Hybrid Colloids Research Articles

Laser synthesis of colloidal Si@Au and Si@Ag nanoparticles in water via plasma-assisted reduction

We report the facile synthesis of colloidal Si@Au and Si@Ag nanoparticles (NPs) through nanosecond IR laser plasma-mediated reduction of 0.03 mM aqueous solutions of chloroauric acid (HAuCl4) and silver nitrate (AgNO3) at different laser intensities on the surface of Si NPs during the ablation of the silicon wafer. The resulting hybrid colloidal NPs were analysed by UV–vis transmission spectroscopy, dynamic light scattering, scanning electron microscopy, energy-dispersive x-ray and x-ray photoelectron spectroscopy.

Protein extraction and cytotoxicity abilities of colloidal gold-coated silica hybrid nanoparticles

Monodisperse non-hybrid silica and hybrid colloidal silica of ≤ 200 nm decorated with small Au nanoparticles (NPs) were synthesized in a simple single-step method. Non-hybrid silica NPs were synthesized in the absence and presence of different twin tail cationic surfactants, while tiny Au NPs were grown under in situ reaction conditions on non-hybrid silica synthesized previously by using cationic dextran. Bio-applicability and cytotoxicity of both hybrid as well as non-hybrid silica NPs were tested by using them for the extraction of protein fractions from complex aqueous protein solutions and treating them with blood cells, respectively. Both non-hybrid and hybrid silica NPs demonstrate excellent ability to extract proteins fractions predominantly of relatively low molecular masses, i.e., ~ 80 kDa. Extraction preferences between both kinds of silica became prominent when predominantly hydrophobic proteins such zein and rice proteins were used rather than mainly polar protein like BSA. Applicability for more complex biological fluid like serum indicated the competitive extractions among strongly versus weakly bound proteins. With significant bearing in in vivo conditions, hybrid silica was potentially toxic towards the blood cells in comparison to non-hybrid silica. It stems from the collective interactions of silica as well as nanometallic surfaces of Au NPs to interact with the blood cells causing hemolysis and hence may not be the suitable vehicles for drug release in systemic circulation.

Tunable Colloidal Crystalline Patterns on Flat and Periodically Micropatterned Surfaces as Antireflective Layers and Printable–Erasable Substrates

Abstract2D nonclose‐packed colloidal crystal patterns have received considerable attention in various fields, but it remains a challenge to fabricate patterns and manipulate their geometries regardless of substrate types and structures. Herein, a simple approach is developed for producing nonclose‐packed hydrogel colloidal crystalline patterns on flat and periodically micropatterned substrates by exposing close‐packed colloidal crystal monolayers to salt aqueous solutions. The patterns are achievable on flat surfaces like silicon, glass, graphene, poly(ethylene terephthalate), and poly(dimethyl siloxane) surfaces. Hydrogel colloidal spheres can deform into disk‐like or hemispherical particles on different material substrates. The colloid geometries and dimensions in the patterns are tunable by varying the salt type or concentration. The tunable colloidal crystalline patterns can form on periodically micropatterned substrates, resulting in novel hierarchical crystalline structures. The modification of the method is effective to easily fabricate nonclose‐packed hybrid colloidal crystal patterns where plasmonic nanoparticles are selectively assembled on the hydrogel particle surfaces. These patterned substrates modulate colors, reduce reflectivity of visible to near‐infrared light, and enhance transmittance. The nonclose‐packed colloidal patterns are useful as antireflection coating layers to enhance the solar thermoelectricity efficiencies of flat and micropatterned substrates. The optical tunability of colloidal crystal patterns enables developing colloid crystal‐based printable and erasable substrates.

