Fabrication And Application Of Photonic Crystal-based Metal Ions Sensing Films

Metal ions are ubiquitous in daily life and can penetrate into human body through the skin or ingestion by mistake.Excessive deposition will cause various diseases and even threaten our life.At present,the traditional detection methods,such as chromatography,spectroscopy and electrochemical methods,are limited in practical application due to the need for special equipments or complex sample preparation.In recent years,photonic crystal?PC?materials have been widely concerned in the fields of chemical and biological sensing due to their special optical properties.The tunability of photonic stopband and fluorescence enhancement derived from slow photon effect provide a good strategy for effective and simple detection of metal ions.In this dissertation,we first combined the photonic stopband tunability of PC with the volume phase transition of poly?acrylic acid-acrylamide?hydrogel.The volume of the hydrogel can be changed by the specific interaction of chemically modified functional molecules with metal ions,which leads to the change of PC microspheres spacing.Correspondingly,the photonic stopband shifts and the color of hydrogel changes,achieving a PC hydrogel film with high selectivity,sensitivity and visual detection of metal ions.Secondly,a PC fluorescence film for highly sensitive,selective,reversible and rapid detection of metal ion was fabricated by combining fluorescence enhancement derived from slow photon effect with the interconnected three-dimensional macropore structure of inverse opal PC?IOPC?.The IOPC was infiltrated by small organic molecules which show the specific complexation to the target metal ions.The details are as follows:1.An opal polystyrene-poly?acrylic acid-acrylamide?three-dimensional PC hydrogel film was fabricated by vertical deposition and sandwich method,followed by modification of dopamine to obtain a PC hydrogel sensing film,DOPA?Hyl-PC?,for visual and effective detection of Fe³⁺ions.The as-prepared hydrogel swelled because the amount of functional groups including amino and carboxyl groups changed,resulted from the complex reaction between dopamine and Fe³⁺ions.The stopband of PC in the hydrogel made a red-shift and the color of the hydrogel changed from green to red,realizing the visual detection of Fe³⁺ions.The hydrogel sensing film fabricated from 15 mM of dopamine responded in 10 min and the maximum of stopband shift was 117 nm.The limit of detection?LOD?was 0.57 nM.Furthermore,the fabricated photonic crystal hydrogel sensing film has good selectivity for Fe³⁺,which lays a theoretical foundation for detecting Fe³⁺in real life.2.Three-dimensional macroporous SiO₂ Inverse opal photonic crystal SiO₂ IOPC was prepared by sacrificial template method,followed by infiltration of rhodamine 6G derivative,RhM₇₁₆,to acquire a Fe³⁺sensitive fluorescence-enhanced PC sensing film.The macropore structure and large specific surface area of IOPC is helpful to the fast infiltration of Fe³⁺ions.RhM₇₁₆chelated specifically with Fe³⁺to generate a fluorescence product RhM₇₁₆-Fe³⁺.Simultaneously,a PC whose blue-band edge of stopband overlapped with the fluorescence emission wavelength of RhM₇₁₆-Fe³⁺was selected to enhance the fluorescence of RhM₇₁₆-Fe³⁺byvirtue of theslow photon effect.The fast and highly sensitive detection of Fe³⁺has been achieved.The fluorescence of the prepared sensing film can be observed obviously in 1 min after immersion in Fe³⁺solution,The limit of detection?LOD?was 0.18 nM.In addition,Fe³⁺ions chelated by RhM₇₁₆can be removed by washing the responded sensing film with ethylene diamine tetraacetic acid?EDTA?solution because EDTA shows stronger complexation ability than that of RhM₇₁₆,leading to the reproducibility,reusability and reversible detection for the sensing film.Therefore,the prepared fluorescence sensing film realized the fast,highly sensitive,highly selective and reversible detection of Fe³⁺ions and was effectively applied in the detection of Fe³⁺ions in YH River and foods.3.A rhodamine B derivative,RhM₇₅₂,was designed and synthesized,and then was infiltrated into SiO₂ IOPC to prepare a PC fluorescence sensing film for highly effective detection of Hg²⁺ions.The fluorescence can be observed within 5 min after immersion in mercury ion solution due to the interaction of mercury ion and RhM₇₅₂to form a fluorescence complex,and the fast diffusion of mercury ion benefited from the interconnected three-dimensional macropore structure of IOPC.Furthermore,the fluorescence can be effectively amplified by slow photon effect of PC whose blue-band edge of stopband matched with the emission wavelength of the fluorescence product.The detection sensitivity was improved,The limit of detection?LOD?was 0.33 nM.The prepared sensing film showed good selectivity and anti-interference based on the specific complexation of mercury ion and RhM₇₅₂.The stronger complexation of EDTA to mercury ions can remove the mercury ions chelated by RhM₇₅₂,resulting in the reactivity and reusability of the sensing film.The as-prepared sensing film was used to detect the content of Hg²⁺in cosmetics,demonstrating that the sensing film can be an effective platform for the detection of mercury ions in daily life.