| 1. |
- Bericat Vadell, Robert, et al.
(författare)
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Single-electron transfer reactions on surface-modified gold plasmons
- 2023
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Ingår i: Materials Today Chemistry. - : Elsevier. - 2468-5194. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- Photoredox catalysis's relevance in organic synthesis research and innovation will increase in the coming decades. However, the processes rely almost exclusively on expensive noble metal complexes, most notably iridium complexes, to absorb light and transfer a single charge to a substrate or a catalyst to initiate cascade transformations. Light-triggered plasmon resonances generate a non-Fermi-Dirac energy distribution with many hot carriers that decay in similar to 1 ps. Their ultrafast relaxation makes performing single electron transfer (SET) transformations challenging. Herein, a novel photosystem is proposed based on surface-modified gold nanoparticles (aka plasmon "molecularization"), which improved charge separation and, more importantly, enabled SET reactions, expanding the portfolio of photocatalysts available for photoredox catalysis. The photosystem was made into an electrode, permitting its use in photoelectrochemical arrangements that leverage electro- and photo-chemical approaches' benefits and chemical engineering solutions, helping the synthetic chemistry efforts towards greener synthesis and synthesis of more complex structures on a scale.
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| 2. |
- Clarizia, Laura, et al.
(författare)
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Effect of Synthesis Method on Reaction Mechanism for Hydrogen Evolution over CuxOy/TiO2 Photocatalysts : A Kinetic Analysis
- 2023
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Ingår i: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- The existing literature survey reports rare and conflicting studies on the effect of the preparation method of metal-based semiconductor photocatalysts on structural/morphological features, electronic properties, and kinetics regulating the photocatalytic H-2 generation reaction. In this investigation, we compare the different copper/titania-based photocatalysts for H-2 generation synthesized via distinct methods (i.e., photodeposition and impregnation). Our study aims to establish a stringent correlation between physicochemical/electronic properties and photocatalytic performances for H-2 generation based on material characterization and kinetic modeling of the experimental outcomes. Estimating unknown kinetic parameters, such as charge recombination rate and quantum yield, suggests a mechanism regulating charge carrier lifetime depending on copper distribution on the TiO2 surface. We demonstrate that H-2 generation photoefficiency recorded over impregnated CuxOy/TiO2 is related to an even distribution of Cu(0)/Cu(I) on TiO2, and the formation of an Ohmic junction concertedly extended charge carrier lifetime and separation. The outcomes of the kinetic analysis and the related modeling investigation underpin photocatalyst physicochemical and electronic properties. Overall, the present study lays the groundwork for the future design of metal-based semiconductor photocatalysts with high photoefficiencies for H-2 evolution.
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| 3. |
- Dey, Ananta, et al.
(författare)
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Exploiting hot electrons from a plasmon nanohybrid system for the photoelectroreduction of CO2
- 2024
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Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic materials convert light into hot carriers and heat to mediate catalytic transformation. The participation of hot carriers (photocatalysis) remains a subject of vigorous debate, often argued on the basis that carriers have ultrashort lifetime incompatible with drive photochemical processes. This study utilises plasmon hot electrons directly in the photoelectrocatalytic reduction of CO2 to CO via a Ppasmonic nanohybrid. Through the deliberate construction of a plasmonic nanohybrid system comprising NiO/Au/ReI(phen-NH2)(CO)3Cl (phen-NH2 = 1,10-Phenanthrolin-5-amine) that is unstable above 580 K; it was possible to demonstrate hot electrons are the main culprit in CO2 reduction. The engagement of hot electrons in the catalytic process is derived from many approaches that cover the processes in real-time, from ultrafast charge generation and separation to catalysis occurring on the minute scale. Unbiased in situ FTIR spectroscopy confirmed the stepwise reduction of the catalytic system. This, coupled with the low thermal stability of the ReI(phen-NH2)(CO)3Cl complex, explicitly establishes plasmonic hot carriers as the primary contributors to the process. Therefore, mediating catalytic reactions by plasmon hot carriers is feasible and holds promise for further exploration. Plasmonic nanohybrid systems can leverage plasmon’s unique photophysics and capabilities because they expedite the carrier’s lifetime.
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| 4. |
- Dey, Ananta, et al.
