Catechols are found in nature taking part in a remarkably broad scope of biochemical processes and functions. Though not exclusively, such versatility may be traced back to several properties ...uniquely found together in the o‐dihydroxyaryl chemical function; namely, its ability to establish reversible equilibria at moderate redox potentials and pHs and to irreversibly cross‐link through complex oxidation mechanisms; its excellent chelating properties, greatly exemplified by, but by no means exclusive, to the binding of Fe3+; and the diverse modes of interaction of the vicinal hydroxyl groups with all kinds of surfaces of remarkably different chemical and physical nature. Thanks to this diversity, catechols can be found either as simple molecular systems, forming part of supramolacular structures, coordinated to different metal ions or as macromolecules mostly arising from polymerization mechanisms through covalent bonds. Such versatility has allowed catechols to participate in several natural processes and functions that range from the adhesive properties of marine organisms to the storage of some transition metal ions.
As a result of such an astonishing range of functionalities, catechol‐based systems have in recent years been subject to intense research, aimed at mimicking these natural systems in order to develop new functional materials and coatings. A comprehensive review of these studies is discussed in this paper.
Catechols participate in several natural processes and functions that range from the adhesive properties of marine organisms to the storage of certain metals ions. Accordingly, many scientists worldwide have been studying and mimicking these natural systems to develop new active materials and coatings. A detailed revision of a wide variety of relevant studies in this field is discussed in this Review.
Herein, a versatile threshold temperature sensor based on the glass transition temperature‐triggered fluorescence activation of a dye/developer duo, encapsulated in polymeric nanoparticles is ...reported. The emission enhancement, detectable even by unaided eye is completed within a narrow temperature range and activates at adjustable threshold temperatures up to 200 °C. Fluorescence is chosen as sensing probe due to its high detection sensitivity together with an advanced spatial and temporal resolution. The strategy is based on nanoparticles prepared from standard thermoplastic polymers, a fluorescence developer, and the commercially available Rhodamine B base dye, a well‐known and widely used fluorescent molecule. By making nanoparticles of different thermoplastic polymers, fast, abrupt, and irreversible disaggregation induced fluorescence enhancement, with tunable threshold temperature depending on the nanoparticles polymer glass transition is achieved. As a proof‐of‐concept for the versatility of this novel family of NPs, their use for sensing the thermal history of environments and surfaces exposed to the threshold temperature is showed.
Fluorescent high‐temperature threshold sensors, based on polymeric nanoparticles containing Rhodamine B and dodecanoic acid, are obtained. These sensors are easily prepared to selectively detect threshold temperatures in the range of 90–200 °C, by simply changing the constituent polymer. The irreversible fluorescence enhancement is high enough to be detectable by unaided eye.
A novel strategy to achieve thermally switchable photochromism in solid materials is reported, which relies on the preparation of polymeric core–shell capsules containing solutions of photochromic ...dyes in acidic phase‐change materials. Upon changing the phase (solid or liquid) of the encapsulated medium, one of the two photochromic states of the system is selectively stabilized on demand, allowing for reversible interconversion between direct and reverse photochromism when thermally scanning through the melting temperature of the phase‐change material. This strategy, which does not require the addition of external agents or chemical modification of the dyes, proved to be general for different spiropyran photochromes and to be applicable to the fabrication of a variety of functional materials by simply embedding the capsules obtained into a solid matrix of choice.
Positive or negative: Solid composites with switchable positive/negative photochromism were obtained by embedding core–shell microcapsules containing photochromic solutions of spiropyran dyes in acidic phase‐change media in polymeric matrices. The photochromism of these materials could be switched by inducing the melting/solidification of the encapsulated medium through a change in temperature.
A facile one‐step polymerization strategy is explored to achieve novel catechol‐based materials. Depending on the functionality of the catechol, the as‐prepared product can be used to modify at will ...the surface tension of nano and bulk structures, from oleo‐/hydrophobic to highly hydrophilic. A hydrophobic catechol prepared thus polymerized shows the ability to self‐assemble as solid nanoparticles with sticky properties in polar solvent media. Such a versatile concept is ideal for the development of catechol‐based multifunctional materials.
To date, crystallization studies conducted in space laboratories, which are prohibitively costly and unsuitable to most research laboratories, have shown the valuable effects of microgravity during ...crystal growth and morphogenesis. Herein, an easy and highly efficient method is shown to achieve space‐like experimentation conditions on Earth employing custom‐made microfluidic devices to fabricate 2D porous crystalline molecular frameworks. It is confirmed that experimentation under these simulated microgravity conditions has unprecedented effects on the orientation, compactness and crack‐free generation of 2D porous crystalline molecular frameworks as well as in their integration and crystal morphogenesis. It is believed that this work will provide a new “playground” to chemists, physicists, and materials scientists that desire to process unprecedented 2D functional materials and devices.
How to achieve simulated microgravity conditions on Earth? The art of growing and processing 2D porous crystalline molecular frameworks in simulated microgravity is presented.
