Improved γ-Aminobutyric Acid Sensing Activity Based On Graphene Oxide Interface On An Optical Microfiber Interferometry

In recent years,more and more attentions have been paid to development of nano material-functionalized optical fiber.It is a challenge to improve the sensing activity of optical fiber sensors.As a two-dimensional material with single-layer carbon atoms,graphene has attracted great interest due to its excellent electronic,thermal,and mechanical properties.Graphene Oxide(GO),as its important derivatives,possesses both sp2,and sp3 hybridized carbon atoms as well as different functional groups such as epoxy,carboxyl,hydroxyl,and so on.It provides a promising platform for the biomolecule immobilization through the π-stacking interaction or covalent conjugation.With miniature size and mechanical flexibility,optical microfiber has become an excellent candidate for sensing.It can be conveniently integrated with current medical tools for sensing in inaccessible locations.What is more,its micro-scale diameter endows it with high refractive index(RI)sensitivity basing on the evanescent wave mechanism.In this thesis,a GO interface has been constructed between silica optical microfiber and bio-recognition elements to develop an improved γ-aminobutyric acid(GABA)sensing approach.The GO interface improved the sensing activity by providing a larger paltform for more bio-recognition elements immobilization,and amplifying surface refractive index change caused by combination between bio-recognition elements and target molecules.The thesis mainly includes the following three aspects:1 An abruptly tapered silica microfiber with waist diameter of 4.25 um has been fabricated.GO nanosheets have been carboxylated and constructed on the microfiber surface as an interface between microfiber and bio-recognition elements.2 The sensor with GO interface has been employed in the γ-aminobutyric(GABA)detection.In the GABA solutions with concentrations from 10-18 M to 10-6 M,the sensor showed regular red-shift in transmission wavelength.The sensitivity of the as-prepared sensor with GO interface reached to 1.03 nm/log M,which is 3 times of the sensor without GO interface(0.37 nm/log M).And its LOD was estimated to be 2.91×10-18 M,obtaining 7 orders of magnitude higher than that without GO interface(8.11×10-11 M).Furthermore,the interface improvement mechanism has been investigated.3 The selectivity of as-prepared sensor to GABA in the presence of other potential interferents,and the sensing performance in real serum samples have been studied.