Enhanced photoluminescence properties of methylene blue dye encapsulated in nanosized hydroxyapatite/silica particles wi
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Enhanced photoluminescence properties of methylene blue dye encapsulated in nanosized hydroxyapatite/silica particles with core-shell structure Xiaolu Ge · Chengfeng Li · Chengyu Fan · Xiaoxing Feng · Bingqiang Cao
Received: 12 October 2012 / Accepted: 12 February 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract Organic dye of methylene blue (MB) was encapsulated in core-shell structured hydroxyapatite/silica particles (HAp/silica-MB) through a modified Stöber method with the addition of polyvinylpyrrolidone molecules. It was found that MB molecules were released from HAp/silicaMB at a slower rate than those from silica-MB in deionized water. In phosphate buffered saline (pH: 7.2–7.4) and acidic solutions (pH: 1.5–1.6), the penetration of ions in the interface influenced the interaction between HAp and MB molecules, which resulted in the rapid release of MB molecules from HAp/silica-MB. From the UV–Vis absorbance spectra, one could see that MB molecules in HAp/silica-MB were weakly aggregated in comparison with those in silica-MB. For HAp/silica-MB, enhanced luminescence properties were observed in the photoluminescence spectra and dual luminescence with two emission peaks were caused by the presence of monomers and dimers. Contrarily, no photoluminescence emission was detected for samples of free MB and silica-MB under the same excitation X. Ge () · C. Fan · X. Feng Key Laboratory of Atmospheric Composition and Optical Radiation, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, P.R. China e-mail: [email protected] Fax: +86-533-2781665 X. Ge School of Science, Shandong University of Technology, Zibo 255049, P.R. China C. Li School of Materials Science and Engineering, Shandong University of Technology, Zibo 255049, P.R. China B. Cao School of Materials Science and Engineering, University of Jinan, Jinan 250022, P.R. China
condition because of the self-quenching effect. It was the adsorption of MB molecules on HAp that had resulted in the enlargement of intramolecular distance and the reduction of self-quenching effect. These hybrid particles with enhanced luminescent properties might find wide applications in the field of bioanalysis, bioseparation, and biomedical imaging.
1 Introduction In comparison with other fluorophores, like quantum dots [1], lanthanide-doped oxides [2, 3], and metallic gold [4, 5], organic fluorescent dyes were used extensively and considerably in biomedical imaging, diagnostics, and therapy [6] due to their low cost, commercial availability, and ease of use. However, there were several considerable drawbacks for biological studies, such as poor photochemical stability, sensibility to buffer composition, and susceptibility to photobleaching. Recently, incorporation of small organic dyes into silica nanoparticles offered a great potential for isolating fluorescent dyes from the external environment because silica nanoparticles were chemically inert and the silica matrix porosity was not susceptible to swell or change with varying pH [7]. The e
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