NOVELTY - Forming a nanostructure membrane, comprises: (a) placing a substrate comprising titanium (235) in electrolyte bath containing water, fluoride compound, complexing agent and polar organic solvent; (b) anodizing the substrate to form titanium dioxide nanotubes array on the substrate; and (c) allowing the titanium dioxide nanotubes array to stand, or applying heat to titanium dioxide nanotubes array until the nanotubes array separates from substrate to create nanostructure membrane.    USE - The method is useful for forming a nanostructure membrane, which is useful in: forming solar cell (claimed), photovoltaic devices e.g. dye-sensitized solar cells; photocleavage of water; photocatalytic dye degradation; air purification; water purification and catalysts; and as sensors.    ADVANTAGE - The method: provides transparent and crack free titanium dioxide membranes (containing highly ordered hexagonal titanium dioxide nanotubes), which gives better photovoltaic properties in solar cells (2.7% efficiency); allows the formation of titanium dioxide nanotubes array at a rate of greater than 40 mu m/hour; is rapid and provides nanotube membranes with lower toxicity, thus it is environmentally friendly; and provides nanotubes having opened both ends that improves the utility of the nanotubes, thus improving the performance of photovoltaic systems, flow-through and filtration processes.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) forming a solar cell, comprising steps (a)-(c) as above per se, and (d) attaching the nanostructure membrane to a transparent substrate to form the photosensitive electrode (215); and    (2) the solar cell formed by the above method.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of dye-sensitive solar cell comprising titanium dioxide nanotubes with a barrier layer.    Counter electrode (205)    Photosensitive electrode (215)    Dye-sensitive titanium dioxide nanotubes (230)    Titanium substrate (235)    Barrier layer (240)