|United States Of America||Issued Patent||9,180,484||11/10/2015||2011-499|
Responsive photonic materials are of great interest owing to their broad applications that are relevant to the controlling of colors. Being efficient and inexpensive, colloidal self- assembly has been widely studied for the fabrication of photonic crystal structures, especially for applications that can tolerate defects. The ideal case is to fix individual magnetic particle chains, which will produce the smallest possible photonic nanostructures that can effectively diffract at visible spectrum.
At UCR, inventors have developed a convenient and flexible approach for the fabrication of individually fixed nanochains with a magnetically responsive photonic property by combining magnetic assembly with sol–gel processes. The process is highly controllable: the periodicity can be varied by using Fe3O4 colloidal nanoclusters (CNCs) of different sizes, the interparticle spacing can be fine-tuned by adjusting the timing of magnetic field exposure, and the length of the chains can be controlled by changing the duration of the magnetic field exposure. The resulting photonic chains disperse randomly in solution in the absence of a magnetic field but align themselves and show diffraction color instantly when an external field is applied. The fixed photonic nanochains exhibit long-term structural/ optical stability and can be conveniently incorporated into many liquid or solid matrices.
a, b) SEM and c) TEM images of typical photonic nanochains. The particle chains are permanently fixed by silica coating so that they remain stable when dispersed in solution or dried on solid substrates.
Dark-field optical microscopy images of magnetic photonic chains with different diffraction colors switched between "off" (a, c, e: without magnetic field) and "on" (b, d, f: with vertical magnetic field) states. These photonic chains diffract at different wavelengths because they were prepared using Fe3O4 CNCs of different average sizes: a, b) 182 nm, c, d) 160 nm, e, f) 113 nm. All images are at the same scale.
Please see all inventions by Prof. Yadong Yin and his team at UCR
Magnetic properties, Nanomaterials, Photonic crystals, self assembly, Sol-gel process, Color displays, Biosensors, Chemical sensorsr, Biomedical Imaging