Control Of Surface Chemistry Research Articles

Polymer design and component selection contribute to uptake, distribution & trafficking behaviours of polyethylene glycol hyperbranched polymers in live MDA-MB-468 breast cancer cells.

As polymeric nanomedicines grow increasingly complex in design, an effective therapeutic release is often inherently tied to localisation to specific intracellular compartments or microenvironments. The inclusion of environmentally-sensitive moieties links the functionality of such materials to the trafficking behaviours exhibited once materials have obtained access to the cellular milieu. In order to perform their designed function, such materials often need to encounter specific biological cues or stimuli. As such, there is an increased need to improve our understanding of how the physicochemical properties of nanomaterials influence post-internalisation behaviours. Amongst the unknown factors that may contribute to the trafficking behaviours and distribution of polymers within the cellular environment, is the influence of the components selected in the development of such materials. To examine whether composition and arrangement of components within small polymeric nanomaterials contribute to their ability to navigate the intracellular space, here we utilise fluorophores to model component selection, varying the fluorescent handle selected and its method of incorporation. We explore the intracellular behaviours of well-characterised hyperbranched polymers in live MDA-MB-468 breast cancer cells in vitro. Changes in distribution as a function of both fluorophore selection and placement are reported, and our data suggest that the individual components used to produce potential nanomedicines are critical to their overall functioning and efficacy. Further to this, through the use of a novel non-conjugated targeting ligand, we demonstrate that there is inherent competition between component-directing factors and cellular influences on the ultimate fate of the polymers. The behaviours reported here suggest that not only does component selection contribute to intracellular processing, but these factors could potentially be harnessed when designing polymers to ensure improved functionality of future materials for therapeutic delivery.

Smart Wetting Control on Shape Memory Polymer Surfaces.

Control of surface wettability is very important, and can be realized by controlling surface chemistry or microstructures. Compared with surface chemistry, smart control of surface microstructure is more difficult. Recently, shape memory polymers (SMPs) have advanced to allow control of the surface microstructure and wettability, and thus, demonstrate excellent controllability and many novel functions. In this Minireview, recent achievements in wetting control on SMP surfaces with general hydrophobic, superhydrophobic, superomniphobic and superslippery properties are presented. Particular attention is paid to superhydrophobic surfaces, which display many novel functions, such as switchable isotropic/anisotropic wetting and reprogrammable gradient wetting. Furthermore, a new strategy that combines responsive molecules with the SMP microstructure is also described; this can be used to realize precise wetting control based on coordinated regulation of both surface microstructure and chemistry.

Electrospinning of Cyclodextrin Functional Nanofibers for Drug Delivery Applications.

Electrospun nanofibers have sparked tremendous attention in drug delivery since they can offer high specific surface area, tailored release of drugs, controlled surface chemistry for preferred protein adsorption, and tunable porosity. Several functional motifs were incorporated into electrospun nanofibers to greatly expand their drug loading capacity or to provide the sustained release of the embedded drug molecules. In this regard, cyclodextrins (CyD) are considered as ideal drug carrier molecules as they are natural, edible, and biocompatible compounds with a truncated cone-shape with a relatively hydrophobic cavity interior for complexation with hydrophobic drugs and a hydrophilic exterior to increase the water-solubility of drugs. Further, the formation of CyD-drug inclusion complexes can protect drug molecules from physiological degradation, or elimination and thus increases the stability and bioavailability of drugs, of which the release takes place with time, accompanied by fiber degradation. In this review, we summarize studies related to CyD-functional electrospun nanofibers for drug delivery applications. The review begins with an introductory description of electrospinning; the structure, properties, and toxicology of CyD; and CyD-drug complexation. Thereafter, the release of various drug molecules from CyD-functional electrospun nanofibers is provided in subsequent sections. The review concludes with a summary and outlook on material strategies.

