Preparation And Performance Of PH Sensors Based On Photonic Nanochain Arrays

Due to the features such as visualization,ease of miniaturization and integration,responsive photonic crystals?RPCs?are considered to be ideal candidates for sensor.However,the film-shape and spherical photonic crystal?PC?sensors always face large challenges in rapid test,especially in micro-area and trace analysis,thus limit their practical applications.To solve these problems,here we designed and prepared a planar array pH sensor by template polymerization to“grow”Fe₃O₄@PAA photonic nanochains on the hydrophilic modified glass substrate.The excellent responsive properties ascribe to the fixation and low dimension of photonic nanochains.The research contents involve the construct mechanism,structural control methods and sensing performances of the pH sensor.The detail results of the dissertation are as following:?1?Fe₃O₄@PAA nanochain arrays was prepared by combining magnetically induced self-assembly and in-situ template polymerization.The as-obtained nanochain arrays could align and rotate in play along with external magnetic field owing to the immobilization of nanochains on the surface of glass substrate.The study on the construct mechanism found that AA was absorbed on the surface of magnetically induced chain-like structures and the glass substrate.It is because that the formation of hydrogen bond between AA monomer and PVP shell,as well as the silicon hydroxyl on the surface of the hydrophilic modified glass substrate.As a result,one end of the nanochains was tethered on the surface of the substrate by generated PAA.The grafting density increased with the increase of the nanoparticle concentration in precursor solution,and the nanochains become longer when extending the induced time of external magnetic field during the preparation process.Whatever,adjusting the magnetic field strength and the ratio of glycol to water in the reaction system,the interparticle spacing and shell thickness of nanochains can be effectively controlled respectively.?2?We focused on the study of optical property and pH sensing performance of Fe₃O₄@PAA nanochain arrays.Dark-field optical micrographs demonstrated that the as-obtained nanochains were photonic nanochains and showed beautiful color under a vertical magnetic field.The pixel in dark-field mode increased with the increase of the grafting density,thus leading to a stronger reflection intensity per unit area.The interparticle spacing of PC nanochains determined the initial structural color and diffraction peak of the PC nanochain arrays.In this dissertation,the initial structural color can be adjusted from blue to yellow,and initial diffraction peak varied from 480nm to 580 nm correspondingly.The studies on pH sensing performance of the PC nanochain arrays revealed that when changing pH value from 5 to 10,the color of PC nanochains changed from blue to red and the reflection spectrum shifted from 465 nm to 630 nm.It only takes about 0.75 s for PC nanochin arrays to complete the pH sensing and only 5.2×10^-1313 mol OH^-is consumed for micro-area??=20?m?detection.Besides,the PC nanochain arrays could resist solution disturbances.All above results indicate that PC nanochain arrays is suitable for real-time,in-situ and trace analysis of the pH value of microenvironment.