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In this paper, fluorescent and optical temperature sensing bi-functional Li+-doping NaLuF4:Ln (Ln = Yb3+, Tm3+/Er3+) nanocrystals were synthesized via a simple hydrothermal method using oleic acid as a capping ligand. The crystal phase, size, upconversion (UC) properties, and optical temperature sensing characteristics of the crystals can be easily modified by Li+ doping. The results reveal that additional Li+ can promote the transformation from the hexagonal phase to the cubic phase and reduce the size of the nanocrystals. In addition, NaLuF4:Ln (Ln = Yb3+, Tm3+, Li+) nanocrystals present efficient near infrared (NIR) emission, which is beneficial for in vivo biomedical applications due to the increased penetration depth and low radiation damage of NIR light in bio-tissues. More importantly, under 980 nm excitation, the temperature dependent UCL from the 2H11/2 and 4S3/2 levels of Er3+ ions in NaLuF4:Yb3+,Er3+,Li+ microcrystals was investigated systematically. The fluorescence intensity ratios (FIR) of the pairs of thermally coupled levels were studied as a function of temperature in the range of 298–523 K. The maximum sensor sensitivities were found to be about 0.0039 K−1 (523 K) by exploiting the UC emissions from the 2H11/2 and 4S3/2 levels. This suggests that the Li+-doped upconversion luminescence (UCL) materials are promising prototypes for application as multi-mode probes for use in bio-separation and optical thermometers. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite quantum dots (PeQDs) have attracted much attention recently owing to their excellent illumination properties; however, the instability of PeQDs has restricted their application. In this work, we successfully synthesized CsPbX3 (X = Br, I) PeQD/Ergo films by encapsulation of PeQDs within Ergo® optical adhesive 8500 (Ergo 8500). The CsPbX3 PeQD/Ergo films exhibited great water-resistance and air-stability. The photoluminescence of the films was stable for weeks in water and months in air. By trying different structures and PeQDs volumes, CsPbX3 PeQD/Ergo white LEDs (W-LEDs) were successfully fabricated. The CsPbX3 PeQD/Ergo W-LEDs exhibited high quality white light with a CIE color coordinate of (0.3692, 0.3442) and correlated color temperature of 4059 K. [ABSTRACT FROM AUTHOR]

Mono-dispersed Gd6O5F8:Yb3+/Er3+ micro-particles with different doping concentrations (Er3+: 0.1–1%) were synthesized by a facile hydrothermal route. The emission spectra, luminescent dynamic power-dependence and temperature sensing of up-conversion photoluminescence were investigated in detail. Under 980 nm excitation, the as-prepared samples exhibit intense red up-conversion and NIR emissions, which are influenced by the doping concentrations of Er3+ within Gd6O5F8. With increasing concentrations of Er3+ ions, the visible up-conversion emissions first increase and then decrease, but NIR down-conversion emissions display a distinct trend, in which one peak at 1010 nm is highly suppressed and another at 1530 nm is increased quickly. Furthermore, the 980 nm excited optical temperature sensing property of the synthesized sample is realized over a wide temperature range by monitoring the intensity of up-conversion luminescence. The study provides a novel strategy based on lanthanide oxy-fluoride micro-particles for multifunctional displays, lighting and temperature sensing in a single system. [ABSTRACT FROM AUTHOR]

Among the chemical doping elements, nitrogen atoms play a critical role in tuning the intrinsic properties or exploiting new phenomena of carbonaceous materials. Herein, we report a facile strategy to synthesize nitrogen-doped carbon dots (NCDs) using glutamic acid as the precursor via a one-step thermal conversion process. The as-produced NCDs exhibit bright blue photoluminescence (the quantum yield of ca. 23.2%), and the emission wavelength could be slightly tuned through changing the parameters of the synthesizing process. Interestingly, apart from their superior luminescence characters, unexpected cathodoluminescence (CL) and frequency upconverted emission properties were both observed in the NCDs. [ABSTRACT FROM AUTHOR]

In this paper, fluorescent and optical temperature sensing bi-functional Li+-doping NaLuF4:Ln (Ln = Yb3+, Tm3+/Er3+) nanocrystals were synthesized via a simple hydrothermal method using oleic acid as a capping ligand. The crystal phase, size, upconversion (UC) properties, and optical temperature sensing characteristics of the crystals can be easily modified by Li+ doping. The results reveal that additional Li+ can promote the transformation from the hexagonal phase to the cubic phase and reduce the size of the nanocrystals. In addition, NaLuF4:Ln (Ln = Yb3+, Tm3+, Li+) nanocrystals present efficient near infrared (NIR) emission, which is beneficial for in vivo biomedical applications due to the increased penetration depth and low radiation damage of NIR light in bio-tissues. More importantly, under 980 nm excitation, the temperature dependent UCL from the 2H11/2 and 4S3/2 levels of Er3+ ions in NaLuF4:Yb3+,Er3+,Li+ microcrystals was investigated systematically. The fluorescence intensity ratios (FIR) of the pairs of thermally coupled levels were studied as a function of temperature in the range of 298-523 K. The maximum sensor sensitivities were found to be about 0.0039 K-1 (523 K) by exploiting the UC emissions from the 2H11/2 and 4S3/2 levels. This suggests that the Li+-doped upconversion luminescence (UCL) materials are promising prototypes for application as multi-mode probes for use in bio-separation and optical thermometers.

GdSr 2 AlO 5 :Yb 3+ /Er 3+ micro-particles were synthesized by a simple solid state method. The structure, morphology, size and upconversion luminescence features have been characterized. These results indicated that GdSr 2 AlO 5 has a contracted tetragonal cell and has irregular block shaped particles with sizes of about 5 μm. During upconversion, green ( 2 H 11/2 , 4 S 3/2 → 4 I 15/2 ) (527 nm, 549 nm) and red ( 4 F 9/2 → 4 I 15/2 ) (665 nm) emissions had been observed, both of which occurred via a two-photon population process. In addition, green UC emission characteristics were studied, and it was found that its temperature ranged from 293 K to 473 K and the sensitivity was 0.0054 K -1 at 473 K. This indicated that GdSr 2 AlO 5 :Yb 3+ /Er 3+ micro-particles may have potential application in high temperature environments for safety signs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Mono-dispersed Gd 6 O 5 F 8 :Yb 3+ /Er 3+ micro-particles with different doping concentrations (Er 3+ : 0.1-1%) were synthesized by a facile hydrothermal route. The emission spectra, luminescent dynamic power-dependence and temperature sensing of up-conversion photoluminescence were investigated in detail. Under 980 nm excitation, the as-prepared samples exhibit intense red up-conversion and NIR emissions, which are influenced by the doping concentrations of Er 3+ within Gd 6 O 5 F 8 . With increasing concentrations of Er 3+ ions, the visible up-conversion emissions first increase and then decrease, but NIR down-conversion emissions display a distinct trend, in which one peak at 1010 nm is highly suppressed and another at 1530 nm is increased quickly. Furthermore, the 980 nm excited optical temperature sensing property of the synthesized sample is realized over a wide temperature range by monitoring the intensity of up-conversion luminescence. The study provides a novel strategy based on lanthanide oxy-fluoride micro-particles for multifunctional displays, lighting and temperature sensing in a single system.