Synthesis of raspberry-like polymer/SiO2 hybrid colloidal spheres grafted by block-copolymer poly(MPC-b-MPS) for underwater superoleophobic anti-biofouling coatings

Raspberry-like polymer/inorganic compound hybrid colloidal spheres have attracted tremendous interest owing to their many potential applications, but most of them are concentrated on synthesis methods, controlling structures and morphologies. Herein, we synthesize raspberry-like poly(ethyl methacrylate)/SiO2 colloidal spheres and further graft a hydrophilic diblock copolymer on the SiO2 nanoparticles. The obtained copolymer-grafted hybrid sphere-based coatings are robust and display excellent underwater superoleophobic and anti-biofouling performances as well as self-repairing ability.

Hybrid nanosystems based on colloidal quantum dots and organic ligands (Review)

The review discusses modern approaches to the synthesis of semiconductor colloidal quantum dots and hybrid nanosystems represented by conjugates of quantum dots and organic ligands. The mechanisms of photoinduced processes taking place in systems of this kind are considered in detail. Data on chemoand photoconvertible hybrid nanosystems are summarized.

Tunable clustering of magnetic nanoparticles in microgels: enhanced magnetic relaxivity by modulation of network architecture.

In the present work we used microgels as colloidal containers for the loading of hydrophobic magnetic nanoparticles using the solvent exchange method. We varied systematically two parameters: (i) the crosslinking degree of microgels (1-4.5 mol% crosslinker) and (ii) loading of hydrophobic magnetite nanoparticles (d = 7 nm) in microgels (2-10 wt%). The experimental data show that the interplay between these two parameters provides efficient control over the clustering of magnetic nanoparticles in the microgel structure. Transverse magnetization relaxation measurements indicate that the formation of nanoparticle clusters in microgels induces non-linear enhancement of the relaxivity with the increase of nanoparticle loading in microgels. The results suggest that the modulation of the microgel network architecture can be efficiently applied to trigger self-assembly processes inside microgels and design hybrid colloids with unusual morphologies and properties.

Flash nanoprecipitation of polymer supported Pt colloids with tunable catalytic chromium reduction property

Pt nanoparticle (NP) embedded polystyrene-b-poly(4-vinylpyridine) colloids (Pt@PS-b-PVP) are prepared through flash nanoprecipitation (FNP). Uniform Pt@PS-b-PVP nanocomposites with ~5 nm Pt NPs decorating the surface on PS-b-PVP nanospheres are easily prepared with tunable size and Pt arrangement. The catalytic chromium reduction property of Pt@PS-b-PVP is tested. The hybrid colloids exhibited excellent catalytic performance as well as tunable ability dependent on the fined-controlled nanostructure. Moreover, the reported nanocomposites are reused for four times without loss of catalytic activity.

