Synthesis of gold/polydopamine composite surfaces on glass substrates for localized surface plasmon resonance and catalysis

Composite materials of polydopamine (PDA) and gold nanoparticles on glass substrates (Au/PDA@slide) were obtained via a simple chemical process. First, PDA films (PDA@slide) were formed by immersing slides in 20mg ml(-1) dopamine aqueous solution at pH=8.5 for 1h. Then, PDA@slide was dipped in 0.02M chloroauric acid (HAuCl4) aqueous solution for a certain time, Au/PDA@slide being formed. Gold nanoparticles were obtained by the reductive properties of PDA. The morphology and chemical composition of the composite material were characterized using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The catalytic properties of Au/PDA@slide were evaluated using the reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydride (NaBH4) aqueous solution at room temperature. The catalytic activity of the optimal Au/PDA@slide was so satisfactory that the reduction of 4-NP was completed within 10min. Moreover, the Au/PDA@slide composite material was stable up to five cycles without significant loss of its catalytic activity. In addition, Au/PDA@slide also exhibited photocatalytic ability, photodegrading 2.5ml of 17.5mg l(-1) methyl orange in 100min. By measuring the UV-visible absorption bands of Au/PDA@slide, it was proved that the condition of the strongest surface plasmon resonance of Au/PDA@slide was the optimal condition for catalytic reduction of 4-NP.