Dynamic mechanical analysis and broadband electromagnetic interference shielding characteristics of poly (vinyl alcohol)-poly (4-styrenesulfonic acid)-titanium dioxide nanoparticles based tertiary nanocomposites

ABSTRACT

Novel tertiary nanocomposite films comprising of poly (vinyl alcohol) (PVA), poly (4-styrenesulfonic acid) (PSSA) and titanium dioxide (TiO₂) nanoparticles (NP_S) were prepared using simple solvent casting method. The structural, thermal, morphological, thermo-mechanical and electromagnetic interference (EMI) shielding properties of PVA/PSSA/TiO₂ nanocomposite films were investigated. The EMI shielding effectiveness (SE) of PVA/PSSA/TiO₂ nanocomposite films in the X and Ku band was found to be 12 dB and 13 dB respectively at 25 wt% TiO₂ NPs loading. These results demonstrate the possible applications of PVA/PSSA/TiO₂ nanocomposite films as low cost, lightweight and flexible material for EMI shielding.     

Efficient preparation of hybrid nanocomposite coatings based on poly(vinyl alcohol) and silane coupling agent modified TiO2 nanoparticles

In the present investigation, at first, the surface of titanium dioxide (TiO₂) nanoparticles was modified with γ-aminopropyltriethoxy silane as a coupling agent. Then a new kind of poly(vinyl alcohol)/titanium dioxide (PVA/TiO₂) nanocomposites coating with different modified TiO₂ loading were prepared under ultrasonic irradiation process. Finally, these nanocomposites coating were used for fabrication of PVA/TiO₂ films via solution casting method. The resulting nanocomposites were fully characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), thermogravimetric analysis/derivative thermal gravimetric (TGA/DTG), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TEM and SEM results indicated that the surface modified nanoparticles were dispersed homogeneously in PVA matrix on nanoscale and based on obtained results a possible mechanism was proposed for ultrasonic induced nanocomposite fabrication. TGA confirmed that the heat stability of the nanocomposite was improved. UV–vis spectroscopy was employed to evaluate the absorbance and transmittance behavior of the PVA/TiO₂ nanocomposite films in the wavelength range of 200–800 nm. The results showed that this type of films could be used as a coating to shield against UV light.     

Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

A simple and straightforward approach to prepare TiO₂-coated carbon nanotubes (CNTs) is presented. Anatase TiO₂ nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO₂ molar ratio on the adsorption capability and photocatalytic efficiency under UV–visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO₂ NPs-coated CNTs photocatalysts. The TiO₂ NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO₂.     

Polyvinyl alcohol-based fiber membranes with high strength and ultraviolet shielding properties for enhancing the shelf life of grapes

Currently, the rising environmental concerns caused by nonbiodegradable food packaging materials have promoted the research and development of biodegradable alternatives. Polyvinyl alcohol (PVA) was selected as the substrate, and zinc oxide nanoparticles (ZnONPs) and titanium dioxide nanoparticles (TiO₂NPs) were blended and modified with PVA, respectively. Based on the electrostatic spinning technology to prepare fiber membranes with high strength and UV blocking properties for grapes preservation. The study indicated that the tensile strength of PVA fiber membranes increased by 243% and 209% when ZnONPs and TiO₂NPs were added at 1%, respectively. Under UV radiation, the PVA/ZnO composite membranes exhibited superior UV absorption than the PVA/TiO₂ composite membranes. After conducting TG tests, it was found that the addition of ZnONPs decreased the thermal stability of the fiber membranes, while TiO₂NPs could improve the thermal stability. Both composite membranes could extend grapes' shelf life, but the PVA/ZnO composite membranes were more effective at maintaining freshness than the PVA/TiO₂ composite membranes.     

Synthesis and photocatalytic performance of PVA/TiO2/graphene‐MWCNT nanocomposites for dye removal

TiO₂/graphene‐MWCNT nanocomposite was prepared using solvothermal reaction for the effective distribution of TiO₂ nanoparticles on carbonaceous materials. TiO₂/graphene‐MWCNT nanocomposite was immobilized in poly(vinyl alcohol) (PVA) matrix for a convenient recovery after wastewater purification. MWCNT was incorporated in a nanocomposite not only to prevent the restacking of graphene but also to increase the electron transfer from TiO₂. The detailed characterization of the nanocomposite was performed using SEM, EDX, XRD, XPS, and FTIR. The photocatalytic performance of PVA/TiO₂/graphene‐MWCNT nanocomposite was investigated by UV spectroscopy on the basis of degradation of organic pollutants. PVA/TiO₂/graphene‐MWCNT nanocomposite showed improved photocatalytic decomposition of more than 70% of residual dye left in case of using PVA/TiO₂/graphene nanocomposite due to the improved electron transfer and the higher adsorption of organic pollutants. PVA/TiO₂/graphene‐MWCNT nanocomposite was suitable as a promising material for the recyclable photocatalytic wastewater purification system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40715.     

