Fabrication of hydrazine sensor based on silica-coated Fe 2 O 3 magnetic nanoparticles prepared by a rapid microwave irradiation method Hashi Akhter a , Jannatul Murshed a , Md. A. Rashed a, b, c , Yoshifumi Oshima b , Yuki Nagao b , Mohammed M. Rahman d , Abdullah M. Asiri d , M.A. Hasnat a , Md. Nizam Uddin a , Iqbal Ahmed Siddiquey a, * a Department of Chemistry, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh b School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan c Department of Chemistry, Mawlana Bhashani Science and Technology University, Santosh, Tangail 1902, Bangladesh d Center of Excellence for Advanced Material Research (CEAMR) and Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, P.O. Box 80203, Saudi Arabia article info Article history: Received 14 October 2016 Received in revised form 19 December 2016 Accepted 20 December 2016 Available online 22 December 2016 Keywords: Magnetic materials Silica coating Microwave heating Sol-gel preparation Hydrazine Sensor abstract A facile, efficient and rapid method for fabrication of silica-coated Fe 2 O 3 magnetic nanoparticles (NPs) by a microwave (MW) irradiation method is reported. The homogeneous heating produced by the MW irradiation is the key to attaining the effective and uniform coating on Fe 2 O 3 magnetic nanoparticles (NPs) in water-ethanol solution. HRTEM images confirmed the successful formation of uniform silica shells around the Fe 2 O 3 NPs surface whereas FT-IR data show the structural differences between non- coated and silica-coated Fe 2 O 3 NPs. These uniformly coated Fe 2 O 3 NPs showed superior dispersibility than the bare Fe 2 O 3 NPs as confirmed by the zeta potential measurements. For potential chemical sensor development, silica-coated Fe 2 O 3 magnetic NPs were deposited onto a flat glassy carbon electrode (GCE, surface area, 0.0316 cm 2 ) to give a sensor with a fast response against selective hydrazine in phosphate buffer phase. Hydrazine sensor also exhibits a good sensitivity with long-term stability and enhanced electrochemical performances. The calibration plot is linear (r 2 : 0.9911) over the 0.2 nM to 2.0 mM hydrazine concentration ranges. The sensitivity and detection limit are ~12.658 mAmM 1 cm 2 and 76.0 pM (signal-to-noise ratio, at a SNR of 3) respectively. It is also commenced a promising future sensitive sensor development using silica-coated Fe 2 O 3 magnetic NPs by I-V method for the important applica- tions of hazardous and carcinogenic compounds in environmental fields. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Magnetic nanoparticles have earned much attention for re- searchers because of their supreme and exclusive magnetic prop- erties such as high coercivity, low Curie temperature, high magnetic susceptibility, etc. in bioseparation and detection of bio- logical entities, targeted drug delivery, data storage and catalysis [1e6]. Among various magnetic NPs, g-Fe 2 O 3 is the very promising and popular candidate due to their potential applications for fer- rofluids, high-density information storage, hypothermal cancer therapy, nuclear magnetic resonance imaging [7e11], grading of cells and magnetic partition of biochemical products [12]. Fe 2 O 3 NPs is attractive for the preparation of the metal-oxide based sensor due to its low production cost, narrow bandgap (~2.1 eV) and good chemical stability. However, the bare Fe 2 O 3 NPs having a high surface to volume ratio and high chemical activity tend to aggregate which result in loss of magnetism, dispersibility and restricts their application in sensors. Therefore, a suitable surface coating and developing some effective protection schemes is very important to enhance the stability, biocompatibility, and bio- recognition. The iron oxide NPs surface could be tailored by organic or inorganic materials, such as biocompatible biomolecules, silica, metals, etc [13]. Tailoring the surface avails to improve their sta- bility and screen the magnetic particle from the encompassing environment and can also be functionalised with a carboxyl group, amino group, biotin, and other biomolecules. Among others, silica * Corresponding author. Department of Chemistry, Shahjalal University of Science and Technology, Sylhet-3114, Bangladesh. E-mail address: iqbal_siddiquey@yahoo.com (I.A. Siddiquey). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom http://dx.doi.org/10.1016/j.jallcom.2016.12.266 0925-8388/© 2016 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 698 (2017) 921e929