In-Situ pH-Sensitive Fibers via the Anchoring of Bromothymol Blue on Cellulose Grafted with Hydroxypropyltriethylamine Groups via Adsorption.

Lele Cao,Xipeng Zhang,Jian Li,Wenbo Liu,Lijuan Wang,Xianxu Zhan,Tieqiang Liang

doi:10.3390/polym10070709

Lele Cao, Xipeng Zhang + Show 5 more

Open Access

https://doi.org/10.3390/polym10070709

Copy DOI

Abstract

In-situ pH-sensitive cellulose fibers (IS-pH-SCF) were prepared by anchoring bromothymol blue (BTB) onto cellulose fibers (CF) modified with hydroxypropyltriethylamine (HPTTL) groups. Fourier transform infrared and X-ray photoelectron spectrum analyses demonstrated that the HPTTL groups were grafted onto the CF. X-ray diffraction proved that cellulose I in the CF transformed into cellulose II after quaternization. Scanning electron microscopy suggested that the quaternized CF (QCF) surface was clean and uniformly ridged. The adsorption of BTB onto QCF was carried out via batch adsorption experiments. A kinetic study illustrated that the adsorption was a spontaneous process and described well by pseudo-second-order, Freundlich and Temkin isotherms. The activation energy for the BTB adsorption onto QCF was 52.89 kJ/mol, which proved that the BTB adsorption onto QCFs was chemically controlled. The pH response demonstrated that the IS-pH-SCF was highly sensitive to pH, with an obvious color change for pH 4 to 8. The release tests showed that BTB was anchored on QCFs and that no BTB was released. IS-pH-SCF has a potential use for indicating pH changes in food.

Highlights

Foods are rich in nutrients and are the most basic materials for human survival
The traditional food quality test is based on a chemical analysis, which requires the destruction of foods, expensive analytical instruments, professional operators, and extended times [1]
A pH dye-based indicator, prepared by coating a mixed solution of bromothymol blue and methyl red on a film that was prepared with nylon with linear low-density polyethylene, was applied to monitor a golden drop, and proved that it can serve as a real-time indicator for spoilage via color changes [15]

Summary

Introduction

Foods are rich in nutrients and are the most basic materials for human survival. Food safety is directly related to human physical health and life safety, and is critical to ensure both economic and social stability. The traditional food quality test is based on a chemical analysis, which requires the destruction of foods, expensive analytical instruments, professional operators, and extended times [1]. Such analyses are not always feasible because the detection is not readily accessible by the public. To overcome these disadvantages, intelligent packaging materials and indicators have been favored by scholars for the real-time detection of food quality [2]. Protein-rich foods (fish and pork, for example) release organic amines during the spoilage, which results in an increase in pH [3].

Methods

Results

Conclusion