Abstract
Fluorescent nanoprobes containing ionophores and solvatochromic dyes (SDs) were previously reported as an alternative to chromoionophore-based nano-optodes. However, the small-molecular SDs are prone to leakage and sequestration in complex samples. Here, we chemically attached the SDs to the surface of organosilica nanospheres through copper-catalyzed Click chemistry to prevent dye leakage. The nano-optodes remained well responsive to K+ even after exposure to a large amount of cation-exchange resin, which acted as a sink of the SDs. The potassium nanoprobes exhibited a dynamic range between 1 μM to 10 mM and a good selectivity thanks to valinomycin. Preliminary sensing device based on a nylon filter paper and agarose hydrogel was demonstrated. The results indicate that the covalent anchoring of SDs on nanospheres is promising for developing ionophore-based nanoprobes.
Highlights
Attached SolvatochromicPotassium ion (K+ ), a very important biological inorganic cation, can be detected with a variety of electrochemical and optical chemical sensors [1–7]
The potassium ionophore valinomycin and the cation exchanger were incorporated in organosilica nanospheres
The nanospheres were characterized with transmission electron microscopy (TEM, Figure S5) and dynamic were with The transmission microscopy
Summary
Attached SolvatochromicPotassium ion (K+ ), a very important biological inorganic cation, can be detected with a variety of electrochemical and optical chemical sensors [1–7]. Several research groups are interested in developing the nanoscale ion-selective optodes in the form of various nanoparticles [11,14–18]. The nano-optodes could share a similar sensing mechanism with polymer film-based bulk optodes where an increase of K+ concentration ([K+ ]) leads to the deprotonation of a pH indicator (H+ chromoionophore) in the nanospheres [19–21]. The group of Bakker, Michalska, Clark, Cash, and our own have reported such nano-optodes based on different materials including Pluronic F-127, lipid covered plasticizer nanodroplets, conducting polymers, organosilicas, and quantum dots [14,15,22–29]. This approach is known to suffer from a cross-response from sample pH changes.
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