Removal of nano-particulates, viruses and other nano-scale contaminations from water is challenging for modern water treatments where most industrial water filtrations are for contaminants above 1 μm. Existing ultrafiltration membranes have been demonstrated to show sub-micron to nano-scale filtration capabilities. However, they have low water permeability, particularly at low temperatures, and need glycerin post-treatment to avoid the shrinkage of pores in industrial drying processes. Here we show a novel N-doped graphene enhanced hollow fibre polyvinylidene fluoride (PVDF) ultrafiltration membrane that demonstrates up to 100% increase in water flux compared with that of pure PVDF ultrafiltration membrane and it shows high stability and can filter water at close to 0 °C with up to 5 times increase in water flux, without the need for glycerin post-treatment. The addition of the N-doped graphene reduces the membrane average pore size from approximately 150 nm to about 100 nm and increases total volume of pores from 10% to 40%. The process mechanisms and characteristics of the membrane are described. Practical industrial application case studies are also presented. The main novelty of the research is the incorporation of a special N-doped graphene into PVDF ultrafiltration tubular nano-porous membranes for enhanced water treatment and the understanding of associated scientific mechanisms.

"The basic principle of the SMAL (Super-resolution Microsphere Amplifying Lens) imaging technology that we invented has its roots in the SMON (Submerged Microsphere Optical Nanoscope) pioneering work. SMAL is a novel objective lens whose front lens assembly contains a microsphere and is replaceable. We built a nanoscope prototype with nano XYZ scanning capability, which integrates a SMAL objective lens, allowing us to achieve super resolution imaging (70 nm – 90 nm). We have resolved large area scans (200 µm x 200 µm) by contactless sample scanning."

"We have demonstrated a novel, non-contacting super-resolution imaging setup using optical tweezers designed in-house. We resolve large area of samples using laser-trapped polystyrene microsphere scanning with resolution below the diffraction limit."

"We have demonstrated an objective lens attachment comprising a single microsphere lens for achieving super resolution virtual imaging. We have resolved large areas with resolutions below the diffraction limit through contactless sample scanning."

Because of the small sizes of most viruses (typically 5–150nm), standard optical microscopes, which have an optical diffraction limit of 200nm, are not generally suitable for their direct observation. Electron microscopes usually require specimens to be placed under vacuum conditions, thus making them unsuitable for imaging live biological specimens in liquid environments. Indirect optical imaging of viruses has been made possible by the use of fluorescence optical microscopy that relies on the stimulated emission of light from the fluorescing specimens when they are excited with light of a specific wavelength, a process known as labeling or self-fluorescent emissions from certain organic materials. In this paper, we describe direct white-light optical imaging of 75-nm adenoviruses by submerged microsphere optical nanoscopy (SMON) without the use of fluorescent labeling or staining. The mechanism involved in the imaging is presented. Theoretical calculations of the imaging planes and the magnification factors have been verified by experimental results, with good agreement between theory and experiment."

The imaging resolution of a conventional optical microscope is limited by diffraction to ∼200 nm in the visible spectrum. Efforts to overcome such limits have stimulated the development of optical nanoscopes using metamaterial superlenses, nanoscale solid immersion lenses and molecular fluorescence microscopy. "These techniques either require an illuminating laser beam to resolve to 70 nm in the visible spectrum or have limited imaging resolution above 100 nm for a white-light source. Here we report a new 50-nm-resolution nanoscope that uses optically transparent microspheres (for example, SiO2, with 2 μm<diameter<9 μm) as far-field superlenses (FSL) to overcome the white-light diffraction limit. The microsphere nanoscope operates in both transmission and reflection modes, and generates magnified virtual images with a magnification up to ×8. It may provide new opportunities to image viruses and biomolecules in real time."