Photochromic Activity Research Articles

Fabrication of photochromic, hydrophobic, antibacterial, and ultraviolet-blocking cotton fabric using silica nanoparticles functionalized with a photochromic dye

The aim of this work was the fabrication of cotton fabric with multifunctional properties such as photochromic, hydrophobicity, antibacterial, and ultraviolet (UV) blocking. In this regard, a mixture of silica nanoparticles with spirooxazine as a photochromic dye first applied on the cotton fabric, and then, the fabric surface was coated with an alkylsilane compound. The homogenous distribution of silica and silica/spirooxazine hybrid on the cotton fibers was established by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray mapping. X-ray diffraction patterns confirmed the amorphous nature of the hybrid on the treated cotton fabric. The photochromic effect of the fabrics was measured after 5-min sunlight irradiation. Other characteristics of treated fabrics, such as antibacterial activity, hydrophobic properties, and UV-blocking activity, were also assessed. The results indicated that adding silica nanoparticles to spirooxazine had a tangible effect on photochromic activity of treated cotton fabrics and its photochromic performance was higher than that of the photochromic dye. The fabric showed stable hydrophobicity with static water contact angle values of 141.2° ± 1°. Moreover, the coated cotton fabric demonstrated proper antibacterial properties and UV-blocking activity.

New spiropyrans based on 1,3-benzoxazine-2-one: acid catalyzed synthesis and theoretical insight into the photochromic activity

A new series of spiropyrans based on 1,3-benzoxazine-2-one were synthesized using acid catalysis. Contrary to expectations, 6′-bromo-6-chloro-3-methyl-8′-nitro-spiro[1,3-benzoxazine-4,2′-chromene]-2-one and 6,6′-dichloro-3-methyl-8′-nitro-spiro[1,3-benzoxazine-4,2′-chromene]-2-one did not exhibit photochromic behavior, which was explained by TD DFT calculations to be a consequence of the existence of an effective non-radiative decay pathway allowing the structural relaxation of the spiropyrans in the first singlet excited state.

Two-Photon Excitation of a Plasmonic Nanoswitch Monitored by Single-Molecule Fluorescence Microscopy.

Visible-light excitation of the surface plasmon band of silver nanoplates can effectively localize and concentrate the incident electromagnetic field enhancing the photochemical performance of organic molecules. Herein, the first single-molecule study of the plasmon-assisted isomerization of a photochrome-fluorophore dyad, designed to switch between a nonfluorescent and a fluorescent state in response to the photochromic transformation, is reported. The photochemistry of the switchable assembly, consisting of a photochromic benzooxazine chemically conjugated to a coumarin moiety, is examined in real time with total internal reflection fluorescence microscopy in the presence of silver nanoplates excited with a 633 nm laser. The metallic nanostructures significantly enhance the visible light-induced performance of the photoconversion, which normally requires ultraviolet excitation. The resulting ring-open isomer is strongly fluorescent and can also be excited at 633 nm. These stochastic emission events are used to monitor photochromic activation and show quadratic dependence on incident power. The utilization of a single laser wavelength for both photochromic activation and excitation effectively mimics a pseudo two-colours system.

Calcitic microlens arrays in Archaster typicus: microstructural evidence for an advanced photoreception system in modern starfish

Recent studies have shown that in some light-sensitive species of an brittlestar (Asteroidea, Echinodermata), the upper surface of the dorsal arm plate bears arrays of hemispherical microstructures which in combination with underlying neural bundles and intraskeletal chromatophores probably function as a compound eye. These calcitic lenses possess superior properties such as light weight, mechanical strength, and very low aberration and birefringence; they display a unique focusing effect, signal enhancement, intensity adjustment, angular selectivity, and photochromic activity. The discovery of these unique optical structures revealed that brittlestar visual system is more sophisticated than initially thought and has inspired active interest toward designing of biomimetic highly tunable optical elements for a wide variety of cutting-edge technological applications. Up to this moment, analogous spherical calcitic lenses have been only reported in a few species of modern brittlestars and starfish. Similar calcitic microlenses have been also observed in the Late Cretaceous fossil echinoderms. Here, we report the structural evidence for the presence of calcitic microlenses in an extant species of starfish Archaster typicus. The close resemblance in microstructure and location between the transparent regions of compact stereom described above and microlenses in the photosensitive brittlestar Ophiocoma wendtii suggests that these regions may be involved with the photoreceptor system in A. typicus.

