PVA Nanocomposite Research Articles

Composition and pH dependence on aggregation of SiO2–PVA suspension for the synthesis of porous SiO2–PVA nanocomposite

Porous monolithic SiO2–poly(vinyl alcohol) (PVA) nanocomposites were fabricated by drying an SiO2–PVA suspension. Depending on the amount of added PVA and pH value of the suspension, the Brunauer–Emmett–Teller surface areas, total pore volumes, and mean pore radii of the (100 − x)SiO2–xPVA (x = 0, 10, 20, 30 wt%) nanocomposites were 102–313 m2 g−1, 0.61–1.42 cm3 g−1, and 8.1–14.7 nm, respectively. Some cracks were observed in the monolithic SiO2–PVA nanocomposite, affected by the pore size. To elucidate crack generation, the correlation between the dispersion/aggregation in the SiO2–PVA suspension and the pore size distribution of the nanocomposite was evaluated in terms of the added PVA amount and pH value. At x = 20 and pH 3, the SiO2 particles and PVA aggregated in the suspension. The preparation of crack-free monolithic SiO2–PVA nanocomposites was possible using the aggregated suspension owing to the low capillary force during drying because of the relatively large pores.

Preparation and photoluminescence of monolithic silica glass doped with Tb3+ ions using SiO2–PVA nanocomposite

The monolithic silica glass doped with Tb3+ ions was fabricated using the SiO2–PVA nanocomposite as the glass precursor. In order to dope Tb3+ ions in the monolithic silica glass, the mesoporous SiO2–PVA nanocomposite was immersed in the Tb3+ ions contained solution and subsequently sintered at 1100°C in air. Consequently the monolithic transparent silica glass was obtained, exhibiting green fluorescence attributed to 5D4→7F5 main transitions under UV excitation. The Tb concentration in the sintered glass could be controlled by immersion time of the nanocomposite in the solution.

Plasmonic optical sensors printed from Ag–PVA nanoinks

In this paper we report on the use of a nanocomposite based on silver nanoparticles embedded in PVA as a plasmonic optical sensor to detect and quantify trace amounts of amines in gas and water, respectively. The transduction mechanism of the sensor is based on the changes of the LSPR band of Ag NPs when analyte molecules are chemisorbed on their surface. The Ag–PVA sensors are fabricated by means of a high-precision microplotter, a direct-write technology developed for printing materials from solution. The nanoink is formulated with a metal precursor (AgNO3) and a polymer (PVA) using an adequate mixture of solvents to meet the rheological requirements for the fluid dispensing process. The LSPR intensity is the most sensitive magnitude to follow the interaction between Ag NPs embedded in PVA and amines. Ag–PVA patterns are tested as a plasmonic optical sensor for the detection of ethylenediamine in solution showing a limit of detection as low as 0.1 nM. Moreover Ag nanocomposite patterns are also used for sensing vapours of several biogenic (cadaverine and putrescine) and synthetic (ethylenediamine and methylenediamine) amines, where shorter amines exhibit the largest sensor response. This plasmonic optical sensor is also tested in real-time monitoring of chicken meat spoilage at room temperature. We believe that the Ag–PVA nanocomposite can be the basis for the development of sensor spots, bar-codes and other labels for smart packaging technology, among other sensing applications.

폴리(비닐 알코올)/사포나이트 나노 복합체 필름 및 연신된 필름의 열적 성질, 모폴로지, 광학 투명성, 및 기체 투과성

용액 삽입법을 이용하여 다양한 함량의 사포나이트(SPT) 점토를 포함한 폴리(비닐 알코올)(poly(vinyl alcohol), PVA) 나노 복합체 필름을 제조하였다. SPT를 0에서 10 wt%까지 첨가한 PVA 나노 복합체 필름들의 열적 특성, 모폴로지, 광학 투명성 및 기체 투과성에 대해 조사하였다. 특히 5 wt% SPT 포함한 PVA 복합체 필름이 매우 우수한 열적 특성과 기체 차단성을 나타내었다. 5 wt% SPT 포함된 복합체 필름을 연신율에 따라 150에서 250%까지 이축 연신하였고, 이축 연신율에 따른 점토 분산성, 광학적 특성 및 기체 투과성에 대한 조사를 하였다. 다양한 비로 이축 연신한 PVA 나노 복합체 필름은 우수한 광학 투명성과 산소 차단성을 보였다. Poly(vinyl alcohol)(PVA) nanocomposite films containing various saponite (SPT) clay contents were synthesized using a solution intercalation method. The thermal property, morphology, optical transparency, and gas permeability of the PVA nanocomposite films with various SPT contents in the range of 0 to 10 wt% were examined. PVA nanocomposite film containing 5 wt% SPT showed excellent thermal and gas barrier property. The hybrid films containing 5 wt% SPT were equibiaxially stretched with stretching ratios ranging from 150 to 250%. The clay dispersion, optical transparency, and gas permeability were also examined as a function of equibiaxial stretching ratio. The PVA nanocomposite films with various equibiaxial stretching ratios showed excellent optical transparency and barrier to oxygen permeability.

