English

• TiO₂ plays a crucial role in the production of white pigments and the formulations of sunscreen, with large-scale manufacturing occurring globally [1,2]. Over the past few decades, TiO₂ has had a significant impact on environmental management and industrial applications due to its straightforward fabrication, affordability, non-toxic nature, consistent performance, and a large band gap energy [3,4]. The phase transition of TiO₂ is utilized to enhance its environmental management applications by improving its activity under visible light and increasing its degradation capacity for organic pollutants [5]. This includes the elimination of pesticide and fertilizer residues from wastewater, as well as the elimination of volatile organic pollutants from the atmosphere [6]. In industrial applications, controlling the crystal phase and structure of TiO₂ can optimize its performance in coatings, cosmetics, and photovoltaic cells [7]. For instance, the rutile phase, known for its high refractive index and excellent covering power, is commonly used in the coatings and plastics industries. Currently, TiO₂ is found in three forms: anatase, rutile and limonite. Among these, anatase TiO₂ is favored in photocatalytic applications because of its high-density localized states [8]. Although rutile demonstrates enhanced stability, density, dielectric properties, and oxygen adsorption in comparison to anatase, it tends to have reduced electron mobility [9]. Taking into account the unique benefits provided by both anatase and rutile, it is common to consider phase junction of TiO₂ as having superior photocatalytic properties, a trait attributed to the formation of heterogeneous junctions [9,10].

  In the phase transition of TiO₂, various techniques are routinely utilized, including rapid thermal annealing treatments [11,12], in situ chemical reactions [13,14], and magnetron sputtering [15]. The process of rapid thermal annealing is achieved by calcining hydrolyzed titanium isopropoxide on commercial rutile particles [16]. In situ chemical synthesis is facilitated through electrolytic oxidation or the addition of organic reagents and anions to the synthesis precursor [17]. When utilizing direct current reactive magnetron sputtering, TiO₂ thin films deposited under a free negative bias demonstrate a pure anatase phase. Nevertheless, an increase in the negative bias voltage results in the emergence of additional rutile phases, yielding a composite of anatase and rutile [18]. In spite of notable advancements in the fabrication of TiO₂ phase transition materials that show improved photocatalytic activity, finding a simpler and more efficient method for synthesizing phase transition TiO₂ in adjustable proportions continues to be a challenge.

  In this study, the successful synthesis of anatase/rutile TiO₂ featuring heterogeneous linkages has been successfully achieved through a short-duration calcination process utilizing laser technology. The tunable characteristic arises from the photothermal effect produced by TiC, which promotes the transformation of TiC into TiO₂ to form nuclear decomposition, thereby facilitates the transformation of anatase into rutile at higher temperatures. Simultaneously, the increase in temperature causes the surrounding anatase grains to agglomerate layer-by-layer manner, thereby facilitating the phase transition from anatase to rutile. Moreover, the use of the phase junction of TiO₂ for the photocatalytic degradation of various aqueous pollutants, including TC–HCl and MB, has demonstrated better catalytic performance and effective pollutant degradation. The experimental results indicated that the photocatalytic performance was optimal when the laser ablation is 3 s, yielding a composition of 80% anatase and 20% rutile. This specific ratio corresponds to the known composition of commercial P25-TiO₂ (80% anatase and 20% rutile), often considered a standard model photocatalyst due to its superior photocatalytic activity [19]. Additionally, the performance of the mixed phase in photocatalysis exceeds that of either pure anatase or rutile, considerably boosting its degradation efficiency. This enhancement plays a vital role in improving water quality and minimizing environmental pollution.

  The microscale phase transformation of the composite material during laser ablation is illustrated in Fig. 1. When subjected to laser irradiation at a wavelength of 808 nm and a power of 1.5 W, the TiC component of the composite material absorb NIR light, converting it into heat energy. This heat facilitates the transformation of the anatase phase into the rutile phase under high temperature [20]. As shown in Fig. 1a as the laser light is continuously applied, heat accumulates, causing neighboring anatase grains to agglomerate under high temperature. Consequently, the phase transformation occurs in a layer-by-layer manner, establishing a diffusive phase transformation mode with TiC acting as the core. This process ultimately led to the formation of the phase junction structure comprising both anatase and rutile. The fabrication methods for the TiO₂ and TiC composites are detailed in Supporting information Fig. S1 (Supporting information).

