Abstract
Magnetically responsive colloidal photonic crystals can change their structural color according to the external magnetic field, which has been widely studied in recent years. However, due to lack of recognition ability towards non-magnetic analytes, these photonic crystals can be applied to constructing a sensor only when an additional stimuli responsive unit is involved. To address this problem, we used a functional protein to modify the magnetically responsive colloidal particles to construct chemically/magnetically dualresponsive nanoparticles. For a proof of concept research in this manuscript, we modified the colloidal particles with streptavidin, and the as obtained nanoparticles were used to detect biotinylated protein via a binding and assembling strategy, which is impossible for conventional photonic crystal sensors. Not only qualitative and quantitative detections were achieved, but also the average diameters of the biotinylated protein were correctly estimated. These results have demonstrated a multipurpose detection feature of our proposed colorimetric sensor.
Highlights
Upon application of an external magnetic field, magnetically responsive colloidal particles with diameters in the range of ca. 70 to 290 nm can assemble into photonic chains within seconds based on the balance of attractive and repulsive forces.[1,2,3,4,5,6,7] When observed with an incident light, the obtained periodical structure reveals structural colors which could be interpreted by Bragg’s law ( = 2nd sin, where is the diffraction wavelength, n the refractive index of dispersant, d the lattice constant, and the Bragg angle).[8]
SA was selected as the functional protein, biotinylated BSA (b-BSA) and biotinylated IgG (b-IgG) were selected as the analytes, which took advantage of the biotin-avidin model system in establishing a biosensing platform
For the high-resolution C1s X-ray photoelectron spectroscopy (XPS) spectra, the peak at 289.0 eV accounting for carbon atoms in the carboxyl groups demonstrated the capability of Fe3O4@C being functionalized via EDC/NHS chemistry
Summary
70 to 290 nm can assemble into photonic chains within seconds based on the balance of attractive (magnetic) and repulsive (electrostatic or steric) forces.[1,2,3,4,5,6,7] When observed with an incident light, the obtained periodical structure reveals structural colors which could be interpreted by Bragg’s law ( = 2nd sin , where is the diffraction wavelength, n the refractive index of dispersant, d the lattice constant, and the Bragg angle).[8] The variables d and can be manipulated magnetically by varying the magnetic field, or tuned non-magnetically by stimuli responsive polymers, to achieve desired structural colors. We believe that this novel CMDRP based binding and assembling detection paradigm can fabricate colorimetric sensors for a variety of analytes
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