Study On The Preparation,Optical Properties And Application Of Magnetic Photonic Nanorods

Responsive photonic crystals?RPCs?with tunable photonic band gap and structure color show promising applications in displaying,sensors,anti-counterfeiting and camouflage.As the smallest structural unit of magnetically responsive photonic crystals?MRPCs?,magnetic photonic nanochains have attracted much attention for their high magnetic responsiveness and color resolution.However,the adjacent particles in photonic nanochain are connected by insensitive material.Thus,they lose abilities of adjusting lattice constant via magnetic field?H?and responsiveness to non-H.Furthermore,the H-induced sedimentation is also a barrier of maintaining the stability of photonic properties.In this paper,the Fe₃O₄@PVP@SiO₂ photonic nanorods were prepared by combining magnetic assembly and slow sol-gel reaction.The novel MRPCs were developed based on photonic nanorods and various optical performances regulated by lattice defects were demonstrated.Combining magnetic assembly with UV-induced polymerization,the Fe₃O₄@PVP@PNIPAM photonic nanorods were fabricated by controlling curing time.Besides,the photonic crystals?PCs?agarose gel film which is responsive to both H and temperature was fabricated by using photonic nanorods as the basic display units.It will show a significantly high photonic stability due to the confinement effect of gel nets to the movement of photonic nanorods.The abundant and adjustable optical performances make the as-obtained photonic nanorods promising applied in the advanced security field.The main works in this dissertation are as follows:?1?Fe₃O₄@PVP@SiO₂ photonic nanorods of 1⁴?m were fabricated through a polyacrylicacid-catalysedhydrolysis–condensationreactionof?-mercaptopropyltrimethoxysilane around chain-like PC templates formed by monodispersed Fe₃O₄@PVP particles under H.?2?The magnetic assembly of typical photonic nanorods with average length of1?m was found that:with increasing H,the photonic nanorods firstly experience in situ rotational orientation along the H direction,followed by alignment and connection into long parellel nanochains via the spaces between the ends of adjacent photonic nanorods?named lattice defects?.As the number and size of the lattice defects changes with H,the MRPCs exhibit multiple optical properties.When the H is applied gradually,the diffraction peak intensity of photonic nanorods continuously increases;meanwhile,invariability,a red-shift and a blue-shift of the diffraction wavelength occur in sequential order.The abundant optical properties of photonic nanorods are also depended on the applied time under a fixed H.?3?The optical properties influenced by the structure parameters of photonic nanorods indicated that:with the increase of photonic nanorods length,the number of lattice defects decreased,and the red-shift and blue-shift range of diffraction wavelength become narrower.With the increase of inherent interparticle distance of photonic nanorods,the red shift process of diffraction peak disappeared gradually.?4?An optical anti-counterfeiting label was fabricated by sealing an ethanol suspension containing the Fe₃O₄@PVP@SiO₂ photonic nanorods.It shows rich optical performances under H and time,and corresponding structural colors and brightness tunable property,which can be used as anti-counterfeiting label.?5?The PC films with magnetic response and thermal sensitivity were fabricated by encapsulated Fe₃O₄@PVP@PNIPAM photonic nanorods suspensions into agarose gel under H.The optical microscope of typical PC film based on photonic nanorods with average length of 1?m indicated that the nanorods can rotate freely following the direction of H without spliced assembly behavior.It demonstrates that the free rotation of photonic nanorods is limited in micropores of agarose gel,which is well agree with the immutability of diffraction wavelength of PC film with the increase of H.The diffraction intensity of PC film is almost unchanged after 6 h under 200 Gs H,which declared that the nanorods have great stability in PC film.?6?The influences of the size of micropores of agarose gel and the average length of photonic nanorods on the magnetic responsiveness of PC film were investigated via reflection spectra.They show that with the decrease of micropores size,the diffraction saturation magnetic intensity increase.More and more photonic nanorods are fixed in an oriented state perpendicular to film surface with the average length of photonic nanorods increasing.When the nanorods length is more than 3?m,the magnetic responsiveness of the as-prepared PC film will be disappeared.The PC film shows the reversible thermal sensitivity.In the range of 8?to 32?,the diffraction wavelength blue shifts about 100 nm.Meanwhile,the thermal sensitivity is full reversible after multiple cycles.The magnetical and thermal responsiveness endow the as-obtained PC film potential applications in many fields such as information hiding,anti-counterfeiting,and identification.