  Figure 1

  

  Figure 1.  (a) Schematic diagram of the phase transition from laser ablated anatase to rutile. (b, c) Infrared thermography images, the insets show pure anatase powder (white) and anatase/TiC composites (black), respectively. (d, e) TGA of the material without ablation and with laser ablation for 3 s. (f) High-speed video camera capturing the dynamics of the laser ablated composite material.

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  Anatase TiO₂ in its pure form did not successfully undergo the laser ablation process when subjected to laser irradiation, with a recorded temperature of 41.5 ℃ as measured by an infrared thermal imager, as depicted in Fig. 1b. In contrast, when a small quantity of TiC is added and the material is ground adequately, laser ablation can be executed almost instantly, at which moment temperatures can soar to 580 ℃, as illustrated in Fig. 1c. The photothermal conversion efficiency of this process is 70%, and the calculation process can be found in the Supporting information section and Fig. S2 (Supporting information) on photothermal conversion efficiency. The literature indicates that the temperature ranges for the phase transition from anatase TiO₂ to rutile spans 528–805 ℃. This suggests that during the laser ablation of composite materials containing TiC, the anatase form achieves the necessary critical temperature for transformation to rutile [21]. As shown in Fig. 1d, thermogravimetric analysis (TGA) was performed on the untreated material (the composites after 0 s of laser ablation). This analysis revealed that prior to 420 ℃, the loss of mass in the untreated material was mainly due to the evaporation and desorption of liquid water along with water of crystallization [22]. When temperatures surpassed 420 ℃, a rise in mass was noted, attributed to the conversion of TiC to the anatase phase, ultimately leading to the emergence of the rutile phase. This finding corroborates literature evidence suggesting that subjecting TiC powder to oxidative milling at 400 ℃ for a period ranging from 24 h to 50 h results in the formation of anatase TiO₂ [23]. The TGA of the material subjected to laser ablation for 3 s is presented in Fig. 1e, indicating that the mass remained unchanged throughout the procedure, signifying that TiC had entirely transitioned to TiO₂. Fig. 1f captures the microscopic dynamics of laser ablation as recorded by a high-speed camera. The sample's volume gradually reduces from (Ⅰ) to (Ⅳ), with the complete process concluding within 0.75 s, accompanied by thermal agglomeration. During pulsed laser ablation, the surface clustering of nanoscale anatase particles can lead to the formation of faults and twins, which create preferential sites for the nucleation of the rutile phase, thereby facilitating its formation.

  The morphology of the composites after 0, 3 and 6 s of laser treatment was observed using scanning electron microscope (SEM). The sample without laser ablation, depicted in Fig. 2a primarily consists of small round particles of anatase and TiC. In contrast, Figs. 2b and c illustrate that the samples subjected to 3 and 6 s of laser ablation show a gradual increase in particle size, accompanied by smaller particles dispersed throughout. SEM observations indicate that the process of melt remodeling occurs in the composites due to the influence of high temperature. The high-resolution transmission electron microscopy (HRTEM) images shown in Fig. 2d demonstrate grain spacing of 0.319 and 0.351 nm, corresponding to the (110) grain surface of rutile and the (101) grain surface of anatase, respectively. These finding confirm the formation of a tight interface between rutile and anatase, suggesting the generation of heterojunctions.

  Figure 2

  

  Figure 2.  (a-c) SEM without laser ablation (anatase), laser ablation for 3 s and 6 s (mixed phase) in order. (d) HRTEM with laser ablation for 3 s. (e-h) XPS with laser ablation for 3 s: survey (e), C 1s (f), Ti 2p (g) and O 1s (h).

