Well-controlled Surface Research Articles

Electrochemical and in Situ Raman Spectroscopic Characterization of Ni Surface Using Inorganic Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

・Introduction Anion exchange membrane water electrolyzer (AEMWE) is expected to reduce the production cost by using base metals for the electrocatalysts and to have high electrolytic efficiency due to its membrane electrode assembly (MEA) structure. The improvement of electrochemical activity and durability of the catalysts remains one of the essential issues for practical application. At present, Ni based oxide is one of the essentially candidate catalysts for both the anode and cathode of AEMWE.Ni is easily oxidized and formed the oxygen-containing adsorbates. The formation of Ni surface oxides depends strongly on the synthesis condition, dopant elements, and the applied potentials. Their peak assignment in the potential-dependent spectra are only possible with well-controlled surfaces. Therefore, an accurate understanding of the surface states and the catalytic reaction process on Ni oxide surface requires the Ni catalyst with well-controlled surface and a highly sensitive analytic technique. Herein, we introduced the inorganic shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) to confirm the surface states and surface reaction precisely.The SHINERS is the advanced mode of the surface-enhanced Raman Scattering (SERS) and can detect the Raman signals enhanced by the local electromagnetic field generated on the surface of the nano-amplifier by an applied laser. The SERS has some priorities to detect the signals non-destructively at in situ/operando conditions from extremely small amount of samples at the molecular level, such as self-assembled monolayers and partial surface adsorbates. Introduction of the inorganic shell on the surface of nano-amplifier prevents direct contact and interaction between the sample and the nano-amplifier, selectively detecting intrinsic surface information of samples. In this experiment, the SHINERS technique can provide spectral features of the thin layers of the Ni oxide with high sensitivity and surface selectivity to detect the surface adsorbates in detail.・Experiment In situ SHINERS measurements were performed in 0.1 mol L-1 KOH aqueous electrolyte (Ar-saturated) at room temperature, using a homemade in situ Raman cell equipped with a Ag/AgCl reference electrode and a Pt counter electrode, while all potentials were quoted vs. the reversible hydrogen electrode (RHE). In the Raman measurements, Au nanoparticles coated with an alkaline-resistant zirconia shell were introduced as an optical nano-amplifier at the surface coverage of ca. 20%. Raman spectra were acquired using the Confocal Microscope Laser Raman Spectrometer (Horiba Jobin Yvon LabRAM HR Evolution). The excitation laser source was 632.8 nm He-Ne laser with the typical power of max. 0.1 mW on the surface. The spectrometer was equipped with an 800 mm focal length monochrometer with a long working distance objective lens (50× magnification, OLYMPUS).・Results and discussion Electrochemical measurements and in situ SHINERS have captured a detail surface features at different potential range, including the redox profile between metallic Ni and α-Ni(OH)2, the phase transition from α-Ni(OH)2 to β-Ni(OH)2, as well as the oxidation process from β-Ni(OH)2 to β-Ni(O)OH on a flat Ni electrode in alkaline condition, together with the formation of the γ-Ni(O)OH and the precursor species of the oxygen evolution reaction (OER) on the Ni electrode. Weak bands of each oxygen-containing adsorbate in the few layers of surface oxide film were assigned in the function of applied potential, revealing difference with those in literatures observed on the thick layers of Ni oxides. In situ SHINERS studies, incorporated with the electrochemical studies, on a flat Ni electrode allow us to propose a general scheme presenting relationships between the metallic Ni and various oxygen-containing adsorbates formed during the potential scan in the range between hydrogen and oxygen evolution reaction. In addition, the potential-dependent catalytic activity of Ni surface and nano-catalysts with be discussed at the conference. Figure 1

(Invited) Synthetic Strategies to Lower the Barrier for Making High Quality Quantum Dot Probes

Quantum dot (QD)-based bioimaging requires QDs with exceptional optical quality and well-controlled surface properties. Although extensive research has been carried out to produce high-quality nanocrystals and to design biocompatible ligands, significant expertise is required to synthesize the best quality QDs and ligands reported. Commercially available QDs often fail to meet the required quality and suffer from irreproducibility in their performance. These restrictions have limited the wide adoption of QDs for biomedical imaging in non-expert groups. My group strives to lower the barrier to preparing high-quality QD probes in a wide range of wavelengths. In this talk, I will discuss the synthetic strategies that we have developed to systematically grow high-quality nanocrystals of various sizes and materials with minimal human intervention and simplify the synthesis of polyimidazole ligands without compromising their quality. By lowering the synthetic barrier to high-quality QDs, we envision unleashing the full potential of QDs in various fields.

