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Article

Photocatalytic Degradation of Ant Trail Pheromones by P25 TiO2

by
Kata Saszet
1,2,
Eszter Mátyás
3,
Eszter Enikő Almási
4,
Laura Vivien Lakatos
5,
Zsolt Czekes
2,3,
Zsolt Pap
3,5,6,* and
Lucian Baia
1,2,6,*
1
Faculty of Physics, Babeș-Bolyai University, M. Kogălniceanu St. 1, RO-400084 Cluj-Napoca, Romania
2
Nanostructured Materials and Bio-Nano-Interfaces Center, Interdisciplinary Research Institute on Bio-Nano-Sciences, Babeș-Bolyai University, Treboniu Laurian St. 42, RO-400271 Cluj-Napoca, Romania
3
Hungarian Department of Biology and Ecology, Babeș-Bolyai University, Republicii St. 44, RO-400015 Cluj-Napoca, Romania
4
Department of Geology, University of Szeged, Egyetem Str. 2, H-6722 Szeged, Hungary
5
Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla Sqr. 1, H-6720 Szeged, Hungary
6
Laboratory for Advanced Materials and Applied Technologies, Institute of Research-Development-Innovation in Applied Natural Sciences, Babeș-Bolyai University, Fântânele St. 30, RO-400327 Cluj-Napoca, Romania
*
Authors to whom correspondence should be addressed.
Catalysts 2025, 15(11), 1040; https://doi.org/10.3390/catal15111040
Submission received: 14 August 2025 / Revised: 13 October 2025 / Accepted: 21 October 2025 / Published: 2 November 2025
(This article belongs to the Special Issue 15th Anniversary of Catalysts—Recent Advances in Photocatalysis)
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Abstract

Titanium dioxide nanostructures are extensively produced and utilized in various industries. Concerns have been raised about this material’s less researched environmental impact. This study investigates the indirect toxicity of TiO2 nanoparticles (NPs) on ant communication via the photocatalytic degradation of ant trail pheromones. Foraging experiments with Lasius niger demonstrated that TiO2-treated pathways were avoided by ants, suggesting trail pheromone degradation. Photocatalytic tests confirmed the degradation of the pheromone component (R)-(-)-mellein under UV-A irradiation in the presence of Evonik Aeroxide P25 TiO2. The nanosized titania was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). These findings indicate that TiO2 NPs can disrupt ant communication, potentially leading to significant ecological consequences.

Graphical Abstract

1. Introduction

Titanium dioxide nanostructures have the highest production rate among engineered nanomaterials (ENMs): based on data available from 2012 [1], annually 10,000 metric tons of TiO2 NP were produced worldwide, a number estimated to reach 2.5 million metric tons by 2025 [2]. Other estimations suggest that this production rate can grow even further, to 14 million metric tons/year [3]. The latter information points out that nanosized titania will become the most dominant product of the nano industry by 2025. Its popularity is based on its possible wide range of use in various industries such as healthcare [4], pharmaceutical [5], food [6], cosmetics [7], electronics [8], paints and coatings [9], catalysis [10], and photocatalysis [11].
Although several attempts exist for the regeneration and recycling of TiO2 NP, at the end of its life cycle (in the absence of proper waste management), it could end up in our environment, if not even earlier, incidentally during handling and usage. Data regarding the accumulation of nanoparticulate titania in the environment is scarce. Still, a simulation performed in 2008 [12] showed that, in Europe, in the period 2008–2012, the concentration of TiO2 NP increased yearly in soils at a rate of 1.28 μg/kg, in surface waters at 0.015 μg/kg, and in sediments at 358 μg/kg. The same simulation concluded that in this short period of 4 years in the U.S., the concentration of TiO2 NP in sediments increased threefold. Today, it is already known that accurately monitoring and modeling TiO2 NP accumulation in the environment is complex and hard to achieve, but all estimations show increasing trends [13,14].
At this rate of production and environmental accumulation, the demand for research on toxicity of TiO2 has grown, resulting in numerous publications with concerning data. The harmful effects of TiO2 on microorganisms, algae, plants, invertebrates, and vertebrates were widely investigated, and three main types of possible toxicity mechanisms of titania were identified: by reactive oxygen species produced by TiO2, by NP attachment to the cell wall, and by NP attachment to organelles inside the cell [15].
In all these cases, the organism is directly affected by the ENM. However, there is another possible mechanism for the toxicity of TiO2 NPs that has not been considered until now. TiO2, being a highly efficient, non-selective photocatalyst of organic compound degradation, could affect various organisms indirectly, by altering or mineralizing endobiotic molecules.
A large number of insect species use organic compounds as means of communication. Ants are a special group of insects, as they use various chemical cues for communication. They use different visual and olfactory signals and their memory in food foraging processes, but probably one of the most important means of communication is through trail pheromones [16,17,18].
From several bioassay studies, it is already known that pheromones from glandular extracts contain various organic compounds such as alcohols, acetates, aldehydes, ketones, esters, terpenes, and aromatic compounds on the ng scale, and worker ants are very sensitive already to the presence of parts per billion of these chemicals [19].
In contrast with this minuscule amount, the quantities of organic compounds degraded by TiO2 in a matter of minutes are incomparable. For example, Székely I. et al. (2019) [20], through heterogeneous photocatalysis, removed phenol from an aqueous solution (initial concentration of 0.5 mM and total volume of 100 mL) using commercial TiO2 under UV-A irradiation, achieving an efficiency of 86.8%. This means that, in 120 min, approximately 4 mg of phenol was removed in total [20].
At present, there is no study treating the problem of the photocatalytic effect of TiO2 on any kind of pheromone of social insects. In the case of honeybees, only the direct toxic effect of the NP was studied [21,22], while in the case of ants, only one study exists that discusses the oxidative effect of TiO2 NP on endobiotic molecules, namely the cuticular hydrocarbon profile of red wood ants [23]. However, different publications point out that titania can have insecticide effects [24,25], although our investigations until now pointed out that titania caused behavioral disorders, rather than mortality [23].
Ants are considered ecosystem engineers, as they directly and indirectly modify the habitat of other organisms: they change the physical and chemical properties of soils they live in, increasing aeration, drainage, and organic matter content (e.g., seeds, plant tissues, and insect carcasses), and contribute to nutrient cycling and subsequently to plant diversity [26,27,28].
In the light of the above, it is fair to assume that the degradation of any of the pheromone signaling pathway used by ants can alter highly regulated ecosystem processes driven by a shift in the foraging behavior of ants. The present study aims to prove the hypothesis that the presence of nano titania can degrade the trail pheromones, irreversibly influencing the communication of ants.
In the first phase of our study, foraging tests were performed on the species Lasius niger, also known as black garden ant, exposing worker ants to a commercially available and well-known nano titania: Evonik Aeroxide P25.
This ENM was specifically chosen because it is widely used in various industries, has fairly well-known physical–chemical properties, is a highly efficient UV-A active photocatalyst in organic compound degradation, and has been the subject of toxicological research, with various results. During the foraging experiment, ants predominantly chose pathways not treated with P25.
In the second part of the study, to prove that this avoidance is not caused merely by the physical disturbance due to the presence of the nanomaterial, but by the lack of a pheromone trail on the TiO2-treated pathways, the findings of the ecotoxicity tests were supplemented with experiments of photocatalytic degradation. The dihydroisocoumarin called mellein, the main component of Formica rufa trail pheromone, was degraded from an aqueous solution in the presence of P25 under UV-A irradiation.

