Mechanisms of Highly Efficient Photocatalytic Pollutant Degradation by Au/TiO2 Janus Nanoparticles

05 September 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Semiconductor nanoparticles partially coated with metals have been widely used to degrade contaminants in water, but the physical mechanisms underlying degradation are poorly understood, limiting their real-world implementation. Here, we reveal the degradation mechanisms that dominate when gold-coated titanium dioxide (Au/TiO2) “Janus” nanoparticles (JNPs) are irradiated with monochromatic ultraviolet light (254 nm and 365 nm wavelengths) to degrade 1,4-dioxane, a carcinogenic model pollutant. To do so, we performed experiments with ultraviolet light at different wavelengths with and without radical quenching, extensive JNP characterization (SEM, XRD, EDS, DLS, and UV-Vis), and 3D simulations of self-propulsion and light-matter interactions. We traced the enhanced photocatalytic activity of Au-coated JNPs to both increased light absorption due to Au acting as an optical antenna, and inhibited recombination of photogenerated electrons and holes. These two effects increase the production of hydroxyl radicals, accelerating the degradation of 1,4-dioxane. The reduced electron/hole recombination is due to two factors: the Schottky barrier that forms between Au and TiO2 (which drives photogenerated electrons from TiO2 into the metal), and stoichiometric changes in the TiO2 that accompany gold sputtering which facilitate electron sequestration by the metal. In contrast, self-propulsion and surface plasmon resonance play at most a minor role.


Pollutant Degradation
Janus Nanoparticle
Advanced oxidation processes
Water treatment
Contaminant removal

Supplementary materials

Supporting Information
We provide a list of figures that help visualize and understand our experimental processes, and data, and give more support for the conclusions reached in the main text. Figures S1-S4 provide more background on the structure of our particles, how they are created and the hypothesis mechanism of degradation. Figures S5 and S6 result from COMSOL simulations to explore the effect of motion on the degradation of 1,4-dioxane. Table S1 summarizes differing effects used to explain enhanced photodegradation of Janus nanoparticles, how our study examined this effect, and our nominal conclusion as to its importance for the results observed within the main text.  


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