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Thin films made of deformable micro‐ and nano‐units, such as biological membranes, polymer interfaces, and particle‐laden liquid surfaces, exhibit a complex behavior during drying, with consequences for various applications like wound healing, coating technologies, and additive manufacturing. Studying the drying dynamics and structural changes of soft colloidal films thus holds the potential to yield valuable insights to achieve improvements for applications. In this study, interfacial monolayers of core‐shell (CS) microgels with varying degrees of softness are employed as model systems and to investigate their drying behavior on differently modified solid substrates (hydrophobic vs hydrophilic). By leveraging video microscopy, particle tracking, and thin film interference, this study shed light on the interplay between microgel adhesion to solid surfaces and the immersion capillary forces that arise in the thin liquid film. It is discovered that a dried replica of the interfacial microstructure can be more accurately achieved on a hydrophobic substrate relative to a hydrophilic one, particularly when employing softer colloids as opposed to harder counterparts. These observations are qualitatively supported by experiments with a thin film pressure balance which allows mimicking and controlling the drying process and by computer simulations with coarse‐grained models. [ABSTRACT FROM AUTHOR]

Polythiophene‐based conjugated polyelectrolytes (CPE) are attracting increasing attention as sensor or interface materials in chemistry and biology. While cationic polythiophenes are better understood, limited structural information is available on their anionic counterparts. Limited access to well‐defined polymers has made the study of structure‐property relationships difficult and clear correlations have remained elusive. By combining controlled Kumada catalyst transfer polymerization with a polymer‐analog substitution, regioregular and narrowly distributed poly(6‐(thiophen‐3‐yl)hexane‐1‐sulfonate)s (PTHS) with tailored chain length are prepared. Analysis of their aqueous solution structures by small‐angle neutron scattering (SANS) revealed a cylindrical conformation for all polymers tested, with a length close to the contour length of the polymer chains, while the estimated radii remain too small (<1.5 nm) for extensive π‐stacking of the chains. The latter is particularly interesting as the longest polymer exhibits a concentration‐independent structured absorption typical of crystalline polythiophenes. Increasing the ionic strength of the solution diminishes these features as the Coulomb repulsion between the charged repeat units is shielded, allowing the polymer to adopt a more coiled conformation. The extended π‐conjugation, therefore, appears to be a key parameter for these unique optical features, which are not present in the corresponding cationic polythiophenes. [ABSTRACT FROM AUTHOR]

In recent years, hydrogel‐based soft materials with hybrid properties have found widespread use in various technological fields, including tissue engineering, soft actuators, and flexible electronics. The proper implementation of these smart multifunctional materials into real‐world applications requires the development of simple, cost‐effective, and large‐scale fabrication methods. Herein, a simple compression‐ and colloid‐based method is presented to fabricate responsive Au‐poly(N‐isopropylacrylamide) (pNIPAM) hybrid films using photopolymerizable resin containing Au‐pNIPAM core–shell microgels as building blocks. Uniform Au‐pNIPAM hybrid films of 25 × 25 mm with adjustable thickness in the micron‐size range (2.3–1.2 µm) w ere successfully fabricated on glass substrates and flexible commercial acetate sheets. The resulting flexible Au‐pNIPAM films exhibit robust optical and mechanical properties, even after repeated edge‐to‐edge bending cycle tests. Additionally, using patterned light to polymerize the Au‐pNIPAM films allows synthesizing of anisotropic Au‐pNIPAM microgels with high width‐to‐height aspect ratios, such as square, circular, and rectangular microgels, adding a new dimension to the proposed fabrication method. [ABSTRACT FROM AUTHOR]

