Unraveling the Water Impermeability Discrepancy in CVD‐Grown Graphene

Graphene has recently attracted particular interest as a flexible barrier film preventing permeation of gases and moistures. However, it has been proved to be exceptionally challenging to develop large‐scale graphene films with little oxygen and moisture permeation suitable for industrial uses, mainly due to the presence of nanometer‐sized defects of obscure origins. Here, the origins of water permeable routes on graphene‐coated Cu foils are investigated by observing the micrometer‐sized rusts in the underlying Cu substrates, and a site‐selective passivation method of the nanometer‐sized routes is devised. It is revealed that nanometer‐sized holes or cracks are primarily concentrated on graphene wrinkles rather than on other structural imperfections, resulting in severe degradation of its water impermeability. They are found to be predominantly induced by the delamination of graphene bound to Cu as a release of thermal stress during the cooling stage after graphene growth, especially at the intersection of the Cu step edges and wrinkles owing to their higher adhesion energy. Furthermore, the investigated routes are site‐selectively passivated by an electron‐beam‐induced amorphous carbon layer, thus a substantial improvement in water impermeability is achieved. This approach is likely to be extended for offering novel barrier properties in flexible films based on graphene and on other atomic crystals.     

Micrometer‐ and Nanometer‐Sized Organic Single‐Crystalline Transistors

The use of micrometer and nanometer‐sized organic single crystals to fabricate devices can retain all the advantages of single crystals, avoid the difficulties of growing large crystals, and provide a way to characterize organic semiconductors more efficiently. Moreover, the effective use of such “small” crystals will be beneficial to nanoelectronics. Here we review the recent progress of organic single‐crystalline transistors based on micro‐/nanometer‐sized structures, namely fabrication methods and related technical issues, device properties, and current challenges.     

Dual Light and Temperature Responsive Micrometer‐Sized Structural Color Actuators

Externally induced color‐ and shape‐changes in micrometer‐sized objects are of great interest in novel application fields such as optofluidics and microrobotics. In this work, light and temperature responsive micrometer‐sized structural color actuators based on cholesteric liquid‐crystalline (CLC) polymer particles are presented. The particles are synthesized by suspension polymerization using a reactive CLC monomer mixture having a light responsive azobenzene dye. The particles exhibit anisotropic spot‐like and arc‐like reflective colored domains ranging from red to blue. Electron microscopy reveals a multidirectional asymmetric arrangement of the cholesteric layers in the particles and numerical simulations elucidate the anisotropic optical properties. Upon light exposure, the particles show reversible asymmetric shape deformations combined with structural color changes. When the temperature is increased above the liquid crystal‐isotropic phase transition temperature of the particles, the deformation is followed by a reduction or disappearance of the reflection. Such dual light and temperature responsive structural color actuators are interesting for a variety of micrometer‐sized devices.     

Size‐Dependent Cytotoxicity of Monodisperse Silica Nanoparticles in Human Endothelial Cells

The effect that monodisperse amorphous spherical silica particles of different sizes have on the viability of endothelial cells (EAHY926 cell line) is investigated. The results indicate that exposure to silica nanoparticles causes cytotoxic damage (as indicated by lactate dehydrogenase (LDH) release) and a decrease in cell survival (as determined by the tetrazolium reduction, MTT, assay) in the EAHY926 cell line in a dose‐related manner. Concentrations leading to a 50% reduction in cell viability (TC₅₀) for the smallest particles tested (14‐, 15‐, and 16‐nm diameter) ranging from 33 to 47 µg cm^?2 of cell culture differ significantly from values assessed for the bigger nanoparticles: 89 and 254 µg cm^?2 (diameter of 19 and 60 nm, respectively). Two fine silica particles with diameters of 104 and 335 nm show very low cytotoxic response compared to nanometer‐sized particles with TC₅₀ values of 1095 and 1087 µg cm^?2, respectively. The smaller particles also appear to affect the exposed cells faster with cell death (by necrosis) being observed within just a few hours. The surface area of the tested particles is an important parameter in determining the toxicity of monodisperse amorphous silica nanoparticles.     