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  The X-ray photoelectron spectroscopy (XPS) measurement spectra of the laser-ablated 3 s material are shown in Fig. 2e, displaying distinct peaks for O 1s, Ti 2p, and C 1s. The C 1s spectrum (Fig. 2f) typically exhibits three carbon contribution peaks at 288.9, 286.3, and 284.8 eV, corresponding to C=O, C—O, and C—C bonds, respectively [24]. Among these, the peak at 284.8 eV predominantly represents C—C, primarily arising from the reference carbon on the sample surface. The Ti 2p XPS spectra (Fig. 2g) are resolved into two peaks, Ti 2p_1/2 and Ti 2p_3/2, located at 464.1 and 458.2 eV, respectively, indicating the presence of Ti⁴⁺ in amorphous, anatase phase, and rutile phase TiO₂ [25,26]. The O 1s spectrum(Fig. 2h) reveals three peaks at 533, 531.5, and 529.5 eV, attributed to lattice oxygen, O—H bonds, and Ti-O bonds, respectively [27]. Meanwhile, the peak at 531.5 eV is associated with the chemisorption of oxygen vacancies, suggesting a higher prevalence of oxygen vacancies in phase junction samples [28]. The Ti-O bond at 529.5 eV in the material laser-ablated for 3 s is attributed to rutile TiO₂ [29,30]. Collectively, the XPS results indicate that the material laser-ablated for 3 s is a mixed phase containing both anatase and rutile.

  The X-ray diffraction (XRD) patterns of all samples at different laser ablation times are shown in Fig. 3a. When the laser ablation duration was 1s, the rutile peak started to appear, concurrently with a gradual reduction in the intensity of the main peak of anatase. With the increase of laser ablation time, the transformation from anatase to rutile was observed, which was accompanied by the reconstruction of the polycrystalline material stemming from the assembly of atoms and extensive reorganization of granular bonds [31]. As a result, the phase transformation process induced by different irradiation durations is illustrated in Eq. 1.

  Anatase→anatase/rutile→rutile

  (1)

  Figure 3

  

  Figure 3.  (a) Material with laser ablation 0–6 s in order from bottom to top. (b) Ratio of anatase to rutile after laser ablation.

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  Fig. 3 illustrates the XRD patterns of anatase/rutile TiO₂ composites synthesized by laser ablation for periods varying from 0 s to 6 s. Notably, the XRD patterns for TiO₂ synthesized between 0 s and 6 s exhibit a consistent form of diffraction peaks, which can be attributed to the tetragonal anatase phase (JCPDS No. 21–1272, space group I4₁/amd) and the tetragonal rutile phase (JCPDS No. 21–1276, space group P4₂/mnm) [31]. Specifically, the diffraction peaks at 2θ = 25.4°, 37.84°, and 48.04° are attributed to the (101), (004), and (200) crystal planes of anatase TiO₂, respectively. In contrast, the peaks observed at 2θ = 27.68°, 36.12°, 41.72°, and 54.1° correspond to the (110), (101), (111), and (211) diffraction peaks of rutile TiO₂. The relative proportions of anatase and rutile in the TiO₂ composites following 0–6 s of laser ablation can be calculated using Eqs. 2 and 3 [32].

  WA=0.886IA0.886IA+IR

  (2)

  WR=IR0.886IA+IR

  (3)

  In the equation, WA and WR represent the mass fractions of anatase TiO₂ and rutile TiO₂, respectively. The integral intensities related to the crystal surfaces of anatase TiO₂ (101) and rutile TiO₂ (110) are denoted by IA and IR, correspondingly. The ratios of the integrated intensities associated with the diffraction peaks from the anatase TiO₂ (101) crystal surface versus those from the rutile TiO₂ (110) crystal surface within the composites are illustrated in Fig. 3b. The XRD analyses indicate that the phase transition process from anatase to rutile in the anatase/TiC composites can be effectively controlled by adjusting the duration of laser ablation.

  Fig. 4a illustrates that Raman spectroscopy serves as an effective tool for distinguishing different crystalline phases of TiO₂ [33]. In the absence of laser ablation effects, the Raman spectrum of anatase exhibits diffraction peaks at 388, 505, and 625 cm^-1, indicative of three active Raman modes: B_1g, A_1g/B_1g, and E_g, respectively. In contrast, following complete laser ablation, which leads to a light gray appearance, the observed diffraction peaks shift to 425 and 602 cm^-1, corresponding to the two active Raman modes: E_g and A_1g, respectively [34,35].

  Figure 4

  

  Figure 4.  Raman characteristic (a) peaks of pure anatase and pure rutile. (b) peaks of laser ablation for 0–6 s in order from top to bottom.

