Spherical Silica Functionalized by 2-Naphthalene Methanol Luminophores as a Phosphorescence Sensor.

Magdalena Laskowska,Peter Weigl,Łukasz Laskowski,Anna Nowak,Thomas Blochowicz,Mateusz Dulski

doi:10.3390/ijms222413289

Abstract

Photoluminescence is known to have huge potential for applications in studying biological systems. In that respect, phosphorescent dye molecules open the possibility to study the local slow solvent dynamics close to hard and soft surfaces and interfaces using the triplet state (TSD: triplet state solvation dynamics). However, for that purpose, probe molecules with efficient phosphorescence features are required with a fixed location on the surface. In this article, a potential TSD probe is presented in the form of a nanocomposite: we synthesize spherical silica particles with 2-naphthalene methanol molecules attached to the surface with a predefined surface density. The synthesis procedure is described in detail, and the obtained materials are characterized employing transmission electron microscopy imaging, Raman, and X-ray photoelectron spectroscopy. Finally, TSD experiments are carried out in order to confirm the phosphorescence properties of the obtained materials and the route to develop phosphorescent sensors at silica surfaces based on the presented results is discussed.

Highlights

Since the last decades of the 20th century, organic materials have shown a vast potential for application
The resulting thermodynamic equilibrium consisting of the triplet state solvation dynamics (TSD) probe and the surrounding solvent can be locally disturbed by exciting the phosphorophore into a metastable triplet state by a UV laser pulse via an intersystem crossing
In order to check the purity of the samples and observe the surface of functionalized materials, we carried out Transmission Electron Microscopy (TEM) imaging

Summary

Introduction

Since the last decades of the 20th century, organic materials have shown a vast potential for application. Naphthalene (Nph) and its derivates, as one of the simplest polyaromatic hydrocarbons, consist of two fused benzene rings, and are commonly used as fluorescence markers and are considered as sensors for metal ions Still, their potential for applications is much broader: for example, as a component for dyes, drugs, or surfactants, just to name of few [7]. The resulting thermodynamic equilibrium consisting of the TSD probe and the surrounding solvent can be locally disturbed by exciting the phosphorophore into a metastable triplet state by a UV laser pulse via an intersystem crossing This initiates reorientation dynamics of the solvent molecules in the first solvation shell, i.e., approximately in a single molecular layer of solvent molecules (∼1 nm), resulting in a spectral shift of the phosphorescence emission as a function of time. Depending on the TSD probe used, local dielectric or shear mechanical experiments can be performed; allowing the TSD method to be understood as a local version of dielectric or shear relaxation spectroscopy, respectively [8,9,10]

Methods

Results

Conclusion