Titanium dioxide (TiO₂) is a commonly used semiconductor photocatalytic material in organic wastewater treatment. Traditional chemical synthesis methods (such as the sol-gel method) suffer from problems including particle agglomeration, residual impurities, and secondary pollution, which restrict the improvement of its performance. As a green physical preparation technique, pulsed laser ablation (PLA) has the advantages of requiring no chemical reagents and yielding high-purity products. However, existing studies lack systematic exploration in medium selection and pulse number regulation, making it difficult to precisely prepare high-performance TiO₂. To address this issue, this study focuses on optimizing the core parameters of laser ablation, aiming to clarify the intrinsic mechanism of the effects of environmental media and cumulative laser pulses on the formation of TiO₂ nanoparticles, and to achieve their efficient synthesis.

Titanium plates with a purity greater than 99.6% were used as the target material, and experiments were carried out using a nanosecond Nd:YAG laser. Firstly, the effects of three media (air, deionized water, and anhydrous ethanol) were compared. After deionized water was determined as the preferred medium, the regulating effects of 10, 20, and 30 pulses on particle nucleation and growth were further explored. The structural and performance characteristics of the particles were characterized using FE-SEM, EDS, and XRD. The catalytic performance was evaluated by methylene blue (MB) degradation experiments under ultraviolet light, and COMSOL simulation was employed to analyze the mechanical stress and temperature changes of the target material.

Experimental results showed that deionized water had the optimal ablation effect. The products were mainly spherical particles, which were superior to those obtained in air and anhydrous ethanol in terms of yield, morphological regularity, and size distribution (Fig.3). Among the laser pulse numbers, 20 pulses was the optimal parameter. Under this condition, the particles were regularly spherical, with the highest proportion in the 70 nm~120 nm range, with no obvious agglomeration, and with a yield significantly higher than that at 10 pulses, while avoiding the particle agglomeration problem observed at 30 pulses (Fig.4, Fig.5). FE-SEM and EDS characterization revealed that its surface was rich in hydroxyl groups and exhibited good dispersibility (Fig.6, Fig.7).XRD analysis indicated that TiO₂ prepared by the PLA method was mainly composed of the rutile phase, with a narrowed band gap of approximately 2.9 eV (Fig.8, Fig.9). In the MB degradation experiment, the TiO2 achieved a degradation rate of 75% within 30 minutes, and its initial reaction rate was superior to that of the sample prepared by the sol-gel method (Fig.10). COMSOL simulation revealed that the peak shock wave pressure in deionized water was higher than in the other media, and a single pulse could raise the target temperature to about 2100 K, exceeding the melting point of titanium (Fig.12, Fig.13).

This study identifies “deionized water medium + 20 laser pulses” as the optimal process. TiO₂ prepared under these conditions possesses both excellent structural properties and catalytic performance. The constructed “medium-pulse number” synergistic optimization system provides an effective pathway for the green and precise synthesis of high-performance TiO₂.