The Research On Inverse Opal Photonic Crystal Hydrogel For Detection Of Small Molecule Substances

With the increasing progress of science and technology,China's industry and agriculture have been greatly developed.However,at the same time,the fast development of industry and agriculture has also caused great damage to the surroundings.Irrational discharge of toxic waste liquid and excessive use of fertilizers and pesticides accelerate the deterioration of the ecological environment and even create extremely serious threat to the human health.Up to now,the commonly used detection methods for small molecule substances include fluorescence method,electrochemical method,chromatography-mass spectrometry,etc.Although these methods can achieve great detection effect,they often require expensive large-scale instruments,professionally trained personnel,complex sample preparation processes.In addition to the above analysis techniques,new types of nanomaterials such as nanorods,nanoparticles and photonic crystals have broad application prospects in the field of chemical biosensing recently.Among them,inverse opal photonic crystals hydrogel(IOPCH)have been broadly favored by researchers and become a research hotspot at home and abroad due to its unique advantage like large specific surface area,three-dimensional interconnected void structure,fast response speed and self-expression of response signals.In this thesis,responsive IOPCH sensing materials were designed for easy,fast,and visual detection of small molecule substances by combining photonic crystals with functionalized hydrogels.The main research contents are as follows:(1)As the Schiff base reaction between primary amine group on hydrogel and formaldehyde,we combined photonic crystals template with primary amine-functionalized hydrogel to develop an IOPCH sensing material that can visually detect formaldehyde in water.When the hydrogel was immersed into the solution of formaldehyde,the IOPCH film became less hydrophilic due to the formation of imine which generated by the Schiff base reaction between electrophilic carbon atoms of aldehyde groups and nucleophilic primary amino groups.Accordingly,the hydrogel with less hydrophilic caused the shrink of IOPCH film,which bridge the gaps between adjacent holes and lead to a clear blue-shift in diffraction wavelength.Therefore,the concentration of the formaldehyde solution can not only be detected by measuring the position of the diffraction peak of the inverse opal photonic crystal hydrogel,but also roughly judged by directly observing the structural color of the hydrogel.The minimum detectable concentrations for formaldehyde can reach 500uM.Furthermore,this developed sensor is proved to possess good recoverability and selectivity.(2)Based on the specific catalytic reaction between urease and urea and the higher specific surface area of the inverse opal photonic crystal,a kind of IOPCH sensing material was constructed by immobilizing urease on the framework of a hydrogel for rapid visual detection of urea and urease inhibitors.The urease immobilized on hydrogels can catalyze the hydrolysis of urea,and produce ammonium ions and bicarbonate ions.These generated ions shield the electrostatic repulsion between the carboxyl groups of hydrogels,resulting in the decrease of the osmotic pressure of the hydrogels and the loss of water from the hydrogel,which drives the pore spacing of the IOPCH smaller and lead to the blue shift of the diffraction peak wavelength.The hydrolysis reaction of urea could be suppressed while the urease inhibitor is introduced into the system so that the diffraction peak of the IOPCH does not undergo a obvious blue shift.The IOPCH sensing material can realize the visual detection of urea and phenylphosphoramide(urease inhibitor),and has good sensitivity(the lowest detection concentration for urea is ImM,paraphenylphosphine and the lowest detection concentration of acyldiamine is as low as 50nM)and specificity.