Synthesis of metal-organic frameworks and their immobilization on surfaces

Els marcs orgànics metàl·lics (MOF, de metal-organic framework) són materials porosos fets d’ions metàl·lics enllaçats a lligands orgànics mitjançant enllaços de coordinació, en què s’obtenen com a resultat estructures amb dues o més dimensions d’unitats repetibles. Últimament, la investigació sobre l’ús de MOF en biologia ha portat a la creació de MOF biològics (BioMOF). A més, la preparació de pel·lícules de MOF i el creixement en superfícies són necessaris per a incorporar MOF en dispositius i produir MOF de superfície coordinada (SURMOF, de surface-coordinated metal-organic framework). En aquest article es presenten la classificació, la síntesi i les aplicacions dels SURMOF.Metal-organic frameworks (MOFs) are porous materials made of metal ions bonded to organic ligands by coordination bonds, resulting in the obtention of structures with two or more dimensions from repeatable units. Lately, research on the use of MOFs in biology has led to the creation of biological MOFs (BioMOFs). In addition, the preparation of MOF films and their growth on functionalized surfaces is required in order to incorporate MOFs into devices and produce surface-coordinated MOFs (SURMOFs). For this reason, SURMOFs’ classification, synthesis and applications are presented in this review

Supramolecular block copolymers incorporating chiral and achiral chromophores for the bottom-up assembly of nanomaterials

The coordination of the chiral metalloporphyrin ([5,10,15,20-[4-(R,R,R,R)-2-N-octadecylamidoethyloxiphenyl]porphyrin] zinc (II)) and an achiral homologue to an amphiphilic block copolymer of poly(styrene-b-4-vinyl pyridine) (PS-b-P4VP) have been studied in solution and as cast material. The resulting chiral dye-polymer hybrid material has been accomplished via axial coordination between the zinc (II) metal ion in the core of the porphyrin ring and the pyridyl units of the block-copolymer in a non-coordinative solvent. The supramolecular organization and possible chirality transfer to the hybrid material have been studied in solution by UV-visible absorption spectroscopy, fluorescence spectroscopy, Nuclear Magnetic Resonance and Circular Dichroism. The morphology of the chiral and achiral doped polymers has been studied in solid state by Transmission Electron Microscopy and Atomic Force Microscopy. We show that the nanostructures formed depend greatly upon the nature of the side-chains on the porphyrins, where a chiral group leads to a very homogeneous phase-separated material, perhaps indicating that chiral side groups are useful for the preparation of this type of supramolecular hybridPostprint (author's final draft

Functional supramolecular tetrathiafulvalene-based films with mixed valences states

Tetrathiafulvalene molecules substituted with a carboxylic acid group (TTFCOOH) were bound as redox-active moieties into a poly(4-vinyl pyridine) (P4VP) skeleton through non-covalent interactions (hydrogen bonds). The aspect of the resulting P4VP-TTFCOOH films showed a uniform and smooth morphology. Moreover, the redox function of TTFCOOH in P4VP-TTFCOOH was demonstrated using tetrachloroauric acid, iron(III) perchlorate and iodine vapors as doping agents. The oxidized states of TTFCOOH as well as the mixed valance state TTFCOOH0-TTFCOOH+• were generated in a controlled manner in solid state, resulting in an organic film capable of charge transport. The charge transport along the organic donor molecules hydrogen bonded to the polymer matrix was demonstrated employing Electrostatic Force Microscopy (EFM)Postprint (author's final draft

Carbon-paste nanocomposites as unconventional gate electrodes for electrolyte-gated organic field-effect transistors: electrical modulation and bio-sensing

Nanocomposite carbon-paste electrodes (NC-CPEs) have been investigated for the first time in electrolytegated organic field-e¿ect transistors (EGOFETs) as a replacement of conventional metal gate electrodes, using carbon nanotubes (CNTs) as a model carbon filler. Interestingly, the electrical properties of the resulting devices have been modulated by changing the loading percentage of CNTs within the insulating polymeric matrix. The potential of using such non-conventional gate electrodes for sensing purposes has also been evaluated by investigating, as a proof of concept, the formation of a supramolecular complex between a functionalized CNT-based NC-CPE containing ß-cyclodextrin (ß-CD) as a bio-recognition element and tryptophan (TRP). This approach, in synergism with the amplification function of an EGOFET, a¿ords a shift in the threshold voltage (VTH) of the transistor, giving promising analytical results with detection limits at picomolar levels (1.0 ± 0.1 pM) as well as a linear response from 10-12 to 10-9 M. Accordingly, NC-CPEs have been demonstrated to be a potential alternative to metal gate electrodes for the development of a new generation of highly sensitive carbon-based EGOFET bio-sensorsPostprint (published version

