Pengembangan Label Magnetik Green-Synthesized Ferofluida Fe3O4 Berbasis Minyak Jarak untuk Sensor Giant Magnetoresistance

Rahma Ayu Aliefia Aini Ulil Albab, Prof. Dr.Eng. Edi Suharyadi, S.Si, M.Eng.

2025 | Skripsi | FISIKA

Penelitian ini melaporkan keberhasilan sintesis ferofluida Fe3O4 berbasis minyak jarak menggunakan metode green synthesis (ekstrak Moringa oleifera) dan pelapis asam oleat. Karakterisasi difraksi sinar-X menunjukkan nanopartikel memiliki struktur face-centered cubic invers spinel dengan ukuran kristalit sebesar (10,10 ± 0,09) nm dan parameter kisi sebesar (8,15 ± 0,06) Å. Analisis fourier transform infra-red mengonfirmasi terbentuknya ferofluida Fe3O4 dengan munculnya gugus fungsi Fe-O (inti magnetit), C=O dan O-H (minyak jarak), serta COO- (asam oleat). Hasil karakterisasi vibrating sample magnetometer, nanopartikel Fe3O4 menunjukkan sifat soft ferromagnetic dengan nilai magnetisasi saturasi (Ms) 55,3 emu/g, magnetisasi remanensi (Mr) (11,9 ± 0,3) emu/g, dan koersivitas (Hc) (54,91± 0,06) Oe. Pengujian label magnetik pada sensor GMR AAL024 menunjukkan bahwa peningkatan konsentrasi ferofluida (5, 10, 15, 20 mg/mL) menghasilkan kenaikan respon tegangan keluaran. Selain itu, diperoleh nilai sensitivitas sebesar 3,94 mV/(mg/mL), linearitas R^2= 0,99, dan batas pendeteksian sebesar 0,4 mg/mL.

This study reports the successful synthesis of Fe3O4 ferrofluid based on castor oil using the green synthesis method with Moringa oleifera extract and oleic acid as a surfactant. X-ray diffraction characterization confirmed that the nanoparticles possess an inverse spinel face-centered cubic structure with a crystallite size of (10.10 ± 0.09) nm and a lattice parameter of (8.15 ± 0.06) Å. Fourier-transform infrared analysis verified the formation of Fe3O4 ferrofluid through the presence of Fe-O (magnetite core), C=O and O-H (castor oil), and COO- (oleic acid) functional groups. Based on vibrating sample magnetometer characterization, the Fe3O4 nanoparticles exhibited soft ferromagnetic behavior, with a saturation magnetization (Ms) of 55.3 emu/g, remanent magnetization (Mr) of (11.9 ± 0.3) emu/g, and coercivity (Hc) of (54.91 ± 0.06) Oe. Magnetic label testing using the GMR AAL024 sensor demonstrated that increasing the ferrofluid concentration (5, 10, 15, 20 mg/mL) resulted in a higher output voltage response. Furthermore, the system achieved a sensitivity of 3.94 mV/(mg/mL), linearity of R² = 0.99, and a limit of detection of 0.4 mg/mL.

Kata Kunci : Ferofluida Fe3O4, Giant magnetoresistance, Green synthesis, Label magnetik