High-pressure zinc oxide phase as visible-light-active photocatalyst with narrow band gap

Razavi‐Khosroshahi, Hadi; Edalati, Kaveh; Wu, Ji; Nakashima, Y.; Arita, Makoto; Ikoma, Yoshifumi; Sadakiyo, Masaaki; Inagaki, Yuji; Staykov, Aleksandar; Yamauchi, Miho; Horita, Zenji; Fuji, Masayoshi

doi:10.1039/c7ta05262f

Cited by 112 publications

(109 citation statements)

References 61 publications

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“…The bandgaps estimated were 3.10 and 3.28 eV for ZnO and TiO 2 nanostructures, respectively. These values are in agreement with the ones reported in the literature, that is, between 3.1 and 3.3 eV for ZnO [62,63] and around 3.2 eV for anatase TiO 2 [31,64]. The ZnO bandgap value is in agreement with an analogous study, in which ZnO nanorods were fabricated on Whatman paper [1].…”

Section: Optical Characterization the Optical Bandgap Values Forsupporting

confidence: 92%

Paper-Based Nanoplatforms for Multifunctional Applications

Matias

Nunes

Pimentel

et al. 2019

Journal of Nanomaterials

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In this work, zinc oxide (ZnO) and titanium dioxide (TiO 2 ) nanostructures were grown on different cellulose paper substrates, namely, Whatman, office, and commercial hospital papers, using a hydrothermal method assisted by microwave irradiation. Pure ZnO and TiO 2 nanostructures were synthesized; however, the growth of TiO 2 above ZnO was also investigated to produce a uniform heterostructure. Continuous ZnO nanorod arrays were grown on Whatman and hospital papers; however, on office paper, the formation of nanoplates originating nanoflower structures could be observed. TiO 2 nanoparticles homogeneously covered all the substrates, in some conditions forming uniform TiO 2 films. Structural characterization was carried out by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy. The optical characterization of all the materials was carried out. The produced materials were investigated for multifunctional applications, like photocatalyst agents, bacterial inactivators, and ultraviolet (UV) sensors. To evaluate the photocatalytic activity under UV and solar radiations, rhodamine B was the model-test contaminant indicator and the best photocatalytic activity was achieved with Whatman paper. Hospital paper with TiO 2 nanoparticles showed significant antibacterial properties against Staphylococcus aureus. ZnO-based UV sensors demonstrated a responsivity of 0.61 μA W -1 .

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Section: Optical Characterization the Optical Bandgap Values Forsupporting

confidence: 92%

Paper-Based Nanoplatforms for Multifunctional Applications

Matias

Nunes

Pimentel

et al. 2019

Journal of Nanomaterials

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“…Possible synthesis routes and stability of Li-doped rocksalt ZnO. While the rocksalt phase of ZnO has been stabilized at ambient condition [16][17][18][19], doping it with Li might be challenging. Based on our results, synthesis route that starts by doping the wurtzite phase and then converts it to the rocksalt is not likely to succeed.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to the ground state wurtzite, ZnO is known to exists in the metastable zincblende and rocksalt structures [7]. The high-pressure rocksalt phase forms at about ∼9 GPa, and can be stabilized at ambient conditions in the nanocrystalline form [16][17][18] or as thin film grown on the MgO substrate with about 15 % of MgO alloyed [19,20]. This phase of ZnO is specifically relevant for our discussion because of its octahedral coordination of atoms, smaller volume (about 18 % reduction) relative to the ground state wurtzite structure and predicted higher valence band edge (∼ 1 eV closer to vacuum) than the wurtzite [21].…”

