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Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals.

Wang X, Pu S, Ji H, Yu G - Nanoscale Res Lett (2012)

Bottom Line: The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties.In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT.The maximum relative enhanced value of QR exceeds 6.8% in our experiments.

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Science, University of Shanghai for Science and Technology, Shanghai, 200093, China. shenglipu@gmail.com.

ABSTRACT
Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (Δn) and figure of merit of optical properties (Q = Δn/α, where α is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field.

No MeSH data available.


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Schematic of the experimental setup for measuring the birefringence of the ferronematic materials.
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Figure 1: Schematic of the experimental setup for measuring the birefringence of the ferronematic materials.

Mentions: The magnetic-field-induced birefringence of the as-prepared ferronematic samples can be measured by the light extinction method, which consists of a sample cell placed between accurately set ‘crossed’ polarizers as shown in Figure 1[29]. A single-mode He-Ne laser emitting linearly polarized light with a wavelength of 632.8 nm is employed. The propagation direction of the incident light is normal to the applied magnetic field. The thin film sample is placed between a pair of solenoids, which generate a uniform horizontal magnetic field in the sample region. The strength of magnetic field can be adjusted by tuning the magnitude of the supply current. For the birefringence measurement, the optimum angle of the polarization direction of the incident linearly polarized light with respect to the magnetic field should be around π/4 [30]. At a given magnetic field, the light transmittance after the analyzer is investigated. Through rotating the analyzer, the maximum and minimum transmitted intensities (Imax and Imin) are measured, respectively. The birefringence Δn can be determined according the following:


Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals.

Wang X, Pu S, Ji H, Yu G - Nanoscale Res Lett (2012)

Schematic of the experimental setup for measuring the birefringence of the ferronematic materials.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475033&req=5

Figure 1: Schematic of the experimental setup for measuring the birefringence of the ferronematic materials.
Mentions: The magnetic-field-induced birefringence of the as-prepared ferronematic samples can be measured by the light extinction method, which consists of a sample cell placed between accurately set ‘crossed’ polarizers as shown in Figure 1[29]. A single-mode He-Ne laser emitting linearly polarized light with a wavelength of 632.8 nm is employed. The propagation direction of the incident light is normal to the applied magnetic field. The thin film sample is placed between a pair of solenoids, which generate a uniform horizontal magnetic field in the sample region. The strength of magnetic field can be adjusted by tuning the magnitude of the supply current. For the birefringence measurement, the optimum angle of the polarization direction of the incident linearly polarized light with respect to the magnetic field should be around π/4 [30]. At a given magnetic field, the light transmittance after the analyzer is investigated. Through rotating the analyzer, the maximum and minimum transmitted intensities (Imax and Imin) are measured, respectively. The birefringence Δn can be determined according the following:

Bottom Line: The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties.In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT.The maximum relative enhanced value of QR exceeds 6.8% in our experiments.

View Article: PubMed Central - HTML - PubMed

Affiliation: College of Science, University of Shanghai for Science and Technology, Shanghai, 200093, China. shenglipu@gmail.com.

ABSTRACT
Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (Δn) and figure of merit of optical properties (Q = Δn/α, where α is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field.

No MeSH data available.


Related in: MedlinePlus