Bismuth-based semiconductors are promising candidates for applications in photocatalysis, photodetection, solar cells, etc. BiSI in particular is attracting attention. It has anisotropic optoelectronic properties and comprises relatively abundant elements. However, the synthesis of this ternary compound presents several challenges. Here, we delve into the underlying chemical processes that lead to the crystal growth of BiSI nanorods and optimize a solution-based synthesis. The mechanism of formation of BiSI nanocrystals is the self-sacrifice of Bi2S3 nanostructures, which also act as templates. The crystallographic similarities between the chalcogenide and the chalcohalide allow for the solid state transformation from one to the other. However, there is also a synergy with the I3 – species formed in the reaction media needed to obtain BiSI. Our method makes use of a green solvent, avoids complicated media, and drastically reduces the reaction time compared to other methods. The obtained nanorods present a band gap of 1.6 eV, in accordance with the reported values. This work presents insight into the chemistry of bismuth-based semiconductors, while introducing an easy, green, and scalable synthesis of a promising material, which could also be applied to similar compounds and other chalcoiodides, such as SbSI. In addition, the optical properties of the BiSI nanorods show their potential in photovoltaic applications.
Bismuth sulpho iodide (BiSI) belongs to the family of chalcohalides, which present several attractive electro-optic properties. In particular, BiSI is a semiconductor which could be used in X and gamma ray detection due to a band gap of 1.6 eV, density of 6.4 g cm −3 , and absorption coefficient for 60 keV radiation of 5.6 cm 2 g −1 . This work presents a facile synthesis under solvothermal conditions of a nanocomposite consisting of BiSI nanorods and amorphous carbon structures. Furthermore, it studies its ionising radiation detection properties at room temperature, when prototype detectors were built from pellets. The construction conditions of pellets were also studied, varying the applied pressure and heat treatment to the nanocomposite. Dark current density and response to different exposure rates of a 241 Am source were measured for the prototype detectors built. It was found that heat treatment of pellets considerably improves detectors performance. Dark current density was one order of magnitude lower than for the pellets without heat treatment, and its response to the 241 Am source, linear, with a signal to noise ratio of 7 for 20 V. Finally, the resistivity for the heat treated detector was in the order of 10 11 Ω cm, comparable to other materials studied for this application.
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