Light driven mesoscale assembly of a coordination polymeric gelator into flowers and stars with distinct properties.
Chemical science
Control over the self-assembly process of porous organic-inorganic hybrids often leads to unprecedented polymorphism and properties. Herein we demonstrate how light can be a powerful tool to intervene in the kinetically controlled mesoscale self-assembly of a coordination polymeric gelator. Ultraviolet light induced coordination modulation photoisomerisation of an azobenzene based dicarboxylate linker followed by aggregation mediated crystal growth resulted in two distinct morphological forms (flowers and stars), which show subtle differences in their physical properties.
10.1039/c5sc02233a
Photo-Reconfigurable Azopolymer Etch Mask: Photofluidization-Driven Reconfiguration and Edge Rectangularization.
Choi Jaeho,Kang Hong Suk,Jo Wonhee,Kim Shin-Hyun,Jung Yeon Sik,Kim Hee-Tak
Small (Weinheim an der Bergstrasse, Germany)
Directional photofluidization of azobenzene materials has provided unprecedented opportunities for the structural reconfiguration of circular holes, line gaps, ellipsoidal holes, and nanofunnel-shaped micro/nanoarchitectures. However, all the reconfigured structures have a parabolic or round wall due to the tendency of the photofluidized azobenezene materials to minimize the surface area, which limits their use as a reconfigurable etch-mask for the lithography process. In this work, a simple method is presented that can change the round walls of azopolymer architectures into rectangular walls, which is named rectangularization. By irradiating far-field light on reconfigured azopolymer in a conformal contact with a flat polydimethylsiloxane (PDMS) film, the round wall transforms to a rectangular one because the azopolymer adheres along the PDMS surface while being photofluidized. As a result, the rectangularization process creates a variety of structural features and sizes ranging from a few micrometers to 150 nm having a rectangular wall. By exploiting the rectangularization process, the concept of a photo-reconfigurable etch mask is achieved, which transfers the mask patterns to a silicon pattern with a high structural fidelity and imparts a considerable flexibility to the lithography process.
10.1002/smll.201703250
Gold Nanoparticles Thin Films with Thermo- and Photoresponsive Plasmonic Properties Realized with Liquid-Crystalline Ligands.
Tomczyk Ewelina,Promiński Aleksander,Bagiński Maciej,Górecka Ewa,Wójcik Michał
Small (Weinheim an der Bergstrasse, Germany)
Robust synthesis of large-scale self-assembled nanostructures with long-range organization and a prominent response to external stimuli is critical to their application in functional plasmonics. Here, the first example of a material made of liquid crystalline nanoparticles which exhibits UV-light responsive surface plasmon resonance in a condensed state is presented. To obtain the material, metal cores are grafted with two types of organic ligands. A promesogenic derivative softens the system and induces rich liquid crystal phase polymorphism. Second, an azobenzene derivative endows nanoparticles with photoresponsive properties. It is shown that nanoparticles covered with a mixture of these ligands assemble into long-range ordered structures which exhibit a novel dual-responsivity. The structure and plasmonic properties of the assemblies can be controlled by a change in temperature as well as by UV-light irradiation. These results present an efficient way to obtain bulk quantities of self-assembled nanostructured materials with stability that is unattainable by alternative methods such as matrix-assisted or DNA-mediated organization.
10.1002/smll.201902807
Light-induced unfolding and refolding of supramolecular polymer nanofibres.
Adhikari Bimalendu,Yamada Yuki,Yamauchi Mitsuaki,Wakita Kengo,Lin Xu,Aratsu Keisuke,Ohba Tomonori,Karatsu Takashi,Hollamby Martin J,Shimizu Nobutaka,Takagi Hideaki,Haruki Rie,Adachi Shin-Ichi,Yagai Shiki
Nature communications
Unlike classical covalent polymers, one-dimensionally (1D) elongated supramolecular polymers (SPs) can be encoded with high degrees of internal order by the cooperative aggregation of molecular subunits, which endows these SPs with extraordinary properties and functions. However, this internal order has not yet been exploited to generate and dynamically control well-defined higher-order (secondary) conformations of the SP backbone, which may induce functionality that is comparable to protein folding/unfolding. Herein, we report light-induced conformational changes of SPs based on the 1D exotic stacking of hydrogen-bonded azobenzene hexamers. The stacking causes a unique internal order that leads to spontaneous curvature, which allows accessing conformations that range from randomly folded to helically folded coils. The reversible photoisomerization of the azobenzene moiety destroys or recovers the curvature of the main chain, which demonstrates external control over the SP conformation that may ultimately lead to biological functions.
10.1038/ncomms15254
Tunable molecular separation by nanoporous membranes.
