Hierarchically structured photonic crystals for integrated chemical separation and colorimetric detectionElectronic supplementary information (ESI) available: Characterization of a photonic crystal film and three kinds of SiO2 particles for fabrication of TLC plates, differential migration of 4-NP, 2-NBA and 4-t-BP and t-BSA, DA and DT, separation of 4-NP and 4-t-BP, distribution of the crack width in three PC plates, reversed phase TLC for separation of nonpolar molecules. See DOI: 10.1039/c6nr

A SiO 2 colloidal photonic crystal film with a hierarchical porous structure is fabricated to demonstrate an integrated separation and colorimetric detection of chemical species for the first time. This new photonic crystal based thin layer chromatography process requires no dyeing, developing and UV irradiation compared to the traditional TLC. The assembling of mesoporous SiO 2 particles via a supersaturation-induced-precipitation process forms uniform and hierarchical photonic crystals with micron-scale cracks and mesopores, which accelerate the diffusion of developers and intensify the adsorption/desorption between the analytes and silica for efficient separation. Meanwhile, the chemical substances infiltrated to the voids of photonic crystals cause an increase of the refractive index and a large contrast of structural colors towards the unloaded part, so that the sample spots can be directly recognized with the naked eye before and after separation. Hierarchically structured SiO 2 colloidal photonic crystals are prepared for integrated separation and colorimetric detection of chemical species via a new thin layer chromatography technique. It is the first time for a photonic crystal based separation technique to realize efficient separation and colorimetric detection at the same time.