We report the formation of metal‐organic cage‐crosslinked polymer hydrogels. To enable crosslinking of the cages and subsequent network formation, we used homodifunctionalized poly(ethylene glycol) (PEG) chains terminally substituted with bipyridines as ligands for the Pd6L4 corners. The encapsulation of guest molecules into supramolecular self‐assembled metal‐organic cage‐crosslinked hydrogels, as well as ultrasound‐induced disassembly of the cages with release of their cargo, is presented in addition to their characterization by nuclear magnetic resonance (NMR) techniques, rheology, and comprehensive small‐angle X‐ray scattering (SAXS) experiments. The constrained geometries simulating external force (CoGEF) method and barriers using a force‐modified potential energy surface (FMPES) suggest that the cage‐opening mechanism starts with the dissociation of one pyridine ligand at around 0.5 nN. We show the efficient sonochemical activation of the hydrogels HG3–6, increasing the non‐covalent guest‐loading of completely unmodified drugs available for release by a factor of ten in comparison to non‐crosslinked, star‐shaped assemblies in solution. [ABSTRACT FROM AUTHOR]

The unique corona structure of surface‐compartmentalized micelles (Janus micelles, patchy micelles) opens highly relevant applications, e.g. as efficient particulate surfactants for emulsion stabilization or compatibilization of polymer blends. Here, stereocomplex‐driven self‐assembly (SCDSA) as a facile route to micelles with a semicrystalline stereocomplex (SC) core and a patch‐like microphase separated corona, employing diblock copolymers with enantiomeric poly(L‐lactide)/poly(D‐lactide) blocks and highly incompatible corona‐forming blocks (polystyrene (PS), poly(tert‐butyl methacrylate)) is introduced. The spherical patchy SC micelles feature a narrow size distribution and show a compartmentalized, shamrock‐like corona structure. Compared to SC micelles with a homogeneous PS corona the patchy micelles have a significantly higher interfacial activity attributable to the synergistic combination of an amphiphilic corona with the Pickering effect of nanoparticles. The patchy micelles are successfully employed in the stabilization of emulsions, underlining their application potential. [ABSTRACT FROM AUTHOR]

Micron-sized hard core-soft shell hybrid microgels are promising model systems for studies of soft matter as they enable in-situ optical investigations and their structures/morphologies can be engineered with a great variety. Yet, protocols that yield micron-sized core-shell microgels with a tailorable shell-to-core size ratio are rarely available. In this work, we report on the one-pot synthesis protocol for micron-sized silica-poly(N-isopropylacrylamide) core-shell microgels that has excellent control over the shell-to-core ratio. Small-angle light scattering and microscopy of 2- and 3-dimensional assemblies of the synthesized microgels confirm that the produced microgels are monodisperse and suitable for optical investigation even at high packing fractions. [ABSTRACT FROM AUTHOR]

Seeded precipitation polymerization is one of the most versatile techniques for the synthesis of solid core–hydrogel shell particles, and it is required to control the shell structure, which plays an important role in functionalization. In this study, the effect of the polymerization conditions, such as the monomer and cross-linker concentrations, on the structure of the shell layer was systematically investigated. A series of experiments revealed that the lack of cross-linking points at low monomer concentrations and the formation of secondary particles at high monomer concentrations hindered the introduction of shells onto the core particles. The dependence of the monomer concentration on the shell thickness was well described by a single-exponential equation, and thus, the required concentrations of monomer and cross-linker to prepare a target thickness/cross-linking density can be predicted. Moreover, the combination of seeded precipitation polymerization and the monomer feeding method allowed further control of the shell thickness. [ABSTRACT FROM AUTHOR]

