Improvement of the thermoelectric properties of a MoO₃ monolayer through oxygen vacancies

• Wenwen Zheng,
• Wei Cao,
• Ziyu Wang,
• Huixiong Deng,
• Jing Shi and
• Rui Xiong

Beilstein J. Nanotechnol. 2019, 10, 2031–2038, doi:10.3762/bjnano.10.199

• , China 10.3762/bjnano.10.199 Abstract We have investigated the thermoelectric properties of a pristine MoO3 monolayer and its defective structures with different oxygen vacancies using first-principles methods combined with Boltzmann transport theory. Our results show that the thermoelectric properties

• oxygen vacancies leads to a sharp peak near the Fermi level in the density of states. This proves to be an effective way to enhance the ZT values of the MoO3 monolayer. The increased ZT values can reach 0.84 (x-axis) and 0.12 (y-axis) at 300 K. Keywords: Boltzmann transport theory; first-principles

• calculations; molybdenum trioxides; MoO3 monolayer; oxygen vacancies; thermoelectric properties; Introduction Thermoelectric materials that can directly convert temperature gradients to voltage gradients and vice versa provide a valid strategy to mitigate the global energy crisis. Owing to the unique ability

Magnetic properties of biofunctionalized iron oxide nanoparticles as magnetic resonance imaging contrast agents

• Natalia E. Gervits,
• Andrey A. Gippius,
• Alexey V. Tkachev,
• Evgeniy I. Demikhov,
• Sergey S. Starchikov,
• Igor S. Lyubutin,
• Alexander L. Vasiliev,
• Vladimir P. Chekhonin,
• Maxim A. Abakumov,
• Alevtina S. Semkina and
• Alexander G. Mazhuga

Beilstein J. Nanotechnol. 2019, 10, 1964–1972, doi:10.3762/bjnano.10.193

• -site) and octahedral [B-site]. The cationic distribution can be represented as: (Fe3+)A[Fe2.5+2]BO4 in the case of magnetite and (Fe3+)A[Fe3+5/3□1/3]BO4 for maghemite, where □ denotes vacancies. The fast electron exchange between the Fe3+ and Fe2+ ions in the B-sites of magnetite leads to an average

Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation

• Dominik Wrana,
• Karol Cieślik,
• Wojciech Belza,
• Christian Rodenbücher,
• Krzysztof Szot and
• Franciszek Krok

Beilstein J. Nanotechnol. 2019, 10, 1596–1607, doi:10.3762/bjnano.10.155

• conductivity. Here, a huge advantage over other materials is the possibility of oxides that self-dope via the introduction of oxygen vacancies [13], which is also a reason why there are not many reliable experimental studies on the work function of transition metal oxides (with one notable exception [14

• beforehand, resulting in the formation of a high concentration of oxygen vacancies. Therefore, the conductivity is much higher than that of a pristine single crystal, which has been estimated via a comparable LC-AFM study to be around 10−16 S [28]. Here the observed changes of conductivity on the surface

• comparable conductivity but notably different work functions. The reason behind this is that although undoped SrTiO3(100) is a band insulator, it could be easily self-doped with oxygen vacancies upon thermal reduction [28][30]. Reduction preferentially occurs at the surface, resulting in the reconstruction

Rapid thermal annealing for high-quality ITO thin films deposited by radio-frequency magnetron sputtering

• Petronela Prepelita,
• Ionel Stavarache,
• Doina Craciun,
• Florin Garoi,
• Catalin Negrila,
• Beatrice Gabriela Sbarcea and
• Valentin Craciun

Beilstein J. Nanotechnol. 2019, 10, 1511–1522, doi:10.3762/bjnano.10.149

• near the valence band (such as oxygen interstitials and indium vacancies) and the number of states increases with increasing oxygen flow. A poor crystalline quality with abundant structural defects leads to effective compensation of doping [33][48]. The metallic nature of the highly conductive ITO

Direct observation of oxygen-vacancy formation and structural changes in Bi₂WO₆ nanoflakes induced by electron irradiation