Arene C[sbnd]H insertion catalyzed by ferrocene covalently heterogenized on graphene acid

The heterogenation of molecular catalysts on solid supports is a viable route for the preparation of hybrid materials that combine the high selectivity and activity of homogeneous active species with the enhanced stability and recyclability imparted by the heterogeneous nature of the support. In this work we describe the covalent functionalization with ferrocene (Fc) of two graphene derivatives: graphene acid (GA), a graphene layer whose basal plane is modified with COOH groups, and graphene oxide (GO). The surface modification is performed exploiting the carbodiimide chemistry, which allows introducing up to 3.6% at. of iron in the GA-based material. Compared to GO, GA owns a superior functionalization degree, which is attributed to its controlled surface chemistry. Both Fc-modified materials are tested as catalysts in the CH insertion of diazonium salts employing arene substrates. The materials are active, versatile and recyclable catalysts that show a catalytic performance comparable to or even better than molecular Fc, together with a 100% recyclability which does not alter the catalytic performance. The GA-based hybrid catalyst results more active than that based on GO due to the presence of more extended aromatic domains that facilitate the adsorption of the reagents close to the active sites.

Vertical Integration of Cell‐Laden Hydrogels with Bioinspired Photonic Crystal Membranes

AbstractThe native architecture of tissue segregates populations of cells through nanostructured membranes of biopolymers (e.g., basement membranes) which serve the dual purpose of providing scaffolding for cells and filtration through size‐exclusion. A multilayered approach to fabricate tissue scaffolds where populations of encapsulated cells are separated by porous silicon (PSi)‐based photonic crystal membranes with nano‐ and microstructure that mimics the basement membranes is reported here. The PSi films are fabricated to display discreet photonic bandgaps such that remote optical interrogation provides a specific resonance for each film. Through careful control of surface chemistry, nanostructured PSi films are engineered to serve as optical biosensors and biomolecule release reservoirs, where the optical signature can report on these distinct functions remotely using a simple light source. The promise of this approach is demonstrated as a “smart” tissue scaffolding by monitoring matrix metalloprotease (MMP) activity from encapsulated multilayered co‐cultures of mesenchymal stem cells and human microvascular endothelial cells, with concurrent attenuation of MMP activity through release of angiogenic‐modulating compounds. The integration of optically registered biosensing and drug‐release capabilities—within a multilayered hydrogel scaffold with multiple cell types—provides a new approach to tissue engineering where dynamic bioactivity can be monitored remotely in real‐time.

Nanoroughness, Surface Chemistry, and Drug Delivery Control by Atmospheric Plasma Jet on Implantable Devices.

Implantable devices need specific tailored surface morphologies and chemistries to interact with the living systems or to actively induce a biological response also by the release of drugs or proteins. These customized requirements foster technologies that can be implemented in additive manufacturing systems. Here, we present a novel approach based on spraying processes that allow to control separately topographic features in the submicron range (∼60 nm to 2 μm), ammine or carboxylic chemistry, and fluorophore release even on temperature-sensitive biodegradable polymers such as polycaprolactone (PCL). We developed a two-steps process with a first deposition of 220 nm silica and poly(lactic- co-glycolide) (PLGA) fluorescent nanoparticles by aerosol followed by the deposition of a fixing layer by an atmospheric pressure plasma jet (APPJ). The nanoparticles can be used to create the nanoroughness and to include active molecule release, while the capping layer ensures stability and the chemical functionalities. The process is enabled by a novel APPJ which allows deposition rates of 10-20 nm·s-1 at temperatures lower than 50 °C using argon as the process gas. This approach was assessed on titanium alloys for dental implants and on PCL films. The surfaces were characterized by Fourier transform infrared, atomic force microscopy, and scanning electron microscopy (SEM). Titanium alloys were tested with the preosteoblast murine cells line, while the PCL film was tested with fibroblasts. Cell behavior was evaluated by viability and adhesion assays, protein adsorption, cell proliferation, focal adhesion formation, and SEM. The release of a fluorophore molecule was assessed in the cell growing media, simulating a drug release. Osteoblast adhesion on the plasma-treated materials increased by 20% with respect to commercial titanium alloy implants. Fibroblast adhesion increased by a 100% compared to smooth PCL substrates. The release of the fluorophore by the dissolution of the PLGA nanoparticles was verified, and the integrity of the encapsulated drug model was confirmed.

Organic Media Superwettability: On-Demand Liquid Separation by Controlling Surface Chemistry.

