Challenges in Determining the Location of Dopants, to Study the Influence of Metal Doping on the Photocatalytic Activities of ZnO Nanopowders

Abstract

Impurity doping is one of the common approaches to enhance the photoactivity of semiconductor nanomaterials by increasing photon-capture efficiency in the visible light range. However, many studies on the doping effects have produced inconclusive and conflicting results. There are some misleading assumptions and errors that are frequently made in the data interpretation, which can lead to inconsistent results about the doping effects on photocatalysis. One of them is the determination of the location of dopants. Even using advanced analytical techniques, it is still challenging to distinguish between bulk modification and surface modification. The paper provides a case study of transition-metal-doped ZnO nanoparticles, whereby demonstrating common pitfalls in the interpretation of the results of widely-used analytical methods in detail, and discussing the importance of using a combination of many characterization techniques to correctly determine the location of added impurities, for elucidating the influence of metal doping on the photocatalytic activities of semiconductor nanoparticles.

Barium‐Doped Zinc Oxide Thin Films as Highly Efficient and Reusable Photocatalysts

“…This might be due to the accumulation of BaCO 3 as a secondary phase on the surface of ZnO, which decreases the effective surface area exposed to RhB as evidenced in Figure (d). The presence of more BaCO 3 particles on the ZnO surface hinders the incoming radiation and thus acts as a free‐radical scavenger …”

“…The presence of more BaCO 3 particles on the ZnO surface hinders the incoming radiation and thus acts as a free-radical scavenger. [52] Further, to verify the photogeneration of charge carriers and their separation, we have performed the current-voltage (IÀ V) characteristics of ZnO and Zn 0.9 Ba 0.1 O films in dark and under visible light produced by 5 W LED bulb and are shown in Figure 8. The higher conductivity in Zn 0.9 Ba 0.1 O films under the dark conditions can be attributed to the presence of oxygen vacancies as evidenced by XPS, Raman and PL analysis.…”

Study on crystallographic and electronic structure of micrometre-scale ZnO and ZnO:B rods via X-ray absorption fine-structure spectroscopy

“…B-doped ZnO has received much attention over the last ten years due to its potential applications in the field of transparent conductive oxides and dilute magnetic semiconductors (Pawar et al, 2009;Tahar & Tahar, 2005;Steinhauser et al, 2007Steinhauser et al, , 2008Xu et al, 2010). The accurate determination of the location of dopants is important for the explanation of the dopant effect on the properties of the parental materials (Tsuzuki et al, 2019). While X-ray diffraction (XRD) is the standard method for the determination of the crystallographic structure and phase of bulk materials, doping studies can be challenging for XRD when submicrometre-size particles are to be investigated (Jeong et al, 2008).…”

Recent Advances in Zinc Oxide Nanostructures with Antimicrobial Activities

“…The photocatalytic performance of ZnO nanostructures under visible light can be enhanced by doping with transition metals and noble metal NPs. Typical transition metal dopants include copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), nickel (Ni) and chromium (Cr) [100][101][102][103][104][105][106][107][108][109][110][111][112], while noble metal NPs used are gold (Au), and silver (Ag) [113][114][115][116][117][118][119]. The ionic radius of Zn 2+ , Co 2+ , Cu 2+ , and Mn 2+ is 0.074, 0.072, 0.073, and 0.080 nm, respectively [100,106].…”