I.S. Cole, A. Trinchi, S.G. Hardin
pp. 510 - 513
Keywords: quantum dots, permeable membranes, pH sensing
The development of inexpensive, flexible, robust pH sensors with an optical mode of operation remains a key challenge. Monitoring pH is a critical capability, and in most lab applications is carried out using the electrochemical glass electrode, which has limitations that make it ill-suited for many applications (e.g. in-vivo biomedical, clinical or food monitoring, or where there may be size limitations or need for deformability). Recently fluorescent semiconductor quantum dots (QDs), which exhibit strong, narrow band fluorescence emission, have been shown to be applicable to a variety of sensing applications. Here we report the development of flexible, water permeable, chromogenic membranes loaded with dyes whose optical properties have been tailored to those of the QD. These systems can be used for reversibly sensing pH changes by monitoring the QD’s fluorescence emission. The membranes can be cast onto a variety of substrates. Under defined conditions, the dye in absorbing mode is chosen to either block the incoming light that stimulates the QD fluorescence, or to absorb the QD’s outgoing fluorescence. By incorporating multiple dye/QD couples, it is theoretically possible to obtain multi-frequency signals over a wide range of pH’s.