Study of the effect of rutile/anatase TiO2 nanoparticles synthesized by hydrothermal route in electrospun PVA/TiO2 nanocomposites

Mixed rutile–anatase TiO₂ nanoparticles were synthesized by hydrothermal treatment under acidic conditions and incorporated into poly(vinyl alcohol) (PVA). These nanocomposites were electrospun to produce nanofibers of PVA/TiO₂, which were characterized by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The photocatalytic degradation of Rhodamine B and degradation of the polymer by UV‐C lamps were also investigated. The results showed that TiO₂ nanoparticles did not change the morphology and thermal behavior of the nanofiber polymer, but were effective in modifying the UV absorption of PVA without reducing its stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and photocatalytic performance of magnetically separable titania photocatalysts for the degradation of propachlor

A magnetic photocatalyst was prepared by modification of TiO₂ nanoparticles (Degussa P25) with nanocrystalline γ-Fe₂O₃ nanoparticles through a protective lining made up of two oppositely charged polyelectrolytes. As-prepared magnetically separable photocatalysts differing in γ-Fe₂O₃ loading (3, 8, 13, 20 and 30 wt.%) were characterized by XRD, TEM, thermal analysis, Mössbauer and magnetic measurements. The photocatalytic efficiency of the nanocomposite catalysts was evaluated using a chloroacetanilide herbicide (propachlor) in water as model compound. The primary degradation of propachlor followed pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Generally, all magnetic photocatalysts exhibit good catalytic activity towards organic pollutants, do not suffer from photodissolution and can be reused several times without any decrease in their photocatalytic activity.     

Water-dispersible TiO2 nanoparticles via a biphasic solvothermal reaction method

A biphasic solvothermal reaction method has been used for the synthesis of TiO₂ nanoparticles (NPs). In this method, hydrolysis and nucleation occur at the interface of organic phase (titanium (IV) n-propoxide and stearic acid dissolved in toluene) and water phase (tert-butylamine dissolved in water) resulting in the nucleation of the stearic acid-capped TiO₂ NPs. These NPs are hydrophilic due to hydrophobic stearic acid ligands and could be dispersed in toluene, but not in water. These stearic acid-capped TiO₂ NPs were surface-modified with 2,3-dimercaptosuccinic acid (DMSA) in order to make them water soluble. The resultant TiO₂ NPs were easily redispersed in water without any noticeable aggregation. The Rietveld profile fitting of X-ray diffraction (XRD) pattern of the TiO₂ NPs revealed highly crystalline anatase structure. The average crystallite size of TiO₂ NPs was calculated to be 6.89 nm, which agrees with TEM results. These results have important implications for the use of TiO₂ in biomedical, environmental, and industrial applications.     

Reinforcement of structural,thermal and electrical properties and antibacterial activity of PVA/SA blend filled with hybrid nanoparticles (Ag and TiO2 NPs): Nanodielectric for energy storage and food packaging industries‏

In this work, silver nanoparticles (Ag NPs) were prepared using a plant extract which is a cost-effective and environmentally friendly method. The sol-gel method was used to synthesize titanium dioxide nanoparticles (TiO₂ NPs). A solid polymer nanocomposite samples have been prepared via the well-known solution cast way. The present samples were examined using various analytical measurements. The XRD patterns showed a decrease in the degree of crystallinity of the PVA/SA blend due to the addition of the hybrid nanoparticles (Ag and TiO₂ NPs). It was evident by the ATR-FTIR measurement that there is an interaction between the functional groups of the polymeric matrix and the hybrid nanoparticles. XPS confirmed that Ag NPs were loaded onto the surfaces of the PVA/SA/TiO₂ organic-inorganic nanocomposite samples. The TGA curves of the doped samples showed an improvement in their thermal stability compared to the pure sample. From the AC conductivity and electrical modulus, the dynamic ions activity and the kind of relaxation process of the nanocomposites samples were examined. The highest conductivity was log −6.066 S/cm for the polymeric sample doped with 1.60% Ag@TiO₂ NPs, as showed by the AC conductivity measurement. A wide dispersion is observed in the dielectric constant spectra at low frequency. It was also evident from the data that the antibacterial activity of the pristine PVA/SA matrix was growing due to the inclusion of the hybrid nanoparticles to the polymeric matrix. Therefore, the obtained results indicate the applicability of these samples and their potential for use in the semiconductor industry, portable electrochemical batteries and energy storage industry, due to the remarkable improvement in the structural, thermal and electrical properties. Also, the good antibacterial activity of these films provides new samples as effective biomaterials and has the potential to be used in the food packaging industry.     