A high‐content screening method to characterize multifunctional multilayer films that combine mechanical adhesion and favorable biological response is reported. Distinct combinations of ...nanostructured films are produced using layer‐by‐layer methodology and their morphological, physicochemical, and biological properties are analyzed in a single microarray chip. Inspired by the composition of the adhesive proteins in mussels, thin films containing dopamine‐modified hyaluronic acid are studied. Flat biomimetic superhydrophobic patterned chips produced by a bench‐top methodology are used for the build‐up of arrays of multilayer films. The wettability contrasts imprinted onto the chips are allowed to produce individual, position controlled, multilayer films in the wettable regions. The flat configuration of the chip permits to perform a series of nondestructive measurements directly on the individual spots. In situ adhesion properties are directly measured in each spot, showing that nanostructured films richer in dopamine promote the adhesion. In vitro tests show an enhanced cell adhesion for the films with more catechol groups. The advantages presented by this platform include ability to control the uniformity and size of the multilayers films, its suitability to be used as a new low cost toolbox and for high‐content cellular screening, and capability for monitoring in situ a variety of distinct material properties.
Inspired by the structure of mussel adhesive proteins, layer‐by‐layer coatings are developed. Many combinations of multilayers films are individually disposed on isolated transparent spots, patterned onto biomimetic superhydrophobic substrates. The adhesion properties of the coatings are analyzed in a high‐throughput way. In vitro tests are carried out to evaluate the biological performance of the multilayer films that can be useful in distinct biomedical applications.
Even though thermofluorochromic materials are eternal candidates for their use in multiple applications, they are still limited as they require complex synthetic strategies to accomplish tunable ...optical properties and/or provide optical changes only over a very wide temperature range. By taking advantage of the high sensitivity of the optical properties of conjugated polymers and oligomers to the external environment, herein phase change material (PCM)‐based thermofluorochromic mixtures are created, where the solid‐to‐liquid transition of the PCM host triggers a sharp fluorescence color change of the dispersed polymers/oligomers. Fluorophore conjugation length, concentration, and PCM nature can be used to vary the spectral properties of the resulting materials along the visible region, covering a large part of the CIE 1931 color space. For the preparation of functional devices, this behavior can be directly transferred to the solid state by soaking or printing cellulose papers with the obtained thermofluorochromic mixtures as well as by structuring them into solid lipid particles that can be dispersed within polymer matrices. The resulting materials show very promising features as thermal sensors and anticounterfeiting labels.
Polymer composite and cellulose papers with thermofluorochromic properties are obtained from easily prepared bulk and microstructured mixtures of phase‐change material and conjugated polymers and oligomers, which offer broad and straightforward tunability of the fluorescence emission all over the visible spectral region.
Pathogenic bacteria pose a significant threat to human health, and their removal from food and water supplies is crucial in preventing the spread of waterborne and foodborne diseases. Recently, ...silver‐based photocatalytic micromotors have emerged as promising candidates for inactivating pathogenic microbes due to their high antibacterial activity. In this study, the synthesis of photoactive Ag3PO4 micromotors with a well‐defined tetrapod‐like structure (TAMs) is presented using a simple precipitation method. These TAMs autonomously move and release Ag ions/nanoparticles (NPs) through a photodegradation process when exposed to light, which enhances their antimicrobial activity against Gram‐negative (Escherichia coli) and Gram‐positive (Staphylococcus aureus) bacterial strains. Interestingly, different motion modes are observed under different manipulated light wavelengths and fuels. Furthermore, the self‐degradation of TAMs is accelerated in the presence of negatively charged bacteria, which results in higher removal rates of both bacteria, E. Coli and S. aureus. The findings introduce a new concept of self‐degradable micromotors based on photocatalytic components, which hold great potential for their use in antimicrobial applications. This work offers significant implications for materials chemistry, especially in designing and developing the next generation of light‐driven antimicrobial agents.
Tetrapod‐shaped micromotors able to self‐propel under light irradiation, disintegrate, and release silver nanoparticles are fabricated. Due to their unique morphology and light interactions, these photoactive micromotors can efficiently inactivate different types of bacteria by an enhanced contact mechanism. The photogeneration of reactive oxygen species by the micromotors is also found to play a key role in their photoactivity.
Off/on, on/off, and on1/on2 fluorescence switching systems find application in a variety of areas, for each of which a particular dye or dye‐switch tether must be specifically designed and ...synthesized. Herein it is demonstrated that such tight requirement can be avoided by using easily prepared mixtures of readily available emitters and phase change materials (PCMs). By proper selection of the PCM and, if needed, additives, thermo‐ and photothermoresponsive materials showing all classes of emission switching modes can be prepared from a single dye and without chemical modifications. This strategy can be generalized to distinct emitters and, thanks to the facile and versatile printability of dye–PCM mixtures, it can be used for the fabrication of fluorescent patterns showing complex (photo)thermal responses with direct applicability in sensing and anti‐counterfeiting.
Bulk and nanostructured phase change materials (PCMs) are used to modulate the fluorescence properties of a perylene diimide derivative, upon temperature‐induced phase transition. By suitably selecting the PCM type and additives allowing for photoinduced electron quenching, it is possible to achieve straightforwardly solid materials manifesting the three possible fluorescence modulation modes, using the same dye: off/on, on/off, and on1/on2.
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