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Ezquerra Riega SD, Gutierrez Suburu ME, Rodríguez HB, Lantaño B, Kleinschmidt M, Marian CM, Strassert CA. A Case-Study on the Photophysics of Chalcogen-Substituted Zinc(II) Phthalocyanines. Chemistry 2024:e202304083. [PMID: 38647352 DOI: 10.1002/chem.202304083] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Indexed: 04/25/2024]
Abstract
Singlet dioxygen has been widely applied in different disciplines such as medicine (photodynamic therapy or blood sterilization), remediation (wastewater treatment) or industrial processes (fine chemicals synthesis). Particularly, it can be conveniently generated by energy transfer between a photosensitizer's triplet state and triplet dioxygen upon irradiation with visible light. Among the best photosensitizers, substituted zinc(II) phthalocyanines are prominent due to their excellent photophysical properties, which can be tuned by structural modifications, such as halogen- and chalcogen-atom substitution. These patterns allow for the enhancement of spin-orbit coupling, commonly attributed to the heavy atom effect, which correlates with the atomic number ( Z ${Z}$ ) and the spin-orbit coupling constant ( ζ ${\zeta }$ ) of the introduced heteroatom. Herein, a fully systematic analysis of the effect exerted by chalcogen atoms on the photophysical characteristics (absorption and fluorescence properties, lifetimes and singlet dioxygen photogeneration), involving 30 custom-made β-tetrasubstituted chalcogen-bearing zinc(II) phthalocyanines is described and evaluated regarding the heavy atom effect. Besides, the intersystem crossing rate constants are estimated by several independent methods and a quantitative profile of the heavy atom is provided by using linear correlations between relative intersystem crossing rates and relative atomic numbers. Good linear trends for both intersystem crossing rates (S1-T1 and T1-S0) were obtained, with a dependency on the atomic number and the spin-orbit coupling constant scaling asZ 0 . 4 ${{Z}^{0.4}}$ andζ 0 . 2 ${{\zeta }^{0.2}}$ , respectively The trend shows to be independent of the solvent and temperature.
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Affiliation(s)
- Sergio D Ezquerra Riega
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Ciencias Químicas, Junín 956, C1113AAD, Buenos Aires, Argentina
- Universidad de Buenos Aires, Instituto de Tecnología Farmacéutica y Biofarmacia (InTecFyB), Junín 956, C1113AAD, Buenos Aires, Argentina
- CONICET - Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE); Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, UBA., Ciudad Universitaria Pab. II, C1428EHA, Buenos Aires, Argentina
| | - Matías E Gutierrez Suburu
- Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstraße 28/30, D-48149, Münster, Germany
- CeNTech, SoN, CiMIC, Universität Münster, Heisenbergstraße 11, D-48149, Münster, Germany
| | - Hernán B Rodríguez
- CONICET - Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE); Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, UBA., Ciudad Universitaria Pab. II, C1428EHA, Buenos Aires, Argentina
| | - Beatriz Lantaño
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Ciencias Químicas, Junín 956, C1113AAD, Buenos Aires, Argentina
- Universidad de Buenos Aires, Instituto de Tecnología Farmacéutica y Biofarmacia (InTecFyB), Junín 956, C1113AAD, Buenos Aires, Argentina
| | - Martin Kleinschmidt
- Institut für Theoretische Chemie und Computerchemie, Fakultät für Mathematik und Naturwissenschaften, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Christel M Marian
- Institut für Theoretische Chemie und Computerchemie, Fakultät für Mathematik und Naturwissenschaften, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Cristian A Strassert
- Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstraße 28/30, D-48149, Münster, Germany
- CeNTech, SoN, CiMIC, Universität Münster, Heisenbergstraße 11, D-48149, Münster, Germany
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Toum Terrones Y, Torresán MF, Mirenda M, Rodríguez HB, Wolosiuk A. Photoactive Red Fluorescent SiO 2 Nanoparticles Based on Controlled Methylene Blue Aggregation in Reverse Microemulsions. Langmuir 2022; 38:6786-6797. [PMID: 35609298 DOI: 10.1021/acs.langmuir.1c02458] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We present a reverse microemulsion synthesis procedure for incorporating methylene blue (MB), a known FDA-approved type-II red-absorbing photosensitizer and 1O2 generator, into the matrix of hydrophobic-core/hydrophilic-shell SiO2 nanoparticles. Different synthesis conditions were explored with the aim of controlling the entrapped-dye aggregation at high dye loadings in the hydrophobic protective core; minimizing dye aggregation ensured highly efficient photoactive nanoentities for 1O2 production. Monitoring the synthesis in real time using UV-vis absorption allowed tracking of the dye aggregation process. In particular, silica nanoparticles (MB@SiO2 NPs) of ∼50 nm diameter size with a high local entrapped-MB concentration (∼10-2 M, 1000 MB molecules per NP) and a moderate proportion of dye aggregation were obtained. The as-prepared MB@SiO2 NPs showed a high singlet oxygen photogeneration efficiency (ΦΔ = 0.30 ± 0.05), and they can be also considered as red fluorescent probes (ΦF ∼ 0.02, λmax ∼ 650 nm). The distinctive photophysical and photochemical characteristics of the synthesized NPs reveal that the reverse microemulsion synthesis procedure offers an interesting strategy for the development of complex theranostic nano-objects for photodynamic therapy.
