Jurnal Penelitian dan Pengkajian Ilmu Pendidikan: e-Saintika https://journal-center.litpam.com/index.php/e-Saintika/index July 2021 Vol. 5, No. 2 e-ISSN: 2615-6881 pp. 168-174 Jurnal Penelitian dan Pengkajian Ilmu Pendidikan: e-Saintika, July 2021 Vol. 5, No. 2 | |168 Development of rGO/Fe3O4 Composites as Glucose Biosensors * Diah Hari Kusumawati, Rahayu Yudia Mufida Physics Department, Faculty of Mathematics and Natural Science, Universitas Negeri Surabaya, Jl. Ketintang, Surabaya, East Java Province, 60231, Indonesia. *Corresponding Author e-mail: diahkusumawati@unesa.ac.id Received: May 2021; Revised: June 2021; Published: July 2021 Abstract The rGO/Fe3O4 composite is one type of composites that can be used as a biosensor material, especially glucose sensors. The main ingredients of the composite synthesis are graphite and iron sand. The synthesis process of Fe3O4 was done using the coprecipitation method, while the graphite oxidation process was accomplished using the modified Hummer's method. The composites were formed using the ex-situ wet mixing method. The formed iron sand and graphite were characterized using FTIR and XRD, and it was found that Fe3O4 was formed from the appearance of the Fe-O bond, the oxidation process of graphite was seen from the appearance of the C=O bond, and the detection of Fe peaks corresponded to the cubic crystal plane. Likewise, the composites formed were also characterized using FTIR and XRD for identification of the rGO/Fe3O4 composite formation. It was proven from the presence of Fe-O and C-O bonds and the appearance of an amorphous peak of rGO in the XRD results. The performance of the rGO/Fe3O4 composites as the glucose biosensor was examined by varying the mass of Fe3O4 on the composite, using UV-Vis spectroscopy. The performance of the rGO/Fe3O4 composite biosensor in absorbing glucose reached optimum at a mass variation of 0.3 grams of Fe3O4, as demonstrated by by the lowest absorbance peak with an intensity of 0.0048 at a wavelength of 440 nm, corresponding to glucose entrappment of 7.1 mg/gram. Keywords: rGO/Fe3O4; Biosencsor; Glucose How to Cite: Kusumawati, D. H., & Mufida, R. Y. (2021). Development of rGO/Fe3O4 Composites as Glucose Biosensors. Jurnal Penelitian Dan Pengkajian Ilmu Pendidikan: e-Saintika, 5(2), 168–174. https://doi.org/10.36312/esaintika.v5i2.493 https://doi.org/10.36312/esaintika.v5i2.493 Copyright© 2021, Kusimawati & Mufida This is an open-access article under the CC-BY-SA License. INTRODUCTION Research on carbon-based materials is growing rapidly. One of the most researched allotropes of carbon is reduce Graphene Oxide (rGO). rGO has unique properties that can cover a wide range of applications, including supercapacitors, microwave absorbers, electrocatalytics and biosensors. The unique characteristics of rGO include high electrical conductivity, wide surface area and a good electrocatalyst. As such, rGO is a good material for mobilizing and absorbing ions. This property makes rGO the material of choice and is attractive to be used as a biosensor. The biosensor derived from rGO has been studied and applied for glucose, especially for people with Diabetes Mellitus (Qiu et al., 2012). Glucose Oxidase (GOx) shows high catalytic activity, but because it is in a non-conductive environment, it is difficult for ion transfer to occur (He et al., 2012). Therefore, to improve the performance of the glucose biosensor, a magnetic material that has good adsorption properties catalytic and electrical conductivity is needed.