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  • 1
    Online Resource
    Online Resource
    Evaluating the Solvent Stark Effect from Temperature-Dependent Solvatochromic Shifts of Anthracene (2020)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_22069
    Format: 1 Online-Ressource (6 Seiten)
    Content: The solvent Stark effect on the spectral shifts of anthracene is studied with temperature‐dependent solvatochromic measurements. The Stark contribution ΔvStark to the absorption shift Δvp in polar solvents is measured to be ΔvStark=(53±35) cm−1, in reasonable agreement with dielectric continuum theory estimate of 28 cm−1, whereas the major shift Δvp∼300 cm−1 presumably originates from the solute quadrupole. We pay attention to the accurate correction of Δvp for the nonpolar contribution that is crucial when the shifts are modest in magnitude.
    Content: Peer Reviewed
    In: ChemPhysChem, Weinheim : Wiley-VCH, 21,2020,7, Seiten 610-615
    Language: English
    DOI: 10.18452/21329
    URN: urn:nbn:de:kobv:11-110-18452/22069-0
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    HU Berlin
  • 2
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    Online Resource
    Insights into Charge Transfer at an Atomically Precise Nanocluster/Semiconductor Interface (2020)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_22158
    Format: 1 Online-Ressource (7 Seiten)
    Content: The deposition of an atomically precise nanocluster, for example, Ag44(SR)30, onto a large‐band‐gap semiconductor such as TiO2 allows a clear interface to be obtained to study charge transfer at the interface. Changing the light source from visible light to simulated sunlight led to a three orders of magnitude enhancement in the photocatalytic H2 generation, with the H2 production rate reaching 7.4 mmol h−1 gcatalyst−1. This is five times higher than that of TiO2 modified with Ag nanoparticles and even comparable to that of TiO2 modified with Pt nanoparticles under similar conditions. Energy band alignment and transient absorption spectroscopy reveal that the role of the metal clusters is different from that of both organometallic complexes and plasmonic nanoparticles: A type II heterojunction charge‐transfer route is achieved under UV/Vis irradiation, with the cluster serving as a small‐band‐gap semiconductor. This results in the clusters acting as co‐catalysts rather than merely photosensitizers.
    Content: Peer Reviewed
    In: Weinheim : Wiley-VCH, 59,20, Seiten 7748-7754
    Language: English
    DOI: 10.18452/21425
    DOI: 10.1002/anie.201915074
    URN: urn:nbn:de:kobv:11-110-18452/22158-2
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    HU Berlin
  • 3
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    Online Resource
    Type-I Energy Level Alignment at the PTCDA—Monolayer MoS2 Interface Promotes Resonance Energy Transfer and Luminescence Enhancement (2021)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_24162
    Format: 1 Online-Ressource (9 Seiten)
    Content: Van der Waals heterostructures consisting of 2D semiconductors and conjugated molecules are of increasing interest because of the prospect of a synergistic enhancement of (opto)electronic properties. In particular, perylenetetracarboxylic dianhydride (PTCDA) on monolayer (ML)-MoS2 has been identified as promising candidate and a staggered type-II energy level alignment and excited state interfacial charge transfer have been proposed. In contrast, it is here found with inverse and direct angle resolved photoelectron spectroscopy that PTCDA/ML-MoS2 supported by insulating sapphire exhibits a straddling type-I level alignment, with PTCDA having the wider energy gap. Photoluminescence (PL) and sub-picosecond transient absorption measurements reveal that resonance energy transfer, i.e., electron–hole pair (exciton) transfer, from PTCDA to ML-MoS2 occurs on a sub-picosecond time scale. This gives rise to an enhanced PL yield from ML-MoS2 in the heterostructure and an according overall modulation of the photoresponse. These results underpin the importance of a precise knowledge of the interfacial electronic structure in order to understand excited state dynamics and to devise reliable design strategies for optimized optoelectronic functionality in van der Waals heterostructures.
    Content: Peer Reviewed
    Note: This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.
