Acid/base- and base/acid-switchable complexation between anionic-/cationic-pillar[6]arenes and a viologen ditosylate salt

pH-Controllable Redox Responsive Amphiphilic Viologens for Switchable Emulsions

A pH and redox dual responsive amphiphilic viologen is synthesized, which can be reversibly transformed among the zwitterionic (SVa), monovalent anionic (SV+), and divalent anionic (SVH2+) forms upon pH variation, exhibiting pH-controllable redox responsive properties. Switchable Pickering emulsions with different droplet size and viscosity are prepared by the mixture of hydrophilic silica nanoparticles and the viologens (SV+ or SVH2+) at acidic conditions, while such combination yielded an oil-in-dispersion emulsion at neutral pH value. Not only can rapid reversible demulsification/stabilization of the Pickering emulsions be achieved by redox reactions, but the rate of redox-demulsification can also be controlled by pH trigger. The dual-responsive amphiphilic viologens have potential applications in developing intelligent colloid materials and molecular logic systems.

The Detection of Food Additives Using a Fluorescence Indicator Based on 6– p–Toluidinylnaphthalence-2-sulfonate and Cationic Pillar[6]arene

The current study investigated host-guest complexation in 6-p-toluidinylnaphthalene-2-sulfonate (TNS), a fluorescence probe used to investigate hydrophobic regions that contain the water-soluble cationic pillar[6]arene (CP6). After complexation with CP6, the fluorescence intensity of TNS was significantly increased. The decreases in the fluorescence intensity of the TNS•CP6 complex when phenolic food-additives are added have been used in indicator displacement assays to detect food additives in the water.

Switchable bifunctional molecular recognition in water using a pH-responsive Endo-functionalized cavity

The construction of water-soluble synthetic hosts with a stimuli-responsive endo-functionalized cavity is challenging. These hosts feature a switchable cavity and may bring new properties to the fields of self-assembly, molecular machines, and biomedical sciences. Herein, we report a pair of water-soluble naphthotubes with a pH-responsive endo-functionalized cavity. The inward-directing secondary amine group of the hosts can be protonated and deprotonated. Thus, the hosts have different cavity features at the two states and show drastically different binding preference and selectivity in water. We reveal that the binding difference of the two host states is originated from the differences in charge repulsion, hydrogen bonding and the hydrophobic effects. Moreover, the guest binding can be easily switched in a ternary mixture with two guest molecules by adjusting the pH value of the solution. These pH-responsive hosts may be used for the construction of smart self-assembly systems and water-soluble molecular machines.

Facile Surface Functionalization of MXene by Pillar[5]arene for Enhanced Electrochemical Performance

A simple strategy was used to prepare functional two-dimensional materials via combination of pillar[5]arene (P5) and MXene. Electrochemical results of MXene-P5 exhibits high supramolecular recognition, enrichment capability, and high electrochemical...

pH-Responsive Host-Guest Complexations Between a Water-Soluble Pillar[6]arene Dodecyl-Ammonium Chloride and Aromatic Sulfonic Acids

In the present work, new host-guest binding motifs based on a water-soluble pillar[6]arene dodecyl-ammonium chloride (CP6) with two aromatic sulfonic acids in aqueous media were fabricated. In accordance with the integrated results of ¹H NMR, 2D NOESY, and florescence titration experiments, it was demonstrated that the host-guest binding of CP6 with the two aromatic sulfonic acids in aqueous solution not only has high binding constants but also has pH-responsiveness.

Facile One-Step Electrodeposition Preparation of Cationic Pillar[6]arene-Modified Graphene Films on Glassy Carbon Electrodes for Enhanced Electrochemical Performance

In the present work, we have developed a facile one-step route for preparing electrochemically reduced graphene oxide-cationic pillar[6]arene (ErGO-CP6) nanocomposite films on glassy carbon electrodes (GCEs) directly from graphene oxide-cationic pillar[6]arene (GO-CP6) colloidal solution by using a pulsed electrodeposition technique. The electrocatalytic activity of ErGO-CP6 was examined by studying the oxidations of five purine bases [adenine (A), guanine (G), xanthine (X), hypoxanthine (HX), and uric acid (UA)]. It enhanced the oxidation currents of A, G, X, HX, and UA when compared to unmodified ErGO films and bare GCE, which is considered to be the synergetic effects of the graphene (excellent electrical properties and large surface area) and CP6 molecules (high inclusion complexation and enrichment capability).

Direct electrodeposition of cationic pillar[6]arene-modified graphene oxide composite films and their host–guest inclusions for enhanced electrochemical performance

Cationic pillar[6]arene functionalized graphene films with enhanced host–guest electrochemical recognition performance were fabricated directly from GO-CP6 dispersions by a one-step pulsed electrodeposition technique.