An Optical pH Sensor Based on Diazocine

Abstract

A novel excellent candidate for the optical pH sensor based on diazocine is presented in this paper. Diazocine serves as a cyclooctatetraene analogy which has a nonplanar 8‐membered ring structure with nitrogen atoms. It is the first example to present the optical properties of cyclooctatetraene analogy with chemical (trifluoroacetic acid) pH gradient by UV‐visible absorption and NMR spectra. Specifically, reversibility of protonation/deprotonation reaction is clearly demonstrated by the UV spectra when triethylamine is added. In this work, we also investigate the spectral properties and sensitivity of polydiaryldibenzo[1, 5]diazocines (PBDA) retaining its optical properties in liquid state. This study features an innovative detection system for H+ measurement through a low cost optical device by means of polymer spin‐coating on the support material (PE films). Furthermore, the optical characteristic collected in the solid state is in excellent agreement with the data previously found in the liquid state. The transient response of optical device is very rapid upon pH change from 6.9 to 1.5. As a result, optical device based on PBDA can be applied to test H+ or pH in organic or aqueous solvent and even extended to sensing of some other analytes.

Synthetic strategies and diversification of dibenzo[1,5]diazocines

“…14,15 The extensive extended π-conjugation of dibenzo [1,5]diazocines are widely employed as organic candidates for organic light emitting diodes (OLEDs) 16,17 and optical sensors. 18 The electron-rich diazocine structures are also capable of serving as versatile ligands towards metal ions to generate a wide range of fascinating geometric architectures of metal complexes. [19][20][21][22][23] From a structural viewpoint, the symmetric structure of diazocine has eight π-electrons, adopts the boat conformation and is classified as a Hückel anti-aromatic compound.…”

“…14,15 The extensive extended π-conjugation of dibenzo[1,5]diazocines are widely employed as organic candidates for organic light emitting diodes (OLEDs) 16,17 and optical sensors. 18 The electron-rich diazocine structures are also capable of serving as versatile ligands towards metal ions to generate a wide range of fascinating geometric architectures of metal complexes. 19–23…”

Development and Characterization of Integrated Nano-Sensors for Organic Residues and pH Field Detection

“…Of these CPs, polyaniline (PANI) is the most frequent choice, given its ease of synthesis, low cost, good environmental stability, and ability to reverse its electric properties (doping) from an insulator to a metallic conductor through a protonation/deprotonation mechanism [ 28 ]. In an acidic medium, PANI is conductive in its protonated form, while, in a basic medium, PANI becomes an insulator (in its deprotonated form) [ 29 , 30 ]. One way to prepare PANI is by inverted emulsion polymerization [ 31 , 32 , 33 ], which has the advantage of overcoming the thermal and viscosity issues that can arise during the reaction, while maintaining its robust chemical properties [ 34 ].…”