Multifunctional radical-doped polyoxometalate-based host-guest material: photochromism and photocatalytic activity.

An effective strategy to synthesize multifunctional materials is the incorporation of functional organic moieties and metal oxide clusters via self-assembly. A rare multifunctional radical-doped zinc-based host-guest crystalline material was synthesized with a fast-responsive reversible ultraviolet visible light photochromism, photocontrolled tunable luminescence, and highly selective photocatalytic oxidation of benzylic alcohols as a result of blending of distinctively different functional components, naphthalenediimide tectons, and polyoxometalates (POMs). It is highly unique to link π-electron-deficient organic tectons and POMs by unusual POMs anion-π interactions, which are not only conducive to keeping the independence of each component but also effectively promoting the charge transfer or exchange among the components to realize the fast-responsive photochromism, photocontrolled tunable luminescence, and photocatalytic activity.

Photochromic and Electrochromic Properties of Dithienylethene-Based Ruthenium Alkynyl Complexes

Two new binuclear ruthenium alkynyl complexes with dithienylethene unit [{(MePh-tpy)(PPh3)2RuCl}2(C≡C−DTE−C≡C)](ClO4)2 (II-1) and [Cp*Ru(dppe)]2(C≡C−DTE−C≡C) (II-2) (Cp* = pentamethylcyclopentadienyl); (DTE = 1,2-bis(2-methylthiophen-3-yl)cyclopentene) were synthesized. Their structures were well confirmed by nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. Their photochromic behaviors and redox properties have also been investigated. The results indicated that the binuclear ruthenium alkynyl complexes II possessed photochromic activity similar to organic DTE derivatives. Electrochemical studies showed that the open-ring isomers of the metal complexes could be triggered by electricity to convert to their closed forms. These investigations clearly suggested that two complexes can be considered as a class of light- and electro-triggered multifunctional molecule switches.

Hydrothermal synthesis and studies on photochromic properties of Al doped WO3 powder

A series of pure and aluminum (Al) doped WO3 powders were synthesized at low temperature. The as synthesized materials have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–VIS) spectroscopy and color difference meter, respectively. A relation was found between the color difference and the UV–VIS photochromic activity. Moreover, the optical band gap of the as-prepared powder narrowed due to the appearance of impurity levels as the Al3+ ions migrated into the WO3 crystal lattice. Some rod-like particles have been found to decrease with the increase of Al concentration. An optimum Al concentration was found to be 0.25% to present the best UV-light induced photochromic activity. The mechanism of photochromic process of the Al-doped WO3 powders has been discussed in detail based on the characterization results.

Methyl viologen-templated zinc gallophosphate zeolitic material with dual photo-/thermochromism and tuneable photovoltaic activity.

A novel zinc gallophosphate zeolitic material |(C12H14N2)4F1.33|[Ga13.33Zn6.67(PO4)20] (denoted as JU101) has been prepared by using in situ generated methyl viologen (MV) as the template. The framework of JU101 features two building units including an unprecedented fused d6r and a novel [412·64·82·102] cavity. The connection of these two building units forms a 3D intersecting pore system containing 8-rings along the [010] direction, and 10-rings along the [001] and [100] directions. The MV-templated JU101 zeolitic material offers a new type of electron transfer system, which endows the material with interesting photochromism, thermochromism, and tuneable photovoltaic activity in response to light and heating. Importantly, JU101 shows an extended photochromism range from UV to visible light, high thermal stability, as well as a long-lived charge-separated state for potential application in solar energy conversion.

