ABSTRACT
A novel nanocomposite has been designed and fabricated through an in situ polymerization process, based on iron oxide nanoparticles (Fe3O4 NPs), halloysite nanotubes (HNTs), and polystyrene (PS). The prepared nanocomposite (formulated as Fe3O4/HNT-PS) has been fully characterized through various methods, and its applicability in microwave absorption was investigated by using some single-layer and bilayer pellets containing nanocomposite and resin. The efficiency of the Fe3O4/HNT-PS composite with different weight ratios and pellets with the thickness of 3.0 and 4.0 mm were examined. Vector network analysis (VNA) revealed that the microwave (12 GHz) can be noticeably absorbed by Fe3O4/HNT-60% PS particles in a bilayer structure with 4.0 mm thickness and 85% resin of the pellets, resulting in a microwave absorption value of ca. -26.9 dB. The observed bandwidth (RL < -10 dB) was about 1.27 GHz, where ca. 95% of the radiated wave is absorbed. Ultimately, due to low-cost raw materials and high performance of the presented absorbent system, the Fe3O4/HNT-PS nanocomposite and the construction of the presented bilayer system can be subjected to further investigations to test and compare with other compounds for industrialization.
ABSTRACT
In the present study, Cu(ii) immobilized on an Fe3O4@HNTs-tetrazole (CFHT) nanocomposite was designed and prepared. For this, halloysite nanotubes (HNTs) as natural mesoporous substances were modified during several chemical reactions. The synthesis of the CFHT nanocomposite was investigated step by step with the required physicochemical techniques such as FT-IR, EDX, SEM, TEM, XRD, VSM, TGA and CHNS analyses. After ensuring that the nanocomposite was successfully prepared, its catalytic application in the synthesis of the 5-substituted 1H-tetrazole derivatives via multicomponent reactions (MCRs) between aromatic aldehydes, malononitrile, and sodium azide was assessed. According to the experimental results, the prepared nanocomposite exhibited excellent capability for conducting this MCR reaction. All desired products were obtained in a short reaction time (30-40 min) with high productivity (90-97%) and without a complicated workup procedure. Furthermore, the magnetic property of the synthesized heterogeneous nanocomposite empowers it to be recovered and reused in five times successive reactions without any significant reduction in reaction efficiency. Moreover, the remarkable antibacterial activity of the nanocomposite against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated by agar diffusion and plate-count methods. The zones of inhibition were around 16 and 20 mm for E. coli and S. aureus bacteria, respectively. Also, colony analysis confirms the killing of bacteria by using the CFHT nanocomposite.
