New Polyhedral Oligomeric Silsesquioxanes-Based Fluorescent Ionic Liquids: Synthesis, Self-Assembly and Application in Sensors for Detecting Nitroaromatic Explosives.

Wensi Li,Dongdong Han,Jie Zhang,Shengyu Feng,Dengxu Wang,Ruixue Sun

doi:10.3390/polym10080917

Abstract

In this paper, two different models of hybrid ionic liquids (ILs) based on polyhedral oligomeric silsesquioxanes (POSSs) have been prepared. Additionally, these ILs based on POSSs (ILs-POSSs) exhibited excellent thermal stabilities and low glass transition temperatures. 1H, 13C, and 29Si nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to confirm the structures of the IL-POSSs. Furthermore, the spherical vesicle structures of two IL-POSSs were observed and were caused by self-assembly behaviors. In addition, we found it very meaningful that these two ILs showed lower detection limits of 2.57 × 10−6 and 3.98 × 10−6 mol/L for detecting picric acid (PA). Moreover, the experimental data revealed that the products have high sensitivity for detecting a series of nitroaromatic compounds—including 4-nitrophenol, 2,4-dinitrophenol, and PA—and relatively comprehensive explosive detection in all of the tests of IL-POSSs with nitroaromatic compounds thus far. Additionally, the data indicate that these two new ILs have great potential for the detection of explosives. Therefore, our work may provide new materials including ILs as fluorescent sensors in detecting nitroaromatic explosives.

Highlights

Ionic liquids (ILs), which have been recognized as a novel class of synthetic materials, have melting points below 100 ◦ C [1,2,3]
We explored ionic liquids (ILs)-polyhedral oligomeric silsesquioxanes (POSSs) materials synthesized with more imidazolium rings in order to enhance their fluorescence sensitivities and employed these IL-POSS materials for detecting a series of nitroaromatic compounds, including 4-nitrophenol, 2,4-dinitrophenol and picric acid (PA)
Based on the aforementioned excellent fluorescence of IL-POSSs, we explored their application in the detection of 4-nitrophenol (NP), 2,4-dinitrophenol (DNP) and picric acid (PA) in ethanol [39]

Summary

Introduction

Ionic liquids (ILs), which have been recognized as a novel class of synthetic materials, have melting points below 100 ◦ C [1,2,3]. With increasing demand for advanced materials, the development of novel ILs has been increasingly explored due to their unique properties [4], which include high ionic conductivity [5], high thermal stability, non-flammability, negligible vapor pressure, and a wide electrochemical stability window [6,7]. POSSs exhibit marvellous compatibility [10] with organic materials because of their inorganic core with various functional organic substituents [7,11,12]. Due to their many excellent merits, POSS materials have been extensively used in many fields, including as drug delivery agents [13], liquid crystalline materials [14,15], and light-emitting materials [16]. Given the aforementioned advantages of POSSs, introducing them into ILs is a reasonable approach to creating more novel and functional ILs

Methods

Discussion

Conclusion