Photonic Crystals: Fabrication And Application In Sensors

Photonic crystal (PC) can manipulate the propagation of light as an innovativefunctional material. Its structural color is visible to the naked eyes when its photonic bandgap (PBG) is located in the visible-light region. Therefore, PC incorporated withstimulus-responsive materials is widely used in the sensor systems due to its color changeswhile stimulated by the corresponding external stimuli. In this study, three differentresponsive PCs were fabricated to expand applications in the field of sensors.First of all, we fabricated monodisperse polymethyl methacrylate (PMMA) colloidalmicrospheres in nanoscale by a seed method，and then self-assembled them into2Dmonolayer periodic structures at the air/water interface by a needle tip flow method. ThisPC was used to detect p-nitrophenol in water, which is a kind of environmental pollutant.However, there was no significant response to this target after being immobilized on the2Dcolloidal array.Secondly,3D PMMA colloidal arrays were prepared and embedded in thebiodegradable cellulose to fabricate cellulose photonic crystal film (CPCF). This film wasused in the detection of volatile organic compounds. It showed different responses toalcohol, n-propanol, isopropanol and n-butanol in the forms of liquid and vapor. Itsstructural colors changed from blue to green, which is convenient to the naked eyedetection. The structural color of CPCF changed from blue to transparent for liquid acetoneand toluene and a week respond for formaldehyde vapor at200ppm. Meanwhile, wetentatively developed methods to fabricate the inverse opal cellulose photonic crystal film.When using3D PMMA colloidal arrays as templates, no proper solvents were found todissolve PMMA colloidal microspheres completely. So, the reflection of this inverse opalcellulose photonic crystal film presented very weak intensity on the spectrogram.Thirdly,2D and3D mechanically responsive nanocomposite photonic hydrogel werefabricated by embedding photonic crystals into nanocomposite hydrogel. When westretched the3D photonic hydrogel, its structural color gradually changed from violet toreddish, which covered the whole visible-light region. Similarly, the Deby Diffraction of2D photonic hydrogel changed from circle to ellipse. When strain is large enough, its DebyDiffraction presented two approximative parallel lines.