Two unique materials were developed, like graphene oxide (GO) sheets covalently grafted on to barium titanate (BT) nanoparticles and cobalt nanowires (Co-NWs), to attenuate the electromagnetic (EM) radiations in poly(vinylidene fluoride) (PVDF)-based composites. The rationale behind using either a ferroelectric or a ferromagnetic material in combination with intrinsically conducting nanoparticles (multiwall carbon nanotubes, CNTs), is to induce both electrical and magnetic dipoles in the system. Two key properties, namely, enhanced dielectric constant and magnetic permeability, were determined. PVDF/BT-GO composites exhibited higher dielectric constant compared to PVDF/BT and PVDF/GO composites. Co-NWs, which were synthesized by electrodeposition, exhibited saturation magnetization (Ms) of 40 emu/g and coercivity (Hc) of 300 G. Three phase hybrid composites were prepared by mixing CNTs with either BT-GO or Co-NWs in PVDF by solution blending. These nanoparticles showed high electrical conductivity and significant attenuation of EM radiations both in the X-band and in the Ku-band frequency. In addition, BT-GO/CNT and Co-NWs/CNT particles also enhanced the thermal conductivity of PVDF by ca. 8.7- and 9.3-fold in striking contrast to neat PVDF. This study open new avenues to design flexible and lightweight electromagnetic interference shielding materials by careful selection of functional nanoparticles.

The study reports the optimized incorporation of pyridinic nitrogen in nitrogen-doped carbon nanotubes (CNTs) to realize effective Fe-N x centers throughout the framework. The study unveils nitrogen as a valuable asset to promote the homogeneous dispersion of Fe moieties throughout the CNT framework, which is a necessary component to institute uniform Fe-N x centers. In addition, pyridinic nitrogen causes disruption in strongly delocalized π-electrons, which impart electron-withdrawing nature in the carbon matrix, resulting in an anodic shift in oxygen reduction reaction (ORR) onset potential (E onset). The direct interaction of Fe-N x with O2, as evidenced by poisoning and computational studies, ensures the preferential inner sphere electron transfer mechanism. Despite the alkaline medium, the outer sphere electron transfer mechanism was muted, with suppressed HO2 – generation, preferential 4e– reduction pathways, and excellent cyclic stability. The study indicates the dependency of ORR half-wave potential on the electron transfer mechanism. The poisoning study unveils the direct involvement of Fe-N x electroactive centers in facilitating ORR in alkaline medium. It further indicates a noticable increase (up to ∼25%) in peroxide generationan unwanted ORR intermediateand concomitant reduction in average electron transfer no. per oxygen molecule.

The production of hydroxyapatite (HAP) composite coatings has continuously been experimented for bone tissue applications during the last decades due to its significant bioactivity and osteoconductivity. This report unravels the...

No abstract

Polyacrylamide-based hydrogels are widely used as potential candidates for cartilage replacement. However, their bioapplicability is sternly hampered due to their limited mechanical strength and puncture resistance. In the present work, the strength of polyacrylamide (PAM) hydrogels was increased using titanium oxide (TiO2) and carbon nanotubes (CNTs) separately and a combination of TiO2 with CNTs in a PAM matrix, which was interlinked by the bonding between nanoparticles and polymers with the deployment of density functional theory (DFT) approach. The synergistic effect and strong interfacial bonding of TiO2 and CNT nanoparticles with PAM are attributed to high compressive strength, elastic modulus (>0.43 and 2.340 MPa, respectively), and puncture resistance (estimated using the needle insertion test) for the PAM–TiO2–CNT hydrogel. The PAM–TiO2–CNT composite hydrogel revealed a significant self-healing phenomenon along with a sign toward the bioactivity and cytocompatibility by forming the apatite crystals in simulated body fluid as well as showing a cell viability of ∼99%, respectively. Furthermore, for new insights on interfacial bonding and structural and electronic features involved in the hydrogels, DFT was used. The PAM–TiO2–CNT composite model, constructed by two interfaces (PAM–TiO2 and PAM–CNT), was stabilized by H-bonding and van der Waals-type interactions. Employing the NCI plot, HOMO–LUMO gap, and natural population analysis tools, the PAM–TiO2–CNT composite has been found to be most stable. Therefore, the prepared polyacrylamide hydrogels in combination with the TiO2 and CNT can be a remarkable nanocomposite hydrogel for cartilage repair applications.