Ag/TiO2纳米材料的制备和光致变色性能研究

 采用光催化还原法在不同温度热处理的TiO2薄膜表面沉积Ag纳米颗粒,制备了Ag/TiO2纳米薄膜材料。通过UV-Vis吸收光谱表征对比了不同温度热处理的TiO2对Ag粒子光催化沉积的影响,发现500℃退火处理TiO2薄膜较利于Ag纳米粒子的光催化沉积;在650 nm红色激光照射下,500℃退火处理的Ag/TiO2样品具有明显的光致变色现象,对此变色过程中涉及的机理进行了讨论,且发现随着Ag纳米颗粒光催化沉积时间的增长,Ag/TiO2薄膜光致变色的响应速率提高,但Ag纳米颗粒过多会抑制Ag/TiO2薄膜的变色响应速率。     

Photochromic Properties and Surface Enhanced Raman Scattering Spectra of Indoline Spiropyran in Silver-Based Nanocomposite Films

The structure and photochromic transformations of composite organometallic nanosystems composed of Ag nanoparticles covered with a layer of indoline-spiropyran (ISP) molecules from solutions were studied by spectrophotometry, surface Raman scattering spectroscopy (SERS) and quantum chemistry. Analysis of experimental data showed that studied nanostructured systems have photochromic properties, manifested in the reversible photo-induced changes both of the electronic-absorption spectra and of the relative intensity of the SERS bands. The open form of ISP, formed in the organometallic nanostructured film as a result of photochromic transformations, has an adsorption geometry, and, possibly, a conformation different from that formed as a result of chemisorption of ISP molecules on silver colloids.     

Formation of copper nanocrystals in photochromic glasses under electron irradiation and heat treatment

It has been experimentally demonstrated that electron irradiation of photochromic glasses containing ions of univalent copper gives rise to the formation of metallic copper nanocrystals in near-surface layers of the glass. The glass composition and conditions for electron irradiation and heat treatment have been shown to affect the amplitude and spectral position of the plasmon resonance of copper nanoparticles. A model has been proposed for explaining the spectral shift in the plasmon resonance.     

Restructuring of plasmonic nanoparticle aggregates with arbitrary particle size distribution in pulsed laser fields

We have studied processes of interaction of pulsed laser radiation with resonant groups of plasmonic nanoparticles(resonant domains) in large colloidal nanoparticle aggregates having different interparticle gaps and particle size distributions.These processes are responsible for the origin of nonlinear optical effects and photochromic reactions in multiparticle aggregates.To describe photo-induced transformations in resonant domains and alterations in their absorption spectra remaining after the pulse action,we introduce the factor of spectral photomodification.Based on calculation of changes in thermodynamic,mechanical,and optical characteristics of the domains,the histograms of the spectrum photomodification factor have been obtained for various interparticle gaps,an average particle size,and the degree of polydispersity.Variations in spectra have been analyzed depending on the intensity of laser radiation and various combinations of size characteristics of domains.The obtained results can be used to predict manifestation of photochromic effects in composite materials containing different plasmonic nanoparticle aggregates in pulsed laser fields.     

Photochromic Quantum Dots

Russian Physics Journal - Results of fundamental and applied research in the field of creating photochromic core-shell type nanoparticles in which semiconductor nanocrystals – quantum dots...     

Effect of a dielectric shell of a silver nanoparticle on the spectral position of the plasmon resonance of the nanoparticle in photochromic glass

The behavior of the spectral position of the absorption band of colloidal silver in photochromic glass is analyzed in relation to the variation in the refractive index of a thin layer of the medium (shell) that surrounds silver nanoparticles. It is shown that the appearance of a shell with a high refractive index leads to a long-wavelength shift in the plasmon absorption band of silver nanoparticles. These results make it possible to explain particular features of the absorption spectrum of photothermorefractive glasses.     

Tuning of crystal phase structure in hydrated WO3 nanoparticles under wet chemical conditions and studies on their photochromic properties

Hydrated tungsten oxide nanoparticles have been synthesized using a simple wet chemical method while varying the concentration of HCl. XRD studies show that the variation in HCl concentration from 1 M to 6 M in the reaction results into gradual change in crystal structure of hydrated WO₃ from hexagonal (WO₃·0.33H₂O) to pure orthorhombic (WO₃·H₂O), through a series of samples with mixed phase of the two indifferent ratios. The similar variations in the degree of hydration and phase variations have also been observed from Raman, FTIR and TGA studies. The average crystallite size of the hydrated WO₃ particles was estimated to be ～26 nm from XRD line broadening and AFM studies showed the formation of spherical shaped particles for all the samples. The photochromic studies were carried out on the composite films of these materials in the polymeric matrix of polyvinyl alcohol (PVA) while exposing to UV light. The composite films show interesting variations in the photochromic behavior depending on the crystal structure of hydrated WO₃ filler. The photochromic behavior has been explained on the basis of EPR spectra of hydrated WO₃.     

