Photochromic Diarylethene Research Articles

Boundary formation in photochromic diarylethene single crystals and its catastrophe theory modeling

Photochromic diarylethenes that are reversibly isomerized by visible and ultraviolet light irradiation could be had the potential to be utilized in a variety of functional devices and systems. In this study, we observed the autonomous formation of a sharp, nanometer-scale boundary between two different surface morphology of photochromic diarylethene crystals when both visible and ultraviolet light were irradiated. We developed a theoretical model using catastrophe theory, which agrees with our experimental observations. This study not only reveals a fundamental experimental finding regarding photochromic crystals but also provides interesting resources to be utilized for future natural intelligent devices and systems.

Re-entrant Photoinduced Morphological Transformation and Temperature-Dependent Kinetic Products of a Rectangular Amphiphilic Diarylethene Assembly.

An amphiphilic rectangular-shaped photochromic diarylethene bearing two hydrophobic alkyl chains and two hydrophilic tri(ethylene glycol) chains was synthesized, and its photoinduced morphological transformation in water was investigated. Two unexpected phenomena were revealed in the course of the experiments: a re-entrant photoinduced macroscopic morphological transformation and temperature-dependent kinetic products of supramolecular assembly. When the pure closed-ring isomer was dispersed in water, a re-entrant photoinduced morphological transformation, that is, a photoinduced transition from the hydrated phase to the dehydrated phase and then back to the hydrated phase, was observed by optical microscopy upon irradiation with green light at 20 °C; this was interpreted by the V-shaped phase diagram of the LCST transition. The aqueous assembly of the pure closed-ring isomer was controlled by changing the temperature; specifically, rapid cooling to 15 and 5 °C gave J and H aggregates, respectively, as the kinetic products. The thermodynamic product at both temperatures was a mixture of mostly H aggregate with a small amount of J aggregate. This behavior was rationalized by the temperature-dependent potential energy surface of the supramolecular assembly.

Feasibility study of a photochromic diarylethene film as a clinical dosimeter for kV X-rays

Radiochromic film (RCF) is commonly used as a measurement tool in radiation therapy and diagnostic X-ray imaging. However, the results are not immediately available. This study establishes the workflow of a new diarylethene (DAE) film dosimetry and investigates the film response versus dose against kV X-rays, with the results immediately available for analysis. The DAE film includes a phosphor layer (BaFCl:Eu), a DAE layer, and a UV cut filter. The workflow of the DAE film dosimetry is as follows: (1) irradiation, where the absorbed doses were between 0.1 and 5.0 Gy at 150 kVp X-ray; (2) scanning with blue excitation light (λ = 465 nm) within 1 h of irradiation to obtain a fluorescence intensity map; and (3) analysis of the relationship between the fluorescence intensity and the absorbed dose, and then comparison between such relationship and that between the optical density and absorbed dose of the RCF. Results show that the fluorescence intensity of the DAE film increased with increasing dose. Moreover, the DAE film had a roughly linear response, while the response of RCF was logarithmic (Pearson's correlation coefficients are 0.979 and 0.843, respectively). The DAE film is feasible as a clinical dosimeter of choice.

Ternary‐Responsive Field‐Effect Transistors and Multilevel Memories Based on Asymmetrically Functionalized Janus Few‐Layer WSe2

AbstractHybrids composed of 2D transition metal dichalcogenides with stimuli‐responsive molecules are prototypical components for the development of multifunctional field‐effect transistors (FETs), whose output currents can be remotely controlled by external inputs. Herein, ternary‐responsive FETs based on a few‐layer WSe2 are realized by decorating the two opposite surfaces of the 2D semiconductor with different stimuli‐responsive molecules in an asymmetric fashion: the bottom surface is interfaced with a photochromic diarylethene film and the top surface with a ferroelectric poly(vinylidene fluoride–trifluoroethylene) layer. This novel Janus ternary device architecture shows superior functional complexity compared with normal mono‐stimuli‐responsive FETs. The synergy between the two molecularly induced effects enables the devices to respond orthogonally to an electric field and light irradiation, with an enhanced output current modulation efficiency of 87%. The 9 ferroelectric and 84 photo‐generated states ensure 756 current levels in a single device. The over 10 cycles of cyclic endurance and more than 1000 h of retention time confirm the reliability of each state, implementing the demand for high‐density non‐volatile memories, as well as enriching the diversification in “More than Moore” technologies.

