Bismuth subcarbonate (BiO)<sub>2</sub>CO<sub>3</sub>, sometimes written Bi<sub>2</sub>O<sub>2</sub>(CO<sub>3</sub>) is a chemical compound of bismuth containing both oxide and carbonate anions. Bismuth is in the +3 oxidation state. Bismuth subcarbonate occurs naturally as the mineral bismutite. Its structure consists of BiâÂÂO layers and CO<sub>3</sub> layers and is related to kettnerite, CaBi(CO<sub>3</sub>)OF. It is light-sensitive.
It is highly radiopaque and for example is used as a filler in radiopaque catheters which can be seen by x-ray. In modern medicine, bismuth subcarbonate has been made into nanotube arrays that exhibit antibacterial properties. It is also used in fireworks to make Dragon's eggs. It is a constituent of milk of bismuth which was a popular digestive tract panacea in the 1930s.
Bismuth subcarbonate may be harmful if swallowed. It may irritate the respiratory and gastrointestinal tract.
Bismuth subcarbonate can be attained from the reaction between bismuth nanoparticles and the atmospheric carbon dioxide (CO<sub>2</sub>) dissolved in water. Bismuth subcarbonate has the tendency to form nanoplates, but it can be also obtained as small round nanospheres (with controlled size) when it is grown in the presence of halloysite nanotubes. The high pH and high temperature of the aqueous solution helps to reduce the time of synthesis. It is readily formed on the surface of undoped bismuth oxide (ò-Bi<sub>2</sub>O<sub>3</sub> and ó-Bi<sub>2</sub>O<sub>3</sub>) nanoparticles even when they are not suspended in water.
Bismuth subcarbonate has a structure with a tetragonal unit cell. Layers of (BiO)<sub></sub> positively charged, and carbonate anion (CO) are surrounding both sides of the (BiO) layer to compensate the charge. Usually, the (BiO)<sub></sub> layer grows perpendicular to the axis.