Vanmaekelbergh<i>et al.</i>Reply

Vanmaekelbergh, D.; Roest, Aarnoud L.; Germeau, A.; Kelly, John J.; Meulenkamp, Eric A.; Allan, G.; Delerue, Christophe

doi:10.1103/physrevlett.91.169704

Cited by 5 publications

(7 citation statements)

References 3 publications

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“…5 The possibility of electron localization in reduced ZnO nanocrystals has since been heavily debated. 7,44,45 The results presented here demonstrate unambiguously that localization of excess electrons in ZnO nanocrystals can occur under specific experimental conditions. Strikingly, Zn 0 forms with only three of our five hole quenchers, and without any apparent correlation to ⟨n max ⟩.…”

Section: ■ Discussionsupporting

confidence: 65%

“…10,14−16 Among free-standing colloidal nanocrystals, the extra electrons of reduced colloidal ZnO nanocrystals are arguably the most extensively investigated. 1,2,[5][6][7][8][9][10]17 Most commonly, these electrons have been generated by photochemical oxidation of ethanol (EtOH), 5,6,[8][9][10]17 as described by eq 1. 18−20 UV illumination of ZnO nanocrystals excites an electron across the band gap and, in the presence of EtOH or other hole quenchers (ZQ), the photogenerated valence-band hole (h VB + ) can be captured irreversibly.…”

Section: ■ Introductionmentioning

confidence: 99%

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Controlling Carrier Densities in Photochemically Reduced Colloidal ZnO Nanocrystals: Size Dependence and Role of the Hole Quencher

et al. 2013

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Photodoped colloidal ZnO nanocrystals are model systems for understanding the generation and physical or chemical properties of excess delocalized charge carriers in semiconductor nanocrystals. Typically, ZnO photodoping is achieved photochemically using ethanol (EtOH) as a sacrificial reductant. Curiously, different studies have reported over an order of magnitude spread in the maximum number of conduction-band electrons that can be accumulated by photochemical oxidation of EtOH. Here, we demonstrate that this apparent discrepancy results from a strong size dependence of the average maximum number of excess electrons per nanocrystal, . We demonstrate that increases in proportion to nanocrystal volume, such that the maximum carrier density remains constant for all nanocrystal sizes. is found to be largely insensitive to precise experimental conditions such as solvent, ligands, protons or other cations, photolysis conditions, and nanocrystal or EtOH concentrations. These results reconcile the broad range of literature results obtained with EtOH as the hole quencher. Furthermore, we demonstrate that depends on the identity of the hole quencher, and is thus not an intrinsic property of the multiply reduced ZnO nanocrystals themselves. Using a series of substituted borohydride hole quenchers, we show that it is possible to increase the nanocrystal carrier densities over 4-fold relative to previous photodoping reports. When excess lithium and potassium triethylborohydrides are used in the photodoping, formation of Zn(0) is observed. The relationship between metallic Zn(0) formation and ZnO surface electron traps is discussed.

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Section: ■ Discussionsupporting

confidence: 65%

Section: ■ Introductionmentioning

confidence: 99%

Controlling Carrier Densities in Photochemically Reduced Colloidal ZnO Nanocrystals: Size Dependence and Role of the Hole Quencher

et al. 2013

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“…Localized surface plasmon resonances (LSPRs) in semiconductor nanocrystals have recently attracted broad attention, − in part because of their tunability in both energy and intensity via tunable carrier densities. Charge-carrier densities in semiconductor nanocrystals have been modulated by various techniques including remote doping, − vacancy generation, − aliovalent doping, − electrochemical doping, − and photodoping, ,,,− each offering specific advantages. For example, aliovalently doped colloidal nanocrystals such as Sn-doped In 2 O 3 (ITO) ,,− and Al-doped ZnO (AZO) ,, contain conduction-band electrons that are stable in air, making them attractive for potential aerobic applications.…”

Section: Introductionmentioning

confidence: 99%

Redox Chemistries and Plasmon Energies of Photodoped In₂O₃and Sn-Doped In₂O₃(ITO) Nanocrystals

et al. 2015

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Plasmonic doped semiconductor nanocrystals promise exciting opportunities for new technologies, but basic features of the relationships between their structures, compositions, electronic structures, and optical properties remain poorly understood. Here, we report a quantitative assessment of the impact of composition on the energies of localized surface plasmon resonances (LSPRs) in colloidal tin-doped indium oxide (Sn:In2O3, or ITO) nanocrystals. Using a combination of aliovalent doping and photodoping, the effects of added electrons and impurity ions on the energies of LSPRs in colloidal In2O3 and ITO nanocrystals have been evaluated. Photodoping allows electron densities to be tuned post-synthetically in ITO nanocrystals, independent of their Sn content. Because electrons added photochemically are easily titrated, photodoping also allows independent quantitative determination of the dependence of the LSPR energy on nanocrystal composition and changes in electron density. The data show that ITO LSPR energies are affected by both electron and Sn concentrations, with composition yielding a broader plasmon tuning range than achievable by tuning carrier densities alone. Aspects of the photodoping energetics, as well as magneto-optical properties of these ITO LSPRs, are also discussed.

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“…transitions, lying in the near IR, can be probed [14,52]. Alternatively, the quenching of the inter-band absorption upon occupation of the electron orbitals can be measured as a direct and quantitative way to monitor the orbital occupation [12,17,53]. The changes in the optical absorption spectrum of a ZnO quantum-dot solid upon electron insertion are shown in Fig.…”

Section: Quantum-dot Solids With Charge-tunable Optical and Electricamentioning

confidence: 99%

Electrochemical gating: A method to tune and monitor the (opto)electronic properties of functional materials

Vanmaekelbergh

Houtepen

Kelly

2007

Electrochimica Acta

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Electrochemical polarization of a crystalline, polymeric or nanoporous system or a single molecule may change the density of charge carriers in a controlled way, and hence the optical and electrical properties. If the system has two contacts, its electronic conductivity can be measured in situ as a function of the charge carrier density that is varied by the electrochemical potential. This is called electrochemical gating. Such investigations can reveal the nature of the charge carriers (mobile or localized) and the mechanism of electronic conduction. Here, we present a brief review of a number of systems including inorganic crystals, polymers, nanoporous quantum-dot solids, and single molecules for which electrochemical gating was used successfully in the study of the electronic properties.

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Vanmaekelberghet al.Reply

Cited by 5 publications

References 3 publications

Controlling Carrier Densities in Photochemically Reduced Colloidal ZnO Nanocrystals: Size Dependence and Role of the Hole Quencher

Controlling Carrier Densities in Photochemically Reduced Colloidal ZnO Nanocrystals: Size Dependence and Role of the Hole Quencher

Redox Chemistries and Plasmon Energies of Photodoped In₂O₃and Sn-Doped In₂O₃(ITO) Nanocrystals

Electrochemical gating: A method to tune and monitor the (opto)electronic properties of functional materials

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Vanmaekelberghet al.Reply

Cited by 5 publications

References 3 publications

Controlling Carrier Densities in Photochemically Reduced Colloidal ZnO Nanocrystals: Size Dependence and Role of the Hole Quencher

Controlling Carrier Densities in Photochemically Reduced Colloidal ZnO Nanocrystals: Size Dependence and Role of the Hole Quencher

Redox Chemistries and Plasmon Energies of Photodoped In2O3and Sn-Doped In2O3(ITO) Nanocrystals

Electrochemical gating: A method to tune and monitor the (opto)electronic properties of functional materials

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Product

Resources

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Redox Chemistries and Plasmon Energies of Photodoped In₂O₃and Sn-Doped In₂O₃(ITO) Nanocrystals