Organic-inorganic Composite Films Research Articles

Effects of germanium content on the optical properties of GeO2-based organic-inorganic composite films doped with azobenzene

Organic-inorganic composite materials have great applications in integrated optics due to their good optical performance. In this study, GeO2-based organic-inorganic composite films doped with azobenzene were prepared by combining the solgel technique and the spin-coating method. The optical waveguide properties including the refractive index and film thickness and the optical response properties of the composite films with different germanium contents have been investigated. The results indicate that the refractive index of the film increases, but the film thickness decreases as the germanium content increases. The composite film with 0.2 mol of germanium exhibits the best optical response properties. Further, the optical switching characteristics of the optimal composite film shows good stability and reversibility. The photochemical and structural properties of the film were also investigated by using Fourier transform infrared spectroscopy and thermo-gravimetric analysis. Finally, hexagonal microlens arrays were built in the film by using the UV nanoimprint technique, resulting in neatly arranged structures with good optical imaging performance.

One-step formation of three-dimensional interconnected T-shaped microstructures inside composites by orthogonal bidirectional self-assembly method

ABSTRACT The fillers inside a polymer matrix should typically be self-assembled in both the horizontal and vertical directions to obtain 3-dimentional (3D) percolation pathways, whereby the fields of application can be expanded and the properties of organic-inorganic composite films improved. Conventional dielectrophoresis techniques can typically only drive fillers to self-assemble in only one direction. We have devised a one-step dielectrophoresis-driven approach that effectively induces fillers self-assembly along two orthogonal axes, which results in the formation of 3D interconnected T-shaped iron microstructures (3D-T CIP) inside a polymer matrix. This approach to carbonyl iron powder (CIP) embedded in a polymer matrix results in a linear structure along the thickness direction and a network structure on the top surface of the film. The fillers in the polymer were controlled to achieve orthogonal bidirectional self-assembly using an external alternating current (AC) electric field and a non-contact technique that did not lead to electrical breakdown. The process of 3D-T CIP formation was observed in real time using in situ observation methods with optical microscopy, and the quantity and quality of self-assembly were characterized using statistical and fractal analysis. The process of fillers self-assembly along the direction perpendicular to the electric field was explained by finite element analogue simulations, and the results indicated that the insulating polyethylene terephthalate (PET) film between the electrode and the CIP/prepolymer suspension was the key to the formation of the 3D-T CIP. In contrast to the traditional two-step method of fabricating sandwich-structured film, the fabricated 3D-T CIP film with 3D electrically conductive pathways can be applied as magnetic field sensor.

Multifunctional organic corncob lignin and inorganic lithium nitride composite films as artificial protective layer to achieve high-performance Li metal anodes

Multifunctional organic corncob lignin and inorganic lithium nitride composite films as artificial protective layer to achieve high-performance Li metal anodes

PMMA-doped composite films microlens arrays on a flexible substrate for improving extraction of an organic light-emitting diode.

Poly (methyl methacrylate) (PMMA)-doped organic-inorganic composite films are prepared on flexible substrates through a combination of the sol-gel technique and the spin-coating method. Circular and hexagonal microlens arrays (MLAs) are then built into the composite films by using ultraviolet nanoimprint technology. Atomic force microscope and ultraviolet spectrophotometer characterization results of the films show that the films have low surface roughness and good optical transmittance. A scanning electron microscope is used to observe the surface morphology of the MLAs, and the results show that the prepared MLAs are regular and neat. The surface profiles of the MLAs are also measured by using a surface profiler. Optical microscopy results show that the prepared MLAs have good optical imaging properties. Finally, the MLAs are applied on the green organic light-emitting diodes (OLEDs), and the influence of the shape and diameter of the MLAs on the luminance and current efficiency of the OLEDs is discussed. Results indicate that there is a relatively high enhancement of the current efficiency and luminance for the OLEDs with hexagonal MLAs and a single microlens height of 9 µm, where the luminance can reach 10611cd/cm2, and the current efficiency can be enhanced by about 20.1%. Furthermore, there is a higher enhancement of the luminance and current efficiency for the OLEDs with PMMA-doped MLAs than that of the OLEDs with no PMMA-doped MLAs. Based on these results, we believe that the obtained PMMA-doped composite film MLAs on flexible substrates have important applications in the flexible OLEDs displays areas.

High-Performanced Hemicellulose Based Organic-Inorganic Films with Polyethyleneimine.

