Engineered supramolecular metallogels as luminescent 3D-printable materials Tomas Gudmundsson, Sebastian Barwich, Matthias Möbius Trinity College Dublin, Ireland
The development of functional supramolecular gels for 3D-printing is an emerging field with impressive potential. Supramolecular gels are viscoelastic soft materials that can be functionalised with metals to generate metallogels with applications in luminescence-based technologies, conductive devices, and even in anti-tumour therapies. 1 Additionally, 3D-printing facilitates the generation of complex shapes and structures which can be easily adapted for the desired purpose, such as polymer gels that have been 3D-printed for specific tissue engineering. 2 Supramolecular gels form by reversible non-covalent interactions, such as metal coordination and hydrogen- bonding, which endow the gel with self-healing properties that can be manipulated for extrusion-based printing. Under enough strain, the gels will turn into viscous liquids and regain their gel state once the extrusion is complete, making them ideal for facile extrusion-printing. 3 Introducing supramolecular metallogels to 3D-printing opens up new avenues in the generation of novel functional materials. The design of the organic gelator ligand utilised here is based on the C 3 -symmetric benzene-1,3,5-tricarboxamide (BTA) platform functionalised with terminal terpyridine ( tpy ) moieties. The tpy ligand acts as a coordinating group for metal ions, and it also serves as an antennae for lanthanide emission: the emission of Ln(III) ions due to forbidden f-f transitions is weak, but is greatly sensitised by tpy . 4, 5 Gels were successfully generated, and various d -metal ion solutions were passed through the gel with visible colour changes and changes in emission spectra. Solutions of lanthanides Tb(III) and Eu(III) were passed through the gel and time-gated emission experiments showed the characteristic sharp phosphorescence emission spectra for the respective ions. Additionally, red and green luminescent metallogels were made by directly incorporating Eu(III) and Tb(III). Luminescent Eu(III) materials have been used in currencies to avoid counterfeiting and the sensing properties of the gel in synchrony with extrusion-manufacturing introduces applications for the material e.g. as a sensor in membranes or in anti- counterfeiting measures.
Figure 1. a) Metallogels made by incorporating metals into the gel structure by gelation. c) Extruded Eu/Tb gels excited at 365 nm for luminescence. References 1. H. Wu, J. Zheng, A-L. Kjøniksen, W. Wang, Y. Zhang, J. Ma, Adv. Mater. , 2019 , 31 , 1806204. 2. R. C. Advincula, J. R. C. Dizon, E. B. Caldona, R. A. Viers, F. D. C. Siacor, R. D. Maalihan, A. H. Espera, MRS Commun. , 2021 , 11 , 539-553. 3. M. C. Nolan, A. M. Fuentes Caparrós, B. Dietrich, M. Barrow, E. R. Cross, M. Bleuel, S. M. King, D. J. Adams, Soft Matter , 2017 , 13 , 8426-8432. 4. O. Kotova, R. Daly, C. M. G. dos Santos, M. Boese, P. E. Kruger, J. J. Boland, T. Gunnlaugsson, Angew. Chem. Int. Ed. , 2012 , 51 , 7208-7212. 5. O. Kotova, R. Daly, C. M. G. dos Santos, P. E. Kruger, J. J. Boland, T. Gunnlaugsson, Inorg. Chem. , 2015 , 54 , 7735-7741
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