Efficient colorimetric pH sensor based on responsive polymer-quantum dot integrated graphene oxide

Based on the responsive polymer and quantum dot (QD) hybrids integrated on a single GO sheet, a GO-based optical sensor was developed to provide colorimetric responses from a wide pH range, as well as excellent stability.

Article  |  Fall 2014

Highly-selective and sensitive optical detection methods have attracted increasing interest in the investigation of environmental, biomedical, and analytical chemistry applications. Graphene oxide (GO) can provide an excellent sensing platform as a highly-sensitive fluorescence quencher. In addition to this superior property, GO also has good dispersion behavior in water and long-term stability. However, none of the reported GO-based optical sensors show a colorimetric response, which means that they always require an additional specific and expensive detector to monitor external changes.

Prof. Bumjoon Kim’s lab designed a robust and versatile platform for a highly-stable GO-based optical sensor that has colorimetric and ratiometric behavior. As an example, they demonstrated the fabrication of a GO-based pH sensor capable of responding to a wide range of pH values with color response.

Prof. Bumjoon Kim’s lab developed the following strategies for producing a highly-stable GO-based pH sensor: 1) the use of two different blue- and orange-colored QDs anchored to a single GO sheet; 2) the pH-dependent emissions of the blue and orange QDs by using the linkers of two different pH-responsive polymers, poly(acrylic acid) and poly(2-vinyl pyridine); and 3) the color of GO-based pH sensor changes from orange to white to blue ratiometrically over a wide range of pH values (pH1 ~ pH7). Furthermore, the research team showed that GO-based pH sensors exhibit high dispersion stability in aqueous media, and reversibility, thereby satisfying the critical requirements for sensors.

Reference: Kwanyeol Paek, Hyunseung Yang, Junhyuk Lee, Junwoo Park, and Bumjoon J. Kim* “Efficient Colorimetric pH Sensor Based on Responsive Polymer–Quantum Dot Integrated Graphene Oxide” ACS Nano, 2014, 8 (3), pp 2848–2856

Additional links for more information:
http://pubs.acs.org/doi/abs/10.1021/nn406657b
http://pnel.kaist.ac.kr