Photonic crystals (PhCs) influence the propagation of light by their periodic variation in dielectric contrast or refractive index. This review outlines the attractive optical qualities inherent to most PhCs namely the presence of full or partial photonic band gaps and the possibilities they present towards the inhibition of spontaneous emission and the localization of light. Colloidal self-assembly of polymer or silica spheres is one of the most favoured and low cost methods for the formation of PhCs as artificial opals. The state of the art in growth methods currently used for colloidal self-assembly are discussed and the use of these structures for the formation of inverse opal architectures is then presented. Inverse opal structures with their porous and interconnected architecture span several technological arenasoptics and optoelectronics, energy storage, communications, sensor and biological applications. This review presents several of these applications and an accessible overview of the physics of photonic crystal optics that may be useful for opal and inverse opal researchers in general, with a particular emphasis on the recent use of these three-dimensional porous structures in electrochemical energy storage technology. Progress towards all-optical integrated circuits may lie with the concepts of the photonic crystal, but the unique optical and structural properties of these materials and the convergence of PhC and energy storage disciplines may facilitate further developments and non-destructive optical analysis capabilities for (electro)chemical processes that occur within a wide variety of materials in energy storage research.

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High performance thin film lithium batteries using structurally stable electrodeposited V2O5 inverse opal (IO) networks as cathodes provide high capacity and outstanding cycling capability and also were demonstrated on transparent conducting oxide current collectors. The superior electrochemical performance of the inverse opal structures was evaluated through galvanostatic and potentiodynamic cycling, and the IO thin film battery offers increased capacity retention compared to micron-scale bulk particles from improved mechanical stability and electrical contact to stainless steel or transparent conducting current collectors from bottom-up electrodeposition growth. Li(+) is inserted into planar and IO structures at different potentials, and correlated to a preferential exposure of insertion sites of the IO network to the electrolyte. Additionally, potentiodynamic testing quantified the portion of the capacity stored as surface bound capacitive charge. Raman scattering and XRD characterization showed how the IO allows swelling into the pore volume rather than away from the current collector. V2O5 IO coin cells offer high initial capacities, but capacity fading can occur with limited electrolyte. Finally, we demonstrate that a V2O5 IO thin film battery prepared on a transparent conducting current collector with excess electrolyte exhibits high capacities (∼200 mAh g(-1)) and outstanding capacity retention and rate capability.

Surfactant induced ordering of 2D and 3D colloidal crystal photonic crystals is possible on metallic substrates by dip‐coating at fast rates (≈1 mm/min). Ordered monolayer opals on conductive gold‐coated silicon substrates behave as a 2D diffraction grating. The method allows high throughput, ordered colloidal crystal formation useful as nanomaterials templates for energy storage or functional materials.

Three-dimensional vanadium pentoxide (V 2 O 5 ) material architectures in the form of inverse opals (IOs) were fabricated using a simple electrodeposition process into artificial opal templates on stainless steel foil using an aqueous solution of VOSO 4 .χH 2 O with added ethanol. The direct deposition of V 2 O 5 IOs was compared with V 2 O 5 planar electrodeposition and confirms a similar progressive nucleation and growth mechanism. An in-depth examination of the chemical and morphological nature of the IO material was performed using X-ray crystallography, X-ray photoelectron spectroscopy, Raman scattering and scanning/transmission electron microscopy. Electrodeposition is demonstrated to be a function of the interstitial void fraction of the artificial opal and ionic diffusivity that leads to high quality, phase pure V 2 O 5 inverse opals is not adversely affected by diffusion pathway tortuosity. Methods to alleviate electrodeposited overlayer formation on the artificial opal templates for the fabrication of the porous 3D structures are also demonstrated. Such a 3D material is ideally suited as a cathode for lithium ion batteries, electrochromic devices, sensors and for applications requiring high surface area electrochemically active metal oxides. The growth in portable electronics and the need for cleaner energy solutions has led to the rising interest in materials research and energy storage material architectures that may help drive advancement in energy storage technologies to mitigate current issues in some energy storage materials and batteries such as capacity fading and lower life times, for example. [1][2][3][4] In recent years, three-dimensional (3D) material architectures 5 have become a particularly attractive approach to achieving significant improvements in charge rate performance, maintenance of specific capacity and opportunities for higher power density supercapacitors. [6][7][8][9] For this reason, the development of synthesis routes for the fabrication of three-dimensional nanostructured active materials onto metallic current collector substrates is important. [10][11][12][13] Electrodeposition is a particularly facile route for the formation of metal and metal oxide films on a variety of conductive substrates and has recently gained a lot of attention for synthesising three-dimensional materials when combined with templates and sacrificial architecture-directing structures. [14][15][16][17] Vanadium pentoxide is a particularly attractive replacement cathode material with its mixed valence, V 4+ and V 5+ , making it an ideal candidate for a large number of redox-dependent applications. 23-26 While the lattice structure is theoretically maintained upon mild intercalation, phase changes are known to occur and the interlayer van der Waals spacing characteristic of its layered orthorhombic crystal structure can become deformed at lower voltages (higher Li mole fraction). 27,28 Large particle sizes can also limit the solid state diffusional rate of cation insertion. The growth of a porous, thre...