A series of graphene/CaIn 2 O 4 composites were synthesized using a facile solvothermal method to improve the photocatalytic performance of CaIn 2 O 4 . The reduction of graphene oxide to graphene and the deposition of CaIn 2 O 4 nanoparticles on the graphene sheets can be achieved simultaneously during the solvothermal process. The photocatalytic activities of as-prepared graphene/CaIn 2 O 4 composites for hydrogen evolution from CH 3 OH/H 2 O solution were investigated under visible light irradiation . It was found that graphene exhibited an obvious influence on the photocatalytic activity of CaIn 2 O 4 . The graphene/CaIn 2 O 4 composite reached a high H 2 evolution rate of 62.5 μmol h −1 from CH 3 OH/H 2 O solution when the content of graphene was 1 wt%. Furthermore, the 1 wt% graphene/CaIn 2 O 4 composite did not show deactivation for H 2 evolution for longer than 32 h. This work could provide a new insight into the fabrication of visible light driven photocatalysts with efficient and stable performance.
Er 3+ /Yb 3+ -codoped CaIn 2 O 4 nano-fibers with good morphology were synthesized by electrospinning technique. X-ray diffraction was performed on the synthesized phosphor of nano-fibers to confirm that the CaIn 2 O 4 crystalline phase is dominant in it. The morphology of the nano-fibers was characterized by scanning electron microscopy. Optimal power supply voltage and thickener concentration for the synthesis were obtained. Er 3+ 980-nm-upconverted emission characteristics of the nano-fibers were investigated. The results show that two-photon process is the dominant mechanism for the upconversion emissions. The nano-fibers doped with 5 mol% Er 3+ display the strongest upconversion fluorescence. Temperature characteristics of the green 530 and 550 nm upconversion fluorescence of the nano-fibers were also studied for thermometry purposes. The results reveal that the nano-fibers show thermally stable spectral structure and the ones doped with 5 mol% Er 3+ display the highest thermal sensitivity of green fluorescence intensity ratio. We conclude that there exists an optimal Er 3+ concentration of 5 mol%, and the CaIn 2 O 4 nano-fibers doped with this optimal Er 3+ concentration display some spectroscopic properties favorable for ratiometric thermometry in the high-temperature regime.
Hang Liu,Ziyi Zhang,Jian Liu,Kailin Wang,Yuhong Zhang
In this paper, the upconversion(UC) and downshifting(DS) luminescence and thermal sensing performances of the CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ (RE=Er, Ho) phosphors are investigated in detail. The bright UC emission bands from 450 to 900 nm and the DS luminescence bands from 1000 to 1700 nm are obtained under 980 nm excitation. The typical near infrared(NIR) emisson band(∼1550 nm) of Er 3+ ions and the NIR emission band(∼1200 nm) of Ho 3+ ions are gained. The temperature sensing features of CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ (RE=Er, Ho) phosphors are investigated with the luminescence intensity ratio (LIR) technique. The results indicate that the maximum relative sensitivity (S Rmax ) of CaIn 2 O 4: Er 3+ /Tm 3+ /Yb 3+ sample reaches 1.576% K -1 at 313 K, and the S Rmax of CaIn 2 O 4: Ho 3+ /Tm 3+ /Yb 3+ sample reaches 0.797% K -1 at 353 K in UC range. In addition, the higher temperature measuring sensitivities have been obtained in NIR-II region with the DS luminescence of CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ phosphors. The above results indicate that the CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ phosphors show bright emission bands in visible and NIR-II, and higher sensitivity for temperature measurement. The CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ phosphors present great application in optical temperature measurement.
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