Sains Malaysiana 55(10)(2026): 1639-1652

http://doi.org/10.17576/jsm-2026-5510-04

 

Plasmon-Assisted Visible Light Photocatalytic Activity of Biosynthesized Ag/TiO₂

(Aktiviti Fotopemangkin Cahaya Nampak Berbantukan Plasmon bagi Ag/TiO₂ Biosintesis)

 

NAZWA JON^1,2, RIZAFIZAH OTHAMAN^1,3,*, MOHAMAD AZUWA MOHAMED^1,3, NURUL AMNI ABDULLAH^1,2, ROZIDA MOHD KHALID^1,3 & ABDEL-NASSER KAWDE⁴

 

¹Department of Chemical Science and Food Technology, Faculty of Science and Technology,

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

²Faculty of Applied Sciences, Universiti Teknologi MARA, Perak Branch, Tapah Campus, 35400 Tapah Road, Perak, Malaysia

³Polymer Research Center (PORCE), Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

⁴Department of Chemistry, College of Sciences, University of Sharjah, P. O. Box 27272 Sharjah, United Arab Emirates

 

Received: 31 May 2026/Accepted: 9 September 2026

 

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

 

Abstract

Green synthesis involves developing and applying techniques that prioritize the environment by minimizing the utilization of harmful substances and reducing waste production. In this study, Ag/TiO₂ photocatalysts were synthesized via a one-pot biosynthesis approach using Oroxylum indicum (OI) leaf extract for enhanced photocatalytic activity under visible light irradiation. The OI leaf extract showed the presence of significant amount of phenolic acid (47.3 mg QE/g dry weight) and flavonoid (44.1 mg QE/g dry weight), potentially serving as the main reducing and capping agent in the synthesis process. Physicochemical characterization confirmed that the Ag nanoparticles were decorated on the TiO₂ surface without lattice alteration, as proved by XRD, FESEM, TEM, and XPS. Furthermore, UV–DRS analysis showed a significant reduction in the band gap energy upon Ag incorporation, with 50-Ag/TiO₂ exhibiting the lowest band gap value of 2.09 eV. This reduction was accompanied by enhanced absorption in the visible-light region, which can be attributed to the surface plasmon resonance (SPR) effect of Ag nanoparticles. The Ag/TiO₂ exhibited significant enhancement in photocatalytic activity towards the removal of ciprofloxacin (CIP), achieving 91% for 50-Ag/TiO₂ under visible light irradiation, attributed to improved charge carrier separation. Scavenger and recyclability tests confirmed the dominant role of •O₂^- and the stability of the photocatalyst. A plausible photocatalytic degradation mechanism was proposed based on the experimental findings. This work demonstrates a sustainable strategy for developing plasmonic photocatalysts with enhanced visible light photocatalytic activity for the removal of emerging pollutants.

Keywords: Ag/TiO₂; biosynthesis; ciprofloxacin; photocatalyst; surface plasmon resonance

 

Abstrak

Sintesis hijau melibatkan pembangunan dan penggunaan teknik yang mengutamakan kelestarian alam sekitar dengan meminimumkan penggunaan bahan berbahaya serta mengurangkan penghasilan sisa. Dalam kajian ini, fotomangkin Ag/TiO₂ disintesis melalui pendekatan biosintesis satu langkah menggunakan ekstrak daun Oroxylum indicum (OI) bagi meningkatkan aktiviti fotomangkin di bawah sinaran cahaya nampak. Ekstrak daun OI menunjukkan kehadiran sejumlah besar asid fenol (47.3 mg QE/g berat kering) dan flavonoid (44.1 mg QE/g berat kering), yang berpotensi bertindak sebagai agen penurun dan penstabil utama dalam proses sintesis. Pencirian fizikokimia mengesahkan bahawa nanopartikel Ag terdekorasi pada permukaan TiO₂ tanpa perubahan pada struktur kekisi, seperti yang dibuktikan melalui analisis XRD, FESEM, TEM dan XPS. Selain itu, analisis UV-DRS menunjukkan bahawa penggabungan Ag telah menyebabkan pengurangan yang ketara dalam tenaga jurang jalur dengan 50-Ag/TiO₂ mencatatkan nilai jurang jalur terendah iaitu 2.09 eV. Pengurangan ini disertai oleh peningkatan penyerapan dalam kawasan cahaya nampak, yang boleh dikaitkan dengan kesan resonans plasmon permukaan (SPR) nanozarah Ag. Ag/TiO₂ menunjukkan peningkatan ketara dalam aktiviti fotomangkin terhadap penyingkiran ciprofloksacin (CIP) sebanyak 91% bagi 50-Ag/TiO₂ di bawah cahaya nampak, yang dikaitkan dengan pemisahan pembawa cas yang cekap. Ujian pemerangkap radikal dan kebolehgunaan semula mengesahkan peranan dominan radikal •O₂^- serta kestabilan fotomangkin tersebut. Mekanisme degradasi fotomangkin yang munasabah telah dicadangkan berdasarkan keputusan uji kaji. Kajian ini menunjukkan satu strategi mampan dalam pembangunan fotomangkin plasmonik dengan aktiviti fotomangkin cahaya nampak yang dipertingkatkan untuk penyingkiran bahan pencemar.

Kata kunci: Ag/TiO₂; biosintesis; ciprofloksacin; degradasi antibiotik; fotomangkin; resonans plasmon permukaan

 

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