Visible light photoflow synthesis of a Cu(ii) single-chain polymer nanoparticle catalyst

We herein pioneer the visible light (λ max = 410 nm) mediated flow synthesis of catalytically active single-chain nanoparticles (SCNPs). Our design approach is based on a copolymer of poly(ethylene glycol) methyl ether methacrylate and a photocleavable 2-((((2-nitrobenzyl)oxy)carbonyl)amino)ethyl methacrylate monomer which can liberate amine groups upon visible light irradiation, allowing for single-chain collapse via the complexation of Cu(ii) ions. We initially demonstrate the successful applicability of our design approach for the batch photochemical synthesis of Cu(ii) SCNPs and transfer the concept to photoflow conditions, enabling, for the first time, the continuous production of functional SCNPs. Critically, we explore their ability to function as a photocatalyst for the cleavage of carbon-carbon single and double bonds on the examples of xanthene-9-carboxylic acid and oleic acid, demonstrating the advantageous effect SCNPs can provide over analogous small molecule catalysts.

Open Linear Polymer Host-Guest Interactions Sensed by Luminescent Silver Nanodots

The selectivity of the linear polymer chain toward its binding moieties has been considered negligible; thus, a clear demonstration showing the best-fit binding of a linear polymer to its guest counterpart is still unknown. Luminescent poly(acrylic acid) (PAA)-stabilized silver nanodots (PAA-AgNDs) have been applied as a turn-on sensor to monitor the interaction between the PAA chain and its binding cations. The binding of cations ions to the PAA chain may cross-link the linear PAA chain via coordination with carboxylate, which increases the rigidity of the polymer chain, retards the nonradiative decay of PAA-AgNDs, and consequently enhances the emission of silver nanodots while inducing a blue-shift of its emission spectrum. For the first time, we have demonstrated that a linear polymer chain can act as an open host to selectively bind to its best-matching cations. Specifically, among Group 2 cations (Mg2+, Ca2+, Sr2+, Ba2+), calcium ions show the strongest bonding to the PAA polymer chain. Our research suggests that, with extra rigidity, the polymer improves its chemical stability as calcium ions cross-linked the linear polymer. Meanwhile, it has also been demonstrated that luminescent silver nanodots can be excellent probes for the detection of polymer activities with straightforward and simple visualization methods.

Polymer-Tethered Nanoparticles: From Surface Engineering to Directional Self-Assembly

ConspectusCurrent interest in nanoparticle ensembles is motivated by their collective synergetic properties that are distinct from or better than those of individual nanoparticles and their bulk counterparts. These new advanced optical, electronic, magnetic, and catalytic properties can find applications in advanced nanomaterials and functional devices, if control is achieved over nanoparticle organization. Self-assembly offers a cost-efficient approach to produce ensembles of nanoparticles with well-defined and predictable structures. Nanoparticles functionalized with polymer molecules are promising building blocks for self-assembled nanostructures, due to the comparable dimensions of macromolecules and nanoparticles, the ability to synthesize polymers with various compositions, degrees of polymerization, and structures, and the ability of polymers to self-assemble in their own right. Moreover, polymer ligands can endow additional functionalities to nanoparticle assemblies, thus broadening the range of their applications.In this Account, we describe recent progress of our research groups in the development of new strategies for the self-assembly of nanoparticles tethered to macromolecules. At the beginning of our journey, we developed a new approach to patchy nanoparticles and their self-assembly. In a thermodynamically driven strategy, we used poor solvency conditions to induce homopolymer surface segregation in pinned micelles (patches). Patchy nanoparticles underwent self-assembly in a well-defined and controlled manner. Following this work, we overcame the limitation of low yield of the generation of patchy nanoparticles, by using block copolymer ligands. For block copolymer-capped nanoparticles, patch formation and self-assembly were "staged" by using distinct stimuli for each process. We expanded this work to the generation of patchy nanoparticles via dynamic exchange of block copolymer molecules between the nanoparticle surface and micelles in the solution. The scope of our work was further extended to a series of strategies that utilized the change in the configuration of block copolymer ligands during nanoparticle interactions. To this end, we explored the amphiphilicity of block copolymer-tethered nanoparticles and complementary interactions between reactive block copolymer ligands. Both approaches enabled exquisite control over directional and self-limiting self-assembly of complex hierarchical nanostructures. Next, we focused on the self-assembly of chiral nanostructures. To enable this goal, we attached chiral molecules to the surface of nanoparticles and organized these hybrid building blocks in ensembles with excellent chiroptical properties. In summary, our work enables surface engineering of polymer-capped nanoparticles and their controllable and predictable self-assembly. Future research in the field of nanoparticle self-assembly will include the development of effective characterization techniques, the synthesis of new functional polymers, and the development of environmentally responsive self-assembly of polymer-capped nanoparticles for the fabrication of nanomaterials with tailored functionalities.

