Abstract. Poly(methyl methacrylate) (PMMA) microbeads are hybridized with fluorescent YVO 4 :Bi 3+ ,Eu 3+ nanoparticles using the layer-by-layer adsorption technique. The composite beads A are prepared by adsorbing negatively-charged YVO 4 :Bi 3+ ,Eu 3+ nanoparticles onto positively-charged PMMA beads modified with poly(allylamine hydrochloride) (PAH). The composite beads B are prepared by adsorbing nanoparticles onto PMMA beads with multiple alternate layers of PAH and poly(sodium 4-styrenesulfonate) (PSS), i.e., with (PAH/PSS) 4 /PAH layers. The composite beads C are prepared by adsorbing 300 °C heated nanoparticles with negative charge onto PMMA beads with single PAH layer. These three kinds of composite beads are compared in terms of the amount of adsorbed nanoparticles and the fluorescent intensity. IntroductionFluorescence-labeled beads have played significant roles in cellular imaging, biodetection, and biosensing in the fields of biology and medicine. In these fields, organic dyes are widely used as fluorescent materials. Dye molecules are incorporated in a matrix such as polymer [1] and silica [2]. However, organic dyes are subject to photobleaching because of a reaction with surrounding oxygen and a photochemical decomposition under the irradiation of excitation light. This cannot allow us to do long-term preservation and observation. Therefore, attention has been paid to fluorescent inorganic nanosized materials. Fluorescent quantum dots with polymerisable ligands were incorporated into polystyrene beads [3]. In this work, we focus on YVO 4 :Bi 3+ ,Eu 3+ nanoparticles showing red emission under near-UV excitation [4].The layer-by-layer (LbL) adsorption technique is one of the attractive preparation methods of composites. In this technique, two different types of materials with opposite charges can be easily combined through electrostatic interaction for a short reaction time [5]. The LbL technique has been applied to the formation of composite beads hybridized with fluorescent nanoparticles such as quantum dots [6]