1,720,976 research outputs found
Nanocomposites and Self-Assembled Structures via Controlled Radical Polymerization
No full textWe report recent findings on the formation of nanocomposites and self-assembled hybrid nanoarchitectures, in which controlled radical polymerization plays a key role. Specifically, we address how macromolecular design via these controlled methods can be used to flexibly guide the formation of hybrid nanoarchitectures in a rational and predetermined fashion. To this end, the role of polymeric architecture in tuning polymer/inorganic nanocomposite structures is examined
Tailoring nanocomposites using RAFT: Super-assemblies of gold nanoparticles and multiblock copolymers
No full textTailoring nanocomposites using RAFT: Super-assemblies of gold nanoparticles and multiblock copolymers
No full textGold-Planet–Silver-Satellite Nanostructures Using RAFT Star Polymer
No full textThe hierarchical self-assembly of distinct nanoelements into precisely ordered nanostructures requires efficient and flexible fabrication strategies. Herein, we report the precise fabrication of bimetallic gold-planet–silver-satellite nanoparticle-arrangements employing RAFT star polymers as particle linker connecting gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) with judiciously modified surface activity. The strengths of this approach include the adjustability of interparticle distances by tailoring the star polymer molar mass. The prepared nanoassemblies have well-defined structures in which a planet AuNP (∼13 nm) is encompassed by several satellite AgNPs (∼8 nm), thus incorporating the properties of both AuNPs and AgNPs, as confirmed by transmission electron microscopy and UV–vis spectra. Our results highlight the general applicability of RAFT star polymers as a nanosynthesis platform for synthesizing noble metal nanocomposites
Spherical Gold-Nanoparticle Assemblies with Tunable Interparticle Distances Mediated by Multifunctional RAFT Polymers
No full textA strategy for the controlled assembly of gold nanocrystals into dispersed three-dimensional superstructures is presented. A multifunctional RAFT agent was used to prepare multiblock polystyrene (4.4-17.8 kDa) with trithiocarbonate groups as junctions between the individual blocks. Addition of these polymers to two-phase Brust-Schiffrin gold nanoparticles (4.1 nm) resulted in the formation of stable gold-nanoparticle assemblies dispersed in toluene. TEM analysis revealed that the interparticle distances in these superstructures can be tuned over an unprecedented wide range by employing multiblock polymers with an adjusted degree of polymerization and thus tailored trithiocarbonate distances. Cross-linking of the gold nanoparticles in the assemblies by multifunctional trithiocarbonates was proven by AFM showing partly preserved globular shape after deposition on a solid substrate. The reported strategy is expected to prove useful when interparticle distances in nanoparticle assemblies need to be tuned in a liquid phase or on surfaces
Planet–Satellite Nanostructures Made To Order by RAFT Star Polymers
No full textThe investigation and application of complex nanostructures requires the hierarchical arrangement of distinct domains on a small scale. Herein, we report a method to prepare planet-satellite arrangements using RAFT polymers. Our approach is based on star polymers decorated with trithiocarbonate groups on their outer periphery that attach to gold surfaces and thus provide the polymer with the ability to connect (larger) gold nanoparticle planets with (smaller) gold nanoparticle satellites. By adjusting the molecular weight of the polymeric linker, nanostructures with tailored planet-satellite distances, as evidenced by transmission electron microscopy, are obtained. This strategy offers a straightforward way to prepare gold nanoparticle scaffolds with multiple reactive functionalities at defined distances from the central core.Fonds der Chemischen Industri
The Structure of Gold-Nanoparticle Networks Cross-Linked by Di- and Multifunctional RAFT Oligomers
No full textGold nanoparticle (AuNP) network structures featuring particles from the two-phase Brust-Schiffiin synthesis and linear RAFT oligomers of styrene with two and multiple trithiocarbonate (TTC) groups along their backbone have been investigated in detail. Insights into the internal structures of these particle networks could be obtained from small-angle X-ray scattering experiments, showing that primary AuNPs are cross linked by the employed molecular linker. The extent of AuNP network formation was investigated by means of dynamic light scattering and UV/visible extinction spectroscopy, showing an abrupt attenuation of network formation after a critical degree of polymerization of the cross-linker is exceeded. Analysis of transmission electron micrographs indicated a three-dimensional shape of the particle superstructures, which is evenly filled with the primary AuNPs. From the results obtained in this study, guidelines for the fabrication of nanoparticle networks from the self-assembly with macromolecular cross-linkers are suggested
Light-induced self-assembly of gold nanoparticles with a photoresponsive polymer shell
No full textThe light-induced self-assembly of gold nanoparticles was studied systematically. A methacrylic type monomer with an azobenzene sidechain was polymerized in a reversible addition–fragmentation chain transfer (RAFT) polymerization. The resulting light responsive polymer was grafted to gold nanoparticles via the RAFT group. UV-light induced trans to cis isomerization of the azobenzene moieties triggers the aggregation of the polymer–gold hybrid particles in toluene dispersion. The thermally induced cis to trans relaxation was found to be significantly slower than for small molecules at gold surfaces. The self-assembly was followed by dynamic light scattering (DLS), UV/vis spectroscopy and transmission electron microscopy (TEM). The density of primary gold particles within the self-assembled aggregates can be tuned by varying the molar mass of the grafted polymer
Stimulus-Responsive Planet–Satellite Nanostructures as Colloidal Actuators: Reversible Contraction and Expansion of the Planet–Satellite Distance
No full textStructural plasticity and its control at the nanoscale are a vivid area of material science. In this contribution, we report a conceptually simple and versatile strategy for the formation of reconfigurable nanoparticle arrangements. The key role in our approach is played by star block copolymers from controlled radical RAFT polymerization, which fulfill the dual task of guiding the particle arrangement and also of equipping the nanomaterials with stimulus-responsiveness. By virtue of their block structure, the star polymers provide at the same time colloidal stability and responsive properties. Structural switching in response to the applied stimulus was investigated by means of small-angle X-ray scattering and dynamic light scattering. The developed approach is general, easy to implement, and may provide new prospects for the development of colloidal actuators, nanoscale materials with switchable properties, and nanoscale machines
Prediction of Kinetically Stable Nanotheranostic Superstructures: Integral of First-Passage Times from Constrained Simulations
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