1
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Yan H, Harmer R, Zafar B, Galoppini E, Gundlach L. Interfacial electron transfer of perylenes: Influence of the anchor binding mode. J Chem Phys 2024; 160:034706. [PMID: 38235795 DOI: 10.1063/5.0185342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 12/21/2023] [Indexed: 01/19/2024] Open
Abstract
Interfacial electron transfer (IET) through saturated single-linker and dual-linker groups from a perylene chromophore into nanostructured TiO2 films was studied by ultrafast spectroscopy. Perylene chromophores with one and two propanoic acid linker groups in the peri and ortho positions were investigated. In comparison to previously studied perylenes bound via unsaturated acrylic acid linkers, the chromophores with saturated linkers showed bi-exponential IET dynamics. Two distinct transfer times were observed that indicate the presence of two concurrent binding modes. A comparison between ortho- and peri-substituted sensitizers resulted in slower IET dynamics and weaker electronic coupling for ortho substitution. Finally, IET from sensitizers with saturated linker groups is neither promoted nor hindered by a second linker group. This indicates that only one of the two linkers binds covalently to the surface. This study reveals the importance of the anchor-binding mode and design considerations of the linker for regulating IET.
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Affiliation(s)
- Han Yan
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
| | - Ryan Harmer
- Department of Chemistry, Rutgers University Newark, Newark, New Jersey 07102, USA
| | - Binish Zafar
- Department of Chemistry, Rutgers University Newark, Newark, New Jersey 07102, USA
| | - Elena Galoppini
- Department of Chemistry, Rutgers University Newark, Newark, New Jersey 07102, USA
| | - Lars Gundlach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
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2
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Sreekumar S, Heidari M, Cheng Z, Maddali H, House K, Frei H, Galoppini E, O'Carroll DM. Self-Assembled Monolayers for Improved Charge Injection of Silver Back Electrodes in Inverted Organic Electronic Devices. ACS Appl Mater Interfaces 2022; 14:38270-38280. [PMID: 35852106 DOI: 10.1021/acsami.2c07610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Self-assembled monolayers (SAMs) formed from thiol compounds bound to Ag and Au electrodes have been used as an important strategy in improving the stability and efficiency of optoelectronic devices. Thiol compounds provide only one binding site with the metal electrode which limits their influence. Dithiolane/dithiol compounds can provide multiple binding sites and could be useful in enhancing the performance of the device. In this study, inverted organic semiconducting hole-only devices were fabricated by using Ag back electrodes in conjunction with SAMs formed from disulfide lipoic acid-based compounds and were compared to a long aliphatic chain thiol. The binding and the electronic properties as well as electrical characteristics of the SAMs on silver were studied to look at the influence of their structure on charge injection in the organic semiconductor devices. It was found that the SAMs formed with (±)-α-lipoic acid, isolipoic acid, and (±)-4-phenylbutyl 5-(1,2-dithiolan-3-yl) pentanoate significantly improved the charge injection by either changing the work function of the Ag or altering the physical interaction between the polymer and the metal surface. This study may lead to an understanding of how the nature of the functional groups of the SAM and the number of bonds formed between each SAM molecule and the metal electrode influence the contact resistance and the performance of organic semiconductor devices.
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Affiliation(s)
- Sneha Sreekumar
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Rd., Piscataway, New Jersey 08854, United States
| | - Marzieh Heidari
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Zhongkai Cheng
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Rd., Piscataway, New Jersey 08854, United States
| | - Hemanth Maddali
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Rd., Piscataway, New Jersey 08854, United States
| | - Krystal House
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Rd., Piscataway, New Jersey 08854, United States
| | - Heinz Frei
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California 94720, United States
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Deirdre M O'Carroll
- Department of Chemistry and Chemical Biology, Rutgers University, 123 Bevier Rd., Piscataway, New Jersey 08854, United States
- Department of Materials Science and Engineering, Rutgers University, 607 Taylor Rd., Piscataway, New Jersey 08854, United States
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3
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Heidari M, Loague Q, Bangle RE, Galoppini E, Meyer GJ. Reorganization Energies for Interfacial Electron Transfer across Phenylene Ethynylene Rigid-Rod Bridges. ACS Appl Mater Interfaces 2022; 14:35205-35214. [PMID: 35862637 DOI: 10.1021/acsami.2c07151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A family of three ruthenium bipyridyl rigid-rod compounds of the general form [Ru(bpy)2(LL)](PF6)2 were anchored to mesoporous thin films of tin-doped indium oxide (ITO) nanocrystals. Here, LL is a 4-substituted 2,2-bipyridine (bpy) ligand with varying numbers of conjugated phenylenethynylene bridge units between the bipyridine ring and anchoring group consisting of a bis-carboxylated isophthalic group. The visible absorption spectra and the formal potentials, Eo(RuIII/II), of the surface anchored rigid-rods were insensitive to the presence of the phenylene ethynylene bridge units in 0.1 M tetrabutyl ammonium perchlorate acetonitrile solutions (TBAClO4/CH3CN). The conductive nature of the ITO enabled potentiostatic control of the Fermi level and hence a means to tune the Gibbs free energy change, -ΔG°, for electron transfer from the ITO to the rigid-rods. Pseudo-rate constants for this electron transfer reaction increased as the number of bridge units decreased at a fixed -ΔG°. With the assumption that the reorganization energy, λ, and the electronic coupling matrix element, Hab, were independent of the applied potential, rate constants measured as a function of -ΔG° and analyzed through Marcus-Gerischer theory provided estimates of Hab and λ. In rough accordance with the dielectric continuum theory, λ was found to increase from 0.61 to 0.80 eV as the number of bridge units was increased. In contrast, Hab decreased markedly with distance from 0.54 to 0.11 cm-1, consistent with non-adiabatic electron transfer. Comparative analysis with previously published studies of bridges with an sp3-hybridized carbon indicated that the phenylene ethynylene bridge does not enhance electronic coupling between the oxide and the rigid-rod acceptor. The implications of these findings for practical applications in solar energy conversion are specifically discussed.
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Affiliation(s)
- Marzieh Heidari
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Quentin Loague
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Rachel E Bangle
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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4
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5
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Zhang H, Weiss I, Rudra I, Jo WJ, Kellner S, Katsoukis G, Galoppini E, Frei H. Controlling and Optimizing Photoinduced Charge Transfer across Ultrathin Silica Separation Membrane with Embedded Molecular Wires for Artificial Photosynthesis. ACS Appl Mater Interfaces 2021; 13:23532-23546. [PMID: 33983702 DOI: 10.1021/acsami.1c00735] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ultrathin amorphous silica membranes with embedded organic molecular wires (oligo(p-phenylenevinylene), three aryl units) provide chemical separation of incompatible catalytic environments of CO2 reduction and H2O oxidation while maintaining electronic and protonic coupling between them. For an efficient nanoscale artificial photosystem, important performance criteria are high rate and directionality of charge flow. Here, the visible-light-induced charge flow from an anchored Ru bipyridyl light absorber across the silica nanomembrane to Co3O4 water oxidation catalyst is quantitatively evaluated by photocurrent measurements. Charge transfer rates increase linearly with wire density, with 5 nm-2 identified as an optimal target. Accurate measurement of wire and light absorber densities is accomplished by the polarized FT-IRRAS method. Guided by density functional theory (DFT) calculations, four wire derivatives featuring electron-donating (methoxy) and -withdrawing groups (sulfonate, perfluorophenyl) with highest occupied molecular orbital (HOMO) potentials ranging from 1.48 to 0.64 V vs NHE were synthesized and photocurrents evaluated. Charge transfer rates increase sharply with increasing driving force for hole transfer from the excited light absorber to the embedded wire, followed by a decrease as the HOMO potential of the wire moves beyond the Co3O4 valence band level toward more negative values, pointing to an optimal wire HOMO potential around 1.3 V vs NHE. Comparison with photocurrents of samples without nanomembrane indicates that silica layers with optimized wires are able to approach undiminished electron flux at typical solar intensities. Combined with the established high proton conductivity and small-molecule blocking property, the charge transfer measurements demonstrate that oxidation and reduction catalysis can be efficiently integrated on the nanoscale under separation by an ultrathin silica membrane.
