Acetic acid-assisted controlled hydrolysis for Br-content-dependent emission color tuning in mixed-halide BiOCl1-x Br x systems.
- 1Department of Chemistry, COMSATS University Islamabad Abbottabad Campus-22060 Pakistan [email protected] [email protected] [email protected] +92 992 383595 +92 992 383592.
- 2Civil Engineering Department, El-Madina Higher Institute for Engineering and Technology Giza 12588 Egypt [email protected].
Abstract
Controlling the emission color of bismuth oxyhalides (BiOX) remains a significant challenge, mainly because current strategies rely on multiple reagents, heterostructures, or energy-intensive synthetic routes. These approaches often disrupt the inherent structure-property relationship in these materials. In the current study, mixed bismuth oxyhalides (x = 0.0-1.0) were prepared using a simple acetate-assisted coprecipitation process. Glacial acetic acid regulated the release of Bi³⁺ ions while stabilizing the solution pH, which allowed controlled hydrolysis and halide incorporation. This strategy facilitated the preparation of BiOCl1-x Br x mixed-halides across the investigated compositional range (x = 0.0-1.0). All samples retained a tetragonal matlockite structure, matched with ICDD card No. 00-006-0249 (BiOCl) and 00-009-0393 (BiOBr), as confirmed by X-ray diffraction (XRD) analysis. As the Br⁻ content increased, the diffraction peaks shifted towards lower 2θ values. This is due to the replacement of smaller Cl⁻ ions (ionic radius = 1.81 Å) with larger Br⁻ ions (ionic radius = 1.96 Å), resulting in the gradual lattice expansion. To this effect, the lattice parameters increased from a = 3.90 Å and c = 7.41 Å (x = 0.0) to a = 3.97 Å and c = 8.31 Å (x = 1.0), indicating successful compositional modulation. It was observed that the Cl-rich sample (x = 0.0) exhibited thin flake-like morphology under scanning electron microscopy (SEM), whereas the Br-rich sample (x = 1.0) had more aggregated microplates. UV-vis spectroscopy revealed systematic tuning of the electronic structure, showing a gradual redshift of the absorption edge as the Br⁻ content increased. The band gap decreased from 2.70 eV to 2.18 eV, due to a stronger contribution of Br⁻ 4p orbitals to the valence band maximum. The formation of shoulders and broad absorption further explained the presence of Bi-Cl and Bi-Br bonding environments. The photoluminescence response was directly affected by these electronic changes. The emissions, including near-band-edge (∼330 nm), shallow, and deep defect emissions (∼420-480 nm), created a smooth color shift from blue to green-yellow. CIE chromaticity coordinates affirmed tunability of color with color purity exceeding 80 ± 5%. Based on optical analysis, a schematic band diagram shows an increase in the valence band with Br⁻ content. Overall, halide substitution in BiOCl1-x Br x controls lattice expansion, modulates band gap, and tunes emission color. The acetate-assisted hydrolysis methodology is thus a scalable platform for luminescent BiOCl1-x Br x materials without the use of surfactants or any external pH-regulator.
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BibTeX
@article{saleem2026acetic,
title = {{Acetic acid-assisted controlled hydrolysis for Br-content-dependent emission color tuning in mixed-halide BiOCl1-x Br x systems.}},
author = {Afsah Saleem and Asad M Khan and Ahmad K Badawi and Bushra Ismail},
journal = {Nanoscale advances},
year = {2026},
month = oct,
doi = {10.1039/d6na00183a},
url = {https://europepmc.org/article/MED/42948703},
note = {CC BY},
}
RIS
TY - JOUR
TI - Acetic acid-assisted controlled hydrolysis for Br-content-dependent emission color tuning in mixed-halide BiOCl1-x Br x systems.
AU - Afsah Saleem
AU - Asad M Khan
AU - Ahmad K Badawi
AU - Bushra Ismail
PY - 2026
DA - 2026/10/27
JO - Nanoscale advances
DO - 10.1039/d6na00183a
UR - https://europepmc.org/article/MED/42948703
AB - Controlling the emission color of bismuth oxyhalides (BiOX) remains a significant challenge, mainly because current strategies rely on multiple reagents, heterostructures, or energy-intensive synthetic routes. These approaches often disrupt the inherent structure-property relationship in these materials. In the current study, mixed bismuth oxyhalides (x = 0.0-1.0) were prepared using a simple acetate-assisted coprecipitation process. Glacial acetic acid regulated the release of Bi³⁺ ions while stabilizing the solution pH, which allowed controlled hydrolysis and halide incorporation. This strategy facilitated the preparation of BiOCl1-x Br x mixed-halides across the investigated compositional range (x = 0.0-1.0). All samples retained a tetragonal matlockite structure, matched with ICDD card No. 00-006-0249 (BiOCl) and 00-009-0393 (BiOBr), as confirmed by X-ray diffraction (XRD) analysis. As the Br⁻ content increased, the diffraction peaks shifted towards lower 2θ values. This is due to the replacement of smaller Cl⁻ ions (ionic radius = 1.81 Å) with larger Br⁻ ions (ionic radius = 1.96 Å), resulting in the gradual lattice expansion. To this effect, the lattice parameters increased from a = 3.90 Å and c = 7.41 Å (x = 0.0) to a = 3.97 Å and c = 8.31 Å (x = 1.0), indicating successful compositional modulation. It was observed that the Cl-rich sample (x = 0.0) exhibited thin flake-like morphology under scanning electron microscopy (SEM), whereas the Br-rich sample (x = 1.0) had more aggregated microplates. UV-vis spectroscopy revealed systematic tuning of the electronic structure, showing a gradual redshift of the absorption edge as the Br⁻ content increased. The band gap decreased from 2.70 eV to 2.18 eV, due to a stronger contribution of Br⁻ 4p orbitals to the valence band maximum. The formation of shoulders and broad absorption further explained the presence of Bi-Cl and Bi-Br bonding environments. The photoluminescence response was directly affected by these electronic changes. The emissions, including near-band-edge (∼330 nm), shallow, and deep defect emissions (∼420-480 nm), created a smooth color shift from blue to green-yellow. CIE chromaticity coordinates affirmed tunability of color with color purity exceeding 80 ± 5%. Based on optical analysis, a schematic band diagram shows an increase in the valence band with Br⁻ content. Overall, halide substitution in BiOCl1-x Br x controls lattice expansion, modulates band gap, and tunes emission color. The acetate-assisted hydrolysis methodology is thus a scalable platform for luminescent BiOCl1-x Br x materials without the use of surfactants or any external pH-regulator.
SN - 2516-0230
ER -