For the high-value utilization of hemicellulose-based composite films, the poor film-forming and mechanical properties of hemicellulose-based composite films must be surmounted crucially. Based on this, hemicellulose-based organic-inorganic composite films with good mechanical properties were prepared from quaternized hemicelluloses (QH), bentonite, and polyethyleneimine (PEI). The QH/PEI/bentonite composite films were prepared by vacuum filtration, and the properties of the composite film were investigated. The results showed that the QH was inserted into bentonite nanosheets through hydrogen bonding and electrostatic interactions. PEI was cross-linked with hemicellulose by hydroxyl groups, electrostatically attracted by the bentonite flake layers. The mechanical properties of the composite films were significantly increased by the incorporation of PEI. When the PEI content was 20%, the tensile stress of the composite film was increased by 155.18%, and the maximum tensile stress was reached 80.52 MPa. The composite films had strong UV absorption ability with the transmittance was almost 0 in the UV region from 200 to 300 nm. The thermal property of composite film was also improved, and the residual mass increased by three times compared to QH. These results provide a theoretical basis for the use of hemicellulose-based composite films in packaging applications.

Optical Isomerization and Photo-Patternable Properties of GeO2/Ormosils Organic-Inorganic Composite Films Doped with Azobenzene

GeO2/organically modified silane (ormosils) organic-inorganic composite films containing azobenzene were prepared by combining sol-gel technology and spin coating method. Optical waveguide properties including the refractive index and thickness of the composite films were characterized by using a prism coupling instrument. Surface morphology and photochemical properties of the composite films were investigated by atomic force microscope and Fourier transform infrared spectrometer. Results indicate that the composite films have smooth and neat surface, and excellent optical waveguide performance. Photo-isomerization properties of the composite films were studied by using a UV–Vis spectrophotometer. Optical switching performance of the composite films was also studied under the alternating exposure of 365 nm ultraviolet light and 410 nm visible light. Finally, strip waveguides and microlens arrays were built in the composite films through a UV soft imprint technique. Based on the above results, we believe that the prepared composite films are promising candidates for micro-nano optics and photonic applications, which would allow directly integrating the optical data storage and optical switching devices onto a single chip.

Titanium content influence on the optical response characteristics of TiO2/ormosils composite films doped with azobenzene.

TiO2-based organic-inorganic composite films doped with azobenzene and photosensitive groups were prepared by combining a low-temperature solgel technique and a spin-coating method. The influence of TiO2 content on the optical and structural properties of the composite films including the film thickness, the refractive index, the transmission loss, the thermal gravity analysis, and Fourier transform infrared spectroscopy spectra was studied. Photoisomerization and optical switching characteristics of the composite film were investigated under the irradiation of 365 nm ultraviolet light and 450 nm visible light. Results indicate that several micrometer thick films can be easily obtained at room temperature and there is a proportional relationship between the refractive index value and the TiO2 content. In addition, the composite films have a low optical propagation loss of about 0.1 dB/cm. The composite films with 0.2 M TiO2 content have an obvious photoisomerization and good optical switching properties. Finally, the hexagonal microlens array was fabricated in the composite films by using an ultraviolet nanoimprint technology. All these results above indicate that the as-prepared TiO2-based organic-inorganic composite film has potential applications in optical switching devices and photonic elements.

Development of geopolymer derived from slag waste based composite film on cotton fabric: A preliminary approach for flame retardant behavior

Organic-inorganic hybrid composite films with a geopolymer and organic polymers (sodium polyacrylate, polytetrafluorethylene, and polyurethane) were prepared using a facile method for application as flame retardant coatings. The geopolymer paste was successfully synthesized by adding a mixture of metakaolin and slag into an alkali solution. The structural and morphological properties of the barrier films were investigated using Fourier-transform infrared spectroscopy and scanning electron microscopy. The films showed the Si-O and Si-Al peaks characteristic of the geopolymer. The microstructural examination revealed that the films consisted of irregular particles. With an increase in the geopolymer amount, the flexural and compressive strengths of the samples decreased. The tensile strength, thermogravimetric analysis and flame retardant properties of the composite paste were investigated. The films showed a tensile strength of 0.15–0.30 MPa. The composite film coated onto cotton surface was thermally stable up to 200 °C. The cotton (C) and the mixture of cotton and polyester (M) substrates coated with the barrier film showed the char lengths of 5–8 and 4–7 cm, respectively. The geopolymers synthesized using slag and metakaolin exhibited excellent flame retardant properties on the cotton fabric. Hence, these films were found to be promising candidates for flame retardant applications.