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Affiliation(s)
- Hongna Zhang
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States
| | - Ian Weiss
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Indranil Rudra
- Shell India Markets Pvt. Ltd., Mahadeva Kodigehalli, Bangalore 562149, India
| | - Won Jun Jo
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States
| | - Simon Kellner
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States
| | - Georgios Katsoukis
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Heinz Frei
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, United States
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6
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Harmer R, Fan H, Lloyd K, Doble S, Avenoso J, Yan H, Rego LGC, Gundlach L, Galoppini E. Synthesis and Properties of Perylene-Bridge-Anchor Chromophoric Compounds. J Phys Chem A 2020; 124:6330-6343. [PMID: 32654486 DOI: 10.1021/acs.jpca.0c04609] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The quest to control chromophore/semiconductor properties to enable new technologies in energy and information science requires detailed understanding of charge carrier dynamics at the atomistic level, which can often be attained through the use of model systems. Perylene-bridge-anchor compounds are successful models for studying fundamental charge transfer processes on TiO2, which remains among the most commonly investigated and technologically important interfaces, mostly because of perylene's advantageous electronic and optical properties. Nonetheless, the ability to fully exploit synthetically the substitution pattern of perylene with linker (= bridge-anchor) units remains little explored. Here we developed 2,5-di-tert-butylperylene (DtBuPe)-bridge-anchor compounds with t-Bu group substituents to prevent π-stacking and one or two linker units in both the peri and ortho positions, by employing a combination of Friedel-Crafts alkylations, bromination, iridium-catalyzed borylation, and palladium-catalyzed cross-coupling reactions. Photophysical characterization and computational analysis by density functional theory (DFT) and time-dependent DFT (TD-DFT) were carried out on four DtBuPe acrylic acid derivatives with a single or a double linker in peri (12b), ortho (15b), peri,peri (18b), and ortho,ortho (21b). The energies of the unoccupied orbitals {LUMO, LUMO + 1, LUMO + 2} are strongly affected by the presence of a π-conjugated linker, resulting in a stabilization of these states and a red shift of their absorption and emission spectra, as well as the loss of vibronic structure in the spectrum of the peri,peri compound, consistent with the strong bonding character of this substitution pattern.
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Affiliation(s)
- Ryan Harmer
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Hao Fan
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Katherine Lloyd
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Samantha Doble
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Joseph Avenoso
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, United States
| | - Han Yan
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Luis G C Rego
- Department of Physics, Universidade Federal de Santa Catarina (UFSC), Florianopolis, South Carolina 88040-900, Brazil
| | - Lars Gundlach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.,Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, United States
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
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7
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Chen Y, Viereck J, Harmer R, Rangan S, Bartynski RA, Galoppini E. Helical Peptides Design for Molecular Dipoles Functionalization of Wide Band Gap Oxides. J Am Chem Soc 2020; 142:3489-3498. [PMID: 31977205 DOI: 10.1021/jacs.9b12001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The use of helical hexapeptides to establish a surface dipole layer on a TiO2 substrate, with the goal of influencing the energy levels of a coadsorbed chromophore, is explored. Two helical hexapeptides, synthesized from 2-amino isobutyric acid (Aib) residues, were protected at the N-terminus with a carboxybenzyl group (Z) and at the C-terminus carried either a carboxylic acid or an isophthalic acid (Ipa) anchor group to form Z-(Aib)6-COOH or Z-(Aib)6-Ipa, respectively. Using a combination of vibrational and photoemission spectroscopies, bonding of the two peptides to TiO2 surfaces (either nanostructured or single-crystal TiO2(110)) was found to be highly dependent on the anchor group, with Ipa establishing a monolayer much more efficiently than COOH. Furthermore, a monolayer of Z-(Aib)6-Ipa on TiO2(110) was exposed for different binding times to a solution of a zinc tetraphenylporphyrin (ZnTPP) derivative terminated with an Ipa anchor group (ZnTPP-P-Ipa). Photoemission spectroscopy revealed that ZnTPP-P-Ipa partly displaced Z-(Aib)6-Ipa, forming a coadsorbed monolayer on the oxide surface. The presence of the peptide molecular dipole shifted the HOMO levels of the ZnTPP group to lower energy by ∼300 meV, in accordance with a simple parallel plate capacitor model. These results suggest that a mixed-layer approach, involving coadsorption of a strong molecular dipole compound with a chromophore, is a versatile method to shift the energy levels of such chromophores with respect to the band edges of the substrate.
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Affiliation(s)
- Yuan Chen
- Chemistry Department , Rutgers University , 73 Warren Street , Newark , New Jersey 07102 , United States
| | - Jonathan Viereck
- Department of Physics and Astronomy and Laboratory for Surface Modification , Rutgers University , 136 Frelinghuysen Road , Piscataway , New Jersey 08854 , United States
| | - Ryan Harmer
- Chemistry Department , Rutgers University , 73 Warren Street , Newark , New Jersey 07102 , United States
| | - Sylvie Rangan
- Department of Physics and Astronomy and Laboratory for Surface Modification , Rutgers University , 136 Frelinghuysen Road , Piscataway , New Jersey 08854 , United States
| | - Robert A Bartynski
- Department of Physics and Astronomy and Laboratory for Surface Modification , Rutgers University , 136 Frelinghuysen Road , Piscataway , New Jersey 08854 , United States
| | - Elena Galoppini
- Chemistry Department , Rutgers University , 73 Warren Street , Newark , New Jersey 07102 , United States
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8
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Konh M, He C, Li Z, Bai S, Galoppini E, Gundlach L, Teplyakov AV. Comparison of ZnO surface modification with gas-phase propiolic acid at high and medium vacuum conditions. J Vac Sci Technol A 2018; 36:041404. [PMID: 29983480 PMCID: PMC6026025 DOI: 10.1116/1.5031945] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 06/15/2018] [Accepted: 06/15/2018] [Indexed: 06/08/2023]
Abstract
Recent advances in preservation of the morphology of ZnO nanostructures during dye sensitization required the use of a two-step preparation procedure. The first step was the key for preserving ZnO materials morphology. It required exposing clean ZnO nanostructures to a gas-phase prop-2-ynoic acid (propiolic acid) in vacuum. This step resulted in the formation of a robust and stable surface-bound carboxylate with ethynyl groups available for further modification, for example, with click chemistry. This paper utilizes spectroscopic and microscopic investigations to answer several questions about this modification and to determine if the process can be performed under medium vacuum conditions instead of high vacuum procedures reported earlier. Comparing the results of the preparation process at medium vacuum of 0.5 Torr base pressure with the previously reported investigations of the same process in high vacuum of 10-5 Torr suggests that both processes lead to the formation of the same surface species, confirming that the proposed modification scheme can be widely applicable for ZnO sensitization procedures and does not require the use of high vacuum. Additional analysis comparing the computationally predicted surface structures with the results of spectroscopic investigations yields the more complete description of the surface species resulting from this approach.
