Fabrication of a hybrid nano-pigment based on sodium montmorillonite nanoclay and Hibiscus sabdariffa flower powder and assessment of their thermal and antimicrobial properties

In the present study, dyes derived from the Hibiscus sabdariffa flower (Hs) were successfully entered into the space inside the sodium montmorillonite clay layer (Na+-MMT) caused by the ion exchange reaction, and a hybrid nano-pigment called (Hs-MMT) was formed. To investigate and characterize the morphology of the Hs-MMT nano-pigment, Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), field emission scanning electron microscope (FESEM), and energy dispersive spectroscopy (EDS) were used. Also, both the thermal and antimicrobial behavior of Hs-MMT nano-pigment was evaluated by thermogravimetric analysis (TGA) and well and disc methods, respectively. The results of FTIR, SAXS, and EDS analyses showed that after the interaction of two organic and inorganic phases, the functional groups of Hs appeared on the nanoclay, and also the insertion of Hs dyes in the spaces between the layers of the nanoclay increased the surface by 5.72 angstrom .The TGA results indicated that the nanoclay plates prevented heat loading on the structure of Hs dyes and caused the thermal stability of Hs-MMT nano-pigments. Finally, the results of the antimicrobial test confirmed that Hs-MMT nano-pigment could hinder and destroy two types of gram-positive bacteria and two types of gram-negative bacteria, in such a way that the minimum bactericidal concentration of gram-positive bacteria i.e., Staphylococcus aureus and Streptococcus pyogenes was equal to 250 and 31.25 microgram per milliliter, respectively, while the minimum bactericidal concentration of gram-negative bacteria i.e., Escherichia coli and Salmonella paratyphi was equal to 1000 microgram per milliliter.