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Affiliation(s)
- Yamili Toum Terrones
- Gerencia Química - Instituto de Nanociencia y Nanotecnología (INN - CONICET), Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, CONICET, Av. Gral. Paz 1499, B1650 KNA San Martín, Buenos Aires, Argentina
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP-CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Diagonal 113 y 64 S/N, B1904 DPI La Plata, Argentina
| | - María Fernanda Torresán
- Gerencia Química - Instituto de Nanociencia y Nanotecnología (INN - CONICET), Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, CONICET, Av. Gral. Paz 1499, B1650 KNA San Martín, Buenos Aires, Argentina
| | - Martín Mirenda
- Gerencia Química - Instituto de Nanociencia y Nanotecnología (INN - CONICET), Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, CONICET, Av. Gral. Paz 1499, B1650 KNA San Martín, Buenos Aires, Argentina
| | - Hernán B Rodríguez
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), CONICET - Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428 EHA Buenos Aires, Argentina
- Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428 EHA Buenos Aires, Argentina
| | - Alejandro Wolosiuk
- Gerencia Química - Instituto de Nanociencia y Nanotecnología (INN - CONICET), Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, CONICET, Av. Gral. Paz 1499, B1650 KNA San Martín, Buenos Aires, Argentina
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Córdoba D, Rodríguez HB, Calvo EJ. Singlet Oxygen Formation during the Oxygen Reduction Reaction in DMSO LiTFSI on Lithium Air Battery Carbon Electrodes. ChemistrySelect 2019. [DOI: 10.1002/slct.201904112] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Daniel Córdoba
- DQIAyQF/INQUIMAEFacultad de Ciencias Exactas y NaturalesUniv. Buenos Aires Pabellón 2, Ciudad Universitaria Buenos Aires Argentina
| | - Hernán B. Rodríguez
- INIFTA (UNLP-CONICET)Facultad de Ciencias ExactasUniversidad Nacional de La Plata.Diagonal 113 y 64 S/N B1904DPI La Plata Argentina
| | - Ernesto J. Calvo
- DQIAyQF/INQUIMAEFacultad de Ciencias Exactas y NaturalesUniv. Buenos Aires Pabellón 2, Ciudad Universitaria Buenos Aires Argentina
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Abstract
The study of the interaction of light with systems at high dye concentrations implies a great challenge because several factors, such as emission reabsorption, dye aggregation, and energy trapping, hinder rationalization and interpretation of the involved photophysical processes. Space constraints induce dye interaction even in the absence of ground state stabilization of dimers and oligomers. At distances on the order of 1 nm, statistical energy traps are usually observed. At longer distances, excited state energy transfer takes place. Most of these factors do not result in ground state spectroscopic changes. Rather, fluorescence phenomena such as inner filter effects, concentration-dependent Stokes' shifts, and changes in quantum yields and decay times are evidenced. Photophysical studies are commonly carried out at high dilution, to minimize dye-dye interactions and emission reabsorption, and in the absence of light scattering. Under these conditions, the physical description of the system becomes rather simple. Fluorescence and triplet quantum yields become molecular properties and can be easily related to ratios of rate constants. However, many systems containing dyes able to fulfill specific functions, whether man-made or biological, are far from being dilute and scattering-free. The photosynthetic apparatus is a paradigmatic example. It is clear that isolation of components allows gathering relevant information about complex systems. However, knowledge of the photophysical behavior in the unaltered environment is essential in most cases. Complexity generally increases when light scattering is present. Despite that, our experience shows that light scattering, when correctly handled, may even simplify the task of unraveling molecular parameters. We show that methods and models aiming at the determination and interpretation of fluorescence and triplet quantum yields as well as energy transfer efficiencies can be developed on the basis of simple light-scattering theories. Photophysical studies were extended to thin films and layer-by-layer assemblies. Procedures are presented for the evaluation of fluorescence reabsorption in concentrated fluid solutions up to the molar level, which are being applied to ionic liquids, in which the emitting species are the bulk ions. Fluorescence reabsorption models proved to be useful in the interpretation of the photophysics of living organisms such as plant leaves and fruits. These new tools allowed the assessment of chlorophyll fluorescence at the chloroplast, leaf and canopy levels, with implications in remote sensing and the development of nondestructive optical methods.