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Affiliation(s)
- Mahsa Konh
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - Chuan He
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - Zhengxin Li
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - Shi Bai
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102
| | - Lars Gundlach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 and Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716
| | - Andrew V Teplyakov
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
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9
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Abraham B, Fan H, Galoppini E, Gundlach L. Vibrational Spectroscopy on Photoexcited Dye-Sensitized Films via Pump-Degenerate Four-Wave Mixing. J Phys Chem A 2018; 122:2039-2045. [PMID: 29381068 DOI: 10.1021/acs.jpca.7b10652] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Molecular sensitization of semiconductor films is an important technology for energy and environmental applications including solar energy conversion, photocatalytic hydrogen production, and water purification. Dye-sensitized films are also scientifically complex and interesting systems with a long history of research. In most applications, photoinduced heterogeneous electron transfer (HET) at the molecule/semiconductor interface is of critical importance, and while great progress has been made in understanding HET, many open questions remain. Of particular interest is the role of combined electronic and vibrational effects and coherence of the dye during HET. The ultrafast nature of the process, the rapid intramolecular vibrational energy redistribution, and vibrational cooling present complications in the study of vibronic coupling in HET. We present the application of a time domain vibrational spectroscopy-pump-degenerate four-wave mixing (pump-DFWM)-to dye-sensitized solid-state semiconductor films. Pump-DFWM can measure Raman-active vibrational modes that are triggered by excitation of the sample with an actinic pump pulse. Modifications to the instrument for solid-state samples and its application to an anatase TiO2 film sensitized by a Zn-porphyrin dye are discussed. We show an effective combination of experimental techniques to overcome typical challenges in measuring solid-state samples with laser spectroscopy and observe molecular vibrations following HET in a picosecond time window. The cation spectrum of the dye shows modes that can be assigned to the linker group and a mode that is localized on the Zn-phorphyrin chromophore and that is connected to photoexcitation.
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Affiliation(s)
- Baxter Abraham
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States
| | - Hao Fan
- Department of Chemistry, Rutgers University , Newark, New Jersey 07102, United States
| | - Elena Galoppini
- Department of Chemistry, Rutgers University , Newark, New Jersey 07102, United States
| | - Lars Gundlach
- Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States.,Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States
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10
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He C, Abraham B, Fan H, Harmer R, Li Z, Galoppini E, Gundlach L, Teplyakov AV. Morphology-Preserving Sensitization of ZnO Nanorod Surfaces via Click-Chemistry. J Phys Chem Lett 2018; 9:768-772. [PMID: 29364670 PMCID: PMC6007857 DOI: 10.1021/acs.jpclett.7b03388] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Films of ZnO nanorods grown by chemical vapor deposition were functionalized with a chromophore in a stepwise process that preserves the surface morphology. In the first step, the ZnO nanorods were functionalized by exposure to prop-2-ynoic acid (propiolic acid) in vacuum, which did bind through the COOH group leading to a ZnO surface functionalized with ethyne moieties (ethyne/ZnO). In the second step, 9-(4-azidophenyl)-2,5-di-tert-butylperylene (DTBPe-Ph-N3) was reacted with the ethyne/ZnO surface via copper-catalyzed azide-alkyne click reaction (CuAAC) in solution to form the DTBPe-functionalized surface (DTBPe/ZnO). The ZnO morphology was preserved after each step, as demonstrated by scanning electron microscopy (SEM). Each step was probed by X-ray photoelectron spectroscopy (XPS), and transient absorption spectroscopy (TA) of the resulting DTBPe/ZnO surface shows interfacial electron transfer following visible light excitation. As expected, attempts to bind the reference compound 1-(4-(8,11-ditert-butylperylen-3-yl)-phenyl)-1H-1,2,3-triazole-4-carboxylic acid (DTBPe-Ph-Tz-COOH) directly from solution lead to etched surfaces (confirmed by SEM) and undefined binding modes (confirmed by TA).
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Affiliation(s)
- Chuan He
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Baxter Abraham
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Hao Fan
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Ryan Harmer
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Zhengxin Li
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, Newark, New Jersey 07102, United States
| | - Lars Gundlach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, United States
| | - Andrew V. Teplyakov
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
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11
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Affiliation(s)
- Xiuyuan Ma
- Rutgers University, Chemistry Department, 73 Warren Street, Newark, NJ 07102, United States
| | - Hao Tang
- Rutgers University, Chemistry Department, 73 Warren Street, Newark, NJ 07102, United States
| | | | - Elena Galoppini
- Rutgers University, Chemistry Department, 73 Warren Street, Newark, NJ 07102, United States
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12
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Nieto-Pescador J, Abraham B, Li J, Batarseh A, Bartynski RA, Galoppini E, Gundlach L. Heterogeneous Electron-Transfer Dynamics through Dipole-Bridge Groups. J Phys Chem C Nanomater Interfaces 2016; 120:48-55. [PMID: 28479939 PMCID: PMC5418589 DOI: 10.1021/acs.jpcc.5b09463] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Heterogeneous electron transfer (HET) between photoexcited molecules and colloidal TiO2 has been investigated for a set of Zn-porphyrin chromophores attached to the semiconductor via linkers that allow to change level alignment by 200 meV by reorientation of the dipole moment. These unique dye molecules have been studied by femtosecond transient absorption spectroscopy in solution and adsorbed on the TiO2 colloidal film in vacuum. In solution energy transfer from the excited chromophore to the dipole group has been identified as a slow relaxation pathway competing with S2-S1 internal conversion. On the film heterogeneous electron transfer occurred in 80 fs, much faster compared to all intramolecular pathways. Despite a difference of 200 meV in level alignment of the excited state with respect to the semiconductor conduction band, identical electron transfer times were measured for different linkers. The measurements are compared to a quantum-mechanical model that accounts for electronic-vibronic coupling and finite band width for the acceptor states. We conclude that HET occurs into a distribution of transition states that differs from regular surface states or bridge mediated states.