Multifunctional Assembly of Micrometer‐Sized Colloids for Cell Sorting

Compared to the extensively studied nanometer‐sized colloids, less attention has been paid to the assembly of micrometer‐sized colloids with multifunctional characteristics. To address this need, a bottom‐up approach is developed for constructing self‐assemblies of micrometer‐sized magnetic colloids possessing multifunctionality, including magnetic, optical, and biological activities. Biotinylated oligo (p‐phenylene vinylene) (OPV) derivatives are designed to mediate the self‐assembly of streptavidin‐modified magnetic beads. The optical element OPV derivatives provide a fluorescence imaging ability for tracing the assembly process. Target cells can be recognized and assembled by the colloidal assembly with bioactive element antibodies. The colloidal assembly reveals better cell isolation performance by its amplified magnetic response in comparison to monodisperse colloids. The self‐assembly of micrometer‐sized magnetic colloids through a combination of different functional ingredients to realize multifunction is conceptually simple and easy to achieve.     

Temperature‐Sensitive Hydrogel‐Particle Films from Evaporating Drops

A simple method to prepare temperature‐sensitive films composed of micrometer‐sized colloidal hydrogel particles using evaporating drops of colloidal suspensions is demonstrated. The films range in thickness from a monolayer to approximately fifty particle diameters depending on initial particle volume fraction. Sessile droplets of hydrogel‐particle suspensions are evaporated on silicon wafers. The film is formed from particles spread densely over the air–water interface which then cross‐link and are deposited on the surface during the evaporation process. The resultant thin films exhibit a temperature‐responsiveness characteristic of the individual particles permitting modulation of size, shape, porosity, and optical transmission.     

Micrometer‐sized DNA–Single‐Fluorophore–DNA Supramolecule: Synthesis and Single‐Molecule Characterization

The synthesis of single‐fluorophore‐bis(micrometer‐sized DNA) triblock supramolecules and the optical and structural characterization of the construct at the single‐molecule level is reported. A fluorophore‐bis(oligodeoxynucleotide) triblock is synthesized via the amide‐coupling reaction. Subsequent protocols of DNA hybridization/ligation are developed to form the supramolecular triblock structure with λ‐DNA fragments on the micrometer length scale. The successful synthesis of the micrometer‐sized DNA–single‐fluorophore–DNA supramolecule is confirmed by agarose gel electrophoresis with fluorescence imaging under UV excitation. Single triblock structures are directly imaged by combined scanning force microscopy and single‐molecule fluorescence microscopy, and provide unambiguous confirmation of the existence of the single fluorophore inserted in the middle of the long DNA. This type of triblock structure is a step closer to providing a scaffold for single‐molecule electronic devices after metallization of the DNAs.     

Structural Evolution and Copper‐Ion Release Behavior of Cu‐pHEMA Hybrids Synthesized In Situ

A novel Cu‐pHEMA hybrid was successfully prepared by in situ photopolymerization of 2‐hydroxyethyl methacrylate (HEMA) monomer in the presence of Cu(II) copper ions, following an in situ chemical reduction. Experimental observations indicate that intermolecular interactions such as the coupling force and hydrogen bonding between the Cu and the hydroxyl groups further stabilize the hybrid structure to a considerable extent. Localization of the metallic copper particles within the pHEMA network structure as a result of those intermolecular interactions gives rise to the formation of discretely distributed nanocrystallites with particle sizes ranging from 5 to 25 nm in diameter. A crystallographic change of the Cu nanophase from an amorphous‐like to a crystalline structure is observed as the H₂O:HEMA molar ratio increases, upon synthesis, accompanied with an increase in the particle size. A relatively slow and sustained release of the Cu (in the form of cupric ions) from the hybrids was measured for a time period of about 10 days, which also illustrates a Cu(II)‐induced proliferation of the endothelial cells over a relatively small range of release rate of the Cu from the hybrids. Such a new type of Cu‐loaded hybrid hydrogel is expected to be compatible and may be considered as a candidate biomaterial for biomedical/therapeutic uses.     

Effect of Carbon Coating on the Physico‐chemical Properties and Toxicity of Copper and Nickel Nanoparticles

The primary aim of these interdisciplinary studies is to investigate the effect of surface carbon coating on the physico‐chemical properties and toxicity of carbon‐coated and noncoated copper and nickel nanoparticles (C‐Cu, Cu, C‐Ni, Ni NPs) in A549 alveolar epithelial cells. Compared to Cu NPs, C‐Cu NPs exhibit protection against surface oxidation, tenfold higher cellular uptake, and fourfold lower release of soluble Cu. The toxicity of C‐Cu NPs and Cu NPs is associated with pronounced damage to mitochondrial function and plasma membrane integrity, respectively. Compared to Cu and C‐Cu NPs, Ni and C‐Ni NPs are less toxic. These studies demonstrate that correlations can be drawn between physico‐chemical properties and resultant toxicity of NPs as a function of surface carbon coating.     

