In this article, we report a facile electrochemical method to modify anatase TiO 2 by cathodically biasing TiO 2 in an ethylene glycol electrolyte. The resulting black TiO 2 is highly stable with a significantly narrower bandgap and higher electrical conductivity. Furthermore, largely improved photoconversion efficiency (increased from 48% to 72% in the visible region, and from nearly 0% to 7% in the UV region), photocatalytic efficiency, and charge-storage capability ($42 fold increase) are achieved for the treated TiO 2 .

A stable, label-free optical biosensor based on a porous silicon-carbon (pSi-C) composite is demonstrated. The material is prepared by electrochemical anodization of crystalline Si in an HF-containing electrolyte to generate a porous Si template, followed by infiltration of poly(furfuryl) alcohol (PFA) and subsequent carbonization to generate the pSi-C composite as an optically smooth thin film. The pSi-C sensor is significantly more stable toward aqueous buffer solutions (pH 7.4 or 12) compared to thermally oxidized (in air, 800 °C), hydrosilylated (with undecylenic acid), or hydrocarbonized (with acetylene, 700 °C) porous Si samples prepared and tested under similar conditions. Aqueous stability of the pSi-C sensor is comparable to related optical biosensors based on porous TiO(2) or porous Al(2)O(3). Label-free optical interferometric biosensing with the pSi-C composite is demonstrated by detection of rabbit IgG on a protein-A-modified chip and confirmed with control experiments using chicken IgG (which shows no affinity for protein A). The pSi-C sensor binds significantly more of the protein A capture probe than porous TiO(2) or porous Al(2)O(3), and the sensitivity of the protein-A-modified pSi-C sensor to rabbit IgG is found to be ~2× greater than label-free optical biosensors constructed from these other two materials.

Self-organized TiO 2 nanomaterials grown by anodic oxidation of Ti foils have attracted broad scientific interest due to their wide potential applications. The majority of anodic TiO 2 nanostructures studied to date are in the form of self-ordered nanotube arrays. Here we report an exotic type of multilayered nanoporous TiO 2 films that are conveniently fabricated by anodizing Ti foils of high imperfection levels using a novel multipulse anodization method. The fabricated TiO 2 films feature tens of welldefined layers whose long-range structural periodicity leads to photonic band gaps in the visible wavelengths and vivid film colors. Moreover, the optical responses (or the film color) of the fabricated TiO 2 multilayers not only are sensitive to environmental chemicals but also can be electrically switched on and off repeatedly, demonstrating their novel potential applications for, e.g., colored smart windows or electric display boards.

A facile electrochemical method to selectively remove the outer walls of anodic TiO2 nanotubes by leaving the as‐anodized nanotubes in the same electrolyte and applying an electric field parallel to the anodic film for several minutes is reported. The better‐separated single‐walled TiO2 nanotubes thus obtained show significantly improved photocatalytic efficiency compared with their non‐etched counterparts.

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Plasmonic materials offer the remarkable ability to manipulate light by metal–dielectric features significantly smaller than the wavelengths of free space photons. The fabrication of such minuscule features for the desired plasmonic properties, however, remains challenging. Here, we report an economical and versatile bottom-up approach that combines electrodeposition and de- alloying techniques for fabricating elaborate metal-based structures, achieving structural resolutions comparable to the present lithography techniques. We present our studies on the metal-based counterpart of the rugate filter. These metal-based photonic films are porous, magnetic, and feature strong optical responses in visible wavelengths, while their structural periodicities are an order of magnitude smaller than the light’s free space wavelength.

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