Surface Engineering Approach Research Articles

Engineering Iron–Nickel Nanoparticles for Magnetically Induced CO2Methanation in Continuous Flow

Induction heating of magnetic nanoparticles (NPs) is a method to activate heterogeneous catalytic reactions. It requires nano-objects displaying high heating power and excellent catalytic activity. Here, using a surface engineering approach, bimetallic NPs are used for magnetically induced CO2 methanation, acting both as heating agent and catalyst. The organometallic synthesis of Fe30 Ni70 NPs displaying high heating powers at low magnetic field amplitudes is described. The NPs are active but only slightly selective for CH4 after deposition on SiRAlOx owing to an iron-rich shell (25 mL min-1 , 25 mT, 300 kHz, conversion 71 %, methane selectivity 65 %). Proper surface engineering consisting of depositing a thin Ni layer leads to Fe30 Ni70 @Ni NPs displaying a very high activity for CO2 hydrogenation and a full selectivity. A quantitative yield in methane is obtained at low magnetic field and mild conditions (25 mL min-1 , 19 mT, 300 kHz, conversion 100 %, methane selectivity 100 %).

Tailoring all-inorganic cesium lead halide perovskites for robust triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have attracted considerable interests because of their high conversion efficiency from low-frequent mechanical energy to electricity. Robust dielectric materials are critical in enhancing the contact electrification charge density of TENGs. Herein, all-inorganic cesium lead halide (CsPbX3, X = I, Br, Cl) perovskites with tunable morphologies and dielectric properties are synthesized through a facile solvent etching method and applied as the triboelectric materials in perovskite TENGs. The influences of effective contact area and the dielectric properties associated with electron donating capacity of perovskite films are systematically investigated through solvent and compositional engineering. Compared with the all-inorganic perovskite free of etching, the crystal growth conditions are well controlled. In addition, the doping of Cl− or I− ions is in favor of regulating the polarity and electronic structure of the [PbBr6]4- octahedral. Benefitting from the physical surface engineering approaches for enhancing the triboelectric charge density and the chemical doping for regulating dielectric property, an open-circuit voltage of 192 V, a short-circuit current of 16.7 μA and maximum power density of 1.2 W m−2 at a contact frequency of 0.5 Hz are achieved in the champion CsPbBr2.6I0.4 TENG. The discovery of extraordinary dielectric behavior of the perovskite halides may pave the way of perovskite TENGs with boosting triboelectric charge density for mechanical energy harvesting.

Surface Engineering for Advanced Aqueous Supercapacitors: A Review

AbstractAbstract: Considerable attention has been focused on aqueous supercapacitors (SCs), owing to their large power density and excellent cycling stability, which makes them more suitable for high power applications. However, the lower energy densities (E) of aqueous SCs as compared to batteries have impeded their range of commercial applications. To overcome this challenge, intensive studies have been devoted to the topic, in which surface engineering becomes critical to the high‐performance electrode design due to the efficient manipulation of a material surface to boost energy storage while maintaining the integrity of interior of the material. The purpose of this Minireview article is to highlight recent significant breakthroughs realized through surface engineering approaches such as surface functionalization, heterostructure design, and surface charge modulation. Current challenges, emerging trends, and opportunities for advanced SCs are discussed accordingly.

On Friction Reduction by Surface Modifications in the TEHL Cam/Tappet-Contact-Experimental and Numerical Studies

The overall energy efficiency of machine elements and engine components could be improved by using new technologies such as surface modifications. In the literature, surface engineering approaches like micro-texturing and the application of diamond-like carbon (DLC) coatings were frequently studied separately, with focus on a specific model contact and lubrication conditions. The contribution of the current study is to elucidate and compare the underlying friction reduction mechanisms of the aforementioned surface modifications in an application-orientated manner. The study applied the operating conditions of the thermo-elastohydrodynamically lubricated (TEHL) cam/tappet-contact of the valve train. Therefore, tribological cam/bucket tappet component Stribeck tests were used to determine the friction behavior of ultrashort pulse laser fabricated microtextures and PVD/PECVD deposited silicon-doped amorphous carbon coatings. Moreover, advanced surface characterization methods, as well as numerical TEHL tribo-simulations, were utilized to explore the mechanisms responsible for the observed tribological effects. The results showed that the DLC-coating could reduce the solid and fluid friction force in a wide range of lubrication regimes. Conversely, micro-texturing may reduce solid friction while increasing the fraction of fluid friction.

