Sains Malaysiana 52(11)(2023): 3253-3260

http://doi.org/10.17576/jsm-2023-5211-17

The Characteristic of pH Sensing of Potentiometric on Zinc Oxide and Aluminium-Doped Zinc Oxide Nanostructures

(Ciri Penderiaan pH Potensiometrik pada Nanostruktur Zink Oksida dan Zink Oksida Terdop Aluminium)

AIN ZAFIRAH KAMARUDDIN¹, LIM KAR KENG^2,*, MUHAMMAD AZMI ABDUL HAMID¹, NAIF H. AL-HARDAN¹, HUDA ABDULLAH³ & ENSAF MOHAMMED AL-KHALQI⁴

¹Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

²School of Liberal Studies, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

³Department of Electrical, Electronics and System Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

⁴Physics Department, Faculty of Applied Science, Thamar University, 87246 Dhamar, Yemen

Received: 11 May 2023/Accepted: 18 October 2023

Abstract

Numerous investigations have been conducted to increase the sensitivity and stability of metal oxide semiconductors as pH-sensing membranes. This paper will describe the pH sensing and characterisation of zinc oxide (ZnO) and aluminium-doped zinc oxide (ZnO:Al) as potentiometric pH sensors. The hydrothermal technique was used to grow ZnO and ZnO:Al thin film nanostructures with doping concentrations of 1, 3, and 5 at% Al on the cleaned ITO substrates. The pH potentiometric sensing was performed in a wide pH range of 4-12 and produced sensitivity, including stability of the nanostructures. The prepared samples were also characterized by X-ray diffraction analysis (XRD), field effect scanning electron microscope (FESEM), and energy dispersive X-ray (EDX) to explore the influence of aluminium concentration on structural and morphology characteristics and then prepared as electrodes for pH sensing. From the XRD result, the sharp peaks and high peak intensities demonstrated well crystalline of the synthesized ZnO nanorods. Furthermore, the FESEM shows the growth of array nanorods perpendicular over the surface of ITO. The sensitivity of the pH sensor with 3 at% ZnO:Al exhibits higher sensitivity (43.80 mV/pH) and larger linearity (0.9507).

Keywords: Aluminium-doped zinc oxide; doping process; hydrothermal process; pH-sensing; ZnO nanostructures

Abstrak

Banyak kajian telah dijalankan untuk meningkatkan sensitiviti dan kestabilan semikonduktor oksida logam sebagai membran penderia pH. Kertas ini akan menerangkan penderiaan pH dan pencirian zink oksida (ZnO) serta zink oksida terdop aluminium (ZnO:Al) sebagai penderia pH potensiometrik. Teknik hidroterma digunakan untuk menumbuhkan nanostruktur filem nipis ZnO dan ZnO terdop Al (ZnO:Al) dengan kepekatan dopan 1, 3 dan 5 at% di atas substrat ITO yang telah dibersihkan. Penderiaan pH potensiometrik dilakukan dalam julat pH yang luas iaitu 4-12 dan menghasilkan sensitiviti termasuk kestabilan nanostruktur. Sampel yang disediakan juga dicirikan oleh analisis pembelauan sinar-X (XRD), mikroskop elektron pengimbasan kesan medan (FESEM), sinar-X penyebaran tenaga (EDX) untuk meneroka pengaruh kepekatan aluminium terhadap ciri-ciri struktur dan morfologi dan kemudian disediakan sebagai elektrod untuk pengesanan pH. Daripada keputusan XRD, kemuncak tajam dan keamatan puncak yang tinggi menunjukkan hablur nanorod ZnO disintesis dengan baik. Tambahan pula, FESEM mendedahkan pertumbuhan tatasusunan nanorod berserenjang di atas permukaan ITO. Sensitiviti penderia pH pada 3 at% ZnO:Al menunjukkan sensitiviti yang lebih tinggi (43.80 mV/pH) dan lineariti yang lebih besar (0.9507).

Kata kunci: Kaedah hidroterma; nanostruktur ZnO; pengesanan pH; proses pengedopan; zink oksida terdop aluminium

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*Corresponding author; email: kk@ukm.edu.my