Physicochemistry of dispersions of HgO, HgS and ‘Makardhwaj’ (an Ayurvedic medicine) prepared in micelle and microemulsion templates

Micelle and microemulsion templates are used to prepare dispersions of HgO and HgS. The prepared HgO dispersions are obtained in four different colors viz. yellow, orange, red, and bluish-white, though the bulk HgO shows only two colors, red and yellow. The synthesized HgS particles in micellar solutions appear faintly grayish. These dispersions of HgO and HgS show characteristic spectral features. They are characterized by spectral, X-ray diffraction (XRD) and transmission electron microscopic (TEM) techniques. The products formed in water/CTAB + n-butanol/n-heptane microemulsion (CTAB being cetyltrimethylammonium bromide) evidence characteristic differences from that prepared in micellar media. Both HgO and HgS preparations show low semiconductivity. Their band gaps range between 3.6 and 5.71 eV. HgO dispersions prepared in Triton X-100 (TX-100) micellar solution are spherical (∼150 nm diameter) whereas that prepared in Tween-20 (TW-20) medium are prolate type (major axis ∼300 nm). In CTAB micellar solution tubes of diameter 150 nm are formed. The HgS preparation in the aforesaid w/o microemulsion appears grayish and transparent. The shapes of the particles are spherical with a size in the range 10–25 nm as found from the TEM study. ‘Makardhwaj’, an Ayurvedic medicine (comprising of HgS, Au and Au2S), also shows characteristic spectral features in micellar and microemulsion media. The grinded dispersed ‘Makardhwaj’ particles are nearly spherical with average size of 10 nm, and evidence the presence of Au, S and Hg in the ratio 1:3.4:30 from electron dispersive X-ray analysis (EDAX) measurements. The results suggest that HgS dispersions fall well within the conventional nano-domain (100 nm) whereas HgO dispersions are moderately out of the domain.