Wang Zhengbang,Knebel Alexander,Grosjean Sylvain,Wagner Danny,Bräse Stefan,Wöll Christof,Caro Jürgen,Heinke Lars
Nature communications
Metal-organic frameworks offer tremendous potential for efficient separation of molecular mixtures. Different pore sizes and suitable functionalizations of the framework allow for an adjustment of the static selectivity. Here we report membranes which offer dynamic control of the selectivity by remote signals, thus enabling a continuous adjustment of the permeate flux. This is realized by assembling linkers containing photoresponsive azobenzene-side-groups into monolithic, crystalline membranes of metal-organic frameworks. The azobenzene moieties can be switched from the trans to the cis configuration and vice versa by irradiation with ultraviolet or visible light, resulting in a substantial modification of the membrane permeability and separation factor. The precise control of the cis:trans azobenzene ratio, for example, by controlled irradiation times or by simultaneous irradiation with ultraviolet and visible light, enables the continuous tuning of the separation. For hydrogen:carbon-dioxide, the separation factor of this smart membrane can be steplessly adjusted between 3 and 8.
10.1038/ncomms13872
Side-group chemical gating via reversible optical and electric control in a single molecule transistor.
Meng Linan,Xin Na,Hu Chen,Wang Jinying,Gui Bo,Shi Junjie,Wang Cheng,Shen Cheng,Zhang Guangyu,Guo Hong,Meng Sheng,Guo Xuefeng
Nature communications
By taking advantage of large changes in geometric and electronic structure during the reversible trans-cis isomerisation, azobenzene derivatives have been widely studied for potential applications in information processing and digital storage devices. Here we report an unusual discovery of unambiguous conductance switching upon light and electric field-induced isomerisation of azobenzene in a robust single-molecule electronic device for the first time. Both experimental and theoretical data consistently demonstrate that the azobenzene sidegroup serves as a viable chemical gate controlled by electric field, which efficiently modulates the energy difference of trans and cis forms as well as the energy barrier of isomerisation. In conjunction with photoinduced switching at low biases, these results afford a chemically-gateable, fully-reversible, two-mode, single-molecule transistor, offering a fresh perspective for creating future multifunctional single-molecule optoelectronic devices in a practical way.
10.1038/s41467-019-09120-1
Stomata-Inspired Photomechanical Ion Nanochannels Modified by Azobenzene Composites.
Chun Kyoung-Yong,Son Young Jun,Jo Sunghwan,Han Chang-Soo
Small (Weinheim an der Bergstrasse, Germany)
A low-powered and highly selective photomechanical sensor system mimicking stomata in the epidermis of leaves harvested from nature is demonstrated. This device uses a light-responsive composite consisting of 4-amino-1,1'-azobenzene-3,4'-disulfonic acid monosodium salt (AZO) and poly(diallyldimethylammonium chloride) (PDDA) coated on a membrane with tens of nanometer-size pores. The ionic current change through the pore channels as a function of pore size variation is then measured. The tran-cis isomerism of AZO-PDDA during light irradiation and the operation mechanism of photomechanical ion channel sensor are discussed and analyzed using UV-vis spectroscopy and atomic force microscopy analysis. It presents the discriminative current levels to the different light wavelengths. The response time of the photoreceptor is about 0.2 s and it consumes very low operating power (≈15 nW) at 0.1 V bias. In addition, it is found that the change of the pore diameter during the light irradiation is due to the photomechanical effect, which is capable of distinguishing light intensity and wavelength.
10.1002/smll.201703618
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
Alignment Control of Nematic Liquid Crystal using Gold Nanoparticles Grafted by the Liquid Crystalline Polymer with Azobenzene Mesogens as the Side Chains.
Kuang Ze-Yang,Fan Yao-Jian,Tao Lei,Li Ming-Li,Zhao Nie,Wang Ping,Chen Er-Qiang,Fan Fan,Xie He-Lou
ACS applied materials & interfaces
The gold nanoparticles highly grafted by a liquid crystalline polymer (LCP) with azobenzene mesogens as the side chain (denoted as Au@TE-PAzo NPs) are successfully designed and synthesized by the two-phase Brust-Schiffrin method. The chemical structures of the monomer and polymer ligands have been confirmed by nuclear magnetic resonance, and the molecular weight of the polymer is determined by gel permeation chromatography. The combined analysis of transmission electron microscopy and thermogravimetric analysis shows that the size of the nanoparticles is 2.5(±0.4) nm and the content of the gold in the Au@TE-PAzo NPs is ca. 17.58%. The resultant Au@TE-PAzo NPs can well disperse in the nematic LC of 5CB. The well-dispersed mixture with appropriate doping concentrations can automatically form a perfect homeotropic alignment in the LC cell. The homeotropic alignment is attributed to the brush formed by Au@TE-PAzo NPs on the substrate, wherein the Au@TE-PAzo NPs gradually diffuse onto the substrate from the mixture. On the contrary, the pure side chain LCPs cannot yield vertical alignment of 5CB, which indicates that the alignment of 5CB is ascribed to the synergistic interaction of the nanoparticles and the grafted LCPs. Moreover, Au@TE-PAzo NPs show excellent film-forming property on account of their periphery of high densely grafted LCPs, which can form uniform thin film by spin-coating. The resultant thin film also can prompt the automatical vertical alignment of the nematic 5CB. Further, upon alternative irradiation of UV and visible light, the alignment of 5CB reversibly switches between vertical and random orientation because of the trans-cis photoisomerization of the azobenzene group on the periphery of Au@TE-PAzo NPs. These experimental results suggest that this kind of nanoparticles can be potentially applied in constructing the remote-controllable optical devices.