• Hong-long Shi,
• Bin Zou,
• Zi-an Li,
• Min-ting Luo and
• Wen-zhong Wang

Beilstein J. Nanotechnol. 2019, 10, 1434–1442, doi:10.3762/bjnano.10.141

• prominent role of oxygen vacancies in the photocatalytic performance of bismuth tungsten oxides is well recognized, while the underlying formation mechanisms remain poorly understood. Here, we use the transmission electron microscopy to investigate the formation of oxygen vacancies and the structural

• evolution of Bi2WO6 under in situ electron irradiation. Our experimental results reveal that under 200 keV electron irradiation, the breaking of relatively weak Bi–O bonds leads to the formation of oxygen vacancies in Bi2WO6. With prolonged electron irradiation, the reduced Bi cations tend to form Bi

• . Keywords: bismuth tungsten oxide; electron diffraction; electron irradiation; nanoflakes; oxygen vacancies; Introduction Bi2WO6 has drawn great interest regarding its physical properties such as the piezoelectric effect and ferroelectricity with large spontaneous polarization and high Curie temperature [1

Kelvin probe force microscopy of the nanoscale electrical surface potential barrier of metal/semiconductor interfaces in ambient atmosphere

• Petr Knotek,
• Tomáš Plecháček,
• Jan Smolík,
• Petr Kutálek,
• Filip Dvořák,
• Milan Vlček,
• Jiří Navrátil and
• Čestmír Drašar

Beilstein J. Nanotechnol. 2019, 10, 1401–1411, doi:10.3762/bjnano.10.138

• nanometers for SiO2 on Si [51][52]). In our case it is increased by the electric field and good oxygen mobility in BiOx due to the formation of charged Bi vacancies [59][60]. This assumption is in good agreement with the observed increase of the cut-in potential barrier upon thinning of the Au layer (see

Gas sensing properties of individual SnO₂ nanowires and SnO₂ sol–gel nanocomposites

• Alexey V. Shaposhnik,
• Dmitry A. Shaposhnik,
• Sergey Yu. Turishchev,
• Olga A. Chuvenkova,
• Stanislav V. Ryabtsev,
• Alexey A. Vasiliev,
• Xavier Vilanova,
• Francisco Hernandez-Ramirez and
• Joan R. Morante

Beilstein J. Nanotechnol. 2019, 10, 1380–1390, doi:10.3762/bjnano.10.136

• nanowires, which is usually connected with the presence of oxygen vacancies [35][37][38]. The decrease in the half-widths and the increase in the relative intensity of the peaks for each of the features observed around 490 eV (main absorption edge of the SnO2) provides evidence for a more ordered structure

• structure density of states is typical of native SnO2-x oxide covering the surface of pure metallic tin foils [37][38] and was confirmed for SnO2 powder samples by the presence of noticeable amounts of oxygen vacancies (Figure 7). XANES oxygen lines near K-edge spectra are presented in Figure 8. The fine

• , powder particles may contain noticeable amounts of oxygen vacancies in their volume. This assumption moves the electronic structure of SnO2 powder particles close to the bulk (core) of natural SnO2-x oxides as confirmed by the XANES Sn M4,5 results (see Figure 7). After calcination, followed by

Imaging the surface potential at the steps on the rutile TiO₂(110) surface by Kelvin probe force microscopy

• Masato Miyazaki,
• Huan Fei Wen,
• Quanzhen Zhang,
• Yuuki Adachi,
• Jan Brndiar,
• Ivan Štich,
• Yan Jun Li and
• Yasuhiro Sugawara

Beilstein J. Nanotechnol. 2019, 10, 1228–1236, doi:10.3762/bjnano.10.122

• [1][2][3][4][5][6][7]. The catalytic activity can be enhanced by the presence of defects, such as oxygen vacancies (Ov), Ti interstitials (Tiint) [8], and crystal steps. TiO2 is an n-type semiconductor because of these defects. In addition, reactive oxygen species, such as OH and H2O2 (compounds with

Pure and mixed ordered monolayers of tetracyano-2,6-naphthoquinodimethane and hexathiapentacene on the Ag(100) surface

• Robert Harbers,
• Timo Heepenstrick,
• Dmitrii F. Perepichka and
• Moritz Sokolowski

