title: All-optical nanoscale pH meter.
abstract: We show that an Au nanoshell with a pH-sensitive molecular adsorbate functions as a standalone, all-optical nanoscale pH meter that monitors its local environment through the pH-dependent surface-enhanced Raman scattering (SERS) spectra of the adsorbate molecules. Moreover, we also show how the performance of such a functional nanodevice can be assessed quantitatively. The complex spectral output is reduced to a simple device characteristic by application of a locally linear manifold approximation algorithm. The average accuracy of the nano-"meter" was found to be +/-0.10 pH units across its operating range.
authors.affiliation: Department of Electrical and Computer Engineering, Laboratory for Nanophotonics, Rice University, P O Box 1892, Houston, Texas 77251-1892, USA.
authors.forename: Sandra W
authors.initials: SW
authors.lastname: Bishnoi
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Rozell
authors.forename: Carly S
authors.initials: CS
authors.lastname: Levin
authors.forename: Muhammed K
authors.initials: MK
authors.lastname: Gheith
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Johnson
authors.forename: Don H
authors.initials: DH
authors.lastname: Johnson
authors.forename: Naomi J
authors.initials: NJ
authors.lastname: Halas
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D006863:Hydrogen-Ion Concentration; D036103:Nanotechnology / Q000295:instrumentation* / Q000379:methods; D055095:Optics and Photonics / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013059:Spectrum Analysis, Raman / Q000295:instrumentation* / Q000379:methods; D013499:Surface Properties; D014159:Transducers