Facile design of amphiphobic PVDF membranes utilizing synergy of pore structure and surface fluorination: A demonstration in membrane distillation

Amphiphobic membranes have attracted much attention in membrane distillation (MD) applications, due to its potential in simultaneously resisting membrane wetting and fouling when treating complex wastewater. The current amphiphobic membranes often require non-trivial design of multilevel re-entrant structure. Here we proposed a new class of amphiphobic membranes without multilevel re-entrant surface, by creating a composite poly(vinylidene fluoride)/polyvinyl alcohol/SiO2 membrane with asymmetric structure and well-controlled small surface pores via the NTIPS method, followed by direct fluorination via chemically binding the –OH of polyvinyl alcohol and low surface energy moieties 1H,1H,2H,2H-perfluorodecyl-triethoxysilane, assisted by 3-aminopropyltriethoxysilane and trimesoyl chloride. The amphiphobic membrane showed superior liquid entry pressure above 5 bar with various simulated saline feeds containing surfactants and organic pollutants. The amphiphobic membrane demonstrated robust anti-wetting and anti-fouling performance through a series of 24-h direct contact MD experiments using the above feeds, presenting stable water flux and high rejection, e.g., flux of 50.6 kg/(m2·h) and rejection >99.9 % with feed containing 3.5 wt% NaCl, 1 mM FA, and 2 mM SDS. The results demonstrated the fabrication of robust amphiphobic membrane through simple procedure utilizing the synergy between pore structure and surface chemistry, inspiring more efforts to design adequate membranes for treating complex wastewater.

Boosting the capacity and stability of Na3V2(PO4)2F3-2xO2x microspheres, using atomic layer deposition of artificial CEI

Phosphate-based materials [e.g. Na3V2(PO4)2F3-2xO2x; (NVPFO2x;0 < x < 1)] are regarded as a promising intercalation cathodes for Sodium-ion batteries (SIBs) due to their high reversible specific capacity and stability. However, so far only 2 Na ion were demonstrated to be active in these polyanionic cathodes, which limit their capacity. Herein we provide a strategic approach towards electrochemical activation of a 3rd Na ion, which leads to higher capacity, and preserves structural integrity. We synthesize and study a series of NVPFO2x (0 < x < 1) with well-controlled surface morphology and vanadium oxidation state, and study the dependence of the electrochemical behavior on the various composition and morphology. The optimized NVPFO cathode exhibited highest initial specific discharge capacity (131 mA h g−1) indicating the activation of 3rd Na ion. Nevertheless, the material suffers rapid capacity fading within ~50 cycles. We demonstrate how this instability is suppressed profoundly through the formation of a thin artificial cathode electrolyte interface (CEI) layer of TiO2 (ca. 2 nm) on the surface of NVPFO by atomic layer deposition (ALD). This TiO2 coating enabled even further extraction of sodium through higher voltage domain, but more importantly, it facilitated excellent long-term stability over 200 cycles. The structural stability of the cathode material was revealed by post cycling HRSEM, XPS, and XRD study. All these studies demonstrate that the thin TiO2 layer effectively contributes to formation of a robust CEI layer, diminishes the parasitic reaction on the electrode surface, reduces carbonate formation, and restricts the electrolyte decomposition.

Influence of Electrospinning Parameters on the Morphology of Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Fibrous Membranes and Their Application as Potential Air Filtration Materials.

A large number of non-degradable materials have severely damaged the ecological environment. Now, people are increasingly pursuing the use of environmentally friendly materials to replace traditional chemical materials. Polyhydroxyalkonates (PHAs) are receiving increasing attention because of the unique biodegradability and biocompatibility they offer. However, the applications of PHAs are still limited due to high production costs and insufficient study. This project examines the optimal electrospinning parameters for the production of PHA-based fibrous membranes for air filtration. A common biodegradable polyester, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), was electrospun into a nanofibrous membrane with a well-controlled surface microstructure. In order to produce smooth, bead-free fibers with micron-scale diameters, the effect of the process parameters (applied electric field, solution flow rate, inner diameter of hollow needle, and polymer concentration) on the electrospun fiber microstructure was optimized. The well-defined fibrous structure was optimized at an applied electric field of 20 kV, flow rate of 0.5 mL/h, solution concentration of 12 wt.%, and needle inner diameter of 0.21 mm. The morphology of the electrospun PHBV fibrous membrane was observed by scanning electron microscopy (SEM). Fourier transform infrared (FTIR) and Raman spectroscopy were used to explore the chemical signatures and phases of the electrospun PHBV nanofiber. The ball burst strength (BBS) was measured to assess the mechanical strength of the membrane. The small pore size of the nanofiber membranes ensured they had good application prospects in the field of air filtration. The particle filtration efficiency (PFE) of the optimized electrospun PHBV fibrous membrane was above 98% at standard atmospheric pressure.

