研究目的
To investigate the p-n heterojunction of Ag2O and TiO2 for photocatalytic decomposition of organic compounds and the inactivation of microorganisms in dependence on the titania matrix (anatase, rutile and mixed-phase titania).
研究成果
Ag2O/TiO2 heterojunctions prepared by simple grinding exhibited enhanced photocatalytic activity under UV/vis and vis irradiation, with mechanisms depending on the titania matrix (e.g., Z-scheme for anatase, p-n junction for rutile). They also showed improved antimicrobial properties, particularly under vis light due to electrostatic interactions. The composites are more stable than bare Ag2O, making them suitable for broad applications in environmental remediation and disinfection.
研究不足
The study used specific TiO2 samples and Ag2O, which may limit generalizability. The grinding method might not ensure uniform distribution in all cases. Antimicrobial tests showed variability, especially with fungi, and the mechanisms proposed are based on correlations rather than direct evidence. Stability and recyclability of bare Ag2O were issues, and the inner-filter effect at higher Ag2O content reduced activity.
1：Experimental Design and Method Selection:
The study involved preparing Ag2O/TiO2 composites by physical grinding of Ag2O with various TiO2 samples to form heterojunctions. The rationale was to enhance charge separation and visible light response. Methods included DRS, XRD, STEM-EDS for characterization, and photocatalytic and antimicrobial activity tests under different light conditions.
2：Sample Selection and Data Sources:
Six commercial TiO2 samples (P25, ST01, ST41, TIO6, RUT, RUT') and Ag2O from Wako Pure Chemicals were used. Microorganisms included Escherichia coli, Candida albicans, and Penicillium chrysogenum.
3：List of Experimental Equipment and Materials:
Equipment included JASCO V-670 for DRS, Rigaku SmartLab for XRD, HD-2000 STEM-EDS, atomic absorption spectroscopy (AAS), gas chromatography (GC-TCD, GC-FID), liquid chromatography (HPLC), Xe lamps with filters for irradiation, and various chemicals like acetic acid, methanol, phenol, 2-propanol, and culture media.
4：Experimental Procedures and Operational Workflow:
Composites were prepared by grinding Ag2O and TiO2 in an agate mortar. Photocatalytic tests involved suspending photocatalysts in reactant solutions, irradiating under UV/vis or vis light, and analyzing products. Antimicrobial tests used suspension and spore-counting methods with irradiation or dark conditions, followed by colony counting.
5：Data Analysis Methods:
Data were analyzed using chromatography for product quantification, XRD with Scherrer equation for crystallite size, and statistical analysis of colony counts. Software tools were not specified.
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JASCO V-670
V-670
JASCO
Used for recording UV/vis diffuse reflectance spectra (DRS).
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X-ray diffractometer
SmartLab
Rigaku
Used for collecting X-ray powder diffraction (XRD) patterns.
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Scanning transmission electron microscopy
HD-2000
HITACHI
Used for observing morphology and distribution of Ag2O with EDS.
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AEROXIDE TiO2 P25
P25
Nippon Aerosil
Used as a titania photocatalyst sample in the preparation of Ag2O/TiO2 composites.
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ST-01
ST01
Ishihara Sangyo
Used as a titania photocatalyst sample (anatase-predominant).
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ST-41
ST41
Ishihara Sangyo
Used as a titania photocatalyst sample (anatase-predominant).
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TIO-6
TIO6
Catalysis Society of Japan
Used as a titania photocatalyst sample (rutile-predominant).
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Rutile nanopowder
RUT
Merck
Used as a titania photocatalyst sample (rutile-predominant).
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Predominantly rutile
RUT'
Merck
Used as a titania photocatalyst sample (rutile-predominant).
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Ag2O
Wako Pure Chemicals
Used as the modifying agent to prepare Ag2O/TiO2 composites.
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Atomic absorption spectroscopy
Used for estimating silver content after dissolution.
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Xe lamp
Used as the light source for photocatalytic and antimicrobial activity tests.
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Gas chromatography
GC-TCD, GC-FID
Used for analyzing gas phases (e.g., CO2, H2, acetone).
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Liquid chromatography
HPLC
Used for analyzing liquid phases (e.g., phenol, benzoquinone).
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Plate count agar
Becton, Dickinson and Company
Used for culturing bacteria in antimicrobial tests.
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Sabouraud dextrose agar
Becton, Dickinson and Company
Used for culturing fungi in antimicrobial tests.
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Malt Extract Agar
Merck
Used for preparing agar slants in fungal spore counting tests.
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