Raymond Schaak

Angewandte Chemie International EditionVolume 57, Issue 12 p. 3002-3002 Author ProfileFree Access Raymond Schaak First published: 24 November 2017 https://doi.org/10.1002/anie.201711024Citations: 2AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “The downside of my job is having to sometimes be the bearer of bad news. My favorite food is anything I can cook on a grill, especially salmon ...” This and more about Raymond Schaak can be found on page 3002. Raymond Schaak The author presented on this page has published more than 10 articles in Angewandte Chemie in the last 10 years, most recently: “Size and Interface Modulated Metal–Insulator Transition in Solution-Synthesized Nanoscale VO2–TiO2–VO2 Heterostructures”: Angew. Chem. Int. Ed. 2017, 56, 15348; Angew. Chem. 2017, 129, 15550. The work of R. E. Schaak has been featured on the cover of Angewandte Chemie: “Sequential Anion and Cation Exchange Reactions for Complete Material Transformations of Nanoparticles with Morphological Retention”: J. M. Hodges, K. Kletetschka, J. L. Fenton, C. G. Read, R. E. Schaak, Angew. Chem. Int. Ed. 2015, 54, 8669; Angew. Chem. 2015, 127, 8793. Date of birth: October 12, 1975 Position: DuPont Professor of Materials Chemistry, Penn State University E-mail: res20@psu.edu Homepage: http://chem.psu.edu/directory/res20 ORCID: 0000-0002-7468-8181 Education: 1998 BS, Lebanon Valley College, Pennsylvania 2001 PhD supervised by Thomas Mallouk, Penn State University 2001–2003 Postdoc with Robert Cava, Princeton University Awards: 2006 Beckman Young Investigator Award; 2006 DuPont Young Professor; 2007 Sloan Research Fellow; 2007 Camille Dreyfus Teacher–Scholar Award; 2011 National Fresenius Award; 2016 Inorganic Nanoscience Award, ACS Current research interests: Synthetic inorganic nanochemistry; retrosynthetic design of solid-state materials; nanoparticle synthesis; chemical reactions of nanoparticles; nanoparticle formation pathways; new materials discovery; earth-abundant catalytic materials for energy applications Hobbies: Photography, painting, music, road trips The downside of my job is having to sometimes be the bearer of bad news. My favorite food is anything I can cook on a grill, especially salmon. My favorite quote is “fortune favors the prepared mind” (Pasteur). The biggest problem that scientists face is communicating the excitement, importance, and implications of fundamental research to many different audiences. What I look for first in a publication is the key result(s)—what is new in it that advances the field. The most important thing I learned from my parents is the value of balance and priorities in life: work hard, but also make time for family, friends, hobbies, and rest. My favorite place on earth is a place (not to be named!) where I can escape without access to internet or a phone for a few days. I chose chemistry as a career because I liked doing experiments, using math to solve problems, and piecing together different concepts in creative ways. In high school, chemistry “clicked” as a career where I could integrate these interests. My not-so-secret passion is macro photography. I like taking pictures of the small things in the world around us that we wouldn't normally see. If I were not a scientist, I would be a graphic designer, a photographer, or an architect. I lose track of time when I am doing something creative, like photography, art, or brainstorming. My 5 top papers: 1“Metallurgy in a Beaker: Nanoparticle Toolkit for the Rapid Low-Temperature Solution Synthesis of Functional Multimetallic Solid State Materials”: R. E. Schaak et al., J. Am. Chem. Soc. 2005, 127, 3506. (Defined our approach to using nanoparticles as reagents for low-temperature solid-state reactions.) 2“Orthogonal Reactivity of Metal and Multimetal Nanostructures for Selective, Stepwise, and Spatially-Controlled Solid State Modification”: B. M. Leonard, M. E. Anderson, K. D. Oyler, T. H. Phan, R. E. Schaak, ACS Nano 2009, 3, 940. (Our vision for applying molecule-inspired orthogonal reactivity to nanoparticles.) 3“A total-synthesis framework for the construction of high-order colloidal hybrid nanoparticles”: M. R. Buck, J. F. Bondi, R. E. Schaak, Nature Chem. 2012, 4, 37. (Applies concepts from natural-product synthesis to complex multicomponent nanoparticles.) 4“Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen Evolution Reaction”: E. J. Popczun, J. R. McKone, C. G. Read, A. J. Biacchi, A. M. Wiltrout, N. S. Lewis, R. E. Schaak, J. Am. Chem. Soc. 2013, 135, 9267. (Transition-metal phosphides were introduced as a viable family of earth-abundant HER catalysts.) 5“Structure-Selective Cation Exchange in the Synthesis of Zincblende MnS and CoS Nanocrystals”: J. L. Fenton, R. E. Schaak, Angew. Chem. Int. Ed. 2017, 56, 6464; Angew. Chem. 2017, 129, 6564. (Multiple distinct crystal structures can be retained during nanocrystal cation exchange.) Citing Literature Volume57, Issue12March 12, 2018Pages 3002-3002 ReferencesRelatedInformation

Effects of Gold Colloids on the Photosensitization Efficiency of Silica Particles Doped with Protoporphyrin IX

