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The simple preparation of Co 3 O 4 nanoparticles from a solid metallorganic molecular precursor [bis(salicylaldehydeato)cobal(II)]; [Co(sal) 2 ] has been achieved via two simple steps: firstly, the [Co(sal) 2 ] precursor was precipitated from the reaction of cobalt(II) acetate and salicylaldehyde; in propanol under nitrogen condition; then, cubic phase Co 3 O 4 nanoparticles with the size of mostly 20-30 nm could be produced by thermal treatment of the [Co(sal) 2 ] in air at 500°C for 5 h. The as-synthesized products were characterized by powder XRD, FT-IR, TEM and SEM. The results confirm that the resulting oxide was pure single-crystalline Co 3 O 4 nanoparticles. The optical absorption spectrum indicates that the direct band gaps of Co 3 O 4 nanoparticles are 1.53 and 2.02 eV. The optical property test indicates that the absorption peak of the nanoparticles shifts towards short wavelength, and the blue shift phenomenon might be ascribed to the quantum effect. The hysteresis loops of the obtained samples reveal the ferromagnetic behaviors the enhanced coercivity (H c ) and decreased saturation magnetization (M s ) in contrast to their respective bulk materials.

Background: The COVID-19 is a pandemic viral infection with a high morbidity rate, leading to many worldwide deaths since the end of 2019. The RBD (Receptor Binding Domain) of SARS-CoV-2 through its spike utilizes several host molecules to enter host cells. One of the most important ones is the angiotensin-converting enzyme 2 (ACE2), an enzyme normally engaged in renin angiotensin pathway and is responsible for hypertension regulation. As different articles have analyzed separate compounds which can bind ACE2 as the potential virus entry blockers, and each one with a different molecular docking algorithm, in this study we compared all candidate compounds individually as well as their combinations using a unique validated software to introduce most promising ones. Methods: We collected and prepared a list of all available compounds which potentially can inhibit RBD binding site of the ACE2 from different studies and then reanalyzed and compared them using the Patchdock (ver. 1.3) as a suitable molecular docking algorithm for analysis of separate compounds or their combinations. Results: Saikosaponin A (e.g. in Bupleurum chinense), Baicalin (e.g. in several species in the genus Scutellaria), Glycyrrhizin (Glycyrrhiza glabra), MLN-4760 and Umifenovir better occupied ACE2 to inhibit viral RBD binding and are suggested as the top five inhibitors of the SARS-CoV-2 binding site of ACE2. Their combinatory effects were also inspiring concurrent ACE2 blockade. Conclusion: The results propose greatest compounds and their combinatory anti-SARS-CoV-2 effects in order to decrease the time and expenses required for further experimental designs.

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