Dielectric properties of graphene/nano-Fe2O3 filled poly (vinyl alcohol)/ Chitosan blends

Novel nanocomposites based on Poly (vinyl alcohol) (PVA), Chitosan (CS), Graphene quantum dots (GQDs) and iron oxide (Fe2O3) nanoparticles (NPs) have been synthesized by solution casting method. The structural mod-ifications and morphological studies were carried out by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscopy/Energy-dispersive X-ray (SEM/EDX) techniques. The results confirm the microscopic interactions and sphere-like morphology of the nanocomposites due to the presence of GQDs and Fe2O3 within the polymer blend. The thermal stability with almost 25% leftover residue for higher nanofillers loading in the nanocomposite was estimated by thermo-gravimetric analysis (TGA). Moreover, the frequency and temperature-dependent dielectric properties were investigated. The dielectric constant and loss tangent values are greatly influenced by reinforcement of GQDs/Fe2O3 and the obtained values were in the range of-104 and-101, respectively at 150 degrees C and 50 Hz. The rise in ac conductivity i.e., 9.8 x 10-4 (S/m) with increasing nanofiller loadings suggests the reduction in capacitive reactance and impedance. However, the semi-circular arcs are observed in the cole-cole plot where the fitted impedance data along with the equivalent circuit is also presented. The reduction of bulk resistance and impedance on increasing the nanofiller loadings with enhanced dielectric properties signifies the use of PVA/CS/GQDs/Fe2O3 nanocomposites as a potential material for energy storage applications.Novel nanocomposites based on Poly (vinyl alcohol) (PVA), Chitosan (CS), Graphene quantum dots (GQDs) and iron oxide (Fe2O3) nanoparticles (NPs) have been synthesized by solution casting method. The structural mod-ifications and morphological studies were carried out by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscopy/Energy-dispersive X-ray (SEM/EDX) techniques. The results confirm the microscopic interactions and sphere-like morphology of the nanocomposites due to the presence of GQDs and Fe2O3 within the polymer blend. The thermal stability with almost 25% leftover residue for higher nanofillers loading in the nanocomposite was estimated by thermo-gravimetric analysis (TGA). Moreover, the frequency and temperature-dependent dielectric properties were investigated. The dielectric constant and loss tangent values are greatly influenced by reinforcement of GQDs/Fe2O3 and the obtained values were in the range of-104 and-101, respectively at 150 degrees C and 50 Hz. The rise in ac conductivity i.e., 9.8 x 10-4 (S/m) with increasing nanofiller loadings suggests the reduction in capacitive reactance and impedance. However, the semi-circular arcs are observed in the cole-cole plot where the fitted impedance data along with the equivalent circuit is also presented. The reduction of bulk resistance and impedance on increasing the nanofiller loadings with enhanced dielectric properties signifies the use of PVA/CS/GQDs/Fe2O3 nanocomposites as a potential material for energy storage applications

Occupational exposure to dromedaries and risk for MERS-CoV infection, Qatar, 2013–2014

We determined the presence of neutralizing antibodies to Middle East respiratory syndrome coronavirus in persons in Qatar with and without dromedary contact. Antibodies were only detected in those with contact, suggesting dromedary exposure as a risk factor for infection. Findings also showed evidence for substantial underestimation of the infection in populations at risk in Qatar

A systematic review on 2D materials for volatile organic compound sensing

Volatile organic compounds (VOCs) are organic chemicals that are toxic and detrimental to the human body and the environment. Therefore, a great mandate for the selective as well as sensitive recognition of VOCs, process control, environmental monitoring, and medical diagnosis is necessary. In the last few years, various forms of nanomaterials have been explored for gas and VOCs sensing with the detection on the miniaturized scale using various sensing approaches including optical, chemiresistive, and electrochemical techniques. Two-dimensional (2D) materials have received tremendous attention owing to their unique structure and extraordinary physical as well as chemical properties which make them an attractive platform for numerous applications including electronics, optoelectronics, energy storage and conversion, catalysis, and chemical sensors. 2D-materials offer unique sensing properties with extremely high sensitivity which is particularly important for the detection of toxic pollutants such as nitrogen dioxide (NO2) and toxic VOCs such as benzene and formaldehyde. This review emphasizes the stateof- the-art recent developments in synthesis, VOCs sensing performance and sensing mechanism of numerous 2D-materials including graphene, graphene oxide (GO), graphene nanoplatelets (Gr-NPls), graphene nanosheets (GNs), transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN), MXenes, black phosphorus (BP) and graphdiyne etc. A brief descriptions of various synthesis approaches of 2D materials are given along with their fundamental VOCs sensing mechanisms. Finally, the performances of various 2D-materials derived VOC sensors are summarize

