Photocleavable Anionic Glues for Light-Responsive Nanoparticle Aggregates

Abstract

Integrating light-sensitive molecules within nanoparticle (NP) assemblies is an attractive approach to fabricate new photoresponsive nanomaterials. Here, we describe the concept of photocleavable anionic glue (PAG): small trianions capable of mediating interactions between (and inducing the aggregation of) cationic NPs by means of electrostatic interactions. Exposure to light converts PAGs into dianionic products incapable of maintaining the NPs in an assembled state, resulting in light-triggered disassembly of NP aggregates. To demonstrate the proof-of-concept, we work with an organic PAG incorporating the UV-cleavable o-nitrobenzyl moiety and an inorganic PAG, the photosensitive trioxalatocobaltate(III) complex, which absorbs light across the entire visible spectrum. Both PAGs were used to prepare either amorphous NP assemblies or regular superlattices with a long-range NP order. These NP aggregates disassembled rapidly upon light exposure for a specific time, which could be tuned by the incident light wavelength or the amount of PAG used. Selective excitation of the inorganic PAG in a system combining the two PAGs results in a photodecomposition product that deactivates the organic PAG, enabling nontrivial disassembly profiles under a single type of external stimulus.

Traffic Lights for Catalysis: Stimuli‐Responsive Molecular and Extended Catalytic Systems

“…Stimuli‐responsive or “switchable” catalysis represents a rapidly expanding field due to its potential to alter the state‐of‐the‐art of organic synthesis on both the laboratory and industrial scales [1–10] . For example, the ability to alter reaction outcomes, including yield, selectivity, or enantiomeric excess, as well as the ability to switch between two distinct classes of organic transformations with a single catalyst will undoubtedly play a role in the next era of sustainable chemistry [1–38] . Indeed, precise control of reaction progress, intermediates, and product distribution through an accessible external stimulus offers an opportunity to minimize the energy and resources spent on unproductive reaction pathways resulting in undesirable by‐products.…”

Precision nanoengineering for functional self-assemblies across length scales

“…Importantly, over the past two decades, size and shape-controlled syntheses have allowed a range of stable noble metal nanoparticles, 35 providing routes for 3D crystals, 36 2D layered structures, 37 and elastic membranes. 38 More detailed theoretical insights and experimental approaches for MNP-based 1D, 2D, and 3D assemblies are beyond the scope of this article and have been discussed in several recent reviews.…”

Ampeln für die Katalyse: Stimulus‐reaktive molekulare und erweiterte katalytische Systeme

“…Die Stimuli‐reaktive oder “schaltbare” Katalyse ist ein zügig wachsendes Feld, da sie das Potenzial hat, den Stand der Technik in der organischen Synthese sowohl im Labor‐ als auch im industriellen Maßstab zu verändern [1–10] . So wird beispielsweise die Fähigkeit, die Reaktionsergebnisse zu verändern, einschließlich der Ausbeute, der Selektivität oder des Enantiomeren‐Überschusses, sowie die Fähigkeit, mit einem einzigen Katalysator zwischen zwei verschiedenen Klassen von organischen Reaktionen zu wechseln, zweifellos eine Rolle in der nächsten Ära der nachhaltigen Chemie spielen [1–38] . Die präzise Steuerung des Reaktionsverlaufs, der Zwischenprodukte und der Produktverteilung durch einen einfach zugänglichen externen Stimulus bietet die Möglichkeit, den Energie‐ und Ressourcenaufwand für Reaktionswege, die zu unerwünschten Nebenprodukten führen, zu minimieren.…”