Molecule deposition in mask-shielded regions revealed by selective Mg vapor deposition

Vacuum deposition with a shadow mask has been widely used for preparing patterned organic films. We found that, during vacuum deposition of organic molecules with a shadow mask, a small amount of organic molecule was also deposited on the mask-shielded surface. This phenomenon was revealed by selective Mg-vapor deposition using photochromic diarylethenes (DAEs). With this selective Mg deposition, no Mg is deposited on the DAE surface in a colorless state with a low Tg near room temperature, even if the DAE film thickness is at a several-nm level. On the other hand, since Mg is deposited on the colored surface obtained by UV irradiation, the presence or absence of low-Tg organic film with a thickness of several-nm level can be determined by the Mg-deposition property. The Mg nondeposition areas of a mask-shielded region depended on the vacuum level, the space between a substrate and a shadow mask, and the DAE deposition quantity; a lower vacuum level (higher pressures), a thicker space, and a larger deposition quantity resulted in a larger Mg nondeposition area. Vacuum deposition in the high vacuum level (10−4–10−3 Pa) with a substrate-shadow-mask space distance of 60 μm led to an Mg nondeposition width over 100 μm from the mask-shielded edge. These results indicate that the origin is in molecular scattering by a residual gas in a vacuum chamber. When minute organic patterns are prepared using shadow masks, which are effective for obtaining satisfactory performances of organic electronics devices, the influence of small amount of deposition under mask-shielded areas should be taken into account.

Light-Driven Rapid Peeling of Photochromic Diarylethene Single Crystals

Macroscopic transformation such as the molecular motors of biology is brought by transforming the protein using the chemical reaction of molecules by external stimuli. If it is possible to achieve it as machine-like in nanometer to micrometer size in photomechanical phenomena, there is a possibility of the application as driving devices of micro- or nanomachineries that drive without any electrical contact. Since light is useful to operate it without any direct contact as external stimuli and leads to rapid photochemical reactions, the operation at high speed can be expected. Here we newly found that crystals of a photochromic diarylethene exhibit a peeling behavior with astonishingly rapid velocity by photoirradiation to a lateral face in addition to separation behaviors such as jumping and cracking by photoirradiation to a well-developed face. The detail of the rapid photoresponsive peeling was discussed based on the molecular packings and the dependence on crystal size and photoirradiation conditions. These crystals can be potentially applied to macroscopic photomechanical actuators rapidly driven based on molecular machinery.

Zero-crosstalk and color-specific photoswitching of dual-emissive polymer nanoparticles for multiple applications

Color-specific photoswitchable dual-emissive systems are highly desirable for encryption, bioimaging and other applications. However, it is difficult to design ideal systems with ultrahigh switching efficiency and none overlap of emission signals. Herein, we report a class of zero-crosstalk dual-emissive polymer nanoparticles (ZDPNs) showing fully color-specific photoswitching property. ZDPNs contain a photochromic fluorescent diarylethene (DBTEO) and a fluorescent tetraphenylporphyrin (TPP) dye. TPP displays large Stokes shift and none spectral overlap with ring-closed form of DBTEO and therefore, blocked energy transfer effect is achieved. Upon irradiation of different lights, cyan emission of DBTEO is 100% photo-switched, while the red fluorescence from TPP is constant. Polymer nanoparticles with different photoswitchable dual-emissive signals can be prepared by simply adjusting the feeding ratio of DBTEO and TPP. In addition, taking advantages of the facile synthesis, good water dispersibility, high-contrast of dual-emissive signals, prominent photoreversibility and photostability of the as-prepared nanoparticles, these nanoparticles exhibit great potentials in multiple applications including information encryption, anti-counterfeiting, photo-rewritable patterning and cancer cell-targeted dual-color bioimaging.

