Electron injection from a carboxylic anchoring dye to TiO2 nanoparticles in aprotic solvents

Fang, Hui; Wu, Yuhao; Kuhn, Danielle L.; Zander, Zachary; DeLacy, Brendan G.; Rao, Yi; Dai, Hai‐Lung

doi:10.1016/j.chemphys.2018.02.022

Cited by 9 publications

(12 citation statements)

References 34 publications

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“…The experimental setup for the visible pump-transient IR probe experiments was described in our previous work. 45 Briefly, a regenerative-amplified Ti:Sapphire laser system (Quantronix, 100 fs), operating at 800 nm and 1 kHz repetition rate, was used for the experiments. A typical output power of the laser was 2.5 W. Then 40% of the 800 nm output was frequency doubled in a BBO crystal to generate a pump pulse of 400 nm with a pulse energy of 3 μJ.…”

Section: Base Treatment Of Electrospun Tio 2 Nanofibersmentioning

confidence: 99%

Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO₂ Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon

et al. 2019

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Among the world’s most deadly toxins are a class of organophosphates that are used as chemical warfare agents (CWAs). It is imperative to continue to develop novel means for mitigation and protection against these chemical threats. Sensitizing the surface of metal oxide semiconductors with plasmonic nanoparticles for photocatalytic degradation of chemical threats has been a prominent area of research in recent years. Anisotropic silver nanoplateles were purposefully grown on the surface of TiO2 fibers, in order to determine the impact of silver nanoparticle shape on (1) the generation of hot electrons by the silver, (2) the subsequent transfer of those electrons from the silver into the TiO2, and (3) the photocatalytic behavior of the Ag–TiO2 composite. To elucidate the charge injection properties of the composites, transient absorption experiments (pump–probe experiments) were undertaken. These involved pumping the composite samples with a range of discrete visible wavelengths and probing the composite within the intraband transitions of the TiO2. As a complement to these experiments, the photocatalytic properties of the Ag–TiO2 composite fibers were studied via the photocatalytic hydrolysis of methyl paraoxon, a chemical warfare agent simulant. This involved exposure of the methyl paraoxon to either red, green, blue, or white LED illumination. For both the transient absorption and photocatalytic experiments, maximum efficiency was observed for those scenarios in which the resonance of the silver platelets most closely matched the wavelength of incident radiation. Furthermore, the composite with silver nanoplatelets clearly outperformed its counterpart with silver nanospheres, in terms of both charge injection and photocatalytic behavior. We believe these results shall serve as a basis for future catalytic research in which the resonance of anisotropic plasmonic nanoparticles (in a given composite) shall be designed to match the wavelength of incident radiation.

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Section: Base Treatment Of Electrospun Tio 2 Nanofibersmentioning

confidence: 99%

Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO₂ Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon

et al. 2019

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Section: Solvent Effects On Dye Adsorption and Electron Injection At Tio2 Nanoparticle Surfacesmentioning

confidence: 99%

“…Specifically, we show how the type of solvent (i.e., protic or aprotic) and solvent polarity affect dye adsorption free energy and density, [83,84] as well as the injection rate of electrons from excited dye molecules to TiO 2 particles. [85] By combing these prior observations, we present a holistic and comprehensive understanding on how the solvent used may affect the efficacy of DSSC. The physical basis for the solvent effect clearly reveals why ACN happens to be the preferred solvent for DSSC fabrication.…”

Section: Introductionmentioning

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“…The lines are fitting curves with a signal exponential rise function convoluted with the instrument response function 300 fs. b) The normalized transient absorption signal intensity for p-ER onto TiO 2 in different solvents.Reproduced with permission [85]. Copyright 2018, Elsevier…”

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Influence of Solvent on Dye‐Sensitized Solar Cell Efficiency: What is so Special About Acetonitrile?

