Nanoscale NiAl-NO3-LDHs with good crystallinity have been synthesized by a method, Separate Nucleation and Aging Steps (SNAS). An NiAl-NO3-LDHs/LDPE composite was prepared by blending NiAl-NO3-LDHs and LDPE in a heate...Nanoscale NiAl-NO3-LDHs with good crystallinity have been synthesized by a method, Separate Nucleation and Aging Steps (SNAS). An NiAl-NO3-LDHs/LDPE composite was prepared by blending NiAl-NO3-LDHs and LDPE in a heated double-roller mixer. The color of this composite changed from olive green to steel gray under UV irradiation. After heating at 80oC for 2 h, the color returned to olive green. The effect of varying the amount of added NiAl-NO3-LDHs and UV exposure time on the photochromic properties of the composite has been investigated. The results showed that the photochromic phenomenon becomes more apparent with increasing amount of NiAl-NO3-LDHs. When the amount reaches 5%, the composite exhibits good photochromic properties and reproducibility. The color change rate of the composite reaches a maximum when the irradiation time exceeds 20 min. The addition of LDPE improves the photochromic cyclability of NiAl-NO3-LDHs significantly. The addition of nanoscale NiAl-NO3-LDHs also improves the mechanical properties of LDPE to some extent.展开更多
TiO_2 sol-gel composite films with dropping molybdenumphosphoric acid(PMoA) have been prepared by sol-gel method.The structure and constitute of composite thin films were studied with Fourier transforms infrared spect...TiO_2 sol-gel composite films with dropping molybdenumphosphoric acid(PMoA) have been prepared by sol-gel method.The structure and constitute of composite thin films were studied with Fourier transforms infrared spectroscopy(FT-IR),atomic force microscopy(AFM),and X-ray diffraction(XRD) patterns,respectively.The photochromic behavior and mechanism of composite thin films were inves-tigated with ultraviolet-visible spectra(UV-vis) and electron spin resonance(ESR).FT-IR results showed that the Keggin geometry of PMoA was still preserved inside PMoA/TiO2 composite thin films,and a charge transfer bridge was built at the interface of PMoA and TiO2 through the Mo-O-Ti bond.Surface topography of the composite film showed obvious changes before/after adding PMoA,and the surface topography of composite films showed obvious changes before/after irradiating as well.Composite thin film had reversible photochromic properties.Irradiated with UV light,transparent films changed from colorless to blue and they can bleach completely with ambient air in the dark.ESR re-sults showed that TiO_2 were excitated by UV light to produce electrons,which deoxidized PMoA to produce heteropolyblues.The photochromic process of PMoA/TiO_2 system was carried through elec-tron transfer mechanism.展开更多
Novel photochromic composite films have been successfully fabricated by dispersing pyrazolone derivative:1,3-Diphenyl-4-(3-chlorobenzal)-5-hydroxypyrazole 4-phenylsemicarbazone(la) into hydrosol of polyvinyl alco...Novel photochromic composite films have been successfully fabricated by dispersing pyrazolone derivative:1,3-Diphenyl-4-(3-chlorobenzal)-5-hydroxypyrazole 4-phenylsemicarbazone(la) into hydrosol of polyvinyl alcohol(PVA).The microstructure,photochromic behaviors and thermal bleaching properties were investigated by Raman spectroscopy,X-ray powder diffraction(XRD),field emission scanning electron microscopy(FE-SEM) and ultraviolet-visible absorption spectroscopy(UV-vis).The results showed that la was not only blended but also well dispersed in the PVA polymer films with a suitable content of chromophore.Upon UV light irradiation,the composite films gradually changed from colorless to yellow and recovered fully to the initial state upon thermal bleaching.The time constants of photochromic reactions were almost the same as those of la observed in their crystalline state,indicating that the photochromic phenomenon is barely disturbed by the polymer matrix.展开更多
Nonanethiol capped gold nanoparticles were firstly used to modify the surface of MoO 3 thin films in order to fabricate the MoO 3/Au composite thin film. Absorption experiments and XPS measurements were used to invest...Nonanethiol capped gold nanoparticles were firstly used to modify the surface of MoO 3 thin films in order to fabricate the MoO 3/Au composite thin film. Absorption experiments and XPS measurements were used to investigate the effect of Au nanoparticles on the photochromic properties of the composite thin film. According to the XPS measurements, the binding energy for the valence band(O 2p ) of the composite thin films decreased. The experimental results of absorbance showed that the photochromic efficiency for the composite thin films became at least as two times as that of MoO 3 thin films. The mechanism of enhancement can be explained by the band energy theory of semiconductor. The Schottky barrier formed at the interface prolonged the electron hole pair separation lifetime and resulted in the enhancement of the photochromic efficiency.展开更多