Nanoengineering with RAFT polymers: from nanocomposite design to applications

Reversible addition–fragmentation chain-transfer (RAFT) polymerization is a powerful tool for the precise formation of macromolecular building blocks that can be used for the construction of well-defined nanocomposites.

Heterobimetallic Eu(iii)/Pt(ii) single-chain nanoparticles: a path to enlighten catalytic reactions

We introduce the formation and characterization of heterometallic single-chain nanoparticles entailing both catalytic and luminescent properties. A terpolymer containing two divergent ligand moieties, phosphines and phosphine oxides, is synthesized and intramolecularly folded into nanoparticles via a selective metal complexation of Pt(ii) and Eu(iii). The formation of heterometallic Eu(iii)/Pt(ii) nanoparticles is evidenced by size exclusion chromatography, multinuclear NMR (1H, 31P{1H}, 19F, 195Pt) as well as diffusion-ordered NMR and IR spectroscopy. Critically, we demonstrate the activity of the SCNPs as a homogeneous and luminescent catalytic system in the amination reaction of allyl alcohol.

Nanofabrication within unimolecular nanoreactors

Nanoparticles (NPs) have been a research focus over the last three decades owing to their unique properties and extensive applications. It is crucial to precisely control the features of NPs including topology, architecture, composition, size, surface and assembly because these features will affect their properties and then applications. Ingenious nanofabrication strategies have been developed to precisely control these features of NPs, especially for templated nanofabrication within predesigned nanoreactors. Compared with conventional nanoreactors (hard templates and supramolecular nanoreactors), unimolecular nanoreactors exhibit (1) covalently stable nanostructures uninfluenced by environmental variations, (2) extensively regulated features of the structure including topology, composition, size, surface and valence due to the rapid development of polymer chemistry, and (3) effective encapsulation of abundant guests with or without strong interaction to achieve the function of loading, delivery and conversion of guests. Thus, unimolecular nanoreactors have shown fascinating prospects as templates for nanofabrication. Various NPs with expected topologies (sphere, rod, tube, branch, and ring), architectures (compact, hollow, core-shell, and necklace-like), compositions (metal, metal oxide, semiconductor, doping, alloy, silica, and composite), sizes (generally 1-100 nm), surface properties (hydrophilic, hydrophobic, reactivity, valence and responsivity) and assemblies (oligomer, chain, and aggregate) can be fabricated easily within reasonably designed unimolecular nanoreactors in a programmable way. In this review, we provide a brief introduction of the properties and types of unimolecular nanoreactors, a condensed summary of representative methodologies of nanofabrication within various unimolecular nanoreactors and a predicted outlook of the potential further developments of this charming nanofabrication approach.

Pushing the limits of single chain compaction analysis by observing specific size reductions via high resolution mass spectrometry

Herein, we push the limits of single chain nanoparticle analysis to directly observe the specific compaction of defined single chains dependent on the number of compaction steps.

A dimolybdenum paddlewheel as a building block for heteromultimetallic structures

A series of heteromultimetallic complexes, containing a Mo₂⁴⁺core unit, were synthesized based on a bifunctional phosphine–carboxylic acid ligand system, leadingi.e.to the formation of supramolecular structuresviaaurophilic interactions.

Strengths and limitations of size exclusion chromatography for investigating single chain folding – current status and future perspectives

Synthetic approaches for Single-Chain Nanoparticles (SCNPs) developed rapidly during the last decade, opening a multitude of avenues for the design of functional macromolecular chains able to collapse into defined nanoparticles. However, the analytical evaluation of the SCNP formation process still requires critical improvements.