Study On Preparation And Performance Of Spiropyran Based Gel Sensor

As an important part of the organisms,metal ions are involved in various life activities such as osmotic pressure regulation,metabolism,signal metabolism,and nucleic acid processing.However,excessive or insufficient certain metal ions will affect the normal conduct of life activities.Therefore,the qualitative and quantitative detection of metal ions is critical.Spiropyran is a class of photochromic dye molecules that can be transformed from colorless ring-closed benzospiran(SP)to colored ring-opened merocyanine(MC)under the irradiation of ultraviolet light,and the phenolic hydroxyl group ol MC can bind with various metal ions(Mn+)through electron transfer to form a complex(MC-Mn+).Under the irradiation of white light,MC can be convered into SP,and metal ions are dissociated from spiropyran,the process is reversible.In this dissertation,taking advantage of the light-controlled reversible binding between spiropyran and metal ions,two kinds of gel sensors containing spiropyran were constructed on the basis of spiropyran.Then the application in the visual detection of metal ions and the deformation and discoloration behavior of gel sensors were explored.The details are as follows:In chapter one,several stimuli-responsive hydrogel sensors were introduced,and summarized the research progress of spiropyran in metal ion detection,including the structure and properties of spiropyran,and the application of spiropyran in metal ion detection.In chapter two,a colorimetric gel sensor which could be used for visual detection of various metal ions was reported.The gel was prepared by using(PNIPAAm),methacrylate spiropyran(SPMA)as the polymerization monomer,and N,N'-methylene bispolyamidoamide(Bis-Am)as crosslinking under the irradiation of blue light.When the merocyanine in the gel bound different metal ions(Ca2+,Mg2+,Co2+,Zn2+ and Cu2+ions)to form a complex(MC-M2+),the position and intensity of the absorption peaks changed in the UV-Visible absorption spectrum,resulting in the color change of gel.When the gel was irradiated with white light,the metal ions was dissociated by the transformation from MC to SP.The results of experimental and theoretical model calculations showed that the tendency of the relative affinity of the gel to metal ions was:Cu2+>Co2+?Zn2+>Mg2+>Ca2+.Furthermore,the gel exhibited excellent fatigue resistance and reversible binding/dissociation of metal ion.Combining the ionoprinting technique,the gel could achieve fast,convenient,and repeatable detection of multiple metal ions.In chapter three,a deformable colorimetric gel for the detection of ferric ions was reported.The gel was prepared by the crosslinking of NIPAAm,acrylamide-6-aminocaproic acid(A6ACA),SPMA,and Bis-Am.Under ultraviolet light,the spiropyran moiety switched to the colored merocyanine and selectively bind with Fe3+,resulting in the disappearance of the absorption peak of merocyanine and the color changing of the gel from red to yellow.It was proved by the mechanical and internal morphologies test that the gel network crosslinked more densely and thus the mechanical properties are enhanced in the presence of Fe3+.By printing Fe3+ on its surface,the gel showed deformation behavior.The gel underwent reversible instant discoloration and bending deformation as response to the temperature.When exposed to strong acid,the gel showed the discoloration behavior owing to the transformation from MC to MCH+;while under strong alkaline conditions,the gel exhibited swelling deformation behavior.Combining two external stimuli,such as temperature-pH and temperature-Fe3+,the deformation and discoloration behavior of the gel will have great application potential in intelligent visual detection/color rendering systems and bionic color changing systems.