(författare)
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Hydrogen evolution with hot electrons on a plasmonic-molecular catalyst hybrid system
- 2024
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic systems convert light into electrical charges and heat, mediating catalytic transformations. However, there is ongoing controversy regarding the involvement of hot carriers in the catalytic process. In this study, we demonstrate the direct utilisation of plasmon hot electrons in the hydrogen evolution reaction with visible light. We intentionally assemble a plasmonic nanohybrid system comprising NiO/Au/[Co(1,10-Phenanthrolin-5-amine)2(H2O)2], which is unstable at water thermolysis temperatures. This assembly limits the plasmon thermal contribution while ensuring that hot carriers are the primary contributors to the catalytic process. By combining photoelectrocatalysis with advanced in situ spectroscopies, we can substantiate a reaction mechanism in which plasmon-induced hot electrons play a crucial role. These plasmonic hot electrons are directed into phenanthroline ligands, facilitating the rapid, concerted proton-electron transfer steps essential for hydrogen generation. The catalytic response to light modulation aligns with the distinctive profile of a hot carrier-mediated process, featuring a positive, though non-essential, heat contribution. Direct participation of plasmon-induced hot electrons in the photoelectrocatalytic synthesis of hydrogen. This report solves a long-lasting contentious issue surrounding plasmonic materials on catalytic applications.
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| 5. |
- Geng, Xinjian, et al.
(författare)
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Direct Plasmonic Solar Cell Efficiency Dependence on Spiro-OMeTAD Li-TFSI Content
- 2021
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- The proliferation of the internet of things (IoT) and other low-power devices demands the development of energy harvesting solutions to alleviate IoT hardware dependence on single-use batteries, making their deployment more sustainable. The propagation of energy harvesting solutions is strongly associated with technical performance, cost and aesthetics, with the latter often being the driver of adoption. The general abundance of light in the vicinity of IoT devices under their main operation window enables the use of indoor and outdoor photovoltaics as energy harvesters. From those, highly transparent solar cells allow an increased possibility to place a sustainable power source close to the sensors without significant visual appearance. Herein, we report the effect of hole transport layer Li-TFSI dopant content on semi-transparent, direct plasmonic solar cells (DPSC) with a transparency of more than 80% in the 450-800 nm region. The findings revealed that the amount of oxidized spiro-OMeTAD (spiro(+)TFSI(-)) significantly modulates the transparency, effective conductance and conditions of device performance, with an optimal performance reached at around 33% relative concentration of Li-TFSI concerning spiro-OMeTAD. The Li-TFSI content did not affect the immediate charge extraction, as revealed by an analysis of electron-phonon lifetime. Hot electrons and holes were injected into the respective layers within 150 fs, suggesting simultaneous injection, as supported by the absence of hysteresis in the I-V curves. The spiro-OMeTAD layer reduces the Au nanoparticles' reflection/backscattering, which improves the overall cell transparency. The results show that the system can be made highly transparent by precise tuning of the doping level of the spiro-OMeTAD layer with retained plasmonics, large optical cross-sections and the ultrathin nature of the devices.
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| 6. |
- Silveira, Vitor R., et al.
(författare)
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Photoelectrocatalytic Conversion of Nitrates to Ammonia with Plasmon Hot Electrons
- 2023
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 127:11, s. 5425-5431
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Tidskriftsartikel (refereegranskat)abstract
- Changes in agricultural practices enabled the circulation of N-containing species, making converting nitrate into ammonia (fertilizer) highly desirable. Herein, we propose a photosystem composed of NiO/Au plasmon/TiO2 that selectively produces ammonia from nitrates at neutral pH and room temperature with visible light via a combination of electrochemical and plasmon hot electrons (i.e., it is a photoelectrochemical process). The system effectively suppresses the undesirable hydrogen evolution reaction and converts the superfluous hot holes into atmospheric oxygen. The role of the hot electrons is to boost catalytic performance, enabling higher reaction rates at lower potentials. The process paves the way for agricultural practices that recycle nutrients, improving process circularity and reducing fertilizer costs.
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| 7. |
- Vadell, Robert Bericat, et al.
(författare)
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Carrier Dynamics in Solution-Processed CuI as a P-Type Semiconductor : The Origin of Negative Photoconductivity
- 2023
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 14:4, s. 1007-1013
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Tidskriftsartikel (refereegranskat)abstract
- There is an urgent need for efficient solutionprocessable p-type semiconductors. Copper(I) iodide (CuI) has attracted attention as a potential candidate due to its good electrical properties and ease of preparation. However, its carrier dynamics still need to be better understood. Carrier dynamics after bandgap excitation yielded a convoluted signal of free carriers (positive signal) and a negative feature, which was also present when the material was excited with sub-bandgap excitation energies. This previously unseen feature was found to be dependent on measurement temperature and attributed to negative photoconductivity. The unexpected signal relates to the formation of polarons or strongly bound excitons. The possibility of coupling CuI to plasmonic sensitizers is also tested, yielding positive results. The outcomes mentioned above could have profound implications regarding the applicability of CuI in photocatalytic and photovoltaic systems and could also open a whole new range of possible applications.
