研究目的
To cover the relatively new and rapidly expanding types of water-soluble titanium-oxide based structures, including new clusters stabilized by small organic ligands, small inorganic anions, and by polyoxometalates, and water-soluble or dispersible TiO2 nanocrystals, with an emphasis on isolation, solution-state characterization, aqueous stability, and applications.
研究成果
The review establishes a continuum from small molecular clusters to larger nanocrystals, blurring the divide between molecular and colloid science. It emphasizes the role of polyoxometalate ligands in stabilizing titanium-oxide structures and enabling solution-state studies and applications, such as photocatalysis. Future perspectives include using rationally modifiable POM properties to control metal-oxide nanocrystal reactivities.
研究不足
The review highlights challenges such as the instability of many titanium-oxide clusters in water, limited examples of water-soluble TiO2 nanocrystals, and the need for specific reaction conditions (e.g., low pH) to maintain solubility and stability. It also notes that many structures are pH-sensitive and may degrade or aggregate under certain conditions.
1：Experimental Design and Method Selection:
The review synthesizes existing literature on water-soluble titanium-oxide structures, focusing on synthesis methods involving hydrolysis of titanium salts in aqueous or mixed solvents, use of stabilizing ligands (e.g., sulfate, polyoxometalates, organic acids), and characterization techniques such as X-ray crystallography, NMR spectroscopy, ESI-MS, TEM, and DLS.
2：Sample Selection and Data Sources:
Samples include various titanium-oxide clusters and nanocrystals isolated from reactions involving titanium precursors (e.g., TiCl4, TiOSO4, titanium alkoxides) with ligands like glycolic acid, sulfate, polyoxometalates, and polyethylene glycol, under controlled pH and temperature conditions.
3：List of Experimental Equipment and Materials:
Equipment includes instruments for synthesis (e.g., reactors, hydrothermal setups), characterization (e.g., XRD, NMR spectrometers, ESI-MS, TEM, DLS), and materials such as titanium salts, ligands, solvents (e.g., water, MeCN, DMSO), and counter ions (e.g., alkylammonium cations).
4：Experimental Procedures and Operational Workflow:
Procedures involve mixing titanium precursors with ligands in specific ratios, adjusting pH, heating or aging, purification by precipitation or crystallization, and characterization using spectroscopic, microscopic, and electrochemical methods.
5：Data Analysis Methods:
Data analysis includes interpretation of NMR spectra, mass spectra, TEM images, DLS measurements, and electrochemical data to confirm structure, stability, and properties.
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