2. Results and Discussion

2.1. The Basic Properties of Evonik Aeroxide P25

The P25 sample used during the experiments was characterized beforehand, as this commercial TiO2 reportedly shows inhomogeneity both in crystalline composition [29] and primary crystallite mean size [30]. Please note that Evonik Aeroxide P25 is a well-known reference photocatalyst; hence no detailed structural study will be carried out. In the present work, just the confirmation of the well-known structural, optical and morphological parameters was evidenced.
All measured and calculated characteristics presented in the following were found in the range of data offered by the literature. When investigating the crystal structure of P25, the calculations based on XRD measurements confirmed that it is a combination of anatase (72.3%), rutile (17%), and a small amount of amorphous matter (10%) (Figure 1).
The mean primary crystallite size values were calculated according to the Scherrer equation [31]: 24 nm for anatase and 36 nm for rutile. According to transmission electron microscopy measurements, P25 is polycrystalline, with aggregated particles (Figure 1).
The optical properties of the material were also investigated. The bandgap energy values obtained from the Kubelka–Munk transformations of the DRS data were 3.3 and 3.1 eV for anatase and rutile phases, respectively. Translated to wavelength values, this means that the light absorption edge of the anatase component is at 370 nm and the rutile component at 394 nm, which indicates UV-A light-driven activation (Figure 1).
When irradiated TiO2 nanoparticles in aqueous media, in the presence of organic molecules, enter into redox reactions, reactive oxygen species (ROS) hydroxyl radicals (•OH), superoxide anions (•O2−), and hydrogen peroxide (H2O2) are produced. Whether the targeted complex organic molecule is a synthetic pollutant or bioactive matter, it will be broken down by ROS non-selectively into more simple molecules and/or CO2 and H2O [11].

2.2. The Interaction Between the Pheromone Trail and Evonik Aeroxide P25

To observe the natural foraging pattern in our experimental setup, we treated the two branches of the bridge leading to the food source with distilled water for negative control. During this test, as expected, no significant preference occurred for one of the branches in the initial few minutes (Figure 2a). In the later minutes, we observed statistically significant preferences for one of the branches (Figure 2b). The different preference of one of the branches, in this case, is caused by the accumulation of trail pheromones caused by the natural behavior of ants during mass recruitment [32,33].
To control any differences in the foraging pattern of the ant workers caused by TiO2, we have also established an experiment during which both branches were treated with TiO2 suspension (positive control). This test resulted in no difference in the number of ants crossing the two branches (Figure 2c). This result is also expected, as no mass recruitment is possible if the trail pheromones are decomposed by the photocatalytic effect of TiO2.
The experiments meant to test the effect of TiO2 on ant foraging showed a clear difference between the foraging intensity of ant workers in the presence and absence of TiO2. On the branches treated with TiO2, a significant decrease in foraging ant workers was observed from the 3rd minute. This suggests a decomposition of the pathway pheromones deposited by ant workers when returning from the food source (Figure 2a, Table 1).

