| 1. |
- Antosiewicz, Tomasz, 1981, et al.
(författare)
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Oscillatory Optical Response of an Amorphous Two-Dimensional Array of Gold Nanoparticles
- 2012
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 109:24
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Tidskriftsartikel (refereegranskat)abstract
- The optical response of metallic nanoparticle arrays is dominated by localized surface plasmon excitations and is the sum of individual particle contributions modified by interparticle coupling that depends on specific array geometry. We demonstrate a so far unexplored distinct oscillatory behavior of the plasmon peak position, full width at half maximum, and extinction efficiency in large area amorphous arrays of Au nanodisks, which depend on the minimum particle center-to-center distance in the array. Amorphous arrays exhibit short-range order and are completely random at long distances. In our theoretical analysis we introduce a film of dipoles approach, within the framework of the coupled dipole approximation, which describes the array as an average particle surrounded by a continuum of dipoles with surface densities determined by the pair correlation function of the array.
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| 2. |
- Apell, Peter, 1952, et al.
(författare)
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Dynamic Depolarization in Plasmonic Metal Nanoparticles
- 2016
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Ingår i: Journal of Optics. - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 18:8
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Tidskriftsartikel (refereegranskat)abstract
- At very low photon energies most metals have a very large and negative dielectric function. For the response of a metal nanoparticle to an external field in this limit, this means that the particular choice of metal does not matter and the localized surface plasmon energy mainly depends on the shape and size of the particle. Here, we present a theoretical framework to describe this situation and unearth the interplay between the depolarization factor of the problem at hand and the dielectric function of the particle. Available experimental results compare favorably with our theoretical framework.
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| 5. |
- Iandolo, Beniamino, 1985, et al.
(författare)
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Correlating flat band and onset potentials for solar water splitting on model hematite photoanodes
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:75, s. 61021-61030
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Tidskriftsartikel (refereegranskat)abstract
- Hematite (α-Fe2O3) is a very promising material for solar water splitting that requires a high anodic potential to initiate the oxygen evolution reaction (OER). In this work, we explore the correlation between the downshift in flat band potential of hematite, Vfb, and in onset potential of OER, Vonset, caused by prolonged annealing. We observed a cathodic shift (i.e., towards lower potentials) of 200 mV of Vonset on model photoanodes consisting of ultra-thin hematite films, upon increasing the oxidation time during fabrication and without any further modifications. Detailed physical characterization, electrochemical impedance spectroscopy, and Mott-Schottky analysis revealed a quantitative correlation between the cathodic shift of Vonset and a lowering of Vfb. We identified a reduction in concentration of grain boundaries with increasing oxidation time, as the mechanism behind the observed shift of the Vfb. The approach presented here can be seen as a complementary strategy to co-catalysts and other post-fabrication treatments to lower Vonset. Moreover, it is generically applicable to photoelectrodes used to carry out oxidation and reduction half-cell reactions.
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| 6. |
- Iandolo, Beniamino, 1985, et al.
(författare)
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Faradaic efficiency of O-2 evolution on metal nanoparticle sensitized hematite photoanodes
- 2014
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 16:3, s. 1271-1275
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Tidskriftsartikel (refereegranskat)abstract
- Functionalization of transition metal oxides using metallic nanoparticles is an interesting route towards efficient photoelectrochemical hydrogen production via water splitting. Although an enhanced photocurrent in photoanodes upon functionalization with metallic nanostructures has been observed in several studies, to the best of our knowledge no measurements of the Faradaic efficiency (FE) of the oxygen evolution reaction (OER) have been reported for such systems. This work characterizes the FE on a model system consisting of ultra-thin films of hematite (Fe2O3) sensitized with Ti/Au nanodisks. Compared to bare hematite references, sensitized samples showed significantly enhanced photocurrents as well as O-2 evolution. Experimental evidence suggests that the observed enhancement was not due to photocatalytic activity of the nanodisks. The FE has been determined to be 100%, within the experimental errors, for both sensitized and reference samples. Also, this work demonstrates that the sensitized samples were stable for at least 16 hours photocurrent testing. The concepts shown in this work are generally applicable to any situation in which a semiconductor has its water splitting performance enhanced by metallic nanostructures.
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| 7. |
- Iandolo, Beniamino, 1985, et al.
(författare)
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On the mechanism for nanoplasmonic enhancement of photon to electron conversion in nanoparticle sensitized hematite films
- 2013
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 15:14, s. 4947-4954
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Tidskriftsartikel (refereegranskat)abstract
- Hematite (Fe2O3) is a promising candidate for hydrogen production via water splitting despite the difference in the characteristic lengths for photon absorption and charge carrier transport. Metallic nanoparticles supporting localized surface plasmon resonances (LSPRs), i.e. collective, non-propagating oscillations of electrons excited by an external electric field, are well-suited to improve the optoelectronic properties of hematite, in particular for ultra-thin films. Several mechanisms have been proposed to explain the observed LSPR mediated performance enhancement. In this work, the improvement of incident photon-to-electron conversion efficiency (IPCE) of ultra-thin hematite photoanodes functionalized with Au nanodisks was investigated. The improvement in IPCE at wavelengths close to the bandgap in hematite was found to correlate well with the increase in optical extinction owing to the excitation of LSPR in the nanodisks. Finite-difference time-domain calculations of the near-field distribution around the nanodisks enabled us to elucidate the mechanism behind the IPCE enhancement and its variations with the position of the plasmonic resonance with respect to the bandgap of hematite. Both were attributed to an increased charge generation close to the hematite-electrolyte interface caused by the electric field enhancement in hematite. The results presented here are directly applicable to other semiconductors with similar properties to hematite and are expected to be helpful in future design of optimized photoanodes, where, for instance, functionalization with metallic nanoparticles is combined with material doping and nanostructuring.
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| 8. |
- Iandolo, Beniamino, 1985, et al.
(författare)
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The rise of hematite: origin and strategies to reduce the high onset potential for the oxygen evolution reaction
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:33, s. 16896-16912
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Tidskriftsartikel (refereegranskat)abstract
- Hematite (alpha-Fe2O3) has emerged as a promising material for photoelectrochemical (PEC) water splitting thanks to its abundance, stability in an aqueous environment, favorable optical bandgap and position of the electronic valence band. Nevertheless, its performance as a photoanode is considerably lower than what is theoretically achievable. In particular, the high electrochemical potential usually needed to initiate water oxidation is detrimental to the prospect of using hematite for practical devices. In this review we elucidate the appealing, as well as the challenging, aspects of using hematite for PEC water splitting and focus on the recent efforts towards lowering the onset potential of water oxidation. We examine and rationalize several strategies pursued to achieve this goal involving manipulation of the hematite/electrolyte interface, as well as improving relevant properties of hematite itself.
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