Templated Solid‐State Dewetting of Thin Silicon Films

Thin film dewetting can be efficiently exploited for the implementation of functionalized surfaces over very large scales. Although the formation of sub‐micrometer sized crystals via solid‐state dewetting represents a viable method for the fabrication of quantum dots and optical meta‐surfaces, there are several limitations related to the intrinsic features of dewetting in a crystalline medium. Disordered spatial organization, size, and shape fluctuations are relevant issues not properly addressed so far. This study reports on the deterministic nucleation and precise positioning of Si‐ and SiGe‐based nanocrystals by templated solid‐state dewetting of thin silicon films. The dewetting dynamics is guided by pattern size and shape taking full control over number, size, shape, and relative position of the particles (islands dimensions and relative distances are in the hundreds nm range and fluctuate ≈11% for the volumes and ≈5% for the positioning).     

Toward High Strength and High Electrical Conductivity in Super‐Aligned Carbon Nanotubes Reinforced Copper

The miniaturization of electronic products is drawing higher demand in the strength and conductivity of conductors. This work demonstrates the possibility of substantially increasing the dislocation density in copper to enhance the strength of super‐aligned carbon nanotubes (SACNTs) reinforced copper matrix composites (SACNT/Cu) without compromising the electrical conductivity. High strain is introduced into pure copper and SACNT/Cu by accumulative roll‐bonding (ARB) process up to 16 cycles at ambient temperature. SACNTs with initial laminated distribution turn out to be dispersed uniformly with maintained directional arrangement inside the copper matrix after ARB, which can then effectively block the motion of dislocations. Therefore, large number of dislocations propagated by large strains can be accumulated without subdivision. The accumulated dislocations will result into strain hardening, which is the major strengthening mechanism in SACNT/Cu after ARB. Furthermore, the contribution of dislocations to resistivity increase is little, thus maintaining high electrical conductivity. As a result, a high tensile strength (505 MPa) combined with a high electrical conductivity (90% IACS) is achieved in large‐sized composite sheet.

     

Intracellular Uptake and Toxicity of Ag and CuO Nanoparticles: A Comparison Between Nanoparticles and their Corresponding Metal Ions

An increased understanding of nanoparticle toxicity and its impact on human health is essential to enable a safe use of nanoparticles in our society. The aim of this study is to investigate the role of a Trojan horse type mechanism for the toxicity of Ag‐nano and CuO‐nano particles and their corresponding metal ionic species (using CuCl₂ and AgNO₃), i.e., the importance of the solid particle to mediate cellular uptake and subsequent release of toxic species inside the cell. The human lung cell lines A549 and BEAS‐2B are used and cell death/membrane integrity and DNA damage are investigated by means of trypan blue staining and the comet assay, respectively. Chemical analysis of the cellular dose of copper and silver is performed using atomic absorption spectroscopy. Furthermore, transmission electron microscopy, laser scanning confocal microscopy, and confocal Raman microscopy are employed to study cellular uptake and particle‐cell interactions. The results confirm a high uptake of CuO‐nano and Ag‐nano compared to no, or low, uptake of the soluble salts. CuO‐nano induces both cell death and DNA damage whereas CuCl₂ induces no toxicity. The opposite is observed for silver, where Ag‐nano does not cause any toxicity, whereas AgNO₃ induces a high level of cell death. In conclusion: CuO‐nano toxicity is predominantly mediated by intracellular uptake and subsequent release of copper ions, whereas no toxicity is observed for Ag‐nano due to low release of silver ions within short time periods.     