Section: Introductionmentioning

confidence: 99%

Metastable rocksalt ZnO is p -type dopable

Goyal

Stevanović

2018

Phys. Rev. Materials

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Despite decades of efforts, achieving p-type conductivity in the wide band gap ZnO in its groundstate wurtzite structure continues to be a challenge. Here we detail how p-type ZnO can be realized in the metastable, high-pressure rocksalt phase (also wide-gap) with Li as an external dopant. Using modern first-principles defect theory, we predict Li to dope the rocksalt phase p-type by preferentially substituting for Zn and introducing shallow acceptor levels. Formation of compensating donors like interstitial Li and/or hydrogen, ubiqutous in the wurtzite phase, is inhibited by the close-packed nature of the rocksalt structure, which also exhibits relatively high absolute valence band edge that promotes low hole effective mass and hole delocalization. Resulting concentrations of free holes are predicted to exceed ∼ 10 19 cm −3 under O-rich synthesis conditions while under O-poor conditions the system remains n-type dopable. In addition to revealing compelling opportunities offered by the metastable rocksalt structure in realizing a long-sought p-type ZnO our results present polymorphism as a promising route to overcoming strong doping asymmetry of wide-band gap oxides. arXiv:1802.00360v2 [cond-mat.mtrl-sci]

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“…The spectral features are compared to experimental emission spectra of ZnO random lasers and polariton lasers and we find a very good agreement in either case. [22,25,26]. The rocksalt configuration is distinguished by a tunable gap from 1.8 eV up to 6.1 eV, a gap value of 3.38 eV is typical for the monocrystal rocksalt configuration without oxygen vacancies [23,24].…”

Section: Introductionmentioning

confidence: 99%

“…These peaks give evidence that such a sample may undergo a transition towards exciton-polariton lasing rather than a transition to exciton-photon lasing, at least a coexistence of both regimes may occur. ZnO is known for excellent light-matter coupling characteristics [7,[14][15][16][17][18][19][20][21][22][23][24][25][26][27]; it is predestined for this study. It has been experimentally derived that ZnO can be considered as a Mott insulator under certain conditions [16,18].…”

Section: Introductionmentioning

confidence: 99%

Quantum Many-Body Theory for Exciton-Polaritons in Semiconductor Mie Resonators in the Non-Equilibrium

Lubatsch

Frank

2020

Applied Sciences

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We implement externally excited ZnO Mie resonators in a framework of a generalized Hubbard Hamiltonian to investigate the lifetimes of excitons and exciton-polaritons out of thermodynamical equilibrium. Our results are derived by a Floquet-Keldysh-Green's formalism with Dynamical Mean Field Theory (DMFT) and a second order iterative perturbation theory solver (IPT). We find that the Fano resonance which originates from coupling of the continuum of electronic density of states to the semiconductor Mie resonator yields polaritons with lifetimes between 0.6 ps and 1.45 ps. These results are compared to ZnO polariton lasers and to ZnO random lasers. We interpret the peaks of the exciton-polariton lifetimes in our results as a sign of gain narrowing which may lead to stable polariton lasing modes in the single excited ZnO Mie resonator. This form of gain may lead to polariton random lasing in an ensemble of ZnO Mie resonators in the non-equilibrium. PACS: 42.55.-f lasers; 71.10.-w theories and models of many-electron systems; 42.50.Hz strong-field excitation of optical transitions in quantum systems; multi-photon processes; dynamic Stark shift; 74.40+ Fluctuations; 03.75.Lm Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices, and topological excitations; 72.20.Ht high-field and nonlinear effects; 71.36.+c polaritons; 71.35.-y excitons and related phenomena; 42.55.Px semiconductor lasers, laser diodes; 89.75.-k complex systems

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High-pressure zinc oxide phase as visible-light-active photocatalyst with narrow band gap

Abstract: High-pressure rocksalt ZnO with a band gap of 1.8 eV, which can absorb visible light.

Cited by 112 publications

References 61 publications

Paper-Based Nanoplatforms for Multifunctional Applications

Paper-Based Nanoplatforms for Multifunctional Applications

Metastable rocksalt ZnO is p -type dopable

Quantum Many-Body Theory for Exciton-Polaritons in Semiconductor Mie Resonators in the Non-Equilibrium

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