AbstractPhotodynamic treatments represent a non‐invasive tool to intervene in the cell cycle, only when needed, but high excitation power is an important limitation. In this work, protoporphyrin IX (PpIX) is covalently anchored to the surface of silica particles. The hybrid colloids are prepared with different photosensitizer loadings and characterized by TEM, SEM‐EDX and spectroscopic methods. The visible excitation of the colloidal samples generates reactive oxygen species, which are quantified by use of a specific chemical scavenger agent (1,3‐diphenylisobenzofuran). The determined efficiencies depend on the PpIX loading, being higher in the sample where the aggregation is reduced. To enhance further the photosensitizing performance of silica‐PpIX samples, increasing amounts of gold nanoparticles are conjugated to the silica surface in order to exploit the antenna effect of plasmonic nanostructures. The visible excitation of silica‐PpIX systems in the presence of gold nanoparticles results in a faster and more efficient photoinduced formation of ROS species reaching a 230 % enhancement of ROS photosensitization when 1013 Au nanoparticles mL−1 (corresponding to circa 75 ppm of gold) are present. The efficiency data are discussed in terms of plasmonic enhancement of the excitation field.

A thermo-degradable hydrogel for on-demand drug delivery

This study involves the synthesis of a new silica-based colloidal hybrid system. In this new hybrid system, poly (ethylene glycol) (PEG) and thermo-sensitive amphiphilic biocompatible poly (vinyl pyrrolidone) (PVP) were used to create suitable storage for hydrophobic drugs. The possibility of using variable PVP/PEG molar ratios to modulate drug release rate from silica nanoparticles was a primary goal of the current research. In addition, an investigation of the drug release kinetic was conducted. To achieve this, silica nanoparticles were synthesized in poly (ethylene glycol) (PEG) and poly (vinyl pyrrolidone) (PVP) solution incorporated with enrofloxacin (EFX) (as a model hydrophobic drug), using a simple synthetic strategy of hybrid materials which avoided waste and multi-step processes. The impacts of PVP/PEG molar ratios, temperature, and pH of the release medium on release kinetic were investigated. The physicochemical properties of the drug-loaded composites were studied by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). In vitro drug release studies demonstrated that the drug release rate, which was evaluated by analyzing the experimental data with seven kinetic models in a primarily non-Fickian diffusion-controlled process, aligned well with both Ritger-Peppas and Sahlin-Peppas equations.

Disinfection of various bacterial pathogens using novel silver nanoparticle-decorated magnetic hybrid colloids

Silver nanoparticles (AgNPs) have long been considered a powerful disinfectant for controlling pathogenic microorganisms. However, AgNPs might have adverse effects on both human health and our ecosystems due to their potential cytotoxicity and the difficulty in recovering them after their release into the environment. In this study, we characterized the antimicrobial efficacy caused by a novel micrometer-sized magnetic hybrid colloid (MHC) containing 7, 15, or 30nm sized monodispersed AgNPs (AgNP-MHCs), which can be re-collected from the environment using simple procedures, such as a magnet or centrifugation. We evaluated the antibacterial capabilities of AgNP-MHCs against target bacteria (Legionella pneumophila, Bacillus subtilis, Escherichia coli, and Clostridium perfringens) and compared them with the inactivation efficacy of AgNPs ~30nm in diameter (nAg30s). Among the different AgNP-MHCs composites evaluated, Ag30-MHCs had the greatest antibacterial effect. After 1h of exposure, more than a 4-log10 reduction of L. pneumophila and 6-log10 reduction of B. subtilis was achieved by 4.6×109particles/mL of Ag30-MHCs and Ag30-MHC-Ls. In addition, Ag30-MHC-Ls maintained their strong antibacterial capabilities under anaerobic conditions. Our results indicate that AgNP-MHCs can be considered excellent tools for controlling waterborne bacterial pathogens, with a minimal risk of release into the environment.