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Affiliation(s)
- Hernán B. Rodríguez
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA, UNLP-CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Diagonal 113 y 64 S/N, B1904DPI La Plata, Argentina
| | - Martín Mirenda
- Gerencia Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica (CNEA-CONICET), Av. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires, Argentina
| | - M. Gabriela Lagorio
- CONICET - Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria Pab. II, C1428EHA Buenos Aires, Argentina
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Enrique San Román
- CONICET - Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria Pab. II, C1428EHA Buenos Aires, Argentina
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
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Litman YE, Rodríguez HB, Braslavsky SE, San Román E. Photophysics of Xanthene Dyes at High Concentrations in Solid Environments: Charge Transfer Assisted Triplet Formation. Photochem Photobiol 2018; 94:865-874. [DOI: 10.1111/php.12978] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 07/01/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Yair E. Litman
- Departamento de Química Inorgánica, Analítica y Química Física; Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires Argentina
| | - Hernán B. Rodríguez
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA); CCT-La Plata-CONICET; Universidad Nacional de La Plata (UNLP); La Plata Argentina
| | - Silvia E. Braslavsky
- Departamento de Química Inorgánica, Analítica y Química Física; Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires Argentina
- Instituto de Química Física de los Materiales; Medio Ambiente y Energía (INQUIMAE); CONICET - Universidad de Buenos Aires; Buenos Aires Argentina
- Max Planck Institute for Chemical Energy Conversion; Mülheim an der Ruhr Germany
| | - Enrique San Román
- Departamento de Química Inorgánica, Analítica y Química Física; Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires Argentina
- Instituto de Química Física de los Materiales; Medio Ambiente y Energía (INQUIMAE); CONICET - Universidad de Buenos Aires; Buenos Aires Argentina
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Ezquerra Riega SD, Rodríguez HB, San Román E. Rose bengal in poly(2-hydroxyethyl methacrylate) thin films: self-quenching by photoactive energy traps. Methods Appl Fluoresc 2017; 5:014010. [PMID: 28276341 DOI: 10.1088/2050-6120/aa61ae] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The effect of dye concentration on the fluorescence,ΦF, and singlet molecular oxygen,ΦΔ, quantum yields of rose bengal loaded poly(2-hydroxyethyl methacrylate) thin films (∼200 nm thick) was investigated, with the aim of understanding the effect of molecular interactions on the photophysical properties of dyes in crowded constrained environments. Films were characterized by absorption and fluorescence spectroscopy, singlet molecular oxygen (1O2) production was quantified using a chemical monitor, and the triplet decay was determined by laser flash-photolysis. For the monomeric dilute dye, ΦF = 0.05 ± 0.01 and ΦΔ = 0.76 ± 0.14. The effect of humidity and the photostability of the dye were also investigated. Spectral changes in absorption and fluorescence in excess of 0.05 M and concentration self-quenching after 0.01 M are interpreted in the context of a quenching radius model. Calculations of energy migration and trapping rates were performed assuming random distribution of the dye. Best fits of fluorescence quantum yields with concentration are obtained in the whole concentration range with a quenching radius r Q = 1.5 nm, in the order of molecular dimensions. Agreement is obtained only if dimeric traps are considered photoactive, with an observed fluorescence quantum yield ratio ΦF,trap/ΦF,monomer ≈ 0.35. Fluorescent traps are capable of yielding triplet states and 1O2. Results show that the excited state generation efficiency, calculated as the product between the absorption factor and the fluorescence quantum yield, is maximized at around 0.15 M, a very high concentration for random dye distributions. Relevant information for the design of photoactive dyed coatings is provided.
