Oxygen vacancy induced band gap narrowing of ZnO nanostructures by an electrochemically active biofilm

Ansari, Sajid Ali; Kalathil, Shafeer; Nisar, Ambreen; Lee, Jintae

doi:10.1039/c3nr02678g

Cited by 564 publications

(343 citation statements)

References 53 publications

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“…[53][54][55] Due to the fact that TiO 2 and ZnO possess typical oxygen related defects, the defect sites are subjected to the chemisorption of the above ions while sharing the lattice electron(s). [53][54][55] Furthermore, the grain boundaries (as seen in the TEM images) are obvious locations for electron decient species to chemisorb. Depending on the availability of free electron(s), the sharing can be partial with the above species which has produced relatively broad binding energies peaking at $532.2 eV or $531.9 eV.…”

Section: Photocatalytic Activity Of Core-shell Heterojunction Nanobersmentioning

confidence: 99%

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

et al. 2014

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Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO 2 in two combinations where only the 'shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO 2 CSHJ, e/h pairs are created mainly in TiO 2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the 'shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO 2 -ZnO CSHJ. The results further revealed that the TiO 2 -ZnO CSHJ shows $1.6 times faster PCA when compared to the ZnO-TiO 2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes.

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Section: Photocatalytic Activity Of Core-shell Heterojunction Nanobersmentioning

confidence: 99%

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

et al. 2014

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“…However, the band gap energy variations seen could be caused by defects, crystal structure, and temperature of MO nanoparticles. 41,42 Photoexcitation responses can also be confirmed using UV and Fourier transforminfrared spectroscopy (FT-IR). 43 The dual UV-MO nanoparticle hybrid system can be applied for the disinfection of bacteria and viruses.…”

mentioning

confidence: 99%

Dual UV irradiation-based metal oxide nanoparticles for enhanced antimicrobial activity in <em>Escherichia coli</em> and M13 bacteriophage

Jin¹,

Hwang²,

Lee³

et al. 2017

IJN

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Metal oxide (MO) nanoparticles have been studied as nano-antibiotics due to their antimicrobial activities even in antibiotic-resistant microorganisms. We hypothesized that a hybrid system of dual UV irradiation and MO nanoparticles would have enhanced antimicrobial activities compared with UV or MO nanoparticles alone. In this study, nanoparticles of ZnO, ZnTiO 3 , MgO, and CuO were selected as model nanoparticles. A dual UV collimated beam device of UV-A and UV-C was developed depending upon the lamp divided by coating. Physicochemical properties of MO nanoparticles were determined using powder X-ray diffractometry (PXRD), Brunauer-Emmett-Teller analysis, and field emission-scanning electron microscopy with energy-dispersive X-ray spectroscopy. Atomic force microscopy with an electrostatic force microscopy mode was used to confirm the surface topology and electrostatic characteristics after dual UV irradiation. For antimicrobial activity test, MO nanoparticles under dual UV irradiation were applied to Escherichia coli and M13 bacteriophage (phage). The UV-A and UV-C showed differential intensities in the coated and uncoated areas (UV-A, coated = uncoated; UV-C, coated ≪ uncoated). MO nanoparticles showed sharp peaks in PXRD patterns, matched to pure materials. Their primary particle sizes were less than 100 nm with irregular shapes, which had an 8.6~25.6 m 2 /g of specific surface area with mesopores of 22~262 nm. The electrostatic properties of MO nanoparticles were modulated after UV irradiation. ZnO, MgO, and CuO nanoparticles, except ZnTiO 3 nanoparticles, showed antibacterial effects on E. coli . Antimicrobial effects on E. coli and phages were also enhanced after cyclic exposure of dual UV and MO nanoparticle treatment using the uncoated area, except ZnO nanoparticles. Our results demonstrate that dual UV-MO nanoparticle hybrid system has a potential for disinfection. We anticipate that it can be developed as a next-generation disinfection system in pharmaceutical industries and water purification systems.

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“…A previous study reporting the synthesis of graphene-hybridized ZnO triangles attributed its increased output photocurrent density of 1.26 mA·cm −2 (compared to 0.321 mA·cm −2 ) to an increase of oxygen defects in the ZnO triangle nanostructure [68]. Other studies have indicated that the presence of oxygen vacancies narrows the band gap of ZnO [69,70], leading to reduced overpotential for photoexcitation of electrons. Thus, the light absorption properties of ZnO is tunable by controlling the intrinsic defect states [71].…”

Section: Modifications Of Zno For Enhanced Photocatalytic Water Oxidamentioning

confidence: 99%

Photocatalytic Water Oxidation on ZnO: A Review

2017

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Abstract:The investigation of the water oxidation mechanism on photocatalytic semiconductor surfaces has gained much attention for its potential to unlock the technological limitations of producing H 2 from carbon-free sources, i.e., H 2 O. This review seeks to highlight the available scientific and fundamental understanding towards the water oxidation mechanism on ZnO surfaces, as well as present a summary on the modification strategies carried out to increase the photocatalytic response of ZnO.

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Oxygen vacancy induced band gap narrowing of ZnO nanostructures by an electrochemically active biofilm

Cited by 564 publications

References 53 publications

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

Selective isolation of the electron or hole in photocatalysis: ZnO–TiO2 and TiO2–ZnO core–shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

Dual UV irradiation-based metal oxide nanoparticles for enhanced antimicrobial activity in <em>Escherichia coli</em> and M13 bacteriophage

Photocatalytic Water Oxidation on ZnO: A Review

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