Structure and photochromism of polyoxometalates nanoparticles in cross-linked polymer networks

Cross-linked polymer (P(VP-MB)) based on N-vinylpyrrolidone (VP) and N, N′-methylene-bis-acrylamide (MB) was used as polymer matrix to construct photochromic nanocomposite thin films with entrapping the Keggin-type polyoxometalates (POM). The microstructure, photochromic behavior, and mechanism of the films were studied with transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectra (UV-vis), and electron resonance spectra (ESR). The transparent films changed from colorless to blue under UV irradiation. The films showed good reversible photochromism and could recover the colorless state gradually in the air, where oxygen plays an important role during the bleaching process. The heteropolyanions dispersed in composite films uniformly and exhibited strong coulombic interaction with cross-linked polymer. Composite films contained molybdenum had higher photochromic efficiency and slower bleaching reaction than films contained tungsten. According to ESR, the photochromic mechanism was followed by charge-transfer happened between POM and cross-linked polymer.     

Controlled Microstructure and Photochromism of Inorganic-organic Thin Films by Ultrasound

A series of inorganic-organic thin films based on uniformly dispersed nanoparticles of polyoxometalates （POM）entrapped in polyacrylamide （PAM） matrix were prepared by ultrasonic method with different irradiation time.The microstructure, photochromic behavior and mechanism of the films were studied by transmission electron microscopy （TEM）, ultraviolet-visible spectra （UV-VIS） and Fourier transform-infrared spectroscopy （FT-IR）.The microstructure and photochromic properties of the hybrid thin films could be controlled by ultrasound.TEM image revealed that the average size of phosphotungstic acid （PWA） nanoparticles decreased from 20 to 10 nm with the ultrasound irradiation time from 30 to 60 min. After irradiated with ultraviolet light,the transparent films changed from colorless to blue and showed reversible photochromism. The hybrid film, with ultrasound irradiation for 60 min had higher photochromic efficiency and faster bleaching reaction than the one with ultrasound irradiation for 30 min. FT-IR spectra showed that the Keggin geometry of heteropolyoxometalate was still preserved inside the composites, and the interactions between polyanions and polymer matrix increased as the ultrasound time prolonged. It is suggested that the mechanism of the different photochromic properties for the inorganic-organic thin films is the variation of the microstructure and interfacial interactions induced by ultrasound.     

Preparation and photochromism of nanocomposite thin film based on polyoxometalate and polyethyleneglycol

A photochromic nanocomposite based on Keggin structure phosphomolybdic acid (PMoA) well dispersed in polyethyleneglycol (PEG) was fabricated. TEM image showed that PMoA nanoparticles with narrow size distribution were finely dispersed in polymer matrix. FT-IR results showed that the Keggin geometry of polyoxometalates was still preserved inside the composites and strong coulombic interaction was built between PMoA and polymer matrix. Under UV irradiation, the film was reduced photochemically to yield a blue species, which was in accordance with a charge-transfer mechanism.     

Preparation and Photochromic Properties of Hybrid Thin Films Based on Heteropolyoxometallate and Polyacrylamide

A series of photochromic hybrid films were prepared through entrapping Dawson type tungsten heteropolyoxomet-allates(P2W18O62^6-) and molybdenum heteropolyoxometallate(P2Mo18O62^6-) into polyacrylamide matrix.FTIR results showed that the Dawson geometry of heteropolyoxometallates in still preserved inside the composites and strong coulombic interaction is built between heteropolyoxometallates and polyacrylamide via hydrogen bonding.Ir radiated with ultraviolet light ,the transparent films change from colorless to blue and show reversible photochromism.The bleaching process occurs when the films are in contact with air or O2 in the dark.The molybdenum heteropolyoxometallate hybrid film has higher photochromic efficiency and slower bleaching reaction than tungsten heteropolyoxometallate hybrid film.ESR results indicated that polyacrylamide is a hydrogen donor and the photoreduced process is in accordance with the radical mechanism.     

Phosphomolybdic acid-modified highly organized TiO2 nanotube arrays with rapid photochromic performance

TiO₂ nanotube arrays were prepared by means of an electrochemical anodization technique in an organic electrolyte solution doped with polyvinyl pyrrolidone (PVP) and were subsequently modified with phosphomolybdic acid (PMoA) to obtain PMoA/TiO₂ nanotube arrays. The microstructure and photochromic properties were investigated via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). The results indicated that the Keggin structure of PMoA and the nanotube structure of TiO₂ were not destroyed, and there was a strong degree of interaction between PMoA and TiO₂ at the biphasic interface with lattice interlacing during the compositing process. The XPS results further indicated that there was a change in the chemical microenvironment during the formation process of the composite, and a new charge transfer bridge was formed through the Mo-O-Ti bond. Under visible light irradiation, the colorless PMoA/TiO₂ nanotube array quickly turned blue and exhibited a photochromic response together with reversible photochromism in the presence of H₂O₂. After visible light irradiation for 60 s, the appearance of Mo⁵⁺ species in the XPS spectra indicated a photoreduction process in accordance with a photoinduced electron transfer mechanism.     