Amyloid Fibrils form Hybrid Colloidal Gels and Aerogels with Dispersed CaCO3 Nanoparticles

AbstractNew hybrid colloidal gels are reported formed by amyloid fibrils and CaCO3 nanoparticles (CaNPs), with Ca2+ as charge screening ions and CaNPs as physical crosslinking agents to establish and stabilize the network. The gel is characterized by rheological measurements and diffusing wave spectroscopy, complemented by microscopic observations using transmission and scanning electron microscopy. The hybrid colloidal gels show a two orders of magnitude improved gel strength at significantly shorter gelation times compared to previous calcium ion‐induced amyloid fibril gels. Supercritical CO2‐dried colloidal aerogels allow demonstrating that amyloid fibrils, combined with smaller (higher specific surface area) CaNPs, constitute a denser fibrils network, resulting in stronger gels. By varying the amyloid fibril concentration and the CaNPs size and concentration, the complete phase diagram is mapped out. This enables identifying the sol–gel phase transition and a window for gel formation, which widens with increasing CaNPs size. Finally pH responsiveness and self‐healing properties of this hybrid colloidal gel are also demonstrated, making these systems a suitable candidate for biological applications.

Hybrid Colloidal Stabilization Mechanism toward Improved Photoluminescence and Stability of CdSe/CdS Core/Shell Quantum Dots.

Colloidal quantum dots can be stabilized in either a polar solvent or a nonpolar solvent depending on their surface chemistry. The former is typically achieved by charge stabilization while the latter by steric hindrance. This allows reversible tuning of their surface polarity for targeted application by engineering their ligand profile. Here we developed a hybrid stabilization approach that leveraged a combination of steric hindrance and charge stabilization simultaneously. We demonstrated this mechanism in a phase transfer process where hexane dispersed and hydrophobic CdSe/CdS core/shell quantum dots were exchanged into the hydrophilic dimethylformamide (DMF) phase. This was achieved by employing both Z-type cadmium acetate and X-type halide ligands. The results suggested only by using this hybrid stabilization strategy were we able to achieve good colloidal stability while preserving their photoluminescence quantum yield. This hybrid ligand strategy may promise new opportunities for the application of QDs in optoelectronic areas.

Kinetic and theoretical studies of novel biodegradable thermo-sensitive xerogels based on PEG/PVP/silica for sustained release of enrofloxacin

This study involves the synthesis of a new silica-based colloidal hybrid system. In this new hybrid system, poly (ethylene glycol) (PEG) and thermo-sensitive amphiphilic biocompatible poly (vinyl pyrrolidone) (PVP) were used to create suitable storage for hydrophobic drugs. The possibility of using variable PVP/PEG molar ratios to modulate drug release rate from silica nanoparticles was a primary goal of the current research. In addition, an investigation of the drug release kinetic was conducted. To achieve this, silica nanoparticles were synthesized in poly (ethylene glycol) (PEG) and poly (vinyl pyrrolidone) (PVP) solution incorporated with enrofloxacin (EFX) (as a model hydrophobic drug), using a simple synthetic strategy of hybrid materials which avoided waste and multi-step processes. The impacts of PVP/PEG molar ratios, temperature, and pH of the release medium on release kinetic were investigated. The physicochemical properties of the drug-loaded composites were studied by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). In vitro drug release studies demonstrated that the drug release rate, which was evaluated by analyzing the experimental data with seven kinetic models in a primarily non-Fickian diffusion-controlled process, aligned well with both Ritger-Peppas and Sahlin-Peppas equations.

Hybrid Colloids Produced by Sequential Capillarity-assisted Particle Assembly: A New Path for Complex Microparticles.

Colloidal particles have long been under the spotlight of a very diverse research community, given their ubiquitous presence in a broad class of materials and processes, and their pivotal role as model systems. More recently, intense efforts have been devoted to the development of micro- and nanoparticles combining multiple materials in objects with a controlled architecture, hence introducing multiple functionalities and a prescribed symmetry for interactions. These particles are often called hybrid colloids or colloidal molecules, given the analogy with classical molecules presenting well defined structures and chemical compositions. Here, we review the recent progress made in our group to fabricate a broad library of hybrid colloids exploiting a novel assembly route, which uses capillary forces at the moving edge of an evaporating droplet for the sequential composition of colloidal clusters, whose geometry and chemistry can be independently programmed.

