Polyvinyl alcohol: A review of research status and use of polyvinyl alcohol based nanocomposites

During the past decade there has been intense activity in the field of laser-induced breakdown spectroscopy (LIBS). This activity includes studies of laser ablation and properties of the laser spark, the development of methods to enhance LIBS detection capabilities, and the application of LIBS to specific analysis needs. The unique capabilities of LIBS make it particularly suited for applications that cannot be addressed by conventional analytical methods. Potential applications of the method are numerous and several applications have been realized, resulting in on-line operating instruments. Other applications will require that the method be developed further to improve analytical performance. Here we present an overview of the LIBS method, discussing its many advantages and some important limitations as an analytical method and how these relate to potential applications.

Laser-Induced Breakdown Spectroscopy—Capabilities and Limitations

The basic ideas of the B-spline R-matrix (BSR) approach are reviewed, and the use of the method is illustrated with a variety of applications to atomic structure, electron?atom collisions and photo-induced processes. Special emphasis is placed on complex, open-shell targets, for which the method has proven very successful in reproducing, for example, a wealth of near-threshold resonance structures. Recent extensions to a fully relativistic framework and intermediate energies have allowed for an accurate treatment of heavy targets as well as a fully nonperturbative scheme for electron-impact ionization. Finally, field-free BSR Hamiltonian and electric dipole matrices can be employed in the time-dependent treatment of intense short-pulse laser?atom interactions.

https://iopscience.iop.org/article/10.1088/0953-4075/46/11/112001/pdf

The B-spline R-matrix method for atomic processes: application to atomic structure, electron collisions and photoionization

Laser-induced plasma temperature

As a novel biodegradable material, poly (vinyl) alcohol (PVA)/starch (ST)/ glycerol (GL)/ halloysite nanotube (HNT) nanocomposite films were prepared by solution casting at the HNT contents of 0.25, 0.5, 1, 3 and 5 wt%. Water absorption capacity and water solubility of nanocomposite films were decreased remarkably by 44.24 and 48.05%, respectively, with increasing the HNT content from 0 to 5 wt% when compared with those of biopolymer matrices. Moreover, the water contact angle of nanocomposite films increased by 21.36o with the incorporation of HNTs. The presence of HNTs appeared to reduce the overall migration rates for PVA/ST/GL/HNT nanocomposite films when interacting with either hydrophilic or lipophilic food simulants. However, the migration rates of HNTs alone were enhanced with increasing the HNT contents in hydrophilic, lipophilic and acidic food simulants. On the other hand, the biodegradation rate and light transmittance of nanocomposite films were reduced linearly by 18.56 and 26.90% with increasing the HNT content from 0 to 5 wt%. Overall, novel PVA/ST/GL/HNT nanocomposite films in this study offer highly competitive material with excellent water resistance, good biodegradability and acceptable transparency to be potentially used for sustainable food packaging particularly targeting lipophilic and acidic foodstuffs.

/pdf/biodegradable-and-water-resistant-poly-vinyl-alcohol-pva-3u4ahau0d9.pdf

Biodegradable and water resistant poly(vinyl) alcohol (PVA)/starch (ST)/glycerol (GL)/halloysite nanotube (HNT) nanocomposite films for sustainable food packaging

We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron number densities have been extracted from the Stark broadened line profiles. The spatial variations in the spectral line intensities and the plasma parameters at 1000, 500, and 100 mbar air pressures have been evaluated. Besides, the effect of the ambient gases (He, Ne, and Ar), the laser irradiance, and the laser wavelengths on the plasma parameters have been investigated.

Spectroscopic characterization of laser ablation brass plasma

Herein, we report successful incorporation of graphene oxide (GO) nanosheets into poly(vinyl alcohol) (PVA) matrix by employing solution casting method. The effect of GO loadings on structural, optical and mechanical properties of PVA films was investigated. Most of the optical properties of such films are reported for the first time in the present study. On incorporating GO nanosheets into PVA matrix, the properties of nanocomposites were changed entirely. The tensile strength and Young’s modulus of nanocomposites were enhanced. Alongside, a variation in absorption edge, direct/indirect band gap, Urbach energy, refractive index, optical dielectric constant, optical conductivity and dispersion parameters were noticed. The band gap and dispersion parameters were calculated using Tauc’s and Wemple–DiDomenico models, respectively. Helpin–Tsai and mixture rule models were employed to calculate Young’s modulus. The applied models reinforced the experimental results in the present study. Advanced analytical techniques were employed to characterize the nanocomposites films. The prepared nanocomposites might be used in designing the opto-electronic devices.

Graphene oxides nanosheets mediation of poly(vinyl alcohol) films in tuning their structural and opto-mechanical attributes

Graphene, being a unique carbon allotrope with a structure that is one atom thick, is known as a mysterious material in the current era due to its strange nature. It has attained global attention due to its amazing mechanical, electrical, thermal and optical properties. Recent progress has revealed that materials built with graphene can have a limitless impact on nanocomposites, electronic, optoelectronic and energy storage devices as well as chemical sensors. In the present study, graphite flakes were chemically oxidized in graphite oxide via the modified Hummers' method, i.e. without adding sodium nitrate. The graphite oxide was exfoliated in distilled water by using an ultrasonic bath to fabricate graphene oxide nanosheets. The graphene was acquired through an inexpensive and large-scale production route to eliminate functional groups containing oxygen by using hydrazine monohydrate as a reducing agent. The reduced graphene oxide obtained through this route contained residual oxygen-functional groups which can act as active sites for gas molecular interaction and be used in a variety of applications like gas sensing. The prepared samples were analyzed using the dynamic light scattering technique, UV–visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy and atomic force microscopy.

https://iopscience.iop.org/article/10.1088/2053-1591/3/10/105036/pdf

Synthesis and structural characterization of separate graphene oxide and reduced graphene oxide nanosheets

Purpose of present study was to investigate the effect of different nanofillers doping on structural and thermal properties of poly(vinyl alcohol) (PVA)-based nanocomposite films. Herein, ZnO nanoparticles (NPs), CuO NPs, graphene oxide and reduced graphene oxide (RGO) nanosheets have been used as separate nanofillers in the formation of PVA nanocomposite films via solution casting approach. The prepared composite films were characterized using X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential scanning calorimetry and tensile strength testing. The results demonstrate the effect of various nanofillers on glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), percentage crystallinity (%χc) and tensile strength of composite films. A doping with (0.02 wt%) RGO nanosheets caused significant influence on thermal properties and tensile strength of PVA composite films as compared to other test nanofillers. The doping with RGO nanosheets resulted in elevation of Tg (48.2 °C), Tm (218.3 °C), Tc (157.8 °C) and %χc (41.9%) as compared to that of pure PVA (Tg 38.4 °C, Tm 190.4 °C, Tc 115.1 °C and %χc 22.2%). Overall, the doping of PVA with graphene-based nanosheets exhibited better tensile strength and thermal stability of nanocomposite as compared with other tested nanofillers.

M. A. Kalyar

Papers

Polyvinyl alcohol: A review of research status and use of polyvinyl alcohol based nanocomposites

Spectroscopic characterization of laser ablation brass plasma

Graphene oxides nanosheets mediation of poly(vinyl alcohol) films in tuning their structural and opto-mechanical attributes

Synthesis and structural characterization of separate graphene oxide and reduced graphene oxide nanosheets

Investigation of structural and thermal properties of distinct nanofillers-doped PVA composite films