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.

Fluorescence from graphene oxide and the influence of ionic, π–π interactions and heterointerfaces: electron or energy transfer dynamics

“…37,77 On the other hand emission at specific wavelengths, for example, 440 nm, 15 505 nm 31 and the blue-UV region, 15,36,39 was observed. The emission wavelengths of GO depend on the functional groups, 45 pH 69,[78][79][80][81][82] and its combination with other materials such as PANI-nanorods, 83 MB, 84 tetra-amino porphyrin, 85 PEG 25,26 etc.…”

Emerging flexible and wearable physical sensing platforms for healthcare and biomedical applications

“…The tunability of the physical properties of these nanomaterials is one of the promising features for their implementation as versatile sensing platforms 72,73 . Indeed, graphene-based physical sensors have been demonstrated in many applications in recent years, including the detection and monitoring of humidity 74 , pH 75 , chemicals 76,77 , biomolecules 73,[78][79][80] , and mechanical forces [81][82][83] . Moreover, the biocompatibility of graphene opens up further possibilities for its use as a fundamental element of implantable biophysical sensors.…”

Upconversion Nanoparticle-Based Nanocomposites

“…NGO-PEG was obtained by covalently grafting amino carboxylic PEG onto NGO sheet, and the left carboxylic groups at the PEG terminals were available for fluorescent probes. Yan et al [187] also fabricated the biocompatible and flexible GO/UCNPs hybrid film for optical pH sensing. The nanocomposites films is prepared by mixing GO with polyethylenimine (PEI)-functionalized upconversion nanoparticles and then vacuum filtrating the resulting hybrid dispersion.…”