Beilstein J. Nanotechnol. 2019, 10, 1188–1199, doi:10.3762/bjnano.10.118

• example. The four symmetry-equivalent domains are marked by A to D. The molecular rows are well visible. The domains exhibit local defects, mostly vacancies, where single molecules are missing. For this structure, STM images of good quality with a low level of noise were obtained easily. We interpret this

Photoactive nanoarchitectures based on clays incorporating TiO₂ and ZnO nanoparticles

• Eduardo Ruiz-Hitzky,
• Pilar Aranda,
• Marwa Akkari,
• Nithima Khaorapapong and
• Makoto Ogawa

Beilstein J. Nanotechnol. 2019, 10, 1140–1156, doi:10.3762/bjnano.10.114

• visible wavelengths (blue and green emission at around 436–438 nm and 544–548 nm) of ZnO hybridized with CTA-smectites varies depending on the ZnO loading. This was attributed to defects, such as oxygen vacancies in ZnO, and trapped surface charges. The photoluminescence intensity of ZnO in saponite and

Quantitative analysis of annealing-induced instabilities of photo-leakage current and negative-bias-illumination-stress in a-InGaZnO thin-film transistors

• Dapeng Wang and
• Mamoru Furuta

Beilstein J. Nanotechnol. 2019, 10, 1125–1130, doi:10.3762/bjnano.10.112

• higher-energy light irradiation, demonstrating that the generated ionized oxygen vacancies (VO+/VO2+) are neutralized by capturing electrons [8]. However, SS degradation still can be observed in the 300 °C-annealed TFT under the irradiation with short-wavelength light (below 430 nm), indicating that

Synthesis and characterization of quaternary La(Sr)S–TaS₂ misfit-layered nanotubes

• Marco Serra,
• Erumpukuthickal Ashokkumar Anumol,
• Dalit Stolovas,
• Iddo Pinkas,
• Ernesto Joselevich,
• Reshef Tenne,
• Andrey Enyashin and
• Francis Leonard Deepak

Beilstein J. Nanotechnol. 2019, 10, 1112–1124, doi:10.3762/bjnano.10.111

• vacancies in the parent MLC compound. For smaller amounts of lanthanum atoms (i.e., larger Sr content in the MS sublattice), the charge transfer to the CrS2 slab becomes smaller. Therefore, the hexagonal (layered) phase of CrS2 becomes unstable beyond 20 atom % Sr and the MLC vanishes. While the parent

Electronic and magnetic properties of doped black phosphorene with concentration dependence

• Ke Wang,
• Hai Wang,
• Min Zhang,
• Yan Liu and
• Wei Zhao

Beilstein J. Nanotechnol. 2019, 10, 993–1001, doi:10.3762/bjnano.10.100

• experimentally demonstrated that substitutional doping of TMDs could be achieved by filling the vacancies observed in CVD-grown monolayer TMDs [18]. Liu et al. [19] prepared epitaxial copper-doped ZnO films and observed that the substitution of Cu for Zn and the presence of strong Cu–Zn–O bonds are necessary for

Rapid, ultraviolet-induced, reversibly switchable wettability of superhydrophobic/superhydrophilic surfaces

• Yunlu Pan,
• Wenting Kong,
• Bharat Bhushan and
• Xuezeng Zhao

Beilstein J. Nanotechnol. 2019, 10, 866–873, doi:10.3762/bjnano.10.87

• are generated on the TiO2 surfaces under UV illumination. The holes lead to the production of oxygen vacancies to enhance the adsorption of hydroxy groups, while the hydroxy groups are replaced by oxygen atoms that have a stronger bond on the defect sites during heating process. However, the change in

On the transformation of “zincone”-like into porous ZnO thin films from sub-saturated plasma enhanced atomic layer deposition

• Alberto Perrotta,
• Julian Pilz,
• Stefan Pachmajer,
• Antonella Milella and
• Anna Maria Coclite

Beilstein J. Nanotechnol. 2019, 10, 746–759, doi:10.3762/bjnano.10.74

• (vacancies). The latter peak is also attributed to the formation of metal carbonates, in line with the FTIR results and the literature values [60]. Finally, the peak at 529.8 eV was attributed to lattice O–Zn bonds [56]. Increasing the plasma time led to the decrease and eventual disappearance of the pure