Visible Light Driven Decomposition of Organic Compounds By Two Different Cocatalysts

1. Introduction Photocatalytic decomposition of organic pollutants is one of the promising method for environmental purification. Most of the researchers focused on efficient decomposition of environmental organic contaminants under visible light irradiation or indoor fluorescent light.1 Oxide-supported metal catalysts are widely acknowledged as important catalysts that are related to versatile key in photochromism, chemical sensing and photocatalytic activity. Tungsten trioxide (WO3) acts as a ideal visible light photocatalyst owing to its small band gap energy (2.4-2.8 eV) and high oxidation power of vanlence band holes. But, WO3 exhibits low photocatalytic activity due its high recombination rate of photoexcited electrons and holes. In order to suppress the recombination of photoexcited carriers and significantly increase the photocatalytic efficiency, most research has focused to prepare WO3 doping constituent or WO3 composites.2,3 In the present study, we have synthesized PtPb/WO3 and PtAu/WO3 alloy catalysts, demonstrated to exhibit the efficiency for the decompostion of organic pollutants under visible light irradiation. 2. Experimental A simple one-pot synthesis approach to obtain WO3 supported PtAu catalyst is as follows. In the synthesis, 0.5 g of WO3was suspended in 15 mL of anhyrous methanol for 15 min in a two neck round bottom flask. Pt (0.0075 g) and Au (0.0045 g) precursors were dissolved in 15 mL anhydrous methanol in the shielded vial uder Ar atmosphere and transferred to the suspensions. Then, the solution was stirred for 30 min to yield homogeneous color soluion. Required amount of NaBH4 in mehtanol was injected into the suspensions. The product were washed and centrifuged with anhydrous methanol for three times and dried under vacuum. Similar procedure was followed to synthesis the PtPb/WO3 catalyst. 3. Results and Discussion Figure 1 shows the TEM images of (a) Pt/WO3 (b) PtPb/WO3 and (c) PtAu/WO3 photocatalysts. Pt and PtPb and PtAu NPs are showed monodispersity and homogeneity on the WO3 supports. The average particle size of the three catalysts can be ranked as PtPb/WO3~PtAu/WO3 > Pt/WO3. The TEM results show that the addition of Pb and Au increases the size of NPs. Figure 2 depicts that the CO2 formation profile over different photocatalysts under visible light irradiation time. PtPb/WO3 photocatalyst (1 wt %) shows the higher rate of CO2formation over other photocatalysts. The details about the characterization and photocatalytic activity of catalysts would be discussed in the presentation. 4.

Photo Characterization of Spirooxazine and Naphthopyran Organic Dyes upon UV Irradiation

Organic dyes namely 1,3,3-trimethylindolino-naphtospirooxazine (TINS) and 3,3-diphenyl-3H-napthol [2,1-pyran DNP) were used in studies of photochromic transformation in ethanol solution. The samples were exposed to UV light ranging from 5, 10 and 15s respectively. TINS absorbs UV light at 613nm for multiple exposure time. The absorption initiated the opening of oxazine spirostructure with formation of open merocyanine species. Irradiation of DNP with UV at 5, 10 and 15s absorbs at 413nm with formation of opening cyclicstucture of naphthopyran, namely allenyl-naphtol. The intensity peaks of TINS and DNP were increased with increasing the period of irradiation time. TINS and DNP dyes exhibit normal photochromic in the polar protic solvent by displaying color changes form transparent to color blue and light orange under exposed UV light. The photochromic activity of these compounds is due to the reversible light-induced cleavage of the C-O bond between the heterocyclic oxygen atom and the quaternary carbon.

The influence of oxygen on the microstructural, optical and photochromic properties of polymer-matrix, tungsten-oxide nanocomposite films

An in situ vapor deposition process has been used to create a photochromic, tungsten-oxide, polymer matrix nanocomposite. Under specific processing conditions, the composite consists of discrete tungsten-oxide nanoparticles distributed uniformly throughout the bulk of an optically transparent fluoropolymer matrix. Ultraviolet exposure of the nanocomposite produces characteristic photochromic changes that result in a 40% change in optical transmission. Optical absorption measurements yield a value of 3.08eV for the bandgap of the tungsten-oxide particles. Incorporating oxygen as a supplementary deposition agent in the synthesis process increased the transparency of the films in the visible region, increased the change in transmission due to the photochromic effect, and led to the percolation of larger nanoparticles near the film surface. Growth of particles in this region allowed the nanocomposite to be bleached readily in an oxygen atmosphere while retaining photochromic activity.

