Research Of Photonic Crystal Sensing Technology Based On Active Nanogel

Hydrogels have shown great application prospects in the fields of biomedicine and label-free sensors owing to their good biocompatibility and water retention.However,the mechanical properties of conventional hydrogels are poor,which limits their application in life.At present,researchers have proposed many methods to enhance the mechanical properties of hydrogels based on the energy dissipation mechanism,such as adding nanoparticle crosslinkers,introducing a second hydrogel network,or designing topological structure hydrogels.The mechanical properties of the hydrogels can be effectively improved by these methods,but it will still be greatly reduced for the swelling hydrogel,and it is difficult for the deformed hydrogels to return to the initial state immediately.To solve these problems,this paper aims to improve the mechanical properties of the hydrogels,a new hydrogel with excellent mechanical properties and sensitive response properties was prepared by designing the polymer network.The photonic crystal is an optical material that could convert the morphological change of the stimulus-responsive hydrogel into an optical output signal.Based on this,the photonic crystal was combined with the stimulus-responsive hydrogel to construct a photonic crystal hydrogel film with simple operation,good sensitivity and visible signal,and further explored the new applications of the film in the field of mechanical sensing and chemical sensing.The details are as follows:In Chapter 2:A polyacrylamide hydrogel(NAG)with high elasticity and high strength was prepared by introducing acrylamide monomer and poly-N-isopropylacrylamide nanogel(NGs)crosslinker.The swelling ratio of this hydrogel is as high as 5500%,and the elongation ratio is 1500%for the swelling hydrogel.The hydrogel exhibits excellent mechanical properties such as resistance to slicing and compression,and the hydrogel could be recovered into the initial state after the external force disappeared.In addition,the hydrogels with different stimulus responses can be obtained by regulating the types of monomers,which expands the application range of these hydrogels.In Chapter 3:A photonic crystal hydrogel(PCNAG)sensor with mechanochromic ability was constructed by combined SiO₂@PS photonic crystal with NAG hydrogel.The photonic crystal is used as a signal element and the hydrogel used as a stimulus-responsive unit,the PCNAG senor could convert the changes in external force into a visible optical signal and output it.Upon stretching the hydrogel,a blue shift in the diffraction wavelength of the PCNAG sensor will be observed with the growing elongation,and the macrostructure color of this sensor will change from red to blue.In addition,the mechanical properties of the PCNAG sensor could be maintained after repeated stretching and releasing,showing excellent cyclic tensile performance.By adjusting the particle size of SiO₂@PS nanoparticles or the composition of the NAG hydrogel,PCNAG sensors with different structure color can be obtained.This new material may provide a new idea for the development of simple mechanochromic sensors.In Chapter 4:Based on the chelation between uranyl ions(UO₂²⁺)and amide and carboxylic acid groups,a two-dimensional photonic crystal hydrogel(PCNAAG)sensor was designed for UO₂²⁺monitoring and removal.The hydrogel has excellent swelling properties and its swelling ratio at room temperature is as high as 8000%.When the PCNAAG sensor reacts with the UO₂²⁺,UO₂²⁺will combine with the amino and carboxyl groups on the hydrogel skeleton to form four or six coordination complex,which shrinks the hydrogel and decreases the particle spacing of the photonic crystal,further increasing the diameter of the Debye diffraction ring and causing a blue shift of the structure color.The analysis and detection of UO₂²⁺can be achieved by observing the change of the Debye ring diameter or the change of the PCNAAG sensor structure color.This sensor has a stable signal,good specificity and reproducibility,the detection range for UO₂²⁺is 50 n M to 100mM,the maximum adsorption capacity is 1213.25 mmol kg^-1,and shows sensitive analysis performance of UO₂²⁺in actual water samples.