Recently, all-inorganic perovskite quantum dots (QDs) (CsPbX 3 , X = Cl, Br, I) as the emerging semiconductor materials have been intensively studied owing to superior optical properties. Currently, the strategy for preparation of inorganic perovskite QDs mainly focuses on the hot-injection method, but requires inert gas protection and is difficult to mass-produce. In this work, we developed a simple and low-cost strategy for preparing highly luminescent and air-stable all-inorganic perovskite QDs by directly heating perovskite precursors in octane in air. The emission wavelength of CsPbX 3 perovskite QDs can be tunable from ultraviolet (UV) to infrared region by simply controlling their halide composition and display high PLQYs. Moreover, CsPbX 3 perovskite QDs in octane can exist more than half a year in air and the film of CsPbX 3 perovskite QDs also shows good thermal stability and air stability, especially high iodide-substituted CsPbBr 3− x I x perovskite QDs. The CsPbX 3 perovskite QDs can be easily blended with PDMS and used as color conversion layer on the blue LEDs chip for high-quality white LEDs. Our work opens a window for the potential application of such highly luminescent material in the fields of multicolor LEDs, backlight display and other related optoelectronic devices.
Li Dong,Weichun Huang,Hongwei Chu,Ying Li,Yunzheng Wang,Shengzhi Zhao,Guiqiu Li,Han Zhang,Dechun Li
Bismuthene quantum dots (Bi-QDs) were synthesized via the liquid phase exfoliation (LPE) method for the passive Q-switching operation in near-infrared (NIR) region. The nonlinear optical properties of the prepared Bi-QDs were investigated by the open-aperture Z-scan technology. The modulation depths were 18.1% and 5.1% at 1.06 and 1.34 µm, respectively. Based on the Bi-QDs saturable absorber, passively Q-switched Nd:GdVO 4 lasers operating at 4 F 3/2 → 2 I 11/2 and 4 F 3/2 → 2 I 13/2 transitions were demonstrated, showing the wideband optical modulation in NIR regime. For the 4 F 3/2 → 2 I 13/2 transition lasing at 1.34 µm, the shortest pulse duration of 155 ns was obtained with a repetition rate of 457 kHz. With respect to the 4 F 3/2 → 2 I 11/2 transition at 1.06 µm, the minimum pulse duration was 150 ns with a repetition rate of 424 kHz, leading to a single pulse energy of 261 nJ and a peak power of 1.68 W. In addition, the ground state absorption cross section and the excited state absorption cross section of Bi-QDs were also investigated for the first time. The impact of the excited state lifetime on the output parameters was numerically stimulated by the coupled rate equations. Our work confirmed that the trap state in Bi-QDs played an important role in the pulse generation mechanism.
We report the interaction between different sizes of CdTe quantum dots (CdTe QDs) and copper (II) ion (Cu 2+ ) via experimental and theoretical aspects. Different sizes of CdTe QDs are synthesized and size effects on the selectivity in the detection of Cu 2+ ions are studied. Experimental results indicate that with the size of CdTe QDs from 1.8 nm to 2.7 nm and to 3.2 nm increases, the linear range gets wider. For the smallest size of QD (QD 524 , 1.8 nm), the linear range is 1.0–5.0 × 10 −5 M with a limited detection of 2.8 × 10 −5 M. The Stern–Volmer plots at different temperatures demonstrate that the fluorescence of CdTe QDs is quenched by Cu 2+ ion through a dynamic quenching mechanism, and the physiological mechanism is analyzed. Electrons are transferred from CdTe QDs to Cu 2+ ion, and Cu 2+ ion acquire electrons and are reduced to Cu + ion, leading to fluorescence quenching . Meanwhile, with the increase in the number of transferred electrons, the phenomenon of fluorescence quenching is more obvious. In order to validate the process of electron transfer , the amount of transferred charge between Cu 2+ and CdTe QDs are calculated by using first principles density functional theory (DFT). Calculation results show that the smaller the QDs are, the more electrons they transfer. The linear range of the smaller size QDs (QD 524 ) is the narrowest, indicating fluorescence quenching is indeed the most obvious of all three sizes.
危险品化学品经营许可证（带存储）