Green emitting diatomite-derived Zn₂SiO₄:Mn as a dual functional sensor for the development of latent fingerprints

By using naturally abundant diatomite with unique particle and porosity structures as the silica precursor, a novel green-emitting diatomite-derived Zn₂SiO₄:Mn phosphor has been obtained as a dual functional sensor for developing latent fingerprints, serving as a fingerprint powder and a reagent for small particle reagents (SPRs). Parameters including calcination duration, calcination temperature, molar ratio of manganese salt to zinc and manganese salts, and molar ratio of zinc and manganese salts to diatomite have been adjusted to optimize luminescent property of this phosphor. Formation mechanism has been proposed based on the change of particle morphology and mesopore structure. With respect to material synthesis, high porosity of diatomite plays a critical part in ensuring uniform doping of Mn²⁺, lowering reaction temperature, sparing inert or reducing atmosphere. Furthermore, surplus diatomite in the precursors results in basic retention of particle morphology which is favorable for latent fingerprint development. Efficient green emission centered at 525 nm of the diatomite-derived Zn₂SiO₄:Mn under 254 nm excitation originates from the ⁴T₁ → ⁶A₁ transition, making it a very capable fluorescent fingerprint powder that can suppress interferences from various surfaces, especially with the aid of 530 nm band-pass filter as an optical filter and green channel of RGB images as a digital filter. Given that the luminescence of diatomite-derived Zn₂SiO₄:Mn phosphor is not subject to external environment factors such as water or dissolved components, a fluorescent SPR prepared by adding a certain amount of this powder (10 mg mL^-1) to an aqueous solution of sodium dodecyl sulfate (0.050 wt%) shows better performance compared with some commercially available SPRs. Latent fingerprints on glass sheets can be clearly visualized even if they have been immersed in water as long as 5 days. Therefore, the successful acquisition of green luminescent diatomite-derived Zn₂SiO₄:Mn contributes to both the synthesis of this popular green-emitting phosphor and the application of fingerprint development.