A versatile amphiphilic pyrano[2,3-b]indole for halochromic turn-ON luminescence in acidic or basic media is accessed by an insertion-coupling-cycloisomerization and adjusting solubilizing and phenolic functionalities. While almost non-emissive in neutral solutions, treatment with acids or bases like trifluoroacetic acid (TFA) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) reveals distinct luminescence at wavelengths of 540 nm or 630 nm in propan-2-ol, respectively. Turn-ON emission can be detected at pH values as mild as pH = 5.31 or 8.70. Quantum yields in propan-2-ol are substantial for protonated (Φf = 0.058) and deprotonated (Φf = 0.059) species. Photometrically, pKa1 of 3.5 and pKa2 of 10.5 were determined in propan-2-ol. With lipophilic polyether sidechains and hydrophilic protonation and deprotonation sites the molecule can be regarded as amphipolar, which results in good solubility properties for different organic solvents. In aqueous media, an organic co-solvent like propan-2-ol (35%) or tetrahydrofuran (25%) is needed, and the solution can be diluted with pure water without precipitation of the compound. At higher concentrations of water, a turbid solution is formed, which indicates the formation of micellar structures or clusters. With dynamic light scattering we could show that these clusters increase in size with increasing water content. [ABSTRACT FROM AUTHOR]

Surface lattice resonances appear in periodic plasmonic nanoparticle arrays due to the hybridization of plasmonic and photonic modes. Compared to localized surface plasmon resonances of single particles, these coupled modes feature reduced linewidth, angle‐dependent dispersion, and long‐range collectivity. Here, the optical response of self‐assembled plasmonic monolayers of periodically arranged gold and silver nanoparticles is studied. In comparison to already established hexagonal lattices, self‐templated honeycomb and Moiré type lattices as well as their binary counterparts that include silver and gold nanoparticles in the same monolayer are looked at. All periodic arrays feature macroscopic dimensions (cm‐scale) and support surface lattice resonances as evidenced from classical extinction measurements. The experimental findings are supported by results from finite difference time domain simulations. Variation of the plasmonic material, the lattice spacing, and geometry enables spectral tunability of the optical response of the lattices. [ABSTRACT FROM AUTHOR]

Noble metal nanoparticles can absorb incident light very efficiently due to their ability to support localized surface plasmon resonances (LSPRs), collective oscillations of the free electron cloud. LSPRs lead to strong, nanoscale confinement of electromagnetic energy which facilitates applications in many fields including sensing, photonics, or catalysis. In these applications, damping of the LSPR caused by inter‐ and intraband transitions is a limiting factor due to the associated energy losses and line broadening. The losses and broad linewidth can be mitigated by arranging the particles into periodic lattices. Recent advances in particle synthesis, (self‐)assembly, and fabrication techniques allow for the realization of collective coupling effects building on various particle sizes, geometries, and compositions. Beyond assemblies on static substrates, by assembling or printing on mechanically deformable surfaces a modulation of the lattice periodicity is possible. This enables significant alteration and tuning of the optical properties. This progress report focuses on this novel approach for tunable spectroscopic properties with a particular focus on low‐cost and large‐area fabrication techniques for functional plasmonic lattices. The report concludes with a discussion of the perspectives for expanding the mechanotunable colloidal concept to responsive structures and flexible devices. [ABSTRACT FROM AUTHOR]

Control over microstructure and interparticle spacing in substrate-supported colloidal arrangements is a key challenge in colloidal self-assembly. We demonstrate here the preparation of Moiré and honeycomb monolayer lattices from core/shell microgels with rigid inorganic cores and soft, deformable hydrogel shells. These structures were realized by the sequential double deposition of freely floating monolayers from the air/water interface onto the same, centimetre-scale substrate. Due to the soft and deformable character of the hydrogel shells, the second applied monolayer fully settles into the same plane as the first monolayer. The resulting structural motif is determined by the drying conditions applied to the second deposition step. We support our experimental findings by Brownian dynamics simulations and provide insights into the structure formation process. [ABSTRACT FROM AUTHOR]

