Abstract Novel supramolecular vesicles based on host–guest systems were coassembled from carboxylate‐substituted pillar[6]arene (CPA[6]) and disulfide‐linked benzimidazolium amphiphiles, and the microstructures of the CPA‐based supramolecular vesicles were clearly elaborated. The supramolecular vesicles showed controlled drug release in response to five stimuli, with glutathione, pH, CO 2 , Zn 2+ ions, and hexanediamine, leading to cleavage of the disulfide bonds, protonation of the carboxylate groups, metal chelation, and competitive binding. This is the first case of a smart pillararene‐based supramolecular vesicle being integrated with five stimuli‐responsive functions to meet the diverse requirements of controlled drug release. Importantly, each of the five stimuli is closely related to microenvironments of tumors and diseases of the human body. The smart stimuli‐responsive supramolecular vesicles have promising applications in drug therapy of tumors and relevant diseases.
Sensitive electrochemical sensors were fabricated with reduced graphene oxide-supported Au@Pd (Au@Pd-RGO) nanocomposites by one-step synthesis for individual and simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) with low detection limits and wide concentration ranges. From the Au@Pd-RGO-modified electrodes, well-separated oxidation peaks and enhanced peak currents of AA, DA, and UA were observed owing to the superior conductivity of RGO and the excellent catalytic activity of Au@Pd nanoparticles. For individual detection, the linear responses of AA, DA, and UA were in the concentration ranges of 0.1–1000, 0.01–100, and 0.02–500 μM with detection limits of 0.02, 0.002, and 0.005 μM (S/N = 3), respectively. For simultaneous detection by synchronous change of the concentrations of AA, DA, and UA, the linear response ranges were 1–800, 0.1–100, and 0.1–350 μM with detection limits of 0.28, 0.024, and 0.02 μM (S/N = 3), respectively. The fabricated sensors were further applied to the detection of AA, DA, and UA in urine samples. The Au@Pd-RGO nanocomposites have promising applications in highly sensitive and selective electrochemical sensing.
Surface pressure (π)−molecular area (A) compression/expansion isotherms of N-octadecanoyl-l-alanine reflect homochiral discrimination behavior of the enantiomeric monolayer. FTIR studies indicate that carboxylic acid groups form out-of-plane ring dimers between two adjacent N-octadecanoyl-l-alanine molecules in monolayer LB films and that the long hydrocarbon chains in the film matrix take a biaxial orientation. The enantiomeric molecules assemble regularly and twist from neighbor to neighbor, thus giving rise to chirality of the aggregate in the two-dimensional condensed phase. Prior to the phase transition, the transformation of the triclinic subcell packing of the hydrocarbon chains into a hexagonal packing occurs. The variable-temperature infrared spectra of LB films provide powerful evidence for the formation of a hydrogen-bonded structure between chiral headgroups.
This paper reports dual enhanced electrochemiluminescence (ECL) of CdS quantum dot (QD)-decorated aminated Au@SiO2 core/shell (Au@SiO2-NH2/CdS) superstructures. A maximum ECL emission of the Au@SiO2-NH2/CdS superstructures (Au core, ca. 55 nm) with a silica shell of 38 nm was 35-fold stronger than that of the counterparts (containing neither Au cores nor amino groups) with H2O2 as a coreactant. The fold of ECL enhancement is the largest, and the optical path of maximum ECL enhancement is the longest reported so far. The larger the Au cores in the superstructures, the stronger the ECL emission of CdS QDs was. Two types of ECL enhancement mechanisms were clearly proposed for the dual enhanced ECL of the Au@SiO2-NH2/CdS superstructures. One was the electromagnetic field enhancement induced by localized surface plasmon resonance of Au cores, and the other was the chemical enhancement from amino groups modified on the silica surface involved in the ECL process in the assistance of H2O2. It is the first time to put forward the new concept of chemical enhanced ECL that was directly related to the participation of other chemicals, which caused a decrease in the difference in the redox potential between emitters and coreactants for the increase of their redox currents. The constructed ECL platform was demonstrated to have promising applications in highly sensitive detection of glutathione (GSH), and the response mechanism of GSH was also explored.
Recognition and detection of melamine are of very significance in food industries. Molecular recognitions of barbituric acid lipids to melamine at the air–water interface have been investigated in detail using in situ infrared reflection absorption spectroscopy (IRRAS). Hydrogen bonding patterns and molecular orientations of the molecular recognitions have been revealed. Prior to molecular recognition, the barbituric acid moieties in the monolayers were hydrogen bonded with a flat-on fashion at the air–water interface, and the alkyl chains were preferentially oriented with their CCC planes perpendicular to the water surface. After molecular recognition, the NH2 stretching bands of recognized melamine were clearly observed at the air–water interface as well as primary characteristic bands, the barbituric acid moieties underwent a change in orientation with non-hydrogen bonded C4═O bonds almost perpendicular to the water surface and C2═O and C6═O bonds involved in hydrogen bonds with melamine, and the alkyl chains were preferentially oriented with their CCC planes parallel to the water surface. The monolayers of barbituric acid lipids exhibited excellent selectivity for melamine over nucleosides.
Ion transport and ion exchange in two-dimensional N-octadecanoyl-l-alanine Langmuir−Blodgett (LB) films were studied through FTIR spectroscopy. At the intrinsic pH values of the ion-containing solutions (without any adjustment), the metal ions penetrating into the LB films are selectively exchanged with the carboxylic acid groups of film-forming molecules. This behavior is different from the interactions between the metal ions in aqueous subphases and the corresponding monolayers at the air−water interface. Ion exchange in the N-octadecanoyl-l-alanine LB films is controlled by the structure of the intermolecular hydrogen-bonding network. Ion exchange is favorable to Zn2+and Ag+ ions, as it promotes an increase of intermolecular hydrogen bonds and a decrease of intermolecular distance. Ion exchange is unfavorable to Ca2+, Cd2+, and Ni2+ ions, as it is suppressed by the occurrence of intramolecular hydrogen bonds and the increase of intermolecular distance. The reverse exchange process by protons is consistent with the above results. Ion exchange is unfavorable to zinc and silver salts, as it is suppressed by the weakening of intermolecular hydrogen bonds and the increase of intermolecular distance, and it is extremely favorable to calcium, cadmium, and nickel salts in converting from intramolecular to intermolecular hydrogen bonds.
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