Photoswitchable Fluorescent Crystals Obtained by the Photoreversible Coassembly of a Nucleobase and an Azobenzene Intercalator.
Zhou Li,Retailleau Pascal,Morel Mathieu,Rudiuk Sergii,Baigl Damien
Journal of the American Chemical Society
Self-assembled nucleobases, such as G-quartets or quadruplexes, have numerous applications, but light-responsive structures are limited to small, noncrystalline motifs. In addition, the assembly of the widely exploited azobenzene photochromic compounds can produce fluorescent crystals of extended dimensions but at the prize of sacrificing their photoswitchability. Here, we overcome inherent limitations of self-assembly with a new concept of supramolecular coassembly leading to materials with unprecedented properties. We show that the coassembly of guanosine monophosphate (GMP) with an azobenzene-containing DNA intercalator produces supramolecular crystals arranged through a combination of π-π, electrostatic, and hydrogen-bond interactions. The resulting crystals are 100 μm long, pH-sensitive, fluorescent, and can be photoreversibly disassembled/reassembled upon UV/blue irradiation. This allows us to perform operations such as dynamic photocontrol of a single-crystal growth, light-gated permeability in membrane-like materials, and photoswitchable fluorescence. We believe this concept critically expands the breadth of multifunctional materials attainable by self-assembly.
10.1021/jacs.9b02836
Light-enhanced liquid-phase exfoliation and current photoswitching in graphene-azobenzene composites.
Döbbelin Markus,Ciesielski Artur,Haar Sébastien,Osella Silvio,Bruna Matteo,Minoia Andrea,Grisanti Luca,Mosciatti Thomas,Richard Fanny,Prasetyanto Eko Adi,De Cola Luisa,Palermo Vincenzo,Mazzaro Raffaello,Morandi Vittorio,Lazzaroni Roberto,Ferrari Andrea C,Beljonne David,Samorì Paolo
Nature communications
Multifunctional materials can be engineered by combining multiple chemical components, each conferring a well-defined function to the ensemble. Graphene is at the centre of an ever-growing research effort due to its combination of unique properties. Here we show that the large conformational change associated with the trans-cis photochemical isomerization of alkyl-substituted azobenzenes can be used to improve the efficiency of liquid-phase exfoliation of graphite, with the photochromic molecules acting as dispersion-stabilizing agents. We also demonstrate reversible photo-modulated current in two-terminal devices based on graphene-azobenzene composites. We assign this tuneable electrical characteristics to the intercalation of the azobenzene between adjacent graphene layers and the resulting increase in the interlayer distance on (photo)switching from the linear trans-form to the bulky cis-form of the photochromes. These findings pave the way to the development of new optically controlled memories for light-assisted programming and high-sensitive photosensors.
10.1038/ncomms11090
Ultrafast isomerization-induced cooperative motions to higher molecular orientation in smectic liquid-crystalline azobenzene molecules.
Nature communications
The photoisomerization of molecules is widely used to control the structure of soft matter in both natural and synthetic systems. However, the structural dynamics of the molecules during isomerization and their subsequent response are difficult to elucidate due to their complex and ultrafast nature. Herein, we describe the ultrafast formation of higher-orientation of liquid-crystalline (LC) azobenzene molecules via linearly polarized ultraviolet light (UV) using ultrafast time-resolved electron diffraction. The ultrafast orientation is caused by the trans-to-cis isomerization of the azobenzene molecules. Our observations are consistent with simplified molecular dynamics calculations that revealed that the molecules are aligned with the laser polarization axis by their cooperative motion after photoisomerization. This insight advances the fundamental chemistry of photoresponsive molecules in soft matter as well as their ultrafast photomechanical applications.
10.1038/s41467-019-12116-6
Photoresponsive switches at surfaces based on supramolecular functionalization with azobenzene-oligoglycerol conjugates.
Nachtigall Olaf,Kördel Christian,Urner Leonhard H,Haag Rainer
Angewandte Chemie (International ed. in English)
The synthesis, supramolecular complexation, and switching of new bifunctional azobenzene-oligoglycerol conjugates in different environments is reported. Through the formation of host-guest complexes with surface immobilized β-cyclodextrin receptors, the bifunctional switches were coupled to gold surfaces. The isomerization of the amphiphilic azobenzene derivatives was examined in solution, on gold nanoparticles, and on planar gold surfaces. The wettability of functionalized gold surfaces can be reversibly switched under light-illumination with two different wavelengths. Besides the photoisomerization processes and concomitant effects on functionality, the thermal cis to trans isomerization of the conjugates and their complexes was monitored. Thermal half-lives of the cis isomers were calculated for different environments. Surprisingly, the half-lives on gold nanoparticles were significantly smaller compared to planar gold surfaces.
