Controlled Fabrication of Quality ZnO NWs/CNTs and ZnO NWs/Gr Heterostructures via Direct Two-Step CVD Method

Abstract

A novel and advanced approach of growing zinc oxide nanowires (ZnO NWs) directly on single-walled carbon nanotubes (SWCNTs) and graphene (Gr) surfaces has been demonstrated through the successful formation of 1D–1D and 1D–2D heterostructure interfaces. The direct two-step chemical vapor deposition (CVD) method was utilized to ensure high-quality materials’ synthesis and scalable production of different architectures. Iron-based universal compound molecular ink was used as a catalyst in both processes (a) to form a monolayer of horizontally defined networks of SWCNTs interfaced with vertically oriented ZnO NWs and (b) to grow densely packed ZnO NWs directly on a graphene surface. We show here that our universal compound molecular ink is efficient and selective in the direct synthesis of ZnO NWs/CNTs and ZnO NWs/Gr heterostructures. Heterostructures were also selectively patterned through different fabrication techniques and grown in predefined locations, demonstrating an ability to control materials’ placement and morphology. Several characterization tools were employed to interrogate the prepared heterostructures. ZnO NWs were shown to grow uniformly over the network of SWCNTs, and much denser packed vertically oriented ZnO NWs were produced on graphene thin films. Such heterostructures can be used widely in many potential applications, such as photocatalysts, supercapacitors, solar cells, piezoelectric or thermal actuators, as well as chemical or biological sensors.

Functionalization of Pristine, Metallic, and Semiconducting-SWCNTs by ZnO for Efficient Charge Carrier Transfer: Analysis through Critical Coagulation Concentration

“…E 2 (high) peak originates from oxygen vibration, lattice disorder and phonon–phonon interactions in ZnO. Major dominant Raman peaks corresponding to ZnO, E 2 (high), A 1 (LO)/E 2L (LO) at ∼338 and ∼580 cm –1 , respectively, were also seen to be present, with additional peaks at 800–1000 cm –1 corresponding to SWCNTs . The comparison of the E 2 (high) peak is demonstrated in Figure S3 from the ZnO perspectives, comparing pristine ZnO with m-SWCNT+ZnO, s-SWCNT+ZnO, and p-SWCNT+ZnO in Figure S3c–e sequentially.…”

“…Major dominant Raman peaks corresponding to ZnO, E 2 (high), A 1 (LO)/E 2L (LO) at ∼338 and ∼580 cm –1 , respectively, were also seen to be present, with additional peaks at 800–1000 cm –1 corresponding to SWCNTs. 38 The comparison of the E 2 (high) peak is demonstrated in Figure S3 from the ZnO perspectives, comparing pristine ZnO with m-SWCNT+ZnO, s-SWCNT+ZnO, and p-SWCNT+ZnO in Figure S3c–e sequentially. Shifting of E 2 (high) Raman peak positions to lesser wavenumbers were observed in the ZnO-functionalized SWCNTs by 4 cm –1 for m-SWCNT and s-SWCNT and 2 cm –1 for p-SWCNT.…”

Single-step growth of p-type 1D Se/2D GeSexOy heterostructures for optoelectronic NO2 gas sensing at room temperature

“…2e shows that the peak of O 1s at 531.67 eV is assigned to the O–Ge band, 70 and the peak located at 532.98 eV corresponds to O–Si, respectively. 71…”

“…2e shows that the peak of O 1s at 531.67 eV is assigned to the O-Ge band, 70 and the peak located at 532.98 eV corresponds to O-Si, respectively. 71 The optical absorption spectrum of the 1D Se/2D GeSe x O y heterostructures is shown in Fig. 2f.…”

ZnO Nanowires: Growth, Properties, and Energy Applications

“…Durbach et al report a nano-second laser irradiation process for generating Au catalysts over dedicated areas, thus controlling the position of ZnO nanowires grown by chemical vapor deposition through a selective growth approach compatible with large surfaces [ 1 ]. Schaper et al show the formation of ZnO nanowires over single-walled carbon nanotubes and graphene using a full chemical vapor deposition approach, further achieving selective growth over dedicated areas [ 2 ]. Another challenge consists in developing innovative heterostructures made of ZnO nanowires combined with a selected semiconductor.…”