PS-b-P4VP block copolymer micelles as a soft template to grow openly porous nickel films for alkaline hydrogen evolution

Highly porous Ni films have been potentiostatically synthesised by micelle-assisted electrodeposition using custom-made PS-b-P4VP block copolymer micelles as a soft template. Two PS-b-P4VP block copolymers with PS/P4VP block ratios of 1:1 and 1:4 were used for the micelle-assisted electrodeposition, resulting in Ni films with large pores of diameters varying from 25 to 600 nm (1:1), and from 10 to 230 nm (1:4). As a result of the interconnected porosity, and hence the drastic increase of the surface-to-volume ratio, the electrocatalytic performance at hydrogen evolution reaction (HER) in alkaline media is significantly improved in comparison to a dense Ni film, and—more importantly—even in comparison to a highly mesoporous Ni film with monodisperse 10 nm wide pores. Most remarkably, it is discovered that the openly porous Ni electrocatalysts not only lead to a simple increase in HER current density, but also to a lower overpotential and a better long-term performance. While the bulk of the films is metallic, Ni(OH)2 is formed on the surfaces of all Ni films during HER. This effect leads to an initial decrease of the catalytic activity, but provides excellent stability in alkaline media. The presented synthesis process for pure Ni may be readily adopted to any other electroplatable metals and alloysThis work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101058076 and the Marie Skłodowska-Curie grant agreement No 764977. Additional funding was obtained from the Generalitat de Catalunya under project 2017-SGR-292 and the Spanish Government under PID2019–108794 GB-I00, PID2020–116844RB-C21, and associated FEDER Project. KE acknowledges the Spanish Ministerio de Uni- versidades for a Margarita Salas fellowship, financed by the European Union – NextGenerationEU. AGC acknowledges financial support from the Spanish Ministry of Science through the “Severo Ochoa” Programme for Centres of Excellence (FUNFUTURE, 2020–2023)Postprint (published version

Novel Zn(II) coordination polymers based on the natural molecule bisdemethoxycurcumin

This article introduces a new family of coordination polymers (CPs) that contains a renewable curcumin derivative, the bisdemethoxycurcumin (BDMC), coordinated to Zn(II) centers. The reaction between BDMC and zinc acetate, performed under mild conditions in ethanol, provides a new 1D phase termed BDMCZn-1. In addition, dimensionality and porosity of this network have been expanded by studying the reaction occurring between three species, the BDMC, the Zn(II), and a ditopic colinker: 1,2-bis(4-pyridyl)ethylene, 1,3-bis(4-pyridyl)propane, or 4,4′-bipyridine. In total, seven new CPs are presented, named BDMCZn-x. The structures of five of them were elucidated by single-crystal X-ray diffraction. Moreover, we show that the combination of the latest technique with solid-state 13C nuclear magnetic resonance is a powerful tool set to analyze the coordination modes of the BDMC, providing insight into the two unresolved structures. In the achievement of the new CPs, we further discuss the coordination capacity of BDMC, the relevance of solvents, and supramolecular interactions

Amperometric thyroxine sensor using a nanocomposite based on graphene modified with gold nanoparticles carrying a thiolated beta-cyclodextrin

This article reports a novel electrochemical sensor based on a nanocomposite for the sensitive determination of Thyroxine (T4), the active form of the hormone. Hydrodynamic amperometry is performed with a nanocomposite electrode based on the dispersion of a graphene–based filler hybrid-nanomaterial throughout an insulating epoxy resin in the optimum composition ratio (the near–percolation composition). This hybrid-nanomaterial consists of reduced graphene oxide tuned with gold nanoparticles and a biorecognition agent, the thiolated ß-cyclodextrin. Recognition of T4 is accomplished via supramolecular chemistry, due to the formation of an inclusion complex between ß-cyclodextrin and T4. The amperometric device operates at +0.85 V vs. Ag/AgCl, where the oxidation of T4 takes place on the electrode surface. The sensor covers the 1.00 nM to 14 nM T4concentration range in a 0.1 M HCl solution, with a detection limit of 1.00 ± 0.02 nM. The sensor can be easily reset by polishing. It exhibits the lowest detection limit regarding to any other electrochemical electrodes for T4 determination previously described in literaturePostprint (author's final draft

