Photophysics of Xanthene Dyes at High Concentrations in Solid Environments: Charge Transfer Assisted Triplet Formation

Litman, Yair; Rodríguez, Hernán B.; Braslavsky, Silvia E.; Román, Enrique

doi:10.1111/php.12978

Cited by 8 publications

(8 citation statements)

References 53 publications

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“…shows the fluorescence spectrum of the PhG-SiO2, after being modified with aminofluorescein according to Scheme 3, with a maximum emission at 517 nm. Similar spectra have been obtained for the other fluorescent derivatives from the carboxylic NPs; small differences in peak emission (5 nm) respect to the free dye can be attributed to the change of photophysical parameters and have been observed in surface immobilized dyes (Figure ESI 5(a)) [48,49]. When the coupling reagents EDC and NHS are not present there is no fluorescence signal, pointing that the immobilization of fluorescein does not take place and we can rule out adsorption of the dye on the SiO2 surface.…”

supporting

confidence: 70%

Click-based thiol-ene photografting of COOH groups to SiO2 nanoparticles: Strategies comparison

Penelas

Soler-Illia

Levi

et al. 2019

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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We present the study of the anchoring of carboxylic groups on SiO2 nanoparticles from different approximations based on the photochemical radical thiol-ene addition (PRTEA) reaction: a photografting approach between mercaptosuccinic acid (MSA) and vinyl-modified SiO2 nanoparticles and the post-grafting on the surface of silica colloids of the silane precursor 2-((2-(trimethoxysilyl)ethyl)thio)succinic acid (TMSMSA), obtained from the PRTEA. These synthetic strategies were compared with a widely common derivatization methodology based on the nucleophilic attack of surface-anchored amino groups with succinic anhydride. The successful functionalization of the colloidal silica was confirmed by infrared spectroscopy (FTIR), zeta potential at different pH and contact angle measurements. We found that although these three approaches were valid for -COOH immobilization, they had a noticeable impact on the dispersability and agglomeration of the colloidal suspension at the end of the synthesis. Scanning electron microscopy, dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS) measurements indicated that the PRTEA photografting between MSA and vinyl-modified SiO2 resulted in highly dispersed colloidal particles. On the other hand, the presence of surface -COOH groups was highly beneficial for redispersion of the colloidal material after lyophilization or freeze-drying procedures.

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supporting

confidence: 70%

Click-based thiol-ene photografting of COOH groups to SiO2 nanoparticles: Strategies comparison

Penelas

Soler-Illia

Levi

et al. 2019

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…However, the lowest fluorescence of M1 could only be due to fluorescence quenching. A high amount of absorbed dye probably caused the formation of specific species, such as molecular aggregates, able to quench fluorescence [31]. M1 and M3 exhibited the shift of the emission peak to a higher wavelength (598 nm), indicating photophysical interactions between PhB molecules.…”

Section: Selection Of Optimal Polyurethane Composite Membranesmentioning

confidence: 99%

Surface Characterization and Anti-Biofilm Effectiveness of Hybrid Films of Polyurethane Functionalized with Saponite and Phloxine B

et al. 2021

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The main objective of this work was to synthesize composites of polyurethane (PU) with organoclays (OC) exhibiting antimicrobial properties. Layered silicate (saponite) was modified with octadecyltrimethylammonium cations (ODTMA) and functionalized with phloxine B (PhB) and used as a filler in the composites. A unique property of composite materials is the increased concentration of modifier particles on the surface of the composite membranes. Materials of different compositions were tested and investigated using physico-chemical methods, such as infrared spectroscopy, X-ray diffraction, contact angle measurements, absorption, and fluorescence spectroscopy in the visible region. The composition of an optimal material was as follows: nODTMA/mSap = 0.8 mmol g−1 and nPhB/mSap = 0.1 mmol g−1. Only about 1.5% of present PhB was released in a cultivation medium for bacteria within 24 h, which proved good stability of the composite. Anti-biofilm properties of the composite membranes were proven in experiments with resistant Staphylococcus aureus. The composites without PhB reduced the biofilm growth 100-fold compared to the control sample (non-modified PU). The composite containing PhB in combination with the photodynamic inactivation (PDI) reduced cell growth by about 10,000-fold, thus proving the significant photosensitizing effect of the membranes. Cell damage was confirmed by scanning electron microscopy. A new method of the synthesis of composite materials presented in this work opens up new possibilities for targeted modification of polymers by focusing on their surfaces. Such composite materials retain the properties of the unmodified polymer inside the matrix and only the surface of the material is changed. Although these unique materials presented in this work are based on PU, the method of surface modification can also be applied to other polymers. Such modified polymers could be useful for various applications in which special surface properties are required, for example, for materials used in medical practice.

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“…Recently, the comparison between corrected fluorescence and triplet quantum yields for different xanthene dyes in microcrystalline cellulose evidenced the formation of photoactive traps capable of yielding triplet states by a charge-transfer assisted mechanism. 20…”

Section: Light-scattering Solid Particlesmentioning

confidence: 99%

“…Corrections of observed triplet quantum yields for fluorescence reabsorption can be performed for light-scattering samples by using the mKM model (SI, eq 5). Recently, the comparison between corrected fluorescence and triplet quantum yields for different xanthene dyes in microcrystalline cellulose evidenced the formation of photoactive traps capable of yielding triplet states by a charge-transfer assisted mechanism …”

Section: Photoprocesses In Highly Absorbing Systemsmentioning

confidence: 99%

Photophysics at Unusually High Dye Concentrations

et al. 2018

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Conspectus 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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Photophysics of Xanthene Dyes at High Concentrations in Solid Environments: Charge Transfer Assisted Triplet Formation

Cited by 8 publications

References 53 publications

Click-based thiol-ene photografting of COOH groups to SiO2 nanoparticles: Strategies comparison

Click-based thiol-ene photografting of COOH groups to SiO2 nanoparticles: Strategies comparison

Surface Characterization and Anti-Biofilm Effectiveness of Hybrid Films of Polyurethane Functionalized with Saponite and Phloxine B

Photophysics at Unusually High Dye Concentrations

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