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  The analysis of Raman spectra collected over a range of laser ablation times, it was observed that the spectral features transition from the anatase phase to the rutile phase [36] with increasing laser ablation duration, as illustrated in Fig. 4b. Notably, after 1s of light treatment, no vibrational modes were detected in the Raman spectra, signaling the emergence of an amorphous phase. When the duration of light exposure was increased to 2 s, the Raman characteristics began to blend with the remaining photoluminescence background. With an additional increase in laser ablation time, the transition from anatase to rutile was progressively characterized, leading to the vanishing of the photoluminescence phenomenon. Concurrently, the Raman peaks at 425 and 602 cm^-1 became increasingly pronounced, signifying the formation of the rutile phase. After a cumulative ablation time of 3 s, the amorphous structure was replaced by the rutile phase, and modifications in the Raman spectra were progressively noted. It is significant to mention that the transition to the rutile phase was tracked via laser beam ablation. These results strongly suggest that the rutile phase does not formed during irradiation, but rather as a consequence of the irradiation [20,37].

  Tetracyclines, such as TC–HCl, are widely used antibiotics that can lead to increased antibiotic resistance in the environment [38,39], posing a long-term threat to ecosystems and human health due to their persistence [30,39,40]. Dyes used in the textile industry, like MB, are harmful to aquatic ecosystems, with approximately 70% remaining in wastewater, potentially carcinogenic, highlighting the urgency of developing effective water treatment technologies to remove these pollutants [41,42]. The introduction of phase change materials for TiO₂ photocatalysts provides significant advantages, adjusting the electronic structure and light absorption characteristics of TiO₂, optimizing the light response range and band structure, thereby improving photocatalytic efficiency [43-45]. Moreover, the incorporation of phase change materials enhances light absorption efficiency and carrier separation efficiency, significantly improving the stability and applicability of photocatalysts, which is crucial for the efficient treatment of organic pollutants in real-world environments [46,47]. Therefore, photocatalytic technology using TiO₂ phase change materials can more effectively degrade harmful pollutants in water bodies, such as TC–HCl and MB [48-50]. This technology significantly improves photocatalytic efficiency through the phase change process and enhances the stability and applicability of photocatalysts, offering an efficient and sustainable solution for the treatment of organic pollutants under complex and changing environmental conditions.

  The efficiency of photocatalytic degradation TC–HCl and MB was explored using various anatase to rutile ratios in anatase/TiC composites that were crafted through laser ablation for time intervals between 0 s and 6 s. As illustrated in Fig. 5a, the catalytic efficiency (C_t/C₀) of the composite material for degrading TC–HCl under visible light is measured at 0.73, 0.67, 0.57, 0.48, 0.66, 0.69, and 0.70, respectively. These results indicate that the sample subjected to 3 s of laser ablation demonstrated superior photocatalytic activity in comparison to other photocatalysts over the course of 150 min of degradation. The degradation process conforms to the first-order kinetic model, as depicted in Fig. 5b, with the calculated photodegradation rate constants [51] for TC–HCl determined from the linear relationship between -Ln(C₀/C_t) and time being 0.0016, 0.00264, 0.00383, 0.00497, 0.00293, 0.00226, and 0.00195 min^-1. The experimental results suggest that at a laser ablation duration of 3 s, the ratio of anatase to rutile is approximately 4:1, which is similar to the photocatalytic performance of the widely recognized benchmark model photocatalyst, P25-TiO₂ (comprising 80% anatase and 20% rutile) [52,53]. Fig. 5c demonstrates the performance of samples treated for 3 s through laser ablation in the photocatalytic degradation of TC–HCl, confirming a steady reduction in TC–HCl concentration with increasing light exposure time. The degradation curves and -Ln(C₀/C_t) degradation rate for MB, along with the photocatalytic degradation results for the specimens treated for 3 s of laser ablation, can be found in Figs. 5d-f, respectively. The outcomes of the degradation studies for TC–HCl and MB indicate that the phase junction catalyst with a ratio of anatase to rutile of 4:1 exhibited enhanced photocatalytic performance and successfully degraded both the antibiotic TC–HCl and the dye MB.

  Figure 5

  

  Figure 5.  Photodegradation effect, primary kinetics and photocatalytic degradation by laser ablation over time for 3 s: (a-c) TC–HCl, (d-f) MB.

