The preparation of stimulus-responsive Pickering emulsion and its application in preparing microspheres

Abstract

In this paper, we report a novel redox responsive water-in-oil Pickering emulsion stabilized by negatively charged SiO₂ nanoparticles hydrophobized with a trace amount of cationic surfactant 3-pyridyl-5-ferrocenyl-2-pyrazoline (PFP), in which ferrocene serves as a redox-sensitive group. The stability of Pickering emulsion can be modulated by adding oxidant and reducing agent alternatively, which leads to the change of amphiphilicity of SiO₂ nanoparticles because of the adsorption of PF⁺P and desorption of PFP. This destabilization-stabilization behavior can be cycled at least three times, demonstrating that the Pickering emulsion is switchable. At the same time, polyacrylamide@SiO₂-PF⁺P microspheres are prepared using Pickering emulsion as template, which can be used for the detection of Fe³⁺. Interestingly, when extremely small amounts of microspheres are placed in Fe³⁺ solution and left overnight, the limit of detection (LOD) decreases significantly because of the synergistic effect of enrichment and fluorescent probe for polyacrylamide and PF⁺P respectively. Moreover, the fluorescence intensity increased when EDTA was added to the solution containing microspheres and Fe³⁺, and a decrease of fluorescence intensity was observed when Fe³⁺ was added again, indicating that the composite microspheres could be reused. This work provides a promising way to construct novel fluorescent probes.

Graphical Abstract

Keywords:

• Pickering emulsion
• modified nanoparticles
• redox
• microspheres
• fluorescent probe

Acknowledgment

We are thankful for the financial support from National Natural Science Foundation Young Investigator Grant Program (Project No. 21706148), Natural Science Foundation of Shandong (Project No. ZR2019MEM010, ZR202103010303), Innovation Research Fund Project of Zhaoyuan Institute of Industrial Technology (Project No. 219185, 220191), and Hubei Jingmen Science and Technology Planning Project (Project No. 2021YFZD030).

Additional information

Funding

This work was funded by National Natural Science Foundation of China;National Natural Science Foundation of China-Shandong Joint Fund;Urgent Need of Talents for Key Supporting Regions of Shandong Province.