Ferroelectric polarization effect promoting the bulk charge separation for enhance the efficiency of photocatalytic degradation

Focused on the separation of photoinduced carriers to improve the photocatalytic performance of semiconductors, polarized C/Bi/Bi2MoO6 were synthesized by electrical polarizing method in presence of organic–inorganic composite films. Significantly, this poling process leads to the better photoactivity for degrade bisphenol A (BPA) and ciprofloxacin (CIP), catalyzing the generation of superoxide radicals (•O2–) and holes (h+) to removal pollutants either through the ferroelectric polarization effect. Meanwhile, the non-destructiveness during the entire polarization process helps maintain the crystal structure and morphology of the catalyst to achieve better photocatalytic performance. This present work not only provides a great route for preparation of various polarized ferroelectric semiconductors, but also indicates the potential of ferroelectric polarization for modification of semiconductors.

Enhanced Capture of Broadband Solar‐Blind UV Light via Introducing Alkali‐Metal Ions (Li+, Na+, and K+) into DC Spectral Converter

AbstractRare earth doped down‐conversion (DC) materials, due to their unique spectral conversion characteristics, are promising candidates for narrow band solar‐blind ultraviolet (UV) light detection devices. Herein, an enhanced capture device for broadband solar‐blind UV light is constructed by combining an ordinary semiconductor with a DC spectrum converter, the essence of which is to introduce the appropriate alkali‐metal ions (Li+, Na+, and K+) into DC layer. Europium‐doped organic–inorganic composite films are used as spectral converters because of their excellent DC characteristic, which can convert broadband solar‐blind UV incident illumination into visible light suitable for capture by light dependent resistor (LDR). Interestingly, the spectral conversion efficiency is positively correlated with the capture ability of broadband solar‐blind UV photons. The introduction of alkali‐metal ions in the DC layer enhances the photon detection efficiency with an increase rate of around 200%, which is attributed to alkali‐metal ions changing the local crystal field symmetry around the Eu3+emitter and distorting the matrix crystal of Y2O3, thus increasing the probability of intra‐4felectron transition. These results signify that the present rare‐earth doped DC luminescent materials are promising building blocks for assembly of high‐performance broadband solar‐blind UV detector.

Up-conversion luminescence of neodymium oxide nanocrystals-doped TiO2/ormosils composite films and strip waveguides

Neodymium oxide nanocrystals are synthesized by an inverse microemulsion method. XRD, XPS and HRTEM are used to characterize the properties of the neodymium oxide nanocrystals. Results show that the prepared neodymium oxide particles have obvious "column” structure with a column width of 400 ~ 600 nm and a length of 1 ~ 4 µm and have nanocrystalline structure with a high crystallinity. Neodymium-doped TiO2/organically modified silanes (ormosils) organic–inorganic composite films were prepared by using a sol–gel spin coating method. Up-conversion emission and optical transmittance of the films baked at different temperature were studied. Results indicate that the up-conversion emission occurs at about seven wavelength numbers of 387, 404, 421, 436, 450, 478 and 487 nm, of which the bright blue emission at 436 nm has the strongest intensity. There is a high optical transmittance value of above 88% for all the samples in the wavelength number 500 ~ 1000 nm. Optical waveguide properties including the optical transmission modes and loss of the composite films were measured. The photochemical properties of the composite films were also demonstrated by FTIR spectra. Besides, an energy level diagram was used to explain the mechanism of the up-conversion emission from neodymium oxide nanocrystals. Finally, strip waveguides with different waveguide sizes were built in the composite films through a UV soft nanoimprint technique and the surface morphology of the waveguides was observed by SEM. The as-prepared neodymium-doped composite films have potential applications in the areas of photonics and micro-optical devices.

Temperature-dependent dielectric properties of metal-doped ZnO nanofiller reinforced PVDF nanocomposites

Here, we report on the successful fabrication of organic-inorganic composite films with poly (vinylidene fluoride) (PVDF) polymer and calcium doped zinc oxide (CaZ) and cadmium doped zinc oxide (CdZ) as two different nanofillers. The incorporation of these nanofillers resulted in increased crystalline and piezoelectric β-phase content of PVDF composites. The comparison of temperature-dependent dielectric studies showed enhanced dielectric properties of CaZ-loaded PVDF composites compared to CdZ-based PVDF composites. At 1 kHz, a maximum dielectric permittivity of 26.13 with a dielectric loss of 0.477 was obtained for 10 wt% CaZ-loaded PVDF composite film (10 CaZ-P) at 100 °C. The relaxation time of as-prepared composites showed Arrhenius behavior and lower activation energy for 10 CaZ-P composites (66.24 kJ/mol). For the 10 CaZ-P composite films, the AFM topography analysis showed higher roughness value (16.54 nm) and confirmed the lower activation energy of the same.