2.3. Photocatalytic Degradation Experiments of Mellein Pheromone Component

From the performed pheromone-based foraging tests, it can be concluded that the presence of TiO2 on the path of ants influences their behavior (Figure 2). In order to demonstrate that the Lasius niger workers avoid TiO2-treated pathways, because these no longer contain the original trail pheromone left by their peers, it had to be demonstrated that pheromones can be oxidized in the presence of TiO2, under UV-A irradiation. As trail pheromones are complex mixtures of organic compounds, degrading just one component of this mixture would be enough to deactivate the pheromone. In the next step, the commercial version of a single organic compound, which is present in the trail pheromone of ants, was chosen for photocatalytic degradation tests using Evonik Aeroxide P25 Titanium dioxide as the photocatalyst.
According to the literature, the trail pheromone of Lasius niger contains dodecyl acetate, palmitic and oleic acids (all inactive), with the main active component being (R)-3,4-dihydro-8-hydroxy-3,5,7-trimethylisocoumarin (Figure 3a) [19]. This compound is commercially unavailable, and it is extremely difficult to synthesize with high yield and appropriate purity. Thus, (R)-(-)-3,4-Dihydro-8-hydroxy-3-methylisocoumarin, commonly called (R)-(-)-mellein, was chosen as a replacement (Figure 3b). The latter is the component of the trail pheromone of Formica rufa, an ant species from the same subfamily as Lasius niger. From the point of view of the chemical structure, both are 3,4-dihydro-8-hydroxy-isocoumarins, the only difference being the presence of two additional methyl groups in the molecule of L. niger pheromone—instead of a phenol ring, it has xylenol in its structure.
The concentration of the aqueous mellein solution used for the following experiments was defined as being high enough to be measured spectrophotometrically but maintained at a lower concentration of 10 mM (i.e., 213.84 mg in 120 mL solution), which is still a more substantial amount of the pheromone than the amount that is already triggering a response in ant trails—around 500 pg/trail according to literature [34] (233,000 times lower than the concentration used in the present experiment).
As a first step, the surface adsorption properties of mellein on TiO2 were tested to distinguish between the concentration decrease of the mellein solution due to heterogeneous photocatalysis and adsorption. The adsorption–desorption equilibrium in the TiO2-mellein system was established after 60 min of testing. Based on the absorbance spectra (Figure 4), no significant adsorption occurred on the surface of the TiO2; therefore the starting concentration of the photodegradation process was considered the initial 10 μM.
In the first 10 min of the UV-A-assisted photocatalytic test, a notable decrease was observed in the absorbance maximum of the mellein peaks at 247.5 and 314 nm. In the following minutes of the test, this degradation process slowed down but remained constant and gradual. The efficiency of the 2 h long photocatalytic degradation test was calculated to be 62% based on a comparison of areas under the initial spectrum and 120 min spectrum (Figure 4 and Figure 5). If we look at this process on the molecular level, it would mean that if P25 degrades successfully to 62% of the initial amount of 722.64 × 1018 mellein molecules/120 mL test solution, then its effect on ant trails is much more destructive, as these contain a significantly smaller amount, 146 × 1010 molecules/trail.
Since trail pheromones are known to be volatile substances [35], and the product information sheet issued by the manufacturer of mellein warn users about the instability of the aqueous solution, the stability of the 10 mM solution was also tested. When compared, the UV-Vis absorbance spectra of the samples taken during a 24 h stability test in darkness followed by a 2 h UV-A stability test showed no significant change (Figure 6). Examining the spectra on the section above 225 nm, a slight systematic change in the absorbance values of the full spectrum can be observed, which is more likely to be of instrumental origin than due to concentration change. As the peak value at 247.5 nm, belonging to the light absorption band of the aromatic ring, does not decrease compared to the original solution, and there is no shift in the peak position, one can infer that the structure of the mellein molecule can be considered unchanged. Therefore, the stability of the solution in its first 24 h after preparation and its UV-A stability during the 2-hour test was proved.
Two other environmental conditions must be considered, which are needed for photocatalytic degradation to occur in nature. First is the aqueous media, which is easily provided by groundwater and rainfall. The second is the accurate UV-A irradiation for the activation of the photocatalyst. On a European summer day, the average UV-A irradiance of the sun is approximately 18 W/m2 [36]. Compared to this, the irradiance of 58 W/m2 which reaches the foraging experiment setup in each second due to the 6 W UV-A lamp is considerably larger. Nevertheless, the duration of the irradiation is of key importance: while the experiments lasted 9 min, natural sunlight is constantly present during daylight in the life of ants. UV-A irradiation on a summer day can accumulate and reach up to 790 Wh/m2 [37]. This amount of energy is already enough to trigger heterogeneous photocatalysis, as proven by various research where natural sunlight is used for organic pollutant degradation with TiO2 NP [38].
The results of the stability, UV-A stability, adsorption, and heterogeneous photocatalysis tests prove that the compound (R)-(-)-3,4-Dihydro-8-hydroxy-3-methylisocoumarin is degraded under UV-A irradiation in the presence of TiO2 P25 photocatalyst. This outcome of the present research supports the idea that TiO2 is a powerful and non-selective oxidant, due to the generated OH radicals in the presence of irradiation, and as such it is capable of degrading various complex organic compounds, whether a pheromone component or another endobiotic molecule.

3. Materials and Methods

3.1. Instrumentation

The measurement methods applied for the basic characterization of Evonik Aeroxide TiO2 P25 (Evonik, Essen, Germany) were the following. X-ray powder diffraction analysis (XRD) was used to determine the crystal structure and crystal phase of the commercial TiO2, utilizing a Shimadzu XRD 6000 diffractometer (Shimadzu Corporation, Kyoto, Japan) with CuKα radiation (λ = 1.54 Å) and Ni filter, in 2θ range of 20–80°, with 2°/min speed. The primary crystallite size of the samples was also determined from the gathered data using the Scherrer equation [31]. The UV-Vis diffuse reflectance (DRS) spectrum of the TiO2 was recorded with a Jasco-V650 spectrophotometer (Jasco Corporation, Wien, Austria) in the 250–800 nm region, using an ILV-724 integration sphere (Jasco Corporation, Wien, Austria), to investigate its optical properties and calculate its specific bandgap value using the Kubelka–Munk function [39].
To follow the possible compositional or concentration changes in the mellein solution, the samples taken during stability, adsorption, and photodegradation tests were analyzed with the help of a Jasco-V650 UV-Vis spectrophotometer (Jasco Corporation, Wien, Austria) in the range of 200–400 nm.