Employing a Thin Artificial CEI Layer on Na3V2 (PO4)2F3-2xO2x (0 < x < 1) by Atomic Layer Deposition; Structure Stabilization and Capacity Enhancement

Sodium ion battery (SIB), still facing the limit in functionality due to lower energy density; arises from either low capacity or narrow potential window. The capacity improvement within material sustainability is one major challenge which needs to be addressed to satisfy the present demand for SIB. Of late phosphate-based materials [Na3V2(PO4)2F3-2xO2x; (NVPFO2x;0 < x < 1)] are established as prospective cathodes for Sodium-ion battery (SIB) due to high reversible capacity and stability. However, the reversible extraction and insertion of only 2 Na ion per formula unit in these polyanionic cathodes limit their capacity. Herein we demonstrate a strategic approach towards electrochemical activation of 3rd Na ion which leads to higher capacity and preserves structural stability. We synthesized a series of NVPFO2x (0 < x < 1) with well-controlled surface morphology and vanadium oxidation state and studied the electrochemical behavior on the various composition and morphology. Cycling within the potential window of 1.2V to 4.3V vs Na/Na+ to trigger extra Na ion in the electrochemical activity have shown their explicit behavior depending on morphology. The optimized NVPFO2x shows specific capacity >130 mA h g-1, implies 3rd Na ion activation. However, the material suffers rapid capacity fading within ~ 65 cycles which is tremendously improved through formation of a thin artificial cathode electrolyte interface (CEI) layer of TiO2 on the surface of NVPFO2x by atomic layer deposition (ALD) technique. This TiO2 coating enabled even further extraction of sodium through higher voltage domain, but more importantly, it facilitated excellent long-term stability over 200 cycles. The thin coating explicitly restores the structural and morphological integrity during prolonged electrochemical cycling which established by post cycling XRD, HRSEM and XPS study. The study demonstrated that the thin TiO2 layer on electrode material is effectively diminishes the parasitic reaction, reduces carbonate formation, and increase the stability of the formed CEI and lowers electrolyte decomposition within wide-range potential window.

Bactericidal Ability of Well-Controlled Cationic Polymer Brush Surfaces and the Interaction Analysis by Quartz Crystal Microbalance with Dissipation.

In this study, cationic poly(2-(methacryloyloxy)ethyl) trimethylammonium chloride) (PMTAC) brush surfaces were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP), and their properties were systematically investigated to discuss the factors affecting their bactericidal properties and interactions with proteins. Model equations for the analysis of electrophoretic behaviors were considered for accurate parameter estimation to indicate the charge density at the interface. The zeta potential dependency of the PMTAC brushes was successfully analyzed using Smolchowski's equation and the Gouy-Chapman model, which describes the diffusive electric double layer. The analysis of the quartz crystal microbalance with dissipation (QCM-D) indicated that the electrostatic interaction promoted protein adsorption, with a large quantity of a negatively charged protein, bovine serum albumin (BSA), being adsorbed. The bactericidal efficiency of the high-graft-density polymer brush (0.45 chains nm-2) was higher than that of the low-graft-density polymer brush (0.06 chains nm-2). To investigate the mechanism of this phenomenon, we applied the dissipation change (ΔD) of QCM-D analysis. The BSA was likewise adsorbed when the brush structure was changed; however, the negative ΔD indicated that the BSA-adsorbed, high-graft-density PMTAC brush became a rigid state. In the bacteria culture media, the behaviors were the same as BSA adsorption, and the high-graft-density polymer brush was also estimated to be more rigid than the low-graft-density polymer brush. Moreover, for S. aureus adhesion after incubating in TSB, a small slope of ΔD/ΔF plots considered initial adsorption of bacteria on the high-graft-density polymer brush strongly interacted compared to that of the low-graft-density polymer brush. The scattered value of the slope of ΔD/ΔF on the high-graft-density polymer brush was considered to be due to the dead bacteria between the bacteria and the polymer brush interface. These investigations for a well-defined cationic polymer brush will contribute to the design of antibacterial surfaces.