Nanocomposites made of stacked‐cup carbon nanotubes coated with NiO (NiO/SCCNTs) via atomic layer deposition (ALD) were synthesized in order to obtain a material exhibiting enhanced and optimized electrochemical performance towards detections of glucose. The structure and morphology were characterized by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). NiO deposited as nanocrystalline particles in the cubic modification, were well dispersed and directly anchored on SCCNTs forming a smooth particulate thin film, which becomes more dense with the increase of the number of ALD cycles. The NiO/SCCNTs samples with various thicknesses of the NiO coating (0.8 nm, 1.7 nm, 4.0 nm, 6.5 nm, 14.0 nm and 21.8 nm) were applied for enzyme‐free glucose sensing. Their electrochemical performance strongly depends on the thickness of the deposited NiO thin film. The best performing glucose sensors respond over a wide concentration range from 2 μM to 2.2 mM (R2=0.9979) with remarkably enhanced sensitivity (1252.3 μA cm−2 mM−1), with a limit of detection (LOD) of 0.10 μM (S/N=3) and with a fast response time (lower than 2 s). The significant performance improvement can be attributed to the conformal NiO coating, high surface to volume ratio and to the optimized thickness of the NiO thin film. The advantage of our sensors is also associated with the conductive supporting material (SCCNTs), simplicity of fabrication, high sensitivity, selectivity, stability and reproducibility for the rapid quantification of glucose. Ain't it sweet? Conductive stacked‐cup carbon nanotubes are conformally coated with NiO of variable thicknesses using atomic layer deposition (ALD). Their electrochemical performance towards glucose oxidation strongly depends on the thickness of the deposited NiO thin film. The NiO/SCCNTs electrode with 4.0 nm thickness of NiO exhibits the highest sensitivity and stability. The very thin NiO layer also protects the underneath SCCNT substrate from corrosion. [ABSTRACT FROM AUTHOR]

The control of the distribution of colloidal particles in microfluidic flows plays an important role in biomedical and industrial applications. A particular challenge is to induce cross-streamline migration in laminar flows, enabling the separation of colloidal particles according to their size, shape or elasticity. Here we show that viscoelastic fluids can mediate cross-streamline migration of deformable spherical and cylindrical colloidal particles in sinusoidal microchannels at low Reynolds numbers. For colloidal streams focused into the center of the channel entrance this leads to a symmetric stream-splitting and separation into four substreams. The degree of stream splitting and separation can be controlled via the flow rates, viscoelasticity of the focusing fluid, and the spatial microchannel modulation with an upper limit when reaching the microchannel walls. We demonstrate that this effect can be used to separate flexible particles of different size and shape. This methodology of cross-stream migration has thus great potential for the passive separation of colloids and cells in microfluidic channels. [ABSTRACT FROM AUTHOR]

Acidochromic turn‐on 2,4‐diarylpyrano[2, 3‐b]indole luminophores with different solubilizing groups are readily synthesized in a two‐step process, consisting of a Pd−Cu‐catalyzed domino insertion‐coupling‐cycloisomerization reaction of alkynoyl ortho‐iodo anilides and terminal arylacetylenes furnishing the chromophore, and a desilylation‐alkylation sequence of the 2‐TMS‐ethylthio functionality for introducing solubilizing moieties, i. e. polar and aliphatic swallowtails as well as propylsulfonate potassium. These title compounds are able to cover a broad spectrum of solubility in nonpolar to polar and even aqueous solvent systems. Indeed, the turn‐on fluorescence can be shown to proceed without precipitation in aqueous solvent systems. In addition, a selected pyrano[2, 3‐b]indole forms clusters of 127 nm diameter at high water concentrations as determined by dynamic light scattering. A Pd−Cu‐catalyzed domino insertion‐coupling‐cycloisomerization reaction furnishes the 2,4‐diaryl‐pyrano[2, 3‐b]indole chromophore, and by desilylation‐alkylation sequence solubilizing polar and aliphatic swallowtails as well as propyl‐sulfonate potassium moieties are introduced. A pyrano‐[2, 3‐b]indole forms clusters of 127 nm diameter at high water concentrations as shown by dynamic light scattering. [ABSTRACT FROM AUTHOR]