Hybrid Micro Textures – A Multi-Scale Surface Engineering Approach For Enhancing Tribological Characteristics

Hybrid Micro Textures – A Multi-Scale Surface Engineering Approach For Enhancing Tribological Characteristics

Surface-Electron Coupling for Efficient Hydrogen Evolution.

Maximizing the activity of materials towards the alkaline hydrogen evolution reaction while maintaining their structural stability under realistic working conditions remains an area of active research. Herein, we report the first controllable surface modification of graphene(G)/V8 C7 heterostructures by nitrogen. Because the introduced N atoms couple electronically with V atoms, the V sites can reduce the energy barrier for water adsorption and dissociation. Investigation of the multi-regional synergistic catalysis on N-modified G/V8 C7 by experimental observations and density-functional-theory calculations reveals that the increase of electron density on the epitaxial graphene enable it to become favorable for H* adsorption and the subsequent reaction with another H2 O molecule. This work extends the range of surface-engineering approaches to optimize the intrinsic properties of materials and could be generalized to the surface modification of other transition-metal carbides.

Durability and Wear Resistance of Laser-Textured Hardened Stainless Steel Surfaces with Hydrophobic Properties.

Hydrophobic surfaces are of high interest to industry. While surface functionalization has attracted significant interest, from both industry and research, the durability of engineered surfaces remains a challenge, as wear and scratches deteriorate their functional response. In this work, a cost-effective combination of surface engineering processes on stainless steel was investigated. Low-temperature plasma surface alloying was applied to increase surface hardness from 172 to 305 HV. Then, near-infrared nanosecond laser patterning was deployed to fabricate channel-like patterns that enabled superhydrophobicity. Abrasion tests were carried out to examine the durability of such engineered surfaces during daily use. In particular, the evolution of surface topographies, chemical composition, and water contact angle with increasing abrasion cycles were studied. Hydrophobicity deteriorated progressively on both hardened and raw stainless steel samples, suggesting that the major contributing factor to hydrophobicity was the surface chemical composition. At the same time, samples with increased surface hardness exhibited a slower deterioration of their topographies when compared with nontreated surfaces. A conclusion is made about the durability of laser-textured hardened stainless steel surfaces produced by applying the proposed combined surface engineering approach.

Interface Engineering of Co(OH)2/Ag/FeP Hierarchical Superstructure as Efficient and Robust Electrocatalyst for Overall Water Splitting.

Rational design and preparation of electrocatalyst with optimal component and interfaces, which can work well for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, are of great importance in practical water splitting. Herein, a multiscale structure surface engineering approach to construct Co(OH)2/Ag/FeP hybrid as efficient electrocatalysis for water splitting in alkaline media is reported. By optimizing the component ratio and engineering interfacial structure, the Co(OH)2/Ag/FeP hybrid eletrocatalyst exhibits promoted HER and OER activity as well as stability in alkaline media, achieving an overpotential of 118 and 236 mV at a current density of 10 mA cm-2, respectively. Further experimental characterizations demonstrate the electron structure changes in Co(OH)2/Ag/FeP hybrid after constructing the interfaces, which is beneficial to generate low-charge state Fe2+ and high-oxidized Co3+/4+. The first-principle calculations reveal that the dissociation of H2O at the interface region is energetically favorable, which is responsible for the enhanced HER and OER activity. Furthermore, two-electrode alkaline water electrolyzer constructed by Co(OH)2/Ag/FeP hybrid electrocatalysts only requires a voltage of 1.56 V to afford a current density of 10 mA cm-2, which is superior to the commercial Pt/C-IrO2 catalytic couple and makes it a promising material to be employed as effective bifunctional catalysts for overall water splitting.

