Sulfur radicals embedded in various cages of ultramarine analogs prepared from zeolites

Synthesis and characterization of amorphous aluminosilicates prepared by sol–gel to encapsulate organic dyes

“…In previous manuscripts published from other authors [15][16][17] and ourselves [18] it has been shown that it is possible to trap cationic species in some aluminosilicates. The adsorption of alizarine has been studied on aluminum gels [14].…”

“…15 MHz to obtain the 27 Al MAS NMR signals using a solution of Al(NO 3 ) 3 as an external reference. Bands were attributed from the already reported results in the bibliography.…”

Encapsulation of red sulfur chromophores in a zeolitic imidazolate framework (ZIF-8) via solvent assisted linker exchange

“…Moreover the coloration and properties of the product can be varied by varying the zeolite synthesis conditions [8]. During the preparation of zeolitic ultramarine pigments, the zeolite is heated to temperatures varying from 500 to 800 C with sodium carbonate and sulfur [12,13]. The zeolite structure types most appropriate for ultramarine preparation so far include LTA, FAU and SOD [2,8,10].…”

“…The sulfur reacts with sodium carbonate resulting in sodium polysulfides that diffuse into the zeolite cages generating the chromophores [6,14]. The formation of different color species is affected by the geometry and the size of the zeolite cage [13].…”

“…Among the sulfur species present in ultramarines, the radicals S 3 À and S 2 À are most common which correspond to blue and yellow colors respectively [4,12,15] Depending on the proportion of each radical, a green color can also be formed [12,13,16,17]. A red shade seen in some ultramarines is due to the presence of the neutral S 4 molecule [6,16,18].…”