Preparation of High-k Polymeric Composites Based on Low-k Boron Nitride Nanosheets with High-Connectivity Lamellar Structure.

Typically, the basic method to enhance the dielectric response of polymer-based composites is to fill giant dielectric ceramic fillers, such as BaTiO3 and CaCu3Ti4O12, into the polymer matrix. Here, by using low-k boron nitride (BN) with well-controlled microstructure and surface, we successfully prepared a high-k polymeric composite, where the improvement in the dielectric constant of the composite even exceeds that of composites containing BaTiO3 and CaCu3Ti4O12 particles at the same weight percent. First, a lamellar boron nitride nanosheet (BNNS) aerogel was prepared by bidirectional freezing and freeze drying, respectively, and then the aerogel was calcined at 1000 °C to obtain the lamellar BNNS skeleton with some hydroxyl groups. Finally, the epoxy resin (EP) was vacuum impregnated into the BNNS skeleton and cured inside to prepare the lamellar-structured BNNSs/EP (LBE) composites. Interestingly, the dielectric constants of LBE with a 10 wt % BNNS content reached 8.5 at 103 Hz, which was higher by 2.7 times than that of pure EP. The experimental data and the finite element simulations suggested that the increased dielectric constants of LBE resulted from the combination of two factors, namely, the lamellar microstructure and the hydroxyl groups. The stacking of the BNNS phase into a highly connected lamellar skeleton significantly increased the internal electric field and the polarization intensity, while the introduction of hydroxyl groups on the BNNS surface further improved the polarization of the composite, resulting in a significant increase in the dielectric constant of the LBE. This work provides a new strategy for improving the dielectric constant through the microstructure design of composites.

Azeotropic Binary Solvent System Containing Nonfluorinated Polymer-Grafted Silica Nanoparticles for the Fabrication of a Superhydrophobic Surface.

This study describes a method for fabricating a superhydrophobic surface on glass via a colloidal deposition technique based on solvent evaporation-induced aggregation. Silica nanoparticles with a low grafting density of long-chain poly(cyclohexyl methacrylate) (PCH) were dispersed in a binary solvent system consisting of tetrahydrofuran (THF) and methanol (MeOH) with an azeotropic point and the nonfluorinated and hydrophobic PCHMA having a solubility parameter similar to that of THF. In the early stages of evaporation, the binary mixtures tend to induce the aggregation of PCH-NP due to the azeotropic point of the solvent components, leading to the formation of surface structures ranging from smooth to rough on the substrate. By adjusting the initial ratio of the binary solvents, a superhydrophobic coating with a water contact angle of 154 ± 2° and a sliding angle of less than 10° was achieved at a THF content of 60 wt %. This facile approach using azeotropes successfully shows that changes in the solvent composition of the binary solvent system during evaporation can be used to prepare superhydrophobic coatings with well-controlled surface structures.

Plasmonic heating effect in SERS-based nanoplastic detection

As interest in nanoplastics (NPs) increases, various detection techniques have been suggested. Among them, surface-enhanced Raman spectroscopy (SERS) has received a lot of attention because it provides the information of molecular fingerprints with outstanding high sensitivity. On the other hand, it has been known in SERS community that the laser irradiation used in SERS measurement causes a plasmonic heating effect in the local hot spot area on the surface. However, such heating effect has not been considered together with the thermofluidic properties of nanoplastics during the measurements. Here, we systematically examined such heating effects on the SERS detection of NPs. We used standard type of polystyrene (PS) and poly (methyl methacrylate) (PMMA) nanoparticles, which are deposited on a well-controlled SERS surface. Dark field spectroscopy allows the optical visualization of individual particles, where laser was irradiated on with controlled power density. We showed that nanoplastics can be locally melted on the SERS surface with increasing laser power, verifying the permeation of nanoplastics into a hotspot. Our results suggest that when measuring nanoplastics by SERS, factors such as laser power, wavelength, substrate property and type of NP should be considered all together.

Metallene-related materials for electrocatalysis and energy conversion.