10.1002/anie.201403331
Azobenzene-Equipped Covalent Organic Framework: Light-Operated Reservoir.
Das Gobinda,Prakasam Thirumurugan,Addicoat Matthew A,Sharma Sudhir Kumar,Ravaux Florent,Mathew Renny,Baias Maria,Jagannathan Ramesh,Olson Mark A,Trabolsi Ali
Journal of the American Chemical Society
Light-operated materials have gained significant attention for their potential technological importance. To achieve molecular motion within extended networks, stimuli-responsive units require free space. The majority of the so far reported 2D-extended organic networks with responsive moieties restrict their freedom of motion on account of their connectivity providing constrained free volume for efficient molecular motion. We report here a light-responsive azobenzene-functionalized covalent organic framework (TTA-AzoDFP) designed in a way that the pendent azobenzene groups are pointing toward the pore channels with sufficient free volume necessary for the unencumbered dynamic motion to occur inside the pores of the covalent organic framework (COF) and undergo a reversible - photoisomerization upon light irradiation. The resulting hydrophobic COF was used for the storage of rhodamine B and its controlled release in solution by the mechanical motion of the azobenzene units triggered by ultraviolet-light irradiation. The TTA-AzoDFP displayed unprecedented photoregulated fluorescence emission behavior upon UV-light irradiation. Size, emission, and degree of hydrophobicity with respect to photoisomerization could be reversibly controlled by alternating UV- and visible-light exposure. The results reported here demonstrate once again the importance of the careful design of the linkers not only to allow the incorporation of molecular switches within the chemical structure of COFs but also to provide the required free space for not hindering their motion. The results demonstrate that responsive COFs could be suitable platforms for delivery systems that can be controlled by external stimuli.
10.1021/jacs.9b09643
Photoinduced reversible switching of porosity in molecular crystals based on star-shaped azobenzene tetramers.
Baroncini Massimo,d'Agostino Simone,Bergamini Giacomo,Ceroni Paola,Comotti Angiolina,Sozzani Piero,Bassanetti Irene,Grepioni Fabrizia,Hernandez Taylor M,Silvi Serena,Venturi Margherita,Credi Alberto
Nature chemistry
The development of solid materials that can be reversibly interconverted by light between forms with different physico-chemical properties is of great interest for separation, catalysis, optoelectronics, holography, mechanical actuation and solar energy conversion. Here, we describe a series of shape-persistent azobenzene tetramers that form porous molecular crystals in their E-configuration, the porosity of which can be tuned by changing the peripheral substituents on the molecule. Efficient E→Z photoisomerization of the azobenzene units takes place in the solid state and converts the crystals into a non-porous amorphous melt phase. Crystallinity and porosity are restored upon Z→E isomerization promoted by visible light irradiation or heating. We demonstrate that the photoisomerization enables reversible on/off switching of optical properties such as birefringence as well as the capture of CO2 from the gas phase. The linear design, structural versatility and synthetic accessibility make this new family of materials potentially interesting for technological applications.
10.1038/nchem.2304
Supramolecular Control of Azobenzene Switching on Nanoparticles.
Chu Zonglin,Han Yanxiao,Bian Tong,De Soumen,Král Petr,Klajn Rafal
Journal of the American Chemical Society
The reversible photoisomerization of azobenzene has been utilized to construct a plethora of systems in which optical, electronic, catalytic, and other properties can be controlled by light. However, owing to azobenzene's hydrophobic nature, most of these examples have been realized only in organic solvents, and systems operating in water are relatively scarce. Here, we show that by coadsorbing the inherently hydrophobic azobenzenes with water-solubilizing ligands on the same nanoparticulate platforms, it is possible to render them essentially water-soluble. To this end, we developed a modified nanoparticle functionalization procedure allowing us to precisely fine-tune the amount of azobenzene on the functionalized nanoparticles. Molecular dynamics simulations helped us to identify two distinct supramolecular architectures (depending on the length of the background ligand) on these nanoparticles, which can explain their excellent aqueous solubilities. Azobenzenes adsorbed on these water-soluble nanoparticles exhibit highly reversible photoisomerization upon exposure to UV and visible light. Importantly, the mixed-monolayer approach allowed us to systematically investigate how the background ligand affects the switching properties of azobenzene. We found that the nature of the background ligand has a profound effect on the kinetics of azobenzene switching. For example, a hydroxy-terminated background ligand is capable of accelerating the back-isomerization reaction by more than 6000-fold. These results pave the way toward the development of novel light-responsive nanomaterials operating in aqueous media and, in the long run, in biological environments.