3.2. Pheromone-Based Foraging Test Method with Lasius niger Ant Species in the Presence of TiO2

To observe the effect of TiO2 on pheromone-based foraging of ants, one of the most common European ant species, the common garden ant (Lasius niger Linnaeus, 1758), was chosen as the test species. Ant workers from the nest surface of a large colony were collected, in order to ensure a similar age of the ants, as well as minimal disturbance of the colony. The ant nest was located on a meadow, near Cluj-Napoca (Cluj County, Romania), where the worker ants were collected at the end of May. The collected ants were kept under laboratory conditions in four artificial nests for acclimatization for two weeks, during which they were fed a widely used artificial food for ants [40]. Before testing, feeding of the worker ants was discontinued for three days to encourage their foraging activity. During each experiment, the four artificial nests were used in random order for the different experimental setups.
The comparative tests were performed in 12 replicates, while the negative and the positive control test were replicated five times, using one random nest for each. Replications were performed in order to rule out the possibility of ants relying on memory instead of a pheromone trail, when choosing between branches, as pointed out by Grüter et al. [41]. Between replications, intervals of 3–4 days were maintained to avoid overfeeding.
The experimental setup consisted of a plastic box (32 cm × 32 cm) connected to a randomly chosen nest through a plastic pipe and a food source inside the experimental box. The bottom of the experimental box was filled with water, above which a diamond-shaped paper bridge with two identical branches was suspended. The role of the bridge was to connect the nest with the artificial ant food, allowing the ants only two possible route choices (Figure 7). Beckers et al. (1992) carried out an experiment using a similar setup [32].
As the objective of the experiments was to investigate the influence of TiO2 nanoparticles on the pheromone-based foraging of ants, for each experiment, one branch of the bridge was treated with an Evonik Aeroxide TiO2 P25 aqueous suspension (1 g·L−1 suspension concentration), while the other branch with distilled water. In the case of negative control, both branches of the bridge were treated with distilled water; in the case of positive control, both branches received a TiO2 suspension treatment. During each experiment, a new paper bridge was used, and a new batch of 0.5 mL artificial ant food was placed at the end of the bridge. Every experiment, including the controls, was performed under UV-A irradiation as the photocatalytic degradation efficiency of the TiO2 is the highest under these conditions. For this, a Philips 6 W black light (Amsterdam, The Netherlands, 95% intensity located in the UV-A range, T5 socket type) lamp with λmax = 365 nm (no UV-B emission) was fastened above the bridge (perpendicular to the position of the bridge—10 cm altitude).
During the data gathering part of the experiments, the number of ants crossing the center of the branches was noted every minute. Each test lasted 9 min, counting from the moment of the first bridge crossing of an ant. The required time frame for the tests was selected based on preliminary experiments.
The statistical analyses of the collected data were carried out in the R software (4.4.2) environment (R Development Core Team 2016), using the lme4 package (1.1.37) [42] to analyze generalized linear mixed models (GLMM, Poisson distribution), where n = 12 for comparative tests and n = 5 for control tests. The analyses were performed separately for each possible experimental setup. In the case of comparative tests, the input variable was the status of the branch (TiO2-treated or not treated), and the output variable was the number of ants crossing the different branches every minute. During positive and negative control experiments, the input variable was the identifier of the bridge’s status (TiO2-treated or not treated). In contrast, the output variable was the number of individuals crossing the bridge (independent of which branch, because both had the same treatment). As a random effect, the individual identifier of the tests was introduced.

3.3. Photocatalytic Degradation Method of the Mellein Pheromone Component

To investigate the photocatalytic effect of TiO2 on the organic components of pheromones, (R)-(-)-3,4-Dihydro-8-hydroxy-3-methylisocoumarin, commonly called (R)-(-)-mellein, was purchased from the Cayman Chemical Company (Ann Arbor, MI, USA) in crystalline solid form, introduced in a solution and used as a general model of organic component in ant pheromone. The compound may contain optical isomers which can interfere with the absorption spectra in terms of intensity (1–5%).
A stock solution of 28 mM concentration of mellein was prepared based on information provided by the manufacturer, using absolute ethanol as solvent. This stock was diluted further with distilled water for the photocatalytic test to obtain a model solution with the 10 μM initial concentration. This last step was always performed freshly, as according to the manufacturer, mellein is not stable in an aqueous solution for more than 24 h.
First and foremost, the stability of the aqueous solution was tested at room temperature, in the dark, and stirred for 24 h, followed by a 2-hour test under the same conditions but with UV-A irradiation. In both cases, multiple samples were taken from the model solution and put under UV-Vis spectroscopy analysis.
The following two types of tests were adsorption tests in dark and photocatalytic tests under UV-A irradiation for which commercially available Evonik Aeroxide TiO2 P25 was suspended in the 10 μM mellein solution, with a 1 g·L−1 suspension concentration. Both types of tests were conducted in a water-cooled Pyrex reactor, at 25 °C, under vigorous stirring and air bubbling (2 L·min−1), and the volume of the testing solution was 120 mL. The adsorption test lasted for an hour, conducted in total darkness, and samples were taken every 10 min for analysis. This was followed by a photocatalytic test, which lasted two hours, during which the photoreactor was irradiated with 6 pcs. of 6 W UV-A lamps (λmax = 365 nm), and samples were taken (centrifuged at 16,000 RPM and filtered using a Whatman Anotop filter, Whatman plc, Maidstone, UK, 20 nm in pore size) and analyzed via UV-Vis spectroscopy every 10 min in the 1st hour, then every 20 min in the 2nd hour. Please note that a small (1–5%), usually positive error might occur due to the light scattering effect of that extremely small number of titania nanoparticles which were not removed.

