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.

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

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.

/pdf/spiropyran-based-dynamic-materials-4c1onvrhup.pdf

Spiropyran-based dynamic materials

Organic (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technological promises include low cost of these materials and the possibility of their room-temperature deposition from solution on large-area and/or flexible substrates. The article reviews the current understanding of the physical mechanisms that determine the (opto)electronic properties of high-performance organic materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Additionally, it highlights the capabilities of various experimental techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small molecules and on conjug...

Organic Optoelectronic Materials: Mechanisms and Applications

Xerographic photoreceptors charge acceptance and dark discharge photoinduced discharge photogeneration theories photogeneration in organic solids charge transport theories charge transport in polymers and related materials experimental techniques photoreceptor preparation photoreceptors fatigue summary and future requirements.

Organic Photoreceptors for Imaging Systems

Stereolithography is a solid freeform technique (SFF) that was introduced in the late 1980s Although many other techniques have been developed since then, stereolithography remains one of the most powerful and versatile of all SFF techniques It has the highest fabrication accuracy and an increasing number of materials that can be processed is becoming available In this paper we discuss the characteristic features of the stereolithography technique and compare it to other SFF techniques The biomedical applications of stereolithography are reviewed, as well as the biodegradable resin materials that have been developed for use with stereolithography Finally, an overview of the application of stereolithography in preparing porous structures for tissue engineering is given

A review on stereolithography and its applications in biomedical engineering

Organic holographic materials such as photorefractive polymers are one of the promising candidates for the next generation three dimensional (3D) real-time display. Recently, we found that polymer composite of monolithic organic compound of 3-[(4-nitrophenyl)azo]-9H-carbazole-9-ethanol (NACzE) (30 wt%) doped transparent polymethylmethacrylate (PMMA) had capability of recording and displaying new images within a few seconds and fixed at ten seconds and viewing for a longer time without applying electric field. Here, we present 3D holographic display using monolithic organic compound NACzE dispersed transparent PMMA film sandwiched between two glass plates with size of 7.5 × 5 cm2. The thickness of film is ca. 50 μm. Images are easily and completely erased by over recording and it is accelerated by slight heating.

Real-time three-dimensional holographic display using a monolithic organic compound dispersed film

The high thermal stability of the photomerocyanine-form (PMC-form) of spiropyran (SP) dispersed in perhydropolysilazane (PHPS), which converted to silica at ambient temperature, was investigated. PHPS was converted to silica by the de-ammonium reaction with water vapor within approximately 48 h. The structure of the converted silica was not only SiO2, but also partially uncondensed Si–OH and O–H. The PMC-form with high thermal stability was attributed to the protonated form, which was produced by intermolecular hydrogen bonding between oxide anion generated by cleavage of C–O bonds and the partially uncondensed Si–OH and O–H of silica. The protonated PMC-form was directly generated from the SP-form without UV light irradiation, because the singlet ground state of the PMC-form (PMC0) is lower than that of the SP-form (SP0) in silica. In this mechanism, the singlet ground state of the protonated PMC-form (H⋯PMC0), which is significantly stabilized by silica, had polarity similar to water. The stabilization of the PMC-form was attributed to hydrogen bonding between silica and direct generation from the SP-form by reverse photochromism.

Reverse photochromism of spiropyran in silica

In recent years, low-cost and effective technologies for oil-water separation have been highly desired due to an increase of oily wastewater and frequent oil spill accidents. This study demonstrates a cost-effective and sustainable preparation of flexible fibrous membranes with high oil-water separation performance using recycled polyethylene terephthalate (rPET). The rPET fibrous membrane was prepared via electrospinning; in the following step, the rPET membrane was dip-coated with polydimethylsiloxane (PDMS) to improve the water intrusion pressure and anti-water-fouling property of the rPET fibrous membrane. The effect of PDMS concentration on the membrane morphology, surface chemistry, thermal and mechanical properties, surface wettability and oil-water separation performance was evaluated. The membranes are superoleophilic with an oil contact angle of 0° and exhibit excellent anti-water-fouling properties. The PDMS-functionalized rPET membranes can effectively separate various oil-water mixtures driven by gravity, with a high flux (∼ 20,000 L m−2  h-1) and a high separation efficiency (> 98 %) for up to ten cycles and thus has potential industrial application.

Recycled PET as a PDMS-Functionalized electrospun fibrous membrane for oil-water separation

The mechanism for negative photochromism of spiropyran in silica

We present here the poly(4-diphenylamino)styrene (PDAS)-based photorefractive composites with a high-speed response time. PDAS was synthesized as a photoconductive polymer and photorefractive polymeric composite (PPC) films by using triphenylamine (TPA) (or ethylcarbazole, ECZ), 4-homopiperidino-2-fluorobenzylidene malononitrile (FDCST), and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were investigated. The photorefractive quantities of the PDAS-based PPCs were determined by a degenerate four-wave mixing (DFWM) technique. Additionally, the holographic images were recorded through an appropriate PDAS-based PPC. Those holographic images clearly reconstruct the original motion with high-speed quality. The present approach provides a promising candidate for the future application of dynamic holographic displays.

https://iopscience.iop.org/article/10.1143/APEX.5.064101/pdf

Kenji Kinashi

Papers

Real-time three-dimensional holographic display using a monolithic organic compound dispersed film

Reverse photochromism of spiropyran in silica

Recycled PET as a PDMS-Functionalized electrospun fibrous membrane for oil-water separation

The mechanism for negative photochromism of spiropyran in silica

High-Speed Photorefractive Response Capability in Triphenylamine Polymer-Based Composites