Search

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+@SiO2upconverting 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 SiO2shell layer thickness. Simultaneously, based on the fluorescence resonance energy transfer phenomenon, we applied the Na3GaF6:Ho3+,Yb3+@SiO2upconversion 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.

Er3+- and Tm3+-doped CaxSr2‒xNb2O7(CxS2‒xN, x= 0.6, 0.8, 1.0, 1.2, 1.4) phosphors with layered perovskite structure were designed. These phosphors exhibit a dominant emission peak at 549 nm under 980 nm laser excitation, attributed to the 4S3/2→4I15/2transition. By increasing the content of Ca2+, the crystal field regulation of rare earth ions is realized and the luminescence enhancement is induced, which is manifested by the increase of 2H11/2,4S3/2→4I15/2emission. Furthermore, the temperature sensing sensitivities of C0.6S1.4N:Er,Tm and C0.6S1.4N:Er,Tm based on non-thermally coupled energy levels were studied. Finally, an anti-counterfeiting imprint was prepared using phosphors, which have high brightness and excellent photothermal stability. This work not only confirms that closer ionic radii substitution enables to increase the electronic density of states, improve the crystal field symmetry and enhance the luminescence, but also provides a promising phosphor system for temperature sensing and anti-counterfeiting applications, opening up new prospects in the optimization of the optical properties of phosphors.

A set of germanate garnet phosphors containing Tb3+and Eu3+were adequately synthesized using the high-temperature solid-state technique. The structural properties, photoluminescence characteristics, fluorescence lifetimes, and temperature-sensing capabilities of the phosphors were thoroughly investigated. X-ray diffraction confirms the crystalline structure of the phosphors, while photoluminescence spectra reveal a colour shift attributed to the transfer of energy from Tb3+to Eu3+as the concentration of Eu3+increases. The phosphors excited by UV light display a transition in colour from green to yellow, and subsequently to red, which can be used as a colour tunable phosphor in white light-emitting diode (w-LED) applications. As a novel temperature sensing material, the maximum relative sensitivity of Ca3Sc2Ge3O12: Tb3+, Eu3+phosphor is 0.1044 K–1(298 K), highlighting its potential for applications in temperature sensing.