Meigong Fan

Bio: Meigong Fan is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Photochromism & Triplet state. The author has an hindex of 10, co-authored 42 publications receiving 426 citations.

Photochromic fulgide for holographic recording

Abstract: (N-4'-methoxy-2-methyl-5-phenyl)-3-pyrryl-ethylidene (isopropylidene) succinic anhydride fulgide, doped in PMMA matrix, exhibits photochromic behavior. The fatigue resistance experiment shows no photodegradation is detected after more than 450 writing-erasing cycles. Study of fulgide material for holographic recording media shows the optimal exposure and the diffraction efficiency is 1047 mJ/cm(2) and 2.26%, respectively, with 10 mum thickness polymer film. Holographic grating with 1680 lines/mm at writing angle theta = 30degrees is also obtained. (C) 2004 Elsevier B.V. All rights reserved.

Polarization patterns hide and display using photoinduced anisotropy of photochromic fulgide

Abstract: Photoinduced anisotropy of a photochromic pyrrylfulgide/PMMA film was investigated by using two linearly polarized beams. Excitation by linearly polarized light induces into the film an optical axis that has the same polarization as the excitation beam. This causes a change of the transmittance and of the polarization state of the detection beam. With a microscope a matrix of 4×4 light spots with different polarizations were recorded in the pyrrylfulgide/PMMA film. If readout with non-polarized light, the matrix of light spots show no information pattern. However, when readout with differently polarized lights, different patterns can be displayed. The experiment demonstrates that pyrrylfulgide/PMMA films can be used to hide two differently polarized patterns, which may be applied in camouflage technology.

Acidichromic effects in spiro(1,3,3-trimethylindolo-2,3′-naphth[1,2-b]-1,4-oxazine) a photochromic compound I. Absorption characteristics

Abstract: Acidichromic and photochromic effects in alcoholic solutions of spiro(1,3,3-trimethylindolo-2,3′-naphth[1,2-b]-1,4-oxazine) are described. First-order, thermally-initiated decay kinetics associated with relaxation of the merocyanine form under acidic conditions are reported. A model for acidichromic and photochromic processes in these systems has been proposed. Preliminary results indicate that spirooxazine compounds are potentially useful in device applications such as pH sensors.

Photochromic fulgide for multi-level recording

Abstract: Photochromism of fulgide with dicyanomethylene a, doped in PMMA matrix, has been investigated. It showed that fulgide a undergoes photoisomerization reaction in PMMA film and exhibits fast response, high sensitivity as well as non-destructive readout. Besides, four-level recording of photochromic compound a used as recording media has also explored with 780 nm laser beam.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Spiropyran-based dynamic materials

Abstract: In the past few years, spiropyran has emerged as the molecule-of-choice for the construction of novel dynamic materials. This unique molecular switch undergoes structural isomerisation in response to a variety of orthogonal stimuli, e.g. light, temperature, metal ions, redox potential, and mechanical stress. Incorporation of this switch onto macromolecular supports or inorganic scaffolds allows for the creation of robust dynamic materials. This review discusses the synthesis, switching conditions, and use of dynamic materials in which spiropyran has been attached to the surfaces of polymers, biomacromolecules, inorganic nanoparticles, as well as solid surfaces. The resulting materials show fascinating properties whereby the state of the switch intimately affects a multitude of useful properties of the support. The utility of the spiropyran switch will undoubtedly endow these materials with far-reaching applications in the near future.

Organic photoresponse materials and devices

Abstract: Organic photoresponse materials and devices are critically important to organic optoelectronics and energy crises. The activities of photoresponse in organic materials can be summarized in three effects, photoconductive, photovoltaic and optical memory effects. Correspondingly, devices based on the three effects can be divided into (i) photoconductive devices such as photodetectors, photoreceptors, photoswitches and phototransistors, (ii) photovoltaic devices such as organic solar cells, and (iii) optical data storage devices. It is expected that this systematic analysis of photoresponse materials and devices could be a guide for the better understanding of structure–property relationships of organic materials and provide key clues for the fabrication of high performance organic optoelectronic devices, the integration of them in circuits and the application of them in renewable green energy strategies (critical review, 452 references).

25th Anniversary Article: Organic Electronics Marries Photochromism: Generation of Multifunctional Interfaces, Materials, and Devices

Abstract: Organic semiconductors have garnered significant interest as key components for flexible, low-cost, and large-area electronics. Hitherto, both materials and processing thereof seems to head towards a mature technology which shall ultimately meet expectations and efforts built up over the past years. However, by its own organic electronics cannot compete or complement the silicon-based electronics in integrating multiple functions in a small area unless novel solutions are brought into play. Photochromic molecules are small organic molecules able to undergo reversible photochemical isomerization between (at least) two (meta)stable states which exhibit markedly different properties. They can be embedded as additional component in organic-based materials ready to be exploited in devices such as OLEDs, OFETs, and OLETs. The structurally controlled incorporation of photochromic molecules can be done at various interfaces of a device, including the electrode/semiconductor or dielectric/semiconductor interface, or even as a binary mixture in the active layer, in order to impart a light responsive nature to the device. This can be accomplished by modulating via a light stimulus fundamental physico-chemical properties such as charge injection and transport in the device.