The proposed experiment can help students to understand the factors involved in the stability of gold nanoparticles (Au NPs) by exploring the adsorption interaction between Au NPs and various substances. The students in this study found that the surface plasmon resonance band of Au NP solutions underwent a red shift (i.e., from 520 to 650 nm) because of NaCl-induced aggregation caused by the elimination of the repulsive electrostatic force. In addition, a sufficient amount of bovine serum albumin molecules (29.4 nM) adsorbed on the surface of Au NPs (1.8 nM) through electrostatic interactions provides steric barriers that hinder electrolyte-induced aggregation. This experiment was performed in the fall 2014 semester to improve the recognition of nanoscale science and engineering concepts of undergraduates.

This study demonstrated facile synthesis of silver phosphate (Ag3PO4) photocatalysts for the degradation of organic contaminants. Ag3PO4 microparticles from different concentrations of precursor, AgNO3, were produced and characterized by scanning electron microscopy, powder X-ray diffraction, and UV–visible diffuse reflectance spectroscopy. Degradation rates of methylene blue (MB) and phenol were measured in the presence of microparticles under low-power white-light light-emitting-diode (LED) irradiation and the reaction rate followed pseudo-first-order kinetics. The prepared Ag3PO4 microparticles displayed considerably high photocatalytic activity (>99.8% degradation within 10 min). This can be attributed to the microparticles’ large surface area, the low recombination rate of electron–hole pairs and the higher charge separation efficiency. The practicality of the Ag3PO4 microparticles was validated by the degradation of MB, methyl red, acid blue 1 and rhodamine B under sunlight in environmental water samples, demonstrating the benefit of the high photocatalytic activity from Ag3PO4 microparticles.

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Facile synthesis of silver phosphate (Ag 3 PO 4) microcrystals was developed for the novel application in the disinfection of pathogens with visible light. Ag 3 PO 4 microcrystals from different synthesis routes were produced and characterised by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The antibacterial activity of the Ag 3 PO 4 microcrystals was also evaluated for its effectiveness in eradicating pathogens (Escherichia coli and Staphylococcus aureus) under white-light light-emitting-diode irradiation. The prepared Ag 3 PO 4 microcrystals displayed higher and more stable photocatalytic antibacterial activity (>99% eradication rate within 10 min) comparing to Ag + ions used only. This can be attributed to the oxidation of the photogenerated hole and the adsorption of Ag + ions. This study demonstrated the strong photocatalytic activity of the as-prepared Ag 3 PO 4 microcrystals, promising for industrial applications related to the eradication of pathogens from wastewater.