Yellow emitting Fe3O4/ZnS hybrid: A probe for in-vitro dermatoglyphics and anti-counterfeiting applications

Abstract

Ambidextrous phosphor materials (performance intact in powder and dispersed condition) with large Stokes shift and excited state lifetime is highly preferable due to the stringent requirements of latent finger print (LFP) detectors and anti-counterfeiting markers. In this work, ZnS grafted Fe3O4 core shell luminomagnetic hybrid have been prepared via facile hydrothermal route. Interestingly, instead of pristine green emission of ZnS the prepared ambidextrous hybrid material (Fe3+:Fe3O4/ZnS) shows intense yellow emission under 350 nm UV exposure. Detailed experimental investigation supported by theoretical modelling and plausible energy band diagram demonstrates an inherent self-substitution mechanism of Zn2+ ions of ZnS shell by Fe3+ ions from the magnetite core which plays a decisive role in achieving the novel yellow emission. Maintaining superparamagnetic behavior in room temperature, the designed rare-earth (RE) free hybrid is employed as a proficient luminescent labeling agent for LFP detection (up to level III, stability up to 45 days) and anti-counterfeiting marker with higher accuracy compared to virgin ZnS.