Here we present a simple but general method for constructing complex binary colloidal crystals with an almost full range of size ratios, which is referred to as "template-assisted electric-field-induced assembly (TAEFIA)". The dependence of the structures of binary colloidal crystals on size ratio (gamma) and volume fraction (varphi) of the colloidal suspension was investigated. Binary colloidal crystals with gamma ranges from 0.10 to 0.91 were fabricated, and an attempt to fabricate a triple colloidal crystal via TAEFIA was presented. We suggest that TAEFIA is a versatile way to grow colloidal crystals with binary or more complex structures.
Energy transfer from fluorescein (Fl) to Rhodamine B (RhB) in the opal photonic crystals has been investigated by photoluminescence. The results show that the energy transfer can be enhanced effectively by photonic bandgaps. When the fluorescence emission wavelength of donor Fl overlaps the photonic bandgap the fluorescence intensity of the donor is suppressed, while the fluorescence intensity of acceptor RhB is obviously enhanced. This enhancement can be attributed to the inhibition of radiative emission of the donor in the photonic crystals.
Photoluminescence of Eu3+ doped TbPO4 (TbPO4:Eu) inverse opal photonic crystals was investigated. The results showed that the energy transfer from the donor Tb3+ to the acceptor Eu3+ can be enhanced effectively by the photonic band gaps in the photonic crystals. When the fluorescence emission wavelength of the donor Tb3+ overlapped the photonic band gap, the fluorescence intensity of the acceptor Eu3+ was obviously enhanced due to the inhibition of radiative emission of donor in the inverse opal photonic crystals.
We demonstrated a simple but general method to prepare large-area flexible nanocomposites with oriented gold nanorods (GNRs) embedded in polyvinyl alcohol (PVA) film by directly introducing a GNR colloidal solution into a PVA aqueous solution and using solid-state drawing techniques. The optical property of the nanocomposite exhibits a strong dependence on the angle between the polarization of the incident light and the drawing direction of the nanocomposite film. The color of the composite film can be intelligently tuned and displays red and blue when the light polarization is switched parallel to and perpendicular to the drawing direction, respectively. These composite films have promise for application in a single electrooptical device.
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