Revealing the dual role of nanoparticle size and surface ligands in plasmon-enhanced photocatalysis of Au/TiO₂ nanorods

Slapničar, Špela (author), Caf, Maja (author), Kralj, Slavko (author), Žerjav, Gregor (author), Pintar, Albin (author)

The development of plasmon-enhanced TiO$_2$ photocatalysts offers exciting opportunities for the use of visible light in environmental and energy-related applications. A key parameter that determines their performance is the size and distribution of the plasmonic metal nanoparticles (NPs), which strongly influence charge separation, light absorption and interfacial chemistry. In this work, we have systematically investigated the role of Au NPs size on the structural, electronic and photocatalytic properties of hydrothermally synthesized TiO$_2$ nanorods (TNR). Au NPs with well-controlled diameters in the range of 10–50 nm were uniformly deposited on the TNR surfaces, which was confirmed by electron microscopy and elemental mapping. UV–Vis diffuse reflectance spectra confirmed the absorption of localized surface plasmon resonance (LSPR) in the visible region, with peak positions depending on both the size of the NPs and the presence of Na-citrate residues from the synthesis. Supplementary spectroscopic analyses showed that citrate residues altered the surface chemistry, impaired charge transfer and partially blocked active sites. Photoluminescence and time-correlated single photon counting measurements revealed that Au decoration effectively suppressed the recombination of electrons and holes and prolonged the lifetime of charge carriers, while electron paramagnetic resonance spectroscopy showed improved stabilization of Ti$^{3+}$ centers and oxygen vacancies upon visible-light irradiation. Photocatalytic tests, evaluated by the generation of reactive oxygen species and the degradation of bisphenol A (BPA), showed that the activity increased with decreasing NPs size. The sample with the smallest Au NPs showed the highest reactivity and achieved a BPA degradation of ∼40 within 4 h. Thus, it clearly outperformed both the larger Au-decorated TNR and the untreated TNR reference sample. Nevertheless, residual citrate limited the overall efficiency by hindering charge transport and surface reactivity. These findings provide a pathway for the rational design of more efficient plasmonic photocatalysts by controlling NP size and removing synthesis by-products.

• Language: English
• Keywords: heterogeneous photocatalysis, titanate nanorods, gold NPs, wet impregnation, localized surface plasmon resonance effect
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FFA - Faculty of Pharmacy
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 14 str.
• Numbering: Vol. 720, pt. C, art. 165300
• PID: 20.500.12556/RUL-182823
• UDC: 66
• ISSN on article: 1873-5584
• DOI: 10.1016/j.apsusc.2025.165300
• COBISS.SI-ID: 261044227
• Publication date in RUL: 25.05.2026

Record is a part of a journal

• Title: Applied surface science
• Publisher: Elsevier
• ISSN: 1873-5584
• COBISS.SI-ID: 22979333

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: kemijska tehnologija, titanov dioksid, fotokatalizatorji, vidna svetloba