Hexagonal ZnO/SnO2 core–shell micropyramids: epitaxial growth-based synthesis, chemical conversion, and cathodoluminescence

Abstract

In this paper, ZnO/SnO 2 core-shell micropyramids were successfully prepared via a chemical vapor deposition process that is based on the epitaxial growth of SnO 2 on the surface of ZnO hexagonal micropyramids. Upon controlling appropriate deposition times and flow rates of the precursor, two epitaxial growth modes of SnO 2 , i.e. a continuous thick film and well-arranged one-dimensional nanostructures were observed in the ZnO/SnO 2 core-shell micropyramids. Taking advantages of the difference in acid resistance between ZnO and SnO 2 , the as-prepared ZnO/SnO 2 micropyramids were further converted into SnO 2 hollow micropyramids with a facile acid-etching treatment. Structural analysis revealed that the lattice mismatch degree between epitaxial planes determines the preferential growth direction of the SnO 2 epitaxial layer on the ZnO surface. Compared to the pristine ZnO template, interestingly, the ZnO/ SnO 2 core-shell micropyramids exhibited very strong green emission around 504 nm. Such enhanced green emission should be induced by high-density structural defects generated in the interfacial area during the epitaxial growth.

Photocatalysis and Bandgap Engineering Using ZnO Nanocomposites

“…The photocatalytic activity of core-shell particles was higher and the reported reason by the authors was the increase of charge separation efficiency [224]. Core-shell micropyramids of ZnO/SnO 2 have also enhanced optical properties [225].…”

Controlled Growth of Supported ZnO Inverted Nanopyramids with Downward Pointing Tips

“…34,[36][37][38][39][40] The latter encompass, among others, transparent conducting oxides, 9,14,41 (photo)catalysts for various processes, [35][36][42][43][44][45] light emitting diodes 2,46 and lasers, 30,39 electrodes for dye-sensitized 1,17,23,47 and photoelectrochemical cells, 5,36,[48][49][50] nanostructured films with for anti-fogging and self-cleaning applications, 30,38,[51][52] as well as nanoscale transducers, field emitters, resonators 1,13,16,53 and solid state gas sensors. 11,22,46 Therefore, various preparation routes 15,26,28,[54][55] (from wet chemical approaches, 33,42,45,53,56 to hydrothermal/so...…”

“…57 In this regard, most of the work done so far has concerned arrays of 1D ZnO systems grown on specific substrates 8,10,47,[49][50]53,57 whereas relatively few papers have reported on the growth of ZnO pyramids and cone-shaped structures, although the latter are highly desirable for many applications. 18,33,37 To date, the obtainment of ZnO-based nanopyramids has been most reported in a powdered form, 7,11,21,25,35,56 whereas only a few reports have described their fabrication as supported systems with upward pointing tips 13,37,62 and a very high density on the growth substrate. 18,23 Nevertheless, supported systems stand as a more attractive choice for functional applications, thanks to the lower tendency to sintering and/or deactivation and to the possibility of being directly integrated into functional devices.…”

“…The tailoring of zinc oxide chemical, physical, and functional properties as a function of the size and shape of ZnO building blocks offers a huge possibility for a variety of technological end-uses. ,− The latter encompass, among others, transparent conducting oxides, ,, (photo)­catalysts for various processes, ,,− light emitting diodes , and lasers, , electrodes for dye-sensitized ,,, and photoelectrochemical cells, ,,− nanostructured films with antifogging and self-cleaning applications, ,,, as well as nanoscale transducers, field emitters, resonators, ,,, and solid-state gas sensors. ,, Therefore, various preparation routes ,,,, (from wet chemical approaches, ,,,, to hydrothermal/solvothermal processes, ,,,, electrodeposition, ,, atomic layer deposition, , chemical vapor deposition (CVD), ,,,, and evaporation ,,, ) have been proposed to fabricate ZnO-based systems with tailored morphologies and dimensional scales from micro- to nanolevel, with the aim of increasing their performances. , In this regard, beside morphology, the defect content and active area significantly affect the p...…”

Synthesis of highly surface-textured ZnO thin films by aerosol assisted chemical vapour deposition

“…The intensity of (10 11) peak exceeds that of ( 1010) in S3 and S4, which is consistent with the XRD results of pyramid-shaped ZnO in previous studies. 19,27 It is noteworthy that, different with the a-axis oriented ( 1010) and c-axis oriented (0001) plane, whose higher XRD peak intensity oen means less corresponding surfaces getting exposed, the promotion of ( 1011)-oriented crystal growth will result in larger surface areas and higher diffraction signals together due to its unique symmetry. Thus, combined with the SEM details in Fig.…”