Fluorescent photoswitchable nanohybrids based on photochromism

A new type of fluorescent photoswitchable nanohybrids based on photochromism has been assembled, in which hydrophobic diarylethene and matched fluorescent dye are assembled in the nanoscale crosslinked polymeric matrix via a modified miniemulsion polymerization process and a seeded polymerization technique. The nanohybrids exhibited excellent fluorescent photoswitchable action owing to efficient photoinduced energy transfer whether the nanohybrids as nanoparticles dispersed in water or in a polymer film, and the improved photo-thermal stability of both essential components could be readily achieved. Importantly, our assembling approach is much simpler than the covalent chemical synthesis, and is a general method for other hydrophobic photochromic compounds.     

Photochromism of diarylethene molecules and crystals

Photochromism is defined as a reversible transformation of a chemical species between two isomers upon photoirradiation. Although vast numbers of photochromic molecules have been so far reported, photochromic molecules which exhibit thermally irreversible photochromic reactivity are limited to a few examples. The thermal irreversibility is an indispensable property for the application of photochromic molecules to optical memories and switches. We have developed a new class of photochromic molecules named “diarylethenes”, which show the thermally irreversible photochromic reactivity. The well designed diarylethene derivatives provide outstanding photochromic performance: both isomers are thermally stable for more than 470,000 years, photoinduced coloration/decoloration can be repeated more than 10⁵ cycles, the quantum yield of cyclization reaction is close to 1 (100%), and the response times of both coloration and decoloration are less than 10 ps. This review describes theoretical background of the photochromic reactions, color changes of the derivatives in solution as well as in the single crystalline phase, and application of the crystals to light-driven actuators.     

Synthesis and structure–behavior relationships of tetra-substituted imidazole derivatives of 1,3-diazabicyclo[3,1,0]hex-3-ene

Among photochromic compounds 1,3-diazabicyclo[3.1.0]hex-3-ene derivatives are currently the subject of intense research due to their photochromic behavior particularly in the crystalline state. In this work, the click syntheses of photochromic compounds containing tetrasubstituted imidazole moieties have been investigated. The structure?Cphotochromic behavior relationships of these compounds have been evaluated.     

Photoswitchable Near‐Infrared‐Emitting Boron‐dipyrromethene (BODIPY) Nanoparticles

The reversible photoswitched near‐infrared‐(NIR)‐emitting Boron‐dipyrromethene (BODIPY) containing nanparticles are reported. Dithienylethene derivatives are used as the photochromic unit in the nanoparticle to control the on and off of fluorescence BODIPY molecules. As a result, it is demonstrated that these nanoparticles conduct robust reversible modulation of the NIR fluorescence in vitro and in the cell culture with negligible toxicity. This study may offer a new approach to the use of these nanomaterials for numerous photonic and biophotonic applications.     

光致变色二芳基乙烯多波长光存储研究

多波长光致变色存储是基于光致变色原理的一种高容量光存储方法.介绍了多波长光存储的存储原理、系统构成和光盘结构.利用三波长光致变色存储实验装置，进行了三波长光致变色存储的实验.结果显示，实验中采用的三种光致变色材料可用于多波长存储，多波长存储读出信号对比度较高，各记录信号之间几乎无串扰.记录信息经50次低速读出后仍保持较高对比度. 关键词： 多波长 光致变色 光存储 串扰     

Fabrication and photochromic study of titanate nanotubes loaded with silver nanoparticles

Pure anatase-TiO₂ and/or titanate nanotubes, photochromic Ag loaded titanium dioxide nanotubes (TNTs) and AgCl loaded titanate nanotubes were synthesized by hydrothermal method. The pH value during the neutralization process plays a crucial role in controlling the morphology and composition of the nanotubes. All these nanotubes were confirmed by XRD, TEM, EDS and XPS analysis. Most of them have open ends with inner/outer diameters of 7/10 nm and several hundred nanometers in length. For photochromic behavior in the case of AgCl-titanate nanotubes, the red color can be clearly observed after irradiation by red light, while the yellow, green, blue ones displayed pale black after the corresponding irradiation. On the other hand, Ag loaded TNT sample exhibited multicolor photochromism corresponding to that of incident light. The photoreduction of silver halide to Ag particle in the case of loaded AgCl particles and a particle-plasmon-assisted electron transfer from Ag nanoparticles to TiO₂ in the case of loaded Ag particles are considered to be responsible for this different behavior.     

Luminescence of photochromic centers in calcium fluoride crystals doped with Lu3+ ions

We report data on the luminescence spectra associated with photochromic centers in X-ray irradiated calcium fluoride crystals doped with Lu ions. Irradiation in low energy photochromic centers absorption band excites emission, which can be identify with transitions into photochromic centers. Ab initio calculation of absorption spectrum of photochromic center agrees rather well with experimental data.     

