We, herein, report the synthesis of umbrella-like CdS single crystal with exposed high-activity (002) facets first time by using a one-step hydrothermal method with cadmium acetate dihydrate (Cd(CH 3 COO) 2 ·2H 2 O) and ammonium thiocyanate (NH 4 SCN), and its possible growth mechanism was discussed. As a contrast, CdS nanoparticles with different morphologies were also synthesized. The morphology, composition and photocatalytic property of as-synthesized samples were determined by XRD, SEM, TEM, UV–Vis DRS, PL and photocurrent tests, respectively. The results show that umbrella-like CdS under UV (20 min) and visible light (80 min) irradiation, the removal rate of rhodamine B was as high as 99.1% and 99.3%, respectively. Moreover, even though the particle size of umbrella-like CdS particle is larger than as-synthesized CdS nanospheres, it still shows excellent photocatalytic degradation activity due to its exposed high-energy (002) facets. And its excellent application prospects are conceivable. The current work provides a new paradigm in material morphology design, especially in the construction of highly active surfaces for photocatalysis and photoelectric conversion.
Herein, a novel amorphous monodisperse Co3O4 quantum dots/3D hexagonal CdS single crystals (0D/3D Co3O4 QDs/CdS) p–n heterojunction was constructed by a simple hydrothermal and electrostatic self-assembly method. The amorphous monodispersed Co3O4 QDs (≈4.5 nm) are uniformly and tightly attached to the surface of the hexagonal CdS single crystals. The sample, 0.5% CQDs/CdS exhibits outstanding hydrogen evolution activity of 17.5 mmol h−1 g−1 with a turnover number (TON) of 4214, up to 10.3 times higher than that of pure CdS. The enhanced photocatalytic activity can be attributed to the synergistic effect of the p–n heterostructure and the quantum confinement effect of Co3O4 QDs, which significantly promoted the separation efficiency of photo-generated electrons and holes. Additionally, the sulfur vacancy also can act as electron trappers to improve carrier separation and electron transfer. The photoelectrochemical and time-resolved fluorescence (TRPL) results further certify the effective spatial charge separation. This work gives an insight into the design of the 0D/3D Co3O4 QDs/CdS p–n heterostructure for a highly efficient photocatalysis.
Semiconductor single-crystal thin films (SCTFs) with nanoscale thickness play an important role in high-performance electronics and optoelectronic devices, owing to the excellent electrical, optical, thermal, and mechanical performance. Although enormous progress has been made in preparing two-dimensional (2D) material SCTFs, it is still challenging to grow SCTFs based on 3D materials with high efficiency. Herein, we report the efficient growth of centimeter-scale CdS SCTFs with the thickness of ∼95.41 nm on the mica substrates using a chemical vapor deposition method. The controlled experiments and the structure characterizations indicate that the SCTFs are formed by the seamless coalescence of the hexagonal CdS nanosheet domains initially grown in the same orientation on the substrate, with the epitaxial relationship of (100)CdS//(110)mica and (110)CdS//(200)mica. Importantly, the CdS SCTF-based photodetectors (PDs) demonstrate a photoswitching (Ion/Ioff) ratio up to 105 and a fast photoresponse speed (trise ≈ 0.5 ms, tdecay ≈ 1 ms). Furthermore, the PDs exhibit excellent stability to at least 2 months of storage in an ambient atmosphere and 1000-time bending. This work paves the way to synthesizing the 3D semiconductor SCTFs on a large scale and promotes their practical application in multifunctional photoelectric devices.
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