Fluorogenic Reaction Probes Defect Sites on Titanium Dioxide Nanoparticles

• Published in: ChemNanoMat : chemistry of nanomaterials for energy, biology and more Vol. 10; no. 7
• Main Authors: Zuo, Li, Hossain, Mohammad Akter, Dubadi, Rabindra, Kist, Madelyn M., Farhana, Fatiha, Chen, Jiao, Jaroniec, Mietek, Shen, Hao
• Format: Journal Article
• Language: English
• Published: 01.07.2024
• Subjects: chemical oxidation; defect site; fluorogenic probe; single-molecule catalysis; titanium dioxide
• ISSN: 2199-692X; 2199-692X
• DOI: 10.1002/cnma.202400031

Titanium dioxide nanoparticles (TiO2 NPs) have traditionally been utilized as industrial catalysts, finding widespread application in various chemical processes due to their exceptional stability and minimal toxicity. However, quantitatively assessing the reactive sites on TiO2 NPs remains a challenge. In this study, we employed a fluorogenic reaction to probe the apparent reactivity of TiO2 NPs. By manipulating the number of defect sites through control of hydrolysis speed and annealing temperature, we determined that the Ti(III) content is positively correlated with the reactivity of TiO2 NPs. Additionally, these Ti(III) sites could be introduced by reducing commercial TiO2 NPs using NaBH4. Our findings suggest that fluorogenic oxidation of Amplex Red is an effective method for probing defect site densities on TiO2 NPs. Utilizing single‐molecule fluorescence imaging, we demonstrated the ability to map defect site density within TiO2 nanowires. Achieving sub‐nanoparticle spatial resolution, we observed significant intraparticle and interparticle variations in the defect site distribution, leading to substantial reactivity heterogeneity. Defect site‐rich titanium dioxide promotes the activation of hydrogen peroxide generating more reactive oxidative species and exhibits outstanding advantages on chemical oxidation. The cycle of Ti(III) and Ti(IV) plays an important role in the catalytic enhancement. More importantly, single‐molecule catalysis has great potential to avoid the heterogeneity of nanocatalysts and probe the defect site distributions.