Using tetraethoxysilane and 3-aminopropyltriethoxysilane as the silica sources, amino-functionalized organic/inorganic hybrid mesoporous silica thin films with 2-dimensional hexagonal structure have been synthesized b...Using tetraethoxysilane and 3-aminopropyltriethoxysilane as the silica sources, amino-functionalized organic/inorganic hybrid mesoporous silica thin films with 2-dimensional hexagonal structure have been synthesized by evaporation induced self-assembly process in the presence of cetyltrimethyl ammonium bromide templates under acid conditions. The Keggin-type molybdphosphoric acid (PMo) is incorporated into the mesoporous silica thin films with amino-groups by wetness impregnation, and the PMo/silica mesoporous composite thin films are obtained. The results of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FTIR) spectra indicate the PMo molecules maintain Keggin structure and are homogeneously distributed inside mesopores. The composite thin films possess excellent reversible photochromic properties, and change from colorless to blue under ultraviolet irradiation. The photochromic mechanism of the composite thin films is studied by ultraviolet-visible (UV-vis), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) spectra. It is shown that intervalence charge transfer (IVCT) and ligand-to-metal charge transfer (LMCT) are the main reasons of photochromism. PMo anions interact strongly with amino-groups of the mesoporous suface via hydrogen bond and electrostatic force. After ultraviolet irradiation, the charge transfer occurs by reduction of heteropolyanions accompanying the formation of heteropolyblues with multivalence Mo(VI, V), and the bleaching process of composite thin films is closely related to the presence of oxygen.展开更多
Photochromic polymolybdate-citric acid composite films were fabricated. It was found that after UV irradiation the composite films with different molar ratios of organic/inorganic components exhibited different colors...Photochromic polymolybdate-citric acid composite films were fabricated. It was found that after UV irradiation the composite films with different molar ratios of organic/inorganic components exhibited different colors. The UV-irradiated films showed dark blue, dark khaki and light sea green colors when the ratios were 1.0, 0.3 and 0.2, respectively. It was identified by Raman spectra that the polymolybdate species formed in the composite films after UV irradiation were sensitive to the ratios of the organic/inorganic components, thus resulting in the different colors of irradiated films. Citric acid played an important role during the photochromic process. Under UV light irradiation, it served as hole scavenger that suppresses the recombination of photogenerated electrons and holes to make the polymolybdates show UV light photochromism.展开更多
基金Supported by the National Basic Research Program of China (973 program) (Grant No. 2004CB720602)the National Natural Science Foundation of China (Grant No. 20471006)the Key Project of the National Natural Science Foundation of China (Grant No. 90306012)
文摘Nanoscale NiAl-NO3-LDHs with good crystallinity have been synthesized by a method, Separate Nucleation and Aging Steps (SNAS). An NiAl-NO3-LDHs/LDPE composite was prepared by blending NiAl-NO3-LDHs and LDPE in a heated double-roller mixer. The color of this composite changed from olive green to steel gray under UV irradiation. After heating at 80oC for 2 h, the color returned to olive green. The effect of varying the amount of added NiAl-NO3-LDHs and UV exposure time on the photochromic properties of the composite has been investigated. The results showed that the photochromic phenomenon becomes more apparent with increasing amount of NiAl-NO3-LDHs. When the amount reaches 5%, the composite exhibits good photochromic properties and reproducibility. The color change rate of the composite reaches a maximum when the irradiation time exceeds 20 min. The addition of LDPE improves the photochromic cyclability of NiAl-NO3-LDHs significantly. The addition of nanoscale NiAl-NO3-LDHs also improves the mechanical properties of LDPE to some extent.
文摘TiO_2 sol-gel composite films with dropping molybdenumphosphoric acid(PMoA) have been prepared by sol-gel method.The structure and constitute of composite thin films were studied with Fourier transforms infrared spectroscopy(FT-IR),atomic force microscopy(AFM),and X-ray diffraction(XRD) patterns,respectively.The photochromic behavior and mechanism of composite thin films were inves-tigated with ultraviolet-visible spectra(UV-vis) and electron spin resonance(ESR).FT-IR results showed that the Keggin geometry of PMoA was still preserved inside PMoA/TiO2 composite thin films,and a charge transfer bridge was built at the interface of PMoA and TiO2 through the Mo-O-Ti bond.Surface topography of the composite film showed obvious changes before/after adding PMoA,and the surface topography of composite films showed obvious changes before/after irradiating as well.Composite thin film had reversible photochromic properties.Irradiated with UV light,transparent films changed from colorless to blue and they can bleach completely with ambient air in the dark.ESR re-sults showed that TiO_2 were excitated by UV light to produce electrons,which deoxidized PMoA to produce heteropolyblues.The photochromic process of PMoA/TiO_2 system was carried through elec-tron transfer mechanism.