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Affiliation(s)
- Jesus Nieto-Pescador
- Department of Physics and Astronomy, University of Delaware, Newark, DE
19716 USA
| | - Baxter Abraham
- Department of Chemistry and Biochemistry, University of Delaware, Newark,
DE 19716 USA
| | - Jingjing Li
- Department of Chemistry and Biochemistry, University of Delaware, Newark,
DE 19716 USA
| | - Alberto Batarseh
- Department of Chemistry, Rutgers University, Newark, NJ 07102 USA
| | - Robert A. Bartynski
- Department of Physics and Astronomy and Laboratory for Surface
Modification, Rutgers University, Piscataway, NJ 08854 USA
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, Newark, NJ 07102 USA
| | - Lars Gundlach
- Department of Chemistry and Biochemistry, University of Delaware, Newark,
DE 19716 USA
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13
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Affiliation(s)
- Elena Galoppini
- Department of Chemistry, Rutgers University-Newark, New Jersey 07102, USA
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14
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Chitre K, Batarseh A, Kopecky A, Fan H, Tang H, Lalancette R, Bartynski RA, Galoppini E. Synthesis of Zinc Tetraphenylporphyrin Rigid Rods with a Built-In Dipole. J Phys Chem B 2015; 119:7522-30. [DOI: 10.1021/jp5112982] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Keyur Chitre
- Chemistry
Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Alberto Batarseh
- Chemistry
Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Andrew Kopecky
- Chemistry
Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Hao Fan
- Chemistry
Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Hao Tang
- Chemistry
Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Roger Lalancette
- Chemistry
Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Robert A. Bartynski
- Department
of Physics and Astronomy and Laboratory for Surface Modification, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, United States
| | - Elena Galoppini
- Chemistry
Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
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15
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Ngo KT, Rochford J, Fan H, Batarseh A, Chitre K, Rangan S, Bartynski RA, Galoppini E. Photoelectrochemical properties of porphyrin dyes with a molecular dipole in the linker. Faraday Discuss 2015; 185:497-506. [DOI: 10.1039/c5fd00082c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The electronic properties of three porphyrin–bridge–anchor photosensitizers are reported with (1a, 1e, 3a and 3e) or without (2a and 2e) an intramolecular dipole in the bridge. The presence and orientation of the bridge dipole is hypothesized to influence the photovoltaic properties due to variations in the intrinsic dipole at the semiconductor–molecule interface. Electrochemical studies of the porphyrin–bridge–anchor dyes self-assembled on mesoporous nanoparticle ZrO2 films, show that the presence or direction of the bridge dipole does not have an observable effect on the electronic properties of the porphyrin ring. Subsequent photovoltaic measurements of nanostructured TiO2 semiconductor films in dye sensitized solar cells show a reduced photocurrent for photosensitizers 1a and 3a containing a bridge dipole. However, cooperative increased binding of the 1a + 3a co-sensitized device demonstrates that dye packing overrides any differences due to the presence of the small internal dipole.
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Affiliation(s)
- Ken T. Ngo
- Department of Chemistry
- University of Massachusetts Boston
- Boston
- USA
| | | | - Hao Fan
- Department of Chemistry
- Rutgers University
- Newark
- USA
| | | | - Keyur Chitre
- Department of Chemistry
- Rutgers University
- Newark
- USA
| | - Sylvie Rangan
- Department of Physics and Astronomy and Laboratory for Surface Modification
- Rutgers University
- Piscataway
- USA
| | - Robert A. Bartynski
- Department of Physics and Astronomy and Laboratory for Surface Modification
- Rutgers University
- Piscataway
- USA
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16
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Pikramenou Z, Weinstein J, Pan Q, Lewis F, Bassani DM, Würthner F, Moucheron C, Slota M, Díaz-Moscoso A, Karlsson J, Basílio N, Adams D, Scandola F, Bohne C, Lemon C, Campagna S, Rohacova J, Ohashi K, Plötz PA, Monti F, Kelly JM, Keane P, Gibson E, Lemercier G, Ruggi A, Cucinotta F, Gust D, Bradberry S, Vos J, Pistolis G, Mauro M, Tuite E, De Cola L, Ceroni P, Maneiro M, Galoppini E, Gunnlaugsson T. Self-organization of photo-active nanostructures: general discussion. Faraday Discuss 2015; 185:529-48. [DOI: 10.1039/c5fd90092a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Ceroni P, Pikramenou Z, Prodi L, Pan Q, Adams D, Weinstein J, Lewis F, Bohne C, Vlcek A, Bassani DM, de Silva AP, Moucheron C, Nocera D, Díaz-Moscoso A, Padilla M, Lemon C, Campagna S, Bradberry S, Galoppini E, Plötz PA, Kelly JM, Rohacova J, Harriman A, Keane P, Gust D, Vos J, Mauro M, De Cola L, Nambalan Sivaraman SK, Lemercier G, Osborne S, Monti F. Luminescence sensing and imaging: general discussion. Faraday Discuss 2015; 185:311-35. [DOI: 10.1039/c5fd90090e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Bohne C, Pan Q, Ceroni P, Börjesson K, Rohacova J, Lewis F, Vlcek A, Bassani DM, Würthner F, Sartorel A, de Silva AP, Nocera D, Scandola F, Lemon C, Allain C, Brudvig GW, Marchesan S, Sundstrom V, Campagna S, Sheehan SW, Plötz PA, Monti F, Kelly JM, Gibson E, Maneiro M, Harriman A, Ruggi A, Galoppini E, Thummel R, Weinstein J, Vos J, Ishitani O, Gust D, Díaz-Moscoso A. Natural and artificial photosynthesis: general discussion. Faraday Discuss 2015; 185:187-217. [DOI: 10.1039/c5fd90089a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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De Filippo CC, Tang H, Ravotto L, Bergamini G, Salice P, Mba M, Ceroni P, Galoppini E, Maggini M. Synthesis and Electronic Properties of 1,2‐Hemisquarimines and Their Encapsulation in a Cucurbit[7]uril Host. Chemistry 2014; 20:6412-20. [DOI: 10.1002/chem.201400039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Indexed: 01/15/2023]
Affiliation(s)
- Christian C. De Filippo
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy), Fax: (+) 30 0498275050
| | - Hao Tang
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, NJ ‐ 07102 (USA)
| | - Luca Ravotto
- Department of Chemistry “G. Ciamician”, Via Selmi 2, 40126 Bologna (Italy)
| | - Giacomo Bergamini
- Department of Chemistry “G. Ciamician”, Via Selmi 2, 40126 Bologna (Italy)
| | - Patrizio Salice
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy), Fax: (+) 30 0498275050
| | - Miriam Mba
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy), Fax: (+) 30 0498275050
| | - Paola Ceroni
- Department of Chemistry “G. Ciamician”, Via Selmi 2, 40126 Bologna (Italy)
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, NJ ‐ 07102 (USA)
| | - Michele Maggini
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy), Fax: (+) 30 0498275050
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20
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Lee CH, Chitre K, Galoppini E. Synthesis of Capped Tetrachelate Porphyrins: Towards “Insulation” of the Chromophore on Semiconductor Surfaces. J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.201000157] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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21
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Abstract
The copper-free click reaction was explored as a surface functionalization methodology for ZnO nanorod films grown by metal organic chemical vapor deposition (MOCVD). 11-Azidodecanoic acid was bound to ZnO nanorod films through the carboxylic acid moiety, leaving the azide group available for Cu-free click reaction with alkynes. The azide-functionalized layer was reacted with 1-ethynylpyrene, a fluorescent probe, and with alkynated biotin, a small biomolecule. The immobilization of pyrene on the surface was probed by fluorescence spectroscopy, and the immobilization of biotin was confirmed by binding with streptavidin-fluorescein isothiocyanate (streptavidin-FITC). The functionalized ZnO films were characterized by Fourier transform infrared attenuated total reflectance (FTIR-ATR), steady-state fluorescence emission, fluorescence microscopy, and field emission scanning electron microscopy (FESEM).