Abstract: The stabilization of crystal phases and nanostructured morphologies is an essential topic in application‐driven design of mesoporous materials. Many applications, e.g. catalysis, require high temperature and humidity. Typical metal oxides transform under such conditions from a metastable, low crystalline material into a thermodynamically more favorable form, i.e. from ferrihydrite into hematite in the case of iron oxide. The harsh conditions induce also a growth of the crystallites constituting pore walls, which results in sintering and finally collapse of the porous network. Herein, a new method to stabilize mesoporous templated metal oxides against sintering and pore collapse is reported. The method employs atomic layer deposition (ALD) to coat the internal mesopore surface with thin layers of either alumina or silica. The authors demonstrate that silica exerts a very strong influence: It shifts hematite formation from 400 to 600 °C and sintering of hematite from 600 to 900 °C. Differences between the stabilization via alumina and silica are rationalized by a different interaction strength between the ALD material and the ferrihydrite film. The presented approach allows to stabilize mesoporous thin films that require a high crystallization temperature, with submonolayer quantity of an ALD material, and to apply mesoporous materials for high temperature applications. [ABSTRACT FROM AUTHOR]

Abstract: Two phenanthroline‐derived Schiff base‐like ligands with a covalently linked ruthenium(II) phosphorescent unit were synthesised and converted into bimetallic RuII–NiII complexes. The optical properties were studied to examine a possible photoluminescence quenching through a nonradiative energy‐transfer upon a coordination‐induced spin‐state switch (CISSS) at the nickel(II) centre. Therefore, the metalloligands and the nickel(II) complexes were studied using UV/Vis absorbance, steady‐state, and time‐resolved emission spectroscopy in solutions of MeCN and pyridine. It is demonstrated that the nature of the bridging ligand between the ruthenium(II) donor and the nickel(II) acceptor strongly influences the photophysical behaviour upon CISSS. For the complex with a phenazine bridge, photoluminescence quenching is observed in the presence of a paramagnetic nickel(II) centre. [ABSTRACT FROM AUTHOR]

Glyco-functionalized gold nanoparticles have great potential as biosensors and as inhibitors due to their increased binding to carbohydrate-recognizing receptors such as the lectins. Here we apply previously developed solid phase polymer synthesis to obtain a series of precision glycomacromolecules that allows for straightforward variation of their chemical structure as well as functionalization of gold nanoparticles by ligand exchange. A novel building block is introduced allowing for the change of spacer building blocks within the macromolecular scaffold going from an ethylene glycol unit to an aliphatic spacer. Furthermore, the valency and overall length of the glycomacromolecule is varied. All glyco-functionalized gold nanoparticles show high degree of functionalization along with high stability in buffer solution. Therefore, a series of measurements applying UV-Vis spectroscopy, dynamic light scattering (DLS) and surface plasmon resonance (SPR) were performed studying the aggregation behavior of the glyco-functionalized gold nanoparticles in presence of model lectin Concanavalin A. While the multivalent presentation of glycomacromolecules on gold nanoparticles (AuNPs) showed a strong increase in binding compared to the free ligands, we also observed an influence of the chemical structure of the ligand such as its valency or hydrophobicity on the resulting lectin interactions. The straightforward variation of the chemical structure of the precision glycomacromolecule thus gives access to tailor-made glyco-gold nanoparticles (glyco-AuNPs) and fine-tuning of their lectin binding properties. [ABSTRACT FROM AUTHOR]

Nanocomposites are an important materials class, which strives to foster synergistic effects from the intimate mixture of two vastly different materials. Inorganic nanoparticles decorated with polymer ligands, for instance, aim to combine the processing flexibility of polymers with the mechanical robustness of solid state materials. The fabrication and purification of such composite nanoparticles, however, still presents a synthetic challenge. Here, we present a simple synthesis of silver polystyrene nanocomposites with a controllable interparticle distance. The interparticle distance can be well-controlled with a few nanometer precision using polystyrene ligands with various molecular weights. The nanoparticle and polymer ligand synthesis yield both materials on gram scales. Consequently, the polymer nanocomposites can also be fabricated in such large amounts. Most importantly, we introduce Q-centrifugation as a purification method, which is capable of purifying large nanocomposite batches in a reproducible manner. We employ a range of characterization methods to prove the successful purification procedure, such as transmission electron microscopy, thermogravimetric analysis, and dynamic light scattering. Our contribution will be of high interest for many groups working on nanocomposite materials, where the sample purification has been a challenge up to now. [ABSTRACT FROM AUTHOR]

