Facile Method for Preparing Surface-Mounted Cucurbit[8]uril-Based Rotaxanes

Surface-immobilized rotaxanes are of practical interest for myriad applications including molecular rotors and analytical sensing. Herein, we present a facile method for the preparation of cucurbit[8]­uril (CB[8])-based rotaxanes on gold (Au) surfaces threaded onto a viologen (MV²⁺) axle. The surface-bound CB[8] rotaxanes were characterized by contact angle measurements and optical microscopy. Direct imaging of the rotaxanes was accomplished by attaching either azobenzene-functionalized silica (Si-azo) colloids or fluorescein-labeled dopamine that were bound to the Au surface through a supramolecular heteroternary (1:1:1) complex with CB[8]. The surface density of CB[8] rotaxanes was examined based on their detection of dopamine. The calculated surface density is 4.8 × 10¹³ molecules·cm^–2, which is only slightly lower than the theoretical value of 5.0 × 10¹³ molecules·cm^–2. Surface-functionalized rotaxanes can be reversibly switched using external stimuli to bind electron-rich second guests for CB[8], including both small molecules such as dopamine and appropriately-functionalized colloidal particles. Such controlled reversibility gives rise to potential applications including selective sensing or reusable templates for preparing well-defined colloidal arrays. The formation of the surface-bound rotaxane structure is critical for successfully anchoring CB[8] host molecules onto Au substrates, yielding an interlocked architecture and preventing the dissociation of binary host–guest complex MV²⁺⊂CB­[8]. The MV²⁺⊂CB­[8] rotaxane structure thus effectively maintains the material density on the Au surface and dramatically enhances the stability of the functional surface

Manipulating K‑Storage Mechanism of Soft Carbon via Molecular Design-Driven Structure Transformation

The emerging potassium-ion batteries (PIBs) have been placing stratospheric expectations for realizing grid-scale electrochemical storage of renewable energy. However, the unsatisfactory K-storage of PIB anode materials, especially promising carbonaceous materials, significantly limited the development of PIBs. Here, a molecular design strategy was proposed to realize controllable structure transformation of soft carbon (SC) materials for enhanced K-storage performance. The optimized SC-PCN material delivered a high reversible K-storage capacity of 838 mAh/g at 50 mA/g, outstanding rate capability (213 mAh/g at 1000 mA/g), and excellent long-term cycling performance (301 mAh/g maintained after 300 cycles at 500 mA/g), superior to most previously reported carbon-based PIB anodes materials. Reaction kinetic analysis revealed that the proposed molecular design strategy can achieve the transformation from a surface capacitive-dominated mechanism to a capacitive-diffusion hybrid mechanism for SC-PCN, benefiting from its unique microstructures with highly defective surface generated via the synergistic effect from template removal, N doping, and surface reconstruction. The optimal hybrid K-storage mechanism should be responsible for the excellent K-storage properties of the prepared SC-PCN

Structure Manipulation of C₁N₁‑Derived N‑Doped Defective Carbon Nanosheets to Significantly Boost K‑Storage Performance

Nanocarbon materials demonstrated huge advantages for K-storage applications due to their wide range of structural tunabilities. However, their K-storage performance was still limited by the underutilization of disordered and ordered carbon structures simultaneously. Here, we developed a C1N1-based reconstruction strategy to fabricate N-doped defective carbon nanosheet (NdC) materials for K-storage. The disordered carbon defects and ordered carbon interlayers were well balanced via choosing suitable precursors for self-condensation generation of the C1N1 skeleton as well as subsequently regulating the high-temperature reconstruction process, resulting in a significantly enhanced intercalation-adsorption K-storage mechanism. As a result, the optimized G-NdC materials delivered a high reversible discharging capacity of 620 mA h/g at 50 mA/g and 241 mA h/g even at 1000 mA/g as well as 210 mA h/g after 300 cycles at 500 mA/g. These excellent K-storage properties should be ascribed to the unique order–disorder balanced microstructures with fast surface capacitive-controlled reaction kinetics. This study emphasized the important roles of carbon defects in the K-storage process and provides a deep insight into the understanding of nanocarbon-based K-storage mechanisms

Imaging GPCR Dimerization in Living Cells with Cucurbit[7]uril and Hemicyanine as a “Turn-On” Fluorescence Probe

Although multiple forms of dimers have been described for GPCR, their dynamics and function are still controversially discussed field. Fluorescence microscopy allows GPCR to be imaged within their native context; however, a key challenge is to site-specifically incorporate reporter moieties that can produce high-quality signals upon formation of GPCR dimers. To this end, we propose a supramolecular sensor approach to detect agonist-induced dimer formation of μ-opioid receptors (μORs) at the surface of intact cells. With the macrocyclic host cucurbit[7]uril and its guest hemicyanine dye tethered to aptamer strands directed against the histidine residues, the sensing module is assembled by host–guest complexation once the histidine-tagged μORs dimerize and bring the discrete supramolecular units into close proximity. With the enhanced sensitivity attributed by the “turn-on” fluorescence emission and high specificity afforded by the intermolecular recognition, in situ visualization of dynamic GPCR dimerization was realized with high precision, thereby validating the supramolecular sensing entity as a sophisticated and versatile strategy to investigate GPCR dimers, which represent an obvious therapeutic target