Chemosensing in deep red: A squaraine-based fluorescent chemosensor for pH
摘要:
We have synthesized and spectrally characterized a squaraine-based fluorescent chemosensor for pH. This chemosensor unlike many others, works in 100 % aqueous solutions, signalling the pH change from 10 to 7 by a 11-fold increase in the emission intensity at 651 nm, when excited at the isosbestic point (614 nm). The average pK(a) for the ionizable groups is found to be 8.8. The chemosensor with its molar extinction coefficient > 200,000 and the quantum yield of 0.2, yield an impressive intrinsic brightness value of 40,000. (C) 1997 Elsevier Science Ltd.
Binding an analyte can cause a change in fluorescence emission of a sensor. The change in fluorescence can be related to the amount of analyte present. The sensor can include a semiconductor nanocrystal linked to a fluorescent moiety. Upon excitation, the fluorescent moiety can transfer energy to the semiconductor nanocrystal, or vice versa.
作者:Preston T. Snee、Rebecca C. Somers、Gautham Nair、John P. Zimmer、Moungi G. Bawendi、Daniel G. Nocera
DOI:10.1021/ja0618999
日期:2006.10.1
The development of a reversible chemical sensor based on a CdSe/ZnS nanocrystal (NC) is described. Signal transduction is accomplished by fluorescence resonance energy transfer (FRET) between the NC and a fluorescent pH-sensitive squaraine dye attached to the surface of the NC. The efficiency of FRET, and consequently the relative intensity of NC and dye emissions, is modulated with the pH-dependent absorption cross section of the squaraine dye. The design of a NC sensor based on FRET results in a ratiometric sensor since the emission intensities of dye and NC may be referenced to the isosbestic point between NC and dye emissions. The ratiometric approach allows sensing to be performed, regardless of issues surrounding collection efficiency (scattering environment, light fluctuations, etc.) and dye:NC loadings.