Colloidal self-assembly merges the flexibility provided by (wet-chemical) colloid synthesis and the structural diversity offered by self-assembly. Using plasmonic nanocrystals as colloidal building blocks, this enables the fabrication of plasmonic superstructures that show optical response superior to the individual colloid properties. In this review, we highlight recent examples of colloidal monolayers featuring coupled plasmonic resonances. Depending on the average inter-particle distance and the structure of such monolayers, the discussed examples show either near-field or radiative coupling signatures depending on the critical interference length scale of the localized resonances. In addition, templated assembly is highlighted as a pathway for the preparation of monolayers that show anisotropic optical coupling. The collected works not only reflect the recent state of the art in plasmonic resonance engineering in self-assembled monolayers, but also point to future directions relevant for their use in nanophotonic applications such as plasmonic lasing. [ABSTRACT FROM AUTHOR]

In this work we investigate the salt-induced cluster formation of monodisperse, spherical gold nanoparticles possessing negative surface charge. Time dependent dynamic light scattering was used to determine the critical coagulation concentration and to study the kinetics of cluster growth. Cryo-TEM as well as small angle X-ray scattering allowed to obtain insights into the cluster morphology at various salt concentrations. The time dependent cluster growth was monitored by stopped-flow small angle X-ray scattering experiments and UV-Visible extinction measurements simultaneously. Our results reveal the transition from reaction limited cluster aggregation (RLCA) at low salt concentrations to diffusion limited cluster aggregation (DLCA) at high salt concentrations. We were able to correlate changes of the plasmon resonance position of the gold nanoparticles to the cluster size. By comparison to theoretical calculations using Mie theory, we found indication that stronger resonance shifts during cluster growth can be related to smaller inter-particle spacings. [ABSTRACT FROM AUTHOR]

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Heterogeneous catalysis with supported nanoparticles (NPs) is a highly active field of research. However, the efficient stabilization of NPs without deteriorating their catalytic activity is challenging. By combining top-down (coaxial electrospinning) and bottom-up (crystallization-driven self-assembly) approaches, we prepared patchy nonwovens with functional, nanometer-sized patches on the surface. These patches can selectively bind and efficiently stabilize gold nanoparticles (AuNPs). The use of these AuNP-loaded patchy nonwovens in the alcoholysis of dimethylphenylsilane led to full conversion under comparably mild conditions and in short reaction times. The absence of gold leaching or a slowing down of the reaction even after ten subsequent cycles manifests the excellent reusability of this catalyst system. The flexibility of the presented approach allows for easy transfer to other nonwoven supports and catalytically active NPs, which promises broad applicability. [ABSTRACT FROM AUTHOR]

Herein, we fabricate hollow silica nanoparticles with exceptionally narrow size distributions that inherently possess two distinct length scales-tens of nanometers with regards to the shell thickness, and hundreds of nanometers in regards to the total diameter. We characterize these structures using dynamic and static light scattering (DLS and SLS), small angle X-ray scattering (SAXS), and transmission electron microscopy (TEM), and we demonstrate quantitative agreement among all methods. The ratio between the radius of gyration (SLS) and hydrodynamic radius (DLS) in these particles equals almost unity, corresponding to ideal capsule behavior. We are able to resolve up to 20 diffraction orders of the hollow sphere form factor in SAXS, indicating a narrow size distribution. Data from light and X-ray scattering can be combined to a master curve covering a q-range of four orders of magnitude assessing all hierarchical length scales of the form factor. The measured SLS intensity profiles noticeably change when the scattering contrast between the interior and exterior is altered, whereas the SAXS intensity profiles do not show any significant change. Tight control of the aforementioned length scales in one simple and robust colloidal building block renders these particles suitable as future calibration standards. [ABSTRACT FROM AUTHOR]