Cationic supramolecular hydrogels for overcoming the skin barrier in drug delivery

A cationic bis‐imidazolium‐based amphiphile was used to form thermoreversible nanostructured supramolecular hydrogels incorporating neutral and cationic drugs for the topical treatment of rosacea. The concentration of the gelator and the type and concentration of the drug incorporated were found to be factors that strongly influenced the gelling temperature, gel‐formation period, and overall stability and morphology. The incorporation of brimonidine tartrate resulted in the formation of the most homogeneous material of the three drugs explored, whereas the incorporation of betamethasone resulted in a gel with a completely different morphology comprising linked particles. NMR spectroscopy studies proved that these gels kept the drug not only at the interstitial space but also within the fibers. Due to the design of the gelator, drug release was up to 10 times faster and retention of the drug within the skin was up to 20 times more effective than that observed for commercial products. Experiments in vivo demonstrated the rapid efficacy of these gels in reducing erythema, especially in the case of the gel with brimonidine. The lack of coulombic attraction between the gelator-host and the guest-drug seemed particularly important in highly effective release, and the intermolecular interactions operating between them were found to lie at the root of the excellent properties of the materials for topical delivery and treatment of rosacea

Tuning Single-Molecule Conductance in Metalloporphyrin-Based Wires via Supramolecular Interactions.

Nature has developed amazing supramolecular constructs to deliver outstanding charge transport capabilities using metalloporphyrin-based supramolecular stacks.1 Here we are incorporating simple, naturally inspired supramolecular interactions via the axial complexation of metalloporphyrins into the formation of a single-molecule wire in a nanoscale gap to dissect the resulting electron pathways through the final chemical adduct. We observe that small structural changes in the axial coordinating linkers result in dramatic changes in the transport properties through the metalloporphyrin-based wire. The increased flexibility of a pyridine-4-yl-methanethiol ligand due to an extra methyl group as compared to a more rigid mercaptopyridine linker allows the former to adopt an unexpected highly conductive stacked structure between the two junction electrodes and the metalloporphyrin ring. DFT calculations reveal a molecular junction structure composed of a shifted stack of the three molecular backbones; the two pyridine ligands sandwiching the metalloporphyrin ring, which is stabilized by a combination of the porphyrin metal center coordinating the pyridinic N and the pyridine/porphyrin overlapping. Contrarily, the more rigid 4-mercaptopyridine ligand presents a more expected octahedral coordination of the metalloporphyrin metal center, leading to much lower conductance. Furthermore, we show that a mechanical forced imposed along the molecular wire axis results in a variety of more extended supramolecular structures between the pyridine linkers and the porphyrin ring spanning the tunneling gap and scoring relatively high conductance values. This works sets an example of the use of supramolecular chemistry in the construction of efficient molecular conduits towards the development of supramolecular electronics, a concept already exploited in natural organisms

Polysilicon-chromium-gold intracellular chips for multi-functional biomedical applications

The development of micro- and nanosystems for their use in biomedicine is a continuously growing field. One of the major goals of such platforms is to combine multiple functions in a single entity. However, achieving the design of an efficient and safe micro- or nanoplatform has shown to be strongly influenced by its interaction with the biological systems, where particle features or cell types play a critical role. In this work, the feasibility of using multi-material pSi-Cr-Au intracellular chips (MMICCs) for multifunctional applications by characterizing their interactions with two different cell lines, one tumorigenic and one non-tumorigenic, in terms of biocompatibility, internalization and intracellular fate, has been explored. Moreover, the impact of MMICCs on the induction of an inflammatory response has been assessed by evaluating TNFα, IL1b, IL6, and IL10 human inflammatory cytokines secretion by macrophages. Results show that MMICCs are biocompatible and their internalization efficiency is strongly dependent on the cell type. Finally as a proof-of-concept, MMICCs have been dually functionalized with transferrin and pHrodo™ Red, SE to target cancer cells and detect intracellular pH, respectively. In conclusion, MMICCs can be used as multi-functional devices due to their high biocompatibility, non-inflammatory properties and the ability of developing multiple functions