Enhancement of the Sub-Band-Gap Photoconductivity in ZnO Nanowires through Surface Functionalization with Carbon Nanodots

Abstract

We report on the surface functionalization of ZnO nanowire (NW) arrays by attachment of carbon nanodots (C-dots) stabilized by polyethylenimine. The photoconductive properties of the ZnO NWs / C-dots devices were investigated under photoexcitation with photon energies below and above the ZnO bandgap. The results indicate an increased photoresponse of the functionalized devices in the visible spectral range, as well as enhanced UV photoconductivity. This is attributed to the fast injection of photoexcited electrons from the C-dots into the conduction band of the ZnO NWs, and the subsequent slower desorption of molecular species from the NW surface, which reduces the surface depletion region in the NWs. The surface functionalization

Room-temperature photodetectors and VOC sensors based on graphene oxide–ZnO nano-heterojunctions

“…In contrast to the other ZnO-GO composite materials, at a 32:1 ZnO/GO ratio, we observed that the dark-current is decreased while the photo-current is increased. The drop in dark-current has been attributed in the literature [64][65][66][67][68][69][70] to the formation of a heterojunction at the surface of ZnO (n-type) semiconductor and p-type material such as NiO, which decreases the available free carriers. Specifically, Retamal et al 67 stated the occurrence of nanoscale heterojunctions between p-type NiO and n-type ZnO enhances the surface band bending of ZnO nanowires, improving the spatial separation efficiency of photogenerated electrons and holes, thus resulting in a larger number of free electron carriers in the ZnO.…”

Functionalized carbon dots on TiO2 for perovskite photovoltaics and stable photoanodes for water splitting

“…Several works have evidenced sensitization from CDs to TiO 2 under visible light, with fast transfer of excited electrons from the HUMO level of the CD to the conduction band of TiO 2 [18,19,21,23,[26][27][28]30]. This mechanism for water splitting operates in other CD/semiconductor electrodes such as CD/Fe 2 O 3 [31], CD/ZnO [32] and CD/WO 3 [33]. However, electron transfer from TiO 2 to the CD seems to be also possible, particularly under UV irradiation [19,23].…”

Dielectrophoretic manipulation of nanomaterials: A review

“…These multiple individual nanowires could be selected according to their electrical characteristics and precisely positioned at different locations in a low‐conductivity liquid to form functional nanodevices with desired electrical properties. In addition, there are numerous other relevant excellent researches based on DEP manipulation of one‐dimensional nanomaterials, which are not be discussed in detail here .…”