Synthesis and characterization of polymetalate based photochromic inorganic–organic nanocomposites

A novel reversible photochromic nanocomposite film based on a hybrid inorganic–organic matrix in which heteropolyacid H₃PW₁₂O₄₀ (PWA) was entrapped was prepared. The structure, photochromic behaviors and mechanism of the film were investigated by means of infrared (IR) spectroscopy, UV-Vis absorption spectra and electron spin resonance (ESR). The results showed that heteropolyanion, i.e. PW₁₂O₄₀³⁻ (PW₁₂), maintained a Keggin structure in the film and there was a strong interaction between anion PW₁₂ and cation R–NH₃⁺ (R=link of hybrid composite). The photochromic properties of the composite film originated from the reversible charge transfer between the anions and cations. Under ultraviolet (UV) irradiation, the anion would be reduced via one-electron step with simultaneous oxidation of the cation, accompanied by a color change from colorless to blue. Then the bleaching could occur when the film was in contact with ambient air or O₂ in the dark.     

Characteristics of organic-inorganic hybrid plasma polymer thin films for low-κ ILD applications

This study investigated the effects of plasma power and tetraethylorthosilane (TEOS) to cyclohexene ratios on low-κ organic-inorganic hybrid plasma polymer thin films deposited on silicon (100) substrates. These films were deposited using a plasma enhanced chemical vapor deposition (PECVD) method, in addition to the electrical and mechanical properties of the resulting composites. Cyclohexene and TEOS were used as organic and inorganic precursors, respectively, with hydrogen and argon as precursor bubbler gases. Furthermore, additional argon was used as a carrier gas. The as-grown polymerized thin films were analyzed using ellipsometry, Fourier-transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The ellipsometry results showed the thickness of the hybrid thin film, and the FT-IR spectra showed that the hybrid polymer thin films were completely fragmented and polymerized between cyclohexene and TEOS. AFM results showed that polymer films with a smooth surface could be grown under various deposition conditions, while TEM and XRD showed that the hybrid thin film was an amorphous plasma polymer thin film without porosity. In addition, current-voltage (C-V) curves were prepared to calculate the dielectric constants. Post-annealing was applied to investigate the thermal stability of hybrid plasma polymer thin films in the hardness, Young's modulus, thermal shrinkage, and the dielectric constant at 400 °C.     

Self-assembled PMo12 3-DODA+ composite superlattice thin films with photochromic properties

A layered superlattice PMo₁₂ ^3-DODA⁺ self-assembled composite film has been successfully prepared. Infrared (IR) spectra revealed that the Keggin structure characteristic of the PMo₁₂O₄₀ ^3- anion was preserved in the composite film. A well-ordered superlattice structure, d spacing of 2.945 nm, was identified by X-ray diffraction (XRD). The superlattice film showed good photochromic properties. On irradiation with UV light, the transparent film changed from light yellow to blue. Then, bleaching occurred when the film was in contact with ambient air or O₂ in the dark. The photochromic mechanism was studied by electron spin resonance (ESR), IR spectra, and UV-Vis spectra.     

Ultrasonic-assisted organic–inorganic multilayer thin film synthesis and enhanced visible-light phototropy based on PVP /PMoA

Novel organic–inorganic layer-by-layer (LbL) multilayers for visible-light phototropy, comprised of polyvinylpyrrolidone (PVP) and phosphomolybdic acid (PMoA), were fabricated via layer-by-layer (LbL) assembly with ultrasonic pretreatment. The characterizations revealed that the Keggin spatial geometry of the PMoA was still maintained in the final ultrasonic-assisted LbL thin films, which promoted halogenesis between the PVP and PMoA. Intriguingly, instead of destroying the PVP thin film, the ultrasonic pretreatment process successfully dispersed the PMoA in the PVP thin film with a median size of approximately 3.6 nm. Thanks to the dispersion of the PMoA particles, the photochromic capabilities of the ultrasonic-assisted PVP/PMoA LbL thin films gained remarkable improvement. Moreover, decreasing the size of the PMoA particles to quantum dots (10–3.4 nm) induces an up-conversion and dielectric confinement effect, which increases the intensity of the absorption peak (0.235 increased to 0.45) while narrowing the emission energy (2.51 eV narrowed to 2.23 eV). At the same time, the size reduction also extended the range of the absorption wavelength, increases the characteristic absorption intensity, and accelerates the coloration rate over the same illumination period.