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Affiliation(s)
- Sergio D Ezquerra Riega
- CONICET-Universidad de Buenos Aires, Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), Ciudad Universitaria, Pab. II, Buenos Aires, Argentina
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Krimer NI, Rodrigues D, Rodríguez HB, Mirenda M. Steady-State Fluorescence of Highly Absorbing Samples in Transmission Geometry: A Simplified Quantitative Approach Considering Reabsorption Events. Anal Chem 2016; 89:640-647. [DOI: 10.1021/acs.analchem.6b02819] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicolás I. Krimer
- Gerencia Química,
Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica (CNEA-CONICET), Av. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires, Argentina
| | - Darío Rodrigues
- Gerencia Química,
Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica (CNEA-CONICET), Av. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires, Argentina
| | - Hernán B. Rodríguez
- Instituto
de Investigaciones Fisicoquímicas Teóricas y Aplicadas
(INIFTA, UNLP-CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4, (1900) La Plata, Argentina
- Departamento
de Química Inorgánica, Analítica y Química
Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA, Buenos Aires, Argentina
| | - Martín Mirenda
- Gerencia Química,
Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica (CNEA-CONICET), Av. Gral. Paz 1499, B1650KNA San Martín, Buenos Aires, Argentina
- Departamento
de Química Inorgánica, Analítica y Química
Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA, Buenos Aires, Argentina
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Litman Y, Rodríguez HB, San Román E. Tuning the concentration of dye loaded polymer films for maximum photosensitization efficiency: phloxine B in poly(2-hydroxyethyl methacrylate). Photochem Photobiol Sci 2016; 15:80-5. [DOI: 10.1039/c5pp00360a] [Citation(s) in RCA: 14] [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: 11/21/2022]
Abstract
Excitation of a dye confined in a polymeric matrix leads to energy trapping at high concentrations.
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Affiliation(s)
- Yair Litman
- INQUIMAE (UBA-CONICET)/DQIAyQF
- Facultad de Ciencias Exactas y Naturales
- Universidad de Buenos Aires
- Buenos Aires
- Argentina
| | - Hernán B. Rodríguez
- INQUIMAE (UBA-CONICET)/DQIAyQF
- Facultad de Ciencias Exactas y Naturales
- Universidad de Buenos Aires
- Buenos Aires
- Argentina
| | - Enrique San Román
- INQUIMAE (UBA-CONICET)/DQIAyQF
- Facultad de Ciencias Exactas y Naturales
- Universidad de Buenos Aires
- Buenos Aires
- Argentina
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Litman Y, Voss MG, Rodríguez HB, San Román E. Effect of Concentration on the Formation of Rose Bengal Triplet State on Microcrystalline Cellulose: A Combined Laser-Induced Optoacoustic Spectroscopy, Diffuse Reflectance Flash Photolysis, and Luminescence Study. J Phys Chem A 2014; 118:10531-7. [DOI: 10.1021/jp5045095] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Yair Litman
- INQUIMAE
(UBA-CONICET)/DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Buenos Aires, Argentina
| | - Matthew G. Voss
- INQUIMAE
(UBA-CONICET)/DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Buenos Aires, Argentina
| | - Hernán B. Rodríguez
- INQUIMAE
(UBA-CONICET)/DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Buenos Aires, Argentina
- INIFTA
(UNLP-CONICET), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Diag. 113 y Calle 64, La Plata, Argentina
| | - Enrique San Román
- INQUIMAE
(UBA-CONICET)/DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Buenos Aires, Argentina
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Rodríguez HB, San Román E. Effect of Concentration on the Photophysics of Dyes in Light-Scattering Materials. Photochem Photobiol 2013; 89:1273-82. [DOI: 10.1111/php.12107] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 05/22/2013] [Indexed: 01/30/2023]
Affiliation(s)
- Hernán B. Rodríguez
- INIFTA, Facultad de Ciencias Exactas; Universidad Nacional; La Plata Argentina
| | - Enrique San Román
- INQUIMAE / DQIAyQF, Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Argentina
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Rodríguez HB, Di Iorio Y, Meichtry JM, Grela MA, Litter MI, San Román E. Evidence on dye clustering in the sensitization of TiO2 by aluminum phthalocyanine. Photochem Photobiol Sci 2013; 12:1984-90. [DOI: 10.1039/c3pp50191d] [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: 11/21/2022]
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Rodríguez HB, Román ES, Duarte P, Machado IF, Vieira Ferreira LF. Eosin Y Triplet State as a Probe of Spatial Heterogeneity in Microcrystalline Cellulose. Photochem Photobiol 2012; 88:831-9. [DOI: 10.1111/j.1751-1097.2012.01152.x] [Citation(s) in RCA: 11] [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: 11/27/2022]