4. Conclusions

The organic compound mellein ((R)-(-)-3,4-Dihydro-8-hydroxy-3-methylisocoumarin) was degraded by Evonik Aeroxide TiO2 P25 under UV-A irradiation with 62% efficiency in 120 min. Due to the non-selective nature of P25 oxidant, an organic compound similar in structure to mellein, the (R)-3,4-dihydro-8-hydroxy-3,5,7-trimethylisocoumarin (Biomol, Hamburg, Germany), a trail pheromone component of L. niger, should be as easily oxidized as mellein. The only difference between these two structures is that mellein has a phenol ring, while the other is a xylenol, which during oxidation with OH undergoes hydroxymethylation and loses its methylene groups irreversibly. As other pheromone components of L. niger are inactive, there is no possibility of the appearance of biologically active degradation intermediates during the oxidation of (R)-3,4-dihydro-8-hydroxy-3,5,7-trimethylisocoumarin. This way, once the degradation process starts, the irreversible changes in the structure of the L. niger trail pheromone component cause the trail to become inactive. Based on the train of thought above, the results of the heterogeneous photodegradation test of mellein support the idea that its analogue component present in the trail pheromone of L. niger is affected by TiO2, causing irreversible changes in the communication of L. niger worker ants, as seen during the foraging test performed in the first part of the present study. This small change not only impacts ant communication, but potentially also triggers a cascading effect on ant community structure, flora and fauna population dynamics, and ecosystem functioning, all started by the unwanted, disruptive presence of nano titania in our natural habitat.