• spectra confirm the removal of the carbon functionalities and the calcined layers showed an O/Zn ratio of 1.0 ± 0.1 (Table 1). The oxygen peaks were decomposed into two contributions, assigned to the oxygen–zinc bonds in the oxide lattice (O–Zn, 529.8 eV), and zinc hydroxides and/or oxygen vacancies (Zn

Review of time-resolved non-contact electrostatic force microscopy techniques with applications to ionic transport measurements

• Aaron Mascaro,
• Yoichi Miyahara,
• Tyler Enright,
• Omur E. Dagdeviren and
• Peter Grütter

Beilstein J. Nanotechnol. 2019, 10, 617–633, doi:10.3762/bjnano.10.62

• a phase-locked loop (PLL). This was first performed by Bennewitz et al. to measure the mobility of F− vacancies in a CaF2 crystal [27]. Schirmeisen et al. later improved the technique by performing the measurements at various temperatures to extract the activation energy for ionic transport in Li

Mo-doped boron nitride monolayer as a promising single-atom electrocatalyst for CO₂ conversion

• Qianyi Cui,
• Gangqiang Qin,
• Weihua Wang,
• Lixiang Sun,
• Aijun Du and
• Qiao Sun

Beilstein J. Nanotechnol. 2019, 10, 540–548, doi:10.3762/bjnano.10.55

• ), including Sc to Zn, Mo, Ru, Rh, Pd and Ag, supported on a boron nitride (BN) monolayer with boron vacancies, were investigated as electrocatalysts for the CO2 reduction reaction (CRR) using comprehensive density functional theory (DFT) calculations. The results demonstrate that a single-Mo-atom-doped boron

• refractory nature [11][35][36][37][38][39][40][41]. Moreover, BN nanomaterials have been used as superior substrates for doping various transition metals by electron beam irradiation [42] or solvent exfoliation [43] to form selected point defects, which are preferred to growing specific boron vacancies [42

Choosing a substrate for the ion irradiation of two-dimensional materials

• Egor A. Kolesov

Beilstein J. Nanotechnol. 2019, 10, 531–539, doi:10.3762/bjnano.10.54

• vacancy generation event involves chalcogen atom removal) [23]. If the fluence is enough, multiple generated vacancies can subsequently merge through the migration processes [15][24], leading to a creation of more complex defects. Additionally, the incident ion can become embedded into the 2D material

Ceria/polymer nanocontainers for high-performance encapsulation of fluorophores

• Kartheek Katta,
• Dmitry Busko,
• Yuri Avlasevich,
• Katharina Landfester,
• Stanislav Baluschev and
• Rafael Muñoz-Espí

Beilstein J. Nanotechnol. 2019, 10, 522–530, doi:10.3762/bjnano.10.53

• combine biocompatibility with a high oxygen-scavenging ability. Cerium oxide is a lanthanide metal oxide with a redox potential behavior that can easily switch between cerium(IV) and cerium(III) and has the capability to leave oxygen vacancies in the crystal lattice [39]. Cerium(IV) oxide exhibits

• , which yielded the hybrid sample NC-CeO2. The fluorescence intensity is higher than for nanocapsules synthesized under ambient conditions without CeO2, but also even higher than for the sample NC(Ar) prepared under argon atmosphere. The oxygen vacancies present in the structure of cerium(IV) oxide

Sub-wavelength waveguide properties of 1D and surface-functionalized SnO₂ nanostructures of various morphologies

• Venkataramana Bonu,
• Binaya Kumar Sahu,
• Arindam Das,
• Sankarakumar Amirthapandian,
• Sandip Dhara and
• Harish C. Barshilia

Beilstein J. Nanotechnol. 2019, 10, 379–388, doi:10.3762/bjnano.10.37

• usual yellow-red luminescence (owing to bridging oxygen vacancies; OB) of the SnO2 is significantly suppressed and the luminescence appearing around the blue spectrum (owing to in-plane O vacancies; OP) becomes strong [13]. Interestingly, with surface functionalization, luminescence tuning is