Interaction of cellulose nanocrystals with titanium dioxide and peculiarities of hybrid structures formation

In this work we prepared hybrid particles based on cellulose nanocrystals and titanium dioxide nanoparticles and studied their aggregate stability for a wide range of the components ratios. Electrosurface properties of cellulose nanocrystals and TiO2 greatly influence on morphology and properties of the hybrid particles. Sufficient amount of TiO2 nanoparticles in the hybrid dispersions make it possible to completely cover cellulose nanocrystals surface and form a core-shell structure. Derjaguin–Landau–Verwey–Overbeek theory calculations confirmed experimental data and possibility of TiO2 monolayer covering of cellulose nanocrystals surface. Summarizing the findings, we conclude about the mechanism of interaction between cellulose nanocrystals and titanium dioxide—at the first stage particles are attracted to one another due to long-range electrostatic forces; at the second stage hydrogen bonds are formed. It is found that control of the surface potential allows to obtain stable colloidal hybrid dispersions (having negative-charged or positive-charged particles), or hybrid systems with a neutral surface charge.

Controlling Configurational Isomerism in Three-Component Colloidal Hybrid Nanoparticles.

Colloidal hybrid nanoparticles are solution-dispersible constructs that join together multiple distinct nanoscale materials through direct solid-solid interfaces. Given their multifunctionality and synergistic properties that emerge from interfacial coupling, hybrid nanoparticles are of interest for applications in biomedical imaging, solar energy conversion, heterogeneous catalysis, nanophotonics, and beyond. High-order hybrid nanoparticles, which incorporate three or more nanocrystal domains, offer greater tunability and functional diversity relative to one or two-component nanoparticles. The multiple heterojunctions within these structures can facilitate complex electromagnetic coupling as well as cooperative surface processes. Additionally, these materials can be used as model systems for studying fundamental structure-property relationships at the nanoscale that arise from particle coupling and interfacial exchanges. Limiting these advances is the inability to synthesize hybrid nanoparticles with precise morphologies and geometries. High-order hybrid nanoparticles can adopt more than one configuration, and each unique arrangement will have different heterointerfaces and, accordingly, different functions. Seeded-growth methods are among the most effective methods for producing high-quality hybrid nanoparticles. Engineering complex heterostructures using these stepwise reactions is in some ways conceptually analogous to the total synthesis of large organic molecules. However, unlike in molecular synthesis, the rules and guidelines that underpin the formation of hybrid nanoparticles are less understood. For example, when a third domain is added to a two-component heterodimer nanoparticle seed, several distinct types of hybrid nanoparticle products are possible, but only one is typically observed due to preferred growth at specific locations. The three-component heterotrimer products that preferentially form are not necessarily those that have the domain configurations and heterojunctions required to facilitate a targeted application. Different arrangements of the three nanoparticles that comprise a heterotrimer lead to distinct configurational isomers. Accordingly, understanding and controlling configurational isomerism in nanoparticle heterotrimers is foundational for engineering high-order hybrid nanostructures with targeted heterointerfaces, properties, and functionalities. This Account highlights recent insights into the pathways by which three-component nanoparticle heterotrimers form and how their configurations can be controlled and modified. In-depth microscopic investigations into the formation of heterotrimers by growing a third nanoparticle domain on a two-component heterodimer seed have revealed that in some cases indiscriminate nucleation first occurs on all exposed surfaces followed by surface-mediated migration and coalescence to the preferred interface. This insight helps to rationalize observed site-specific, chemoselective growth phenomena. Additionally, new approaches for directing growth in heterotrimer synthesis, such as protection-deprotection schemes inspired by organic chemistry, are becoming effective tools for constructing hybrid nanoparticles having nonpreferred domain configurations. Alternatives to traditional seeded-growth approaches are also emerging, including insertion reactions driven by saturation-precipitation processes and orthogonal transformations of preformed hybrid constructs using ion exchange. These and other recent advances are providing a powerful suite of synthetic tools that are anticipated to enable function-driven design of high-order hybrid nanoparticles having targeted properties and applications.