10.1021/jacs.8b09638
Dynamic actuation of glassy polymersomes through isomerization of a single azobenzene unit at the block copolymer interface.
Molla Mijanur Rahaman,Rangadurai Poornima,Antony Lucas,Swaminathan Subramani,de Pablo Juan J,Thayumanavan S
Nature chemistry
Nature has engineered exquisitely responsive systems where molecular-scale information is transferred across an interface and propagated over long length scales. Such systems rely on multiple interacting, signalling and adaptable molecular and supramolecular networks that are built on dynamic, non-equilibrium structures. Comparable synthetic systems are still in their infancy. Here, we demonstrate that the light-induced actuation of a molecularly thin interfacial layer, assembled from a hydrophilic- azobenzene -hydrophobic diblock copolymer, can result in a reversible, long-lived perturbation of a robust glassy membrane across a range of over 500 chemical bonds. We show that the out-of-equilibrium actuation is caused by the photochemical trans-cis isomerization of the azo group, a single chemical functionality, in the middle of the interfacial layer. The principles proposed here are implemented in water-dispersed nanocapsules, and have implications for on-demand release of embedded cargo molecules.
10.1038/s41557-018-0027-6
Crystalline Nanochannels with Pendant Azobenzene Groups: Steric or Polar Effects on Gas Adsorption and Diffusion?
Huang Hubiao,Sato Hiroshi,Aida Takuzo
Journal of the American Chemical Society
An azobenzene-containing, zirconium-based metal-organic framework (MOF), upon irradiation with ultraviolet (UV) light at 365 ± 10 nm, underwent trans-to-cis isomerization of its azobenzene pendants to furnish the cis-isomer content of 21% (MOF) in 30 min at the photostationary state and underwent backward isomerization into MOF upon either irradiation with visible light (420-480 nm) or heating. When the cis-isomer content increased, the diffusion rate and amount of CO adsorbed into the nanochannels of MOF decreased considerably. When erythrosine B, a polarity-probing guest, was used, it showed a red shift upon exposure of MOF⊃EB to visible light, indicating that the interior environment of MOF turns less polar as the trans-isomer content becomes higher. In sharp contrast, the adsorption profiles of MOF and MOF for Ar having an analogous kinetic diameter to CO but no quadrupole moment and a smaller polarizability were virtually identical to one another. Therefore, it is likely that CO experiences a dominant effect of a polar effect rather than a steric effect in the crystalline nanochannels.
10.1021/jacs.7b02979
Atomic/Molecular Layer Deposited Iron-Azobenzene Framework Thin Films for Stimuli-Induced Gas Molecule Capture/Release.
Khayyami Aida,Philip Anish,Karppinen Maarit
Angewandte Chemie (International ed. in English)
The atomic/molecular layer deposition (ALD/MLD) technique provides an elegant way to grow crystalline metal-azobenzene thin films directly from gaseous precursors; the photoactive azobenzene linkers thus form an integral part of the crystal framework. Reversible water capture/release behavior for these thin films can be triggered through the trans-cis photoisomerization reaction of the azobenzene moieties in the structure. The ALD/MLD approach could open up new horizons for example, for the emerging fields of remotely controlled drug delivery and gas storage.
10.1002/anie.201908164
Athermal Azobenzene-Based Nanoimprint Lithography.
Probst Christian,Meichner Christoph,Kreger Klaus,Kador Lothar,Neuber Christian,Schmidt Hans-Werner
Advanced materials (Deerfield Beach, Fla.)
A novel nanoimprint lithography technique based on the photofluidization effect of azobenzene materials is presented. The tunable process allows for imprinting under ambient conditions without crosslinking reactions, so that shrinkage of the resist is avoided. Patterning of surfaces in the regime from micrometers down to 100 nm is demonstrated.
10.1002/adma.201505552
Tunable Photocontrolled Motions Using Stored Strain Energy in Malleable Azobenzene Liquid Crystalline Polymer Actuators.