Theoretical analysis of an all-photonic multifunctional molecular logic device: Using TD-DFT//DFT to assess photochromic activity of multimeric photochrome

The structures and properties of a single-molecule photochromic switch consisting of 3 photochromic moieties is investigated. Using time-dependent density functional theory (TD-DFT) we calculated the λmax within±30nm (± 0.18eV) and produced spectra that were similar. The charge-transfer (CT) character of the molecular orbitals (MO) was assessed via the overlap between the occupied and virtual orbitals (Λ diagnostic) and did not suffer from CT failure. The MOs were consistent with photochemically productive photochromes. The MO and their contribution to different excited states paralleled both the observed activity and observed inactivity of the photochrome.

1‐Alkyl‐2‐{(O‐Thioalkyl)Phenylazo}Imidazole Complexes of PbII and Their Photochromic Property

AbstractPbII complexes of 1‐alkyl‐2‐{(o‐thioalkyl)phenylazo}imidazole (SRaaiNR'), [Pb(SRaaiNR')2X2] were characterized by spectroscopic studies. The single‐crystal X‐ray structure of [Pb(SEtaaiNEt)2Cl2] (SEtaaiNEt = 1‐ethyl‐2‐{(o‐thioalkyl)phenylazo}imidazole) proved imidazolyl‐N and –SEt coordination forming unusual puckered eight member chelate rings. UV light irradiation of the complexes in DMF solution shows E‐to‐Z (E and Z refer to trans and cis‐configuration about –N=N–, respectively) photoisomerization of the coordinated azoimidazole. The rate of isomerization follows the sequence: [Pb(SRaaiNR')2Cl2] < [Pb(SRaaiNR')2Br2] < [Pb(SRaaiNR')2I2]. Quantum yields (φE→Z) and the activation energy (Ea) of the isomerization of the complexes are lower than observed for the free ligand. This can be explained by considering the molecular assembly and the thus observed increase in mass and rotor volume of the complexes. DFT and TDDFT calculations of optimized geometry could explained the spectral properties and photochromic activity.

Structural and charge‐transfer properties of indolylfulgides

The structural and electronic properties of a photochromic molecule dictate their potential photochemical activity. To gain insight into these influences, the ground‐state structure and excited state properties of six indolylgulgides were calculated using several time dependent‐density functional theory (DFT) (TD‐DFT)//DFT methods, second‐order M⊘ller–Plesset (MP2), and CIS(D). These methods simulated the charge‐transfer properties and the conformation of the ground‐state structure for each molecule. Generally, TD‐DFT accurately simulated the expected charge‐transfer state. The degree of spatial overlap of the occupied and virtual molecular orbitals involved in the S1 transition of indolylfulgides quantitatively assessed their charge‐transfer character and was qualitatively useful in assessing their photochromic activity. The M06, M06‐2X, and M11 structures were quite similar to those calculated by MP2. Structural differences, similarities, and functional trends are compared and discussed. © 2013 Wiley Periodicals, Inc.

Synthesis and Photochromic Activity of a New Diarylethene Bearing Benzo[b]Thiophene Unit

Synthesis and Photochromic Activity of a New Diarylethene Bearing Benzo[b]Thiophene Unit

Transducer influence of polycyclic aromatic hydrocarbons (PAHs) on photoisomerisation of 1-alkyl-2-(arylazo)imidazoles