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Affiliation(s)
- Yan Cao
- Department of Chemistry, Rutgers, the State University of New Jersey, 73 Warren Street, Newark, New Jersey 07102, USA
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22
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Johansson PG, Zhang Y, Meyer GJ, Galoppini E. Homoleptic “Star” Ru(II) Polypyridyl Complexes: Shielded Chromophores to Study Charge-Transfer at the Sensitizer-TiO2 Interface. Inorg Chem 2013; 52:7947-57. [DOI: 10.1021/ic4004565] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Patrik G. Johansson
- Department of Chemistry and Material Science & Engineering, John Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Yongyi Zhang
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
| | - Gerald J. Meyer
- Department of Chemistry and Material Science & Engineering, John Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Elena Galoppini
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
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Johansson PG, Kopecky A, Galoppini E, Meyer GJ. Distance Dependent Electron Transfer at TiO2 Interfaces Sensitized with Phenylene Ethynylene Bridged RuII–Isothiocyanate Compounds. J Am Chem Soc 2013; 135:8331-41. [DOI: 10.1021/ja402193f] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Patrik G. Johansson
- Departments of Chemistry and Materials Science & Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Andrew Kopecky
- Department of Chemistry, Rutgers University, 73 Warren St, Newark, New Jersey
07102, United States
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, 73 Warren St, Newark, New Jersey
07102, United States
| | - Gerald J. Meyer
- Departments of Chemistry and Materials Science & Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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24
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Chen Y, Klimczak A, Galoppini E, Lockard JV. Structural interrogation of a cucurbit[7]uril-ferrocene host–guest complex in the solid state: a Raman spectroscopy study. RSC Adv 2013. [DOI: 10.1039/c2ra21584e] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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25
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Chitre KP, Guillén E, Yoon AS, Galoppini E. Synthesis of Homoleptic Ruthenium “Star” Complexes by Click Reaction for TiO2Sensitization. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201200896] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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26
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Abstract
A stepwise surface functionalization methodology was applied to nanostructured ZnO films grown by metal organic chemical vapor deposition (MOCVD) having three different surface morphologies (i.e., nanorod layers (ZnO films-N), rough surface films (ZnO films-R), and planar surface films (ZnO films-P). The films were grown on glass substrates and on the sensing area of a quartz crystal microbalance (nano-QCM). 16-(2-Pyridyldithiol)-hexadecanoic acid (PDHA) was bound to ZnO films-N, -R, and -P through the carboxylic acid unit, followed by a nucleophilic displacement of the 2-pyridyldithiol moiety by single-stranded DNA capped with a thiol group (SH-ssDNA). The resulting ssDNA-functionalized films were hybridized with complementary ssDNA tagged with fluorescein (ssDNA-Fl). In a selectivity control experiment, no hybridization occurred upon treatment with non complementary DNA. The ZnO films' surface functionalization, characterized by FT-IR-ATR and fluorescence spectroscopy and detected on the nano-QCM, was successful on films-N and -R but was barely detectable on the planar surface of films-P.
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Affiliation(s)
- Yan Cao
- Department of Chemistry, Rutgers, The State University of New Jersey, Newark, New Jersey 07102, United States
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27
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Porel M, Klimczak A, Freitag M, Galoppini E, Ramamurthy V. Photoinduced electron transfer across a molecular wall: coumarin dyes as donors and methyl viologen and TiO2 as acceptors. Langmuir 2012; 28:3355-3359. [PMID: 22303867 DOI: 10.1021/la300053r] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Coumarins C-153, C-480, and C-1 formed 1:2 (guest:host) complexes with a water-soluble cavitand having eight carboxylic acid groups (OA) in aqueous borate buffer solution. The complexes were photoexcited in the presence of electron acceptors (methyl viologen, MV(2+), or TiO(2)) to probe the possibility of electron transfer between a donor and an acceptor physically separated by a molecular wall. In solution at basic pH, the dication MV(2+) was associated to the exterior of the complex C-153@OA(2), as suggested by diffusion constants (~1.2 × 10(-6) cm(2)/s) determined by DOSY NMR. The fluorescence of C-153@OA(2) was quenched in the presence of increasing amounts of MV(2+) and Stern-Volmer plots of I(o)/I and τ(o)/τ vs [MV(2+)] indicated that the quenching was static. As per FT-IR-ATR spectra, the capsule C-153@OA(2) was bound to TiO(2) nanoparticle films. Selective excitation (λ(exc) = 420) of the above bound complex resulted in fluorescence quenching. When adsorbed on insulating ZrO(2) nanoparticle films, excitation of the complex resulted in a broad fluorescence spectrum centered at 500 nm and consistent with C-153 being within the lipophilic capsule interior. Consistent with the above results, colloidal TiO(2) quenched the emission while colloidal ZrO(2) did not.
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Affiliation(s)
- Mintu Porel
- Department of Chemistry, University of Miami, Coral Gables, Florida 33124, USA
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28
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Freitag M, Gundlach L, Piotrowiak P, Galoppini E. Fluorescence Enhancement of Di-p-tolyl Viologen by Complexation in Cucurbit[7]uril. J Am Chem Soc 2012; 134:3358-66. [DOI: 10.1021/ja206833z] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Marina Freitag
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
| | - Lars Gundlach
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
| | - Piotr Piotrowiak
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
| | - Elena Galoppini
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey
07102, United States
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29
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Persson P, Knitter M, Galoppini E. Light-harvesting and electronic contacting capabilities of Ru(ii) Ipa rod and star complexes–first principles predictions. RSC Adv 2012. [DOI: 10.1039/c2ra21240d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
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30
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Johansson PG, Zhang Y, Abrahamsson M, Meyer GJ, Galoppini E. Slow excited state injection and charge recombination at star-shaped ruthenium polypyridyl compounds—TiO2 interfaces. Chem Commun (Camb) 2011; 47:6410-2. [DOI: 10.1039/c1cc11210d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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31
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Abstract
Methylviologen (1,1'-dimethyl-4,4'-bipyridinium dichloride, MV(2+), 1) and a newly synthesized viologen derivative (1-methyl-1'-p-tolyl-4,4'-bipyridinium dichloride, MTV(2+), 2) were encapsulated in a macrocyclic host, cucur[7]bituril, CB[7]. The complexes MV(2+)@CB[7] and MTV(2+)@CB[7] were physisorbed on the surface of TiO(2) nanoparticles films. Viologens 1 or 2, which do not have anchoring group substituents, did not bind to the films in the absence of CB[7]. The complexation into CB[7] was monitored by (1)H NMR spectra in D(2)O solutions, which showed an upfield shift of the viologen protons upon encapsulation. TiO(2) films functionalized with the complexes were studied by FT-IR-ATR and UV-vis absorption. The electrochemical and spectroelectrochemical properties of MV(2+)@CB[7] and MTV(2+)@CB[7] were studied in solution and in electrochromic windows, where the complexes were bound to TiO(2) films cast on FTO. The windows prepared from MV(2+)@CB[7]/TiO(2)/FTO and MTV(2+)@CB[7]/TiO(2)/FTO electrodes showed reversible, sharp (colorless to purple), and fast color switching upon application of -0.8 V. Electrochromic behavior was not observed in control windows prepared in the absence of CB[7].