Selective noble-metal deposition modulation on photocurable polydimethylsiloxane films for electronics device applications

Selective metal-vapor deposition on organic surfaces is an interesting phenomenon and is applicable to prepare fine metal patterns for various electronic and photonic devices based on vacuum evaporation without a shadow mask. However, selective metal-vapor deposition with photochromic diarylethenes has not been successful for noble metals such as Au, Ag and Cu, which are generally used in the electronics field. In this paper, we report deposition modulation of noble-metal vapor on a photocurable polydimethylsiloxane (PDMS) film. When Au, Ag or Cu was vacuum-deposited on the UV-curable PDMS, Au and Cu formed a film on the surface even on the uncured film. Ag, however, was desorbed from the uncured film, and a small amount of evaporated Ag atoms was absorbed into the film. This metal species dependence on metal-deposition/desorption tendency was correlated with the intrinsic vapor pressure of metal species; metals with a high vapor pressure tend to desorb. The uncured film with a small amount of Ag deposition was easily removed with a hexane rinse, leaving only Ag on the cured film. Using this principle, various Ag-film patterns were prepared by irradiating upon UV light with a photomask to form a cured pattern and using maskless Ag deposition. Furthermore, we succeeded in fabrication of fine Ag patterns with a width of several micron by UV-laser scanning and maskless Ag-vapor deposition. This method would be applied to the electrode/wiring for various electronic devices.

Constructing photochromic diarylethene with NIR-absorption beyond 800 nm

Near-infrared (NIR) absorbing dyes have received increasing attention due to their ability of NIR radiation absorption and efficient light-to-heat conversion. NIR absorbing photochromic diarylethene (DAE) materials, which could modulate NIR absorption upon light stimulation, provide a convenient route to fabricate smart NIR absorbers. In this study, we constructed a new NIR absorbing photochromic DAE system, of which NIR absorption stems from closed isomer bearing triarylamine (TAA) radical (TDEc-ox). Upon 365/440 nm light irradiation, the open isomer TDEo undergoes photo-oxidation and cyclization to yield TDEc-ox, which exhibited NIR absorption at 928 nm in chloroform. TDEc-ox possesses a photo-inactive feature facilitating non-destructive readout of NIR absorption and high stability (lifetime time ≥ 3 days). Contrary to TDEo, the closed isomer TDEc cannot be directly photo-oxidized to give TDEc-ox. This discrepancy makes TDEc a “photogenerated TAA radical reservoir”: after cycles of photoisomerization, a controllable accumulation of NIR absorbing TDEc-ox can be achieved.

Synthesis and properties of photochromic hybrid diarylethenes bearing benzothiophene and pyrrole moieties

Two diarylethenes containing the hybrid structures of benzothiophene and pyrrole backbone were synthesized and their structures and properties including photochromism, fatigue resistance, and fluorescence were systematically investigated. Both of them exhibit good photochromisms and can function as fluorescence switches in both solution and solid state upon the irradiations of UV/vis lights. Compared with that bearing cyano group (1O), the carboxamide group containing diarylethene (2O) exhibits a higher molar absorption coefficient in solution, and its maximum absorption in solid state red-shifts by 30 nm, as compared with that in solution. In addition, the application potentials of 2O in bioimaging are demonstrated with excellent performances under physiological conditions.

"Click-switch" - one-step conversion of organic azides into photochromic diarylethenes for the generation of light-controlled systems.