The UV light irradiation to a solution of 1-alkyl-2-(arylazo)imidazole (L) in toluene shows transformation of trans to cis configuration about NN bond. The rate of photo-isomerisation and quantum yields are influenced by internal parameters like – nature of substituents, coordination to metal ions, steric and electronic effect, protonation etc. and the external factors like solvent (polarity, viscosity, dipole moment etc.), presence of innocent (to be chemically noninteracting) and noninnocent (chemically interacting) ions or molecules. In this work the influence of polycyclic aromatic hydrocarbons (PAH) such as – napththalene, anthracene, phenanthrene, pyrene – an innocent system, on the photochromic efficiency of L has been examined. The PAHs are π-donor and may form a π–π continuum with L which can significantly affect the motional (vibration, rotation) properties of the analyte and hence the photochromic activity. The rate and quantum yield of trans-to-cis isomerisation of L decrease with increasing [PAH] and also with increasing number of the fused phenyl ring(s) in PAH. Thus the photoisomerisation follows the rate sequence: no PAH>napththalene>anthracene–phenanthrene>pyrene. The reverse change, cis-to-trans is very slow upon light irradiation while appreciably fast in thermal process at dark. The activation energy (Ea) also decreases with [PAH] and number of fused phenyl rings.

Synthesis, Characterization, and the Photochromic, Luminescence, Metallogelation and Liquid‐Crystalline Properties of Multifunctional Platinum(II) Bipyridine Complexes

A series of multifunctional platinum(II) bipyridine complexes were designed, synthesized, and characterized by (1)H NMR, fast atom bombardment mass spectrometry (FAB-MS), and elemental analysis. Their electrochemical and photophysical properties were investigated. The photochromic properties of the spironaphthoxazine-containing complexes were also studied. Some of these complexes were shown to be capable of forming stable thermoreversible metallogels in organic solvents. In contrast to typical thermotropic organogels and metallogels, one of the complexes could form metallogels in dodecane and is very stable towards external stimuli. The photochromic activation parameters for the bleaching reaction of a representative spironaphthoxazine-containing complex in a dodecane gel were determined through kinetic studies at various temperatures. Lamellar liquid-crystalline behavior was also observed in one of the complexes, and the liquid-crystalline properties were studied by thermogravimetry analysis (TGA), polarized optical microscopy (POM), differential scanning calorimetry (DSC), variable-temperature X-ray diffraction (XRD), and variable-temperature infrared (IR) spectroscopy.

Effect of hydrothermal temperature on structure and photochromic properties of WO3 powder

Tungsten trioxide (WO3) powders were prepared via a simple hydrothermal method. The morphology, structure and photochromic activity of the synthesized WO3 powders were studied by X-ray diffraction, scanning electron microscopy and UV–vis spectrophotometer combined with color difference meter. The results showed the synthesized WO3 powders with hexagonal phase got much better photochromic properties than the WO3 powders with cubic phase, the ones not appear until about 160°C. Besides, the WO3 powder synthesized at 120°C exhibited the best photochromic properties of the samples prepared below 160°C, the particles of which formed a shape of clusters of cactus with uniform size and good dispersion.

Photochromic Block Copolymer Poly(styrene‐b‐azo monomer) by ATRP

AbstractPhotoactive monomers [(E)‐1(4‐methacryloxyphenyl)‐2‐(nitrophenyl) diazene] (azo 1) and (E)‐1‐(4‐methacryloxyethyl‐phenyl)‐2‐phenyl‐diazene (azo2) were synthesized. The azo 1 monomer showed poor reactivity under the evaluated polymerization method. The Azo 2 monomer was used in the block copolymerization with polystyrene by the normal ATRP methodology. Several polystyrene macroinitiators were prepared with molecular weights of 10, 20 and 30 k g/mol. The end functionality was increased by the addition of 0.1 equivalents of copper II chloride. Block copolymers in 30% yield and low polydispersity were synthesized by ATRP from the polystyrene macroinitiators and the azo monomer. The block copolymer exhibits good photochromic activity.

Photoactive periodic media

Photoactive (photochromic) multilayers of MoO3/SiO2 are studied optically before and after UV excitation. Enhancement in photochromic activity is observed over a wide spectrum and in particular near the photonic band edges where optical changes are up to 25 times greater than in similarly prepared bulk, nonperiodic samples. Applications to light-sensitive devices are discussed.