Search results for "cucurbituril"
showing 10 items of 15 documents
Strong Emission Enhancement in pH-Responsive 2:2 Cucurbit[8]uril Complexes
2019
Organic fluorophores, particularly stimuli-responsive molecules, are very interesting for biological and material sciences applications, but frequently limited by aggregation- and rotation-caused photoluminescence quenching. A series of easily accessible bipyridinium fluorophores, whose emission is quenched by a twisted intramolecular charge-transfer (TICT) mechanism, is reported. Encapsulation in a cucurbit[7]uril host gave a 1:1 complex exhibiting a moderate emission increase due to destabilization of the TICT state inside the apolar cucurbituril cavity. A much stronger fluorescence enhancement is observed in 2:2 complexes with the larger cucurbit[8]uril, which is caused by additional con…
Chiral hemicucurbit[8]uril as an anion receptor: selectivity to size, shape and charge distribution
2017
A novel eight-membered macrocycle of the hemicucurbit[n]uril family, chiral (all-R)-cyclohexanohemicucurbit[8]uril (cycHC[8]) binds anions in a purely protic solvent with remarkable selectivity. The cycHC[8] portals open and close to fully encapsulate anions in a 1 : 1 ratio, resembling a molecular Pac-Man™. Comprehensive gas, solution and solid phase studies prove that the binding is governed by the size, shape and charge distribution of the bound anion. Gas phase studies show an order of SbF6− ≈ PF6− > ReO4− > ClO4− > SCN− > BF4− > HSO4− > CF3SO3− for anion complexation strength. An extensive crystallographic study reveals the preferred orientations of the anions within the octahedral cav…
Ecocompatible Halloysite/Cucurbit[8]uril Hybrid as Efficient Nanosponge for Pollutants Removal
2016
Hybrid materials based on halloysite nanotubes (HNT) and cucurbit[8]uril (CB[8]) were prepared with the aim to obtain efficient nanosponges towards hydrocarbons both in liquid and vapor phases. The loading on both HNT surfaces and the hybrid morphology were evidenced by FTIR spectroscopy, thermogravimetric analysis and scanning electron microscopy. In order to highlight the interactions in the hybrid 13C {1H} CP-MAS NMR experiments were performed. The aqueous colloidal stability of HNT/CB[8] was highlighted through ζ potential and dynamic light scattering measurements. The HNT/CB[8] composite was employed as nanosponge to capture aromatic oils in aqueous phase as evidenced by fluorescence e…
Enhanced catalytic electrochemical reduction of dissolved oxygen with ultracleancucurbituril[7]-capped gold nanoparticles
2014
Gold nanoparticles capped with cucurbituril[7] have been prepared in the absence of metallic cations and organic ligands. Remarkably, these nanohybrids encapsulate dissolved oxygen and are highly active in electrochemical reduction. The effect of the presence of sodium and ammonium salts on this catalysed process is also analysed.
Binding abilities of new cyclodextrin-cucurbituril supramolecular hosts
2015
Various combined techniques (UV–vis spectrophotometry, isothermal titration calorimetry, thermogravimetry, ESI-MS mass spectrometry, polarimetry and 1H NMR spectroscopy) were used in order to study the interaction between a new combined supramolecular host, namely a bow-tie-structured cyclodextrin–cucurbituril association solely held by non-covalent interactions, and a suitably selected guest, namely the N-(p-nitrophenyl)-1,8-diaminooctane hydrochloride. In particular, the use of different techniques highlighted the peculiar features of the possible host–guest supramolecular interactions under different concentration conditions.
Application of the Generalized Molar-Ratio Method to the Determination of the Stoichiometry and Apparent Binding Constant of Nanoparticle-Organic Cap…
2015
A generalization of the molar-ratio method is applied to the determination of the stoichiometry and apparent binding constant of metal nanoparticle-organic capping complexes (MmLx) using voltammetric data for the oxygen reduction reaction (ORR) in air-saturated aqueous phosphate buffer solutions. The method is applied to the formation of binary nanohybrids consisting of gold nanoparticles (AuNPs) capped with a rigid spacer, cucurbit[7]uril (CB), termed AuNP@CB, as well as to the formation of their ternary complexes (MmLxBz) with methylene blue (MB), termed AuNP@CB@MB. The obtained stoichiometries correspond to binding of four Au surface atoms for each CB unit.
Breaking the Nd3+-sensitized upconversion nanoparticles myth about the need of onion-layered structures
2018
Up to now, most strategies to build efficient 800 nm-light responsive upconversion nanoparticles (UCNPs) have included onion-layered structures, in which Nd3+ is confined within the inorganic crystal structure of at least one layer. We report here an easy room-temperature modular preparation of core-shell UCNPs consisting of NaYF4:Yb,Er(Tm)/NaYF4 (UCCS) with Nd3+ anchored at the organic capping by using cucurbituril[7] (CB[7]) as an adhesive. Strikingly, excitation at 800 nm effectively triggers the upconversion emission of UCCS@CB[7]@Nd nanohybrids.
Nanocomposite based on Multi-Macrocyclic Receptors and Halloysite for Volatile Organic Compounds Capture
2015
Volatile organic compounds (VOCs) are chemicals released to the atmosphere by natural and anthropogenic sources. VOCs are hazardous air pollutants and promote formation of photochemical smog. Variety of chemicals released from pharmaceutical industry includes priority pollutants like benzene, toluene, and dichloromethane. The aim of this work was at designing, preparing and characterizing from the physico-chemical view-point a pseudo nano-sponge with low environmental impact for pollutant removal. As adsorbent material, a nanocomposite based on nanoclay and cucurbiturils, which are biocompatible materials, were investigated. Clay minerals (e.g. montmorillonite and kaolin) are important comp…
Chiral hemicucurbit[8]uril as an anion receptor: selectivity to size, shape and charge distribution
2017
A novel eight-membered macrocycle of the hemicucurbit[n]uril family, chiral (all-R)-cyclohexanohemicucurbit[8]uril (cycHC[8]) binds anions in a purely protic solvent with remarkable selectivity. The cycHC[8] portals open and close to fully encapsulate anions in a 1 : 1 ratio, resembling a molecular Pac-Man™. Comprehensive gas, solution and solid phase studies prove that the binding is governed by the size, shape and charge distribution of the bound anion. Gas phase studies show an order of SbF6− ≈ PF6− > ReO4− > ClO4− > SCN− > BF4− > HSO4− > CF3SO3− for anion complexation strength. An extensive crystallographic study reveals the preferred orientations of the anions within the octahedral cav…
Chemistry inside molecular containers in the gas phase.
2013
Inner-phase chemical reactions of guest molecules encapsulated in a macromolecular cavity give fundamental insight into the relative stabilization of transition states by the surrounding walls of the host, thereby modelling the situation of substrates in enzymatic binding pockets. Although in solution several examples of inner-phase reactions are known, the use of cucurbiturils as macrocyclic hosts and bicyclic azoalkanes as guests has now enabled a systematic mass spectrometric investigation of inner-phase reactions in the gas phase, where typically the supply of thermal energy results in dissociation of the supramolecular host-guest assembly. The results reveal a sensitive interplay in wh…