Structural control of the hybrid colloids by cooperative assembly of PS-b-PAA and semiconductor nanoparticles from the solvent aspects

Well-defined polymer/inorganic nanoparticle (NP) hybrids are of vital importance to the development of nanomaterials with desired optical, electric, magnetic, and many other properties. We demonstrate the efficient incorporation of n-trioctylphosphine oxide (TOPO)-coated CdSe quantum dots (QDs) into polystyrene-b-polyacrylic acid (PS-b-PAA) colloids by a “solution phase self-assembly” approach. Driven by the hydrophobic interactions, the CdSe QDs are homogeneously encapsulated in the hybrid colloids. The sizes of the hybrid colloids with different structures, i.e., simple spherical micelles and big compound micelles, are tuned from 45 to 126 nm by varying the THF content in the cosolvents of THF and DMF, as well as changing the content or addition rate of selective solvent (water). The PS-b-PAA@CdSe QD hybrid colloids, which show brightly green fluorescence, can be endocytosed into biological cells and be released from the cells evolutionally, indicating their potential applications in biological imaging, labeling, and sensing, among others.

Preparation of free-standing hybrid colloidal membranes via assembly of liponanocapsules

We intended to create a free-standing and organic–inorganic hybrid colloidal membrane. The colloidal membrane was assembled from polymeric capsules, which were prepared by coating of polymer layers over a liposome (liponanocapsules). In this study, two approaches were employed for mineralization over the membrane with calcium phosphate (CaP) to control its mechanical robustness and biodegradability (hybrid bioscaffold). One approach was based on CaP deposition over the liponanocapsules and their assembly into the hybrid membrane. CaP deposition was conducted via the counter-diffusion of phosphate ions and calcium ions across the capsule wall to obtain hybrid nanocapsules. Then, free-standing hybrid membrane was obtained by utilizing hybrid nanocapsules as building blocks for drying-mediated assembly. The obtained hybrid membrane was degraded into individual nanocapsules and degradation could be tuned by the crystal structure of CaP. In another approach, the free-standing membrane was assembled from DNA-coated liponanocapsules and then the counter-diffusion of ions was carried out across each assembled nanocapsule for CaP mineralization. The mechanical robustness of the membrane was significantly improved and its degradation was suppressed by CaP mineralization. This is probably because mineral cross-linkages were formed in the interspace between each nanocapsule. Fluorescent substances could be incorporated in each nanocapsule of the membrane and their release could be tuned by the control in crystal properties of CaP.

Hybrid colloidal microswimmers through sequential capillary assembly.

Active colloids, also known as artificial microswimmers, are self-propelled micro- and nanoparticles that convert uniform sources of fuel (e.g. chemical) or uniform external driving fields (e.g. magnetic or electric) into directed motion by virtue of asymmetry in their shape or composition. These materials are currently attracting enormous scientific attention as models for out-of-equilibrium systems and with the promise to be used as micro- and nanoscale devices. However, current fabrication of active colloids is limited in the choice of available materials, geometries, and modes of motion. Here, we use sequential capillarity-assisted particle assembly (sCAPA) to link microspheres of different materials into hybrid clusters of prescribed shapes ("colloidal molecules") that can actively translate, circulate and rotate powered by asymmetric electro-hydrodynamic flows. We characterize the active motion of the clusters and highlight the range of parameters (composition and shape) that can be used to tune their trajectories. Further engineering provides active colloids that switch motion under external triggers or perform simple pick-up and transport tasks. By linking their design, realization and characterization, our findings enable and inspire both physicists and engineers to create customized active colloids to explore novel fundamental phenomena in active matter and to investigate materials and propulsion schemes that are compatible with future applications.