Microstructure and properties of Al and Al-Cr coatings on nickel-based superalloy GH625 by a thermal diffusion process

Aluminide coating has been known as one of the best surface engineering approaches to combat high temperature corrosion in nickel-based superalloy. In this paper, A chromium-modified aluminide coating was prepared on the GH625 by the neutral salt bath method. The microstructure and properties of the modified coating was studied and compared with simple-aluminized coating by scanning electron microscope, x-ray diffraction techniques, depth elemental profiling analysis, microhardness and interface bonding force test. Surface SEM and EDS analysis show that the Al-Cr coating contains more Cr element, finer microstructure and fewer oxide inclusions. Surface XRD analysis shows that the phase structure of Al-Cr coating is different and the α-Cr phase has replaced Ni3Al and Al4CrNi15 phases in the Al coating. Cross section SEM and line scan analysis show that the microstructure of Al-Cr coating is more compact and the element distribution is more uniform than the Al coating. In addition, there is a significantly wider interface zone in the Al-Cr coating than that of Al coating. In the interface zone, there is an obvious Cr-rich area and a wider elemental diffusion area toward the substrate. As the result, the Al-Cr coating has higher microhardness and the interfacial bonding force between the coating and the substrate.

Nanostructured Free-Form Objects via a Synergy of 3D Printing and Thermal Nanoimprinting.

High‐resolution surface patterning has garnered interests as a nonchemical‐based surface engineering approach for creating functional surfaces. Applications in consumer products, parts for transportation vehicles, optics, and biomedical technologies demand topographic patterning on 3D net shape objects. Through a hybrid approach, high‐resolution surface texture is incorporated onto 3D‐printed polymers via direct thermal nanoimprinting process. The synergy of geometry design freedom in 3D printing and the high spatial resolution in nanoimprinting is demonstrated to be a versatile fabrication of high‐fidelity surface pattern (from 2 µm to 200 nm resolution) on convex, concave semicylindrical, and hemispherical objects spanning a range of surface curvatures. The novel hybrid fabrication is further extended to achieve a high‐resolution curved mold insert for rapid prototyping via injection molding. The versatility of the fabrication strategies reported here not only provides a post‐3D printing process that enhances the surface properties of 3D‐printed objects but also opens a new pathway to enable future study on the effects of combining microscale and nanoscale surface texture with macroscopic curvature. Both have been known, individually, as an effective approach to tune surface functionalities.

Surface functionalization of 3D printed polymer scaffolds to augment stem cell response

Three-dimensional (3D) printing by material extrusion is being widely explored to prepare patient-specific scaffolds from biodegradable polyesters such as poly(lactic acid) (PLA). Although they provide the desired mechanical support, PLA scaffolds lack bioactivity to promote bone regeneration. The aim of this work was to develop a surface engineering approach for enhancing the osteogenic activity of 3D printed PLA scaffolds. Macro-porous PLA scaffolds were prepared by material extrusion with 70.2% porosity. Polyethyleneimine was chemically conjugated to the alkali-treated PLA scaffolds followed by conjugation of citric acid. These polymer-grafted scaffolds were immersed in the simulated body fluid to yield scaffolds coated with calcium-deficient hydroxyapatite (PLA-HaP). Surface roughness and water wettability were enhanced after surface modification. PLA-HaP scaffolds exhibited a steady release of calcium ions in an aqueous medium for 10 days. The adhesion and proliferation of human mesenchymal stem cells (hMSCs) on PLA-HaP was ~50% higher than on PLA. Mineral deposition resulting from hMSC osteogenesis on PLA-HaP scaffolds was nearly twice that on PLA scaffolds. This was corroborated by the increase in alkaline phosphatase activity and expression of several osteogenic genes. Thus, this work presents a surface modification strategy to enhance the bioactivity of 3D printed scaffolds for bone tissue regeneration.

Water-lubricated behaviour of AISI 440C stainless steel and a DLC coating for an orbital hydraulic motor application

The low-speed, high-torque, orbital hydraulic motor is a component that often uses mineral oil to convert hydraulic energy into the rotational motion of a shaft. The main purpose of our research was to investigate the possibility of using water, which is a much less environmentally damaging working fluid than oil. The limitations of water lubrication were overcome with an appropriate surface-engineering approach. The surface coated with diamond-like carbon (DLC) significantly reduced both the friction and the wear. The lowest coefficients of friction in this study, taking into account all the tested parameters, were obtained when the stainless-steel/DLC (SS/DLC) contact was tested in water. The friction of the SS/DLC in water was even lower than the friction of the SS/DLC or SS/SS contact in oil. Furthermore, the wear coefficient of the SS/DLC in water was comparable to the wear coefficient of the SS/SS in oil. The surface hardness, surface roughness and applied force were also varied, but they did not play such an important role as employing the DLC coating. The SS/DLC contact can thus be considered as a very promising solution for an orbital hydraulic motor from the tribological and environmental points of view.

