Red‐ to NIR‐Emitting, BODIPY‐Based, K⁺‐Selective Fluoroionophores and Sensing Materials

Abstract

Optical sensing materials for the selective measurement of potassium ions (K+) in water are presented. The indicator dyes are based on an aza‐crown ether as a receptor and borondipyrromethenes (BODIPY) dyes as fluorophores. Fluorescence enhancement is caused by the reduction of photoinduced electron transfer (PET) upon complexation with K+ ions. The family of new indicators possesses tuneable optical properties (green to red excitation, red to NIR emission) and PET efficiencies. They exhibit high brightness with quantum yields between 0.20 and 0.47 in the “on” state and a molar absorption coefficient between 30 000 and 290 000 m−1 cm−1. The new indicator dyes are immobilized in biocompatible hydrogel matrices to obtain stable nonleaching and fast responding (t90 ≈ 10 s) sensing materials for continuous measurements of potassium. They are realized in various formats such as planar optodes, fiber‐optic sensors, and water‐dispersible polymer‐based nanoparticles. Apart from fluorescence intensity measurements, self‐referenced read‐out of fluorescence decay time is demonstrated. All sensor materials display a high K+/Na+ selectivity and are not influenced by pH within the physiologically relevant range. Practical applicability of the materials is emphasized by application of a fiber‐optic sensor to quantification of K+ in serum, which shows excellent correlation with the reference measurements.

Sub-nanomolar detection of cesium with water-gated transistor

“…We believe this is due to the channel-like nanocavities in zeolite structures wherein cations absorb more strongly than in the rather point-like 'holes' in ring-shaped organic cation sensitiser molecules, e.g. crown ethers [41]. As a caveat, we note that the observed threshold shift results from the extraction of Cs + by mordenite from the sample, which will reduce Cs + concentration in the sample.…”

“…Optical sensors using organic ionophores usually show significantly smaller K, e.g. K = 5 x 10 4 L/mole [40], or 10 5 L/mole [41]. We believe this is due to the channel-like nanocavities in zeolite structures wherein cations absorb more strongly than in the rather point-like 'holes' in ring-shaped organic cation sensitiser molecules, e.g.…”

“…1. We find a large stability constant of K = (3.9 +/-0.4) x 10 9 L/mole and LoD of 33 pM, 4 orders-of-magnitude below potentiometric Cs + detection with organic ionophores [15,41]. Our device therefore is well suited to assay water for the potability limit of 7.5 nM Cs + recommended by the Agency for Toxic Substances and Disease Registry [25].…”

Construction of a crystalline 14-metal Zn–Nd rectangular nanocluster with a dual-emissive response towards metal ions

“…For example, K + ion has been reported to be easy to form some intermolecular interaction such as cation-p interaction with macrocyclic compounds and framework complexes due to its suitable ionic size. 25,[38][39][40][41] The interaction between the added metal ions and 1 was investigated by UV-vis titration measurement (Fig. S8 †).…”

Fluorescent Hydrogel‐Coated Paper/Textile as Flexible Chemosensor for Visual and Wearable Mercury(II) Detection

“…Among various solid‐state sensing materials, flexible fluorescent hydrogel films are attracting increasing attention in recent years . This is because hydrogels are hydrophilic, water swellable polymer networks that can allow efficient diffusion of water‐soluble pollutants into the hydrogel matrix .…”