Understanding the Crystal Growth of Bismuth Chalcohalide Nanorods through a Self-Sacrificing Template Process: A Comprehensive Study

Abstract

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.

( Bi 19 S 27 I 3 ) 0.6667 nanorods with more negative potentials of conduction band as highly active photocatalysts under visible light

“…It is well known that the morphology and crystalline phase of crystals are strongly influenced by the reaction conditions and their own crystal structure. [25][26][27] The nanoparticles gradually grow into short nanorods in the effect of mannitol long-chain molecules and the crystal structure of (Bi 19 S 27 I 3 ) 0.6667 . [28][29][30] And it finally grows into a uniform nanorod after the hydrothermal reaction for 4 hours.…”

“…(Bi 19 S 27 I 3 ) 0.6667 nuclei are then grown into nanoparticles under hydrothermal conditions, which agglomerated into nano‐spheres likely due to surface electrostatic forces between nanoparticles. It is well known that the morphology and crystalline phase of crystals are strongly influenced by the reaction conditions and their own crystal structure 25‐27 . The nanoparticles gradually grow into short nanorods in the effect of mannitol long‐chain molecules and the crystal structure of (Bi 19 S 27 I 3 ) 0.6667 28‐30 .…”

Recent Development Strategies for Bismuth‐Driven Materials in Sustainable Energy Systems and Environmental Restoration

“…[ 66,67 ] For example, BiTeCl compounds consist of layered [BiTe] + with a hexagonal structure and a P6 3 mc space group, whereas BiTeBr and BiTeI are arranged into the P$$\overline 3 $$m1 and P3m1 space groups, respectively. [ 68,69 ] The structural differences between Bi 2 S 3 and BiSI are summarized in Figure , [ 70 ] where BiSI is prepared through the self‐sacrifice of the Bi 2 S 3 nanostructure.…”

“…Parallel view to the c-axis of a) Bi 2 S 3 and c) Bi 2 S 2 I 2 in a 1 × 1 × 5 expanded cell (violet, yellow, and green represent Bi, S, and I, respectively),and b) partial Bi 2 S 3 dissolution mechanism for the entry of iodine atoms. Reproduced with permission [70]. Copyright 2022, American Chemical Society.…”

Mist Chemical Vapor Deposition of Bi13S18I2 for Photoelectrochemical-type Photodetection

“…Their peculiar electronic structures arise from the hybridization of cation s-orbitals with anion p-orbitals, leading to antibonding character of the top of the valence band and extended p-states at the bottom of the conduction band. This highly dispersive band nature brings high charge carrier mobility and defect tolerance. ,,, Meanwhile, the incorporation of different anions into the crystal structure can effectively modulate its properties, such as changing the bandgap or inducing ferromagnetism. − For instance, despite the similar Bi:S molar ratio and crystal structure for the Bi 2 S 3 and Bi 13 S 18 I 2 , the bandgap of Bi 13 S 18 I 2 was much narrower than that of Bi 2 S 3 . Additionally, bismuth is a kind of green element with low toxicity. − These merits mentioned above make bismuth-based ternary compounds suitable for a range of applications, including photocatalysis, energy storage, and sensing. − , …”