Superwettability involving water affinity has demonstrated prominent advantages in oil-water separation. However, superwetting surfaces in nonpolar liquid-polar liquid systems are rarely explored for the separation of organic liquids. In this work, a protocol of elaborately controlling surface chemistry is presented to construct dual superlyophobic surfaces for polar or nonpolar liquids in opposite organic media. On two kinds of silver-roughened copper coatings, a polar hydroxyl group is subtly integrated with nonpolar perfluoroalkyl chain at the nanoscale. Prewetted by one organic liquid, the obtained dual superlyophobic mesh can selectively intercept other immiscible organic liquids, realizing high-efficiency on-demand separation. In theory, the dual superlyophobic surfaces in organic media are strongly dependent on their affinity toward polar liquids and the surface roughness. The discovery may promote the development of organic liquid-related interfacial materials.

Colloidal suspensions of monodisperse diamond core-shells

We report on an innovative method to synthesize monodispersed diamond core-shells stable in colloidal aqueous suspensions. Starting with an electrostatic seeding of silica particles by detonation nanodiamonds, carefully driven in terms of charge and proportion, we are able to initiate the growth of a carbon coating all around the seeded silica particles in a plasma MPCVD reactor dedicated to powder treatments. The crystalline structure of the carbon coating can be tuned by changing the MPCVD conditions: from nanocrystalline diamond for low methane content to graphite nanoflakes for high methane content. These materials are characterized by FE-SEM, HR-TEM, FTIR and Raman spectroscopy. Preliminary photoluminescence (PL) data are also provided. A chemical post-treatment of the core-shell particles is applied to obtain colloidal stability in neutral aqueous suspensions. The monodispersity and the colloidal stability are assessed using DLS and Zeta measurements. After the removal of the silica core, stable suspensions of diamond hollow spheres are obtained. This new class of diamond-based material may find promising applications in various fields, such as nanomedicine toward a versatile nanotool for drug delivery or biolabeling, catalysis thanks to its controllable porosity and carbon surface chemistry or photonics as an elemental block toward bottom-up ordered diamond structures.

Size and shape control of metal nanoparticles in millifluidic reactors

Abstract Engineered metal nanoparticles (metal NPs) possess unique size -dependent optical and electronic properties that could enable new applications in biomedicine, energy generation, microelectronics, micro-optics, and catalysis. For metal NPs to make a mark in these fields, however, new synthetic strategies must be developed that permit NP synthesis on the kilogram scale, while maintaining precise control over NP physiochemical properties (size, shape, composition, and surface chemistry). Currently, NP batch syntheses produce product on the milligram scale and rely on synthetic strategies that are not readily amenable to scale-up. Flow reactor systems (including lab-on-a-chip devices) provide a synthesis platform that can circumvent many of the traditional limitations of batch-scale NP syntheses. These reactors provide more uniform reagent mixing, more uniform heat transfer, opportunities to interface in situ monitoring technology, and allow product yield to be scaled up simply by running multiple reactors in parallel. While many NP syntheses have been successfully transferred to microfluidic reactor systems, microfluidic reactor fabrication is time intensive and typically requires sophisticated lithography facilities. Consequently, millifluidic flow reactors (reactors with channel dimensions of 0.5–10.0 mm) are gaining popularity in NP synthesis. These millifluidic reactors provide many of the same synthetic advantages as microfluidic devices, but are simpler to construct, easier to reconfigure, and more straightforward to interface with in situ monitoring techniques. In this chapter, we will discuss the progress that has been made in developing millifluidic reactors for functionalized metal NP synthesis. First, we will review the basic wet-chemical strategies used to control metal NP size and shape in batch reactors. We will then survey some of the basic principles of millifluidic device design, construction, and operation. We will also discuss the potential for incorporating in situ monitoring for quality control during synthesis. We will conclude by highlighting some particularly relevant examples of millifluidic metal NP synthesis that have set new standards for metal NP size, shape, and surface chemistry control. Graphical Abstract: Credit: Sam Lohse

Surface Chemistry Controls Anomalous Ferroelectric Behavior in Lithium Niobate.

