The preparation of fluorescent fingerprinting powders using 8-hydroxyquinoline compounds and magnetite

Abstract

Fluorescent fingerprinting powders were prepared by using rotary evaporation to coat magnetite powder with varying amounts of either tris(8-hydroxyquinolinato)aluminium (Alq₃), tris(8-hydroxyquinolinato)gallium (Gaq₃), bis(8-hydroxyquinolinato)magnesium (Mgq₂) or bis(8-hydroxyquinolinato)zinc (Znq₂). The performance of each fingerprinting powder was tested on various surfaces under visible light and under UV excitation. The efficacy of powder application using a magnetic brush was compared to that of standard brushes. The effects of varying the particle sizes of the fingerprinting powders made with Alq₃ and Znq₂ were explored. The stability of each fluorescent compound under standard conditions was tested. The synthesis of sodium tetrakis(8-hydroxyquinolinato)boron (NaBq₄) was attempted twice, but failed both times. The product acquired was suspected to be Na₄(C₉H₆NO)₄(H₂O)₈ (Na₄q₄(H₂O)₈) instead. Crystals of Na₄q₄(H₂O)₈ were prepared using a modified literature method. The Na₄q₄(H₂O)₈ crystals and the products of the attempted syntheses were characterised by powder X-ray crystal diffraction, inductively coupled plasma mass spectrometry, electrospray ionisation mass spectrometry, nuclear magnetic resonance spectroscopy, UV-Vis absorption, and melting point measurements. Fingerprint powders were prepared using the products of the attempted NaBq₄ syntheses and tested in the same manner as the Alq₃, Gaq₃, Znq₂, and Mgq₂ fingerprint powders.