Synthesis, Characterization and Anti-bacterial Activity of Ag-NPs

SYNTHESIS, characterization and comparison the anti bacterial activity of both silver/ polyvinyl alcohol (Ag/ PVA) nanocomposite and nisin, for some pathogenic bacteria was carried out. Applications of the nicin include dental care products, pharmaceutical products such as stomach ulcers and colon infection treatment and potential birth control. Ag/ PVA nanocomposite was prepared by in situ reduction method in which silver nitrate, gamma irradiation and PVA act as precursor, reductant and stabilizer respectively. The synthesized nanocomposites have potential antibacterial activity toward both Gram-positive and Gram-negative bacteria. Further studies have demonstrated the structure and the distribution of Ag nanoparticles caped within PVA polymer chain such as X-ray diffraction (XRD), transmission electron microscopy (TEM) were carried out.

Polyaniline nanofiber reinforced nanocomposite coated quartz crystal microbalance based highly sensitive free radical sensors

Abstract AT-cut quartz crystals with gold electrodes have been coated with PAni nanofiber reinforced PVA nanocomposite thin films for determination of free radicals in solution. The frequency shifts of PAni nanofiber reinforced PVA nanocomposite modified quartz crystal electrode upon exposure to different concentrations of free radicals have been monitored and found to vary linearly with free radical concentration. A sensitivity factor of 133.42, 140.13 and 129.13 Hz ppb −1 for the DPPH, hydroxyl and peroxyl free radicals, respectively within the concentration range of 500–10000 ppb has been observed for direct exposure. The response time has been found to be in the range of 0.5–2.36 s and decreases with the increasing concentration of the analyte. The sensing mechanism of the free radical sensor has been investigated by XRD, FTIR, impedance and ac conductivity spectra of the PAni nanofiber reinforced PVA nanocomposite films before and after exposure to different concentration of the analytes. The results indicate that upon exposure to the analyte, PAni nanofiber reinforced PVA nanocomposites get oxidized by losing hydrogen leading to decrease in mass with a corresponding increase in frequency of the quartz crystal electrode that makes the sensor highly sensitive to free radicals in solution up to ppb level.

Cu nanoparticles induced structural, optical and electrical modification in PVA

Cu nanoparticles were synthesized in PVA matrix by chemical reduction of cupric nitrate with hydrazine hydrate. Structural characterization of synthesized Cu–PVA nanocomposite was carried out using UV–Visible Spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Appearance of characteristic surface plasmon resonance peak of Cu nanoparticles at 591 nm in absorption spectra of Cu–PVA colloidal solution confirms the formation of Cu nanoparticles. TEM investigation indicates that Cu nanoparticles of size 16 nm are formed in PVA matrix which are in agreement with the size obtained using X-ray diffraction. Morphology of Cu–PVA nanocomposite was further confirmed using SEM. Analysis of UV–Visible absorption and reflection data indicates towards the reduction in optical band gap and increase in refractive index of the resulting nanocomposite. The synthesized Cu–PVA nanocomposite has been found to be more conducting than PVA as ascertained using I–V studies. The decrease in band gap and increase in conductivity can be correlated due to the formation of localized electronic states in PVA matrix due to insertion of Cu nanoparticles. Photoluminescence measurements showed strong blue visible emission peak at 450 nm at different excitation wavelengths in the range of 220–245 nm.

Facile preparation of water-dispersible graphene sheets stabilized by acid-treated multi-walled carbon nanotubes and their poly(vinyl alcohol) composites

Graphene has attracted tremendous interest in reinforcing fillers due to its unique structure and excellent physical properties. However, efficient reinforcement has been largely limited because graphene tends to agglomerate within a polymer matrix. In this study, direct reduction of graphene oxide (GO) in water in the presence of acid-treated multi-walled carbon nanotubes (t-CNTs) results in a homogeneous dispersion of reduced graphene oxide (r-GO) and t-CNT hybrids. The three-dimensional r-GO/t-CNTs hybrids (abbreviated as G-CNT hybrids) possess unique properties, making them ideal reinforcing fillers for polymer nanocomposites. Poly(vinyl alcohol) (PVA) composite containing G-CNT hybrids is then prepared by a simple water casting method. Due to the synergistic interaction of the two kinds of nanofillers, the tensile strength and Young's modulus of the resulting PVA nanocomposite filled with only 0.6 wt% G-CNT hybrids are significantly improved by about 77% and 65%, respectively. The results indicate that the nanohybrids are well dispersed throughout the PVA matrix and form strong interfacial interactions with the matrix. Besides, the presence of G-CNT hybrids slightly increases the thermal stability at 5% weight loss and remarkably improves the amount of residues of PVA nanocomposites. For comparison, we also prepare a PVA composite with the addition of only t-CNTs and find that its mechanical properties show limited enhancement owing to the decreased length-to-diameter ratio and structural defects of CNTs by acid treatment. Our work therefore provides a new way for the preparation of hybrid carbon nanomaterials with unique structure and excellent properties for fabricating high-performance polymer nanocomposites.