光致变色多阶光存储中的光学串扰分析

利用光致变色材料的灰度分阶特性可以实现多阶光存储。以傅里叶光学和光致变色记录符的可叠加性为基础,采用霍普金斯标量衍射理论的经典归-化坐标,对光致变色多阶光存储中的光学串扰进行了理论建模和数值分析。作为后续电通道补偿设计的前提。数值计算结果表明：相邻记录符与盘基信号的交叉串扰项是光学串扰的主要成分,且随着中心距的增加,相邻记录符引起的串扰迅速降低;当无寻道误差时,邻道记录符引起的串扰可以忽略;高阶记录符引起串扰要明显高于低阶的串扰。且影响多阶存储的可分阶性;实验结果很好地验证了所建立的模型的合理性。     

Nondestructive readout of a three-dimensional photochromic optical memory with a near-infrared differential phase-contrast microscope

A three-dimensional (3D) rewritable optical memory using photochromic material is described for high-density memory. The bits are recorded in a 3D volume of photochromic material. A transformation of the photochromic molecule between two isomers with different absorption spectra can be stimulated by irradiation with appropriate wavelengths. We show that a nondestructive readout of photochromic memory is possible by use of a small difference in the refractive index of the photochromic isomers in the near-IR range. For this purpose a near-IR laser-scan differential phase-contrast microscope is used. Experimental results of 3D recording and nondestructive reading are presented.     

Photochromism of dihydroindolizines: part XIV. Synthesis and photophysical behavior of photochromic dihydroindolizine‐tripodal linkers toward anchoring sensitizers to semiconductor nanoparticles

Photochromic dihydroindolizines (DHIs) 4a,5‐dihydropyrrolo[1,2‐b]pyridazine based tripodal‐linker systems with adamantane core and ethyl benzoate tripods as anchoring groups have been successfully synthesized. In addition, new spirocyclopropene precursors have been prepared through both chemical and photochemical processes. The photochromic properties of the newly synthesized DHIs derivatives have been optimized and fine‐tuned by the incorporation of various substituents on the fluorene (region A) and pyridazine (region C) moieties. Several alternative routes for the synthesis of the DHIs under investigation have been established. The Sonogashira crosscoupling reaction was utilized for fragment coupling between DHIs and the phenylacetylene tether of the adamantane core. Several reaction conditions of this key reaction were surveyed to obtain optimal yields of a new series of coupling products targeted for anchoring to semiconductor nanoparticles. The chemical structures of the newly synthesized materials were elucidated by both analytical and spectroscopic tools. Irradiation of the photochromic DHIs with polychromatic light resulted in ring opened colored betaines which underwent cycloreversion reactions via thermal 1,5‐electrocyclization processes. The kinetic of the thermal 1,5‐electrocyclization was studied by using a UV/VIS/NIR spectrophotometer. The kinetic measurements showed the half‐lives of the colored betaines to be in the second domain. A pronounced increase in the half‐lives of betaines bearing dimethyl‐substituted pyridazine was noted compared with non‐substituted pyridazine betaines. A strong effect of solvent polarity on the λ_max and half‐lives of the betaines was observed. The further adjustment of the absorption maxima and the kinetic properties via the manipulation of substituents on the fluorene (region A) and pyridazine moieties (region C) should yield more refined systems for application as supports onto metal‐oxide surfaces which remains an active area of our ongoing research. Copyright © 2010 John Wiley & Sons, Ltd.     

Facile synthesis and photochromic properties of diarylethene‐containing terpyridine and its transition metal (Zn2+/Co2+/Ru2+) complexes

Several transition metal complexes based on 2,3‐bis(2,4,5‐trimethyl‐3‐thienyl)maleic anhydride (DTE) bearing terpyridine (TPY) have been designed and synthesized. Furthermore, the photochromism of the free ligand and the influence of transition metal moieties on the photochemical properties have been thoroughly characterized by monitoring the changes in their UVvis spectra. Compounds 3–6 all display excellent response to UV irradiation, especially Co complex 5 with optimum sensitivity that took only 5 s to reach photostationary state. The photochromic properties of DTE unit have been found to be strongly influenced by the bridging transition metals, as complexes 4 (L–Zn–L) and 6 (L–Ru–L) exhibit much better photochromic properties in tetrahydrofuran solution than complex 5 (L–Co–L) and the free ligand 3 (L). It is worth noting that the optical/chemical thermal stabilities of photochromic compounds 3–6 are all greatly improved after the precursor functionalized with TPY and further coordinated with metal ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Specific features of the CuI nanocrystal structure in photochromic glasses

Physics of the Solid State - The absorption spectra of CuI nanocrystals with an average radii of 5.3 and 6.2 nm in photochromic glass matrix have been studied in the temperature range 38–300...     

Diffraction efficiency of photochromic absorption gratings

Efficiencies of thick photochromic absorption gratings are theoretically investigated. The treatment is based on a realistic photochromic grating model, which includes both spatial and temporal variations of the absorption coefficient. Simple analytic solutions for dynamic diffraction characteristics are derived. This nonlinear model shows that the maximum diffraction efficiency of photochromic absorption gratings may exceed 10%.