Redox‐Mediated Transient Reconfiguration of a Supramolecular Assembly

Fuel-Driven Enzymatic Reaction Networks to Program Autonomous Thiol/Disulfide Redox Systems

Fuel-driven dissipative formation of disulfide bonds using competing oxidative activation and reductive deactivation presents a possibly very versatile avenue for autonomous materials design. However, this is challenging to realize because of the direct annihilation of oxidizing fuel and a deactivating reducing agent. We overcome this challenge by introducing a redox-based enzymatic reaction network (ERN), enabling the dissipative disulfide formation for molecularly dissolved thiols in a fully autonomous manner. Moreover, the ERN allows for programming hydrogel lifetimes by utilizing thiol-terminated star polymers (sPEG-SH). The ERN can be customized to operate with aliphatic and aromatic thiols and should thus be broadly applicable to functional thiols.

Dynamic Timing Control of Molecular Photoluminescent Systems

Dynamic control of molecular photoluminescence offers chemical solutions to designing functional emissive materials. Although stimuli-switchable molecular luminescent systems are well established, how to encode these dynamic emissive systems with a "timing" feature, that is, time-dependent luminescent properties, remains challenging. This Concept aims to summarize the design principles of dynamic timing molecular photoluminescent systems by discussing the state-of-the-art of this topic and the shaping of fabrication strategies at both the molecular and supramolecular levels. An outlook and perspectives are given to outline the future opportunities and challenges in the rational design and potential applications of these smart emissive systems.

The Dissociation of Exciton During the Lasing of a Single CsPbBr3 Microplate

In this work, the lasing of a single CsPbBr₃ microplate (MP) fabricated with chemical vapor deposition (CVD) is investigated from the viewpoint of exciton dissociation characterized with steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL). It is confirmed that the lasing performance is disturbed by the dissociation of excitons. The increase of lasing threshold with temperature originates from the dissociation of free excitons (FEs) to localized carriers (LCs), and the lasing failure is mostly ascribed to the dissociation of FEs to free carriers (FCs). The working temperature of micro/nanolasers based on metal halide perovskites (MHPs) could be raised up to the temperature determined by exciton binding energy while the laser heating effect is dealt with well. These findings advance our understanding on the photophysics of the lasing behaviors of micro/nanocavities based on MHPs and help us promote their performance by having better thermal management.

Dynamic Timing Control over Multicolor Molecular Emission by Temporal Chemical Locking

Dynamic control over molecular emission, especially in a time-dependent manner, holds great promise for the development of smart luminescent materials. Here we report a series of dynamic multicolor fluorescent systems based on the time-encoded locking and unlocking of individual vibrational emissive units. The intramolecular cyclization reaction driven by adding chemical fuel acts as a chemical lock to decrease the conformational freedom of the emissive units, thus varying the fluorescence wavelength, while the resulting chemically locked state can be automatically unlocked by the hydrolysis reaction with water molecules. The dynamic molecular system can be driven by adding chemical fuels for multiple times. The emission wavelength and lifetime of the locking states can be readily controlled by elaborating the molecular structures, indicating this strategy as a robust and versatile way to modulate multi-color molecular emission in a time-encoded manner.

Droplet Formation by Chemically Fueled Self-Assembly: The Role of Precursor Hydrophobicity

We investigate active droplets that form at the expense of a chemical fuel in aqueous buffer and vanish autonomously. Dynamic light scattering reveals the scattered intensity, the hydrodynamic radius, and the width of the size distribution with high precision as well as high temporal and spatial resolutions. Comparing the resulting time-dependent behavior of the droplet characteristics with the time-dependent concentration of the anhydrides, the roles of the chemical reaction cycle and of colloidal growth processes are elucidated. The droplet sizes and lifetimes depend strongly on the hydrophobicity of the precursor, and the growth rate is found to correlate with the deactivation rate of the product.

