Concentration and pH-modulated dual fluorescence in self-assembled nanoparticles of phototautomerizable biopolymeric amphiphile

A dual-emissive biopolymeric amphiphile (GC–HBO) has been prepared by densely conjugating hydrophilic glycol chitosan (GC) with a phototautomerizable hydrophobic dye (a derivative of 2-(2′-hydroxyphenyl)benzoxazole, HBO) showing excited-state intramolecular proton transfer (ESIPT). Ratiometric modul...

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Bibliographic Details
Published in:Dyes and pigments 2011-09, Vol.90 (3), p.284-289
Main Authors: Lim, Chang-Keun, Seo, Jangwon, Kim, Sehoon, Kwon, Ick Chan, Ahn, Cheol-Hee, Park, Soo Young
Format: Article
Language:English
Subjects:
Agglomeration
Biopolymeric conjugate
Chitosan
Derivatives
Dyes
Emission
Excited-state intramolecular proton transfer (ESIPT)
Fluorescent nanoparticle
Nanostructure
pH sensor
Ratiometric fluorescence sensor
Self assembly
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Summary:A dual-emissive biopolymeric amphiphile (GC–HBO) has been prepared by densely conjugating hydrophilic glycol chitosan (GC) with a phototautomerizable hydrophobic dye (a derivative of 2-(2′-hydroxyphenyl)benzoxazole, HBO) showing excited-state intramolecular proton transfer (ESIPT). Ratiometric modulation of phototautomeric (enol–keto) dual emission, governed by the chromophoric aggregation state, was studied with a low-molecular-weight model compound (GA–HBO) and was well correlated with the nanoparticle-forming behavior of GC–HBO via amphiphilic self-assembly in water. It has been found that the promoted chromophoric aggregation at higher concentration or at basic-to-neutral pH assists the nanostructure formation to generate predominant keto emission while the enol emission is intensified at lower concentration or with decreasing pH by disintegration of self-assembled structure. The assembly-related advantageous potential of GC–HBO for probing self-concentration and surrounding pH has been demonstrated with the ratiometric determination of critical particulation concentration (0.04 kg m −3) and near-physiological pH sensitivity (p K a ∼ 5.1). [Display omitted] ► Dual-emissive amphiphilic biopolymer self-assembles into nanoparticles. ► Phototautomerizable pendants generate the assembly-dependant dual emission. ► The dual emission modulation correlates to the concentration and pH condition. ► Ratiometric dual emission of the biopolymeric amphiphile probes the surrounding pH.
ISSN:0143-7208
1873-3743
DOI:10.1016/j.dyepig.2010.12.014