Project Results:
WP1- Design and synthesis of multifunctional SR-MOFs.
Mostly, we employed solvothermal synthesis to get single crystals. Cu(I) was mainly used as metal, since it is able to interact with thiolates ligands known as 2,2'-dithiobis(5-nitropyridine) (SNP) and 6,6'-dithiodinicotinic acid (H2dtdn), to obtain MOFs with suitable optical and/or electrical properties.
Working with copper(I) iodide and 6,6'-dithiodinicotinic acid (H2dtdn) and its reduced form 6-mercaptonicotinic acid (6mna), three new coordination polymers, named CP1-3, were synthesized.
On the other hand, the interaction of 2,2'-dithiobis(5-nitropyridine) (SNP) with copper(I) iodide gave rise to three new coordination complexes, named complexes 4-6.
WP2- Structural and optical/electrical characterization.
The structures of the six newly synthetized complexes were fully characterized by different techniques: i) single crystal and powder X-ray diffraction, ii) infrared spectroscopy and iii) thermal stability studies.
The optical properties of all complexes, such as absorption, emission, quantum yield and excited-state lifetime, were evaluated by means of steady-state and time-resolved spectroscopic and photophysical techniques.
The electrical properties of the complexes were measured on single crystals using a two-contact set-up.
From the structural point of view, CP1 and CP3 are 2D-CPs while CP2 is 1D-CP, with an interesting crystal arrangement. Complexes 4 and 5 are 2D-CPs while 6 is a particular hexanuclear cluster.
The three CPs 1-3 showed a semiconductive behavior and CP1 and CP2 displayed an intense emission, in the 600-700 nm range, at low temperature (77 K). Complex 6 was found to be strongly emissive in the near-infrared region and complex 4 has shown an interesting photo-induced electrical behaviour. Theoretical calculations were performed in order to describe the electronic transitions at the origin of the observed optical outcomes.
WP3- Test of the sensing properties towards selected VOCs.
Test studies on the response of the prepared complexes towards selected analytes have been performed.
Among the prepared materials, complex 6 showed good sensitivity towards NaHS, in terms of photoluminescence quenching and colour change, from red to black. This interesting response predicts its application for the detection of H2S, a known poisonous gas.
On the other hand, the room-temperature non-emissive CP1 complex has shown a switch-on emission behaviour when immersed in acetic acid. Due to the low crystallinity of the obtained new phase, it was difficult to clarify the possible structural changes induced by the guest.
While most of the achieved deliverables contributed to expand considerably the knowledge on synthesis, characterization and sensing application of MOFs, some limitations were encountered in some specific domains, such as:
- Obtaining porous MOFs/CPs;
- Deposition of the obtained CPs on surfaces (WP4) due to the lack of solubility.
Exploitation and dissemination of the results.
The outcomes of the project have been presented at nine national and international events. One paper has been recently submitted and forthcoming papers are in preparation. Dissemination to the large public of the importance of MOFs and of their applications in sensing and cultural heritage preservation has been achieved through the participation of the ER and the Supervisor in the European Researchers’ Nights events in 2017 and 2018 in Bologna with a stand, presentations and activities.