Chemically fueled materials with a self-immolative mechanism: transient materials with a fast on/off response

There is an increasing demand for transient materials with a predefined lifetime like self-erasing temporary electronic circuits or transient biomedical implants. Chemically fueled materials are an example of such materials; they emerge in response to chemical fuel, and autonomously decay as they deplete it. However, these materials suffer from a slow, typically first order decay profile. That means that over the course of the material's lifetime, its properties continuously change until it is fully decayed. Materials that have a sharp on-off response are self-immolative ones. These degrade rapidly after an external trigger through a self-amplifying decay mechanism. However, self-immolative materials are not autonomous; they require a trigger. We introduce here materials with the best of both, i.e., materials based on chemically fueled emulsions that are also self-immolative. The material has a lifetime that can be predefined, after which it autonomously and rapidly degrades. We showcase the new material class with self-expiring labels and drug-delivery platforms with a controllable burst-release.

Parasitic behavior in competing chemically fueled reaction cycles

Non-equilibrium, fuel-driven reaction cycles serve as model systems of the intricate reaction networks of life. Rich and dynamic behavior is observed when reaction cycles regulate assembly processes, such as phase separation. However, it remains unclear how the interplay between multiple reaction cycles affects the success of emergent assemblies. To tackle this question, we created a library of molecules that compete for a common fuel that transiently activates products. Often, the competition for fuel implies that a competitor decreases the lifetime of these products. However, in cases where the transient competitor product can phase-separate, such a competitor can increase the survival time of one product. Moreover, in the presence of oscillatory fueling, the same mechanism reduces variations in the product concentration while the concentration variations of the competitor product are enhanced. Like a parasite, the product benefits from the protection of the host against deactivation and increases its robustness against fuel variations at the expense of the robustness of the host. Such a parasitic behavior in multiple fuel-driven reaction cycles represents a lifelike trait, paving the way for the bottom-up design of synthetic life.

A short critique on biomining technology for critical materials

Being around for several decades, there is a vast amount of academic research on biomining, and yet it contributes less to the mining industry compared to other conventional technologies. This critique briefly comments on the current status of biomining research, enumerates a number of primary challenges, and elaborates on some kinetically-oriented strategies and bottom-up policies to sustain biomining with focus on critical material extraction and rare earth elements (REEs). Finally, we present some edge cutting developments which may promote new potentials in biomining.

Active Bicomponent Nanoparticle Assembly with Temporal, Microstructural, and Functional Control

Transient supramolecular self-assembly has evolved as a tool to create temporally programmable smart materials. Yet, so far single-component self-assembly has been mostly explored. In contrast, multicomponent self-assembly provides an opportunity to create unique nanostructures exhibiting complex functional outcomes, newer and different than individual components. Even two-component can result in multiple organizations, such as self-sorted domains or co-assembled heterostructures, can occur, thus making it highly complex to predict and reversibly modulate these microstructures. In this study, we attempted to create active bicomponent nanoparticle assemblies of orthogonally pH-responsive-group-functionalized gold and cadmium selenide nanoparticles with temporal microstructural control on their composition (self-sorted or co-assembly) in order to harvest their emergent transient photocatalytic activity by coupling to temporal changes in pH. Moving towards multicomponent systems can deliver next level control in terms of structural and functional outcomes of supramolecular systems.

Synthesis of Complex Molecular Systems-The Foreseen Role of Organic Chemists

How to control the self-assembly of complex molecular systems is unknown. Yet, these complex molecular systems are fundamental for advances in material and biomedical sciences. A step forward is to transform one-step self-assembly into multistep synthesis involving covalent and noncovalent reactions. Key to this approach is to explore the chemical space at the frontiers of advanced covalent synthesis and supramolecular chemistry. Herein, we describe a selection of such reported cases and provide a guide for current limitations and insights for future directions. This outlook is meant to trigger collaborations between synthetic organic and supramolecular chemists, to expand the repertoire of organic syntheses working with supramolecular assemblies and thereby join forces to achieve stepwise emergence of molecular complexity in supramolecular systems.