Kinetic and spectroscopic responses of pH-sensitive nanoparticles: influence of the silica matrix

Clasen, Anne; Wenderoth, Sarah; Tavernaro, Isabella; Fleddermann, Jana; Kraegeloh, Annette; Jung, Gregor

doi:10.1039/c9ra06047b

Cited by 7 publications

(9 citation statements)

References 80 publications

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“…In this context, Finlayson et al demonstrated that, above the T g , the poly(ethylacrylate) (PEA) shell shows viscoelastic properties with a corresponding shear rate of η = 10 3 –10 4 Pa·s at 100 °C, which is important for the ordering process [ 37 ]. Moreover, protic polar environments turned out to enhance ESPT [ 29 , 30 ]; therefore, it is necessary to include hydroxylic moieties into the shell material. Furthermore, it can be assumed that, the higher the content of the hydroxylic groups in the copolymer, the higher the corresponding hydrophilicity.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, the excitation spectrum exclusively shows a band at 447 nm, which is assigned to ROH. Although the extent of emission of the conjugated base of the photoacid is minor, its observation unambiguously points to ESPT [ 30 ]. Summarizing, PHEMA- and PIPGMA-containing opal films spectra show evidence for ESPT, which was confirmed for a PGMMA-containing film by adding water (pH 3.5) as proton acceptor.…”

Section: Resultsmentioning

confidence: 99%

“…The reversible proton release (in the excited state) and recapture (in the ground state) is also known as the Förster Cycle [ 27 ]. However, solvatochromism and recent spectroscopic experiments highlighted the decisive impact of the surrounding in ESPT [ 28 , 29 , 30 , 31 , 32 , 33 ]. In the present case, two possible effects of the matrix as surrounding aroused our interest: (1) Can we exploit the reversible generation of charged molecules to manipulate the material photonic properties?…”

Section: Introductionmentioning

confidence: 99%

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Embedding Photoacids into Polymer Opal Structures: Synergistic Effects on Optical and Stimuli-Responsive Features

et al. 2021

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Opal films with their vivid structural colors represent a field of tremendous interest and obtained materials offer the possibility for many applications, such as optical sensors or anti-counterfeiting materials. A convenient method for the generation of opal structures relies on the tailored design of core-interlayer-shell (CIS) particles. Within the present study, elastomeric opal films were combined with stimuli-responsive photoacids to further influence the optical properties of structurally colored materials. Starting from cross-linked polystyrene (PS) core particles featuring a hydroxy-rich and polar soft shell, opal films were prepared by application of the melt-shear organization technique. The photoacid tris(2,2,2-trifluoroethyl) 8-hydroxypyrene-1,3,6-trisulfonate (TFEHTS) could be conveniently incorporated during freeze-drying the particle dispersion and prior to the melt-shear organization. Furthermore, the polar opal matrix featuring hydroxylic moieties enabled excited-state proton transfer (ESPT), which is proved by spectroscopic evaluation. Finally, the influence of the photoacid on the optical properties of the 3-dimensional colloidal crystals were investigated within different experimental conditions. The angle dependence of the emission spectra unambiguously shows the selective suppression of the photoacid’s fluorescence in its deprotonated state.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Embedding Photoacids into Polymer Opal Structures: Synergistic Effects on Optical and Stimuli-Responsive Features

et al. 2021

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“…4). The change of the solvent should effect the spectra of the dyes on the surface, while particles with dyes in the interior should show no or only a minor solvent influence [47].…”

Section: Validation Of Binding Character and Dye Distribution In The Particlementioning

confidence: 99%

“…In addition to the position of the dye in the particle, the covalent or non-covalent nature of the dye-particle connection should be proven, as well as the strength of the dye-particle interaction. Due to low dye concentrations, statements about the strength of the dye binding are only possible with spectroscopic methods such as fluorescence anisotropy [47]. In this method, fluorophores get excited by polarized light.…”

Section: Validation Of Binding Character and Dye Distribution In The Particlementioning

confidence: 99%

Hybrid inorganic-organic fluorescent silica nanoparticles—influence of dye binding modes on dye leaching

Klippel

Jung

Kickelbick

2021

J Sol-Gel Sci Technol

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Silica nanoparticles with embedded fluorescent dyes represent an important class of markers for example in biological imaging. We systematically studied the various incorporation mechanisms of fluorescent xanthene dyes in 30–40 nm silica nanoparticles. An important parameter was the interaction of the dye with the matrix material, either by weak electrostatic or strong covalent interactions, which also has implications on the stability of fluorescence and brightness of the dyes. Factors that can influence leaching of dyes such as the position of the dyes in particles and the intensity of the particle-dye interaction were investigated by using the solvatochromic effect of xanthene dyes and by stationary fluorescence anisotropy measurements. We compared uranine and rhodamine B, which were physically embedded, with modified fluorescein isothiocyanate and rhodamine B isothiocyanate, which were covalently bound to the silica matrix within a usual Stöber synthesis. Systematic leaching studies of time spans up to 4 days revealed that covalent bonding of dyes like fluorescein isothiocyanate or rhodamine B isothiocyanate is necessary for fluorescence stability, since dyes bound by physical interaction tend to leach out of porous silica networks. Coverage of silica particles with hydrophobic protection layers of alkyltrialkoxysilanes or hydrophilic polyethylene glycol (PEG) groups resulted in a better retention of physisorbed dyes and provides the possibility to adapt the particles to the polarity of the medium. Best results were archived with PEG groups, but even small trimethylsilyl (TMS) groups already reduce leaching.

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Ultrafast transient absorption and solvation of a super-photoacid in acetoneous environments

Knorr

Sülzner

Geissler

et al. 2022

Photochem Photobiol Sci

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The phenomenon of photoacidity, i.e., an increase in acidity by several orders of magnitude upon electronic excitation, is frequently encountered in aromatic alcohols capable of transferring a proton to a suitable acceptor. A promising new class of neutral super-photoacids based on pyranine derivatives has been shown to exhibit pronounced solvatochromic effects. To disclose the underlying mechanisms contributing to excited-state proton transfer (ESPT) and the temporal characteristics of solvation and ESPT, we scrutinize the associated ultrafast dynamics of the strongest photoacid of this class, namely tris(1,1,1,3,3,3-hexafluoropropan-2-yl)8-hydroxypyrene-1,3,6-trisulfonate, in acetoneous environment, thereby finding experimental evidence for ESPT even under these adverse conditions for proton transfer. Juxtaposing results from time-correlated single-photon counting and femtosecond transient absorption measurements combined with a complete decomposition of all signal components, i.e., absorption of ground and excited states as well as stimulated emission, we disclose dynamics of solvation, rotational diffusion, and radiative relaxation processes in acetone and identify the relevant steps of ESPT along with the associated time scales. Graphical abstract

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Kinetic and spectroscopic responses of pH-sensitive nanoparticles: influence of the silica matrix

Abstract: Self-calibrating, fluorescent nanoparticles with diameter far below 50 nm are synthesized with embedding a new ratiometric and pH sensitive indicator dye. The prompt response of the fluorophore allows for determining the intracellular pH.

Cited by 7 publications

References 80 publications

Embedding Photoacids into Polymer Opal Structures: Synergistic Effects on Optical and Stimuli-Responsive Features

Embedding Photoacids into Polymer Opal Structures: Synergistic Effects on Optical and Stimuli-Responsive Features

Hybrid inorganic-organic fluorescent silica nanoparticles—influence of dye binding modes on dye leaching

Ultrafast transient absorption and solvation of a super-photoacid in acetoneous environments

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