Abstract:We investigated the local structural properties of ZnO nanoparticles (NPs), nanorods and powder by using extended X-ray absorption ne structure (EXAFS). The average diameter and size of the ZnO NPs and nanorods were about 4.5 nm and 40 nm, respectively. The EXAFS analysis revealed that the bonding lengths of atoms in the ZnO nanorods were slightly elongated along the c-axis while they were shrunken in the ab-plane, as compared with those of the ZnO powder. We did not observe a vacancy or an extra disorder for … Show more
“…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). For study of the electronic structure, local order and conformation of the dopant ion B with respect to the host material ZnO, we resort to synchrotron radiation based X-ray absorption spectroscopy (XAS).…”
Section: Introductionmentioning
confidence: 99%
“…For the XAS we consider two parts: near-edge X-ray absorption fine structure (XANES) and extended X-ray absorption fine structure (EXAFS), which are useful techniques to characterize both electronic structure and local structural properties of materials (Braun, 2017;Ankudinov & Rehr, 1997). There are few studies on the local structural properties of ZnO nanoparticles determined via the EXAFS technique, which describes the bonding lengths, bonding length disorders, coordination and atomic species of neighboring atoms around a probe atom (Jeong et al, 2008). Chiou et al (2004a) worked on the electronic structure of ZnO nanorods by angle-dependent X-ray absorption spectroscopy at the oxygen (O) K-edge and zinc (Zn) L 3 -and K-edges.…”
X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectra were recorded to investigate the electronic structure and local crystal structure of ZnO and ZnO:B powders produced via hydrothermal synthesis. ZnO and ZnO:B grow as micrometre-scale rods with hexagonal shape, as confirmed by scanning electron microscopy micrographs. The number of broken ZnO:B rods increases with increasing B concentration, as observed in the images, due to B atoms locating in between the Zn and O atoms which weakens and/or breaks the Zn–O bonds. However, no disorder within the crystallographic structure of ZnO upon B doping is observed from X-ray diffraction results, which were supported by EXAFS results. To determine the atomic locations of boron atoms in the crystal structure and their influence on the zinc atoms, EXAFS data were fitted with calculated spectra using the crystal structure parameters obtained from the crystallographic analysis of the samples. EXAFS data fitting and complementary k-weight analysis revealed the positions of the B atoms – their positions were determined to be in between the Zn and O atoms.
“…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). For study of the electronic structure, local order and conformation of the dopant ion B with respect to the host material ZnO, we resort to synchrotron radiation based X-ray absorption spectroscopy (XAS).…”
Section: Introductionmentioning
confidence: 99%
“…For the XAS we consider two parts: near-edge X-ray absorption fine structure (XANES) and extended X-ray absorption fine structure (EXAFS), which are useful techniques to characterize both electronic structure and local structural properties of materials (Braun, 2017;Ankudinov & Rehr, 1997). There are few studies on the local structural properties of ZnO nanoparticles determined via the EXAFS technique, which describes the bonding lengths, bonding length disorders, coordination and atomic species of neighboring atoms around a probe atom (Jeong et al, 2008). Chiou et al (2004a) worked on the electronic structure of ZnO nanorods by angle-dependent X-ray absorption spectroscopy at the oxygen (O) K-edge and zinc (Zn) L 3 -and K-edges.…”
X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectra were recorded to investigate the electronic structure and local crystal structure of ZnO and ZnO:B powders produced via hydrothermal synthesis. ZnO and ZnO:B grow as micrometre-scale rods with hexagonal shape, as confirmed by scanning electron microscopy micrographs. The number of broken ZnO:B rods increases with increasing B concentration, as observed in the images, due to B atoms locating in between the Zn and O atoms which weakens and/or breaks the Zn–O bonds. However, no disorder within the crystallographic structure of ZnO upon B doping is observed from X-ray diffraction results, which were supported by EXAFS results. To determine the atomic locations of boron atoms in the crystal structure and their influence on the zinc atoms, EXAFS data were fitted with calculated spectra using the crystal structure parameters obtained from the crystallographic analysis of the samples. EXAFS data fitting and complementary k-weight analysis revealed the positions of the B atoms – their positions were determined to be in between the Zn and O atoms.
“…Both the ZnO-4/FTO and ZnO-4/Si Zn L 3 -edge spectra indicate the presence of wurtzite ZnO structure in that the Zn L 3 -edge peak near 1021.3 eV is associated with strong Zn 2+ signals in ZnO wurtzite structures [36,37]. The local band structures of the ZnO nanorods are expected to be different from those of the bulk ZnO because of the size effect, structural distortion, and disorder, but we have confirmed that both ZnO-4/FTO and ZnO-4/Si have the same wurtzite ZnO nanostructures [38,39].…”
ZnO nanorods have been grown on Si(001) wafer and fluorine-doped tin oxide (FTO) glass substrates for 1 and 4 h with the hydrothermal methods. The morphologies and photocatalytic activities of the ZnO nanorods were found to depend on the substrates. We investigated their properties by using spectroscopic analysis and demonstrated that the shape of nanorod and the ratios of external defects can be controlled by varying the substrates. Our experiments revealed that the nanorods grown on Si(001) have a single-crystalline wurtzite structure with (002) facets and that the number of surface oxygen defects increases with their length as the growth time increases. The nanorods grown on Si(001) have different facets, in particular wider (002) facets, and a higher ratio of the oxygen defect than the nanorods on FTO glass substrate. Moreover, the photocatalytic activities with respect to 2-aminothiophenol (2-ATP) of these nanorods were investigated with high-resolution photoemission spectroscopy (HRPES). We demonstrated that their photocatalytic activity is influenced by the ratios of surface oxygen defects, which varies with the substrate surface.
“…Both the ZnO-4/FTO and ZnO-4/Si Zn L 3 -edge spectra indicate the presence of wurtzite ZnO structure in that the Zn L 3 -edge peak near 1021.3 eV is associated with strong Zn 2+ signals in ZnO wurtzite structures [ 36 , 37 ]. The local band structures of the ZnO nanorods are expected to be different from those of the bulk ZnO because of the size effect, structural distortion, and disorder, but we have confirmed that both ZnO-4/FTO and ZnO-4/Si have the same wurtzite ZnO nanostructures [ 38 , 39 ]. Fig.…”
ZnO nanorods have been grown on Si(001) wafer and fluorine-doped tin oxide (FTO) glass substrates for 1 and 4 h with the hydrothermal methods. The morphologies and photocatalytic activities of the ZnO nanorods were found to depend on the substrates. We investigated their properties by using spectroscopic analysis and demonstrated that the shape of nanorod and the ratios of external defects can be controlled by varying the substrates. Our experiments revealed that the nanorods grown on Si(001) have a single-crystalline wurtzite structure with (002) facets and that the number of surface oxygen defects increases with their length as the growth time increases. The nanorods grown on Si(001) have different facets, in particular wider (002) facets, and a higher ratio of the oxygen defect than the nanorods on FTO glass substrate. Moreover, the photocatalytic activities with respect to 2-aminothiophenol (2-ATP) of these nanorods were investigated with high-resolution photoemission spectroscopy (HRPES). We demonstrated that their photocatalytic activity is influenced by the ratios of surface oxygen defects, which varies with the substrate surface.
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