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Tobias Garling, Yujin Tong, Tamim Darwish, Martin Wolf, R Kramer Campen
Surfaces whose macroscopic properties can be switched by light are potentially useful in a wide variety of applications. One such promising application is electrochemical sensors that can be gated by optically switching the electrode <i>on</i> or <i>off</i>. One way to make such a switchable electrode is by depositing a self-assembled monolayer of bistable, optically switchable molecules onto an electrode surface. Quantitative application of any such sensor requires understanding how changes in interfacial field affect the composition of photostationary states, <i>i...
July 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Chris Ritchie, George Vamvounis, Hamid Soleimaninejad, Trevor A Smith, Evan J Bieske, Viktoras Dryza
The spectroscopic properties of poly(methyl methacrylate) polymer films doped with two kinds of photochromic molecular switches are investigated. A green-fluorescent sulfonyl diarylethene (P1) is combined with either a non-fluorescent diarylethene (P2) or red-fluorescent spiropyran (P3). Photoswitching between the colorless and colored isomers (P1: o-BTFO4 ↔ c-BTFO4, P2: o-DTE ↔ c-DTE, P3: SP ↔ MC) enables the P1 + P2 and P1 + P3 films to be cycled through three distinct states. From the initial state (o-BTFO4 + o-DTE/SP), irradiation with UV light generates the second state (c-BTFO4 + c-DTE/MC), where c-BTFO4 → c-DTE/MC energy transfer is established...
July 19, 2017: Physical Chemistry Chemical Physics: PCCP
Maja Feierabend, Ermin Malic, Andreas Knorr, Gunnar Berghäuser
Atomically thin transition metal dichalcogenides (TMDs) hold promising potential for applications in optoelectronics. Due to their direct band gap and the extraordinarily strong Coulomb interaction, TMDs exhibit efficient light-matter coupling and tightly bound excitons. Moreover, large spin orbit coupling in combination with circular dichroism allows for spin and valley selective optical excitation. As atomically thin materials, they are very sensitive to changes in the surrounding environment. This motivates a functionalization approach, where external molecules are adsorbed to the materials surface to tailor its optical properties...
July 10, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Thomas Halbritter, Christoph Kaiser, Josef Wachtveitl, Alexander Heckel
A highly versatile water-soluble pyridine-spiropyran photoswitch is reported which functions as photoacid in a wide pH range. Under neutral conditions, the open-ring merocyanine (MC-) exists to 48% and closes quantitatively by irradiation with visible light while the reverse reaction occurs rapidly in the dark or by irradiation at 340 nm. The different pKa of the pyridine nitrogen in the closed spiropyran (4.8) and open merocyanine form (6.8) leads to a reversible proton release in a pH range of 3-7. Only negligible hydrolytic decomposition was observed in the pH range from 1-12...
July 7, 2017: Journal of Organic Chemistry
Bijnaneswar Mondal, Aloke Kumar Ghosh, Partha Sarathi Mukherjee
A spiropyran decorated covalent organic cage (PC2) has been designed employing dynamic imine chemistry followed by imine bond reduction. The molecule is capable of altering its colour upon exposure to external stimuli like heat and light. Construction of a 3D organic cage introduces a new piece to the system by swapping of close form to open form in solid state withdiverse colour change. Moreover, this material has high chemical stability and is capable of reversible stimuli-responsive colour change without any degradation for an extended period...
July 5, 2017: Journal of Organic Chemistry
Doory Kim, Zhengyang Zhang, Ke Xu
By recording both the images and emission spectra of thousands of single fluorescent molecules stochastically generated from the ring-opening reaction of a spiropyran, we provide mechanistic insights into its multipath reaction pathways. Through statistics of the measured single-molecule spectra, we identify two spectrally distinct isomers, presumably TTC and TTT cis-trans isomers, for the open-ring merocyanine product, and discover a strong solvent polarity-dependence for the relative population of the two isomers...
July 3, 2017: Journal of the American Chemical Society
Masayuki Suda, Naoto Takashina, Supawadee Namuangruk, Nawee Kungwan, Hidehiro Sakurai, Hiroshi M Yamamoto
The presence of interface dipoles in self-assembled monolayers (SAMs) gives rise to electric-field effects at the device interfaces. SAMs of spiropyran derivatives can be used as photoactive interface dipole layer in field-effect transistors because the photochromism of spiropyrans involves a large dipole moment switching. Recently, light-induced p-type superconductivity in an organic Mott insulator, κ-(BEDT-TTF)2 Cu[N(CN)2 ]Br (κ-Br: BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) has been realized, thanks to the hole carriers induced by significant interface dipole variation in the spiropyran-SAM...
