Slow photons in the fast lane in chemistry

Assembly of large-area, highly ordered, crack-free inverse opal films

“…This scalable route to highly ordered, large-area, chemically tailorable inverse opal films may be utilized in a diverse range of applications. Due to the absence of an overlayer, the high porosity of the coassembled films is readily accessible from the top surface, which is especially important for applications in catalysis (10,15,16), gas adsorption (55), or tissue engineering (11,12). These single-domain periodic inverse opal films can also behave as large-area photonic band gap structures for applications in photonics (6-10).…”

“…Inverse opals can exhibit a high degree of interconnected porosity (approximately 75%) with extremely uniform size (average size normally in the range of 100-1000 nm) and periodic distributions of pores, achieved through colloidal monodispersity. Such structures have been shown to be potentially useful in a wide range of fields, including photonics (6-10), tissue engineering (11,12), sensing (13,14), and catalysis (10,15,16). However, whereas conventional self-assembly has yielded ordered inverse opal structures over modest (≤10 μm) length scales, such processes have been plagued by uncontrolled formation of defects over larger length scales (2,3), thus limiting their real-world applications.…”

Bottom-up assembly of photonic crystals

“…Several firsts have been demonstrated in this system: The first complete photonic band gap at the optical telecommunication wavelength of 1.5 mm, 52 the first demonstration of enhanced and suppressed spontaneous emission, 4 the first non-linear optical experiments like all optical switching in transmittance for opals 5 and inverse opals 6 and the enhancement of third harmonic 7 and second harmonic generation. 8 Without the need for a complete gap, several other ideas have been first implemented with colloidal photonic crystals: Graded structures for enhanced coupling efficiency, 9 binary colloidal crystal architectures, 10 porous Bragg mirrors for sensing applications, 67,69 slow photon enhanced photochemistry and photocatalysis, 11 dynamic full colour displays, enhanced light harvesting for solar-cells, 74 solid-state dye and polymer lasers, 75 increased efficiency for lithium ion battery applications 12,13 as well as applications as a dual stationary phase and detector in high-pressure liquid chromatography. 14 In this tutorial review we will start with the underlying physical concepts behind the success of the bottom-up assembled 3D colloidal photonic crystal, how the knowhow was adapted to 2D photonic crystal architectures, expanded and enriched to include 1D photonic crystal lattices, which will be followed by a discussion of the materials and fabrication issues of these different dimensionality structures and concluded by an outlook to current and future applications.…”

Advanced Materials for Sustainable Energy and a Greener Environment

“…At the frequency edges of stop bands, photons propagate with substantially reduced group velocity leading to the appearance of slow photons. [6][7][8][9][10] The effect of the pore size of an inverse TiO 2 opal in relation to photocatalytic activity has been studied since the stop band position depends on the macroporous size.…”