A simple procedure to develop antibacterial surfaces using thiol-capped gold nanoparticles (AuNPs) is shown, which effectively kill bacteria under dark and light conditions. The effect of AuNP size and concentration on photo-activated antibacterial surfaces is reported and we show significant size effects, as well as bactericidal activity with crystal violet (CV) coated polyurethane. These materials have been proven to be powerful antibacterial surfaces against both Gram-positive and Gram-negative bacteria. AuNPs of 2, 3 or 5 nm diameter were swell-encapsulated into PU before a coating of CV was applied (known as PU-AuNPs-CV). The antibacterial activity of PU-AuNPs-CV samples was tested against Staphylococcus aureus and Escherichia coli as representative Gram-positive and Gram-negative bacteria under dark and light conditions. All light conditions in this study simulated a typical white-light hospital environment. This work demonstrates that the antibacterial activity of PU-AuNPs-CV samples and the synergistic enhancement of photoactivity of triarylmethane type dyes is highly dependent on nanoparticle size and concentration. The most powerful PU-AuNPs-CV antibacterial surfaces were achieved using 1.0 mg mL−1 swell encapsulation concentrations of 2 nm AuNPs. After two hours, Gram-positive and Gram-negative bacteria were reduced to below the detection limit (>4 log) under dark and light conditions.

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The emergence of antibiotic resistant bacteria is a major threat to the practice of modern medicine. Photobactericidal agents have obtained significant attention as promising candidates to kill bacteria, and they have been extensively studied. However, to obtain photobactericidal activity, an intense white light source or UV-activation is usually required. Here we report a photobactericidal polymer containing crystal violet (CV) and thiolated gold nanocluster ([Au 25 (Cys) 18 ]) activated at a low flux levels of white light. It was shown that the polymer encapsulated with CV do not have photobactericidal activity under white light illumination of an average 312 lux. However, encapsulation of [Au 25 (Cys) 18 ] and CV into the polymer activates potent photobactericidal activity. The study of the photobactericidal mechanism shows that additional encapsulation of [Au 25 (Cys) 18 ] into the CV treated polymer promotes redox reactions through generation of alternative electron transfer pathways, while it reduces photochemical reaction type-ІІ pathways resulting in promotion of hydrogen peroxide (H 2 O 2) production.

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High-surface area electrode materials are particularly relevant for a vast range of applications, especially in the field of catalysis and electrochemical energy conversion (e.g. fuel cells). In this work high surface area gold electrodes were produced by direct electrodeposition of highly porous gold (hPG) films onto gold electrodes via a very fast (15 sec), simple, and cost-effective methodology that involves a hydrogen bubble template. This methodology was also successfully applied to gold microelectrodes produced by lift-off lithography, thus paving the way for interesting lab-on-a-chip applications. The hPG electrodes showed very high sensitivity towards glucose, with a detection limit of 5 µM. This reactivity was maintained when the electrodes were tested in artificial urine, thus encouraging their use in healthcare. The hPG electrodes showed high sensitivity also towards other aldoses and other reducing sugars (maltose, lactose, galactose).

A highly-reproducible, high-yield flow synthesis of gold nanoparticles is developed based on synthesis kinetics from a high-pH gold precursor solution.

A microfluidic reactor offers a controllable and convenient platform for fast synthesis of gold nanoparticles with carbon monoxide.

Enzymatic biofuel cells (EBFCs) can generate energy from metabolites present in physiological fluids. They represent an attractive alternative to lithium batteries to power implantable devices, as they work at body temperature, are light and easy-to-miniaturise. To be implantable in blood vessels, EBFCs should not only be made of non-toxic and biocompatible compounds but should also be able to operate in continuous flow-through mode. The EBFC devices reported so far, however, implement carbon-based materials of questionable toxicity and stability, such as carbon nanotubes, and rely on the use of external redox mediators for the electrical connection between the enzyme and the electrode. With this study, we demonstrate for the first time continuous power generation by flow through miniature enzymatic biofuel cells fed with an aerated solution of glucose and no redox mediators. Non-toxic highly porous gold was used as the electrode material and the immobilisation of the enzymes onto the electrodes surface was performed via cost-effective and easy-to-reproduce methodologies. The results presented here are a significant step towards the development of revolutionary implantable medical devices that extract the power they require from metabolites in the body.