Biocompatible and flexible graphene oxide/upconversion nanoparticle hybrid film for optical pH sensing

Liang Yan, Ya Nan Chang, Wenyan Yin, Xiaodong Liu, Debao Xiao, Gengmei Xing, Lina Zhao, Zhanjun Gu, Yuliang Zhao

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Free-standing optical hybrid film which is composed of positively-charged polyethylenimine-coated NaYF4:Yb,Er nanoparticles and negatively-charged graphene oxide (GO) has been developed to measure pH based on the pH-dependent luminescence quenching effect caused by GO. The isothermal titration calorimetry analyses indicate that the interaction between GO and NaYF4:Yb,Er nanoparticles becomes stronger with increasing pH, leading to a more significant fluorescence quenching of NaYF4:Yb,Er nanoparticles at high pH values. The excellent mechanical properties of the hybrid film endow the thin-film pH sensor with better repeatability and higher stability during the measurements. Quantitatively, the upconversion luminescence intensity of the hybrid film exhibits a linear trend over the pH range of 5.00-8.00. Because of excitation with a 980 nm laser, as expected, the hybrid film sensor is also sensitive to the urine measurements with reduced background absorption. In addition to its good biocompatibility, our free-standing hybrid film sensor would be a promising candidate for biological, medical, and pharmaceutical applications.

Original languageEnglish (US)
Pages (from-to)1576-1582
Number of pages7
JournalPhysical Chemistry Chemical Physics
Issue number4
StatePublished - Jan 28 2014

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry


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