The first two years of the project were conducted in the group of Prof. Wiesner at Cornell University in the United States. This period was dedicated to the synthesis and development of these new materials with complex architectures. In this regards, new methods have been established for the synthesis of luminescent quantum dots with improved optical properties and their encapsulation in silica nanoparticles as a biocompatible material (Fig. 1). In addition, this silica matrix provided a versatile platform for the subsequent surface functionalization with zwitterionic groups. During this period, it was demonstrated that such functionalization allowed endosomal uptake of the nanoparticles by live cells (Fig. 1), while ensuring good colloidal stability. New methods have also been investigated for the synthesis of ultrasmall and water soluble plasmonic gold and/or silver nanoparticles. These metal nanoparticles can thereafter bind to silica coated quantum dots thanks to prior surface modification with amine or thiol groups.
In parallel, new nanoparticles structures have also been discovered through the self-assembly of mesoporous silica. This approach resulted in particular in the formation of ultrasmall particles with dodecahedral cage and ring morphologies (Fig. 2). Given the versatility of silica surface chemistry, and the ability to distinguish the inside and outside of the cages and rings, these materials might prove themselves particularly useful as cargo containers for smart drug delivery strategies.
The final year of NanoIntra was carried out in the group of Prof. Zeger Hens at Ghent University, Belgium. Following the discovery of dodecahedral silica cages in the first part of the project, a new 2D materials (Fig. 3) was conceived through the confined growth of these cages at an interface between two immiscible liquids. Varying the synthesis conditions offered a fine control over the thickness and structure of these 2D superstructures, revealing emergence of structural order in mesoporous materials.
Finally a new approach was developed for the integration of silica cages with 3D printing by digital light processing. To this end, the nanostructure were functionalized with photoresponsive ligands, enabling the direct printing of mesoporous parts without any post-treatment required. In addition the versatile silica chemistry studied in NanoIntra, allowed for the positioning of functionalities within the printed parts. This approach can be implemented for selective binding mechanisms in bioassays for instance.
Overview of the results and dissemination:
The results obtained within NanoIntra were disseminated through publication in peer-reviewed articles in scientific journals:
- The Impact of core/shell sizes on the optical gain characteristics of CdSe/CdS quantum dots, S. Bisschop, P. Geiregat, T. Aubert, Z. Hens, ACS Nano 2018, 12 (9), 9011-9021.
- Self-assembly of highly symmetrical, ultrasmall inorganic cages directed by surfactant micelles, K. Ma, Y. Gong, T. Aubert, M.Z. Turker, T. Kao, P.C. Doerschuk, U. Wiesner, Nature 2018, 558 (7711), 577-580.
- Fluorescent silica nanoparticles with well-separated intensity distributions from batch reactions, T. Kao, F. Kohle, K. Ma, T. Aubert, A. Andrievsky, U. Wiesner, Nano Lett. 2018, 18 (2), 1305-1310.
- Efficient Endocytosis of Inorganic Nanoparticles with Zwitterionic Surface Functionalization, E. Drijvers, J. Liu, A. Harizaj, U. Wiesner, K. Braeckmans, Z. Hens, T. Aubert, ACS Appl. Mater. Interfaces 2019, 11 (42), 38475-38482.
- Two‐Dimensional Superstructures of Silica Cages, T. Aubert, K. Ma, K. W. Tan, U. Wiesner, Adv. Mater. 2020, 32, 1908362.