Author Contributions

Conceptualization, K.S., Z.C. and Z.P.; methodology, Z.P., L.B. and Z.C.; validation, K.S., E.M. and E.E.A.; formal analysis, K.S., E.M., E.E.A. and L.V.L.; investigation, K.S., E.M. and L.V.L.; resources, Z.P. and L.B.; data curation, K.S.; writing—original draft preparation, K.S. and E.M.; writing—review and editing, Z.C., Z.P., L.B. and E.E.A.; visualization, K.S. and Z.C.; supervision, Z.P. and L.B.; project administration, Z.P. and L.B.; funding acquisition, Z.P. and L.B. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Piccinno, F.; Gottschalk, F.; Seeger, S.; Nowack, B. Industrial production quantities and uses of ten engineered nanomaterials in Europe and the world. J. Nanopart. Res. 2012, 14, 1109. [Google Scholar] [CrossRef]
  2. Robichaud, C.O.; Uyar, A.E.; Darby, M.R.; Zucker, L.G.; Wiesner, M.R. Estimates of Upper Bounds and Trends in Nano-TiO2 Production as a Basis for Exposure Assessment. Environ. Sci. Technol. 2009, 43, 4227–4233. [Google Scholar] [CrossRef]
  3. Solymos, K.; Babcsányi, I.; Ariya, B.; Gyulavári, T.; Ágoston, Á.; Kukovecz, Á.; Kónya, Z.; Pap, Z. Environmental significance of the interaction between titanium dioxides and soil solutions. Environ. Sci. Eur. 2024, 36, 85. [Google Scholar] [CrossRef]
  4. Wu, K.C.-W.; Yamauchi, Y.; Hong, C.-Y.; Yang, Y.-H.; Liang, Y.-H.; Funatsu, T.; Tsunoda, M. Biocompatible, surface functionalized mesoporous titania nanoparticles for intracellular imaging and anticancer drug delivery. Chem. Commun. 2011, 47, 5232. [Google Scholar] [CrossRef]
  5. Eshaghi, M.M.; Pourmadadi, M.; Rahdar, A.; Díez-Pascual, A.M. Improving quercetin anticancer activity through a novel polyvinylpyrrolidone/polyvinyl alcohol/TiO2 nanocomposite. J. Drug Deliv. Sci. Technol. 2023, 81, 104304. [Google Scholar] [CrossRef]
  6. Younes, M.; Aquilina, G.; Castle, L.; Engel, K.; Fowler, P.; Fernandez, M.J.F.; Fürst, P.; Gundert-Remy, U.; Gürtler, R.; Husøy, T.; et al. Safety assessment of titanium dioxide (E171) as a food additive. EFSA J. 2021, 19, e06585. [Google Scholar] [CrossRef] [PubMed]
  7. Lu, P.-J.; Huang, S.-C.; Chen, Y.-P.; Chiueh, L.-C.; Shih, D.Y.-C. Analysis of titanium dioxide and zinc oxide nanoparticles in cosmetics. J. Food Drug Anal. 2015, 23, 587–594. [Google Scholar] [CrossRef]
  8. Kokkonen, M.; Talebi, P.; Zhou, J.; Asgari, S.; Soomro, S.A.; Elsehrawy, F.; Halme, J.; Ahmad, S.; Hagfeldt, A.; Hashmi, S.G. Advanced research trends in dye-sensitized solar cells. J. Mater. Chem. A 2021, 9, 10527–10545. [Google Scholar] [CrossRef]
  9. Chen, M.C.; Koh, P.W.; Ponnusamy, V.K.; Lee, S.L. Titanium dioxide and other nanomaterials based antimicrobial additives in functional paints and coatings: Review. Prog. Org. Coat. 2022, 163, 106660. [Google Scholar] [CrossRef]
  10. Gardy, J.; Hassanpour, A.; Lai, X.; Ahmed, M.H.; Rehan, M. Biodiesel production from used cooking oil using a novel surface functionalised TiO2 nano-catalyst. Appl. Catal. B 2017, 207, 297–310. [Google Scholar] [CrossRef]
  11. Guo, Q.; Zhou, C.; Ma, Z.; Yang, X. Fundamentals of TiO2 Photocatalysis: Concepts, Mechanisms, and Challenges. Adv. Mater. 2019, 31, 1901997. [Google Scholar] [CrossRef]
  12. Gottschalk, F.; Sonderer, T.; Scholz, R.W.; Nowack, B. Modeled Environmental Concentrations of Engineered Nanomaterials (TiO2, ZnO, Ag, CNT, Fullerenes) for Different Regions. Environ. Sci. Technol. 2009, 43, 9216–9222. [Google Scholar] [CrossRef] [PubMed]
  13. Bundschuh, M.; Filser, J.; Lüderwald, S.; McKee, M.S.; Metreveli, G.; Schaumann, G.E.; Schulz, R.; Wagner, S. Nanoparticles in the environment: Where do we come from, where do we go to? Environ. Sci. Eur. 2018, 30, 6. [Google Scholar] [CrossRef]
  14. Heilgeist, S.; Sekine, R.; Sahin, O.; Stewart, R.A. Finding Nano: Challenges Involved in Monitoring the Presence and Fate of Engineered Titanium Dioxide Nanoparticles in Aquatic Environments. Water 2021, 13, 734. [Google Scholar] [CrossRef]
  15. Hou, J.; Wang, L.; Wang, C.; Zhang, S.; Liu, H.; Li, S.; Wang, X. Toxicity and mechanisms of action of titanium dioxide nanoparticles in living organisms. J. Environ. Sci. 2019, 75, 40–53. [Google Scholar] [CrossRef]
  16. Knaden, M.; Graham, P. The Sensory Ecology of Ant Navigation: From Natural Environments to Neural Mechanisms. Annu. Rev. Entomol. 2016, 61, 63–76. [Google Scholar] [CrossRef]
  17. Czaczkes, T.J.; Grüter, C.; Jones, S.M.; Ratnieks, F.L.W. Synergy between social and private information increases foraging efficiency in ants. Biol. Lett. 2011, 7, 521–524. [Google Scholar] [CrossRef]
  18. Czaczkes, T.J. Communication: Recruitment to Resources. In Encyclopedia of Social Insects; Springer International Publishing: Cham, Switzerland, 2021; pp. 267–274. [Google Scholar] [CrossRef]
  19. Morgan, E.D. Trail pheromones of ants. Physiol. Entomol. 2009, 34, 1–17. [Google Scholar] [CrossRef]
  20. Székely, I.; Baia, M.; Magyari, K.; Boga, B.; Pap, Z. The effect of the pH adjustment upon the WO3-WO3·0.33H2O-TiO2 ternary composite systems’ photocatalytic activity. Appl. Surf. Sci. 2019, 490, 469–480. [Google Scholar] [CrossRef]
  21. Ferrara, G.; Salvaggio, A.; Pecoraro, R.; Scalisi, E.M.; Presti, A.M.; Impellizzeri, G.; Brundo, M.V. Toxicity assessment of nano-TiO2 in Apis mellifera L. 1758: Histological and immunohistochemical assays. Microsc. Res. Tech. 2020, 83, 332–337. [Google Scholar] [CrossRef] [PubMed]
  22. Papa, G.; Di Prisco, G.; Spini, G.; Puglisi, E.; Negri, I. Acute and chronic effects of Titanium dioxide (TiO2) PM1 on honey bee gut microbiota under laboratory conditions. Sci. Rep. 2021, 11, 5946. [Google Scholar] [CrossRef]
  23. Czekes, Z.; Bai, D.; Vincze, J.; Gál, E.; Réthi-Nagy, Z.; Baia, L.; Pap, Z. Commercial photocatalyst changes the behavior of Formica pratensis and Formica polyctena. Environ. Sci. Nano 2023, 10, 72–79. [Google Scholar] [CrossRef]
  24. Gutiérrez-Ramírez, J.A.; Betancourt-Galindo, R.; Aguirre-Uribe, L.A.; Cerna-Chávez, E.; Sandoval-Rangel, A.; Del Ángel, E.C.; Chacón-Hernández, J.C.; García-López, J.I.; Hernández-Juárez, A. Insecticidal Effect of Zinc Oxide and Titanium Dioxide Nanoparticles against Bactericera cockerelli Sulc. (Hemiptera: Triozidae) on Tomato Solanum lycopersicum. Agronomy 2021, 11, 1460. [Google Scholar] [CrossRef]
  25. Gutiérrez-Ramírez, J.A.; Betancourt-Galindo, R.; Aguirre-Uribe, L.A.; Cerna-Chávez, E.; Sandoval-Rangel, A.; Ángel, E.C.; Chacón-Hernández, J.C.; García-López, J.I.; Hernández-Juárez, A. Investigating the Insecticidal Properties of Titanium Oxide Nanoparticles against Periplaneta americana. Entomol. Lett. 2021, 1, 1–7. [Google Scholar] [CrossRef]
  26. De Almeida, T.; Mesléard, F.; Santonja, M.; Gros, R.; Dutoit, T.; Blight, O. Above- and below-ground effects of an ecosystem engineer ant in Mediterranean dry grasslands. Proc. R. Soc. B Biol. Sci. 2020, 287, 20201840. [Google Scholar] [CrossRef]
  27. Folgarait, P.J. Ant biodiversity and its relationship to ecosystem functioning: A review. Biodivers. Conserv. 1998, 7, 1221–1244. [Google Scholar] [CrossRef]
  28. Sanders, D.; van Veen, F.J.F. Ecosystem engineering and predation: The multi-trophic impact of two ant species. J. Anim. Ecol. 2011, 80, 569–576. [Google Scholar] [CrossRef] [PubMed]
  29. Ohtani, B.; Prieto-Mahaney, O.O.; Li, D.; Abe, R. What is Degussa (Evonik) P25? Crystalline composition analysis, reconstruction from isolated pure particles and photocatalytic activity test. J. Photochem. Photobiol. A Chem. 2010, 216, 179–182. [Google Scholar] [CrossRef]