The encapsulation of inorganic nanoparticles by hydrogel shells offers a promising pathway toward the design of functional building blocks for manifold applications. Hydrogel shells can be grown in a broad range of thicknesses, from a few tens to several hundreds of nanometer, allowing for encapsulation of inorganic particles with different composition, size, and shape. This gives access to a diverse toolbox of colloidal building blocks, which combine properties of the individual components in a multifunctional fashion. Hydrogel shells provide the nano­particle cores with transparent, soft, and responsive coatings which improve the colloidal stability and allow interparticle distance control in colloidal assembly. The variation of the shell dimensions gives access to controlling the fill factor and ultimately distance-dependent effects such as plasmon resonance coupling. This article summarizes the latest efforts in the preparation of core-shell colloids with different inorganic cores and hydrogel shells of various morphologies as well as the assembly of these building blocks into functional superstructures. It is demonstrated how the level of complexity can be increased from 1D to 3D by chemical treatment of core-shell particles, i.e., core growth or core removal, and template-free as well as template-assisted assembly leading to isotropic and anisotropic arrangements of particles. [ABSTRACT FROM AUTHOR]

Polymer encapsulation is an important pathway to stabilize inorganic nanoparticles, allow their phase transfer to different media, and access inter-particle distance control in particle assembly. In the past, hydrogels were shown to be a versatile encapsulation material offering rather thick polymeric shells through free radical precipitation polymerization. In this work, we systematically investigate the influence of nanoparticle surface functionalization and concentration on the formation of core-shell microgels. Spherical gold nanoparticles are used as seeds in the radical polymerization of N-isopropylacrylamide and N, N′-methylenebisacrylamide. We find that the encapsulation occurs via precipitation of oligomers/polymers onto the seed particle surface, independent of the presence of polymerizable groups. Furthermore, we identify the seed concentration regime where almost exclusively core-shell particles are formed. In this concentration range, the hydrogel thickness is precisely controllable by the amount of seeds. Monitoring the polymerizations in situ by dynamic light scattering and absorbance spectroscopy provides first insights into the encapsulation mechanism and its time dependence. [ABSTRACT FROM AUTHOR]

We demonstrate the large-scale organisation of anisotropic nanoparticles into linear assemblies displaying optical anisotropy on macroscopic areas. Monodisperse gold nanorods with a hydrophilic protein shell are arranged by dip-coating on wrinkled surfaces and subsequently transferred to indium tin oxide (ITO) substrates by capillary transfer printing. We elucidate how tuning the wrinkle amplitude enables us to precisely adjust the assembly morphology and fabricate single, double and triple nanorod lines. For the single lines, we quantify the order parameter of the assemblies as well as interparticle distances from scanning electron microscopy (SEM) images. We find an order parameter of 0.97 and a mean interparticle gap size of 7 nm. This combination of close to perfect uni-axial alignment and close-packing gives rise to pronounced macroscopic anisotropic optical properties due to strong plasmonic coupling. We characterise the optical response of the assemblies on ITO-coated glass via UV/vis/NIR spectroscopy and determine an optical order parameter of 0.91. The assemblies are thus plasmonic metamaterials, as their periodicity and building block sizes are well below the optical wavelength. The presented approach does not rely on lithographic patterning and provides access to functional materials, which could have applications in subwavelength waveguiding, photovoltaics, and for large-area metamaterial fabrication. [ABSTRACT FROM AUTHOR]