Fang

Wilhelm

et al. 2021

Part & Part Syst Charact

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The selection of solvent for preparing a working electrode (and to act as the electrolyte) is known to influence the efficiency of dye‐sensitized solar cells. In this topical review, results taken from a systematic study are presented from the authors’ own lab examining how protic and aprotic solvents, as well as solvent polarity, affect adsorption of carboxylic dyes on the titanium dioxide nanoparticle surface and electron injection from the dye to the semiconductor. Adsorption of dye molecules on nanoparticle surfaces is measured through second harmonic light scattering and electron injection through ultrafast transient mid‐infrared absorption. It is revealed that protic solvents do not allow direct adsorption of the dye onto the semiconductor surface, due to hydrogen bonding with the dye and competitive binding to the semiconductor surface. Aprotic solvents, on the other hand, support solvation of the dye molecules but also facilitate dye adsorption on the semiconductor nanoparticle. Among aprotic solvents, it is found that solvents with higher polarity result in larger adsorption free energy for the dye and faster electron injection. Overall, these studies reveal that aprotic solvents with high solvent polarity (such as acetonitrile) yield more efficient solar cell devices.

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Quantitative Modeling of Electron Dynamics and the Effect of Diffusion in Photosensitized Semiconductor Nanocomposites

Fang

Wilhelm

et al. 2022

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Photosensitized semiconducting nanomaterials have received considerable attention because of their applications in photocatalytic and photoelectronic devices. In such systems, photoexcited electrons with sufficiently high energies can be injected into the conduction band (CB) of an adjacent semiconductor. These excited electrons are subjected to various physical processes that can lead to their annihilation before exercising their catalytic/electric functions, and the efficiency of the photosensitized functions depends on the quantity of CB electrons produced and how long they remain near the surface region of the semiconductor. The rise and decay of photoexcited electrons in the semiconductor CB can be probed with transient IR absorption (TA), which was first demonstrated by Lian and coworkers. Results from various laboratories have since revealed that electrons appear in the CB following the excitation of the photosensitizer in tens to hundreds of femtoseconds and that the decay of the CB electrons typically exhibits multiple exponentials on varying ultrafast time scales. The size of the semiconductor nanoparticle appears to influence the diffusion of the CB electrons and thus their lifetimes. In all studies reported, the observed multiexponential decays have been analyzed and interpreted using purely phenomenological models, in which the individual decays were intuitively assigned to one specific relaxation or loss process.In reality, however, each exponential decay can be a convolution of multiple physical processes. In this Account, we report a universally applicable physical model, constructed by including all known electron dynamic processes, to quantitatively account for the multiexponential decays. We characterize the model as universal, as it can be used to analyze our own TA measurements, as well as data acquired in other laboratories. In our study of TiO 2 nanorods photosensitized by Ag platelets, we demonstrate that each of the observed triple-exponential decays corresponds to a convolution of several physical decay processes occurring on similar time scales. The rate of each of the processes can be deconvoluted and determined to construct a complete, physically based model to assess the most important question: How many CB electrons are near the semiconductor surface region and what is their lifetime?The size of the semiconductor is an important consideration. Intuitively, as the semiconductor volume increases, there is more room for CB electrons to diffuse around, which increases their lifetime as annihilation occurs primarily at the surface. Indeed, Tachiya and co-workers previously reported that this lifetime increases with particle size. Nevertheless, while CB electrons live longer in the bulk of the particle, they are only useful when they are at the surface. Overall, what really matters is the CB electrons near the surface region, where the photosensitized functions actually occur. In applying our model to analyze the previously reported size-d...

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Electron injection from a carboxylic anchoring dye to TiO2 nanoparticles in aprotic solvents

Cited by 9 publications

References 34 publications

Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO₂ Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon

Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO₂ Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon

Influence of Solvent on Dye‐Sensitized Solar Cell Efficiency: What is so Special About Acetonitrile?

Quantitative Modeling of Electron Dynamics and the Effect of Diffusion in Photosensitized Semiconductor Nanocomposites

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Electron injection from a carboxylic anchoring dye to TiO2 nanoparticles in aprotic solvents

Cited by 9 publications

References 34 publications

Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO2 Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon

Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO2 Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon

Influence of Solvent on Dye‐Sensitized Solar Cell Efficiency: What is so Special About Acetonitrile?

Quantitative Modeling of Electron Dynamics and the Effect of Diffusion in Photosensitized Semiconductor Nanocomposites

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Product

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Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO₂ Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon

Fabrication of Anisotropic Silver Nanoplatelets on the Surface of TiO₂ Fibers for Enhanced Photocatalysis of a Chemical Warfare Agent Simulant, Methyl Paraoxon