Intracellular Delivery of a Planar DNA Origami Structure by the Transferrin‐Receptor Internalization Pathway

DNA origami provides rapid access to easily functionalized, nanometer‐sized structures making it an intriguing platform for the development of defined drug delivery and sensor systems. Low cellular uptake of DNA nanostructures is a major obstacle in the development of DNA‐based delivery platforms. Herein, significant strong increase in cellular uptake in an established cancer cell line by modifying a planar DNA origami structure with the iron transport protein transferrin (Tf) is demonstrated. A variable number of Tf molecules are coupled to the origami structure using a DNA‐directed, site‐selective labeling technique to retain ligand functionality. A combination of confocal fluorescence microscopy and quantitative (qPCR) techniques shows up to 22‐fold increased cytoplasmic uptake compared to unmodified structures and with an efficiency that correlates to the number of transferrin molecules on the origami surface.     

Label‐Free Tracking of Single Organelle Transportation in Cells with Nanometer Precision Using a Plasmonic Imaging Technique

Imaging and tracking of nano‐ and micrometer‐sized organelles in cells with nanometer precision is crucial for understanding cellular behaviors at the molecular scale. Because of the fast intracellular dynamic processes, the imaging and tracking method must also be fast. In addition, to ensure that the observed dynamics is relevant to the native functions, it is critical to keep the cells under their native states. Here, a plasmonics‐based imaging technique is demonstrated for studying the dynamics of organelles in 3D with high localization precision (5 nm) and temporal (10 ms) resolution. The technique is label‐free and can track subcellular structures in the native state of the cells. Using the technique, nanometer steps of organelle (e.g., mitochondria) transportation are observed along neurite microtubules in primary neurons, and the 3D structure of neurite microtubule bundles is reconstructed at the nanometer scale from the tracks of the moving organelles.     

Nanoparticles of Mesoporous SO3H‐Functionalized Si‐MCM‐41 with Superior Proton Conductivity

Nanometer‐sized mesoporous silica particles of around 100‐nm diameter functionalized with a large amount of sulfonic acid groups are prepared using a simple and fast in situ co‐condensation procedure. A highly ordered hexagonal pore structure is established by applying a pre‐hydrolysis step in a high‐dilution synthesis approach, followed by adding the functionalization agent to the reaction mixture. The high‐dilution approach is advantageous for the in situ functionalization since no secondary reagents for an effective particle and framework formation are needed. Structural data are determined via electron microscopy, nitrogen adsorption, and X‐ray diffraction, proton conductivity values of the functionalized samples are measured via impedance spectroscopy. The obtained mesoporous SO₃H‐MCM‐41 nanoparticles demonstrate superior proton conductivity than their equally loaded micrometer‐sized counterparts, up to 5 × 10^?2 S cm^?1. The mesoporosity of the particles turns out to be very important for effective proton transport since non‐porous silica nanoparticles exhibit worse efficient proton transport, and the obtained particle size dependence might open up a new route in rational design of highly proton conductive materials.     

The generation of nanocolloidal wear from stainless steel and titanium alloy and its toxic effects in a monocyte cell culture model

This study addresses the aspect of submicron‐sized / nanocolloidal wear comparing stainless steel (316L) and titanium alloy (TiAl6V4) for their toxic and inflammatory potentials. Wear was generated in a tribometer using the disc‐on‐pin‐method with pin and disc submerged in a sterile cell culture medium setting. The wear medium was separated according to Stokes' law into a fraction smaller 200 nm (nanocolloids) and a fraction greater 200 nm (particles). Vitality and inflammatory potential was measured in a cell culture model employing murine macrophages (J774). Cells were incubated with increasing concentrations (12.5, 25 and 50vol%) of either wear medium (particles and nanocolloids) from 316L and TiAl6V4. Vitality was measured by MTT assay and inflammatory reactions were quantified by TNF‐α ELISA. Nanocolloids from stainless steel and titanium induced strong, dose dependant toxic effects in the MTT assay while particles did not affect vitality in a dose dependant manner. The inflammatory response remained unaltered in all four groups. We conclude that interactions between soluble metallic wear and proteins forming nanocolloidal wear should be considered when conduction experiments addressing the aspect of biocompatibility in metallic implant materials.     