UV-curable polyurethane acrylate–Ag/TiO2 nanocomposites with superior UV light antibacterial activity

Polyurethane acrylate (PUA)–Ag/TiO₂ nanocomposites were synthesized through in situ polymerization. The well-dispersed Ag/TiO₂ nanorods serve as photoinitiator. Meanwhile, the PUA–Ag/TiO₂ nanocomposite films exhibit superior activity toward the photocatalytic degradation of Escherichia coli under UV light. The excellent UV curing and antibacterial activities can be ascribed to the synergistic effect of Ag and TiO₂, which promotes the effective electron/hole separation and thus generates various reactive species. Thin films with these nanoparticles are more hydrophilic after UV illumination. And the antibacterial mechanism of the UV-curable PUA–Ag/TiO₂ nanocomposites was proposed.     

TiO2-coated nanostructures for dye photo-degradation in water

The photocatalytic efficiency of a thin-film TiO₂-coated nanostructured template is studied by dye degradation in water. The nanostructured template was synthesized by metal-assisted wet etching of Si and used as substrate for the deposition of a thin film of TiO₂ (10 nm thick) by atomic layer deposition. A complete structural characterization was made by scanning and transmission electron microscopies. The significant photocatalytic performance was evaluated by the degradation of two dyes in water: methylene blue and methyl orange. The relevance of the reported results is discussed, opening the route toward the application of the synthesized nanostructured TiO₂ for water purification.     

Construction of Z-scheme type CdS–Au–TiO2 hollow nanorod arrays with enhanced photocatalytic activity

The Z-scheme type CdS–Au–TiO₂ hollow nanorod arrays have been constructed on glass substrates by following these simple steps: firstly, highly ordered TiO₂ hollow nanorod arrays (THNAs) were synthesized by liquid phase deposition (LPD) using ZnO nanorod arrays as templates; then both Au core and CdS shell nanoparticles were achieved on the THNAs by in situ photodeposition. The prepared three-component films were characterized by field-emission scanning electron microscopy (FSEM), high-resolution transmission electron microscope (HRTEM), Raman scattering and ultraviolet–visible absorption spectrum. The results showed that Au–CdS core–shell nanoparticles were well dispersed on wall of anatase THNAs from top to bottom. The three-component nanojunction system was evaluated for their photocatalytic activity through the degradation of methylene blue (MB) in aqueous solution. It was found that the CdS–Au–TiO₂ three-component hollow nanorod arrays exhibited significantly enhanced photocatalytic activity compared with single (THNAs) and two components (Au-THNAs or CdS-THNAs) systems. Reasons for this enhanced photocatalytic activity were revealed by photoluminescence (PL) results of our samples.     

Employment of ultrasonic waves for the preparation of PVA/TiO2‐BSA nanocomposites: Mechanical,thermal, and optical properties

The goal of this project is to obtain poly(vinyl alcohol) (PVA)/TiO₂‐bovine serum albumin (BSA) nanocomposite (NC) films in different weight percentages of modified TiO₂. For this purpose, to prevent the accumulation of nanoparticles (NPs) in the PVA matrix, the surface of the TiO₂ NPs was treated with the BSA molecules. To achieve this aim, ultrasonic waves were used as an environmentally friendly and green process that decrease the time of reactions, help better spreading of TiO₂ NPs and maintain dimensions of TiO₂ NPs in the nanoscale range. In the end, the features of the PVA/TiO₂‐BSA NC films were considered with a variety of techniques. The Fourier transform infrared spectroscopy, energy dispersive X‐ray, and X‐ray diffraction showed that the BSA was well placed on the surface of TiO₂ NPs. The thermal gravimetric analysis and UV‐visible results demonstrated that all the PVA/TiO₂‐BSA NC films have better thermal and optical properties than the pure PVA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46558.     

