Photonic nanorods with magnetic responsiveness regulated by lattice defects

Abstract

Herein, we use experiments and numerical simulations to demonstrate a novel class of magnetically responsive photonic crystals (MRPCs) based on photonic nanorods which exhibit multiple optical properties in a magnetic field (H) due to their fixed photonic nanorods and H-tunable lattice defects. As an example, superparamagnetic FeO@polyvinyl pyrrolidone (PVP)@SiO photonic nanorods were fabricated through a polyacrylic acid-catalysed hydrolysis-condensation reaction of γ-mercaptopropyltrimethoxysilane around chain-like PC templates formed by monodispersed FeO@PVP particles under H. For the as-proposed MRPCs, 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 visible red-shifts and blue-shifts of their diffraction wavelengths in addition to monotonous enhancement of their diffraction peaks. These optical properties are very different from those of previously reported MRPCs. The diversity of the structural colors and brightness of these MRPCs with H is also closely dependent on the applied time of H, the concentration of the photonic nanorods, and the structural parameters of the nanorods, including nanorod length and interparticle distance. Due to the difficult duplication of their various optical properties as well as their easy fabrication and low cost, MRPCs based on photonic nanorods are suitable for wide applications in forgery protection and information encryption.

Magnetic Nanomotor-Based Maneuverable SERS Probe

“…For obtaining magnetic nanoparticles as the main body of the "rod-like" nanomotors ( Figure 1(a)), we used hydrothermal synthesis [68,69] to acquire Fe 3 O 4 nanoparticles with the diameter of about 400 nm (Figure 1(b)). Then, an extra magnetic field of about 0.9~3.5 mT with fixed direction was applied, the magnetic nanoparticles with permanent magnetic dipoles would align themselves according to the external magnetic field, and at the same time, also attract each other to form short chains [70] ( Figure S1). Then, we grow a thin layer of silica on the external surface of the cross-linked chains to "fix" the shape of the short chains and form rigid nanorods (see more details in Materials and Methods and Figure 1(c)).…”

Bioinspired Stimuli‐Responsive Color‐Changing Systems

“…Stabilization of nanoclusters by means of both PVP and SiO 2 has also been recently developed. Fe 3 O 4 @PVP@SiO 2 photonic nanorods made of nanoclusters have been generated by means of a magnetic field . The nanorods are different in terms of both length (i.e., number of nanoclusters forming the chain) and interparticle distance.…”

Progress on Rapidly and Self-Assembly Magnetically Responsive Photonic Crystals With High Tunability and Stability

“…In this regard, similar to the traditional self-assembling methods, MRPCs are required to be prepared in suitable particle sizes for visible spectral segments and narrow particle size distribution. Accordingly, recent studies have found that surface-active agents, such as polyacrylic acid (PAA) (Ge et al, 2007) (Figures 1A,B), polyvinylpyrrolidone (PVP) (Ma et al, 2017) (Figures 1C,D) and oleic acid (OA) (You et al, 2017) (Figures 1E,F) were usually coated on MNPs or a carbon nanolayer with a large number of carboxyl groups (Wang et al, 2010) (Figures 1G,H) so as to introduce a large amount of charge on the MNPs surface with a large amount of charge to balance the attraction between MNPs so that it could disperse evenly in the solvent. Basically, in the absence of EMF, these synthesized SMNs are randomly dispersed and scattered distribution in an aqueous solution which is known as Brownian motion.…”