Monitoring Microenvironments With Nano-sized pH Meter

Each nano-shell contained a tiny core of non-conducting silica. The minute particles were then coated with pH-sensitive molecules of paramercaptobenzoic acid (pMBA).

When the nano-shells were placed in solutions of varying acidity, the pH of the environment could be monitored by measuring the surface-enhanced Raman scattering (SERS) spectra of the pMBA coating. The complex spectral output was 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. These details were published in the June 28, 2006, issue of Nano Letters.

"Almost every biologist I speak with comes up with one or two things they would like to measure with this,” said senior author Dr. Naomi Halas, professor of chemistry at Rice University.



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