As a member of graphene analogs, metallenes are a class of two-dimensional materials with atomic thickness and well-controlled surface atomic arrangement made of metals or alloys. When utilized as catalysts, metallenes exhibit distinctive physicochemical properties endowed from the under-coordinated metal atoms on the surface, making them highly competitive candidates for energy-related electrocatalysis and energy conversion systems. Significantly, their catalytic activity can be precisely tuned through the chemical modification of their surface and subsurface atoms for efficient catalyst engineering. This minireview summarizes the recent progress in the synthesis and characterization of metallenes, together with their use as electrocatalysts toward reactions for energy conversion. In the Synthesis section, we pay particular attention to the strategies designed to tune their exposed facets, composition, and surface strain, as well as the porosity/cavity, defects, and crystallinity on the surface. We then discuss the electrocatalytic properties of metallenes in terms of oxygen reduction, hydrogen evolution, alcohol and acid oxidation, carbon dioxide reduction, and nitrogen reduction reaction, with a small extension regarding photocatalysis. At the end, we offer perspectives on the challenges and opportunities with respect to the synthesis, characterization, modeling, and application of metallenes.

E-cadherin-dependent coordinated epithelial rotation on a two-dimensional discoidal pattern.

In vivo, cells collectively migrate in a variety of developmental and pathological contexts. Coordinated epithelial rotation represents a unique type of collective cell migrations, which has been modeled in vitro under spatially confined conditions. Although it is known that the coordinated rotation depends on intercellular interactions, the contribution of E-cadherin, a major cell-cell adhesion molecule, has not been directly addressed on two-dimensional (2D) confined substrates. Here, using well-controlled fibronectin-coated surfaces, we tracked and compared the migratory behaviors of MDCK cells expressing or lacking E-cadherin. We observed that wild-type MDCK II cells exhibited persistent and coordinated rotations on discoidal patterns, while E-cadherin knockout cells migrated in a less coordinated manner without large-scale rotation. Our comparison of the collective dynamics between these two cell types revealed a series of changes in migratory behavior caused by the loss of E-cadherin, including a decreased global migration speed, less regularity in quantified coordination, and increased average density of topological defects. Taken together, these data demonstrate that spontaneous initiation of collective epithelial rotations depends on E-cadherin under 2D discoidal confinements.

Surface Preparation for Single-Molecule Fluorescence Imaging in Organic Solvents.

The development of single-molecule techniques provides opportunities to investigate the properties and heterogeneities of individual molecules, which are almost impossible to be obtained in ensemble measurements. Recently, single-molecule fluorescence microscopy is being applied more and more to study chemical reactions in organic solvents. However, little has been done to optimize the surface preparation procedures for single-molecule fluorescence imaging in organic solvents. In this work, we developed a method to prepare the surface for single-molecule fluorescence imaging in organic solvents with a well-controlled surface density of chemically immobilized dye molecules and a low density of nonspecifically adsorbed impurities. We also compared the surfaces prepared by two different procedures and studied the impacts of the polarities of the solvent and the surface functionality on the quality of prepared surface. We found that higher polarities of both the solvent and the surface functionality provided better control of the surface density of chemically immobilized dyes and helped reduce the nonspecific adsorption of both dyes and fluorescent impurities in organic solvents. We further performed single-molecule fluorescence imaging in DMF and investigated the photophysical properties of dyes and fluorescent impurities, which could be used to filter out false counts in single-molecule fluorescence measurements.

Layer-by-Layer Deposition of 2D CdSe/CdS Nanoplatelets and Polymers for Photoluminescent Composite Materials.

Two-dimensional (2D) semiconductor nanoplatelets (NPLs) are strongly photoluminescent materials with interesting properties for optoelectronics. Especially their narrow photoluminescence paired with a high quantum yield is promising for light emission applications with high color purity. However, retaining these features in solid-state thin films together with an efficient encapsulation of the NPLs is a challenge, especially when trying to achieve high-quality films with a defined optical density and low surface roughness. Here, we show photoluminescent polymer-encapsulated inorganic-organic nanocomposite coatings of 2D CdSe/CdS NPLs in poly(diallyldimethylammonium chloride) (PDDA) and poly(ethylenimine) (PEI), which are prepared by sequential layer-by-layer (LbL) deposition. The electrostatic interaction between the positively charged polyelectrolytes and aqueous phase-transferred NPLs with negatively charged surface ligands is used as a driving force to achieve self-assembled nanocomposite coatings with a well-controlled layer thickness and surface roughness. Increasing the repulsive forces between the NPLs by increasing the pH value of the dispersion leads to the formation of nanocomposites with all NPLs arranging flat on the substrate, while the surface roughness of the 165 nm (50 bilayers) thick coating decreases to Ra = 14 nm. The photoluminescence properties of the nanocomposites are determined by the atomic layer thickness of the NPLs and the 11-mercaptoundecanoic acid ligand used for their phase transfer. Both the full width at half-maximum (20.5 nm) and the position (548 nm) of the nanocomposite photoluminescence are retained in comparison to the colloidal CdSe/CdS NPLs in aqueous dispersion, while the measured photoluminescence quantum yield of 5% is competitive to state-of-the-art nanomaterial coatings. Our approach yields stable polymer-encapsulated CdSe/CdS NPLs in smooth coatings with controllable film thickness, rendering the LbL deposition technique a powerful tool for the fabrication of solid-state photoluminescent nanocomposites.