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Llansola Portolés MJ, Gara PMD, Kotler ML, Bertolotti S, San Román E, Rodríguez HB, Gonzalez MC. Silicon nanoparticle photophysics and singlet oxygen generation. Langmuir 2010; 26:10953-10960. [PMID: 20491505 DOI: 10.1021/la100980x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The effect of molecular oxygen and water on the blue photoluminescence of silicon nanoparticles synthesized by anodic oxidation of silicon wafers and surface functionalized with 2-methyl 2-propenoic acid methyl ester is investigated. The particles of 3 +/- 1 nm diameter and a surface composition of Si(3)O(6)(C(5)O(2)H(8)) exhibit room-temperature luminescence in the wavelength range 300-600 nm upon excitation with 300-400 nm light. The luminescence shows vibronic resolution and high quantum yields in toluene suspensions, while a vibronically unresolved spectrum and lower emission quantum yields are observed in aqueous suspensions. The luminescence intensity, though not the spectrum features, depends on the presence of dissolved O(2). Strikingly, the luminescence decay time on the order of 1 ns does not depend on the solvent or on the presence of O(2). To determine the mechanisms involved in these processes, time-resolved and steady-state experiments are performed. These include low-temperature luminescence, heavy atom effect, singlet molecular oxygen ((1)O(2)) phosphorescence detection, reaction of specific probes with (1)O(2), and determination of O(2) and N(2) adsorption isotherms at 77 K. The results obtained indicate that physisorbed O(2) is capable of quenching nondiffusively the particle luminescence at room temperature. The most probable mechanism for (1)O(2) generation involves the energy transfer from an exciton singlet state to O(2) to yield an exciton triplet of low energy (<0.98 eV) and (1)O(2). In aqueous solutions, excited silicon nanoparticles are able to reduce methylviologen on its surface.
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López SG, Worringer G, Rodríguez HB, San Román E. Trapping of Rhodamine 6G excitation energy on cellulose microparticles. Phys Chem Chem Phys 2010; 12:2246-53. [DOI: 10.1039/b919583a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [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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Meichtry JM, Rivera V, Di Iorio Y, Rodríguez HB, Román ES, Grela MA, Litter MI. Photoreduction of Cr(vi) using hydroxoaluminiumtricarboxymonoamide phthalocyanine adsorbed on TiO2. Photochem Photobiol Sci 2009; 8:604-12. [DOI: 10.1039/b816441j] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [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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Braslavsky SE, Fron E, Rodríguez HB, Román ES, Scholes GD, Schweitzer G, Valeur B, Wirz J. Pitfalls and limitations in the practical use of Förster's theory of resonance energy transfer. Photochem Photobiol Sci 2008; 7:1444-8. [DOI: 10.1039/b810620g] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [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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Rodríguez HB, Román ES. Energy Transfer from Chemically Attached Rhodamine 101 to Adsorbed Methylene Blue on Microcrystalline Cellulose Particles†. Photochem Photobiol 2007; 83:547-55. [PMID: 17029496 DOI: 10.1562/2006-08-01-ra-993] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Rhodamine 101 (R101) was chemically attached onto microcrystalline cellulose and methylene blue (MB) was adsorbed to a sample bearing nearby 6 x 10(-7) mol R101 (g cellulose)(-1). The system was studied by reflectance and emission spectroscopy in the solid state. R101 shows no aggregation in these conditions and, while pure MB builds up dimers on cellulose even at 2 x 10(-8) mol g(-1), in the presence of R101 no evidence on selfaggregation or heteroaggregation is found up to around 10(-6) mol g(-1). No exciplex formation is found as well. The overall fluorescence quantum yield measured on thick layers, once re-absorption effects are accounted for, amounts to 0.80 +/- 0.07 for pure R101 and decreases steadily on increasing the concentration of MB. Results demonstrate the occurrence of radiative and nonradiative singlet energy transfer from R101 to MB. For thick layers of particles, the combined effect of both kinds of energy transfer amounts to nearly 80% at the highest acceptor concentration, while nonradiative transfer reaches 60% both for thin and optically thick layers. The dependence of nonradiative energy transfer efficiencies on the acceptor concentration is analyzed and the origin of departures from Förster behavior at low acceptor concentration is discussed.
