Fluorescence of pyranine in sol-gel based silica and hybrid thin films

Abstract

Abstract. The sensitivity of the pyranine fluorescence to protonation/deprotonation is used to follow modifications in cured sol-gel thin films. The acid concentration in the sol-gel solution is varied for TEOS-based coatings and a series of organically modified silanes Si(OR)3R' are added to the TEOS solution. The concentration of the organically modified silane is varied as well as the chain length of the alkylgroup (R').The stationary fluorescence measurements show that the equilibrium between the protonated and the deprotonated form of pyranine changes depending on the type of silica matrix. The deprotonated form is dominant in the cured SiO2 films and the protonation/deprotonation ratio of pyranine is constant for the different acid concentrations used. The protonated form becomes dominant as the concentration of Si(OR)3R' is increased and as the alkyl chain length (W) of the organically modified silanes is augmented.Emission anisotropy measurements of pyranine in the same coatings show that the rotational freedom of the molecule changes due to modifications in the cages for the TEOS-based coatings. These modifications are produced by the acid concentration used to prepare the coatings. An increase in the rotational freedom of pyranine is observed in the TEOS-Si(OR)3R' systems.

Characterization of the Microenvironments of PRODAN Entrapped in Tetraethyl Orthosilicate Derived Glasses

“…In the past few years several reports have appeared describing the use of fluorescence spectroscopy to characterize the internal environment(s) of sol−gel derived glasses and biomaterials prepared from tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS). , Steady-state and time-resolved fluorescence spectroscopy have been able to provide detailed information regarding the polarity , dynamics, and accessibility of the local microenvironment within the glass, and how these change as a function of the preparation and aging protocols used.…”

“…It is well-known that only some entrapped probes accurately report on the pore−liquid composition and microviscosity within sol−gel derived materials, while others report on other, probe-specific phenomena. For example, some probes, such as 7-azaindole, adsorb to the surface of the glass, providing information on composition of the silica surface rather than the pore−liquid composition. 3a,3b,, Others, such as pyrene, report on the solubility of the probe, owing to shifts in the monomer−excimer equilibria when the probe is present at sufficiently high concentration. 3c,, Other probes can be sensitive to internal pH, oxygen content, or even surface charge . Given the vast number of parameters that may affect the emission of a fluorophore, detailed knowledge of the factors that determine the overall decay properties of a probe is of paramount importance for understanding the relationship between the emission properties of an entrapped probe and the properties of the host material.…”

“…A fluorophore that has been used widely for examination of sol−gel derived materials is 6-propionyl-2-(dimethylamino)naphthalene (PRODAN). 3b,4e,, This probe is typically used to assess the polarity and microviscosity within sol−gel derived materials owing to its large solvatochromic shift (emission wavelength ranges from 401 nm in cyclohexane to 531 nm in water), and the sensitivity of the excited-state decay kinetics to the local environment of the probe . An interesting feature that has recently been reported for this probe is a concentration-dependent aggregation phenomena that is related to solvent composition, producing a diagnostic peak at ca.…”

The pyranine-benzalkonium ion pair: A promising fluorescent system for the ratiometric detection of wound pH

“…In the present work, we turned our attention to HPTS: it is a hydrophilic, pH-sensitive fluorescent dye with very good photostability (a property shared also by its derivatives) [12] and a broad range of applications for optical sensors [13][14][15][16][17][18][19][20]. HPTS has also been used for various biological applications, e.g.…”

Solvatochromic Characterization of Organic−Inorganic Polymer Hybrids with Pyridinium N-Phenolate Betaine Dyes

“…It is of great interest to utilize these nanocomposites as host media for numerous organic, organometallic, and biological molecules. − This approach has been applied extensively for the design and synthesis of a wide range of novel materials in the fields of photonics (solid-state dye lasers, − nonlinear optics, − optical storage, optical switches), sensors, , and biological catalysts . Probing the microenvironment of the entrapped molecules in the nanocomposites is another area of interest. ,− The nature of the local environment around the entrapped molecule is usually decisive in achieving the desired property. It is necessary to understand the microenvironment around the doped molecules to predict and design the property of the molecules and the resulting property of the materials.…”