10.1021/acsami.8b07483
Chemiluminescence-initiated and -enhanced photoisomerization for tissue-depth-independent photo-controlled drug release.
Chemical science
Tissue-penetration-depth-independent self-luminescence is highly expected to perform photoisomerization-related bioapplications to overcome the limitation of shallow tissue-penetration from external photoexcitation. However, it remains extremely challenging because of lacking a target-specific high-intensity self-luminescence to precisely and effectively drive the photoisomerization. Here, we first report a target-specific tissue-depth-independent photoisomerization by developing a target-specific initiated and -enhanced chemiluminescence (one of self-luminescence) strategy that overcomes the limitation of lacking target-specific high-intensity self-luminescence. Considering that photoisomerization shows boundless glamour in drug-controlled release for disease-specific chemotherapy, we demonstrated applicability of our strategy to apply it in tumor-specific self-luminescence-controlled drug chemotherapy. Specifically, a chemiluminescence substrate and chemiluminescence fluorophore (antitumor drug, CPT) were co-encapsulated in host-guest carriers composed of cyclodextrin and the photoisomerization molecule azobenzene. Tumor-specific HO-induced chemiluminescence preliminarily isomerizes azobenzene, triggering the partial dissociation of host-guest carriers and CPT release. Particularly, the initially released CPT again functions as a chemiluminescence enhancer to achieve enhanced chemiluminescence, assuring target-specific enhanced isomerization and CPT release. With high tumor-inhibition-rate (73%) and no obvious therapy-side-effect indicates the good efficiency and target-specificity of our chemiluminescence-driven photoisomerization. Although we only demonstrated one example of a photoisomerization-related bioapplication, namely photoisomerization-controlled drug chemotherapy, our work provides guidelines to design various target-specific tissue-depth-independent photoisomerization for bioapplications.
10.1039/c8sc04012e
Light-Switchable Azobenzene-Containing Macromolecules: From UV to Near Infrared.
Weis Philipp,Wu Si
Macromolecular rapid communications
Azobenzene-containing macromolecules (azo-macromolecules) such as azobenzene-containing polymers (azopolymers) and azobenzene-functionalized biomacromolecules are photoswitchable macromolecules. Trans-to-cis photoisomerization in conventional azo-macromolecules is induced by ultraviolet (UV) light. However, UV light cannot penetrate deeply into issue and has a very small fraction in sunlight. Therefore, conventional azo-macromolecules are problematic for biomedical and solar-energy-related applications. In this Feature Article, the strategies for constructing visible and near-infrared (NIR) light-responsive azo-macromolecules are reviewed, and the potential applications of visible- and NIR-light-responsive azo-macromolecules in biomedicine and solar energy conversion are highlighted. The remaining challenges in the field of photoswitchable azo-macromolecules are discussed.
10.1002/marc.201700220
Enhanced Release of Molecules upon Ultraviolet (UV) Light Irradiation from Photoresponsive Hydrogels Prepared from Bifunctional Azobenzene and Four-Arm Poly(ethylene glycol).
Rastogi Shiva K,Anderson Hailee E,Lamas Joseph,Barret Scott,Cantu Travis,Zauscher Stefan,Brittain William J,Betancourt Tania
ACS applied materials & interfaces
Advances in biosensors and drug delivery are dependent on hydrogels that respond to external stimuli. In this work, we describe the preparation and characterization of photoresponsive hydrogels prepared by cross-linking of di-NHS ester of azobenzoic acid and four-armed, amine-terminated poly(ethylene glycol). The porous structure and composition of the hydrogels were confirmed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The reversible photoisomerization of the azobenzene-containing hydrogel cross-linkers in the gels was confirmed by absorption spectroscopy. Specifically, the photoisomerization of the cross-linkers between their trans and cis configurations was observed by monitoring the absorbance of the hydrogels at the two characteristic peaks of azobenzene (π-π* at 330 nm and n-π* at 435 nm). The effect of photoisomerization on the hydrogel structure was investigated by microscopy. Ultraviolet (UV) irradiation-induced reduction in hydrogel size was observed, which may be a result of the inherently smaller footprint of the cis azobenzene conformation, as well as dipole-dipole interactions between the polar cis azobenzene and the polymer network. The UV-triggered reduction in hydrogel size was accompanied by enhanced release of the near-infrared fluorescent dye Alexa Fluor 750 (AF). Enhanced release of AF was observed in samples irradiated with UV versus dark control. Together, these data demonstrate the potential of these systems as reversible photoresponsive biomaterials.
10.1021/acsami.6b16183