Diarylethenes (DAEs) are an established class of photochromic molecules, but their effective incorporation into pre-existing targets is synthetically difficult. Here we describe a new class of DAEs in which one of the aryl rings is a 1,2,3-triazole that is formed by “click” chemistry between an azide on the target and a matching alkyne–cyclopentene–thiophene component. This late-stage zero-length linking allows for tight integration of the DAE with the target, thereby increasing the chances for photomodulation of target functions. Nineteen different DAEs were synthesized and their properties investigated. All showed photochromism. Electron-withdrawing groups, and in particular −M-substituents at the triazole and/or thiophene moiety resulted in DAEs with high photo- and thermostability. Further, the chemical nature of the cyclopentene bridge had a strong influence on the behaviour upon UV light irradiation. Incorporation of perfluorinated cyclopentene led to compounds with high photo- and thermostability, but the reversible photochromic reaction was restricted to halogenated solvents. Compounds containing the perhydrogenated cyclopentene bridge, on the other hand, allowed the reversible photochromic reaction in a wide range of solvents, but had on average lower photo- and thermostabilities. The combination of the perhydrocyclopentene bridge and electron-withdrawing groups resulted in a DAE with improved photostability and no solvent restriction. Quantum chemical calculations helped to identify the photoproducts formed in halogenated as well as non-halogenated solvents. For two optimized DAE photoswitches, photostationary state composition and reaction quantum yields were determined. These data revealed efficient photochemical ring closure and opening. We envision applications of these new photochromic diarylethenes in photonics, nanotechnology, photobiology, photopharmacology and materials science.

Measurement of glass-transition temperature of thermoreversible photochromic materials based on mechanochemical amorphization

Photochromic diarylethene (DAE) materials are expected to be applied to various organic devices, and it is important to measure the glass transition temperature (Tg) in order to evaluate their stability. Although DAEs have excellent thermal stability, their colored state has a high melting point, and either a thermal cyclo-reversion reaction or decomposition occurs during the differential scanning calorimetry (DSC) measurement. Tgs in the colored state, therefore, are hard to measure. In this study, we succeeded in measuring Tgs of the colored state with DSC by preparing the colored amorphous state based on a mechanochemical effect for various DAEs. In addition, the relationship between the isomerization ratio and Tg was determined by combining the amorphization and the thermal reversion reaction near the melting point. It was found that Tg changed monotonically according to the isomerization ratio.

A highly selective colorimetric and fluorescent probe for Cu2+ based diarylethene with a diaminomaleonitrile unit

A novel photochromic diarylethene derivative containing a diaminomaleonitrile unit (1O) was synthesized and its colorimetric and fluorescent turn-on sensing of Cu2+ in acetonitrile solution was demonstrated. Both of its open- and closed-loop isomers (1O and 1C) were highly selective for Cu2+ with obvious absorption and color transforms. Moreover, the addition of Cu2+ enhanced the fluorescence of 1O up to 174-fold with the concomitant color change from colorless to blue. The limit of detections (LODs) for Cu2+ was determined to be 1.76 × 10−8 mol L−1. The stoichiometry of 1: 1 between the probe 1O and Cu2+ was measured in Job’s plot and ESI-MS. Most remarkably, the probe 1O could be used to detect Cu2+ in test strip.

Photo‐Modulated Reversible Switching of Fluorescence from ZnO Quantum Dots with a Photochromic Diarylethene

AbstractA photo controlled and reversible fluorescent switching system was constructed with fluorescence ZnO quantum dots (ZnO‐QDs) and a photochromic diarylethene. Upon alternate irradiation with UV and visible lights, the fluorescence emission of the ZnO‐QDs could be modulated between ‘‘ON’’ and ‘‘OFF’’ repeatedly. The results indicated that the strategy of constructing ZnO‐QDs/diarylethene based switching system was feasibility. Moreover, a logic circuit was designed with the fluorescence intensity at 568 nm as output and the diarylethene and UV/vis lights as inputs.

Reversible Photoinduced Luminescence Modulation from Nanospheres Containing CdSe/ZnS Quantum Dots and Photochromic Diarylethene

We prepared for the first time photoactive colloidal nanospheres consisting of hydrophobic CdSe/ZnS core–shell quantum dots encapsulated in an amphiphilic PMAT polymeric shell containing photochrom...