TiN-based organic-inorganic composite films with dual functions of solar control and low-emission for energy-saving coatings

With the fast development of modern intelligent buildings, the demand for a comfortable environment and ‘low carbon’ technologies, for example, energy-saving buildings, becomes more intense. Thermal insulation coatings as one of the most promising routes to alleviate the energy consumption of buildings attract extensive attention in recent years. In this work, titanium nitride-based organic-inorganic composite films (TiN O/I films) were introduced as the thermal insulation coatings to window glass via blade coating method. Additionally, two different synthesis methods were adopted to prepare the inorganic TiN nanoparticle and its effect on the optical property of the coatings was studied detailedly via the ultraviolet-visible-near-infrared (UV–vis-IR) spectrophotometer and Fourier transform infrared spectrometer characterizations. In addition, the thermal insulation properties of the films were characterized by a system that simulates the natural environment. Various characterizations show that the synthesized TiN O/I films can not only pass through the visible light but also has high reflectance at the mid-infrared range, that is with the functions of solar control and low emission, well satisfying the requirements of the energy-saving coatings for window glass. These results demonstrated the good feasibility of TiN O/I films in thermal insulation coatings, and also provide a direction for the development of more novel thermal insulation materials with large-scale.

Transparent MoS2/PEDOT Composite Counter Electrodes for Bifacial Dye-Sensitized Solar Cells.

Dye-sensitized solar cells (DSSCs) are solar energy conversion devices with high efficiency and simple fabrication procedures. Developing transparent counter electrode (CE) materials for bifacial DSSCs can address the needs of window-type building-integrated photovoltaics (BIPVs). Herein, transparent organic–inorganic hybrid composite films of molybdenum disulfide and poly(3,4-ethylenedioxythiophene) (MoS2/PEDOT) are prepared to take full advantage of the conductivity and electrocatalytic ability of the two components. MoS2 is synthesized by hydrothermal method and spin-coated to form the MoS2 layer, and then PEDOT films are electrochemically polymerized on top of the MoS2 film to form the composite CEs. The DSSC with the optimized MoS2/PEDOT composite CE shows power conversion efficiency (PCE) of 7% under front illumination and 4.82% under back illumination. Compared with the DSSC made by the PEDOT CE and the Pt CE, the DSSC fabricated by the MoS2/PEDOT composite CE improves the PCE by 10.6% and 6.4% for front illumination, respectively. It proves that the transparent MoS2/PEDOT CE owes superior conductivity and catalytic properties, and it is an excellent candidate for bifacial DSSC in the application of BIPVs.

Robust Organic–Inorganic Composite Films with Multifunctional Properties of Superhydrophobicity, Self-Healing, and Drag Reduction

Multifunctional films have attracted wide attention in scientific research and engineering applications. Based on thermodynamically driven metathesis reactions of disulfide bonds, a self-healing fi...

Influence of nanosilica on inner structure and performance of chitosan based films

Chitosan based organic-inorganic composite films were prepared through direct incorporation of nanosilica particles in order to enhance their performance for potential packaging material. After the addition of nanosilica, the viscosity of film-forming solutions (FFSs) decreased obviously, and the G’ of FFS with 25% of nanosilica was higher than that of other FFSs with nanosilica. In low field nuclear magnetic resonance (LF-NMR) determination, the addition of 25% of nanosilica gave rise to the lowest relaxation time and peak area proportion of T21 component. Additionally, the changes of structure characteristic of composite films with different nanosilica content were analyzed through FTIR spectroscopy, SEM and XRD analysis. The thermal stability of films improved markedly with increasing nanosilica. The optimal mechanical properties of films were yielded at 25% of nanosilica. Furthermore, the introduction of nanosilica significantly (p < 0.05) decreased the swelling ratio of chitosan based films at pH 7.6 and pH 2.6.

