Plasmonic SiO2/TiO2 aerogels degrade RhB
Anatase TiO2 grown in silica aerogels, then Ag@Au nanoshells, adsorbs and photocatalyzes rhodamine B far better than TiO2 powder.
Source
Plasmon-Sensitized Silica-Titanium Aerogels as Potential Photocatalysts for Organic Pollutants and Bacterial Strains
What they did
They made silica aerogels from sodium silicate, grew anatase TiO2 in the pores (TNBT, calcine 600 °C), deposited Ag nanoparticles, then seed-grew Ag@Au nanoshells. Photocatalysis used 10−5 M RhB under a 300 W xenon lamp; they also tracked ROS and antibacterial phototoxicity.
What they found
Bare SiO2 has 447.9 m2 g–1 area. Composite aerogels adsorb 56% of RhB versus 9% on TiO2 powder. Under solar light (>350 nm, 3 h) SiO2/TiO2 degrades 76% of RhB (6.3-fold vs TiO2’s 12%); SiO2 alone is 6%. Band gap of the composite is 2.3 eV versus 3.2 eV for anatase. Ag NPs average 34.7 nm; Ag@Au 97.5 nm. Excess Ag clogs pores and hurts dye degradation.
The limits
What it doesn't show
RhB is a model dye, not a real wastewater mixture. Ag@Au did not give high RhB conversion; the authors say metal loading still needs optimization. Antibacterial CFU assays are biological endpoints secondary to the materials chemistry.
Key terms
- Aerogel
- Ultralight, high-area mesoporous solid; here silica hosts TiO2 and plasmonic metals.
- Anatase TiO2
- Photocatalytic crystal phase of titania, grown in the silica and preserved by 600 °C calcination.
- LSPR
- Localized surface plasmon resonance of Ag/Au nanostructures that harvests visible light.
- Rhodamine B (RhB)
- Cationic dye used as a probe of adsorption and photocatalytic ROS chemistry.
- N-de-ethylation
- Visible-light RhB pathway driven mainly by superoxide, seen as a hypsochromic shift of λmax.
Flashcards
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Quiz yourself
Dark adsorption of RhB on SiO2/TiO2 versus TiO2 powder is about
Common questions
Why put TiO2 inside silica aerogel?
The aerogel adsorbs dye (56% vs 9% on powder) and keeps TiO2 dispersed so ROS form next to the adsorbate.
How much RhB is degraded in 3 h solar light?
76% with SiO2/TiO2 versus 12% with commercial anatase and 6% with silica alone.
What band gap is reported for the composite?
2.3 eV, lower than 3.2 eV for typical anatase.
Does more silver always help photocatalysis?
No—excess Ag blocks pores, cuts area, and speeds electron–hole recombination.
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