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.