Jiawen Wang,Ruoshan Lei,Shilong Zhao,Feifei Huang,Degang Deng,Shiqing Xu,Huanping Wang
Rigorous temperature measurement employed to characterize physic-chemical state has compelled scientists to explore more novel materials for contactless optical thermometry, which must overcome the drawbacks of low sensitivity and poor signal discriminability. Here, a novel dual-mode optical thermometer La 2 ZnTiO 6 : Bi 3+ /Eu 3+ is designed, prepared and characterized via XRD , XPS , EPR, SEM, EDS , PL spectra and decay time. Under 350 nm excitation, the energy transfer process from Bi 3+ to Eu 3+ allows the samples to demonstrate adjustable multi-color emissions. The temperature-dependent emission spectra display that the luminescence intensity of Bi 3+ ions decreases quite faster than that of Eu 3+ ions with temperature, leading to a significant chromaticity shift (∆E = 224 ×10 −3 in 293–473 K) visible to naked eyes. Based on fluorescence intensity ratio of Eu 3+ versus Bi 3+ (FIR = I Eu /I Bi ), the sample shows the maximum relative sensitivity (S r ) of ~1.50% K −1 at 293 K and excellent signal discriminability. Meanwhile, the 5 D 0 → 7 F 2 transition of Eu 3+ ions shows a thermal-responsive lifetime with the optimal S r of 1.23% K −1 at 573 K. This work suggests that the La 2 ZnTiO 6 : Bi 3+ /Eu 3+ double perovskite phosphor has a great potential for dual-mode optical thermometry, being beneficial to obtain precise, sensitive and reliable temperature detection.
A new far-red/green dual-emitting phosphor La 2 ZnTiO 6 :Mn 4+ /Er 3+ (LZT:Mn 4+ /Er 3+ ) was successfully synthesized by the sol-gel method. Under 381 nm excitation, LZT:Mn 4+ /Er 3+ phosphor shows the strong far-red emission peak of 709 nm (Mn 4+ : 2 E g → 4 A 2g ) and weak green emission peak of 523/548 nm (Er 3+ : 2 H 11/2 / 4 S 3/2 → 4 I 15/2 ), which consistent with the requirement of plant growth for far-red and green light. A 1.5-fold enhancement of far-red emission intensity is found in LZT:Mn 4+ /Er 3+ phosphor compared with the Mn 4+ singly-doped counterparts. Moreover, the relative emission intensity of far-red and green can be easily controlled by changing temperature. Utilizing the optimal LZT:0.2%Mn 4+ /2%Er 3+ phosphor as plant lighting, a prototype near-UV-pumped LED device was fabricated. Upon 120 mA driving current, it demonstrated far-red/green dual emission. All the results indicated that the LZT:Mn 4+ /Er 3+ phosphor is a potential material for plant growth illumination with far-red/green light.
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