Improving Voc With Indium and Alkali Fluorides in Cu(In,Ga)Se2 Solar Cells Deposited at Low Temperature on Polyimide

Flexible, lightweight, Cu(In,Ga)Se2 photovoltaic technology is becoming more and more popular, thanks to the very high efficiencies already achieved (>20%) and to the possible employment of roll-to-roll deposition techniques, offering new application opportunities. In this paper, we aim to improve the understanding and performances of recently discovered new front surface engineering approaches. We show that the improvement of Voc generally observed using heavy alkali (below Na) can be boosted by adding indium during the alkali postdeposition treatments (PDTs). The obtained modification of the absorber using NaF/KF + In PDT leads to an improvement of Voc by 20 mV with respect to NaF/KF PDT and by almost 50 mV with respect to NaF-PDT only. The electrical performances of solar cells prepared with different PDTs are analyzed and discussed in light of structural and optical characterization data, supported by physical modeling. We show that KF PDTs modify the absorber over a thin region close to the surface, and also deep in the bulk of the film. Our results with KF show a record efficiency of 18.1% without antireflecting coating (ARC), a value that is close to the highest reported value of 20.4% (with ARC).

Drug Delivery: Nanoparticles of Metal‐Organic Frameworks: On the Road to In Vivo Efficacy in Biomedicine (Adv. Mater. 37/2018)

In article number 1707365, Patrick Couvreur, Christian Serre, and co-workers evaluate the biomedical applications of metal–organic frameworks at the preclinical stage, for pharmacological applications or toxicity evaluation. Current surface-engineering approaches, in vivo studies, and their prospects are considered. The back cover image illustrates the circulation of drug-loaded MOF nanoparticles in a blood vessel. In particular, nanosized cages of MIL-100(Fe) loaded with Ibuprofen drug are represented. Cover project designed by Maria Mikołajczak-Zygmańska.

Tolerance induction by surface immobilization of Jagged-1 for immunoprotection of pancreatic islets

Although transplantation of pancreatic islets is a promising approach for treatment of type 1 diabetes mellitus, the engraftment efficiency of these islets is limited by host immune responses. Extensive efforts have been made to immunoisolate these islets by introducing barriers on the islet surface. To date, these barriers have not successfully protected islets from attack by the immune system. In addition, the inevitable permeability of an islet capsule cannot prevent filtration by proinflammatory cytokines and islet self-antigens. Thus, we have developed a surface engineering approach for localized immonumodulation of the islet microenvironment. Jagged-1 (JAG-1), as a potent immunomodulatory factor, was immobilized on the islet surface by mediation of a double-layer of heterobifunctional poly (ethylene glycol) (PEG). Immobilization and functionality of JAG-1 on PEGylated islet surfaces were established. When co-cultured with splenocytes, the JAG-1 conjugated islets induced a significant increase in regulatory T cells and regulated the cytokine levels produced by immune cells. The results demonstrated that JAG-1 immobilization could improve immunoprotection of pancreatic islets by localized modulation of the immune milieu from an inflammatory to an anti-inflammatory state. We also evaluated the effects of surface modification of these islets by JAG-1 in a xenotransplantation model. The transplanted JAG-1/PEG/islets group showed a significantly reduced blood glucose levels compared with the control group of diabetic mice during the acute phase of the immune response to the transplanted islets. Our results demonstrated that surface modification has the potential to shift the immune system from an inflammatory to anti-inflammatory milieu and may offer a new prospective for immunoprotection of pancreatic islets.

Surface Engineering of Two‐Dimensional Materials

AbstractTwo‐dimensional (2D) materials have attracted intensive interest because of their unique optical and electronic properties, their potential applications in next generation electronic devices, as well as serving as an ideal platform to explore new physics or chemistry at the 2D limit. As an atomically thin layered material, their atomic/electronic structures and device performances are susceptible to the various surfaces presented. In this regard, plenty of surface modification approaches have been applied to enrich their functionalities and complement their limitations. In this review, we summarize the state‐of‐the‐art progress on the surface engineering of graphene and transition metal dichalcogenides (TMDCs). We begin with the defect and single‐atomic incorporation in graphene lattice and surface transfer doping of graphene, followed by the bandgap and mobility engineering, and the construction of versatile heterostructures of TMDCs. Although this review mainly focuses on graphene and TMDCs, it is not an exhaustive list of the experimental results, but it rather summarizes the established knowledge in surface engineering and pinpoints the most promising future trends. These surface engineering approaches can also be applied to other 2D materials, such as phosphorene and antimonene.