Polarization switching in ferroelectric materials underpins a multitude of applications ranging from nonvolatile memories to data storage to ferroelectric lithography. While traditionally considered to be a functionality of the material only, basic theoretical considerations suggest that switching is expected to be intrinsically linked to changes in the electrochemical state of the surface. Hence, the properties and dynamics of the screening charges can affect or control the switching dynamics. Despite being recognized for over 50 years, analysis of these phenomena remained largely speculative. Here, we explore polarization switching on the prototypical LiNbO3 surface using the combination of contact mode Kelvin probe force microscopy and chemical imaging by time-of-flight mass-spectrometry and demonstratepronounced chemical differences between the domains. These studies provide a consistent explanation to the anomalous polarization and surface charge behavior observed in LiNbO3 and point to new opportunities in chemical control of polarization dynamics in thin films and crystals via control of surface chemistry, complementing traditional routes via bulk doping, and substrate-induced strain and tilt systems.

(Invited) Interfacial Engineering of Energy Conversion and Storage Materials Using Atomic Layer Deposition

Nanoscale materials offer several unique opportunities for applications in energy conversion and storage, due to their high surface-to-volume ratios, short transport distances, mechanical strain relaxation, and the ability to tune their material properties. However, despite these potential advantages, increasing surface and interfacial area dramatically can also present challenges. For example, in semiconductor devices such as photovoltaics and photoelectrochemical cells, an increase in surface recombination of excited charge carriers can offset the benefits of nanostructuring. Similarly, in batteries, undesirable side reactions at electrode-electrolyte interfaces, such as electrolyte decomposition and surface passivation, can lead to degradation of performance and limit lifetime. Therefore, in electrochemical engineering of nanostructured electrode materials, we desire the ability to “turn on” the desirable properties, and “turn off” the deleterious effects of moving to the nanoscale. To improve our ability to precisely control surface and interfacial phenomena in nanoscale materials, we require new methods to control surface chemistry and structure with atomic precision, without introducing inhomogeneities that may arise from diffusion limits during surface modification. One technique that simultaneously accomplishes both of these traits is Atomic Layer Deposition (ALD). In the past two decades, there has been an explosion of research in ALD for interfacial modification of nanostructured materials for energy conversion and storage. However, much of this work has been empirical in nature, and there is often a fundamental lack of understanding of the coupled surface chemistry, structure, and performance relationships at the atomic scale. To overcome this limitation, we must complement ALD interfacial modification with atomically-precise characterization methods. We must also pay attention to not only the initial and final surface properties, but develop novel in situ/operando methods to quantitatively evaluate the evolution of surface properties during dynamic device operation. To bridge this gap, our research group focuses on using ALD not only as a tool for surface coating, but as a platform for fundamental research on the coupled surface chemical, electrochemical, structural, and mechanical evolution that occurs during operation. In this talk, I will present examples in our work on atomically-precise control of electrode-electrolyte interfaces in rechargeable batteries and photoelectrochemical cells. Examples will include development of superionic lithium solid electrolytes by ALD that enable conformal coating of 3-D battery architectures and interfacial modification of all-solid-state batteries1, control of lithium metal anode electrodeposition and dissolution2, and fabrication of 3-D hierarchical photoelectrodes for artificial photosynthesis and water purification3,4. Common to each of these examples is the ability to decouple beneficial and detrimental processes that occur at the interface, and perform materials design optimization at the atomic scale. Beyond purely performance metrics, and emphasis will be placed on gaining new fundamental mechanistic insight into the origins of improved surface behavior, which provides a perspective on the opportunities that surface and interfacial engineering at the atomic scale provides. E. Kazyak, K.-H. Chen, K. N. Wood, A. L. Davis, T. Thompson, A.R. Bielinski, A. J. Sanchez, X. Wang, C. Wang, J. Sakamoto, N. P. Dasgupta, Chem. Mater. 29, 3785 (2017)E. Kazyak, K. N. Wood and N. P. Dasgupta, Chem. Mater. 27, 6457 (2015).E. Rodríguez, S. P. Agarwal, S. An, E. Kazyak, D. Das, W. Shang, R. Skye, T. Deng, and N. P. Dasgupta, ACS Appl. Mater. Interfaces 10, 4614 (2018)Lee, A. R. Bielinski, E. Fahrenkrug, N. P. Dasgupta, and S. Maldonado, ACS Appl. Mater. Interfaces. 8, 16178 (2016)

Efficient synthesis of nitrogen and oxygen co-doped hierarchical porous carbons derived from soybean meal for high-performance supercapacitors