June 29, 2017: Advanced Materials
Chaoqun Liu, Yan Zhang, Min Liu, Zhaowei Chen, Youhui Lin, Wei Li, Fangfang Cao, Zhen Liu, Jinsong Ren, Xiaogang Qu
Most chemotherapeutic drugs commonly suffer from several shortcomings, including the lack of aqueous solubility, limited stability and adverse side effects. Although caging strategy has recently been employed as an effective approach to conceal and stabilize these drugs to achieve light-activated cancer therapy, it is plagued by the sophisticated drug modification process and deleterious solvent usage. In addition, using UV or Visible light to remove photocaged group is restricted to its limited tissue penetration ability in and phototoxicity...
September 2017: Biomaterials
Stephan Stremlau, Friedrich Maass, Petra Tegeder
Spiropyrans are prototype molecular switches, which undergo a reversible photoinduced ring-opening/-closure reaction between the closed three-dimensional spiropyran (SP) and the open, planar merocyanine (MC) form. In solution the SP isomer is the thermodynamically stable form. Using high resolution electron energy loss spectroscopy, we resolve a thermally-activated irreversible ring-opening reaction of nitrospiropyran resulting in the MC form for coverages above one monolayer. Thus, the situation found in solution is reversed for the adsorbed molecules, since the MC form is more stable due to the modified energetics by the presence of the substrate...
August 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Colm Delaney, Peter McCluskey, Simon Coleman, Jeffrey Whyte, Nigel Kent, Dermot Diamond
A novel approach that allows control of flow in microfluidic channels with unsurpassed performance using light is described. Valve structures have been created using photoresponsive hydrogels based on spiropyran-functionalised pNIPAAm hydrogels photopolymerised around pillar structures within the channels. Valve actuation is controlled from outside the fluidic system using externally located LEDs. Highly precise and accurate flow rates can be selected by passing real-time flow rate measurements into a PID algorithm...
May 31, 2017: Lab on a Chip
Dushanthi S Dissanayake, Gregory T McCandless, Mihaela C Stefan, Michael C Biewer
Spiropyrans are notable among different classes of photochromic compounds due to their large structural and electronic transformation upon isomerization. In order to parlay the electronic differences associated with the two isomeric forms into a materials based switch, the spiropyran ultimately requires a covalent attachment through a conjugated pathway. In this work a synthetic method was developed to incorporate spiropyran (SP) into thiophene based materials. A series of compounds with a systematic variation of substituents were synthesized (SP-T, SP-T-Br, SP-T-T, SP-T-T-T and SP-T-T-T-T-SP) and their photochromism in both polar (methanol) and non-polar (toluene) solvents were studied...
July 1, 2017: Photochemical & Photobiological Sciences
L N Corîci, S Shova, V Badea, D Aparaschivei, O Costisor, L Cseh
The network of chemical reactions of 2,6-bis(5-bromo-2-hydroxybenzylidene)cyclohexanone (BHBC) when subjected to light and different pH values has been investigated. The pH dependent species involved in the chemical network have been identified and characterized by NMR and UV-VIS spectroscopy. Direct pH jumps were carried out by adding a strong acid to equilibrated solutions of trans-chalcone (Ct) forming the flavylium cation which was stable only under extremely acidic conditions (pH < 0.5). The single crystal X-ray study and NMR analysis has confirmed the structure of the new flavylium cation...
June 14, 2017: Photochemical & Photobiological Sciences
Meng Li, Weifeng Liu, Qi Zhang, Shiping Zhu
We prepared force sensitive acrylic latex coatings by covalently incorporating spiropyran mechanophore. The acrylic latexes were obtained through emulsion copolymerization of butyl acrylate (BA), methyl methacrylate (MMA) with vinyltriethoxysilane (VTES) as interparticle cross-linker, and (1'-(2-(methacryloyloxy)ethyl)-3',3'-dimethylspiro[chromene-2,2'-indolin]-6-yl)methyl methacrylate) (SP) as intraparticle cross-linker. The latexes of P(BA-co-MMA-co-SP-co-VTES) were subsequently cast onto Teflon-coated surface to form latex coatings...
