Porphyrins and phthalocyanines as chemical visualisation reagents for latent fingerprint development

Abstract

The focus of the research presented in this thesis was the investigation of porphyrins and phthalocyanines as potential reagents for the development of latent fingerprints. Porphyrins and phthalocyanines are structurally related compounds which have many features in common, including the ability to substitute a wide variety of metal ions into the core of the macrocyclic ring, along with the ability to attach a vast range of functional groups to the periphery of the macrocyclic ring and to the metal centre. These compounds also exhibit diverse absorption and emission spectra, which are sensitive to the metal ions and functional groups incorporated. Porphyrins are the most abundant colouring matter found in nature, and phthalocyanines are used extensively as colouring agents. These qualities indicate that such compounds are good candidates for fingerprint reagents.

A porphyrin and several phthalocyanines were synthesised, characterised, and appraised as potential fingerprint reagents. All compounds examined showed reactivity towards one or more fingerprint components. In particular it was found that dihydroxytetraphenylporphyrinatotin(IV) was capable of developing prints via reaction with water and non-water soluble fingerprint components. This compound may have application for the development of fingerprints on substrates such as thermal paper. It may also be a useful prior treatment to Physical Developer, a currently used technique for the development of fingerprints that have been exposed to water. Another compound, copper(II) tetrachlorosulfonylphthalocyanine was found to develop prints by reaction with water soluble fingerprint components. This compound may be of use on substrates where currently available methods give low contrasting fingerprints. Overall it was determined that porphyrins and phthalocyanines show genuine promise as fingerprint reagents and that further research in this area is clearly warranted.