione working solution act as a Lewis acid catalyst, stabilising a key intermediate during a rate-limiting hydrolysis step. Furthermore, studying the reaction using a chromatography-grade cellulose substrate method previously reported confirmed that cellulose substrates play a major role in facilitating the indanedione-amino acid reaction by acting as a surface catalyst in the early stages of the reaction and by directing the formation of the desired luminescent product (Joullié’s Pink).
Spindler, X., Hofstetter, O., McDonagh, A., Roux, C., & Lennard, C. (2011). Enhancement of Latent Fingermarks on Non-Porous Surfaces Using Anti-L-Amino Acid Antibodies Conjugated to Gold Nanoparticles. Chemical Communications, 47(19), 5602-5604. https://doi.org/10.1039/c0cc05748g