The Research On Detection And Removal Of Uranyl Ions By Photonic Crystal Hydrogel

Nuclear energy,as a promising clean energy can replace traditional fossil energy,is used in nuclear power,industry,and national defense.However,with the development and application of nuclear energy,the problems of nuclear pollution also accompany.As the main nuclear fuel,uranium is widely used,but the wastewater of uranium will represent a serious threat to ecological and human health.Usually,the detection of uranium relies on expensive precision instruments,and requires the operation of professionals.Nevertheless,it is difficult to realize in-situ real-time uranium monitoring.As for the efficient removal of uranium in wastewater,many technologies have been developed,such as membrane separation,extraction and adsorption.But all of these technologies can’t simultaneously efficiently remove and sensitively detect uranium.However,the emergen ce of photonic crystals（PCs）,which own unique optical properties,provides a new idea for solving these problems.In this thesis,new methods for simple,sensitive and visual detection and efficient removal of uranyl ions(UO₂²⁺)were developed,in which PCs were used as signal conversion elements to be combined with functional hydrogels.We also studied on how to overcome the problem that the colors of PCs were seriously affected by incident angle,which was disadvantageous to the accuracy and stability of detection.The details are as follows:（1）Through increasing the refractive index of photonic crystal templates,the angle dependence property of PCs could be restrained.We synthesized the spherical hydrophilic CdS@SiO₂ core-shell particles by utilizing high refractive index material（CdS）as cores,and modifying the CdS cores with hydrophilic SiO ₂ shells.After vertical deposition,we prepared low angle dependence CdS@SiO ₂ photonic crystal films.Different from the traditional SiO₂ and PS temples,the structural color of the CdS@SiO₂ photonic crystal film is low angle dependence,which can solve the problems that the angle dependence and the intrinsic color instability severely restrict the practical applications of PCs.（2）As UO₂²⁺can complex with multiple coordination groups and form tetracoordinate to hexacoordinate complexes,we combined CdS@SiO ₂ photonic crystal template with functional hydrogel to develop a low angle dependence photonic crystal hydrogel（LAD-PCH）,which could be used as UO₂²⁺sensor and remover.Because of abundant active sites of carboxyl and amide groups in hydrogel as ligands to complex with UO₂²⁺,the hydrogel would shrink after complexing with UO₂²⁺,and the particle spacing inside PCs temples would decrease immediately.This volume change could be transmuted into spectra change,which triggered the blue-shift of diffraction wavelength of LAD-PCH.What’s more,this color change was visible to the naked eye,and overcame the intrinsic color instability of normal PC sensors dependent on incident angle.Furthermore,our CdS@SiO₂ LAD-PCH material could detect the concentration of UO₂²⁺sensitively as low as 100 pM,and remove UO₂²⁺high-efficiently as the maximum adsorption capacity of it was about4.3 mmol·g^-1.Thus,it’s potential to use LAD-PCH to detect and remove UO₂²⁺in real water samples.（3）Based on the three-dimensional interpenetrating macroporous structure and high specific surface area of inverse opal photonic crystal,an inverse opal photonic crystal hydrogel（IO-PCH）was designed to be used as sensing film for visual detection and efficient removal of UO₂²⁺.The method to prepare IO-PCH was simple and convenient,and suitable for preparing large area hydrogels.Besides,the UO ₂²⁺detection and removal principle of IO-PCH was also based on the complexation reaction between UO₂²⁺and the amide groups and carboxyl groups modified on the hydrogel skeleton.When the diffraction spectrum of the hydrogel blue-shifted,the color of the hydrogel would change simultaneously and also be naked-eye visible.This IO-PCH had the minimum UO₂²⁺detection concentration of 50 nM,the maximum adsorption capacity of about 2.5 mmol·g^-1,and anti-interference ability,which could be applied in practical environments.