Journal of Luminescence 102–103 (2003) 476–480 Spectral study of colloidal photonic crystals K. Dou a ,Z.Xu b , X.J. Wang c, *,Y.Chen b , T. Collins a a Department of Physics and the Center for Laser and Photonics Research, Oklahoma State University, Stillwater, OK 74078, USA b Department of Chemistry, Oklahoma State University, Stillwater, OK 74078, USA c Department of Physics, Georgia Southern University, Statesboro, GA 30460, USA Abstract The spectroscopic and microscopic investigation in polystyrene photonic crystals was performed. Colloidal crystalline layers were deposited on glass and quartz by vertical evaporation deposition. Emission, excitation and up- convertedemissionwerestudiedonbothpolystyrenepowdersandpolystyrenephotoniccrystals.Theresultsindicated thatspectralfeatureswerestronglydependentontheparticlepropertiesofsize,shape,andarrangement.Blueemission at420nmwasalsofoundbyusinga532-nmexcitationduetomultiphotonprocessandadynamicmodelwasproposed to explain the mechanism of the up-converted emission. r 2002 Elsevier Science B.V. All rights reserved. PACS: 78.67.Bf; 42.70.Qs; 72.80.Le Keywords: Nanocrystals; Quantum-structured materials; Excited-state dynamics; Photonic crystal 1. Introduction There has been increasing interest in photonic crystals known as photonic band gap materials because they are composed of ordered structures with regular periodicity comparable to the wave- length of electromagnetic wave [1,2]. Possessing a spatial periodicity with length scales on the order of incident light wavelength, photonic crystals behave with respect to electromagnetic waves in a manner analogous to the behavior of atomic crystals with electrons. As an electronic band gap iscreatedbytheperiodicarrangementofatomsin a semiconductor, photonic crystals form a band gap in the crystals and the electromagnetic wave propagation is forbidden in this band gap. The band gap in these structures results from the modulation of the refractive index. Three-dimen- sional (3D) photonic crystals have facilitated the developments in the manipulation of light trans- mission in visible and infrared range and this will create new aspects for micro- to nanoscale device fabricationandintegrationwithspecialproperties. Significant applications of photonic crystals have been demonstrated in the fields of photon trap- ping,lightbeambending,lightemitting,andsoon [3–7]. Two classes of structures as photonic crystals madebychemicalmethodsaresyntheticopalsand inverse opals [8–11]. The former consists of monodisperse spherical particles with nano- to microscale diameters packed in a face centered cubic (FCC) arrangement, whereas the latter is formedbyfillingthevoidspacesofopaltemplates *Corresponding author. Tel.: +1-912-681-5503; fax: 1-912- 681-0471. E-mail address: xwang@gasou.edu (X.J. Wang). 0022-2313/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0022-2313(02)00582-3