Aggregation-induced chemical reactions: acid dissociation in growing water clusters

Understanding chemical reactivity at ultracold conditions, thus enabling molecular syntheses via interstellar and atmospheric processes, is a key issue in cryochemistry. In particular, acid dissociation and proton transfer reactions are ubiquitous in aqueous microsolvation environments. Here, the full dissociation of a HCl molecule upon stepwise solvation by a small number of water molecules at low temperatures, as relevant to helium nanodroplet isolation (HENDI) spectroscopy, is analyzed in mechanistic detail. It is found that upon successive aggregation of HCl with H2O molecules, a series of cyclic heteromolecular structures, up to and including HCl(H2O)3, are initially obtained before a precursor state for dissociation, HCl(H2O)3···H2O, is observed upon addition of a fourth water molecule. The latter partially aggregated structure can be viewed as an “activated species”, which readily leads to dissociation of HCl and to the formation of a solvent-shared ion pair, H3O+(H2O)3Cl−. Overall, the process is mostly downhill in potential energy, and, in addition, small remaining barriers are overcome by using kinetic energy released as a result of forming hydrogen bonds due to aggregation. The associated barrier is not ruled by thermal equilibrium but is generated by athermal non-equilibrium dynamics. These “aggregation-induced chemical reactions” are expected to be of broad relevance to chemistry at ultralow temperature much beyond HENDI spectroscopy

Effect of Geometrical Structure, Drying, and Synthetic Method on Aminated Chitosan-Coated Magnetic Nanoparticles Utility for HSA Effective Immobilization

Human serum albumin (HSA) is one of the most frequently immobilized proteins on the surface of carriers, including magnetic nanoparticles. This is because the drug−HSA interaction study is one of the basic pharmacokinetic parameters determined for drugs. In spite of many works describing the immobilization of HSA and the binding of active substances, research describing the influence of the used support on the effectiveness of immobilization is missing. There are also no reports about the effect of the support drying method on the effectiveness of protein immobilization. This paper examines the effect of both the method of functionalizing the polymer coating covering magnetic nanoparticles (MNPs), and the drying methods for the immobilization of HSA. Albumin was immobilized on three types of aminated chitosan-coated nanoparticles with a different content of amino groups long distanced from the surface Fe3O4-CS-Et(NH2)1−3. The obtained results showed that both the synthesis method and the method of drying nanoparticles have a large impact on the effectiveness of immobilization. Due to the fact that the results obtained for Fe3O4-CS-Et(NH2)2 significantly differ from those obtained for the others, the influence of the geometry of the shell structure on the ability to bind HSA was also explained by molecular dynamics

Tris(8-hydroxyquinoline)aluminium in a polymer matrix as an active layer for green OLED applications

Tris(8-hydroxyquinoline)aluminium with poly(N-vinylcarbazole) (Alq₃:PVK) or polystyrene sulfonate (Alq₃:PSS) were deposited by spin-coating on glass and silicon substrates. SEM measurements show that relatively smooth thin films were obtained. Fourier transform infrared measurements were performed to confirm the composition of the samples. The optical properties of thin films containing Alq₃:PVK and Alq₃:PSS were characterised using absorption spectroscopy and spectroscopic ellipsometry. It was found that the absorption spectrum of Alq₃:PVK is characterised by four bands, while for Alq₃:PSS only three bands are visible. The photoluminescence of the studied thin layers shows a peak with a maximum at about 500 nm. Additionally, cyclic voltammetry of Alq₃ is also presented. Theoretical density functional theory calculations provide the insight into the interaction and nature of Alq₃:PVK and Alq₃:PSS excited states. Finally, the organic light-emitting diode (OLED) structure based on Alq₃:PVK was fabricated and showed strong electroluminescence with a green emission at 520 nm. The results of the device show that the ITO/PEDOT:PSS/Alq₃:PVK/Ca/Al system can be useful for the production of low-cost OLEDs with Alq₃:PVK as an active layer for future lighting applications