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Affiliation(s)
- Marina Freitag
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, USA
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32
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Nemec H, Rochford J, Taratula O, Galoppini E, Kuzel P, Polívka T, Yartsev A, Sundström V. Influence of the electron-cation interaction on electron mobility in dye-sensitized ZnO and TiO2 nanocrystals: a study using ultrafast terahertz spectroscopy. Phys Rev Lett 2010; 104:197401. [PMID: 20866996 DOI: 10.1103/physrevlett.104.197401] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Indexed: 05/27/2023]
Abstract
Charge transport and recombination in nanostructured semiconductors are poorly understood key processes in dye-sensitized solar cells. We have employed time-resolved spectroscopies in the terahertz and visible spectral regions supplemented with Monte Carlo simulations to obtain unique information on these processes. Our results show that charge transport in the active solar cell material can be very different from that in nonsensitized semiconductors, due to strong electrostatic interaction between injected electrons and dye cations at the surface of the semiconductor nanoparticle. For ZnO, this leads to formation of an electron-cation complex which causes fast charge recombination and dramatically decreases the electron mobility even after the dissociation of the complex. Sensitized TiO2 does not suffer from this problem due to its high permittivity efficiently screening the charges.
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Affiliation(s)
- H Nemec
- Department of Chemical Physics, Lund University, Getingevägen 60, Box 124, 221 00 Lund, Sweden
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Affiliation(s)
- Chi-Hang Lee
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102
| | - Elena Galoppini
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102
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34
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Lee CH, Zhang Y, Romayanantakit A, Galoppini E. Modular synthesis of ruthenium tripodal system with variable anchoring groups positions for semiconductor sensitization. Tetrahedron 2010. [DOI: 10.1016/j.tet.2010.04.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
The study of interfacial charge-transfer processes (sensitization) of a dye bound to large-bandgap nanostructured metal oxide semiconductors, including TiO(2), ZnO, and SnO(2), is continuing to attract interest in various areas of renewable energy, especially for the development of dye-sensitized solar cells (DSSCs). The scope of this Review is to describe how selected model sensitizers prepared from organic polyaromatic hydrocarbons have been used over the past 15 years to elucidate, through a variety of techniques, fundamental aspects of heterogeneous charge transfer at the surface of a semiconductor. This Review does not focus on the most recent or efficient dyes, but rather on how model dyes prepared from aromatic hydrocarbons have been used, over time, in key fundamental studies of heterogeneous charge transfer. In particular, we describe model chromophores prepared from anthracene, pyrene, perylene, and azulene. As the level of complexity of the model dye-bridge-anchor group compounds has increased, the understanding of some aspects of very complex charge transfer events has improved. The knowledge acquired from the study of the described model dyes is of importance not only for DSSC development but also to other fields of science for which electronic processes at the molecule/semiconductor interface are relevant.
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Affiliation(s)
- Yongyi Zhang
- Department of Chemistry, Rutgers, the State University of New Jersey, Newark, NJ 07102,USA
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36
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Zastrow M, Thyagarajan S, Ahmed S, Haase P, Seedorff S, Gelman D, Wachtveitl J, Galoppini E, Rück-Braun K. Efficient Preparation of Photoswitchable Dithienylethene-Linker-Conjugates by Palladium-Catalyzed Coupling Reactions of Terminal Alkynes with Thienyl Chlorides and Other Aryl Halides. Chem Asian J 2010; 5:1202-12. [DOI: 10.1002/asia.200900503] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Thyagarajan S, Galoppini E, Persson P, Giaimuccio JM, Meyer GJ. Large footprint pyrene chromophores anchored to planar and colloidal metal oxide thin films. Langmuir 2009; 25:9219-9226. [PMID: 19719222 DOI: 10.1021/la9007679] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Sensitization and binding of a large footprint pyrene chromophore to planar (sapphire) and colloidal metal oxide films (TiO2 and ZrO2) is investigated. The model compound combines a 1-pyrenyl-ethynylenephenylene unit with a new adamantane-tripodal linker that binds to the surface. The linker design, combining a large footprint (approximately 2 nm2) of the tripodal linker with the meta position of the COOH anchoring groups, was suggested from atomistic models, and it aims to provide improved spacing control. The pyrene chromophore unit provides a probe of sensitizer-sensitizer interactions through its propensity to form excimers, unless neighboring pyrene units are sufficiently spaced (>or=3.5 A). Absorption and fluorescence studies, and a comparison with a pyrene-rigid rod model compound, suggest that the new tripodal anchor group allows spacing control on planar surfaces. On colloidal films, the linker provides spacing control at low surface coverage but sensitizer-sensitizer interactions are still observed on colloidal films at high surface coverage. Implications for the functionalization of metal oxide films in hybrid molecule-metal oxide semiconductor material systems are discussed.
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Affiliation(s)
- Sujatha Thyagarajan
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, USA
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38
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Taratula O, Galoppini E, Mendelsohn R, Reyes PI, Zhang Z, Duan Z, Zhong J, Lu Y. Stepwise functionalization of ZnO nanotips with DNA. Langmuir 2009; 25:2107-2113. [PMID: 19199718 DOI: 10.1021/la8026946] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A surface functionalization methodology for the development of ZnO nanotips biosensors that can be integrated with microelectronics was developed. Two types of long chain carboxylic acids linkers were employed for the functionalization of 0.5 mum thick MOCVD-grown ZnO nanotip films with single-stranded DNA (ssDNA), followed by hybridization with complementary ssDNA tagged with fluorescein. The ZnO functionalization strategy was developed for the fabrication of ZnO nanotips-linker-biomolecule films integrated with bulk acoustic wave (BAW) biosensors, and it involved three main steps. First, 16-(2-pyridyldithiol)hexadecanoic acid or N-(15-carboxypentadecanoyloxy)succinimide, both bifunctional C16 carboxylic acids, were bound to ZnO nanotip films through the COOH group, leaving at the opposite end of the alkyl chain a thiol group protected as a 2-pyridyl disulfide, or a carboxylic group protected as a N-succinimide, respectively. In the second step, ssDNA was covalently linked to each type of ZnO-linker film: the 2-pyridyl disulfide end group was substituted with 16 bases 5'-thiol-modified DNA (SH-ssDNA), and the N-succinimide ester end group was substituted with 16 bases 5'-amino-modified DNA (NH(2)-ssDNA). In the third step, the DNA-functionalized ZnO nanotip films were hybridized with complementary 5'-fluorescein ssDNA. The surface-modified ZnO nanotip films were characterized after each step by FT-IR-ATR, fluorescence emission spectroscopy, and fluorescence microscopy. This functionalization approach allows sequential reactions on the surface and, in principle, can be extended to numerous other molecules and biomolecules.
