Antibacterial activity and dielectric properties of the PVA/cellulose nanocrystal composite using the synergistic effect of rGO@CuNPs.

This work aims to enhance the performance of the polyvinyl alcohol (PVA) composite by using cellulose nanocrystal (CNC) as reinforcement and copper nanoparticles (CuNPs)/reduced graphene oxide (rGO) as conducting and antimicrobial reagents. Firstly, rGO was loaded onto CuNPs using an eco-friendly microwave method. Different techniques characterized the components and prepared composites, which indicated the incorporation of cellulose nanocrystals and rGO@CuNPs within the polyvinyl alcohol matrix. Utilizing the clear zone of inhibition, the antibacterial test was quantified. Compared to the neat composite, the rGO@CuNPs loaded polyvinyl alcohol/ cellulose nanocrystal composites exhibited no bacterial growth against S. aureus, E. coli, and C. albicans. However, all composites did not have antifungal activity against A. niger. The combination of conductivity and interfacial polarization is the reason for the abrupt increase of permittivity with decreasing frequency. Besides, adding rGO@CuNPs improved the electrical conductivity. DC-Conductivity increased about a decade after adding cellulose nanocrystal to polyvinyl alcohol, then another decade after adding CuONPs. The electric loss modulus representation shows a systematic shift in the peak position towards higher frequencies, decreasing the so-called conductivity relaxation time. This is the main reason for the enhancement of conductivity. The systematic attenuation of peaks' height with increasing conductivity is still unclear.

Charge transport and heavy metal removal efficacy of graphitic carbon nitride doped with CeO2.

Doping of graphitic carbon nitride (g-C3N4) with semiconductors prevents electron-hole recombination and enhances adsorption capacity. This work investigates the synthesis of a water remediation material using g-C3N4 doped with CeO2 using two different techniques. The chemical structures of the doped g-C3N4 samples were confirmed using FTIR, XRD, XPS and their morphology was studied using SEM-EDX. Charge transport through the doped materials was illustrated by a comprehensive dielectric study using broadband spectroscopy. The ability of doped g-C3N4 to adsorb heavy metals was investigated thoroughly in the light of applying different parameters such as temperature, pH, time, and concentration. The results showed that the mode of doping of g-C3N4 by CeO2 strongly affected its adsorption capacity. However, g-C3N4 doped with CeO2 using the first mode adsorbed 998.4 mg g-1 in case of Pb2+ and 448 for Cd2+. Kinetic study revealed that the adsorption process obeyed PSORE as its q exp e is close to its q cal e and the rate-controlling step involved coordination among the synthetic materials and the heavy metal ions. The recovery of Pb2+ and Cd2+ ions from various sorbents was investigated by utilizing different molar concentrations of HNO3 and indicated no significant change in the sorption capability after three different runs. This study has demonstrated an efficient method to obtain a highly efficient adsorbent for removing heavy metals from waste water.

Polyanionic electrically conductive superabsorbent hydrogel based on sodium alginate-g-poly (AM-co-ECA-co-AMPS): Broadband dielectric spectroscopy investigations.

In this study, the dielectric behavior of polyanionic electrically conductive superabsorbent hydrogel based on sodium alginate-g-poly(AM-co-ECA-co-AMPS) was investigated by broadband dielectric spectroscopy (BDS). The dielectric spectra obtained from -70 to 70 °C showed a superposition of three distinctive processes, electrode polarization, charge carrier's transport, and a molecular relaxation process. These dynamic processes were further analyzed along with the effect of both temperature and reduced graphene oxide (rGO) content. The development of a clear electrochemical double layer (ECDL) at the electrode/hydrogel interface strongly supports its possible application in supercapacitors' forms of energy storage. TGA, DSC, rheology, and electrochemical properties were studied. Furthermore, when the composite hydrogel with rGO content of 2.5 % was assembled into a symmetric supercapacitor, it displayed a specific capacitance of 756 F.g-1 at 1 A.g-1 and 704 F.g-1 after 5000 cycles with high capacitance retention of 93.2 %. The superior conductivity and porous structure of the rGO composite hydrogel are credited with the hydrogel's excellent electrochemical capabilities.

High performance hydrogel electrodes based on sodium alginate-g-poly(AM-c o-ECA-co-AMPS for supercapacitor application.

