Yangyang Xie,Chong Geng,Yiqun Gao,Jay Guoxu Liu,Zi-Hui Zhang,Yonghui Zhang,Shu Xu,Wengang Bi
In this report, to tackle the thermal fluorescent quenching issue of II-VI semiconductor quantum dots (QDs), which hinders their on-chip packaging application to light-emitting diodes (LEDs), a QD-ZnS nanosheet inorganic assembly monolith (QD-ZnS NIAM) is developed through chemisorption of QDs on the surface of two-dimensional (2D) ZnS nanosheets and subsequent assembly of the nanosheets into a compact inorganic monolith. The QD-ZnS NIAM could reduce the thermal fluorescent quenching of QDs effectively, possibly due to fewer thermally induced permanent trap states and decreased Förster resonance energy transfer (FRET) among QDs when compared with those in a reference QD composite thin film. We have demonstrated that the QD-ZnS NIAM enables QDs to be directly packaged on-chip in LEDs with over 90% of their initial luminance being retained at above 85 °C, showing advantage in LED application in comparison with conventional QD composite film.Keywords:quantum dots;nanosheet;assembly;thermal stability
Fan Gao,Rui Lei,Xueyan Huang,Jie Yuan,Cankun Jiang,Wenhui Feng,Lulu Zhang,Ping Liu
Two-dimensional nanomaterial semiconductor is an efficient photocatalyst due to the unique properties such as abundant exposed active sites and large contact area with reactant. Herein, a hierarchical architecture that consists of highly dispersed ZnS nanosheets (ZnS NSs) with S vacancies vertically anchored on the Zn-In-layered-double-hydroxide (Zn-In-LDH) is successfully constructed through in situ etching growth process. The defective ZnS NSs grown perpendicularly on the Zn-In-LDH surfaces with abundant exposed area disperse extensively and exhibit good performance of photocatalytic hydrogen production under visible light irradiation. It is due to the synergistic effect of large specific surface area, separate vertically grown ZnS NSs and S defects, that the optical ZnS/Zn-In-LDH composite shows an improved H 2 evolution rate of 49.3 μmol h −1 g cat −1 (154.8 μmol h −1 g ZnS −1 ) and the AQE at 415 nm can be as high as 1.315 %. Besides, this work is expected to facilitate other analogous nanosheets synthesized based on the layered double hydroxides.
The SnO 2 quantum dots (SnO 2 QDs)/ZnS nanosheets (ZnSNs) heterojunction was fabricated via an in-situ synthetic method at room temperature. Rhodamine B, potassium dichromate, and tetracycline were used to discuss the photocatalytic activities of the as-prepared samples under the visible light illumination. The photocatalytic mechanism of the as-prepared samples was also proposed. The experimental results indicate that the degradation efficiency of the as-prepared SnO 2 QDs/ZnSNs heterojunction first increases and then decreases with increasing the usage of ZnSNs. When the mass ratio of SnO 2 QDs to ZnSNs is 1: 2 in 180 min, the asprepared samples have the highest degradation efficiency of 89.1% for rhodamine B, 97.7% for potassium dichromate, and 83.8% for tetracycline, which are much higher than 51.7%, 26.8%, and 0.9% of pure SnO 2 QDs as well as 37.9%, 87.1%, and 19.1% of pure ZnSNs, respectively. After it is repeatedly degraded for 3 times, it possesses the degradation efficiency of 62.5% for rhodamine B, which increases by 200.5% in comparison with 20.8% of the pure SnO 2 QDs. Moreover, the enhanced photocatalytic performances of the as-prepared hybrids are attributed to the formation of heterojunction between the SnO 2 QDs and ZnSNs. In addition, hydroxyl radicals and superoxide anion radicals play major roles during the photocatalytic degradation process, while holes play a minor role.
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