Enhanced Photochromism of Diarylethene Induced by Excitation of Localized Surface Plasmon Resonance on Regular Arrays of Gold Nanoparticles.

Localized surface plasmon resonance (LSPR) excitation on the photochromic reaction of a diarylethene derivative (DE) was studied by surface enhanced Raman scattering (SERS). UV and visible light irradiations transform reversibly DE between open-form (OF) and closed-form (CF) isomers, respectively. A mixture of PMMA and DE (either OF or CF isomer) was spin-coated onto gold nanorods (GNRs) arrays, designed by electron beam lithography, with two localized surface plasmon resonances (LSPR) at distinct wavelengths, due to their anisotropy. The photochromic reaction rates from CF to OF isomers, under LSPR excitation, were monitored from SERS spectral changes under different polarizations, on the same GNR substrate to compare the effect of LSPR field strength. It appears that the photoisomerization rate was faster when LSPR was excited with the polarization parallel to the GNR long axis. The present results highlight a potential genuine mechanism, from near field LSPR excitation, involved in the photochromic enhancement of diarylethene photochromes.

Electronic transport induced by doping on the electrodes in molecular devices

The electronic transport properties of molecular device based on photochromic diarylethene with carbon nanotube electrode are investigated by density functional theory and non-equilibrium Green’s function. The devices with open and closed configurations show a switching effect. It is found that doping of different amounts of nitrogen atoms on left electrodes results in different electronic transport properties. In addition, we discuss the observed oscillation of current in the devices induced by doping using transmission eigenstates and transmission spectra of the device. The local density of states of the device is calculated to analyze the observed rectifying behavior. The results suggest that doping of nitrogen atoms on the left electrode can be considered as a factor to modulate the electronic transport properties of molecular device.

Geometrical Evolution and Formation of the Photoproduct in the Cycloreversion Reaction of a Diarylethene Derivative Probed by Vibrational Spectroscopy.

The front cover artwork is provided by the groups of Prof. Hiroshi Miyasaka (Osaka University, Japan), Prof. Masahiro Irie (Rikkyo University, Japan), Prof. Seiya Kobatake (Osaka City University, Japan) and Prof. Akira Sakamoto (Aoyama Gakuin University, Japan). The image shows the coherently vibrating closed form of a photochromic diarylethene derivative in the excited state, and subsequent structural evolution into the open form in the cycloreversion reaction. Read the full text of the Article at 10.1002/cphc.202000315.

Front Cover: Geometrical Evolution and Formation of the Photoproduct in the Cycloreversion Reaction of a Diarylethene Derivative Probed by Vibrational Spectroscopy (ChemPhysChem 14/2020)

The Front Cover shows the coherently vibrating closed form of a photochromic diarylethene derivative in the excited state, and subsequent structural evolution into the open form in the cycloreversion reaction. More information can be found in the Article by Hikaru Sotome, Hiroshi Miyasaka, and co-workers.

A new multi-functional fluorescent mercuric ion sensor based on diarylethene with triazole-linked rhodamine B unit

A novel photochromic diarylethene fluorescence sensor 1o bearing a triazole-linked rhodamine B unit was designed and synthesized. Results showed that 1o had multi-responsive photoswitchable characteristics under the stimulation of light, proton, and specific metal ions. It also showed highly selectivity and sensitivity to recognize Hg2+ over other interfering heavy and transition metal ions through the spirolactam ring-opening reaction, which could be detected with “naked-eyes”. Upon the treatment with Hg2+, the fluorescence intensity of 1o at 606 nm was enhanced by 88-fold with notable fluorescence color changing from dark to pink. And its detection limit to Hg2+ was as low as 0.13 μM. Significant fluorescence quenching was observed upon the irradiation with 297 nm light due to FRET between rhodamine B moiety and diarylethene unit. Moreover, an INHIBIT logic gate was established with UV light and proton as the dual data inputs, and the fluorescence intensity at 605 nm as the data output.