The fabrication of antimicrobial surfaces that exhibit enhanced activity towards a large variety of microbial species is one of the major challenges of our time. In fact, the negative effects associated with both bacterial and fungal infections are enormous, especially considering that many microbial species are developing resistance to known antibiotics. In this work, we show how a combination of specific surface morphology and surface chemistry can create a surface that exhibits nearly 100% antimicrobial activity towards both Gram-negative and Gram-positive bacteria, and fungal cells. Arrays of vertically aligned, oxygen deficient zinc oxide (ZnO) nanowires grown on a substrate exhibit enhanced antimicrobial activity compared to surfaces containing either less defective nanowires, or highly oxygen-deficient flat films. This synergistic effect between physical activity (morphology) and chemical activity (surface composition) has been shown to be responsible for the outstanding antimicrobial activity of our surfaces, especially towards notoriously resilient bacterial or fungal species. These findings provide a series of design rules for tuning the activities of antibacterial and antifungal nanomaterials. These rules constitute an excellent platform for the development of next-generation antimicrobial surfaces.

Chemical syntheses of nanocrystals using colloidal techniques enable the production of a large variety of nanomaterials of a desired size, shape and composition. Therefore, these syntheses hold tremendous promise for the production of nanoparticles for next-generation technologies.However, they suffer from scalability issues, which can limit, or prevent, their translation into commercial technologies. Here we show the synthesis of zinc oxide nanocrystals with controlled size and doping using a continuous growth method, which is easily scalable. We demonstrate the tunable growth of pure ZnO nanocrystals from ~5 nm up to ~30 nm, and the synthesis of plasmonic ZnO nanocrystals by incorporating substitutional trivalent dopants such as aluminium, gallium and indium. We investigated the growth kinetics of these nanocrystals and used a variety of characterization techniques to fully elucidate the relationship between synthetic conditions and nanocrystal properties. We validate our reaction method by synthesizing Al-doped ZnO nanocrystals on a gram-scale, and with a reaction yield of 100%. These nanocrystals are used to deposit thin coating with excellent transparency and enhanced electrical conductivity compared to native ZnO. heating rate of 5 °C/min in air. Energy dispersive X-ray (EDX) spectra were acquired on a Nova 200 NanoSEM with a voltage of 15 kV. Scanning electron microscopy (SEM) images were acquired on a FEI Verios 460L SEM operated at 2 kV and 25 pA. ASSOCIATED CONTENT Supporting Information. Additional characterizations and data (Figure S1-S21 and Table S1-S2): UV-Vis-NIR, FTIR and PL spectra; XRD patterns; TEM and SEM images; size distribution histograms; crystallite size values; TGA scan; photo of the reaction setup; and additional tables. This material is available free of charge via the Internet at http://pubs.acs.org AUTHOR INFORMATION

Fluorine-doped tin oxide (FTO) is one of the most studied and established materials for transparent electrode applications. However, the syntheses for FTO nanocrystals are currently very limited, especially for stable and well-dispersed colloids. Here, we present the synthesis and detailed characterization of FTO nanocrystals using a colloidal heat-up reaction. High-quality SnO2 quantum dots are synthesized with a tuneable fluorine amount up to ~10% atomic, and their structural, morphological and optical properties are fully characterized. These colloids show composition-dependent optical properties, including the rise of a dopant-induced surface plasmon resonance in the near infrared.

OCA 20 Contact Angle System, utilizing a CCD camera to capture the images. Drops of ultrapure Milli-Q water were used. Each drop was recorded 10 times, and the average angle was computed.