     

含三氯化铁的紫精/聚合物薄膜的光致变色性能和机理研究

紫精/聚合物薄膜光照后产生颜色变化,但褪色缓慢,加入过渡金属离子可以促进薄膜褪色。制备了一种含有三氯化铁的紫精/聚乙烯吡咯烷酮（PVP）光致变色薄膜。三氯化铁的加入消耗薄膜中光照产生的自由基阳离子,使薄膜的颜色变浅,但褪色加快,薄膜的光致变色随着变色/褪色的增加而加深,当三氯化铁和紫精的摩尔比为1∶1时,经过3次变色/褪色循环后,薄膜光照后变色较深,并可褪色至无色;改变三氯化铁的含量和褪色温度,可以调节褪色速率。X射线光电子能谱（XPS）结果表明,光照后的三氯化铁/紫精薄膜中既有Fe＋3也有Fe＋2,由此提出可能的变色机理为Fe＋3从紫色的紫精自由基阳离子夺取电子变成Fe＋2,而紫精退回到无色的二价阳离子态。     

In situ spectroelectrochemistry of poly(N,N'-ethylenebis(salicylideneiminato)Cu(II))

In situ ESR, UV-visible, and FT-IR-ATR spectroelectrochemistry were used to study the charge transfer for electrochemically synthesized poly(N,N'-ethylenebis(salicylideneiminato)Cu(II)), which represents a macromolecular metal chelate with ESR-active central metal ions. Structural evidence for different charged states in electroactive poly(Cu(II)-salen) was obtained from ESR, UV-visible, and FT-IR spectra under reversible redox cycling. The changes in a characteristic broad ESR line without hyperfine splitting originating from Cu(II) as well as in the corresponding UV-visible and infrared spectra are discussed in order to describe an electron transfer to the redox-active sites within the polymer chains in detail.     

基于超分子结构的光电子材料的制备与表征(英文)

为实现短波长光存储材料,提出一种基于金属纳米粒子与染料共掺杂的复合材料制备新方法.采用透射电子显微镜(TEM)、紫外-可见吸收光谱(UV-Vis)以及傅立叶变换红外光谱(FT-IR)对所制备的复合薄膜进行表征.实验发现,与未掺杂银的薄膜相比,掺杂银的复合薄膜中甲基橙的吸收蓝移了6nm.提出并利用超分子结构模型分析了该吸收蓝移的机理.研究结果显示,本研究所提出的这种新的材料制备方法具有制备吸收波长在400～500nm,且可望与GaN激光器在光存储技术中匹配的能力.     

聚乙二醇-碳纳米管(PEG-CNTs)共聚物膜的制备及其微摩擦行为的研究

制备了聚乙二醇接枝碳纳管共聚物(PEG-CNTs)。通过红外光谱(FT-IR)。荧光光谱(FS)和透射电子显微镜(TEM)对共聚物进行了表征。利用旋涂技术以云母为基片制备了共聚物薄膜,采用原子力显微镜／摩擦力显微镜(AFM／FFM)研究了薄膜表面的形貌及微摩擦学行为。复合薄膜内的聚合物组分保证了膜的表面平整,坚硬的碳纳米管组分增强了薄膜的承载能力。     

Self-assembled hybrid films of phosphotungstic acid and aminoalkoxysilanes on SiO2/Si surfaces

The present paper describes the influence of the chemical structure of two aminoalkoxysilanes: 3-aminopropyltriethoxysilane (APTS) and N-(3-(trimethoxysilyl)-propyl)-ethylenediamine (TSPEN) on the morphology of thin layer hybrid films with phosphotungstic acid (HPW), a Keggin heteropolyanion. X-ray photoelectron spectroscopy analyses indicated that both silane films showed protonated amine species interacting with the heteropolyanion by electrostatic forces as well as the presence of secondary carbamate anions. The hybrid films have different surface morphology according to atomic force microscopy analyses. The hybrid film with TSPEN forms flatter surfaces than the hybrid film with APTS. This effect is ascribed to higher flexibility and chelating ability of the TSPEN on adsorbed molecules. Ultrasonication effect on surface morphology of the hybrid film with APTS plays a fundamental role on surface roughness delivering enough energy to promote surface diffusion of the HPW heteropolyanions. This diffusion results in agglomerate formation, which corroborates with the assumption of electrostatic bonding between the HPW heteropolyanions and the protonated amine surface. These hybrid films could be used for electrochemical sensor design or to build photochromic and electrochromic multilayers.     