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Affiliation(s)
- Hernán B Rodríguez
- INQUIMAE/DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina
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Abstract
Absorption and fluorescence properties of methylene blue (MB), a well-known singlet molecular oxygen photosensitizer, and its mixtures with pheophorbide-a (Pheo) sorbed on microgranular cellulose are studied, with emphasis on radiative and nonradiative energy transfer from Pheo to MB. Although pure MB builds up dimeric species on cellulose even at 2 x 10(-8) mol g(-1), addition of 2.05 x 10(-7) mol g(-1) Pheo largely inhibits aggregation up to nearly 10(-6) mol g(-1) MB. At the same time, the absorption spectrum of monomeric MB in the presence of Pheo differs from the spectrum in pure cellulose. Both effects reveal a strong influence of Pheo on the medium properties. A model relying entirely on experimental data is developed, through which energy transfer efficiencies can be calculated for thin and thick layers of dye-loaded cellulose. At the largest concentration of MB assuring no dye aggregation, nonradiative energy transfer efficiencies reach a maximum value of nearly 40%. This value is quite high, taking into account the low fluorescence quantum yield of Pheo, Phi = 0.21, and results from the existence of high local concentrations of the acceptor within the supporting material. These results show that large energy transfer rates can exist in a system devoid of any special molecular organization.
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Affiliation(s)
- Hernán B Rodríguez
- INQUIMAE/DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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Abstract
Rose Bengal adsorbed on microgranular cellulose was studied in the solid phase by total and diffuse reflectance and steady-state emission spectroscopy. A simple monomer-dimer equilibrium fitted reflectance data up to dye loadings of 4 x 10(-7) mol (g cellulose)(-1) and allowed calculation of monomer and dimer spectra. Further increase of dye loading resulted in the formation of higher aggregates. Observed emission and excitation spectra and quantum yields were corrected for reabsorption and reemission of luminescence, using a previously developed model, within the assumption that only monomers are luminescent [M. G. Lagorio, L. E. Dicelio, M. I. Litter and E. San Roman, J. Chem. Soc., Faraday Trans., 1998, 94, 419]. An apparent increase of fluorescence quantum yield with dye loading was found, which was attributed to the occurrence of dimer fluorescence. Extension of the model to two luminescent species (i.e. monomer and dimer) yielded constant fluorescence quantum yields for the monomer, phiM= 0.120 +/- 0.004, and for the dimer, phiD= 0.070 +/- 0.006. The monomer quantum yield is close to the value found for the same dye in basic ethanol. The presence of fluorescent dimers and calculated quantum yields are supported by analysis of the excitation spectra and other experimental evidence. The possible occurrence of non-radiative energy transfer and the effect of surface charge on the properties of the dimer are analyzed.
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Affiliation(s)
- Hernán B Rodríguez
- INQUIMAE/DQIAyQF, FCEyN, UBA, Ciudad Universitaria, Pabellon II, 1428 Buenos Aires, Argentina
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Morales de León JC, Rodríguez HB, González JP. [Adaptation of a cheese-making procedure for use in rural homes]. Arch Latinoam Nutr 1980; 30:369-83. [PMID: 7224777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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