Electrochemical conductive hydrogels are being extensively explored in the fabrication of portable batteries and high-performance supercapacitors. Herein, the rational design of a new polyanionic electrically conductive hydrogels based on sodium alginate-g-poly(AM-co-ECA-co-AMPS) are described. rGO was incorporated into the hydrogel during the polymerization process generating rGO@ sodium alginate-g-poly(AM-co-ECA-co-AMPS) composite hydrogels to study the impact of rGO on the performance of the hydrogels. FT-IR, XRD, and SEM-EDX characterized the chemical composition, crystalline, and morphological structure of the new synthesized hydrogels. The electrochemical performance of as-synthesized hydrogels was investigated by cyclic voltammetry, galvanostatic, charge-discharge rate, and electrochemical impedance spectroscopy. The supercapacitor performance for ECH2.5 composite hydrogel showed a capacitance of 753 F. g-1 at 1 A. g-1 with good rate capability and cycling stability up to 5000 cycles. Thus, ECH2.5 hydrogel is a good candidate as electrode material in supercapacitor applications.

In situ synthesis of Fe3O4@ cyanoethyl cellulose composite as antimicrobial and semiconducting film.

Cyanoethyl cellulose (CEC)/ magnetite (Fe3O4) flexible composite film with enhanced dielectric and magnetic properties was successfully prepared. CEC has been synthesized from micro crystalline cellulose (MCC). The effects of magnetite mass fraction on the morphology, microstructure, thermal stability, and antimicrobial activity of the as-prepared composite films were investigated. The Vibrating sample magnetometer (VSM) and broadband dielectric spectrometer was also employed to study the magnetic and dielectric properties, respectively. In addition to study the computational calculation of MCC, and CEC by DFT/ B3LYP/6-31G (d) basis sets. The results showed that, the sample that is magnetite free has a diamagnetic response to the applied magnetic field, however the other samples that is loaded with magnetite show super-paramagnetic behavior indicating that the particles' sizes of the magnetite mostly below 20 nm. Also, antimicrobial activities of composite films against (G + ve), (G-ve), were investigated.

Rational design and electrical study of conducting bionanocomposites hydrogel based on chitosan and silver nanoparticles.

The chitosan/polyacrylic acid/polypyrrole/loaded with silver nanoparticles (CS/PAA/PPy/Ag-NPs) bionanocomposite as conductive, biodegradable, and biocompatible hydrogels were prepared by the casting method. Silver nanoparticles (Ag-NPs) were incorporated into the prepared bionanocomposite hydrogels to reinforce the electrical conductivity as well as the antimicrobial properties of the prepared hydrogels. The scanning electron microscopy revealed the compatibility of chitosan, polyacrylic acid, and polypyrrole, as well as Ag-NPs, were inserted in the polymer matrix and dispersed well on the superficies of the prepared bionanocomposites. X-ray diffraction displayed the presence of Ag-NPs into the polymer matrix. Also, the appearance of characteristic peaks in the Fourier transform infrared confirmed the compatibility of three polymers. Additionally, the swelling properties, antimicrobial activity as well as the electrical and dielectric characteristics of the fabricated bionanocomposites hydrogels were investigated. Moreover, the DC-conductivity was studied and our data designated that the DC-conductivity of the prepared bio-nanocomposites was improved by the existence of PPy more precisely than that of Ag-NPs. However, both were of high conductivity compared to that of the CS/PAA and found to follow the BNN universal relation. Also, The activation energy of about 55 kJ/mol of CS:2PAA hydrogel and reduce to about 15 kJ/mol in all the considered bionanocomposites after addition of Ag-NPs. Furthermore, the antibacterial activities of the knowledgeable microbes were improved as a result of the presence of Ag-NPs in bionanocomposites hydrogels.

Development of biodegradable semiconducting foam based on micro-fibrillated cellulose/Cu-NPs.

In this work regenerated cellulose was prepared by phosphoric acid as a primarily step in preparation of biodegradable foam. Copper nanoparticles (Cu-NPs) were embedded onto the cellulosic suspensions followed by freeze drying process. The scanning electron microscopy (SEM) revealed the presence of individual chunky regenerated cellulose fibers in the dimensions of micro that enhanced tendency to aggregate during drying. X-ray diffraction (XRD) demonstrated that, the treatment of cellulose with concentrated phosphoric acid led to defibrated cellulose with lower crystallinity index than original cellulose fibers. The study provided insights about the influence of the Cu-NPs on the structure, thermal stability and the electrical contributions of the considered cellulose-based foam. The electrical and dielectric properties were studied by means of the broadband dielectric spectroscopy. The dielectric spectra were dominated by an anomalous behavior of the permittivity as illustrated versus frequency of the investigated samples. The real part of conductivity follows the universal power law at higher frequencies. The foam loaded Cu-NPs exhibit biodegradability and highly efficient antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans.