A series of bio-compatible metal-organic frameworks (MOFs) have been studied as potential carriers for drug delivery applications. Grand canonical Monte Carlo (GCMC) simulations were performed to ...study the adsorption of the model drug ibuprofen. Simulations were first validated with available experimental data for ibuprofen adsorption and release in MIL-53, MIL-100 and MIL-101. In the second stage, the study was extended to three additional MOFs with interesting properties in terms of bio-compatibility and porosity: CDMOF-1, based on edible precursors; MOF-74 containing a highly biocompatible metal (Mg); and BioMOF-100, a mesoporous MOF with extremely high pore volume. By comparing with experimental data, we show how GCMC simulation is able to predict the macroscopic performance of new porous MOFs in drug delivery applications, providing useful molecular-level insights and giving thermodynamic and structural details of the process. Adsorption isotherms, snapshots, energy of adsorption and radial distribution functions were used to analyse the drug delivery process.
Trivalent lanthanide ions (Ln3+) are used to prepare a plethora of coordination compounds, with metal–organic frameworks (MOFs) being among the most sought-after in recent years. The porosity of ...Ln-MOFs is often complemented by the luminescence imparted by the metal centers, making them attractive multifunctional materials. Here, we report a class of three-dimensional (3D) MOFs obtained from a solvothermal reaction between 2,6-naphthalenedicarboxylic acid (H2NDC) and lanthanide chlorides, yielding three types of compounds depending on the chosen lanthanide: LnCl(NDC)(DMF) for Ln3+ = La3+, Ce3+, Pr3+, Nd3+, Sm3+ (type 1), Eu(NDC)1.5(DMF)·0.5DMF (type 2), and Ln2(NDC)3(DMF)2 for Ln3+ = Tb3+, Dy3+, Y3+, Er3+, Yb3+ (type 3). Photoluminescent properties of selected phases were explored at room temperature. The luminescence thermometry capability of Yb3+-doped Nd-MOF was fully investigated in the 15–300 K temperature range under 365 and 808 nm excitation. To describe the optical behavior of the isolated MOFs, we introduce the total energy-transfer balance model. Therein, the sum of energy-transfer rates is considered along with its dependence on the temperaturethe sign, magnitude, and variation of this parameterpermitting to afford a thorough interpretation of the observed behavior of the luminescent species of all materials presented here. The combination of novel theoretical and experimental studies presented herein to describe energy-transfer processes in luminescent materials can pave the way toward the design of MOF-based chemical and physical sensors working in an optical range of interest for biomedical applications.
The novel Yb succinate metal–organic framework exhibits a reversible single‐crystal to single‐crystal polymorphic transformation (see figure) when it is heated above 130 °C, returning to its initial ...form when back at room temperature. This transformation produces a change in the coordination sphere of the Yb atoms, which influences the catalytic activity of the material.
Yb(C4H4O4)1.5 undergoes a temperature‐triggered single‐crystal to single‐crystal transformation. Thermal X‐ray single‐crystal studies showed a reversibly orchestrated rearrangement of the atoms generated by the breaking/formation of coordination bonds, in which the stoichiometry of the compound remains unchanged. The transformation occurs on heating the crystal at ≈130 °C. This uncommon behavior was also studied by thermal methods, FTIR spectroscopy, and thermodiffractometry. Both polymorphs, α (room‐temperature form) and β (high‐temperature form), are proven to be active heterogeneous catalysts; the higher catalytic activity of β is owed to a decrease in the Yb coordination number. A mechanism based on spectroscopic evidence and involving formation of the active species YbOOH is proposed for the sulfide oxidation.
The novel Yb succinate metal–organic framework exhibits a reversible single‐crystal to single‐crystal polymorphic transformation (see figure) when it is heated above 130 °C, returning to its initial form when back at room temperature. This transformation produces a change in the coordination sphere of the Yb atoms, which influences the catalytic activity of the material.
Coordination networks (CNs) with tailorable multi‐metallic composition were designed and then used as sacrificial materials to obtain promising materials with Up‐conversion (UC) properties. The ...metal‐organic precursors led to solid solutions of Rare‐Earth Oxides (REO)Y2O3:Yb3+/Er3+ or Y2O3:Yb3+/Er3+/Gd3 through a calcination process. In order to obtain luminescent UC platforms, spin‐coating technique was implemented to deposit these materials onto glass supports. The synthesized solids and the resulting films were characterized by Scanning Electron Microscopy – Energy Dispersive Spectroscopy (SEM‐EDS), infrared spectroscopy, powder (PXRD), and grazing incidence (GIXRD) X‐ray diffraction techniques. Moreover, the photophysical properties of bulk and deposited Y2O3:Ln3+ doped oxides were evaluated after being irradiated with NIR wavelength (980 nm) laser to excite the Yb3+ sensitizer ion. Besides, decay emission profiles from each sample were also obtained and lifetime (τobs) values were calculated. These results open up the implementation of REO thin films obtained through CN calcination for promising applications such as solar cells and sensor devices.
