title: Biocompatible and flexible graphene oxide/upconversion nanoparticle hybrid film for optical pH sensing.
abstract: 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.
authors.affiliation: CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China. zjgu@ihep.ac.c linazhao@ihep.ac.cn zhaoyuliang@ihep.ac.cn.
authors.forename: Liang
authors.initials: L
authors.lastname: Yan
authors.forename: Ya-Nan
authors.initials: YN
authors.lastname: Chang
authors.forename: Wenyan
authors.initials: W
authors.lastname: Yin
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Liu
authors.forename: Debao
authors.initials: D
authors.lastname: Xiao
authors.forename: Gengmei
authors.initials: G
authors.lastname: Xing
authors.forename: Lina
authors.initials: L
authors.lastname: Zhao
authors.forename: Zhanjun
authors.initials: Z
authors.lastname: Gu
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D053758:Nanoparticles / Q000737:chemistry*; D055620:Optical Phenomena; D010087:Oxides / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D010087:Oxides; D006108:Graphite