Adopting an impregnation strategy, the homogeneous and efficient pore-creating are simultaneously achieved by one-pot KOH activation making full use of the swelling feature of hydrophilic soybean protein gels in alkaline solution. N, O co-doped porous carbons (NOPCs) have been fabricated using soybean meal as carbon, nitrogen and oxygen sources for an abundance of protein with a smaller amount of corrosive KOH. The as-obtained NOPCs exhibit advantageous characteristics for electrochemical energy storage including unique honeycomb-like morphology with interconnected carbon frameworks, high specific surface area, hierarchical porosity and controllable surface chemistry, which provides a large number of favorable nanochannels with suitable surface property for fast electrolyte diffusion and efficient electron transfer in the carbon networks. When tested as supercapacitor electrodes with symmetric configuration in 3 M KOH electrolyte, the NOPC-700 electrode prepared at 700 °C with a KOH/soybean meal mass ratio of 0.25 presents a high specific capacitance (330 F g−1 at 0.5 A g−1), remarkable cycling stability (94.6% capacitance retention after 10000 cycles at 2.5 A g−1), and superior rate capability (270 F g−1 at 5 A g−1). Furthermore, the NOPC-700//NOPC-700 supercapacitor delivers a maximum energy density of 8.4 Wh kg−1. The coordination between protein-rich soybean meal and one-pot KOH activation plays an important role in efficiently synthesizing porous carbons with robust energy storage performance for supercapacitors.

Moderate pressure plasma source of nonthermal electrons

Plasma sources of electrons offer control of gas and surface chemistry without the need for complex vacuum systems. The plasma electron source presented here is based on a cold cathode glow discharge (GD) operating in a dc steady state mode in a moderate pressure range of 2–10 torr. Ion-induced secondary electron emission is the source of electrons accelerated to high energies in the cathode sheath potential. The source geometry is a key to the availability and the extraction of the nonthermal portion of the electron population. The source consists of a flat and a cylindrical electrode, 1 mm apart. Our estimates show that the length of the cathode sheath in the plasma source is commensurate (~0.5–1 mm) with the inter-electrode distance so the GD operates in an obstructed regime without a positive column. Estimations of the electron energy relaxation confirm the non-local nature of this GD, hence the nonthermal portion of the electron population is available for extraction outside of the source. The use of a cylindrical anode presents a simple and promising method of extracting the high energy portion of the electron population. Langmuir probe measurements and optical emission spectroscopy confirm the presence of electrons with energies ~15 eV outside of the source. These electrons become available for surface modification and radical production outside of the source. The extraction of the electrons of specific energies by varying the anode geometry opens exciting opportunities for future exploration.

Surface Chemistry Mechanism of Ultra-Low Interfacial Resistance in the Solid-State Electrolyte Li7La3Zr2O12

The garnet-type solid-state electrolyte, based on the nominal formula Li7La3Zr2O12 (LLZO), is unique in that it is a fast Li-ion conductor, exhibits sufficient mechanical properties, and is also chemically and electrochemically stable against metallic Li. Despite these promising attributes, additional challenges must be overcome before solid-state batteries based on LLZO are viable. Demonstrating low Li–LLZO interfacial resistance (R Li–LLZO) is a critical milestone along the path to commercialization. While several studies have characterized R Li–LLZO, nearly all report values significantly higher than conventional LIBs employing liquid electrolytes. Thus, strategies to reduce R Li–LLZO to values comparable to, or lower than, LIBs are needed [1]. In this study, the impact of surface chemistry on the interfacial resistance between the LLZO solid-state electrolyte and a metallic Li electrode is revealed [1]. Control of surface chemistry allows the interfacial resistance to be reduced to 2 Ω cm2, lower than that of liquid electrolytes, without the need for interlayer coatings. A mechanistic understanding of the origins of ultra-low resistance is provided by quantitatively evaluating the linkages between interfacial chemistry, Li wettability, and electrochemical phenomena. A combination of Li contact angle measurements, X-ray photoelectron spectroscopy (XPS), first-principles calculations, and impedance spectroscopy demonstrates that the presence of common LLZO surface contaminants, Li2CO3 and LiOH, result in poor wettability by Li and high interfacial resistance. On the basis of this mechanism, a simple procedure for removing these surface layers is demonstrated, which results in a dramatic increase in Li wetting and the elimination of nearly all interfacial resistance. The low interfacial resistance is maintained over one-hundred cycles and suggests a straightforward pathway to achieving high energy and power density solid-state batteries. [1] A. Sharafi, E. Kazyak, A. L. Davis, S. Yu, T Thompson, D. J. Siegel, N. P. Dasgupta, J. Sakamoto, Chem. Mater. 29, 7961(2017)

