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Novel Precursors for the Controlled Aqueous Synthesis of Bismuth Oxyhalides.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Novel Precursors for the Controlled Aqueous Synthesis of Bismuth Oxyhalides./
Author:	Gordon, Matthew Nathan.
Description:	1 online resource (226 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-02, Section: B.
Contained By:	Dissertations Abstracts International85-02B.
Subject:	Inorganic chemistry. -
Online resource:	click for full text (PQDT)
ISBN:	9798380152068

Novel Precursors for the Controlled Aqueous Synthesis of Bismuth Oxyhalides.
Gordon, Matthew Nathan.

Novel Precursors for the Controlled Aqueous Synthesis of Bismuth Oxyhalides. - 1 online resource (226 pages)

Source: Dissertations Abstracts International, Volume: 85-02, Section: B.

Thesis (Ph.D.)--Indiana University, 2023.

Includes bibliographical references

Bismuth oxyhalides (BiOX, X = Cl, Br) are promising layered photocatalysts that can produce H2 using solar light. The layered crystal structures allow for band gap tuning through compositional flexibility and also minimize electron−hole recombination in these materials. These materials are often synthesized in aqueous media but with poor synthetic control resulting from the extremely fast nucleation and growth rates of the particles, caused by the rapid precipitation of bismuth salts with free halide ions. To overcome this challenge, unique precursors were required that first, allow Bi3+ to be soluble in water, and second, introduce halides into the reaction solution in a controlled manner. By developing these precursors, a new level of controlled aqueous synthesis of bismuth oxyhalides could be achieved. A bismuth-lactate complex was identified as a water-soluble bismuth source and small organohalide molecules were used as halide sources. Using a rapid and scalable ultrasonic spray synthesis technique, these precursors were spatially and temporally confined in the aerosol phase with molten salt fluxes. This process allowed the formation of single-crystalline BiOX nanoplates to be produced continuously. Mechanistic studies revealed that, with the application of heat, halide ions are released by an SN2 reaction with water. These released free halide ions then precipitate with bismuth ions as BiOX (X = Cl, Br). By controlling the halide ion formation rate via temperature, the nucleation and growth rates of BiOX materials can be tuned to provide synthetic control. Further developing this class of reagents, the halide functional group was directly added onto the ligand coordinated to bismuth to form single-source precursors and characterized by solving their crystal structures. The single-source precursors allow the halide ion to be released in close proximity to the Bi3+ ion further controlling the formation processes. The diverse potential of these precursors is demonstrated by synthesizing BiOX in three ways: aqueous colloidal synthesis, solid-state decomposition, and fabrication of films of BiOX via spray pyrolysis of the aqueous precursor solutions. These broadly applicable single-source precursors will enhance the ability to synthesize future BiOX materials with controlled morphologies. Using these novel single-source precursors, the nucleation and growth of bismuth oxyhalides can be slowed significantly. Through this advance, these slowed processes were now able to be investigated to gather mechanistic insights. Two techniques, in situ X-ray pair distribution function and in situ liquid cell transmission electron microscopy were combined to investigate the early stages of BiOCl particle formation as it occurs. In situ pair distribution function analysis of X-ray total scattering data allows us to probe the local order of atomic structures throughout the synthesis from precursor to product. Complementarily, in situ liquid cell transmission electron microscopy provides a visual look at the particles as they form which can be tracked. Through this work, mechanistic insights into the nucleation and growth of BiOCl were found. The slowed formation of BIOX is achieved for the first time using the newly developed precursors. As photocatalytic reactions are surface-mediated, control of crystallinity and exposed facets is crucial. With the BiOX formation rate slowed, additional reagents and conditions could be used to influence the resulting particle morphology. It is envisioned that this novel class of precursors can be used to further develop future controlled BiOX materials for improved photocatalysis.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798380152068Subjects--Topical Terms:

1182077
Inorganic chemistry.
Subjects--Index Terms:

Aqueous synthesisIndex Terms--Genre/Form:

554714
Electronic books.

Novel Precursors for the Controlled Aqueous Synthesis of Bismuth Oxyhalides.
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520 $a Bismuth oxyhalides (BiOX, X = Cl, Br) are promising layered photocatalysts that can produce H2 using solar light. The layered crystal structures allow for band gap tuning through compositional flexibility and also minimize electron−hole recombination in these materials. These materials are often synthesized in aqueous media but with poor synthetic control resulting from the extremely fast nucleation and growth rates of the particles, caused by the rapid precipitation of bismuth salts with free halide ions. To overcome this challenge, unique precursors were required that first, allow Bi3+ to be soluble in water, and second, introduce halides into the reaction solution in a controlled manner. By developing these precursors, a new level of controlled aqueous synthesis of bismuth oxyhalides could be achieved. A bismuth-lactate complex was identified as a water-soluble bismuth source and small organohalide molecules were used as halide sources. Using a rapid and scalable ultrasonic spray synthesis technique, these precursors were spatially and temporally confined in the aerosol phase with molten salt fluxes. This process allowed the formation of single-crystalline BiOX nanoplates to be produced continuously. Mechanistic studies revealed that, with the application of heat, halide ions are released by an SN2 reaction with water. These released free halide ions then precipitate with bismuth ions as BiOX (X = Cl, Br). By controlling the halide ion formation rate via temperature, the nucleation and growth rates of BiOX materials can be tuned to provide synthetic control. Further developing this class of reagents, the halide functional group was directly added onto the ligand coordinated to bismuth to form single-source precursors and characterized by solving their crystal structures. The single-source precursors allow the halide ion to be released in close proximity to the Bi3+ ion further controlling the formation processes. The diverse potential of these precursors is demonstrated by synthesizing BiOX in three ways: aqueous colloidal synthesis, solid-state decomposition, and fabrication of films of BiOX via spray pyrolysis of the aqueous precursor solutions. These broadly applicable single-source precursors will enhance the ability to synthesize future BiOX materials with controlled morphologies. Using these novel single-source precursors, the nucleation and growth of bismuth oxyhalides can be slowed significantly. Through this advance, these slowed processes were now able to be investigated to gather mechanistic insights. Two techniques, in situ X-ray pair distribution function and in situ liquid cell transmission electron microscopy were combined to investigate the early stages of BiOCl particle formation as it occurs. In situ pair distribution function analysis of X-ray total scattering data allows us to probe the local order of atomic structures throughout the synthesis from precursor to product. Complementarily, in situ liquid cell transmission electron microscopy provides a visual look at the particles as they form which can be tracked. Through this work, mechanistic insights into the nucleation and growth of BiOCl were found. The slowed formation of BIOX is achieved for the first time using the newly developed precursors. As photocatalytic reactions are surface-mediated, control of crystallinity and exposed facets is crucial. With the BiOX formation rate slowed, additional reagents and conditions could be used to influence the resulting particle morphology. It is envisioned that this novel class of precursors can be used to further develop future controlled BiOX materials for improved photocatalysis.
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653 $a Nanomaterials
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