Unique doubly temperature-responsive hollow microgels are presented. These consist of two concentric thermoresponsive polymer shells made of poly( N-isopropylacrylamide) (PNIPAM) and poly( N-isopropylmethacrylamide) (PNIPMAM), respectively. The hollow particles are derived from silica-PNIPAM-PNIPMAM core-shell-shell (CSS) particles by dissolution of the silica core. Light scattering measurements reveal the twofold volume phase transition behavior that occur in the PNIPAM and PNIPMAM regions of the CSS and the respective hollow particles. In the presence of the silica core, i.e., in case of the CSS particles, the swelling of the inner shell is tremendously restricted by the core. However, after the core is dissolved, the transition of the inner shell from the swollen to the collapsed state is highly pronounced. This versatile approach allows preparing hollow particles with individually tunable properties on the particle inside and outside for various applications as multifunctional smart materials. [ABSTRACT FROM AUTHOR]

Coating metal nanocrystals with responsive polymers provides a model case of smart, functional materials, where the optical properties can be modulated by external stimuli. However the optical response is highly sensitive to the polymer shell morphology, thickness and dielectric contrast. In this paper we study the nature of cross-linked, thermoresponsive polymer shells for the first time using four different scattering approaches to elucidate the density profile of the shells. Each scattering method provides unique information about the temperature-induced changes of shell thickness in terms of hydrodynamic radius and radius of gyration, the pair-distance distribution functions of the shells as well as the dynamic network fluctuations. Only a combination of these different scattering techniques allows to develop a morphological model of the core-shell particles. We further demonstrate control of the cross-linker distribution in core-shell synthesis by semi-batch precipitation copolymerization. Conducting the polymerization in three steps, we show for the first time that the polymer shell thickness can be successively increased without affecting the shell morphology and response behavior. [ABSTRACT FROM AUTHOR]

The interaction of spherical gold nanoparticles (Au-NPs) with microgels composed of chemically cross-linked poly-(N-isopropylacrylamide) is reported. Simple mixing of the two components leads to adsorption of the gold particles onto the microgels. Different loading densities can be achieved by varying the ratio of gold particles to microgel particles. The adsorption of gold nanoparticles is analysed by TEM, UV-Vis absorption spectroscopy and SAXS. The influence of the microgel mesh size on the adsorption of gold nanoparticles is investigated by using microgels with three different cross-linker densities. The results suggest a strong relationship between the nanoparticle penetration depth and the cross-linker density. This, in turn, directly influences the optical properties of the colloids due to plasmon resonance coupling. In addition, information about the mesh size distribution of the microgels is obtained. For the first time the change in optical properties by varying cross-linker density and temperature is directly related to the formation of dimers of gold particles, proven by SAXS. [ABSTRACT FROM AUTHOR]

Adjusting the inter-particle distances in ordered nanoparticle arrays can create new nano-devices and is of increasing importance to a number of applications such as nanoelectronics and optical devices. The assembly of negatively charged polystyrene (PS) nanoparticles (NPs) on Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes, quaternized PDMAEMA brushes and Si/PEI/(PSS/PAH)2, was studied using dip- and spin-coating techniques. By dip-coating, two dimensional (2-D), randomly distributed non-close packed particle arrays were assembled on Si/PEI/(PSS/PAH)2 and PDMAEMA brushes. The inter-particle repulsion leads to lateral mobility of the particles on these surfaces. The 200 nm diameter PS NPs tended to an inter-particle distance of 350 to 400 nm (center to center). On quaternized PDMAEMA brushes, the strong attractive interaction between the NPs and the brush dominated, leading to clustering of the particles on the brush surface. Particle deposition using spin-coating at low spin rates resulted in hexagonal close-packed multilayer structures on Si/PEI/(PSS/PAH)2. Close-packed assemblies with more pronounced defects are also observed on PDMAEMA brushes and QPDMAEMA brushes. In contrast, randomly distributed monolayer NP arrays were achieved at higher spin rates on all polyelectrolyte architectures. The area fraction of the particles decreased with increasing spin rate. [ABSTRACT FROM AUTHOR]