Optical transmission versus ac magnetization measurements for monitoring colloidal Ni nanorod rotational dynamics
| Autor: | Micha Gratz, Andreas Tschöpe |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
010302 applied physics
Materials science Acoustics and Ultrasonics Magnetic moment Condensed matter physics Field (physics) Relaxation (NMR) Physics::Optics Nanotechnology 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Magnetic field Magnetization Distribution function Amplitude 0103 physical sciences Nanorod 0210 nano-technology |
| Zdroj: | Journal of Physics D: Applied Physics. 50:015001 |
| ISSN: | 1361-6463 0022-3727 |
| DOI: | 10.1088/1361-6463/50/1/015001 |
| Popis: | Ni nanorods with an average length nm and diameter nm were synthesized using the AAO template method. The magnetization and optical transmission of nanorod colloidal dispersions in alternating magnetic fields were measured and analyzed with the objective of comparing the intrinsic Brownian relaxation times obtained with the two methods. The different physical origin of the measured signal, related to different moments of the orientation distribution function, and the non-linear effects expected for the large magnetic moments of the Ni nanorods at common field amplitudes required a comprehensive modelling. The time-dependent magnetization and optical transmission in ac magnetic fields was derived by numerical solution of the Fokker–Planck equation. The simulated time-dependent magnetization and optical transmission at a given frequency and field amplitude were analyzed analogous to experimental data to determine characteristic relaxation frequencies. Empirical relationships were derived which enabled extraction of the intrinsic Brownian relaxation time from the characteristic frequencies measured in the non-linear regime. Despite large differences in the characteristic frequencies obtained from magnetization and optical transmission measurements, the retrieved intrinsic Brownian relaxation times were found to agree well. The potential of ac magnetic field-dependent optical transmission for biosensing applications was demonstrated by monitoring the adsorption of the protein gelatine on the nanorod labels. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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