    In: Weinheim : Wiley-VCH, 8
    Language: English
    DOI: 10.18452/23510
    DOI: 10.1002/advs.202100215
    URN: urn:nbn:de:kobv:11-110-18452/24162-4
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  • 4
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    Online Resource
    Mono‐, Di‐, and Tri‐Valent Cation Doped BiFe0.95Mn0.05O3 Nanoparticles: Ferroelectric Photocatalysts (2022)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_26449
    Format: 1 Online-Ressource (16 Seiten)
    Content: The ferroelectricity of multivalent codoped Bismuth ferrite (BiFeO3; BFO) nanoparticles (NPs) is revealed and utilized for photocatalysis, exploiting their narrow electronic bandgap. The photocatalytic activity of ferroelectric photocatalysts BiFe0.95Mn0.05O3 (BFM) NPs and mono‐, di‐, or tri‐valent cations (Ag+, Ca2+, Dy3+; MDT) coincorporated BFM NPs are studied under ultrasonication and in acidic conditions. It is found that such doping enhances the photocatalytic activity of the ferroelectric NPs approximately three times. The correlation of the photocatalytic activity with structural, optical, and electrical properties of the doped NPs is established. The increase of spontaneous polarization by the mono‐ and tri‐valent doping is one of the major factors in enhancing the photocatalytic performance along with other factors such as stronger light absorption in the visible range, low recombination rate of charge carriers, and larger surface area of NPs. A‐site doping of BFO NPs by divalent elements suppresses the polarization, whereas trivalent (Dy3+) and monovalent (Ag+) cations provide an increase of polarization. The depolarization field in these single domain NPs acts as a driving force to mitigate recombination of the photoinduced charge carriers.
    Content: The ferroelectricity of Ag/Ca/Dy‐doped BiFe0.95Mn0.05O3 nanoparticles are utilized for photocatalysis under ultrasonic conditions. The mitigated recombination of photoinduced charge‐carriers in the nanoparticles due to the depolarization field, is one of the important factors for the photocatalytic rate. The piezoresponse becomes a crucial parameter under ultrasonic conditions for ferroelectric photocatalysts. The pink dye (rhodamine B) is photodegraded using MDT doped nanoparticles. The ease of photoinduced charge carrier separation in single domain nanoparticles using the depolarization field as a driving force is shown. image
    Content: Peer Reviewed
    In: Weinheim : Wiley-VCH, 32,43
    Language: English
    DOI: 10.1002/adfm.202207105
    DOI: 10.18452/25781
    URN: urn:nbn:de:kobv:11-110-18452/26449-3
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  • 5
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    Online Resource
    Evidence for Hybrid Inorganic–Organic Transitions at the WS2/Terrylene Interface (2023)
    Berlin : Humboldt-Universität zu Berlin
    Details
    UID:
    edochu_18452_28959
    Format: 1 Online-Ressource (11 Seiten)
    Content: The realization of the potential of hybrid inorganic organic systems requires an understanding of the coupling between the constituents: its nature and its strength. The observation of hybrid optical transitions in the monolayer WS2/terrylene hybrid is reported. The first-principle calculations, linear optical, and transient absorption spectroscopy are employed to investigate the optical spectrum of the hybrid, which exhibits a new transition that does not appear in the constituents’ spectra. The calculations indicate type II level alignment, with the highest occupied level of terrylene in the gap of WS2. Exploiting state-resolved transient absorption, the response of the hybrid interface to optical excitation is selectively probed. The dynamics reveal rapid hole transfer from WS2 to the terrylene layer, with a decay time of 88 ps. This hole transfer induces a bleach of the hybrid transition, which indicates that terrylene contributes to its initial state. Based on this, the hybrid resonance energy, and on our calculations, we assign the hybrid feature to a transition from the highest occupied molecular orbital of terrylene to the conduction band of WS2 close to the Γ point. The results indicate that the conditions for strong electronic coupling are met in this hybrid system.
    Content: Peer Reviewed
    In: Weinheim : Wiley-VCH, 221,1
    Language: English
    DOI: 10.18452/28309
    DOI: 10.1002/pssa.202300346
    URN: urn:nbn:de:kobv:11-110-18452/28959-3
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    HU Berlin
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