Constructing non-fluorinated porous superhydrophobic SiO2-based films with robust mechanical properties

We present a cost-effective and environmentally friendly fabrication route for fluorine-free superhydrophobic SiO2-based films with robust mechanical properties on various substrates including soda-lime glass, fabric, paper and aluminium flake. The superhydrophobic dispersion is achieved by modifying the SiO2 nanoparticles (NPs) with hexamethyl disilazane (HMDS), in which the SiO2 NPs are derived from base catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS). The water contact angle (CA) and sliding angle (SA) of the dip-coated films from the HMDS-modified SiO2 NPs reache ∼170° and about 2°, respectively. We particularly present a facile route to greatly enhance the mechanical durability without noticeable lossing the superhydrophobicity of the films by mixing different size ranges of SiO2 NPs in the presence ofhydroxy acrylic resin (HAR). The synthesized SiO2-based organic-inorganic composite superhydrophobic films display excellent self-cleaning properties even after 100 cycles of sandpaper abrasion. Combined with the excellent superhydrophobic properties and the robust mechanical properties, the present procedure provides a facile and cost-effective synthetic protocol of constructing surfaces for not only durable self-cleaning and antifouling devices but also anti-corrosion applications.

Rationally Designed, Multifunctional Self-Assembled Nanoparticles for Covalently Networked, Flexible and Self-Healable Superhydrophobic Composite Films

For constructing bioinspired functional films with various superhydrophobic functions, including self-cleaning, anticorrosion, antibioadhesion, and oil-water separation, hydrophobic nanomaterials have been widely used as crucial structural components. In general, hydrophobic nanomaterials, however, cannot form strong chemical bond networks in organic-inorganic hybrid composite films because of the absence of chemically compatible binding components. Herein, we report the rationally designed, multifunctional self-assembled nanoparticles with tunable functionalities of covalent cross-linking and hydrophobicity for constructing three-dimensionally interconnected superhydrophobic composite films via a facile solution-based fabrication at room temperature. The multifunctional self-assembled nanoparticles allow the systematic control of functionalities of composite films, as well as the stable formation of covalently linked superhydrophobic composite films with excellent flexibility (bending radii of 6.5 and 3.0 mm, 1000 cycles) and self-healing ability (water contact angle > 150°, ≥10 cycles). The presented strategy can be a versatile and effective route to generating other advanced functional films with covalently interconnected composite networks.

A novel hydrophilic pyridinium salt polymer/SWCNTs composite film for high thermoelectric performance

Polymer/carbon nanotube composites have gained great progress in the past decade. However, the lack of scalability of production due to the relatively high volatility and strong toxicity of the dispersion solvent have created a great need for environmental friendly process for expanding TE applications. In this work, organic-inorganic composite films composed of a novel hydrophilic pyridinium salt polymer (noted as P2) and SWCNTs were prepared for thermoelectric application. The novel hydrophilic pyridinium salt polymer was designed and synthesized containing the pyridinium salt for aqueous dissolution and thiophenes as the conjugation group to make the polymer/CNT composite film electrical connecting, therefore improving the thermoelectric performance. Another pyridinium salt polymer (noted as P1) without thiophene group was also synthesized for the purpose of comparison. The polymers attach on the surface of CNTs through π-π conjugation interaction between conjugation groups and π-electrons of CNTs. The P2/CNT composites were homogeneously dispersed in the aqueous solution, revealing better dispersion behavior than P1/CNT, which is probably because of the stronger contact interaction between P2/CNT than P1/CNT due to the higher electron delocalization of polymer P2 than P1. The electrical conductivity of P2/CNT composite film reached the maximum value of 159 S/cm with 50% CNT content. Consequently, a high power factor of 46.4 μW/mK2 was obtained for the P2/50%CNT composite film.

Ionic Liquid-Mediated Homogeneous Esterification of Cinnamic Anhydride to Xylans.

A new functional biopolymer was synthesized through an ionic liquid-mediated homogeneous grafting of cinnamic anhydride to xylans. The ionic liquid used was 1-allyl-3-methylimidazolium chloride (AMIMCl) ionic liquid. Xylans with degrees of substitution (DS) between 0.11 and 0.57 were accessible in a completely homogeneous system by changing catalysts (NaOH, KOH and LiOH), time, reaction temperature, and cinnamic anhydride/xylan molar ratio. The chemical structure and the thermal stability of the derivatives were characterized by Fourier transform infrared spectroscopy (FT-IR), 13C-NMR spectroscopy, and thermogravimetry. The thermal stability of the derivatives was reduced compared with the original xylan. Possible applications of the cinnamic anhydride-acylated xylan derivatives include wet-end papermaking, organic–inorganic composite films, and hydrogels.