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Affiliation(s)
- Olena Taratula
- Department of Chemistry, Rutgers, The State University of New Jersey, 73 Warren Street, Newark, New Jersey 07102, USA
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39
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Pal SK, Sundström V, Galoppini E, Persson P. Calculations of interfacial interactions in pyrene-Ipa rod sensitized nanostructured TiO2. Dalton Trans 2009:10021-31. [DOI: 10.1039/b910880g] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Rochford J, Galoppini E. Zinc(II) tetraarylporphyrins anchored to TiO2, ZnO, and ZrO2 nanoparticle films through rigid-rod linkers. Langmuir 2008; 24:5366-5374. [PMID: 18410135 DOI: 10.1021/la703845u] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A series of six Zn(II) tetraphenylporphyrins (ZnTPP), with a phenyl (P) or oligophenyleneethynylene (OPE = (PE) n ) rigid-rod bridge varying in length (9-30 A) and terminated with an isophthalic acid (Ipa) anchoring unit, were prepared as model dyes for the study of sensitization processes on metal oxide semiconductor nanoparticle surfaces (MO(n) = TiO(2), ZnO, and insulating ZrO(2)). The dyes were designed such that the electronic properties of the central porphyrin chromophore remained consistent throughout the series, with the rigid-rod anchoring unit allowing each porphyrin unit to be located at a fixed distance from the metal oxide nanoparticle surface. Electronic communication between the porphyrin and the rigid-rod unit was not desired. Rigid-rod porphyrins ZnTPP-Ipa, ZnTPP-P-Ipa, ZnTPP-PE-Ipa, ZnTPP-(PE)(2)-Ipa, ZnTPP-(PE)(3)-Ipa, and ZnTMP-Ipa (with mesityl substituents on the porphyrin ring) were synthesized using combinations of mixed aldehyde condensations and Pd-catalyzed cross-coupling reactions. Their properties, in solution and bound, were compared with that of Zn(II) 5,10,15,20-tetra(4-carboxyphenyl)porphyrin ( p-ZnTCPP) as the reference compound. Solution UV-vis and steady-state fluorescence spectra for all six rigid-rod-Ipa porphyrins were almost identical to each other and to that of p-ZnTCPP. Cyclic voltammetry and differential pulse voltammetry scans of the methyl ester derivatives of the six rigid-rod-Ipa porphyrins, recorded in dichloromethane/electrolyte, exhibited redox behavior typical of ZnTPP porphyrins, with the first oxidation in the range +0.99 to 1.09 V vs NHE. All six rigid-rod-Ipa porphyrins and p-ZnTCPP were bound to metal oxide (MO(n) = TiO(2), ZnO, and insulating ZrO(2)) nanoparticle films. The Fourier transform infrared attenuated total reflectance spectra of all compounds bound to MO n films showed a broad band at 1553-1560 cm(-1) assigned to the v(CO(2)(-)) asymmetric stretching mode. Splitting of the Soret band into two bands at 411 and 423 nm in the UV-vis spectra of the bound compounds, and broadening and convergence of both fluorescence emission bands in the fluorescence spectra of the porphyrins bound to insulating ZrO(2) were also observed. Such changes were less evident for ZnTMP-Ipa, which has mesityl substituents on the porphyrin ring to prevent aggregation. Steady-state fluorescence emission of rigid-rod-Ipa porphyrins bound to TiO(2) and ZnO through the longest bridges (>14 A) showed residual fluorescence emission, while fluorescence quenching was observed for the shortest compounds.
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Affiliation(s)
- Jonathan Rochford
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, USA
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Giaimuccio JM, Rowley JG, Meyer GJ, Wang D, Galoppini E. Heavy atom effects on anthracene-rigid-rod excited states anchored to metal oxide nanoparticles. Chem Phys 2007. [DOI: 10.1016/j.chemphys.2007.07.039] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Thyagarajan S, Liu A, Famoyin OA, Lamberto M, Galoppini E. Tripodal pyrene chromophores for semiconductor sensitization: new footprint design. Tetrahedron 2007. [DOI: 10.1016/j.tet.2007.05.055] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Taratula O, Galoppini E, Wang D, Chu D, Zhang Z, Chen H, Saraf G, Lu Y. Binding studies of molecular linkers to ZnO and MgZnO nanotip films. J Phys Chem B 2007; 110:6506-15. [PMID: 16570948 DOI: 10.1021/jp0570317] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two bifunctional linkers, a rigid-rod p-ethynyl-isophthalic acid capped with a Ru(II)-polypyridyl complex and 3-mercaptopropionic acid, were covalently bound to ZnO nanotip films grown by metal-organic chemical vapor deposition (MOCVD) technology. This highly vertically aligned, crystalline form of ZnO had not been functionalized before. The binding was studied by Fourier transform (FT) IR and UV spectroscopies and probed, in the case of the Ru complex, by static and dynamic fluorescence quenching. The molecules did bind through the carboxylic acid groups, and the FT-IR attenuated total reflectance spectra are indicative of a bidentate carboxylate binding mode. Other molecules (heptanoic acid, isophthalic acid, and trimethoxy(2-phenylethyl)silane) were also bound to the ZnO nanotips. A comparison was made with epitaxial ZnO films grown by MOCVD and ZnO mesoporous films prepared from colloidal solutions to investigate the effect of the ZnO morphology. The ZnO nanotips were excellent binding substrates, particularly for the rigid-rod linker. Since ZnO films are etched at low pH (< 4), novel nanotip films made of ternary MgxZn1-xO, which is formed by alloying ZnO with MgO and is more resistant to acids, were developed. The MgxZn1-xO nanotip films were employed to use linkers with acidic groups and to study the effect of pH pretreatment of the surface on the binding.
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Affiliation(s)
- Olena Taratula
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, USA
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Rochford J, Chu D, Hagfeldt A, Galoppini E. Tetrachelate Porphyrin Chromophores for Metal Oxide Semiconductor Sensitization: Effect of the Spacer Length and Anchoring Group Position. J Am Chem Soc 2007; 129:4655-65. [PMID: 17385856 DOI: 10.1021/ja068218u] [Citation(s) in RCA: 227] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Four Zn(II)-tetra(carboxyphenyl)porphyrins in solution and bound to metal oxide (TiO2, ZnO, and ZrO2) nanoparticle films were studied to determine the effect of the spacer length and anchoring group position (para or meta) on their binding geometry and photoelectrochemical and photophysical properties. The properties of three types of anchoring groups (COOH and COONHEt3) for four Zn(II)-porphyrins (Zn(II)-5,10,15,20-tetra(4-carboxyphenyl)porphyrin (p-ZnTCPP), Zn(II)-5,10,15,20-tetra(3-carboxyphenyl)porphyrin (m-ZnTCPP), Zn(II)-5,10,15,20-tetra(3-(4-carboxyphenyl)phenyl)porphyrin (m-ZnTCP2P), and Zn(II)-5,10,15,20-tetra(3-ethynyl(4-carboxyphenyl)phenyl)porphyrin (m-ZnTC(PEP)P)) were compared. In m-ZnTCPP, m-ZnTCP2P, and m-ZnTC(PEP)P the four anchoring groups are in the meta position on the meso-phenyl rings of the porphyrin macrocycle, thus favoring a planar binding mode to the metal oxide surfaces. The three meta-substituted porphyrin salts have rigid spacer units of increasing length (phenyl (P), biphenyl (P2), and diphenylethynyl (PEP)) between the porphyrin ring and the carboxy anchoring groups, thus raising the macrocycle from the metal oxide surface. All porphyrins studied here, when bound to TiO2 and ZnO, exhibited quenching of the fluorescence emission, consistent with electron injection into the conduction band of the semiconductor. Steady-state UV-vis and fluorescence studies of p-ZnTCPP on insulating ZrO2 showed evidence of aggregation and exciton coupling. This was not observed in any of the meta-substituted porphyrins. The photoelectrochemical properties (IPCE, Voc, and Isc) of the porphyrins bound to TiO2 films in solar cells have been measured and rationalized with respect to the sensitizer binding geometry and distance from the surface.