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  Fig. 6a illustrates the relationship between catalyst content and photocatalytic efficiency. As the concentration of the catalyst rises, the photocatalytic efficiency similarly increases, reaching its peaking at 20 mg. This is attributed to the fact that an optimal amount of catalyst enhances the interaction between photons and photosensitive semiconductors, thereby increasing the generation of active species and accelerating the photocatalytic reaction [40]. However, too much catalyst may lead to heightened turbidity in the solution, which reduces light transmittance and consequently inhibits photocatalytic efficiency [54]. At the same time, the impact of pollutant concentration on photocatalytic activity is being investigated. With a catalyst content of 20 mg, the photocatalytic performance of TC–HCl solutions at concentrations ranging from 10 mg/L to 30 mg/L analyzed. Findings indicate that the catalyst achieves maximum catalytic performance at a TC–HCl concentration of 20 mg/L, as demonstrated in Fig. 6b. Since the generation of the mixed phase is directly influenced by laser intensity, we analyzed the effect of the mixed phase produced under different intensities of laser irradiation on photocatalytic performance, identifying an optimal laser power of 1.5 W, as shown in Fig. S3 (Supporting information).

  Figure 6

  

  Figure 6.  Influenced factors at different catalyst contents (a), different pollutant concentrations (b). (c) Effect of free radical scavengers on IC dye destruction. (d) Reusability of catalysts. (e) Mechanism of photodegradation.

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  During the process of photocatalytic degradation, a series of capture experiments were conducted to identify the active substances, with findings illustrated in Fig. 6c. Scavengers, including 15 mmol/L isopropanol (IPA), ascorbic acid (LA), ammonium oxalate (AO) and dimethyl sulfoxide (DMSO) [55] were selected to target hydroxyl radicals (^•OH), ^•O₂^-, h⁺ and electrons (e^-), respectively [56]. The findings indicated a general decline in the degradation rate of TC–HCl upon the addition of these scavengers, confirming the involvement of these active species in the photodegradation process. Notably, IPA and DMSO demonstrated a negligible effect on the photodegradation of TC–HCl, implying that ^•OH and e^- have a limited influence in this context. In contrast, the degradation rate of TC–HCl significantly diminished when h⁺ and ^•O₂^- were scavenged using LA and AO, respectively, suggesting that h⁺ and ^•O₂^- are essential active species for the degradation of TC–HCl within the phase junction catalysts, which are crucial for facilitating the photocatalytic degradation reaction. Fig. 6d illustrates that the photocatalytic structure of anatase/rutile TiO₂ demonstrates good stability, maintaining 83% of the initial degradation efficiency of TC–HCl after five cycles of use.

  The laser-ablated composites demonstrated improved absorption properties in the visible region [30], a phenomenon likely attributed to the formation of the anatase/rutile hybrid structure. As illustrated in Fig. S4 (Supporting information), the band gaps of the samples subjected to laser ablation for durations of 0, 3, and 6 s were recorded at 3.17, 3.08, and 3.54 eV, respectively. Notably, the samples ablated for 3 s exhibited reduced band gaps, which promote electron transitions from the valence band to the conduction band, thus enhancing their conductivity [48]. The results from the photocurrent density tests of the modified electrodes [40] showed that the 3 s ablated samples achieved higher photocurrent conversion efficiency, as shown in Fig. S5a (Supporting information). In addition, the internal resistance and interfacial electron transfer capabilities of the samples were validated by electrochemical impedance spectroscopy (EIS) measurements [57], depicted in Fig. S5b (Supporting information). The electrodes modified with the 3 s laser ablated exhibited smaller diameters of the semicircular arcs, signifying a decrease in internal resistance and enhanced interfacial electron transfer efficiency.

  Under photoexcitation conditions, the transfer of electrons from rutile to anatase effectively inhibits charge recombination and promotes the efficient separation of electron-hole pairs, thus enhancing photocatalytic activity [58]. The excellent oxygen adsorption capacity of rutile, combined with the high-density localized states of anatase, facilitates the generation of ^•O₂^- and h⁺, respectively. As shown in Fig. 6e, electrons are captured during the reduction of O₂ to produce ^•O₂^-, while the valence band of rutile undergoes an oxidation reaction, resulting in the generation of a substantial number of h⁺ [30,55]. Usually, ^•O₂^- and h⁺ serve as the primary active species in the photocatalytic degradation of pollutants. Therefore, these active species are crucial for the effective mineralization of pollutants during the photocatalytic degradation of TC–HCl and MB.

