The Magnetic Responsive Photonic Crystals-based Microchemical Sensors

Responsive photonic crystals?RPCs?have the advantages of non-toxicity,non-label,low cost and visualization,thus they have a wide application prospects in the fields of sensing,display,anti-counterfeiting and camouflage.The pH-RPCs developed are mainly bulky gel membrane or ball typed materials prepared by the introduction of responsive hydrogels into the photonic crystal structure,these responsive gel compositions can not only fix the photonic crystal structure,but also response to external stimuli,relying on its own volume expansion or contraction to regulate the photonic band gap.However,these bulky pH-RPCs materials whose photonic crystal structures are fixed in the gel membrane will face some challenges in their preparation,using process and preservation:the preparation process is relatively complex,time-consuming and the photonic crystal structures in the process of assembling vulnerability to kinds of solvent,monomer,pH value of interference;The bulky gel materials and the fixed photonic crystal structures make the pH-RPCs have problems such as long response time,low sensitivity,poor durability,easy occurrence of uneven expansion or contraction;because these RPCs above are short of particularly excellent response performanc and relative large gel volume,their applications are limited in many areas,such as real-time monitoring in microenvironment and the detection of some large molecules.In the light of of the problems above,in this paper,we use the characteristics of the interaction between the shell PVP molecules of the Fe₃O₄@PVP and functional monomers,the pH responsive Fe₃O₄@PVP@poly?AA-co-HEMA?core-shell gel typed colloidal nanoparticles are prepared.The novel magnetic responsive photonic crystals which response to external stimuli were constructed by those above as-obtained colloidal nanoparticles.Furthermore,the response performances of pH were explored.Besides,the PAA colorimetric sensor based on the magnetic responsive photonic crystals assembled by the Fe₃O₄@PVP colloidal nanoparticles,the physical crosslinking of hydrogen bond between PVP and polymer PAA was used in the building of the PAA sensor.and the effect of macromolecule PAA on their optical properties were investigated.The main research works of the thesis are as follows:?1?The Fe₃O₄@PVP nanoparticles were chosed as raw materials,and the Fe₃O₄@PVP@poly?AA-co-HEMA?core-shell gel typed colloidal nanoparticles with several nanometer's shell were prepared by a hydrogen bond-guided template polymerization method.?2?Those RPCs pH colorimetric sensor were constructed by the assembling of those as-obtained Fe₃O₄@PVP@poly?AA-co-HEMA?core-shell gel typed colloidal nanoparticles.They showing many excellent responsive performances,such as good durability bright and homogeneous structural colours,high sensitivity???p/?pH329.22 nm/pH?,short response time?<44.30 ms?,and the diffraction spectrum of the photonic crystals when pH was from 4.40 to 7.20,almost covers the whole visible spectrum,showing excellent color performance.In addition,due to the reversible assembly?deformability?,ultra small size?nanometer level?and the ability of responsiveness to the pH and magnetic field at the same time of the as-obtained nanoparticles.They can pass through the small environment?such as the narrow channel?to the designated area to realize the detection of analytes or other goals.?3?The preparation of the Fe₃O₄@PVP@responsive hydrogel core-shell nanoparticles can be designed,owing to the universal hydrogen bond-guided template polymerization method.As for the responsive monomers which can form hydrogen bond directly with PVP molecules,we can observe the above preparation method of the Fe₃O₄@PVP@poly?AA-co-HEMA?nanoparticles;while as for those responsive monomers which can't form hydrogen bond directly with PVP molecules,such as NIPAM,we can prepare thermo-responsive core-shell colloidal nanoparticles by introducing“bridging molecule”?such as PAA molecule chains?to concentrate the responsive monomers around the Fe₃O₄@PVP nanoparticles.?4?The response time of the magnetic responsive photonic crystals assembled by the molecular brush Fe₃O₄@PVP nanoparticles was investigated in different solvent systems;The effects of different PAA?M.W 3000?concentrations on the molecular brush typed core-shell nanoparticles?Fe₃O₄@PVP?and the response mechanism were investigated.Under the fixed magnetic field,with the increase of PAA concentration(0-2000 mg?L^-1),the diffraction wavelength shifted to red firstly and then to blue,which cover the whole visible spectrumm.When the PAA concentration is 40 mg?L^-1,the diffraction wavelength reach to the maximum.?5?The influence of the magnetic field on the molecule brush typed Fe₃O₄@PVP colloidal nanoparticles under the effect of different PAA concentrations was explored.The compressible capacity of the shell of Fe₃O₄@PVP nanoparticles under different PAA concentration was demonstrated by the different magnetic field.More importantly,we can distinguish quickly the different PAA concentration which corresponding to the same diffraction wavelength by changing the magnetic field.?6?The selectivity to PAA of the photonic crystals sensing system assembled by Fe₃O₄@PVP nanoparticles was investigated.The Fe₃O₄@PVP@poly?AA-co-HEMA?magnetic magnetic colloid particles were prepared by a hydrogen bond-guided template polymerization method.The photonic crystals pH colorimetric sensor under the constant magnetic field shows the characteristics of fast response,high sensitivity;and the characteristic of the reversible assembly makes they applied to the detection of microenvironment;The PAA chemical colorimetric sensor was developed via the priciple of the changing of the photonic band induced by the the hydrogen bonds between the molecular brush of the Fe₃O₄@PVP and the PAA of macromolecular analytes.The photonic crystals chemical sensor shows good identification to the concentration and the molecular weight.