Study of Charge Carrier Dynamics at Illuminated ZnO Photoanodes

Schoenmakers, G. H.; Vanmaekelbergh, and D.; Kelly, John J.

doi:10.1021/jp952392f

Cited by 65 publications

(47 citation statements)

References 32 publications

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“…On the basis of results reported [30][31][32][33] and theoretical calculations made by Xu et al [24], Zhang et al [25], Erhart et al [26], Van Dijiken et al [29] and Egelhaaf et al [34], we tentatively attribute these following emission bands to arise from. Some authors have described oxygen defect centers V O and V O + , which are located 50 and 190 meV below the band edge as the donors [35], but the observed luminescence bands in our study do not support any transitions from these donor states.…”

Section: Article In Pressmentioning

confidence: 56%

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Nano-star formation in Al-doped ZnO thin film deposited by dip-dry method and its characterization using atomic force microscopy, electron probe microscopy, photoluminescence and laser Raman spectroscopy

Behera

Acharya

2008

Journal of Luminescence

134

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Section: Article In Pressmentioning

confidence: 56%

“…Since ZnO nanoparticle has large surface to volume ratio, it is expected to be occurring at a surface site. A probable candidate for the trapping of holes is O 2À ion at the surface [30]. However, there are different arguments for the emissions observed in the ZnO nanoparticle.…”

Section: Article In Pressmentioning

confidence: 99%

Nano-star formation in Al-doped ZnO thin film deposited by dip-dry method and its characterization using atomic force microscopy, electron probe microscopy, photoluminescence and laser Raman spectroscopy

Behera

Acharya

2008

Journal of Luminescence

134

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“…In this way complex reactions can be studied both under steady-state and transient conditions. 2,3 For quantitative analysis the collection efficiency for the RRDE geometry used must be known; this is the fraction of product produced at the disk that is detected at the ring. Early theory of the RRDE was developed by Leveque and co-workers.…”

mentioning

confidence: 99%

The Rotating Ring-Ring Electrode. Theory and Experiment

Kuiken¹,

Bakkers²,

Ligthart³

et al. 2000

J. Electrochem. Soc.

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The rotating ring-disk electrode (RRDE), first described almost forty years ago by Frumkin and Nekrasov, 1 has proved an invaluable tool for the study of electrochemical reactions. The RRDE consists of two electrodes in a cylindrical holder: a disk of radius r 1 (see Fig. 1) surrounded by a concentric ring with inner and outer radii r 2 and r 3 , respectively. The area between the disk and the ring is electrochemically inactive. The electrodes face downward in solution. The rotation axis passes through the center of the disk (r ϭ 0) and is perpendicular to its surface. Products generated at the disk are swept outward by the convection caused by rotation; at the ring they can be detected electrochemically. Using a bipotentiostat one measures a disk current which is generally due to two or more electrochemical reactions. By fixing the potential of the ring it may be possible to distinguish between the products from the disk, i.e., the ring current at a given potential is a measure for the rate of production of a specific product at the disk. In this way complex reactions can be studied both under steady-state and transient conditions. 2,3 For quantitative analysis the collection efficiency for the RRDE geometry used must be known; this is the fraction of product produced at the disk that is detected at the ring. Early theory of the RRDE was developed by Leveque and co-workers. 4,5 Albery 6 and Albery and Bruckenstein, 7 using boundary layer theory and applying the Levèque approximation to describe mass transport, succeeded in setting up a complete and accurate theory for determining the collection efficiency. The theory has been confirmed by experiments in which a single reaction occurs at the disk and its product is measured at the ring. 7 A survey of work on the RRDE is to be found in books by Albery and Hitchman 2 and Pleskov and Filinovski. 8 As part of a project devoted to etching under well-defined hydrodynamic conditions we were interested in etching a ring in a masked rotating disk. In order to follow the dissolution reaction in the ring shaped opening we use an outer concentric ring to detect the etch products. This is, in fact, a rotating ring-ring electrode (RRRE) geometry. To characterize this system we first considered the case in which a simple redox reaction occurs at the inner ring, i.e., no etching occurs. In this paper, we show how the theory of Albery et al. can be extended to cover the RRRE and we derive an expression for the collection efficiency as a function of the ring geometry. Details of the mathematical treatment are presented in a number of Appendices. The experimental setup used to check the validity of the theory is described in the experimental section together with the experimental results.Unstable products or intermediates formed at the disk of an RRDE can be detected at the ring. 2 Clearly, the transit time of the species, i.e., the time required for passing from disk to ring, must be shorter than the lifetime of the species. In a separate Appendix, we show that the RRRE can offer...

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“…The origin of the enhanced NBE emission in core-shell NRAs can be explained by the following model. For an uncoated ZnO NRAs, oxygen molecules adsorb near the surface of ZnO NRAs, trap the free electrons from conduction band, and become the charged oxygen molecules ( [21]. This widens the depletion layer, leading to an upward band bending around the surface [22].…”

Section: Methodsmentioning

confidence: 99%

“…For the bare ZnO NRAs, the surface built-in electric field separates the photogenerated electron-hole pairs and accumulates holes at the surface, leading to lower radiative transition. With increasing temperature, more accumulated holes can obtain thermal energy to overcome the potential resulted from the surface band banding [21], leading to increasing probability of radiative recombination. As a result, the PL intensity was decreased less sensitively with increasing temperature.…”

Section: Methodsmentioning

confidence: 99%

ZnO/Al₂O₃ Core-shell Nanorod Arrays: Processing, Structural Characterization, and Luminescent Property

et al. 2008

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We reported the aqueous chemical method to fabricate the well-aligned ZnO/Al 2 O 3 coreshell nanorod arrays (NRAs). The shell is composed of α-Al 2 O 3 nanocrystals in amorphous Al 2 O 3 layers. The photoluminescence (PL) measurements showed that the enhancement of nearband-edge emission in ZnO NRAs arrays due to the addition of Al 2 O 3 shell was observed. The Al 2 O 3 shell layer resulting in flatband effect near ZnO surface leads to a stronger overlap of the wavefunctions of electrons and holes in the ZnO core, further enhancing the NBE emission.

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Study of Charge Carrier Dynamics at Illuminated ZnO Photoanodes

Cited by 65 publications

References 32 publications

Nano-star formation in Al-doped ZnO thin film deposited by dip-dry method and its characterization using atomic force microscopy, electron probe microscopy, photoluminescence and laser Raman spectroscopy

Nano-star formation in Al-doped ZnO thin film deposited by dip-dry method and its characterization using atomic force microscopy, electron probe microscopy, photoluminescence and laser Raman spectroscopy

The Rotating Ring-Ring Electrode. Theory and Experiment

ZnO/Al₂O₃ Core-shell Nanorod Arrays: Processing, Structural Characterization, and Luminescent Property

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Study of Charge Carrier Dynamics at Illuminated ZnO Photoanodes

Cited by 65 publications

References 32 publications

Nano-star formation in Al-doped ZnO thin film deposited by dip-dry method and its characterization using atomic force microscopy, electron probe microscopy, photoluminescence and laser Raman spectroscopy

Nano-star formation in Al-doped ZnO thin film deposited by dip-dry method and its characterization using atomic force microscopy, electron probe microscopy, photoluminescence and laser Raman spectroscopy

The Rotating Ring-Ring Electrode. Theory and Experiment

ZnO/Al2O3 Core-shell Nanorod Arrays: Processing, Structural Characterization, and Luminescent Property

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Product

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ZnO/Al₂O₃ Core-shell Nanorod Arrays: Processing, Structural Characterization, and Luminescent Property