  In this study, we achieved efficient and tunable proportional phase transformation of TiO₂ from anatase to rutile through near-infrared laser ablation of nanoanatase and TiC. By precisely controlling the exposure time to NIR light, we can adjust the conversion ratio of anatase to rutile. Under the high temperatures generated by the laser, TiC acts as a photothermal core, reacting with oxygen in the air to produce TiO₂ and carbon dioxide. Simultaneously, this elevated temperature promotes the layer-by-layer phase transformation of adjacent anatase to rutile, thereby enabling precise control over the TiO₂ phase structure. This controllable phase change strategy not only enhances the separation efficiency of photogenerated charge carriers but also improves the photocatalytic activity of TiO₂. Experimental results indicate that the TiO₂ sample processed by laser sintering for 3 s exhibits optimal photocatalytic performance, with a weight ratio of rutile to anatase of approximately 0.2 to 0.8. This specific phase change ratio significantly improves the degradation efficiency of organic pollutants such as TC–HCl and MB. In addition, the constructed TiO₂ heterojunction structure increases the oxygen adsorption capacity and increases the local state density, effectively promoting the generation of ^•O₂^- and h⁺. This discovery offers new insights for the design of photocatalytic materials, paving the way for advancements in environmental pollution control and water purification technologies, and holds significant environmental and social benefits.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  CRediT authorship contribution statement

  Hongping Zhao: Writing – original draft, Methodology, Investigation, Data curation, Conceptualization. Hanzhaobing Wu: Methodology, Investigation, Data curation. Baolong Shi: Investigation, Data curation. Jiayue Wang: Investigation. Chunzheng Wu: Investigation. Chaohai Wang: Investigation. Xiaoyan Wang: Writing – review & editing, Investigation. Wei Liu: Writing – review & editing, Supervision, Investigation, Data curation. Chaoqing Dai: Writing – review & editing, Investigation. Dalei Wang: Writing – review & editing, Supervision, Investigation, Data curation.

  Acknowledgments

  This research was supported by Zhejiang Provincial Natural Science Foundation of China (No. LTGC23C160002), Zhejiang Provincial Academy Cooperation Forestry Science and Technology Project (No. 2023SY14), the Zhejiang Provincial Natural Science Foundation of China (No. LR20A050001), Scientific Research Project of Education Department of Hunan Province (No. 22A0560), General Project of Zhejiang Provincial Department of Education (No. Y202147215), the National Natural Science Foundation of China (Nos. 12275240, 12075210), Zhejiang Provincial Public Welfare Technology and Application Research Project (No. GN21B020001), the Scientific Research and Developed Fund of Zhejiang A&F University (Nos. 2021FR0009, 2022LFR042), Scientific Research Foundation of Zhejiang A&F University (No. 2023CFR136) and the 2024 Open Fund for Henan Key Laboratory of Water Pollution Control and Rehabilitation Technology (No. CJSZ2024012).

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2025.110815.

  
  
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  Figure 1  (a) Schematic diagram of the phase transition from laser ablated anatase to rutile. (b, c) Infrared thermography images, the insets show pure anatase powder (white) and anatase/TiC composites (black), respectively. (d, e) TGA of the material without ablation and with laser ablation for 3 s. (f) High-speed video camera capturing the dynamics of the laser ablated composite material.

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  Figure 2  (a-c) SEM without laser ablation (anatase), laser ablation for 3 s and 6 s (mixed phase) in order. (d) HRTEM with laser ablation for 3 s. (e-h) XPS with laser ablation for 3 s: survey (e), C 1s (f), Ti 2p (g) and O 1s (h).

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  Figure 3  (a) Material with laser ablation 0–6 s in order from bottom to top. (b) Ratio of anatase to rutile after laser ablation.

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  Figure 4  Raman characteristic (a) peaks of pure anatase and pure rutile. (b) peaks of laser ablation for 0–6 s in order from top to bottom.

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  Figure 5  Photodegradation effect, primary kinetics and photocatalytic degradation by laser ablation over time for 3 s: (a-c) TC–HCl, (d-f) MB.

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  Figure 6  Influenced factors at different catalyst contents (a), different pollutant concentrations (b). (c) Effect of free radical scavengers on IC dye destruction. (d) Reusability of catalysts. (e) Mechanism of photodegradation.

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