Fluorescent, stimuli-responsive, crosslinked PNIPAM-based microgel

•A fluorescent, crosslinked PNIPAM-based microgel is synthesized via simple free radical emulsion polymerization to use as a dual-responsive material.•The microgel shows excellent pH-responsive property with noticeable changes in its fluorescence emission color, caused by fluorophores in the polymer...

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Bibliographic Details
Published in:Sensors and actuators. B, Chemical Chemical, 2015-02, Vol.207, p.623-630
Main Authors: Kim, Yongkyun, Kim, Daigeun, Jang, Geunseok, Kim, Jongho, Lee, Taek Seung
Format: Article
Language:English
Subjects:
Crosslinking
Fluorescein
Fluorescence
Free radicals
Microgels
pH and temperature
PNIPAM microgel
Rhodamine
Sensor
Stimuli-responsive material
Turbidity
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Summary:•A fluorescent, crosslinked PNIPAM-based microgel is synthesized via simple free radical emulsion polymerization to use as a dual-responsive material.•The microgel shows excellent pH-responsive property with noticeable changes in its fluorescence emission color, caused by fluorophores in the polymer backbone, which can be easily observed by the naked eye.•The microgel is capable of monitoring of pH or temperature using fluorometric method.•The microgel is robust and exhibits its reversibility of fluorescence emission colors even after repeated cycles of pH variation mainly because of its crosslinked structure. We have synthesized a highly pH and temperature-sensitive, fluorescent, crosslinked poly(N-isopropylacrylamide) (PNIPAM)-based probe via simple free radical emulsion copolymerization, which formed a reversible microgel containing both fluorophores of fluorescein and rhodamine derivatives. We confirmed that the opening of the lactone ring of fluorescein and the lactam ring of rhodamine in the polymer was responsible for the fluorescence changes in basic and acidic conditions, which showed fluorescence emissions at 514nm (green) and 586nm (red), respectively. The polymeric microgel exhibited a linear relationship between the ratio of emission intensity and pH windows of pH 2–6 and 7–12. Moreover, the microgel exhibited changes in fluorescence intensity with an alteration of turbidity of the microgel induced by temperature. Moreover, these fluorescence changes could be easily observed by the naked eye, serving as a potential probe for ratiometric microgel detection of pH or temperature.
ISSN:0925-4005
1873-3077
DOI:10.1016/j.snb.2014.10.089