Abstract
Chemical technologies based on light have acquired a paramount importance in the last years, as they can allow the realization of sustainable systems for the production of energy and heat and for the fuelling of chemical transformations, as well as the remote control of chemical switches and material response. Among the different applications, photothermal catalysis (PTC) is of particular relevance since it allows to use low intensity irradiation, as that provided by solar light, to promote the conversion of raw materials, including environmentally dangerous chemicals, into useful products, as fuels. Nanosized photothermal agent (nPTAs), i.e. nanostrucuterd materials capable to convert the energy associated to light into chemically exploitable forms, are the crucial elements of PCT. Photothermal catalysis is thought to proceed mainly by nPTAs-induced generation and injection hot-electrons, in combination with other photochemical effects. However, we are convinced that also the specific temperature enhancement achieved in the close proximity of the nPTAs can play a relevant role. Unfortunately, the investigation and development of applications of the photothermal effect is hampered by the fact that the few physical methods available to detect local temperature changes at the nanometer scale present several drawbacks, including the need of intense focalized laser irradiation and of expensive and dedicated custom setup, and in particular the lack of sufficient spatial resolution. On the other hand, fluorescence based molecular thermometers are not sensitive enough to allow the investigation of small samples fractions and can be hardly applied to systems featuring relevant quenching ability. In this project, we propose to solve this problem by developing tools capable to amplify the response by “integrating” in time the effect of the localized photoactivity. This goal will be achieved using irreversible OFF/ON probes based on photolabile linkers. The switching on of these probes will be hence the demonstration that high temperature has been reached at least in proximity of the nPTAs. The amount and localization of the products will provide information about the temperature reached and the size of the photoactive area. Three different classes of nPTAs, granting the appropriate features to effectively promote PTC will be studied, namely gold plasmonic nanoparticles, graphene derivatives and melanin-like nanoparticles. The application of our newly developed probes to these nPTAs will bring about several relevant achievements: namely, the understanding of the heat generation effect by nPTAs at the nanometre scale, a detailed comprehension of the mechanisms of photothermal catalysis, the proof-of-concept demonstration of the possibility to use localized photoinduced heating to promote chemical reactions, the development of thermolabile linkers that could find applications in fields as drug release and phototriggered materials.
Results achieved
The NANOTHERM project aimed to develop innovative tools for the study of the photothermal effect induced by light-absorbing nanomaterials, with particular attention to the localized heating induced by moderate light irradiation. The planned strategy involved the synthesis and characterization of photolabile molecules capable of acting as temperature "integrators". The extent of probe degradation was demonstrated to be proportional to the time of exposure and of the temperature reached in the microenvironment of the probes. Recycling of the probes in the small volume of solution affected by the heating allowed significant signal amplification and the possibility to detect localized heating effects. These probes were tested using different types of nanomaterials capable of light-into-heat transduction. The project implementation was shared by two operational units (UniPD and UniBO) with complementary expertise and distinct roles. In particular UniPD mostly took care of the synthesis and thermal characterization of the molecular probes while UniBO mostly performed the photothermal experiments. The kick-off meeting of the project was held on February 26th, 2024, attended by delegates from the two units. The research activity started immediately and is proceeding according to the schedule. Periodic meetings between the teams occur regularly online. On June 17th 2025 joint measurements were performed in Padova by Fei Guo and Silvia Vincenzi. Several molecular temperature probes have been prepared and characterized, as well as the nanoabsorbers. Light irradiation tests were performed on different materials, with positive results, demonstrating the possibility to monitor local temperature changes. Additionally, this technology was applied to the chemical functionalization of nanoparticles creating light-responsive coating and enabling the light driven control of the nanoparticles’ properties. The achievement of the project objectives is detailed as follows: • Milestone 1: Design and synthesis of the photothermal probes, successfully achieved. Task 1.1 provided probes with the desired features while probes obtained in tasks 1.2 and 1.3 were suboptimal to the project needs and, being redundant, were abandoned. • Milestone 2: Synthesis of photothermal inorganic and organic photothermal platforms, successfully achieved. Gold nanoparticles and nanorods (task 2.1), liquid exfoliated graphene (task 2.2) and porous polydopamine nanoparticles (task 2.3) were prepared and investigated. • Milestone 3: Comparison of the photothermal properties of inorganic and organic photothermal platforms: partially achieved. Bulk investigation of the photothermal properties of the nanoparticles were performed (task 3.1) as well as fluorescence microscopy investigations (task 3.2), leading to the discovery of relevant thermal effects and selective photothermal catalysis. However, dissection of the factors at the bases of photothermal acceleration of chemical processes will require additional investigation. The project does not harm the environment but rather aims to develop methods and processes that will improve the environmental impact of chemical processes. Hosting Institutions are highly committed to ensure wide dissemination of research results and equal opportunities in access to research and employment. To this end, all the selections made were carried out in accordance with these criteria. Peer-reviewed papers. The project led to the publication of three review articles and four research articles: 1. Chem. Eur. J. 2024, 30, e202400461 2. Antioxidants 2025, 14, 376 3. J. Funct. Biomater. 2025, 16, 243 4. J. Am. Chem. Soc. 2025, 147, 10031-10043; 5. Nanoscale Adv. 2025, 7, 6786-6790; 6. Small 2026, 22, e07110; 7. Chem. Eur. J. 2026, 32, e02967. Conferences dissemination: The results of the project were presented so far in poster form at the International Supramolecular Chemistry Summer School (Pula, May 26th-30th 2024), at the National Conference of Supramolecular Chemistry (Pavia, September 10th-13th 2024), at the International School of Photocatalysis (Padova, June 2nd-7th 2024), at the European Winter School on Physical Organic Chemistry (Bressanone, 2nd – 7th February 2025) and at the Supramolecular Chemistry Days for Young Researchers (Salerno, June 11th-13th 2025) by members of the UniPD team, and at the 6th International Caparica Symposium on Nanoparticles/Nanomaterials and Applications (Costa de Caparica, Portugal, January 22nd-25th, 2024) by members of the UniBo team. Other presentations to conferences and schools are in program in the next summer.Project details
Unibo Team Leader: Marco Montalti
Unibo involved Department/s:
Dipartimento di Chimica "Giacomo Ciamician"
Coordinator:
Università degli Studi di GENOVA(Italy)
Total Unibo Contribution: Euro (EUR) 112.000,00
Project Duration in months: 24
Start Date:
30/11/2023
End Date:
28/02/2026
