In this study, N-propyl-benzoguanamine-SO 3 H magnetic nanoparticles (MNPs) were used as a catalyst for the synthesis of new Schiff base ligands from condensation reaction of terephthalaldehyde and ortho-aniline derivatives. The bioactive ligands and their cobalt (II) complexes were characterized with nuclear magnetic resonance ( 1 H-NMR), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-Visible), mass spectroscopy studies and molar conductance. The antibacterial activity of ligands and their metal complexes were screened using disc diffusion and broth dilution methods against Escherichia coli, Serratia marcescens, Pseudomonas aeruginosa (gram negative bacteria), Bacillus Subtilis and Staphylococcus aureus (gram positive bacteria). The ligands with hydroxyl group showed better biological activity when compared to other ligands. The results showed that the metal complexes have much higher antibacterial activity compare to the parent ligands. It was found that the CoL 3 complex was more effective than other metal complexes used against all types of bacteria tested and it was more effective against Pseudomonas aeruginosa with diameter inhibition zone of 17 mm and minimal inhibitory concentration value of 0.15 mg/mL.

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Investigations were carried out to compare the effectiveness of compounds such as sodium nitrite, trisodium citrate (TSC) and TSC-zinc acetate to inhibit the corrosion of steel rebar in simulated concrete interstitial solution contaminated with chloride and to explain the mechanism of corrosion inhibition on reinforcing steel by these systems. Inhibition efficiency of these systems was studied by electrochemical techniques such as potentiodynamic polarization and half cell potential measurements. Electronic spectral studies of simulated pore solution and FT-IR spectral investigations of the film deposited on steel surface were carried out for understanding the mechanism of corrosion inhibition. Microscopic surface analysis was conducted to obtain the surface morphological behaviour of steel rebar. TSC alone was not exhibited good corrosion inhibition at very low and high concentrations according to electrochemical studies. However, in the presence of zinc acetate, corrosion protection efficiency of TSC increased appreciably. When comparing with sodium nitrite, TSC in the presence and absence of zinc acetate displayed good corrosion inhibition efficiency. Among a number of samples, TSC 100 ppm-zinc acetate 50 ppm combination showed maximum corrosion inhibition efficiency on steel rebar in simulated concrete interstitial solution.

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The aqueous extract of Tarragon, as a reducing agent, was used to synthesize silver-montmorillonite (MMT) nanocomposite (Ag-MMT-NPs) in the batch method. The leaf extract and metal solution concentrations were optimized to improve Ag-MMT-NPs synthesis in 48 h. For characterizing the nanocomposite, powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and UV-Vis spectroscopy were performed. The peak was observed at 437 nm on the UV-Vis spectrum, showing the surface plasmon resonance of Ag-MMT-NPs. Using XRD analysis, the crystalline nature and purity of Ag-MMT-NPs were confirmed. FTIR was used to evaluate specific functional groups, causing a reduction in silver nitrate during Ag-MMT-NPs formation. According to TEM, the average particle size was 25.12 nm in AgNPs. The nanocomposite showed antibacterial properties against Gram-negative and Gram-positive bacteria (Escherichia coli and Staphylococcus aureus).