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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - NANOREACTOR (Multiscale modelling of stimuli-responsive nanoreactors)

Teaser

Summary

This project theoretically derives design rules for the optimization of nanoparticle catalysis by means of thermosensitive yolk-shell carrier systems. In the latter, the nanoparticle is stabilized in solution by an encapsulating, thermosensitive hydrogel shell.
The catalysis by metal nanoparticles is one of the fastest growing areas in nanoscience due to our society\'s exploding need for fuels, drugs, and environmental remediation. However, the optimal control of catalytic activity and selectivity remains one of the grand challenges in the 21st century. Responsive nanoreactors permit catalytic reaction to be switched and tuned, e.g., by the temperature or the pH. The novel hybrid character of these emerging \'nanoreactors\' opens up unprecedented ways for the control of nanocatalysis due to new designable degrees of freedom. The complex mechanisms behind stimuli-responsive nanocatalysis call for a concerted, interdisciplinary modelling approach, based on multiscale computer simulations of solvated polymers and the statistical and continuum mechanics of soft matter structures and dynamics. The key challenge is to integrate the molecular solvation effects and our growing knowledge of hydrogel mechanics and thermodynamics into advanced reaction-diffusion equations for a quantitative rate prediction. In addition, we envision exciting novel phenomena such as a chemo-mechanical \'self-regulated catalysis\' or an amplifying \'resonant catalysis\', if hydrogel response and fluctuations couple to the chemical output signal. The expected results and design principles will help our experimental collaborators to synthesize tailor-made, superior nanocatalysts for the increasing demand of our society for energy materials, fine chemicals and enviromental remediation.

Work performed

After assembling the ERC Team of 4 postdocs and 2 PhD-students we have dedicated our simulation and multiscale modeling work on the three NANOREACTOR work packages as planned.
The main results so far are the following: We have developed novel and optimized molecular models for computer simulation of responsive polymer hydrogels, including chemical cross-linkers. Preliminary simulations show
a high reactant selectivity of the hydrogels, in particular in their hydrophobic collapsed states and substantial permeability increase close to the hydrogel volume transition.
We additionally established new models that led to a description and better understanding of the coupling between hydrogel swelling and its volume transition and reactant permeation.
The knowledge of the response of the hydrogel to reactant adsorption and permeability is important for optimizing the nanoreactor function. Importantly, we have integrated this knowledge
into a full set of rate equations for bimolecular reactions in responsive nanoreactors in the diffusion-influenced reaction case. With new experiments coming up thus a full understanding
of the first prototypical nanoreactor based on model reactions is thus in reach. Then, the next substantial step, optimizing and guidance of nanoreactor synthesis based on theoretical insight,
can soon be made. So far the results were disseminated on over 10 conferences and published in 7 peer-reviewed publications.

Final results

We are converging to a full theoretical understanding of responsive nanoreactors for metal nanoparticle catalysis. The expected results and design principles will help our experimental collaborators to synthesize tailor-made, superior nanocatalysts for the increasing demand of our society for energy materials, fine chemicals and enviromental remediation.