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Biosensors working in the second near-infrared (NIR-II) spectral region have recently gained great attention owning to their deep tissue bioimaging and high spatiotemporal resolution. However, there is still a challenge to develop efficient nanothermometers based on NIR-II luminescence. Herein, we present a pioneering advancement in the field of nanothermometry by synthesizing a novel nanothermometer, a composite of fluoride nanocrystals and quantum dots. This NaYF 4 :1Nd-Ag 2 S QDs@SiO 2 nanocomposite demonstrates exceptional functionality, being excited by a single light irradiation at 808 nm for NIR-II luminescence imaging. Notably, the composite emits at two distinct wavelengths-1064 nm and 1125 nm, attributable to Nd3+ and Ag 2 S QDs, respectively. This unique emission profile enables deeper tissue penetration, mitigating overheating risks compared to conventional excitation sources at 980 nm. Furthermore, the nanomaterials exhibit remarkable temperature-sensing capabilities, with maximum sensitivities of 0.81%K−1 (S R) at 333 K. These superior sensitivities outperform many existing temperature sensors relying on thermally coupled Stark sublevels. The SiO 2 matrix not only encapsulates and protects the fluoride nanocrystals and quantum dots but also shields them from aqueous environments, ensuring outstanding luminescence stability. Our findings highlight the potential of this nanothermometer as a highly efficient temperature sensor with promising applications in cutting-edge bioapplications. This development introduces a new frontier in temperature sensing and bioimaging, showcasing its potential for transformative contributions to the field. [Display omitted] • Successful synthesis of a novel nanothermometer based on a composite comprising fluoride nanocrystals and quantum dots. • The emission intensity of Nd3+ and Ag 2 S QDs serves as a temperature sensing mechanism (0.81%K−1 (S R) at 333 K). • A versatile platform allows the integration of two different luminescent nanomaterials to meet customized requirements. • The SiO 2 matrix shields NCs and Ag 2 S QDs from water environments, ensuring excellent luminescence stability. [ABSTRACT FROM AUTHOR]

X-ray excited optical luminescence (XEOL) imaging shows great potential applications in security inspection and computed tomography. Lanthanide doped fluoride nanoscintillators (NSs) do not only exhibit advantages of simple synthetic procedures, tunable emissions and high environmental stability, but also show many new properties through constructing core/shell architectures. However, the strong hysteresis scintillation luminescence greatly restrict their practical applications. Herein, we verify that this hysteresis can be fully restricted by employing core/shell structure to inhibit the generation of Frenkel defects and incorporating Gd3+ ions to introduce extra energy migration process. As a result, upon continuous X-ray irradiation, the XEOL intensity of the LiYF 4 : 15Tb/25Gd@LiYF 4 core/shell NSs almost keeps unchanged. Our results provide important information for designing new NSs with greatly reduced hysteresis scintillation luminescence, which show promising applications in the field of stable X-ray imaging. [Display omitted] • Hysteresis scintillation is greatly restricted in the LiYF 4 : 15Tb/25Gd@LiYF 4 NSs. • Upon continuous X-ray irradiation, its XEOL intensity is only increased ∼1.6%. • The core/shell structure can inhibit the generation of Frenkel defects. • Incorporating Gd3+ ions can introduce extra energy migration process. [ABSTRACT FROM AUTHOR]

A series of Er 3+ doped and Er 3+ /Yb 3+ codoped SrTiO 3 nanocubes with varying dopant concentrations have been successfully synthesized by a facile hydrothermal method. The doping effects on phase purity, morphology and microstructure of samples were identified by power X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that SrTiO 3 nanocubes have a typical perovskite structure with the edge length ranging 20–50 nm. The Er 3+ and Yb 3+ ions were successfully doped into the crystal lattice of SrTiO 3 , but did not alter crystal structure of SrTiO 3 . The photon up-conversion (UC) photoluminescence (PL) measurements indicated that the intense green light emission of Er 3+ ions around 525 nm, 550 nm and red light emission centered at 670 nm in UC processes populated by 980 nm laser excitation have been achieved in SrTiO 3 nanocubes. Moreover, the PL intensity of Er 3+ -doped SrTiO 3 nanocubes was greatly enhanced while introducing the Yb 3+ to the crystal structure, especially the red emission. The mechanisms for these emissions probably due to the excited state absorption (ESA) and energy transfer (ET) process. Er 3+ /Yb 3+ -codoped single-crystal perovskite SrTiO 3 nanocubes could be interesting objects for applications in mechanical−electrical luminescence such as electric field modulation luminescence and mechanoluminescence. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) phosphors converted to light-emitting diodes (pc-LED) sources have extensive application prospects in medical imaging, foodstuff analysis and plant growth fields. However, there are some shortcomings in NIR phosphors, such as narrow emission band and poor thermal stability. Here a new wide band NIR luminescent phosphor Cr3+-doped Sr 3 Sc 4 O 9 (SSO) is introduced. The emission spectrum ranges from 600 nm to 1000 nm, with a peak value of 761 nm and the value of full width at half maximum (FWHM) is 120 nm. The internal quantum efficiency (IQE) of sample is about 87% according to the fitting result. The most appropriate doping concentration is x = 0.02 and the best excitation wavelength is 468 nm, which matches the commercial blue chip. At the same time, the phosphor shows good thermal stability in variable temperature spectrum test, and can maintain 70.4% emission intensity at 373 K relative to room temperature. To better understand its practical applications, packaged pc-LED is designed to show good NIR light penetration in spectral penetration tests. This study provides an excellent choice of NIR phosphors. • Sr 3 Sc 4 O 9 :Cr3+ phosphors are promising near-infrared (NIR) emission materials. • The phosphors retain 70.4% of initial emission intensity at 373 K. • The IQE of sample is about 87%. • The pc-LED device can be applied in NIR penetration analysis. [ABSTRACT FROM AUTHOR]