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| 8. |
- Verma, Rishi, et al.
(författare)
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Nickel-Laden Dendritic Plasmonic Colloidosomes of Black Gold : Forced Plasmon Mediated Photocatalytic CO2 Hydrogenation
- 2023
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 17:5, s. 4526-4538
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have designed and synthesized nickel-laden dendritic plasmonic colloidosomes of Au (black gold-Ni). The photocatalytic CO2 hydrogenation activities of black gold-Ni increased dramatically to the extent that measurable photoactivity was only observed with the black gold-Ni catalyst, with a very high photocatalytic CO production rate (2464 +/- 40 mmol gNi-1 h-1) and 95% selectivity. Notably, the reaction was carried out in a flow reactor at low temperature and atmospheric pressure without external heating. The catalyst was stable for at least 100 h. Ultrafast transient absorption spectroscopy studies indicated indirect hot-electron transfer from the black gold to Ni in less than 100 fs, corroborated by a reduction in Au-plasmon electron-phonon lifetime and a bleach signal associated with Ni d-band filling. Photocatalytic reaction rates on excited black gold-Ni showed a superlinear power law dependence on the light intensity, with a power law exponent of 5.6, while photocatalytic quantum efficiencies increased with an increase in light intensity and reaction temperature, which indicated the hot-electron-mediated mechanism. The kinetic isotope effect (KIE) in light (1.91) was higher than that in the dark (similar to 1), which further indicated the electron-driven plasmonic CO2 hydrogenation. Black gold-Ni catalyzed CO2 hydrogenation in the presence of an electron-accepting molecule, methyl-p-benzoquinone, reduced the CO production rate, asserting the hot-electron-mediated mechanism. Operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that CO2 hydrogenation took place by a direct dissociation path via linearly bonded Ni-CO intermediates. The outstanding catalytic performance of black gold-Ni may provide a way to develop plasmonic catalysts for CO2 reduction and other catalytic processes using black gold.
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| 9. |
- Zou, Xianshao, et al.
(författare)
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Photophysical Study of Electron and Hole Trapping in TiO2 and TiO2/ Au Nanoparticles through a Selective Electron Injection
- 2022
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:50, s. 21467-21475
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Tidskriftsartikel (refereegranskat)abstract
- The photophysics surrounding the electron and hole trapping in TiO2 do not have a scientific consensus. Herein, we studied the steady-state photoluminescence and time-resolved spectroscopy time-resolved photoluminescence indicates that the electrons from bandgap excitation decay slower (similar to 30 ps) than in TiO2 (< 24 ps). We conclude this as a result of the band bending passivation effect on the surface electron traps. Meanwhile, electron trapping is proved as the dominant surface depopulation process because of the easy-fill characteristics of surface hole traps even under low excitation density, which also interprets the slow surface hole trapping (similar to 2 ns) in TiO2. Through plasmon-assisted electron injection, we distinguished the electron and hole behaviors at varied photon fluences and then obtained the intrinsic bulk trapping of electrons and holes in the similar to 50 and similar to 400 ps time range, respectively.
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| 10. |
- Zou, Xianshao, et al.
(författare)
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Ultrafast Infrared-to-Visible Photon Upconversion on Plasmon/TiO2 Solid Films
- 2023
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 14:27, s. 6255-6262
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Tidskriftsartikel (refereegranskat)abstract
- Optical upconversion via a multiphoton absorption process converts incoherent low-energy photons to shorter wavelengths. In this contribution, we report a solid-state thin film for infrared-to-visible upconversion composed of plasmonic/TiO2 interfaces. When excited at λ = 800 nm, three photons are absorbed, leading to the excitation of TiO2 trap states into an emissive state in the visible domain. The plasmonic nanoparticle enhances the light absorption capabilities of the semiconductor, increasing emission efficiency by 20 times. We demonstrate that the plasmonic nanoparticle only changes the optical absorption of the semiconductor; i.e., the process is purely photonic. The process occurs in the ultrafast domain (<10 ps), contrasting with molecular triplet-triplet exciton annihilation, the commonly used method in photon upconversion, in the nano- to microsecond time scales. The process utilizes pre-existing trap states within the semiconductor bandgap and involves three-photon absorption.
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