Nanoparticles of Metal-Organic Frameworks: On the Road to In Vivo Efficacy in Biomedicine.

In the past few years, numerous studies have demonstrated the great potential of nano particles of metal-organic frameworks (nanoMOFs) at the preclinical level for biomedical applications. Many of them were reported very recently based on their bioactive composition, anticancer application, or from a general drug delivery/theranostic perspective. In this review, the authors aim at providing a global view of the studies that evaluated MOFs' biomedical applications at the preclinical stage, when in vivo tests are described either for pharmacological applications or for toxicity evaluation. The authors first describe the current surface engineering approaches that are crucial to understand the in vivo behavior of the nanoMOFs. Finally, after a detailed and comprehensive analysis of the in vivo studies reported with MOFs so far, and considering the general evolution of the drug delivery science, the authors suggest new directions for future research in the use of nanoMOFs for biomedical applications.

Microstructure‐property relation in alumina ceramics during post‐annealing process after laser shock processing

AbstractLaser shock processing (LSP) is a new surface engineering approach to introduce significant compressive residual stress into ceramics to improve their mechanical properties. However, LSP of ceramics may induce microcracks, which limit the further improvement of mechanical properties of ceramics. In this research, the effect of a post‐LSP annealing process on α‐Al2O3 ceramics was investigated. The annealing treatment can cause thermal relaxation of compressive residual stress generated by LSP while still maintain the positive attribute of LSP. The compressive residual stress was stabilized after annealing after 10 hours at 1100‐1300°C. The healing of microcracks in α‐Al2O3 ceramics was observed during the post‐LSP annealing process, which is caused by diffusion bonding mechanisms and accompanied by dislocation and void formation. The combination of the stabilized compressive residual stress and microcrack healing can improve the cracking resistance of α‐Al2O3 ceramics to mechanical impact on the surface by 69%.

Label-Free Optical Biodetection of Pathogen Virulence Factors in Complex Media Using Microtoroids with Multifunctional Surface Functionality.

Early detection of pathogens or their virulence factors in complex media has a key role in early diagnosis and treatment of many diseases. Nanomolar and selective detection of Exotoxin A, which is a virulence factor secreted from Pseudomonas aeruginosa in the sputum of Cystic Fibrosis (CF) patients, can pave the way for early diagnosis of P. aeruginosa infections. In this study, we conducted a preliminary study to demonstrate the feasibility of optical biodetection of P. aeruginosa Exotoxin A in a diluted artificial sputum mimicking the CF respiratory environment. Our surface engineering approach provides an effective biointerface enabling highly selective detection of the Exotoxin A molecules in the complex media using monoclonal anti-Exotoxin A functionalized microtoroids. The highly resilient microtoroid surface toward other constituents of the sputum provides Exotoxin A detection ability in the complex media by reproducible measurements. In this study, the limit-of-detection of Exotoxin A in the complex media is calculated as 2.45 nM.

Surface Engineering of Nanoparticles for Targeted Delivery to Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-associated deaths worldwide. There is a lack of efficient therapy for HCC; the only available first-line systemic drug, sorafenib, can merely improve the average survival by two months. Among the efforts to develop an efficient therapy for HCC, nanomedicine has drawn the most attention, owing to its unique features such as high drug-loading capacity, intrinsic anticancer activities, integrated diagnostic and therapeutic functionalities, and easy surface engineering with targeting ligands. Despite its tremendous advantages, no nanomedicine can be effective unless it successfully targets the tumor site, which is a challenging task. In this review, the features of HCC are described, and the physiological hurdles that prevent nanoparticles from targeting HCC are discussed. Then, the surface physicochemical factors of nanoparticles that can influence targeting efficiency are discussed. Finally, a thorough description of the physiological barriers that nanomedicine must conquer before uptake by HCC cells if possible is provided, as well as the surface engineering approaches to nanomedicine to achieve targeted delivery to HCC cells. The physiological hurdles and corresponding solutions summarized in this review provide a general guide for the rational design of HCC targeting nanomedicine systems.