Enhanced Solid‐Phase Photocatalytic Degradation Activity of a Poly(vinyl chloride)‐TiO2 Nanocomposite Film with Bismuth Oxyiodide

A new type of photodegradable poly(vinyl chloride)‐bismuth oxyiodide/TiO₂ (PVC‐BiOI/TiO₂) nanocomposite film was prepared by embedding a nano‐TiO₂ photocatalyst modified by BiOI into the commercial PVC plastic. The solid‐phase photocatalytic degradation behavior of the as‐prepared film was investigated in ambient air at room temperature under UV light irradiation, with the aid of UV‐Vis spectroscopy, weight loss monitoring, scanning electron microscopy, and FT‐IR spectroscopy. Compared to the PVC‐TiO₂ nanocomposite film, the PVC‐BiOI nanocomposite film and the pure PVC film, the PVC‐BiOI/TiO₂ nanocomposite film exhibited a higher photocatalytic degradation activity. The optimal mass ratio of BiOI to TiO₂ was found to be 0.75 %. The weight loss rate of the PVC‐BiOI/TiO₂ nanocomposite film reached 30.8 % after 336 h of irradiation, which is 1.5 times higher than that of the PVC‐TiO₂ nanocomposite film under identical conditions. The solid‐phase photocatalytic degradation mechanism of the nanocomposite films was briefly discussed.     

Tungsten and nitrogen co-doped TiO2 nano-powders with strong visible light response

A two-step method, combining with sol–gel and mechanical alloying (MA) method, was used to fabricate the tungsten and nitrogen co-doped TiO₂ nano-powders ((W, N) co-doped TiO₂ NPs). The (W, N) co-doped TiO₂ NPs showed strong absorbance in visible range, as long as 650 nm. Enhanced photocatalytic activities under visible light irradiation were also observed from the results of photodegradation experiments and chemical oxygen demand (COD) analysis. Physical, chemical, and optical properties of the samples were investigated. Possible reasons for the enhanced photocatalytic activities were analyzed based on the experimental results. Oxygen vacancies detected by electron spin response (ESR) spectra, acting as trapping agencies for electrons (e⁻) to produce active oxygen species (O²⁻), were proved to be the main cause for the improved photocatalytic performances.     

Enhancing Photophysical Properties of MDMO-PPV-DMP Conjugated Polymer via Incorporation Anatase Titania Nanoparticles

Improving photophysical properties of poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene]-end capped with dimethylphenyl, MDMO-PPV-DMP, was achieved via incorporation anatase titania nanoparticles (TiO₂ NPs). Various contents of TiO₂ NPs (up to 50 wt%) were dispersed into fixed concentration of the MDMO-PPV-DMP (5 mg/mL) via solution blending method followed by spin coating onto cleaned glass substrates to form their thin films. The formation of MDMO-PPV-DMP/TiO₂ nanocomposites was evidenced from the results of X-ray diffractograms and Fourier transform infrared spectra, while the homogeneity of the films was detected by field emission-scanning electron microscopy (FE-SEM). Increasing the contents of TiO₂ NPs resulted in a slight decrease (up to ~?0.07 eV) in both direct and indirect energy band gaps of the MDMO-PPV-DMP in the nanocomposite thin films. A higher degree of disorder in the electronic structure of the MDMO-PPV-DMP/TiO₂ nanocomposite and increasing the localized states density within the forbidden gap can be achieved by increasing the energy tail values and decreasing the steepness parameter with rising the TiO₂ NPs content. The enhancement in emission intensity and broadening of emission spectra with increasing the TiO₂ NPs content can be explained by the charge trapping effect and particle size distribution, respectively. Moreover, the incorporation of TiO₂ NPs into the MDMO-PPV-DMP led to tuning its emitted light color which is of distinct interest in optoelectronic devices.

