Article pubs.acs.org/Langmuir
“Fastening” Porphyrin in Highly Cross-Linked Polyphosphazene Hybrid Nanoparticles: Powerful Red Fluorescent Probe for Detecting Mercury Ion Ying Hu,† Lingjie Meng,*,‡ and Qinghua Lu*,†,§ †
School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, Shanghai 200240, P. R. China MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and Department of Applied Chemistry, School of Science, Xi’an Jiaotong University, Xi’an 710049, P. R. China § State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, P. R. China ‡
S Supporting Information *
ABSTRACT: It is a significant issue to overcome the concentration-quenching effect of the small fluorescent probes and maintain the high fluorescent efficiency at high concentration for sensitive and selective fluorescent mark or detection. We developed a new strategy to “isolate” and “fasten” porphyrin moieties in a highly cross-linked poly(tetraphenylporphyrin-co-cyclotriphosphazene) (TPP−PZS) by the polycondensation of hexachlorocyclotriphosphazene (HCCP) and 5,10,15,20-tetrakis(4hydroxyphenyl)porphyrin (TPP-(OH)4) in a suitable solvent. The resulting TPP− PZS particles were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), 31P nuclear magnetic resonance (NMR), and ultraviolet and visible (UV−vis) absorption spectra. Remarkably, TPP−PZS particles obtained in acetone emitted a bright red fluorescence both in powder state and in solution because the aggregation of porphyrin moieties in “H-type” (face-to-face) and “J-type” (edge-to-edge) was effectively blocked. The fluorescent TPP−PZS particles also showed superior resistance to photobleaching, and had a high sensitivity and selectivity for the detection of Hg2+ ions. The TPP−PZS particles were therefore used as an ideal material for preparing test strips to quickly detect/monitor the Hg2+ ions in a facile way.
1. INTRODUCTION Fluorescent nanoparticles have attracted great interest over the past two decades in the fields of bioimaging and therapy,1−3 chemical sensors,4 heavy ion detection,5 display and lighting,6 and so on. Compared with the organic dyes, these nanoparticles provide competitive advantages in term of brighter emission, higher photobleaching resistance, and even capability for multiplexing. The frequently used fluorescent nanoparticles are semiconductor quantum dots (QDs),7 rare earth based nanoparticles,8 noble metal nanoparticles,9 carbon dots,10 and dyedoped silica or polymer nanoparticles.11,12 The QDs and rare earth based nanoparticles have relatively high quantum yield, narrow emission, and high resistance to photobleaching. However, they have several fundamental problems, such as poor chemical stability, susceptible emission to surface conditions, and potential cytotoxicity of their heavy metals ingredient.13 Noble metal nanoparticles and carbon dots present reduced cytotoxicity compared with QDs and rare earth, but their small size (
