Abstract
Extremely stable and biocompatible 3D magnetically responsive photonic crystals (MRPCs) are successfully prepared in aqueous solution. Classic hydrothermal synthesis was applied for preparation of the Fe3O4@C core. Modified Stöber method was then employed for synthesis of the different size of Fe3O4@C@SiO2. Unlike the traditional magnetic nanoparticles, the highly negative charged superparamagnetic nanospheres (SMNs), i.e., the double-shell structure Fe3O4@C@SiO2 are capable of rapidly self-assembling into 3D MRPCs with full visible and various colors that can be periodically and reversibly tuned under different kinds of external magnetic fields (EMFs) within 1 s. The assembling behavior and mechanism of the 3D MRPCs under EMF were monitored and analyzed. The preparation is simple and the size of the SMN is easily controllable by adjusting the amount of catalyst. Compared with the previous works, the synthesized 3D MRPCs are hydrophilic, and exhibit extremely high stability after 6-month storage. To conclude, our study provides an effective two-step strategy for fabrication of biocompatible 3D MRPCs and it reveals great potentials in biological fields.
Highlights
Photonic crystals (PCs) are considered as one of the tunable optical nanomaterials and exhibit high brightness and saturation, permanent color, and an iridescent effect (Vukusic and Sambles, 2003; Teyssier et al, 2015)
The highly charged surfaces provide sufficient long-range interparticle electrostatic repulsion, which balances the magnetic dipole-dipole attraction and establishes a force equilibrium within the chain-like structures (Wang and Yin, 2016) In this work, we have prepared extremely stable and highly charged Fe3O4@C@SiO2 superparamagnetic nanospheres (SMNs), i.e., the 3D magnetically responsive photonic crystals (MRPCs) which are capable of orderly self-assembling in water and biocompatiblity under external magnetic fields (EMFs)
The different diffraction wavelength of MRPC could be obtained by changing the distance of microspheres (d), which could be adjusted by tuning the particle size or EMF intensity, (Yang et al, 2016) such as gradually weakening the EMF by increasing the distance between the glasses and magnet in our work
Summary
Photonic crystals (PCs) are considered as one of the tunable optical nanomaterials and exhibit high brightness and saturation, permanent color, and an iridescent effect (color changes with viewing angles) (Vukusic and Sambles, 2003; Teyssier et al, 2015). The highly charged surfaces provide sufficient long-range interparticle electrostatic repulsion, which balances the magnetic dipole-dipole attraction and establishes a force equilibrium within the chain-like structures (Wang and Yin, 2016) In this work, we have prepared extremely stable and highly charged Fe3O4@C@SiO2 SMNs, i.e., the 3D MRPCs which are capable of orderly self-assembling in water and biocompatiblity under EMF. The critical point for the preparation of 3D MRPCs lies in the establishment of a balance among the dipole-dipole attractive forces, exclusion forces, and dipole-dipole electrostatic repulsive forces. This approach is able to endow the SMNs with a long-term stability almost independent of ionic strength, pHvalue and solvent polarity. Compared with the previous works (Whitesides and Boncheva, 2002), our synthesized SMNs are hydrophilic, and exhibit extremely high stability after 6-month storage
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