     

Fullerene modification CdSe/TiO2 and modification of photocatalytic activity under visible light

CdSe, CdSe-TiO₂, and CdSe-C₆₀/TiO₂ composites were prepared using sol–gel method, and their photocatalytic activity was evaluated by measuring the degradation of rhodamine B solutions under visible light. The surface area, surface structure, crystal phase, and elemental identification of these composites were characterized by nitrogen adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and UV-visible (vis) absorption spectrophotometry. XRD showed that the CdSe-C₆₀/TiO₂ composite contained a typical single and clear anatase phase. SEM of the CdSe-C₆₀/TiO₂ composites revealed a homogenous composition in the particles. EDX revealed the presence of C and Ti with strong Cd and Se peaks in the CdSe-C₆₀/TiO₂ composite. The degradation of dye was determined by UV–vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase in the photoabsorption effect by fullerene and the cooperative effect of the CdSe. The repeatability of photocatalytic activity was also tested in order to investigate the stability of C₆₀ and CdS-C₆₀/TiO₂ composites.     

Visible photocatalytic activity and photoelectrochemical behavior of TiO2 nanoparticles modified with metal porphyrins containing hydroxyl group

TiO₂ nanoparticles modified with 5-(p-hydroxylphenyl)-10,15,20-triphenylporphyrin (HTPP), 5-(p-hydroxylphenyl)-10,15,20-triphenylporphyrin zinc (ZnHTPP) and trans-dichloro-5-(p-hydroxylphenyl)-10,15,20-triphenylporphyrin tin (SnHTPP) were prepared in order to improve the visible photocatalytic activity of TiO₂ nanoparticles. The photocatalytic activity of the modified TiO₂ nanoparticles was investigated by carrying out the photodegradation of methyl orange in aqueous solution under visible light irradiation. The TiO₂ nanoparticles modified with SnHTPP show the highest visible photocatalytic activity with a degradation ratio of 86% of methyl orange after 180 min irradiation among three catalysts. This result indicates that the central metal ions in porphyrins can significantly influence the sensitization efficiency of porphyrins. In addition, the photoelectrochemical behavior of the modified TiO₂ nanoparticles was examined and related to their photocatalytic activity. Finally, the photocatalytic mechanism was discussed preliminarily.     

Enhancement of the photocatalytic performance of Ni-loaded TiO2 photocatalyst under sunlight

A highly sunlight active Ni-loaded TiO₂ nanocomposite (Ni/TiO₂) is successfully prepared by a simple chemical reduction method using tetrabutyl titanate as a precursor, Ni(NO₃)₂·6H₂O as a nickel source, and N₂H₄·H₂O as a reductant, respectively. The crystal structure, morphology and UV–vis diffuse reflectance characteristics are investigated by XRD, TEM, and UV–vis diffuse reflectance spectroscopy, while the photocatalytic performance of Ni/TiO₂ is evaluated by photocatalytic degradation of methyl orange solution under UV and sunlight irradiation. Results show that the crystal structure of TiO₂ is not changed upon the loading of Ni, the photocatalytic performance of TiO₂ under both UV-light and sunlight, however, is enhanced greatly. The enhancement of the photocatalytic performance of Ni/TiO₂ is attributed to the increase of the photogenerated electron–hole separation efficiency and the advanced absorption of light due to surface plasmon effect of Ni nanoparticles.     

Ag nanoparticles loaded TiO2/MWCNT ternary nanocomposite: A visible-light-driven photocatalyst with enhanced photocatalytic performance and stability

A visible light active photocatalyst, Ag/TiO₂/MWCNT was synthesized by loading of Ag nanoparticles onto TiO₂/MWCNT nanocomposite. The photocatalytic activity of Ag/TiO₂/MWCNT ternary nanocomposite was evaluated for the degradation of methylene blue dye under UV and visible light irradiation. Ag/TiO₂/MWCNT ternary nanocomposite exhibits (~9 times) higher photocatalytic activity than TiO₂/MWCNT and (~2 times) higher than Ag/TiO₂ binary nanocomposites under visible light irradiation. The enhancement in the photocatalytic activity is attributed to the synergistic effect between Ag nanoparticles and MWCNT, which enhance the charge separation efficiency by Schottky barrier formation at Ag/TiO₂ interface and role of MWCNT as an electron reservoir. Effect of different scavengers on the degradation of methylene blue dye in the presence of catalyst has been investigated to find the role of photogenerated electrons and holes. Simultaneously, the Ag/TiO₂/MWCNT shows excellent photocatalytic stability. This work highlights the importance of Ag/TiO₂/MWCNT ternary nanocomposite as highly efficient and stable visible-light-driven photocatalyst for the degradation of organic dyes.