Dual Cooperatively Grown J-aggregates with Different Nucleus Size.
Wenjing Shi1, Rong Wei1, Di Zhang1
1Beijing National Laboratory for Molecular Sciences, Chemistry, Center for the Soft Matter Science and Engineering and the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing, 100871, China.
Angewandte Chemie (International Ed. in English)
|July 17, 2022
Summary
This study reveals that cooling monomer solutions forms a less stable J-aggregate (J1) first, which then slowly transforms into a more stable J-aggregate (J2) due to differences in nucleus size and kinetics.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Physical Chemistry
Background:
- J-aggregates are crucial in various optical and electronic applications.
- Understanding the formation kinetics and thermodynamics of J-aggregates is key to controlling their properties.
- Cooperative growth of multiple J-aggregate types presents complex formation pathways.
Purpose of the Study:
- To investigate the formation mechanism of two distinct, cooperatively grown J-aggregates (J1 and J2).
- To elucidate the role of nucleus size and kinetic factors in the selective formation and transformation of J-aggregates.
- To understand the thermodynamic stability and kinetic control governing J-aggregate growth.
Main Methods:
- Controlled cooling of monomer solutions to induce J-aggregate formation.
- Variable-temperature spectroscopic analyses to monitor aggregate evolution.
- Mathematical simulations to validate proposed nucleation and growth models.
Main Results:
- The thermodynamically less stable J1 exclusively forms upon cooling, even at slow rates.
- J1 transforms into the more stable J2 at room temperature via slow kinetics.
- Nucleus size differences (smaller J1, larger J2) and monomer depletion explain the observed formation pathway and kinetics.
Conclusions:
- The formation pathway of J-aggregates is dictated by a balance between thermodynamic stability and kinetic accessibility.
- Entropy effects favor smaller nuclei formation at higher temperatures.
- Kinetic hindrance, due to monomer depletion by the less stable aggregate, controls the formation of the thermodynamically favored aggregate.
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