• . Then, surface passivation takes place leading to suppression of the luminescence related to the OB vacancy sites. Moreover, luminescence from OP arises at high energy relative to the luminescence OB vacancies. We previously reported a detailed study on OTS functionalization of the SnO2 NPs [19]. It is

• 2.6 eV are assigned to band edge transitions. Earlier, it was shown from DFT calculations using an all-electron Gaussian approximation that formation of an acceptor state close to 1 eV above the valence band occurs due to the stable oxygen vacancies [31]. Thus, the above mentioned studies point out

Site-specific growth of oriented ZnO nanocrystal arrays

• Rekha Bai,
• Dinesh K. Pandya,
• Sujeet Chaudhary,
• Veer Dhaka,
• Vladislav Khayrudinov,
• Jori Lemettinen,
• Christoffer Kauppinen and
• Harri Lipsanen

Beilstein J. Nanotechnol. 2019, 10, 274–280, doi:10.3762/bjnano.10.26

• may in turn impact the physical properties on account of the known role of oxygen vacancies and defects on electron transport behavior of ZnO [26][27]. But in our case no such high temperature processing is required at any stage. Cho et al. [17] have used a solution method with tri-potassium citrate

Zn/F-doped tin oxide nanoparticles synthesized by laser pyrolysis: structural and optical properties

• Florian Dumitrache,
• Iuliana P. Morjan,
• Elena Dutu,
• Ion Morjan,
• Claudiu Teodor Fleaca,
• Monica Scarisoreanu,
• Alina Ilie,
• Marius Dumitru,
• Cristian Mihailescu,
• Adriana Smarandache and
• Gabriel Prodan

Beilstein J. Nanotechnol. 2019, 10, 9–21, doi:10.3762/bjnano.10.2

• SnO2 in its undoped form is an n-type semiconductor with a direct bandgap of 3.6 eV at room temperature. Its n-type conductivity is due to oxygen vacancies in its rutile structure. The bandgap, starting from the bulk value, increases as the size of the nanocrystal decreases, due to electron confinement

Nanostructure-induced performance degradation of WO₃·nH₂O for energy conversion and storage devices

• Zhenyin Hai,
• Mohammad Karbalaei Akbari,
• Zihan Wei,
• Danfeng Cui,
• Chenyang Xue,
• Hongyan Xu,
• Philippe M. Heynderickx,
• Francis Verpoort and
• Serge Zhuiykov

Beilstein J. Nanotechnol. 2018, 9, 2845–2854, doi:10.3762/bjnano.9.265

• samples originate from W5+ ions in the lattice, which reveals the formation of a few oxygen vacancies [29][46]. The O 1s spectra for all samples in Figure 5c depict two peaks with one main peak from the lattice oxygen, OL, and another from the oxygen in water molecules, OH2O [47][48]. With increasing

Graphene-enhanced metal oxide gas sensors at room temperature: a review

• Dongjin Sun,
• Yifan Luo,
• Marc Debliquy and
• Chao Zhang

Beilstein J. Nanotechnol. 2018, 9, 2832–2844, doi:10.3762/bjnano.9.264

• -sensing material. Therefore, further reduction of GO is necessary and the product after reduction is called reduced graphene oxide (rGO). Some oxygen functional groups remain after the reduction, some defects and vacancies are generated during the reduction, which are beneficial for the gas adsorption [13

• concentrations of NH3 and responded dramatically, which could be ascribed to the p–n heterojunctions formed between ZnO and rGO. However, the influence of humidity on the sensor response was not negligible due to the residual oxygen (high hydrophilicity) on rGO and the active sites (oxygen vacancies) on ZnO

Variation of the photoluminescence spectrum of InAs/GaAs heterostructures grown by ion-beam deposition

• Alexander S. Pashchenko,
• Leonid S. Lunin,
• Eleonora M. Danilina and
• Sergei N. Chebotarev

Beilstein J. Nanotechnol. 2018, 9, 2794–2801, doi:10.3762/bjnano.9.261

• Bi = 148 pm and In = 142 pm atoms are very close. Therefore, in the InAs QD growth process on the GaAs1−xBix surface, In adatom surface diffusion can be realized both through substituting Ga or Bi vacancies. Increase of QD heights in the InAs/GaAs0.95Bi0.05 heterosystem is an indirect demonstration