Fabrication of Au nanoparticles doped bulk silica glass by use of SiO<sub>2</sub>–PVA nanocomposite

Fabrication of Au nanoparticles doped bulk silica glass by use of SiO<sub>2</sub>–PVA nanocomposite

Preparation and crystallization behavior of multiwalled carbon nanotubes/poly(vinyl alcohol) nanocomposites

AbstractThe poly(vinyl alcohol) (PVA)‐based nanocomposites embedded with modified multiwalled carbon nanotubes (MWCNTs) were prepared. To enhance the interfacial interaction between MWCNTs and PVA, acid‐treated MWCNTs were grafted with PVA chains, compatibilizing MWCNTs and the matrix. The better dispersion of MWCNTs in PVA matrix was obtained by the introduction of MDI reaction bridges and then PVA molecules onto the surface of MWCNTs. Moreover, strong interaction between MWCNTs and PVA matrix was evidenced through the measurement results of the melting behavior, polarized Raman measurement, and nonisothermal crystallization behavior of the nanocomposites. Owing to the reinforcement of MWCNTs, the tensile strength and modulus of PVA nanocomposite containing 0.9 wt% MWCNTs were increased by 160.7 and 109.2%, respectively, compared to neat PVA. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Preparation of SiO2-PVA nanocomposite and monolithic transparent silica glass by sintering

We present a procedure for fabricating transparent silica glass that involves the sintering of green bodies prepared from an inorganic–organic nanocomposite. The nanocomposite was prepared from fumed silica and poly(vinyl alcohol) (PVA). We investigated the SiO2–PVA nanocomposite by Fourier transform infrared spectrometry (FT-IR) measurement, transmission electron microscopy and electron energy-loss spectroscopy, and the results revealed homogeneously dispersed SiO2 nanoparticles and PVA. We examined the relationship between the pH and ζ potential of the SiO2 suspension and the formability of the SiO2–PVA nanocomposite. Formability of the SiO2–PVA nanocomposite was dependent on the pH of the SiO2 suspension, and a monolithic SiO2–PVA nanocomposite without cracks was obtained using a SiO2 suspension at around the isoelectric point (pI). By sintering the SiO2–PVA nanocomposite in air at 1100°C, monolithic transparent silica glass was obtained with no cracks. The glass is highly transparent from the ultraviolet to the visible region.

Poly(vinyl alcohol)-assisted dispersion of multiwalled carbon nanotubes in aqueous solution for electroanalysis

Multiwalled carbon nanotubes (MWNTs) were directly dispersed into poly(vinyl alcohol) (PVA) aqueous solution without functionalization of their surface. A MWNTs–PVA nanocomposite film is prepared by cast deposition from a homogeneous MWNTs–PVA solution. The morphology of the resulting MWNTs–PVA nanocomposite film is characterized by atomic force microscopy (AFM). Well-defined voltammetric responses are observed for the Fe ( CN ) 6 4 - / Fe ( CN ) 6 3 - redox system in aqueous 0.1 M KCl at MWNTs–PVA nanocomposite film modified glassy carbon electrode. In contrast to electrode coated only with PVA, both anodic and cathodic peak currents depended linearly on the square root of the scan rate over the range of 25–200 mV/s at MWNTs–PVA nanocomposite film modified electrode, which suggests diffusion-control and fast electron conduction within the film.

Preparation and dielectric property of Ag–PVA nano-composite

The property of nano-powder was reviewed with emphasis on its Coulomb blockade effects. Ag-colloid of different concentration with different particle size was prepared. Ag–PVA composite colloid was obtained by mixing Ag-colloid with PVA solution. TEM showed that Ag particles (<100 nm) were uniformly dispersed in PVA. The resistivity at room and low temperatures and breakdown field strength of samples were investigated. The results show that dielectric properties of composite change while Ag content or distributing state changes. The composite with 20–30 nm Ag particles has a higher resistivity and breakdown field than its matrix. In a word, Coulomb blockade effects of metal powders could improve resistivity and breakdown field of its matrix.