title: A ratiometric CdSe/ZnS nanocrystal pH sensor.
abstract: 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.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4306, USA.
authors.forename: Preston T
authors.initials: PT
authors.lastname: Snee
authors.forename: Rebecca C
authors.initials: RC
authors.lastname: Somers
authors.forename: Gautham
authors.initials: G
authors.lastname: Nair
authors.forename: John P
authors.initials: JP
authors.lastname: Zimmer
authors.forename: Moungi G
authors.initials: MG
authors.lastname: Bawendi
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Nocera
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D019187:Cadmium Compounds / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry; D003460:Crystallization; D003503:Cyclobutanes / Q000737:chemistry; D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D053758:Nanoparticles / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry; D010636:Phenols / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry*; D012995:Solubility; D013057:Spectrum Analysis; D013440:Sulfides / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D004396:Coloring Agents; D003503:Cyclobutanes; D008024:Ligands; D010087:Oxides; D010636:Phenols; D010720:Phosphines; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; C480596:squaraine; D014867:Water; C058667:cadmium selenide; C044646:phosphine; C031238:zinc sulfide