  30. Kehres, J.; Andreasen, J.W.; Krebs, F.C.; Molenbroek, A.M.; Chorkendorff, I.; Vegge, T. Combined in situ small- and wide-angle X-ray scattering studies of TiO2 nanoparticle annealing to 1023 K. J. Appl. Crystallogr. 2010, 43, 1400–1408. [Google Scholar] [CrossRef]
  31. Hossain, M.S.; Ahmed, S. Easy and green synthesis of TiO2 (Anatase and Rutile): Estimation of crystallite size using Scherrer equation, Williamson-Hall plot, Monshi-Scherrer Model, size-strain plot, Halder- Wagner Model. Results Mater. 2023, 20, 100492. [Google Scholar] [CrossRef]
  32. Beckers, R.; Deneubourg, J.L.; Goss, S. Trail laying behaviour during food recruitment in the ant Lasius niger (L.). Insectes Soc. 1992, 39, 59–72. [Google Scholar] [CrossRef]
  33. Czaczkes, T.J.; Grüter, C.; Ellis, L.; Wood, E.; Ratnieks, F.L.W. Ant foraging on complex trails: Route learning and the role of trail pheromones in Lasius niger. J. Exp. Biol. 2012, 216, 188–197. [Google Scholar] [CrossRef]
  34. Bestmann, H.J.; Kern, F.; Schafer, D.; Witschel, M.C. 3,4-Dihydroisocoumarins, a New Class of Ant Trail Pheromones. Angew. Chem. Int. Ed. Engl. 1992, 31, 795–796. [Google Scholar] [CrossRef]
  35. Klowden, M.J. Communication Systems. In Physiological Systems in Insects; Elsevier: Amsterdam, The Netherlands, 2008; pp. 597–642. [Google Scholar] [CrossRef]
  36. Proutsos, N.; Alexandris, S.; Liakatas, A.; Nastos, P.; Tsiros, I.X. PAR and UVA composition of global solar radiation at a high altitude Mediterranean forest site. Atmos. Res. 2022, 269, 106039. [Google Scholar] [CrossRef]
  37. Cañada, J.; Esteve, A.R.; Marín, M.J.; Utrillas, M.P.; Tena, F.; Martínez-Lozano, J.A. Study of erythemal, UV (A + B) and global solar radiation in Valencia (Spain). Int. J. Climatol. 2008, 28, 693–702. [Google Scholar] [CrossRef]
  38. Ramamoorthy, S.; Das, S.; Balan, R.; Lekshmi, I.C. TiO2-ZrO2 nanocomposite with tetragonal zirconia phase and photocatalytic degradation of Alizarin Yellow GG azo dye under natural sunlight. Mater. Today Proc. 2021, 47, 4641–4646. [Google Scholar] [CrossRef]
  39. Landi, S.; Segundo, I.R.; Freitas, E.; Vasilevskiy, M.; Carneiro, J.; Tavares, C.J. Use and misuse of the Kubelka-Munk function to obtain the band gap energy from diffuse reflectance measurements. Solid State Commun. 2022, 341, 114573. [Google Scholar] [CrossRef]
  40. Bhatkar, A.; Whitcomb, W.H. Artificial Diet for Rearing Various Species of Ants. Fla. Entomol. 1970, 53, 229. [Google Scholar] [CrossRef]
  41. Grüter, C.; Czaczkes, T.J.; Ratnieks, F.L.W. Decision making in ant foragers (Lasius niger) facing conflicting private and social information. Behav. Ecol. Sociobiol. 2011, 65, 141–148. [Google Scholar] [CrossRef]
  42. Bates, D.; Mächler, M.; Bolker, B.; Walker, S. Fitting Linear Mixed-Effects Models Using lme4. J. Stat. Softw. 2015, 67, 1–48. [Google Scholar] [CrossRef]
Catalysts 15 01040 g001
Figure 1. XRD pattern (upper left), DRS spectrum/first derivative DRS spectrum (upper right) and TEM micrograph (lower centered) of Evonik Aeroxide TiO2 P25 nanoparticles.
Figure 1. XRD pattern (upper left), DRS spectrum/first derivative DRS spectrum (upper right) and TEM micrograph (lower centered) of Evonik Aeroxide TiO2 P25 nanoparticles.
Catalysts 15 01040 g001
Catalysts 15 01040 g002
Figure 2. The difference between the number of foraging ant workers (a) on TiO2-suspension-treated (white) and water-treated (grey) branches of the experimental setup; (b) in the case when both branches were treated with distilled water (negative control); (c) in the case when both branches were treated with TiO2 suspension (positive control) during the experiments. The plots represent the median of all data, higher and lower quarters, maximum and minimum data (boxplots), and idealized data distribution (side curves). Statistically significant differences are marked with asterisks (* p ≤ 0.05, ** p ≤ 0.005, *** p ≤ 0.0001).
Figure 2. The difference between the number of foraging ant workers (a) on TiO2-suspension-treated (white) and water-treated (grey) branches of the experimental setup; (b) in the case when both branches were treated with distilled water (negative control); (c) in the case when both branches were treated with TiO2 suspension (positive control) during the experiments. The plots represent the median of all data, higher and lower quarters, maximum and minimum data (boxplots), and idealized data distribution (side curves). Statistically significant differences are marked with asterisks (* p ≤ 0.05, ** p ≤ 0.005, *** p ≤ 0.0001).
Catalysts 15 01040 g002
Catalysts 15 01040 g003
Figure 3. (a). (R)-3,4-dihydro-8-hydroxy-3,5,7-trimethylisocoumarin—pheromone component of Lasius niger (b). (R)-(-)-3,4-Dihydro-8-hydroxy-3-methylisocoumarin—pheromone component of Formica rufa.
Figure 3. (a). (R)-3,4-dihydro-8-hydroxy-3,5,7-trimethylisocoumarin—pheromone component of Lasius niger (b). (R)-(-)-3,4-Dihydro-8-hydroxy-3-methylisocoumarin—pheromone component of Formica rufa.
Catalysts 15 01040 g003
Catalysts 15 01040 g004
Figure 4. UV-Vis absorbance spectra of the most relevant samples taken during the adsorption and UV-A-assisted photodegradation tests of 10 µM mellein in the presence of titania.
Figure 4. UV-Vis absorbance spectra of the most relevant samples taken during the adsorption and UV-A-assisted photodegradation tests of 10 µM mellein in the presence of titania.
Catalysts 15 01040 g004
Catalysts 15 01040 g005
Figure 5. Adsorption after 60 min and degradation curve of 10 µM mellein followed at 247.5 nm in the presence of titania.
Figure 5. Adsorption after 60 min and degradation curve of 10 µM mellein followed at 247.5 nm in the presence of titania.
Catalysts 15 01040 g005
Catalysts 15 01040 g006
Figure 6. UV-Vis absorbance spectra of the most relevant samples taken during the stability tests of 10 µM mellein in the absence of titania (under irradiation/dark).
Figure 6. UV-Vis absorbance spectra of the most relevant samples taken during the stability tests of 10 µM mellein in the absence of titania (under irradiation/dark).
Catalysts 15 01040 g006
Catalysts 15 01040 g007
Figure 7. (a) Photograph of the experimental setup. (b) Sketch of the experimental setup and the test types, where grey indicates distilled water treatment of the branch and white indicates the TiO2 suspension treatment of the branch.
Figure 7. (a) Photograph of the experimental setup. (b) Sketch of the experimental setup and the test types, where grey indicates distilled water treatment of the branch and white indicates the TiO2 suspension treatment of the branch.
Catalysts 15 01040 g007
Table 1. Results of the statistical testing of the differences between the number of ant workers passing the two branches for each of the three setups (* p < 0.05; ** p < 0.01; *** p < 0.001).
Table 1. Results of the statistical testing of the differences between the number of ant workers passing the two branches for each of the three setups (* p < 0.05; ** p < 0.01; *** p < 0.001).
Experimental Setupzp
positive control
1. min.−0.500.61
2. min.0.880.37
3. min.--
4. min.--
5. min.--
6. min.−1.130.25
7. min.−0.810.41
8. min.−0.710.47
9. min.−1.050.29
negative control
1. min.−0.190.84
2. min.−0.440.65
3. min.−0.300.76
4. min.−1.240.21
5. min.2.405 *0.016
6. min.−0.500.61
7. min.−1.760.07
8. min.−3.369 ***<0.001
9. min.−0.700.48
comparative test
1. min.1.060.28
2. min.0.200.83
3. min.−2.91 **0.003
4. min.−3.080 **0.002
5. min.−3.390 ***<0.001
6. min.−5.101 ***<0.001
7. min.−4.599 ***<0.001
8. min.−5.911 ***<0.001
9. min.−5.869 ***<0.001
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MDPI and ACS Style

