All-optical nanoscale pH meter

Sandra W Bishnoi, Christopher J Rozell, Carly S Levin, Muhammed K Gheith, Bruce R Johnson, Don H Johnson, Naomi J. Halas

Research output: Contribution to journalArticlepeer-review

312 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1687-92
Number of pages6
JournalNano Letters
Issue number8
StatePublished - Aug 2006


  • Equipment Design
  • Equipment Failure Analysis
  • Hydrogen-Ion Concentration
  • Nanotechnology
  • Optics and Photonics
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Spectrum Analysis, Raman
  • Surface Properties
  • Transducers
  • Evaluation Studies
  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.


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