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Affiliation(s)
- Jonathan Rochford
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, NJ 07102, USA
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Lundqvist MJ, Galoppini E, Meyer GJ, Persson P. Calculated Optoelectronic Properties of Ruthenium Tris-bipyridine Dyes Containing Oligophenyleneethynylene Rigid Rod Linkers in Different Chemical Environments. J Phys Chem A 2007; 111:1487-97. [PMID: 17279731 DOI: 10.1021/jp064219x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ruthenium tris-bipyridine dyes containing oligophenyleneethynylene (OPE) rigid rod linker groups ([Ru(bpy)3]2+, [Ru(bpy)2bpy-E-Ipa]2+, [Ru(bpy)2bpy-E-Ph-E-Ipa]2+, and [Ru(bpy)2bpy-E-Bco-E-Ipa]2+, where bpy = 2,2'-bipyridine, E = ethynylene, Ph = p-phenylene, Bco = bicyclo[2.2.2]octylene, and Ipa = isophthalic acid) have been investigated using DFT and TD-DFT calculations to elucidate the influence of the rigid rod on their optoelectronic properties. Experimentally observed differences in the optical absorption for the different complexes are discussed on the basis of TD-DFT simulated absorption spectra. A comparison of the calculated optoelectronic properties of [Ru(bpy)2bpy-E-Ph-E-Ipa]2+ in different chemical environments, that is, in different solvents and with or without counter ions, suggests that both the absorption spectra and the redox properties of the dyes with OPE rods are sensitive to the environment. The calculations show that spurious low-energy charge-transfer excitations present in the TD-DFT calculations of the extended systems in vacuum are removed when the environment is included in the calculations.
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Affiliation(s)
- M J Lundqvist
- Department of Quantum Chemistry, Uppsala University, Box 518, SE-75120 Uppsala, Sweden
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Galoppini E, Rochford J, Chen H, Saraf G, Lu Y, Hagfeldt A, Boschloo G. Fast Electron Transport in Metal Organic Vapor Deposition Grown Dye-sensitized ZnO Nanorod Solar Cells. J Phys Chem B 2006; 110:16159-61. [PMID: 16913732 DOI: 10.1021/jp062865q] [Citation(s) in RCA: 390] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electron transport in dye-sensitized solar cells with a MOCVD (metal organic vapor deposition)-grown ZnO nanorod array (ZnO-N) or a mesoporous film prepared from ZnO colloids (ZnO-C) as the working electrode was compared. The electrodes were of similar thickness (2 mum) and sensitized with zinc(II) meso-tetrakis(3-carboxyphenyl)porphyrin, while the electrolyte was I(-)/I(3)(-) in 3-methoxypropionitrile. Electron transport in the ZnO-C cells was comparable with that found for colloidal TiO(2) films (transport time approximately 10 ms) and was light intensity dependent. Electron transport in solar cells with ZnO-N electrodes was about 2 orders of magnitude faster ( approximately 30 mus). Thus, the morphology of the working ZnO electrode plays a key role for the electron transport properties.
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Taratula O, Rochford J, Piotrowiak P, Galoppini E, Carlisle RA, Meyer GJ. Pyrene-Terminated Phenylenethynylene Rigid Linkers Anchored to Metal Oxide Nanoparticles. J Phys Chem B 2006; 110:15734-41. [PMID: 16898719 DOI: 10.1021/jp0623847] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phenylenethynylene (PE) rigid linkers (para and meta) were used to anchor pyrene to the surface of TiO2 (anatase) and ZrO2 nanoparticle thin films through the two COOH groups of an isophthalic acid (Ipa) unit. Four chromophore-linker models were studied in solution and bound. Two are novel meta-pyrene-PE linker systems: dimethyl 5-(3-(1-pyrenylethynyl)phenylethynyl)-isophthalate, carrying one pyrene, and dimethyl 5-(bis-3,5-(1-pyrenylethynyl)phenylethynyl)-isophthalate, carrying two. These were compared with para rigid-rods dimethyl 5-(1-pyrenylethynyl)isophthalate and dimethyl 5-(4-(1-pyrenylethynyl)phenylethynyl)-isophthalate, each carrying one pyrene but varying in length. The length of the PE linkers and the para or meta substitution influence the photophysical properties of the compounds. The extinction coefficient increased, and the long wavelength absorbance of the pyrene chromophore was shifted to the red with increasing conjugation. Compared to unsubstituted pyrene, the pyrene-linker systems were characterized by short fluorescence lifetimes (tau approximately 2 ns in tetrahydrofuran solutions), but quantum yields were close to unity. ZINDO/S CI calculations attribute this effect to a switching in the order of the two lowest-lying singlet states of pyrene. High surface coverages, approximately 10(-8) mol/cm2, and carboxylate binding modes on nanostructured TiO2 films were obtained in all cases. The appearance of a pyrene excimer emission on ZrO2, an insulator, indicates that the pyrene-linker system is closely packed (Py-Py < 4 A) on the surface. The fluorescence emission on TiO2 was completely quenched, consistent with quantitative and rapid electron injection into the semiconductor indicating that the pyrene excimer acts as a sensitizer. Photoelectrochemical studies in regenerative solar cells with I3-/I- as the redox mediator indicated near-quantitative conversion of absorbed photons into an electrical current.
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Affiliation(s)
- Olena Taratula
- Chemistry Department, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, USA
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Abstract
The sensitizers [Ru(bpy)2(deeb)](PF6)2 (1), [Ru(bpy)2(bpy)-(E-Ph)-Ad](PF6)2 (2), and [Ru(bpy)2(bpy)-(E-Ph)2-Ad](PF6)2 (3), where deeb is 4,4'-(COOCH2CH3)2-2,2'-bipyridine, E-Ph is phenylethynyl, and Ad are tripod shaped bpy ligands based on 1,3,5,7-tetraphenyladamantane, were anchored to mesoporous nanocrystalline (anatase) TiO2 thin films and studied in regenerative solar cells with 0.1 M LiI/0.005 M I2 dichloromethane electrolyte. Over three decades of 488 nm irradiance, the open circuit photovoltage increased markedly with the distance between the Ru center and the surface binding groups, 1 (7 A) < 2 (18 A) < 3 (24 A). The diode equation accurately models the irradiance dependent data and indicates that the TiO2(e-) --> I3- (and/or I2) charge recombination rate constants were decreased by a factor of 20 for 2/TiO2 and 280 for 3/TiO2 relative to 1/TiO2. The results suggest that control of the sensitizer-TiO2 orientation is important for efficient power optimization.
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Ernstorfer R, Felber S, Storck W, Galoppini E, Wei Q, Willig F. Distance dependence of heterogeneous electron transfer probed in ultra-high vacuum with femtosecond transient absorption. Res Chem Intermed 2005. [DOI: 10.1163/1568567054908970] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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