Lu Xili,Guo Shengwei,Tong Xia,Xia Hesheng,Zhao Yue
Advanced materials (Deerfield Beach, Fla.)
A new strategy for enhancing the photoinduced mechanical force is demonstrated using a reprocessable azobenzene-containing liquid crystalline network (LCN). The basic idea is to store mechanical strain energy in the polymer beforehand so that UV light can then be used to generate a mechanical force not only from the direct light to mechanical energy conversion upon the trans-cis photoisomerization of azobenzene mesogens but also from the light-triggered release of the prestored strain energy. It is shown that the two mechanisms can add up to result in unprecedented photoindued mechanical force. Together with the malleability of the polymer stemming from the use of dynamic covalent bonds for chain crosslinking, large-size polymer photoactuators in the form of wheels or spring-like "motors" can be constructed, and, by adjusting the amount of prestored strain energy in the polymer, a variety of robust, light-driven motions with tunable rolling or moving direction and speed can be achieved. The approach of prestoring a controllable amount of strain energy to obtain a strong and tunable photoinduced mechanical force in azobenzene LCN can be further explored for applications of light-driven polymer actuators.
10.1002/adma.201606467
Mechanized azobenzene-functionalized zirconium metal-organic framework for on-command cargo release.
Science advances
Stimuli-responsive metal-organic frameworks (MOFs) have gained increasing attention recently for their potential applications in many areas. We report the design and synthesis of a water-stable zirconium MOF (Zr-MOF) that bears photoresponsive azobenzene groups. This particular MOF can be used as a reservoir for storage of cargo in water, and the cargo-loaded MOF can be further capped to construct a mechanized MOF through the binding of β-cyclodextrin with the azobenzene stalks on the MOF surface. The resulting mechanized MOF has shown on-command cargo release triggered by ultraviolet irradiation or addition of competitive agents without premature release. This study represents a simple approach to the construction of stimuli-responsive mechanized MOFs, and considering mechanized UiO-68-azo made from biocompatible components, this smart system may provide a unique MOF platform for on-command drug delivery in the future.
10.1126/sciadv.1600480
Direct Fabrication of Micro/Nano-Patterned Surfaces by Vertical-Directional Photofluidization of Azobenzene Materials.
Choi Jaeho,Cho Wonhee,Jung Yeon Sik,Kang Hong Suk,Kim Hee-Tak
ACS nano
Anisotropic movement of azobenzene materials (i.e., azobenzene molecules incorporated in polymer, glass, or supramolecules) has provided significant opportunities for the fabrication of micro/nanoarchitectures. The examples include circular holes, line gaps, ellipsoidal holes, and nanofunnels. However, all of the previous studies have only focused on the lateral directional movement for the structural shaping of azobenzene materials. Herein, we propose structural shaping based on a vertical directional movement of azobenzene materials. To do this, light with oblique incidence, containing normal direction light polarization, was illuminated onto azobenzene materials film contact with patterned elastomeric molds (i.e., PDMS) so that the resulting vertical directional movement of azobenzene materials fills in the cavities of the molds and results in pattern formation. As a result, a range of patterns with sizes of features from micro- to sub-100 nm scale was successfully fabricated in a large area (few cm), and the structural height was deterministically controlled by simply adjusting irradiation time. In addition to the notable capability of fabricating the single-scale structures, the technique provides a facile way to fabricate complex hierarchical multiscale structures, ensuring its versatility and wide applicability to various applications. As a selected exemplary application of the multiscale structures, a superhydrophobic surface has been successfully demonstrated.
10.1021/acsnano.6b05934
Controlled Sol-Gel Transitions of a Thermoresponsive Polymer in a Photoswitchable Azobenzene Ionic Liquid as a Molecular Trigger.
Wang Caihong,Hashimoto Kei,Tamate Ryota,Kokubo Hisashi,Watanabe Masayoshi
Angewandte Chemie (International ed. in English)
Producing ionic liquids (ILs) that function as molecular trigger for macroscopic change is a challenging issue. Photoisomerization of an azobenzene IL at the molecular level evokes a macroscopic response (light-controlled mechanical sol-gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2-phenylethyl methacrylate), show a lower critical solution temperature in the IL mixture containing azobenzene, while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, different gelation temperatures were observed in it under dark and UV conditions. Light-controlled sol-gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self-assembly of a thermoresponsive polymer, leading to macroscopic light-controlled sol-gel transitions.
10.1002/anie.201710288