Metal ion linked multilayers on mesoporous substrates: Energy/electron transfer, photon upconversion, and more

Robb, Alex J.; Knorr, Erica S.; Watson, Noelle; Hanson, Kenneth

doi:10.1016/j.jphotochem.2019.112291

Cited by 16 publications

(20 citation statements)

References 124 publications

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“…[1][2][3] Environmental and economic benefits of maximising upconversion quantum yields are evident, as TTA-UC has been identified as a method to increase solar cell efficiencies beyond that of the Shockley-Queisser limit. [4][5][6] Furthermore, TTA-UC has been successfully demonstrated in many photovoltaic, [6][7][8][9][10][11][12][13][14][15][16] photocatalytic, [17][18][19] and biosensing [20][21][22] applications, often where achieving maximum upconversion quantum yield (QY) is a figure of merit. A second figure of merit is the threshold intensity (I th ).…”

Section: Introductionmentioning

confidence: 99%

Modulating TTA efficiency through control of high energy triplet states

Carrod

Cravcenco

et al. 2022

J. Mater. Chem. C

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Section: Introductionmentioning

confidence: 99%

Modulating TTA efficiency through control of high energy triplet states

Carrod

Cravcenco

et al. 2022

J. Mater. Chem. C

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“…The multilayers are composed of nanoparticle TiO 2 films of varying porosity, zero to three layers of p -terphenyl diphosphonic acid ( B ) and Zn II linking ion, and Ru(bpy) 2 ((4,4′-PO 3 H 2 ) 2 bpy)]Cl 2 ( RuP ) as the dye molecule. Zn(II) was selected as the linking ion, as opposed to Zr(IV) mentioned above, to remain consistent with the previously published B -containing multilayer films . However, it is worth noting that it has been shown that Zn(II)- and Zr(IV)-containing multilayers exhibit similar photophysical and electrochemical properties …”

Section: Introductionmentioning

confidence: 83%

“…The assembly of multiple molecular components on an inorganic substrate offers a powerful means of controlling energy and electron events, which are critical to a range of applications including organic and hybrid electronics, biosensing, electrochromics, and so on. Of the assembly strategies (e.g., host–guest, codeposition, and hydrogen bonding), metal ion-linked multilayers are appealing because they are relatively easy to prepare via step-wise soaking, the components can be independently synthesized, the loading of two or more species is not surface area-limited, and they can provide directional control over energy and electron transfer toward and away from the surface. , …”

Section: Introductionmentioning

confidence: 99%

Role of Metal Ion-Linked Multilayer Thickness and Substrate Porosity in Surface Loading, Diffusion, and Solar Energy Conversion

Robb

Miles

Salpage

et al. 2020

ACS Appl. Mater. Interfaces

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Metal ion-linked multilayers offer an easily prepared and modular architecture for controlling energy and electron transfer events on nanoparticle, metal oxide films. However, unlike with planar electrodes, the mesoporous nature of the films inherently limits both the thickness of the multilayer and subsequent diffusion through the pores. Here, we systematically investigated the role of TiO 2 nanoparticle film porosity and metal ion-linked multilayer thickness in surface loading, through-pore diffusion, and overall device performance. The TiO 2 porosity was controlled by varying TiO 2 sintering times. Molecular multilayer thickness was controlled through assembling Zn II -linked bridging molecules (B = p-terphenyl diphosphonic acid) between the metal oxide and the Ru(bpy) 2 ((4,4′-PO 3 H 2 ) 2 bpy)]Cl 2 dye (RuP), thus producing TiO 2 -(B n )-RuP films. Using attenuated total reflectance infrared absorption and UV−vis spectroscopy, we observed that at least two molecular layers (i.e., TiO 2 -B 2 or TiO 2 -B 1 -RuP) could be formed on all films but subsequent loading was dependent on the porosity of the TiO 2 . Rough estimates indicate that in a film with 34 nm average pore diameter, the maximum multilayer film thickness is on the order of 4.6−6 nm, which decreases with decreasing pore size. These films were then incorporated as the photoanodes in dye-sensitized solar cells with cobalt(II/III)tris(4,4′-di-tert-butyl-2,2′-bipyridine) as a redox mediator. In agreement with the surface-loading studies, electrochemical impedance spectroscopy measurements indicate that mediator diffusion is significantly hindered in films with thicker multilayers and less porous TiO 2 . Collectively, these results show that care must be taken to balance multilayer thickness, substrate porosity, and size of the mediator in designing and maximizing the performance of new multilayer energy and electron management architectures.

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“…The free electron concentration in a TCO is not appreciably influenced by excited-state injection. Nevertheless, TCOs support long-lived charge separation when excited-state electron transfer occurs remote to the surface with free energy gradients that direct the electron toward, and the oxidizing equivalent away, from the conductor. − A layer-by-layer assembly technique with Zr IV Lewis acids was utilized to spatially arrange redox active molecular components on mesoporous thin films of In 2 O 3 :Sn (nITO) nanocrystallites. − For the full molecular assembly shown with at terminal triphenyl amine (TPA), long-lived charge separation was achieved with a quantum yield of 0.2 and first-order recombination kinetics ( k = 1.5 s –1 ) to TPA + , Figure a and b . This data support the notion that first-order recombination may be more commonly observed with weakly coupled acceptors located outside of the electric double layer. , Comparative studies revealed that the viologen acceptor and the iron donor were required for such long-lived charge separation.…”

Section: Discussion and Perspectivesmentioning

confidence: 99%

Perspectives on Dye Sensitization of Nanocrystalline Mesoporous Thin Films

Sampaio

Schneider

et al. 2020

J. Am. Chem. Soc.

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Recent advances in our mechanistic understanding of dye-sensitized electron transfer reactions occurring at metal oxide interfaces are described. These advances were enabled by the advent of mesoporous thin films, comprised of anatase TiO 2 nanocrystallites, that are amenable to spectroscopic and electrochemical characterization in unprecedented molecular-level detail. The metal-to-ligand charge transfer (MLCT) excited states of Ru polypyridyl compounds serve as the dye sensitizers. Excited-state injection often occurs on ultrafast time scales with yields that can be tuned from unity to near zero through modification of the sensitizer or the electrolyte composition. Transport of the injected electron and the oxidized sensitizer (hole hopping) are both operative in the composite mechanism for charge recombination between the injected electron and the oxidized sensitizer. Sensitizers that contain a pendant electron donor, as well as core/shell SnO 2 /TiO 2 nanostructures, often prolong the lifetime of the injected electron and provide fundamental insights into adiabatic and nonadiabatic electron transfer mechanisms. Regeneration of the oxidized sensitizer by iodide is enhanced through halogen bonding, orbital pathways, and ion pairing. A substantial ∼10 MV cm −1 electric field is created by electron injection into TiO 2 nanocrystallites that induces ion migration, reports on the sensitizer dipole orientation, and (in some cases) reorients or flips the sensitizer. Dye-sensitized conductive oxides also promote long-lived charge separation with bias dependent kinetics that provide insights into the reorganization energies associated with electron and proton-coupled electron transfer in the electric double layer.

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Metal ion linked multilayers on mesoporous substrates: Energy/electron transfer, photon upconversion, and more

Cited by 16 publications

References 124 publications

Modulating TTA efficiency through control of high energy triplet states

Modulating TTA efficiency through control of high energy triplet states

Role of Metal Ion-Linked Multilayer Thickness and Substrate Porosity in Surface Loading, Diffusion, and Solar Energy Conversion

Perspectives on Dye Sensitization of Nanocrystalline Mesoporous Thin Films

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