China
Africa
Explore chapters and articles related to this topic
Solar Cells Based on Cyanine and Polymethine Dyes
Published in Sun Sam-Shajing, Sariciftci Niyazi Serdar, Organic Photovoltaics, 2017
Cyanine dyes have very large absorption extinction coefficients (~10−5M−1cm−1). However, the absorption peaks of monomers in solution are very sharp and exhibit typical vibronic shoulder absorption. The fluorescent quantum yield of cyanines is usually low and the Stokes shift is relatively small. It seems that cyanine dyes are not suitable for use as solar cell sensitizers, since solar cell materials need to have strong absorption in the whole spectrum in order to harvest the light. Indeed when cyanine dyes are adsorbed on the nanocrystalline TiO2 film, they can form J- and H-aggregate (about J- and H-aggregate, see Ref. [5]), which broadens the absorption spectra of the electrode in the visible region. So cyanine dyes with carboxyl groups in the alkyl chain (Scheme 1) [6,7] and in the aromatic ring (Scheme 2) [8,9] were synthesized to study their performance in DSSCs.
Practical Aspects of Localization Microscopy
Published in Guy Cox, Fundamentals of Fluorescence Imaging, 2019
Mark B. Cannell, Christian Soeller, David Baddeley
There are a number of subtly different flavors of localization microscopy, sharing the same underlying principle but exploiting different mechanisms to switch the fluorescent molecules between fluorescent and dark states. The major approaches to switching and their respective acronyms are: PALM/fPALM [6, 8] (photoactivated localization microscopy), which uses fluorescent probes that are initially dark (in the channel of interest) such as PA-GFP, mEos, or caged fluorescein. Exposure to weak UV light (typically at 405 nm) stochastically turns some molecules on which are then rapidly bleached by stronger readout illumination.STORM [7] (stochastic optical reconstruction microscopy), which uses a pairing of two small molecule dyes, one of which is typically a Cy5 or Cy7 derivative and fluoresces at the far red end of the spectrum, the other is typically a shorter wavelength excited dye used for activation. Exposing the cyanine dye to intense illumination in the presence of thiols in the solution will cause a transition to a dark state, from which it can be effectively recovered by excitation of the shorter wavelength dye.dSTORM/RPM/GSDIM [10–12], which expand on the STORM concept, extending it both to a wider range of dyes and dispensing with the specific activator dye, instead relying on either thermal relaxation or a weak blue/UV absorption characteristic of the dark state for reactivation.
*
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Eun-Kyung Lim, Taekhoon Kim, Soonmyung Paik, Seungjoo Haam, Yong-Min Huh, Kwangyeol Lee
Organic fluorescent dyes such as cyanine 5.5 (Cy5.5) and fluorescein isothiocyanate (FITC) are widely used to monitor molecular events in biological systems. Visible or ultraviolet (UV) light used to excite organic dyes does not penetrate deeply into the tissue, which confines application of organic dyes in bioimaging mainly to cells. In addition, individual organic dyes are photobleachable and rather toxic.
Self-assembled molecular devices: a minireview
Published in Instrumentation Science & Technology, 2020
Until recently, the photoisomerization of helical pyran groups caused changes in chiral signals, making the system behave as a chiroptical switch. Based on this phenomenon, Miao et al.[52] designed two enantiomeric helical pyran-conjugated l (d)-glutamate gels (SP-LG and SP-DG), which could self-assemble into the nanoscale helix through the gel. Under the alternating irradiation of ultraviolet and visible light, spiropyrane in a supramolecular gel ran through the reversible changes between the blue zwitterionic cyanine state and the colorless closed ring spiropyrane.
Enhanced wavelength-sensitivity of volume holographic grating with dual-photoinitiation system in polymer-dispersed liquid crystal
Published in Liquid Crystals, 2019
Kangni Wang, Jihong Zheng, Linyong Qian, Yourong Liu
Photoinitiation system within H-PDLC gratings plays a crucial role for photopolymerisation because it decides the wavelength of the recording light and its concentration also influences the quality of hologram [13]. Photoinitiators postpone the polymerisation gelation and also increase the gelation time difference between the bright and dark areas of the holographic patterns [14]. If the time of the LC molecules diffusion is faster than their nucleation and the nucleation occurs much faster than gelation, a well-defined grating is formed and affords high DE. Commonly used photoinitiators for fabricating H-PDLC gratings include Ingacure 1173 for ultraviolet light [15], Rhodamine 6G dye, rose bengal (RB), Ingacure 784 for green and blue light [16], methylene blue (MB), H-Nu-Blue 640 used for red light [17,18], and Cyanine dye IR-140 for near infrared light [19]. The photoinitiator requires good absorption at the recording wavelength and their coordination with coinitiators to induce photopolymerisation. Despite the diversity and wide applications of each photoinitiation system, little has been reported about the combination of two or more photoinitiators for the formation of H-PDLC gratings. Previously, our group proposed a multi-colour composite grating, especially for its application within autostereoscopic display [20]; however, the electro-optical features and holographic characteristic parameters compared with the gratings exposure upon a single photoinitiation system, such as sensitivity and refractive index modulation remain unclear. Herein, we mix two groups of photoinitiation systems including RB/N-phenylglycine (NPG) and MB/p-toluenesulfonic acid (PTSA) for both green and red laser beams, which enable the fabrication of H-PDLC gratings upon two different visible laser lights with an output wavelength of 532 and 632.8 nm. Distinct from previous reports, a detailed comparative analysis between dual- and single photoinitiation system for H-PDLC grating fabrication is carried out by experiment. In addition, three-dimensional (3D) images of a coin have been reconstructed within a single-layer H-PDLC hologram by using both green and red laser source.