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<p>Ferrofluids, exhibiting the combined properties of liquids and magnetic responsiveness, have diverse potential applications in science and engineering. In this study, ferrofluids were synthesised using ∼ 10&#xa0;nm iron oxide nanoparticles coated with citric acid and oleic acid, dispersed in polyvinyl alcohol (PVA) and kerosene, respectively. PVA-based ferrofluids were employed to prepare solid films by casting onto glass slides, while kerosene-based ferrofluids were used to form dynamic fluid films confined between two slides. Magnetic patterning in PVA films was achieved by drying under parallel and perpendicular magnetic fields using permanent magnets. Optical micrographs revealed chain-like structures indicative of field-induced alignment. Transmission of green laser light (532&#xa0;nm) through parallelly patterned PVA films produced diffraction patterns resembling those from a series of wires. In situ magnetic patterning of kerosene-based ferrofluid films was studied under parallel magnetic fields using the same laser source. The diffraction patterns showed continuous lobes instead of sharp spots, attributed to the absence of perfectly periodic chain-like structures with uniform chain spacing. Magnetochromatic effects were observed as colour changes under white light illumination: perpendicularly patterned PVA films exhibited distinct colour modulation, while kerosene-based films showed a transition from yellow to red in CCD images. UV–Vis optical absorption measurements indicated that the magnetic field modifies the chromatic properties of ferrofluids, as demonstrated by a corresponding shift in their optical band gap. These observations confirm that ferrofluids can act as tunable optical gratings suitable for optical switches, filters, and sensors. Dielectric studies (100–1&#xa0;MHz) of kerosene-based ferrofluids further revealed a decrease in dielectric constant and loss with increasing frequency, both influenced by applied magnetic fields, demonstrating the potential of these ferrofluids as magnetically tunable liquid dielectrics.</p> Graphical abstract <p></p>

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Investigations on the optical and dielectric properties of ferrofluids for tunable grating and dielectric applications

  • 期刊论文

  • 发表日期：

    2026年1月2日

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  • Laveena Varghese,
  • P. Divya Joy,
  • Aneesh George,
  • C. M. Avanthika,
  • Smitha Bhaskaran,
  • Imaddin A. Al-Omari,
  • K. A. Malini,
  • E. Veena Gopalan

摘要

Ferrofluids, exhibiting the combined properties of liquids and magnetic responsiveness, have diverse potential applications in science and engineering. In this study, ferrofluids were synthesised using ∼ 10 nm iron oxide nanoparticles coated with citric acid and oleic acid, dispersed in polyvinyl alcohol (PVA) and kerosene, respectively. PVA-based ferrofluids were employed to prepare solid films by casting onto glass slides, while kerosene-based ferrofluids were used to form dynamic fluid films confined between two slides. Magnetic patterning in PVA films was achieved by drying under parallel and perpendicular magnetic fields using permanent magnets. Optical micrographs revealed chain-like structures indicative of field-induced alignment. Transmission of green laser light (532 nm) through parallelly patterned PVA films produced diffraction patterns resembling those from a series of wires. In situ magnetic patterning of kerosene-based ferrofluid films was studied under parallel magnetic fields using the same laser source. The diffraction patterns showed continuous lobes instead of sharp spots, attributed to the absence of perfectly periodic chain-like structures with uniform chain spacing. Magnetochromatic effects were observed as colour changes under white light illumination: perpendicularly patterned PVA films exhibited distinct colour modulation, while kerosene-based films showed a transition from yellow to red in CCD images. UV–Vis optical absorption measurements indicated that the magnetic field modifies the chromatic properties of ferrofluids, as demonstrated by a corresponding shift in their optical band gap. These observations confirm that ferrofluids can act as tunable optical gratings suitable for optical switches, filters, and sensors. Dielectric studies (100–1 MHz) of kerosene-based ferrofluids further revealed a decrease in dielectric constant and loss with increasing frequency, both influenced by applied magnetic fields, demonstrating the potential of these ferrofluids as magnetically tunable liquid dielectrics.

Graphical abstract