Dielectric properties of graphene/nano-Fe2O3 filled poly (vinyl alcohol)/ Chitosan blends

Novel nanocomposites based on Poly (vinyl alcohol) (PVA), Chitosan (CS), Graphene quantum dots (GQDs) and iron oxide (Fe2O3) nanoparticles (NPs) have been synthesized by solution casting method. The structural mod-ifications and morphological studies were carried out by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscopy/Energy-dispersive X-ray (SEM/EDX) techniques. The results confirm the microscopic interactions and sphere-like morphology of the nanocomposites due to the presence of GQDs and Fe2O3 within the polymer blend. The thermal stability with almost 25% leftover residue for higher nanofillers loading in the nanocomposite was estimated by thermo-gravimetric analysis (TGA). Moreover, the frequency and temperature-dependent dielectric properties were investigated. The dielectric constant and loss tangent values are greatly influenced by reinforcement of GQDs/Fe2O3 and the obtained values were in the range of-104 and-101, respectively at 150 degrees C and 50 Hz. The rise in ac conductivity i.e., 9.8 x 10-4 (S/m) with increasing nanofiller loadings suggests the reduction in capacitive reactance and impedance. However, the semi-circular arcs are observed in the cole-cole plot where the fitted impedance data along with the equivalent circuit is also presented. The reduction of bulk resistance and impedance on increasing the nanofiller loadings with enhanced dielectric properties signifies the use of PVA/CS/GQDs/Fe2O3 nanocomposites as a potential material for energy storage applications.Novel nanocomposites based on Poly (vinyl alcohol) (PVA), Chitosan (CS), Graphene quantum dots (GQDs) and iron oxide (Fe2O3) nanoparticles (NPs) have been synthesized by solution casting method. The structural mod-ifications and morphological studies were carried out by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscopy/Energy-dispersive X-ray (SEM/EDX) techniques. The results confirm the microscopic interactions and sphere-like morphology of the nanocomposites due to the presence of GQDs and Fe2O3 within the polymer blend. The thermal stability with almost 25% leftover residue for higher nanofillers loading in the nanocomposite was estimated by thermo-gravimetric analysis (TGA). Moreover, the frequency and temperature-dependent dielectric properties were investigated. The dielectric constant and loss tangent values are greatly influenced by reinforcement of GQDs/Fe2O3 and the obtained values were in the range of-104 and-101, respectively at 150 degrees C and 50 Hz. The rise in ac conductivity i.e., 9.8 x 10-4 (S/m) with increasing nanofiller loadings suggests the reduction in capacitive reactance and impedance. However, the semi-circular arcs are observed in the cole-cole plot where the fitted impedance data along with the equivalent circuit is also presented. The reduction of bulk resistance and impedance on increasing the nanofiller loadings with enhanced dielectric properties signifies the use of PVA/CS/GQDs/Fe2O3 nanocomposites as a potential material for energy storage applications

MXene based emerging materials for supercapacitor applications: Recent advances, challenges, and future perspectives

In the past few decades, with the advancement of technology, there has been an increasing demand for high-capacity energy storage devices having durability, low production cost, and flexibility. MXene, a layered 2D transition metal carbide, nitride or carbonitride, exfoliated from its parent MAX phase by selective chemical etching of covalently bonded A layer has become the most emerging material today for energy storage applications. The 2D layered structure, atomic layer thickness, high conductivity, tunable surface functional groups, superior hydrophilicity, good mechanical properties, excellent electrochemical nature, flexibility, and the ease of preparation of MXene has made it the most demanding material today among 2D families. Starting from gas and biosensors, water purification, water splitting, photo and electrocatalysis, transparent conductors in electronics, antibacterial film, electromagnetic interference shielding, and in batteries and supercapacitors, MXene have a wide range of applications. The special properties of MXene have made scientists work on its further theoretical and experimental developments. This article mainly reviews the recent advances of MXene for fabricating durable, pliable, and highly efficient electrochemical energy storage devices using supercapacitors as its power source. The structure of MXene, different synthesis methods, and their unique properties have been deeply studied, as well as the effect of various factors like size and shape of MXene sheets, design of electrode architecture, nature of electrolyte, etc. on the electrochemical performance and charge storage mechanism of MXene based supercapacitors have been emphasized. This article also throws light on state-of-the-art recent progress in MXene composite-based supercapacitors. Finally, its challenges and future advances have been discusse

