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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.


Related in: MedlinePlus

Birefringence of pure MFs and MFs doped with 5CB. Birefringence of pure MFs with different magnetic particle concentrations and MFs doped with 5CB as a function of magnetic induction.
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Figure 2: Birefringence of pure MFs and MFs doped with 5CB. Birefringence of pure MFs with different magnetic particle concentrations and MFs doped with 5CB as a function of magnetic induction.

Mentions: Figure 2 shows the birefringence of pure MFs with different magnetic particle concentrations as a function of magnetic induction. From Figure 2, we can see that the birefringence of samples a to d increases gradually with the magnetic induction and tends to saturate at high field. This is attributed to the formation of magnetic chains under external magnetic field. Application of external magnetic field will induce structural ordering within the MF confined between two glass plates, which are due to the interaction between the magnetic dipoles induced at the particle sites [31,32]. This results in the optical anisotropy of MF under applied magnetic field. When the applied magnetic field is small, the aligned discrete magnetic short chains will form. With further increasing the strength of the magnetic field, the short chains will start to combine with each other to become longer discrete chains. The longer the chain structure is, the stronger the spatial anisotropy is and the larger the birefringence of MF becomes.


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)

Birefringence of pure MFs and MFs doped with 5CB. Birefringence of pure MFs with different magnetic particle concentrations and MFs doped with 5CB as a function of magnetic induction.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Birefringence of pure MFs and MFs doped with 5CB. Birefringence of pure MFs with different magnetic particle concentrations and MFs doped with 5CB as a function of magnetic induction.
Mentions: Figure 2 shows the birefringence of pure MFs with different magnetic particle concentrations as a function of magnetic induction. From Figure 2, we can see that the birefringence of samples a to d increases gradually with the magnetic induction and tends to saturate at high field. This is attributed to the formation of magnetic chains under external magnetic field. Application of external magnetic field will induce structural ordering within the MF confined between two glass plates, which are due to the interaction between the magnetic dipoles induced at the particle sites [31,32]. This results in the optical anisotropy of MF under applied magnetic field. When the applied magnetic field is small, the aligned discrete magnetic short chains will form. With further increasing the strength of the magnetic field, the short chains will start to combine with each other to become longer discrete chains. The longer the chain structure is, the stronger the spatial anisotropy is and the larger the birefringence of MF becomes.

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