Saszet, K.; Mátyás, E.; Almási, E.E.; Lakatos, L.V.; Czekes, Z.; Pap, Z.; Baia, L. Photocatalytic Degradation of Ant Trail Pheromones by P25 TiO2. Catalysts 2025, 15, 1040. https://doi.org/10.3390/catal15111040

AMA Style

Saszet K, Mátyás E, Almási EE, Lakatos LV, Czekes Z, Pap Z, Baia L. Photocatalytic Degradation of Ant Trail Pheromones by P25 TiO2. Catalysts. 2025; 15(11):1040. https://doi.org/10.3390/catal15111040

Chicago/Turabian Style

Saszet, Kata, Eszter Mátyás, Eszter Enikő Almási, Laura Vivien Lakatos, Zsolt Czekes, Zsolt Pap, and Lucian Baia. 2025. "Photocatalytic Degradation of Ant Trail Pheromones by P25 TiO2" Catalysts 15, no. 11: 1040. https://doi.org/10.3390/catal15111040

APA Style

Saszet, K., Mátyás, E., Almási, E. E., Lakatos, L. V., Czekes, Z., Pap, Z., & Baia, L. (2025). Photocatalytic Degradation of Ant Trail Pheromones by P25 TiO2. Catalysts, 15(11), 1040. https://doi.org/10.3390/catal15111040

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