2D Single‐Crystalline Copper Nanoplates as a Conductive Filler for Electronic Ink Applications

Large‐scale 2D single‐crystalline copper nanoplates (Cu NPLs) are synthesized by a simple hydrothermal method. The combination of a mild reductant, stabilizer, and shape modifier allows the dimensional control of the Cu nanocrystals from 1D nanowires (NWs) to 2D nanoplates. High‐resolution transmission electron microscopy (HR‐TEM) reveals that the prepared Cu NPLs have a single‐crystalline structure. From the X‐ray photoelectron spectroscopy (XPS) analysis, it is found that iodine plays an important role in the modification of the copper nanocrystals through the formation of an adlayer on the basal plane of the nanoplates. Cu NPLs with an average edge length of 10 μm are successfully synthesized, and these Cu NPLs are the largest copper 2D crystals synthesized by a solution‐based process so far. The application of the metallic 2D crystals as a semitransparent electrode proves their feasibility as a conductive filler, exhibiting very low sheet resistance (0.4 Ω ?^?1) compared to Cu NWs and a transmittance near 75%. The efficient charge transport is due to the increased contact area between each Cu NPL, i.e., so‐called plane contact (2D electrical contact). In addition, this type of contact enhances the current‐carrying capability of the Cu NPL electrodes, implying that the large‐size Cu NPLs are promising conductive fillers for printable electrode applications.     

Controlled Attachment of Pseudomonas aeruginosa with Binary Colloidal Crystal‐Based Topographies

Micro‐ and nanotopographies can interfere with bacteria attachment, however, the interplay existing between surface chemistry and topography remains unclear. Here, self‐assembled spherical micrometer‐ silica and nanometer poly(methyl methacrylate) (PMMA)‐sized particles are used to make binary colloidal crystal (BCC) topographical patterns to study bacterial attachment. A uniform surface chemistry of allylamine plasma polymer (AAMpp) is coated on the top of the BCCs to study only the topography effects. The uncoated and coated BCCs are exposed to Pseudomonas aeruginosa, and the surfaces and bacteria are characterized using scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and fluorescence microscopy. It is found that bacteria attachment to the uncoated BCCs is delayed and individual cells are attracted to the small particle regions of the patterns. Surprisingly, this phenomenon is also observed for the AAMpp‐coated BCCs, with bacteria attaching to the small particle regions of the pattern, in stark contrast to uniform flat films of AAMpp that are highly adhesive toward P. aeruginosa. Also, the overall levels of bacterial attachment are significantly reduced by the BCC patterns compared to controls. Thus, there is a trade‐off that exists between chemistry and topography that can be exploited to delay the onset of P. aeruginosa biofilm formation on surfaces.     

Self‐Similar Growth of Polyolefin Alloy Particles in a Single Granule Multi‐Catalyst Reactor

In this news article, a new kind of in‐reactor alloying process (Chinese multi‐catalyst reactor granule technology, CMRGT) is introduced. It provides the possibility to produce series of new polyolefin materials that can be used in automotive and appliances parts by the substitution of some traditional engineering plastics. A characteristic ‘fractal (self‐similar) growth and pore‐filling mechanism’ for the CMRGT‐produced alloy particles is found. It reveals the fundamental scientific principles that govern the chemistry and physics in the formation mechanism of such novel olefinic alloys. This mechanism allows a detailed control of the dispersion and structure of these polyolefin alloys from a nanometer to micrometer size range, and possesses great potential to fulfil the requirements for a new generation of recyclable automotive materials.     

Near‐Infrared Light Responsive Multi‐Compartmental Hydrogel Particles Synthesized Through Droplets Assembly Induced by Superhydrophobic Surface

Light‐responsive hydrogel particles with multi‐compartmental structure are useful for applications in microreactors, drug delivery and tissue engineering because of their remotely‐triggerable releasing ability and combinational functionalities. The current methods of synthesizing multi‐compartmental hydrogel particles typically involve multi‐step interrupted gelation of polysaccharides or complicated microfluidic procedures with limited throughput. In this study, a two‐step sequential gelation process is developed to produce agarose/alginate double network multi‐compartmental hydrogel particles using droplets assemblies induced by superhydrophobic surface as templates. The agarose/alginate double network multi‐compartmental hydrogel particles can be formed with diverse hierarchical structures showing combinational functionalities. The synthesized hydrogel particles, when loaded with polypyrrole (PPy) nanoparticles that act as photothermal nanotransducers, are demonstrated to function as near‐infrared (NIR) light triggerable and deformation‐free hydrogel materials. Periodic NIR laser switching is applied to stimulate these hydrogel particles, and pulsatile release profiles are collected. Compared with massive reagents released from single‐compartmental hydrogel particles, more regulated release profiles of the multi‐compartmental hydrogel particles are observed.