Photoresponsive Ion-Selective Optical Sensor

Light-driven ion extraction of polymeric membranes for on-demand Cu(II) sensing

The modulation of the ion-fluxes across a polymeric membrane is important for designing attractive methodologies. As an alternative to the commonly used dynamic electrochemistry approaches, light can be used as an external stimulus and provides a very convenient way to manipulate ions release and/or extraction into a polymeric membrane. Herein, we designed a solid-contact polymeric membrane ion-selective sensor that exhibits dynamic response by light irradiation at 375 nm. The electrode membrane contains a light-sensitive lipophilic salt (bis(4-tert-butylphenyl)iodonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (R⁺-R^-, BTDT-TFPB) instead of traditional ion exchanger. Under light illumination, the decomposition of the lipophilic cation makes the membrane with ion-exchange properties. The solid-contact ion-selective electrodes based on potentiometry and constant potential coulometry have been explored for direct ion sensing. Copper was selected as a mode analyte and can be determined at micromole levels. The proposed dynamic ion sensors show promise for on-demand ion sensing.

Visible light-induced ion-selective optodes based on a metastable photoacid for cation detection

A new platform of ion-selective optodes is presented here to detect cations under thermodynamic equilibriumviaratiometric analysis.

Photodynamic optical sensor for buffer capacity and pH based on hydrogel-incorporated spiropyran

The kinetics of a light activated proton extraction correlates with the buffer capacity of a sample at a given pH.

Photoresponsive ion extraction/release systems: dynamic ion optodes for calcium and sodium based on photochromic spiropyran

Photoresponsive ion extraction/release systems (PRIONERS) represent a highly interesting tool for the localized and time-controlled chemical perturbation of biological materials. We report here on our first results on phototriggered calcium and sodium exchanging materials. Such materials exist in two distinct states (“on” and “off”), depending on the wavelength of illumination. We used a combination of spectroscopic and electrochemical methods to obtain a better understanding of the dynamic processes involved in the triggered ion-exchange reaction upon activation of the photoactive compound. The driving force for the ion exchange is the light-induced acidity change of the chromoionophore. Activation with UV light generates a species in the membrane with an increased pK_a. Protons are pulled into the membrane, and at the same time, ions are expelled. The selectivity of the system is determined by the employed ionophore. In contrast to photoresponsive ionophore-based systems, the concept presented here is applicable for virtually any ion of interest for which an ionophore exists.

Reversible photodynamic chloride-selective sensor based on photochromic spiropyran

We report here for the first time on a reversible photodynamic bulk optode sensor based on the photoswitching of a spiropyran derivative (Sp). The photoswitching of Sp induces a large basicity increase in the polymeric phase, which triggers the extraction of Cl^– and H⁺. Cl^– is stabilized by a lipophilic chloride-selective ionophore inside the membrane, while H⁺ binds with the open form of Sp and induces a spectral change, hence providing the sensor signal. The system was studied with spectroscopic and electrochemical methods.