Engineering Surface-Binder Interactions in High Energy Density Nanowire Conversion Electrodes for Improved Cycle Life without Fluorinated Additives

High capacity conversion electrode materials – like silicon and germanium – that undergo a large volume change upon lithiation and delithiation, require the formation of a robust solid-electrolyte interphase (SEI) layer, which is critically important to mitigate deleterious irreversible reactions that occur at the electrode-electrolyte interface. Over time, these irreversible reactions at the electrode surface result in capacity fade by decreasing the number of mobile lithium ions within the cell and by creating a more hindered diffusion path for lithium ions as they travel toward the electrode. To combat the recurrence of these irreversible reactions in high-capacity conversion electrode systems, the addition of electrolyte additives, such as fluoroethylene carbonate (FEC), is typically deemed necessary to promote stable cycling and improve capacity retention. The observed improvements associated with the inclusion of these virtually universally employed additives have been previously attributed to fluorinated reductive decomposition products that enable the formation of a robust SEI layer. Clearly, careful control over interfacial chemistry and surface reactions are critical for the design of robust electrochemical systems; however, the surface chemistry of the active material is typically ignored prior to electrode formulation. In most studies of high capacity conversion electrode materials, the surfaces remained unmodified, and the active material is incorporated irrespective of what uncontrolled – potentially oxidized – surfaces happen to be present in the native state. Herein, we systematically investigate the electrochemical cycling of germanium nanowire composite conversion electrodes with controlled surface chemistry, formulated with an array of polymeric binders, both in the presence and in the absence of fluorinated electrolyte additives. We observe that controlled modification of the nanowire electrode surface, when paired with certain binders, dramatically improved germanium nanowire-based electrode cycling retention and longevity. In fact, some of these pairings exhibit improved capacity retention in the absence of the fluorinated additives typically deemed necessary for stable cycling, whereas the addition of the fluorinated additive caused the cell capacity to fade more rapidly. Finally, through careful control of surface chemistry and strategic choice of binder material, we show that germanium nanowire-based conversion electrodes can maintain capacity retention in the complete absence of fluorinated additives, fluorinated electrolytes, and fluorinated binders.

Study of coal cleaning rejects by FIB and sample preparation for HR-TEM: Mineral surface chemistry and nanoparticle-aggregation control for health studies

Abstract Nano-minerals and amorphous nanoparticles play a vital role in the contexts of human health and environmental sustainability. For instance, aerosols generated by the process of coal beneficiation adversely affect human health as well as the environment. These are called Coal Cleaning Rejects (CCRs). They mainly contain clay minerals, nano-quartz, different particles of Fe/Al, and other Hazardous Elements (HEs) and compounds in minute quantities. In this work, we studied the CCRs of industrial facilities in Brazil for the presence of nanoparticles/nanominerals and HEs. CCRs were characterized using Focused Ion Beam (FIB) to evaluate nano-compound assemblages with high resolution-transmission electron microscopy/energy dispersive spectroscopy (HR-TEM/EDS) to assess the extent of risk to human health. In the present work, the importance of nanogeoscience in the description of CCRs and HEs in several secondary phases deposits (e.g. Fe and Al-sulfates, oxides and hydroxides minerals) has been emphasized and the presence of HEs in Brazilian coal abandoned area has been confirmed. This innovative study used an advanced characterization that will be useful in understanding the extent of environmental risk as well as a threat to human health, associated with CCRs.

Tunable Bifunctional Activity of Mnx Co3-x O4 Nanocrystals Decorated on Carbon Nanotubes for Oxygen Electrocatalysis.