周期性梯度富硅SiNx薄膜的微结构与发光特性

采用磁控共溅射结合快速光热退火技术在单晶硅和石英衬底上制备了含硅量子点的周期性梯度富硅SiN_x薄膜(梯度薄膜)和单层富硅SiN_x薄膜(单层薄膜)。采用Raman光谱、掠入射X射线衍射(GIXRD)、透射电子显微镜(TEM)、傅里叶变换红外(FTIR)光谱和光致发光(PL)光谱分析了薄膜的结构特性、键合特性和发光特性。Raman光谱、GIXRD和TEM结果表明, 梯度薄膜和单层薄膜中的硅量子点晶化率分别为41.7%和39.2%; 梯度薄膜的硅量子点密度是单层薄膜的5.4倍。FTIR光谱结果显示两种薄膜均为富硅氮化硅薄膜, 梯度薄膜的硅含量小于单层薄膜。PL光谱结果表明梯度薄膜中的辐射复合缺陷少于单层薄膜。     

Microstructural and electrical properties in textured lead calcium lanthanum titanate thin films deposited on a Pt/Ti/SiO2/Si substrate

Textured Ca modified (Pb,La)TiO₃ (PLCT) films were deposited on Pt/Ti/SiO₂/Si substrates using a metal-organic decomposition (MOD) process. The microstructure of the PLCT thin film was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Electric properties were measured using the Pt/PLCT/Pt capacitor structure. The PLCT films exhibit good ferroelectric and dielectric properties.     

A Hydrogel‐Film Casting to Fabricate Platelet‐Reinforced Polymer Composite Films Exhibiting Superior Mechanical Properties

The fabrication of mechanically superior polymer composite films with controllable shapes on various scales is difficult. Despite recent research on polymer composites consisting of organic matrices and inorganic materials with layered structures, these films suffer from complex preparations and limited mechanical properties that do not have even integration of high strength, stiffness, and toughness. Herein, a hydrogel‐film casting approach to achieve fabrication of simultaneously strong, stiff, and tough polymer composite films with well‐defined microstructure, inspired from a layer‐by‐layer structure of nacre is reported. Ca²⁺‐crosslinked alginate hydrogels incorporated with platelet‐like alumina particles are dried to form composite films composed of horizontally aligned alumina platelets and alginate matrix with uniformly layered microstructure. Alumina platelets are evenly distributed parallel without precipitations and contribute to synergistic enhancements of strength, stiffness and toughness in the resultant film. Consequentially, Ca²⁺‐crosslinked alginate/alumina (Ca²⁺‐Alg/Alu) films show exceptional tensile strength (267 MPa), modulus (17.9 GPa), and toughness (3.60 MJ m⁻³). Furthermore, the hydrogel‐film casting allows facile preparation of polymer composite films with controllable shapes and various scales. The results suggest an alternative approach to design and prepare polymer composites with the layer‐by‐layer structure for superior mechanical properties.     

Studies of casting and LB films of ferroelectric liquid crystalline polysiloxane

Monolayers of side chain ferroelectric liquid crystalline polysiloxane have been successively transferred onto appropriate substrates by vertical dipping method to study the morphology and the orientation of the mesogens and the side chains by UV spectra and polarized FT-IR spectra and X-ray diffraction. The spectra for casting film and LB film are compared. The molecules in LB films are found to be more orientated along the normal of the substrate at an angle of 37° for the mesogens as the side chain as found by polarized FT-IR spectra and transmitting FT-IR spectra than casting film. Layer structure is also confirmed by X-ray diffraction results. The mesogens are found to form H-aggregates structure in bulk phase and LB films from UV spectra. Temperature-dependent UV spectra have revealed the change of the tilt angle of the mesogens inside the layer of both bulk phase and LB films.     

Preparation of Pb0.98La0.02(Zr0.65Ti0.35)O3 films and their fine patterning

The photosensitive lanthanum-doped lead zirconate titanate (PLZT) gel films were prepared by chemical modification with acetylacetone (AcAcH), and their fourier transform infrared (FT-IR) spectra and ultraviolet visible (UV-Vis) spectra were measured. The results show that the chelate rings of AcAcH with Ti or Zr are formed in the PLZT gel films. With irradiation of UV light, the chelate rings are photolyzed, and lead to a change of the solubility of the PLZT gel films in methanol. Transmission electron microscope (TEM) observations show that the perovskite phase is crystallized in PLZT thin film after heat treatment at 700 °C, whose grain sizes are less than or equal to 60 nm. The PLZT thin films exhibited hysteresis loops and good fatigue properties.     

激光化学气相反应生长Ti（C,N）薄膜的成分及微观结构

运用ＸＲＤ，ＥＰＭＡ，ＴＥＭ等手段分析在Ｔｉ－６Ａｌ－４Ｖ基材上用激光化学气相色反应生长的Ｔｉ（Ｃ，Ｎ）薄膜的成分，结构，显微结构，可在基材表面的形成大面积均匀的Ｔｉ（Ｃ，Ｎ）膜层，为无明显择优取向的等轴纳米晶，其中有少量的Ｔｉ２Ｎ相，且Ａｌ，Ｖ含量低于基材。