Fully inkjet-printed paper-based Pb2+ optodes for water analysis without interference from the chloramine disinfectant

Near-Infrared Fluoride Sensing Nano-Optodes and Distance-Based Hydrogels Containing Aluminum-Phthalocyanine

“…In this regard, optical sensors could be advantageous since they are miniaturizable and immune to electromagnetic interference and thus more easily adapted for various onsite and point-of-care testing (POCT) purposes. − For example, ionophore-based optodes, the counterpart of ISEs, have recently been miniaturized into the nanoscale, resulting in “ion-selective nano-optodes” targeting various ions including Li + , Na + , K + , Ca 2+ , Pb 2+ , Cu 2+ , Cl – , and polyions. − For POCT, ion-selective nano-optodes have been physically entrapped in agarose hydrogels to form distance-based disposable optical ion sensing devices, which could reduce the reliance on heavy instrumentation and the cost of measurements. , The 3D networks of agarose hydrogels also act as filters to block large particulates (such as cells in blood) while allowing inorganic ions to readily reach the entrapped nano-optodes. , Ion-selective nano-optodes typically contained the following sensing components: an ionophore to bind the target ion, an ion-exchanger (optional in certain cases), and a chromoionophore for optical signal transduction, and a lipophilic matrix to host the active ingredients. , In this way, recognition of the target ions could eventually lead to optical signal changes from the chromoionophore, which could be pH-sensitive or solvatochromic dyes. ,− However, since there is a limited number of highly selective fluoride ionophores, fluoride-selective nano-optodes were rarely reported despite the great significance of fluoride in environmental and biological sciences.…”