Na3GaF6:Ho3+,Yb3+@SiO2: A Novel Upconversion Sensor Material for Food Pigment Detection Application

Upconverting nanocrystals are widely used in the field of trace substance detection, but quantitative analysis with high sensitivity remains challenging. In this paper, we developed a novel optical sensing material for food pigment detection. A series of upconverting nanocrystals Na₃GaF₆:Ho³⁺,Yb³⁺ with a monoclinic phase were synthesized by the coprecipitation method. To modify the nanocrystal surface and limit luminescence quenching, Na₃GaF₆:Ho³⁺,Yb³⁺@SiO₂ upconverting materials with a core–shell structure were designed, where the high-intensity upconversion emission was realized by the modulation of the Ho³⁺/Yb³⁺ doping ratio and SiO₂ shell layer thickness. Simultaneously, based on the fluorescence resonance energy transfer phenomenon, we applied the Na₃GaF₆:Ho³⁺,Yb³⁺@SiO₂ upconversion luminescent material to the concentration detection of food pigment (amaranthine red), and the detection mechanism was also analyzed in detail. In addition, this work presents a promising strategy for food pigment detection with high sensitivity and selectivity, which holds significant practical value and effectively safeguards human health.