Multi‐metallic CNs were employed as sacrificial materials through a calcination process to obtain REOs with up‐conversion properties. REOs were deposited on glass substrates by spin‐coating to obtain luminescent thin films. Bulk and films were photophysically characterized after being irradiated with a NIR wavelength (980 nm) laser. The results are promising for the application of thin films in areas like solar cells and/or sensor devices.
Two new holmium–succinate frameworks have been synthesized by hydrolysis in situ of the succinylsalicylic acid under different hydrothermal conditions. Compound 1, Ho2(C4H4O4)3(H2O)2·0.33(C7H6O3), ...Pi̅ space group, has a novel structure composed by 1D-SBUs consisting of HoO9 chains of polyhedra linked by the succinate ligands giving a 3D framework. Compound 2, Ho2(C4H4O4)3(H2O)2, also belonging to the Pi̅ space group, has a denser structure. The role of the in-situ-generated salicylic acid on formation of both structures is studied by means of a synthesis design methodology. A topological study of the new holmium succinate compounds in comparison with the previously reported 3D holmium–succinate framework is performed here.
Abstract
One of the features unique in Bi-2212/Ag wires is the network of bridges between the filaments formed by grains grown through the Ag matrix during the partial-melt heat treatment process. ...Although these interconnections favor a redistribution of the current among the filaments allowing high critical current density, they represent a strong electrical coupling between the filaments themselves. Such a coupling increases the AC losses, present also in the case of the charge and discharge of DC magnets, and principal applications of this kind of superconductor. In this work, through transport and magnetic measurements and their comparison, we study the behavior of these bridges as a function of applied magnetic field and temperature and the implications they have on the electrical coupling. The experiment has been performed on two multifilamentary wires prepared by Groove-Die-Groove Powder In Tube process starting from two commercial Bi-2212 precursor powders: Nexans and Engi-Mat. The reported results show that the effective length scale on which the filaments are coupled is dependent on the field and temperature, passing from the filaments-bundle diameter at low field and temperature to single filament diameter at high field and temperature. Although the two samples have different Jc values, such filaments coupling behavior is common to both. We believe that these findings are very useful in magnet design.
Water-ethanol suspensions of 2D coordination network (CN) based on rare earth elements and mixed ligands were evaluated as reactive oxygen species (ROS) generators under UV light irradiation, in ...contact with a biomimetic substrate (tryptophan) or an O2(1Δg) quencher (1,3-diphenylisobenzofuran; 1,3-DPBF). A combination of bottom-up and top-down strategies was implemented in order to obtain nano-sized CN particles and the subsequent colloidal suspensions were also tested towards photodynamic inactivation of Candida albicans (C. albicans). SEM, TEM, FTIR, and XRD techniques were applied to characterize the solids and ICP-AES was employed to determine the metal content of the colloidal suspensions. Promising results were found indicating that the presence of Tb3+ allows an intersystem crossing suitable for singlet oxygen generation, resulting in the antifungal activity of C. albicans culture upon UV-irradiation.
In this paper the roles of texturing and thickness of different buffer layers employed in the fabrication of Fe(Se,Te) coated conductors are studied. Fe(Se,Te) thin films were deposited either on ...rolling assisted biaxially textured substrates substrates with highly textured CeO2 buffer layer and on HASTELLOY® C276 substrates with a randomly oriented native oxide grown through different oxidizing processes. It was found that the buffer layer has to be both thick enough to block Ni interdiffusion from the metallic tape to the Fe(Se,Te) overlayer, and textured enough to ensure good in-plane alignment of the superconducting film, and consequently good critical current densities (Jc). The best results in terms of critical temperature (Tc) and critical current were obtained using a highly textured 350 nm thick CeO2 buffer layer, but a fairly good Jc of 1.2 104 A cm−2 in self field at 5 K was also obtained using an HASTELLOY® C276 substrate with a 400 nm thick randomly oriented native oxide. The obtained results indicate that the superconducting properties of the Fe(Se,Te) coated conductors are determined by a trade-off between degree of texturing of the substrate and inhibition of Nickel interdiffusion.
The introduction of H-bond donor/acceptor functionality into metal–organic frameworks (MOFs) can have a beneficial effect on their molecular recognition, uptake selectivity and catalytic properties. ...The changes in ligand geometry induced by incorporation of functional groups may also affect the topology and composition of the resultant MOFs. Herein, we present a comprehensive study of functional group incorporation into MOFs, linked by either Zn
2+
paddlewheel units or monomeric Zn
2+
corners, which exhibit
pcu
and
dia
topology, respectively. Crystallographic analysis shows that amide groups can be easily incorporated into isoreticular
pcu
pillared-MOFs, whilst integration of urea units results in materials with
dia
topology. Molecular simulations allow the examination of hypothetical structures with differing constitutions and topologies, and highlight the influence of the urea units in generating the experimentally observed topologies. Noncovalent interactions between independent nets may be significant structure-directing influences, a finding which has great implications for the design of MOFs containing more complex functional groups.
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