Photonic Crystals from Ordered Mesoporous Thin‐Film Functional Building Blocks

Abstract

Environment‐sensitive Bragg reflectors are built using functional mesoporous thin films as building blocks. Tuning of optical properties is achieved by changing the composition or porosity of the slabs or the introduction of planar defects. Sorption or capillary condensation of molecules into the pore system results in a 10–40 nm photonic bandgap (PBG) shift. Organic functions added to the pore surface change the response, permitting tailoring of the selectivity towards small‐size molecules.

Tunable Mesoporous Bragg Reflectors Based on Block Copolymer Self-Assembly

“…The adsorption and desorption of gas phase molecules in the pores leads to reversible changes in the refractive index and thereby in the photonic properties of the stack. [4][5][6][7] Bonifacio et al introduced the concept of a MDBR-based "photonic nose". 8 Other applications include the use of MDBRs as environmentally responsive resonance cavities 10,11 and their coupling to mesoporous surface layers.…”

“…4 While the MDBRs exhibited an interconnected pore network, the stack fabrication was extremely time consuming with fabrication times of 4 days or more for each consecutive layer. 4,5 A less complex alternative is the sequential deposition of nanoparticle-based solutions to form mesoporous films. The group of Cohen introduced this concept for a homopolymer mediated nanoparticle approach following numerous dip-coating cycles.…”

“…This range is well above previously reported approaches to tune the refractive index by porosity for MDBR manufacture. 5,18 To visualize an entire MDBR stack, thin cross-sectional slices were prepared by focussed ion-beam milling. The two different MDBR layers are clearly discernible in the transmission electron microscopy (TEM) image of Fig.…”

Tunable structural color in organisms and photonic materials for design of bioinspired materials

“…Inorganic porous films using this principle can be used in a color-tunable sensor. Their mesoporous SiO 2 and TiO 2 multilayers can be fabricated by depositing precursor solutions by spin coating [41], dip coating [42] and layer-by-layer assembly [43].…”

Photon Management in Dye Sensitized Solar Cells

“…This might have a deleterious effect on charge transport and recombination through the cell. Very recently, new types of one-dimensional photonic crystals (1DPC) have been prepared by alternate deposition of either mesoporous (Choi et al, 2006); (Fuertes et al, 2007) or nanoparticles (Wu et al, 2007); (Colodrero et al, 2008) based films. These structures Mihi & Míguez, 2005) are usually easier to build and integrate than those abovementioned of higher dimensionality and present attractive features, such as very intense and wide Bragg reflections and reduced thickness (less than a micron versus the several micron thickness of opals).…”