Noble‐metal‐free electrocatalysts are attractive for cathodic oxygen catalysis in alkaline membrane fuel cells, metal–air batteries, and electrolyzers. However, much of the structure–activity relationship is poorly understood. Herein, the comprehensive development of manganese cobalt oxide/nitrogen‐doped multiwalled carbon nanotube hybrids (MnxCo3−xO4@NCNTs) is reported for highly reversible oxygen reduction and evolution reactions (ORR and OER, respectively). The hybrid structures are rationally designed by fine control of surface chemistry and synthesis conditions, including tuning of functional groups at surfaces, congruent growth of nanocrystals with controllable phases and particle sizes, and ensuring strong coupling across catalyst–support interfaces. Electrochemical tests reveal distinctly different oxygen catalytic activities among the hybrids, MnxCo3−xO4@NCNTs. Nanocrystalline MnCo2O4@NCNTs (MCO@NCNTs) hybrids show superior ORR activity, with a favorable potential to reach 3 mA cm−2 and a high current density response, equivalent to that of the commercial Pt/C standard. Moreover, the hybrid structure exhibits tunable and durable catalytic activities for both ORR and OER, with a lowest overall potential of 0.93 V. It is clear that the long‐term electrochemical activities can be ensured by rational design of hybrid structures from the nanoscale.

The optimization and production of stable homogeneous amine enriched surfaces with characterized nanotopographical properties for enhanced osteoinduction of mesenchymal stem cells.

Silane modification has been proposed as a powerful biomaterial surface modification tool. This is the first comprehensive investigation into the effect of silane chain length on the resultant properties of -NH2 silane monolayers and the associated osteoinductive properties of the surface. A range of -NH2 presenting silanes, chain length 3-11, were introduced to glass coverslips and characterized using water contact angles, atomic force microscopy, X-ray photoelectron spectroscopy, and Ninhydrin assays. The ability of the variation in chain length to form a homogenous layer across the entirety of the surfaces was also assessed. The osteoinductive potential of the resultant surfaces was evaluated by real-time polymerase chain reaction, immunocytochemistry, and von Kossa staining. Control of surface chemistry and topography was directly associated with changes in chain length. This resulted in the identification of a specific, chain length 11 (CL11) which significantly increased the osteoinductive properties of the modified materials. Only CL11 surfaces had a highly regular nano-topography/roughness which resulted in the formation of an appetite-like layer on the surface that induced a significantly enhanced osteoinductive response (increased expression of osteocalcin, CBFA1, sclerostin, and the production of a calcified matrix) across the entirety of the surface. © 2018 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1862-1877, 2018.

Significantly improved rubber-silica interface via subtly controlling surface chemistry of silica

It has been commonly acknowledged that particle dispersion and interfacial interactions are vital in determining the ultimate performance of polymer composites. However, the interplay between dispersibility and interfacial interaction in polymer composites has not been explicitly unraveled. In this contribution, a series of silica with controlled surface chemistry are prepared to reveal the effects of subtle change in surface property of filler on the structures and mechanical performance of the rubber composites. On the basis of thermodynamic theory, the dispersibility of modified silica in rubber is quantitatively evaluated by using surface energy. The modified silica was introduced into styrene-butadiene rubber (SBR) to investigate the effects of surface modification on the dispersion of silica and interfacial interaction of the rubber composites. It has been demonstrated that subtle change in surface chemistry of silica drastically improves its dispersibility in rubber matrix, leading to much improved accessible surfaces and hence much complete interfacial reaction. At very low grafting content (0.2 molecule/nm2), improved modulus (44%) and wet-traction (54%), together with reduced rolling-resistance (11%), are concurrently observed.

Mineral surface chemistry control for origin of prebiotic peptides

Some seventy years ago, John Desmond Bernal proposed a role for clays in the origin of life. While much research has since been dedicated to the study of silicate clays, layered double hydroxides, believed to be common on the early Earth, have received only limited attention. Here we examine the role that layered hydroxides could have played in prebiotic peptide formation. We demonstrate how these minerals can concentrate, align and act as adsorption templates for amino acids, and during wetting—drying cycles, promote peptide bond formation. This enables us to propose a testable mechanism for the growth of peptides at layered double hydroxide interfaces in an early Earth environment. Our results provide insights into the potential role of mineral surfaces in mimicking aspects of biochemical reaction pathways.