Research

The “Synthesis of Nanoscale Systems” group was established in 2007 with the appointment of Prof. Dr. Bart Jan Ravoo. At that time, our group was one of three new groups founded at the Westfälische Wilhelms-Universität Münster in the framework of the so-called FOKUS Initiative. The purpose of this initiative is to foster interfaculty links and collaboration between the disciplines of Physics, Chemistry and Biology in the field of nanoscience and nanotechnology.

Our group is based in the Organic Chemistry Institute. We are also affiliated to SoN, the recently established Center for Soft Nanoscience, and to CeNTech, the Münster Center for Nanotechnology. The group focuses on three main areas of research: biomimetic supramolecular chemistry, surface functionalization by molecular self-assembly and functional (nano)particles. We develop new materials and chemical systems that are characterized by molecular organization on the nanoscale. Self-assembly is a key issue throughout our research and we approach nanotechnology from the bottom-up.

Figure 1
Figure 1: Schematic illustration of arylazopyrazole based supramolecular systems. [J. Am. Chem. Soc. 2016, 138, 4547–4554].
© AK Ravoo

One of our main topics is the creation of stimuli-responsive supramolecular assemblies composed of multiple small building blocks connected via multiple weak interactions such as host-guest complexes. Since these systems are typically held together by highly multivalent interactions an excellent stimuli-response is needed to reach a switchable system. To this end, we recently introduced arylazopyrazoles (AAPs) as a new class of photochromic azo compounds that offer high yielding E/Z-isomerization in both directions by irradiation with light. Since AAPs show light-responsive host-guest interactions with beta-cyclodextrin they were applied in supramolecular soft materials composed of cyclodextrin vesicles or cyclodextrin decorated (nano)particles [J. Am. Chem. Soc. 2016, 138, 4547–4554].

Figure 2
Figure 2: Functionalization of Indol-SAMs through TAD-reclick chemistry and ATRP polymerization of polymer brushes for rewritable surfaces [Angew. Chem. Int. Ed. 2015, 54, 13126–13129].
© AK Ravoo

Surfaces and their properties are of great importance and interest in chemistry and material sciences. Surfaces have to be functionalized in a very specific way to obtain the desired properties for the desired application. We are using different approaches and techniques that enable us to achieve a high variety of functionalities on surfaces. Recently, we could produce rewritable, structured surfaces containing polymer brushes, which allow a reversible control of surface patterns and properties  [Angew. Chem. Int. Ed. 2015, 54, 13126–13129].

Another example shows the combination of surface chemistry with supramolecular chemistry to receive adhesive surfaces based on non-covalent interactions [Chem. Commun. 2016, 52, 1964-1966].

We are also interested in sensors. In a recent project, active enzymes were coupled to surfaces [Bioconjugate Chem. 2015, 26, 1017–1020].

Figure 3
Figure 3: Host–guest complexation of monovalent Azo-TEG or AAP-TEG in the cavity of CDA@UCNPs and release after NIR irradiation; Aggregation experiment using a divalent Azo-linker or AAP-linker and CDA@UCNP. [Chem. Commun., 2017,53, 240-243]
© AK Ravoo

 

 

Nanoparticles constitute a fascinating research field, which is mainly due to their extraordinary properties, such as the enormous surface to volume ratio, offering unique properties that are very different to bulk material. In our group we developed a broad expertise of nanoparticle research, including noble metal, silica, magnetite and lanthanide-doped nanoparticles. Amongst others, we have functionalized nanoparticles with cyclodextrins, so that the properties of the nanoparticles can be directed by host-guest chemistry. In close cooperation with the group of Prof. Glorius, we have investigated N-heterocyclic carbenes for the functionalization of nanoparticles, opening the door to new nanoparticles catalysts. (Figure 3). We are also interested in anisotropic particles, which can self-assemble into unusual structures [see: Chem. Commun. 2014, 50, 3204; ACS Catal. 2015, 5, 5414; Angew. Chem. Int. Ed. 2016, 55, 5856–5860].

Currently, our group is composed of about 25 people. Our work is supported by the Westfälische Wilhelms-Universität Münster, Deutsche Forschungsgemeinschaft (DFG: Normalverfahren, SFB 858, TRR 61, Cells-in-Motion Cluster of Excellence), Verband der Chemischen Industrie e.V. (FCI), Deutsche Akademische Austausch Dienst (DAAD),  European Union and Volkswagen Foundation.

Please check the list of publications for the latest results from our group!