基金supported by the National Natural Science Foundation of China (Nos. 21262038, 21571152 and U1203292)National 973 Program on Key Basic Research Project of China (No. 2014CB660805)the Outstanding Youth Natural Science Foundation of Xinjiang Uygur Autonomous Region of China (No. 201311006)
文摘Novel photochromic composite films have been successfully fabricated by dispersing pyrazolone derivative:1,3-Diphenyl-4-(3-chlorobenzal)-5-hydroxypyrazole 4-phenylsemicarbazone(la) into hydrosol of polyvinyl alcohol(PVA).The microstructure,photochromic behaviors and thermal bleaching properties were investigated by Raman spectroscopy,X-ray powder diffraction(XRD),field emission scanning electron microscopy(FE-SEM) and ultraviolet-visible absorption spectroscopy(UV-vis).The results showed that la was not only blended but also well dispersed in the PVA polymer films with a suitable content of chromophore.Upon UV light irradiation,the composite films gradually changed from colorless to yellow and recovered fully to the initial state upon thermal bleaching.The time constants of photochromic reactions were almost the same as those of la observed in their crystalline state,indicating that the photochromic phenomenon is barely disturbed by the polymer matrix.
文摘Nonanethiol capped gold nanoparticles were firstly used to modify the surface of MoO 3 thin films in order to fabricate the MoO 3/Au composite thin film. Absorption experiments and XPS measurements were used to investigate the effect of Au nanoparticles on the photochromic properties of the composite thin film. According to the XPS measurements, the binding energy for the valence band(O 2p ) of the composite thin films decreased. The experimental results of absorbance showed that the photochromic efficiency for the composite thin films became at least as two times as that of MoO 3 thin films. The mechanism of enhancement can be explained by the band energy theory of semiconductor. The Schottky barrier formed at the interface prolonged the electron hole pair separation lifetime and resulted in the enhancement of the photochromic efficiency.
基金Supported by the National High Technology Research and Development Program of China (Grant No. 2003AA005017)Advanced Research Foundation of Na-tional University of Defense Technology (Grant No. CX06-01-06)
文摘Using tetraethoxysilane and 3-aminopropyltriethoxysilane as the silica sources, amino-functionalized organic/inorganic hybrid mesoporous silica thin films with 2-dimensional hexagonal structure have been synthesized by evaporation induced self-assembly process in the presence of cetyltrimethyl ammonium bromide templates under acid conditions. The Keggin-type molybdphosphoric acid (PMo) is incorporated into the mesoporous silica thin films with amino-groups by wetness impregnation, and the PMo/silica mesoporous composite thin films are obtained. The results of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FTIR) spectra indicate the PMo molecules maintain Keggin structure and are homogeneously distributed inside mesopores. The composite thin films possess excellent reversible photochromic properties, and change from colorless to blue under ultraviolet irradiation. The photochromic mechanism of the composite thin films is studied by ultraviolet-visible (UV-vis), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) spectra. It is shown that intervalence charge transfer (IVCT) and ligand-to-metal charge transfer (LMCT) are the main reasons of photochromism. PMo anions interact strongly with amino-groups of the mesoporous suface via hydrogen bond and electrostatic force. After ultraviolet irradiation, the charge transfer occurs by reduction of heteropolyanions accompanying the formation of heteropolyblues with multivalence Mo(VI, V), and the bleaching process of composite thin films is closely related to the presence of oxygen.
基金Project supported by the National Natural Science Foundation of China (Nos. 50221201, 90301010, 20373077 and 20471062), the Chinese Academy of Sciences and the National Research Fund for Fundamental Key Projects No. 973.
文摘Photochromic polymolybdate-citric acid composite films were fabricated. It was found that after UV irradiation the composite films with different molar ratios of organic/inorganic components exhibited different colors. The UV-irradiated films showed dark blue, dark khaki and light sea green colors when the ratios were 1.0, 0.3 and 0.2, respectively. It was identified by Raman spectra that the polymolybdate species formed in the composite films after UV irradiation were sensitive to the ratios of the organic/inorganic components, thus resulting in the different colors of irradiated films. Citric acid played an important role during the photochromic process. Under UV light irradiation, it served as hole scavenger that suppresses the recombination of photogenerated electrons and holes to make the polymolybdates show UV light photochromism.