4-Sulfonatocalixarene-induced nanoparticle formation of methylimidazolium-conjugated dextrans: Utilization for drug encapsulation

Methylimidazolium side groups were grafted via ether linkage to dextran and the self-assembly of these polymers with 4-sulfonato-calix[n]arenes (SCXn) was studied in aqueous solutions. Dynamic light scattering and zeta potential measurements revealed the mixing ratio ranges of the constituents where stable nanoparticles could be created. The macrocycle size of SCXn and the molecular mass of the polymer barely affected the nanoparticle diameter, but the lowering of the imidazolium degree of substitution substantially diminished the stability of the associates. The pH change from neutral to acidic also unfavourably influenced the self-organization owing mainly to the decrease of the SCXn charge. Cryogenic transmission electron microscopy images proved the spherical morphology of the nanoproducts in which the stoichiometry of the constituents was always close to the one corresponding to charge compensation. The flexible and positively charged dextran-chains are compacted by the polyanionic SCXn. Coralyne, a pharmacologically important alkaloid was efficiently embedded by self-assembly in the produced nanoparticles reaching 99% association efficiency. © 2019 Elsevier Lt

Reversible Nanoparticle–Micelle Transformation of Ionic Liquid–Sulfonatocalix[6]arene Aggregates

The effect of temperature and NaCl concentration variations on the self-assembly of 1-methyl-3- tetradecylimidazolium (C14mim+) and 4-sulfonatocalix[6]- arene (SCX6) was studied by dynamic light scattering and isothermal calorimetric methods at pH 7. Inclusion complex formation promoted the self-assembly to spherical nanoparticles (NP), which transformed to supramolecular micelles (SM) in the presence of NaCl. Highly reversible, temperature-responsive behavior was observed, and the conditions of the NP−SM transition could be tuned by the alteration of C14mim+:SCX6 mixing ratio and NaCl concentration. The association to SM was always exothermic with enthalpy independent of the amount of NaCl. In contrast, NPs were produced in endothermic process at low temperature, and the enthalpy change became less favorable upon increase in NaCl concentration. The NP formation was accompanied by negative molar heat capacity change, which further diminished when NaCl concentration was raised

Macroscopic and mesoscopic surface diffusion from a deposit formed by a Stranski-Krastanov type of growth: Pb on Cu(100) at above one layer coverage

Under ultrahigh-vacuum conditions, we have studied the diffusion from Pb deposits on Cu(100), at above one-layer coverage, in the 250–625 K temperature range. The growth mode is Stranski-Krastanov, and the deposits consist of thick three-dimensional Pb islands which form above a dense Pb single layer. This latter layer has a two-domain structure which “melts” around TM=520 K. In the 475–625 K temperature range, we have measured the spread of the deposits in the mm range, using in situ Rutherford backscattering analysis. To study diffusion at lower temperature, on a smaller scale, the Pb layer between the islands has been removed by sputtering around 150 K. We have then studied, in the 250–380 K temperature range, the kinetics of its reformation by using in situ Auger spectroscopy. In these experiments the Pb diffusion is followed over distances of the order of the spacing between Pb islands, i.e., about 1 μm. Our measurements demonstrate that the diffusing species is a Pb adatom moving above the dense Pb layer, leading to its spread with a quasiconstant Pb concentration, the adatom source being the Pb islands. We have analyzed our results via numerical integration of a diffusion equation with a concentration-dependent diffusion coefficient, using the finite-difference method. This analysis provides the activation energy ET governing the process. ET is the sum of two characteristic energies ES and Ed. ES is the formation energy of Pb adatoms from the islands, and Ed the activation energy for the motion of these adatoms on the Pb layer. Ed is markedly higher below TM than above, indicating that when the Pb layer is structured, the diffusion is probably limited by the crossing of domain boundaries

Isotopically Labeled Nanoparticles at Relevant Concentrations: How Low Can We Go? The Case of CdSe/ZnS QDs in Surface Waters

International audienceAnalytical barriers impose work at nanoparticles (NPs) concentrations orders of magnitude higher than the expected NPs concentrations in the environment. To overcome these limitations, the use of nontraditional stable isotope tracers incorporated in NPs (spiked-NPs) coupled with HR-ICP-MS has been proposed. The performance and efficiency of this analytical method was assessed in the case of quantum dots (QDs). Multi-isotopically labeled 111Cd77Se/68ZnS QDs were synthesized and their dissemination in natural aquatic matrices (river, estuarine and sea waters) was modeled at very low concentrations (from 0.1 to 5000 ppt). The QD limits of quantification (QD-LOQ) in each matrix were calculated according to the isotopic tracer. In ultrapure and simple medium (HNO3 2%), Zn, Cd, and Se originated from the QDs were quantifiable at concentrations of 10, 0.3, and 6 ppt, respectively, which are lower than the conventional HR-ICP-MS LOQs. In aquatic matrices, the QD-LOQs increase 10-, 130-, and 250-fold for Zn, Cd, and Se, respectively, but remain relevant of environmental concentrations (3.4 ppt ≤ QD-LOQs ≤ 2.5 ppb). These results validate the use of isotopically labeled ENPs at relevant concentrations in experimental studies related to either their fate, behavior, or toxicity in most aquatic matrices

Synthesis, binding and self-assembly properties of a well-defined pillar[5]arene end functionalised polydimethylacrylamide

International audienceThe synthesis, binding and self-assembly properties of a well-defined pillar[5]arene end-functionalised poly(dimethylacrylamide)(MePilla-PDMAC) are reported. In order to synthesise MePilla-PDMAC, a new trithiocarbonate type RAFT agent MePilla-CTA was developed incorporting a partially methylated pillar[5]-arene moiety. Kinetic studies clearly indicated the propensity of MePilla-CTA to control the polymeri-sation of DMAC. Interestingly, as PDMAC type chains display good solubilty both in organic and aqueous media, MePilla-PDMAC was able of specifically bind electron deficient guest molecules at the α-chain-end both in chloroform and water. Complex formation was found to be reversible upon addition of chloride anions or heating in organic and aqueous media, respectively. Furthermore, cryo-TEM, VT-NMR (1 H) and VT-DLS investigations also indicated the ability of MePilla-PDMAC to self-assemble into micelle-like aggregates in water showing reversible recognition properties

Electron Transfer at Oxide/Water Interfaces Induced by Ionizing Radiation

The electron transfer from oxide into water is studied in nanoparticle suspensions of various oxides (SiO₂, ZnO, Al₂O₃, Nd₂O₃, Sm₂O₃, and Er₂O₃) by means of pulse and γ radiolysis. The time-resolved and steady-state investigations of the present study demonstrate independently that whatever the band gap and the electron affinity of the oxide, the electron transfer always takes place in these nanometric systems: Irradiation generates hot electrons which have enough energy to cross the semiconductor–liquid interface. Moreover, picosecond measurements evidence that the spectrum of the solvated electron is the same as in water. Lastly, the decay of the solvated electron is similar on the picosecond to nanosecond time scale in water and in these suspensions, but it is clearly different on the nanosecond to microsecond time scale