April 21, 2017: ACS Applied Materials & Interfaces
Jeroen Ter Schiphorst, Giuseppe G Melpignano, Hossein Eslami Amirabadi, Menno H J M Houben, Sterre Bakker, Jaap M J den Toonder, Albertus P H J Schenning
Microfluidic devices allow the manipulation of fluids down to the micrometer scale and are receiving a lot of attention for applications where low volumes and high throughputs are required. In these micro channels, laminar flow usually dominates, which requires long residence times of the fluids, limiting the flow speed and throughput. Here a switchable passive mixer has been developed to control mixing and to easily clean microchannels. The mixer is based on a photoresponsive spiropyran based hydrogel of which the dimensions can be tuned by changing the intensity of the light...
April 18, 2017: Macromolecular Rapid Communications
Seungse Cho, Saewon Kang, Ashish Pandya, Ravi Shanker, Ziyauddin Khan, Youngsu Lee, Jonghwa Park, Stephen L Craig, Hyunhyub Ko
Silver nanowire (AgNW) networks are considered to be promising structures for use as flexible transparent electrodes for various optoelectronic devices. One important application of AgNW transparent electrodes is the flexible touch screens. However, the performances of flexible touch screens are still limited by the large surface roughness and low electrical to optical conductivity ratio of random network AgNW electrodes. In addition, although the perception of writing force on the touch screen enables a variety of different functions, the current technology still relies on the complicated capacitive force touch sensors...
April 25, 2017: ACS Nano
M Livendahl, J Jamroskovic, M Hedenström, T Görlich, N Sabouri, E Chorell
G-quadruplex (G4) DNA structures are involved in many important biological processes and can be linked to several human diseases. Drug-like low molecular weight compounds that target G4 structures are therefore interesting not only for their potential therapeutic properties but also for their potential use as chemical research tools. We report here on the development of methods to synthesize spiropyrans using a condensation-cyclisation reaction of quaternary salts of α-methyl quinoline or phenanthridine with salicylaldehydes...
April 11, 2017: Organic & Biomolecular Chemistry
Papatya Kaner, Xiaoran Hu, Samuel W Thomas, Ayse Asatekin
In this study, we present a novel self-cleaning, photoresponsive membrane that is capable of removing predeposited foulant layers upon changes in surface morphology in response to UV or visible light irradiation while maintaining stable pore size and water permeance. These membranes were prepared by creating thin film composite (TFC) membranes by coating a porous support membrane with a thin layer of novel comb-shaped graft copolymers at two side-chain lengths featuring polyacrylonitrile (PAN) backbones and photoreactive side chains, synthesized by atom transfer radical polymerization (ATRP)...
April 5, 2017: ACS Applied Materials & Interfaces
Denhy Hernández-Melo, Ruy Cervantes, Jorge Tiburcio
A stimulus-responsive guest-containing spiropyran and viologen unit assembles with a 24-membered crown ether into a stable host-guest complex displaying a partially threaded geometry. Acid addition induces guest transformation to a merocyanine species activating a second recognition site, suitable for the formation of a pseudorotaxane. The simultaneous presence of two recognition sites produces a small-amplitude macrocycle shuttling motion, from the viologen to the merocyanine moiety. Base addition returns the guest to its spiropyran form, and concurrently the translation motion stops...
March 30, 2017: Journal of Organic Chemistry
Oliver Brügner, Thomas Reichenbach, Michael Sommer, Michael Walter
The modification of molecular properties by the use of substituents is a versatile route for molecular design. Here we show for the example of multiresponsive spiropyrans that substituent effects and their correlations can be accurately described by Hammett constants, which in turn can be obtained directly from density functional theory calculations. The internal energetic difference ΔU between the noncolored and the colored form is determined for 63 spiropyran derivatives with substituents at the spiropyran N- and C6-positions, and can be described by only five parameters with an accuracy better than 0...
March 24, 2017: Journal of Physical Chemistry. A
Hong Chen, Fengyu Yang, Qiang Chen, Jie Zheng
A newly developed polyacrylamide-co-methyl acrylate/spiropyran (SP) hydrogel crosslinked by SP mechanophore demonstrates multi-stimuli-responsive and mechanically strong properties. The hydrogels not only exhibit thermo-, photo-, and mechano-induced color changes, but also achieve super-strong mechanical properties (tensile stress of 1.45 MPa, tensile strain of ≈600%, and fracture energy of 7300 J m(-2) ). Due to a reversible structural transformation between spiropyran (a ring-close) and merocyanine (a ring-open) states, simple exposure of the hydrogels to white light can reverse color changes and restore mechanical properties...
June 2017: Advanced Materials
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