Enhanced quality factor of polyvinyl formal (PVF) based nanocomposites filled with zinc oxide and carbon black nanoparticles for wireless sensing applications

The present article deals with the preparation of polyvinyl formal based nanocomposites filled with zinc oxide (ZnO) and carbon black nanoparticles using colloidal blending technique. To explore the electrical and structural properties, PVF/ZnO/CBNP nanocomposite films were characterized using Fourier transform infrared (FTIR) spectroscopy, X- Ray diffraction (XRD) and Scanning electron microscopy (SEM). The surface morphology of these nanocomposite films was evaluated using polarized optical microscopy (POM). The structural change in PVF nanocomposite was achieved by incorporating ZnO and CBNP, by homogeneous distribution in polymer nanocomposite. The electrical properties such as impedance and quality factor (Q – factor) of PVF/ZnO/CBNP composite films were elucidated using impedance analyzer in the wide range of frequency from 50 Hz – 20 MHz and temperature in the range 50°C – 150°C. Quality factor was measured as a function of temperature (50 – 150°C) and wide range of frequency from 50 Hz - 20 MHz. The PVF/ZnO/CBNP nanocomposite exhibits high Q-factor (439) for neat PVF films. The incorporation of ZnO at 10% decreases Q-factor to 36.1. Incorporation of CBNP at 5% and ZnO at 5% further reduces the Q-factor to 13.7. With further increase in CBNP content, the Q – factor was found to decrease7.38. Impedance values of PVA/ZnO/CBNP nanocomposites varied at different filler loading in PVF at 3% of CBNP (3.54 X 107Ω) to 10% of CB (1.48 X 107Ω). Increase in the CBNP wt% in PVF shows enhanced conductivity. Thus, based on the above results the PVF/ZnO/CBNP nanocomposites can be used for high – k capacitor applications and also for wireless sensing applications.The authors wish to thank the management of VIT University for providing the facilities for XRD, SEM, and AFM analysis through VIT-DST-FIST scheme. One of the authors M.K. Mohanapriya expresses sincere thanks to the management of Voorhees College, Vellore for their support.Scopu

Synergistic effect of vanadium pentoxide and graphene oxide in polyvinyl alcohol for energy storage application

A novel ultra-high-k composite material comprising of polyvinyl alcohol (PVA) as a polymer matrix and vanadium pentoxide (V2O5) and graphene oxide (GO) as fillers have been developed successfully using colloidal processing technique. The PVA/V2O5 and PVA/V2O5/GO composites were characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV–vis spectroscopy (UV), X-ray diffraction (XRD), thermogravimetric analysis (TGA), polarized optical microscopy (POM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). FTIR studies indicate the strong chemical interaction between GO and polymer matrix. SEM results confirm that GO was homogeneously dispersed within the polymer matrix. The dielectric measurements show that PVA/V2O5/GO composites exhibit ultra-high dielectric constant and low dielectric loss. The dielectric constant increases from (ε = 189.40, 50 Hz, 40 °C) for PVA/V2O5 (95/05 wt/wt) composites to (ε = 5610.76, 50 Hz, 50 °C) for PVA/V2O5/GO composites with 2.5 wt% GO loading and the dielectric loss increases from (tan δ = 3.76, 50 Hz, 80 °C) for PVA/V2O5 (95/05) composites to (tan δ = 9.77, 50 Hz, 150 °C) for PVA/V2O5/GO composites with 2.5 wt% GO loading. This study opens up the avenue to prepare novel graphene-based polymer composites having ultra-high dielectric constant and low dielectric loss and extends the application window of graphene based fillers.One of the authors, Kalim Deshmukh would like to thank the management of B.S. Abdur Rahman University , Chennai 600048, TN, India for providing Junior Research Fellowship (JRF) to carry out this research work. Kalim Deshmukh also wishes to thank Dr. S.M. Khatake from Elantas Beck Pvt. Ltd., Pune for carrying out TGA analysis and Prof. Pundlik R. Bhagat from VIT University, Vellore, TN, India, for help in SEM and AFM studies.Scopu