Surface Decomposition and Healing in Solution-Phase Ligand Exchange for Efficient Colloidal Quantum Dot Solar Cells

The efficiency of solution-processed colloidal quantum dot (CQD) thin-film solar cells has been significantly improved recently. However, there is still potential for efficiency improvements, which can be realized through a deeper understanding of surface chemical treatment for CQDs. In this study, we developed CQD thin-film solar cells with an improved power conversion efficiency (PCE) of 11.97%. We accomplished this by simply controlling the species and their molar concentrations used in the surface chemical treatment in the solutionphase ligand exchange process. Iodine treatment that generates conductive CQDs induces surface defects via cationic decomposition of the CQD surface; healing the CQD surface requires an excess of lead cations in the solution-phase ligand exchange process. Accordingly, we found that manufacturing CQD thin-film solar cells that have high efficiencies requires well-controlled surface treatment to effectively exchange surface ligands and simultaneously minimize surface defects on the CQD surface.

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

There is an obvious gap between efforts dedicated to the control of chemicophysical and morphological properties of catalyst active phases and the attention paid to the search of new materials to be employed as functional carriers in the upgrading of heterogeneous catalysts. Economic constraints and common habits in preparing heterogeneous catalysts have narrowed the selection of active-phase carriers to a handful of materials: oxide-based ceramics (e.g. Al2O3, SiO2, TiO2, and aluminosilicates-zeolites) and carbon. However, these carriers occasionally face chemicophysical constraints that limit their application in catalysis. For instance, oxides are easily corroded by acids or bases, and carbon is not resistant to oxidation. Therefore, these carriers cannot be recycled. Moreover, the poor thermal conductivity of metal oxide carriers often translates into permanent alterations of the catalyst active sites (i.e. metal active-phase sintering) that compromise the catalyst performance and its lifetime on run. Therefore, the development of new carriers for the design and synthesis of advanced functional catalytic materials and processes is an urgent priority for the heterogeneous catalysis of the future. Silicon carbide (SiC) is a non-oxide semiconductor with unique chemicophysical properties that make it highly attractive in several branches of catalysis. Accordingly, the past decade has witnessed a large increase of reports dedicated to the design of SiC-based catalysts, also in light of a steadily growing portfolio of porous SiC materials covering a wide range of well-controlled pore structure and surface properties. This review article provides a comprehensive overview on the synthesis and use of macro/mesoporous SiC materials in catalysis, stressing their unique features for the design of efficient, cost-effective, and easy to scale-up heterogeneous catalysts, outlining their success where other and more classical oxide-based supports failed. All applications of SiC in catalysis will be reviewed from the perspective of a given chemical reaction, highlighting all improvements rising from the use of SiC in terms of activity, selectivity, and process sustainability. We feel that the experienced viewpoint of SiC-based catalyst producers and end users (these authors) and their critical presentation of a comprehensive overview on the applications of SiC in catalysis will help the readership to create its own opinion on the central role of SiC for the future of heterogeneous catalysis.

Dual-Mode Plasmonic Coupling-Enhanced Color Conversion of Inorganic CsPbBr3 Perovskite Quantum Dot Films.

Plasmonic coupling has been demonstrated to be an effective manipulation strategy for emission enhancement in low-dimensional semiconductor materials. Here, dual-mode plasmonic resonances based on a metal dimer structure were proposed to simultaneously enhance the absorption under short-wavelength excitation and excitons' emission at longer wavelengths for CsPbBr3 perovskite quantum dots (QDs). Large-area metal nanodimer arrays with well-controlled local surface plasmon resonance were facilely fabricated by a simple method combined with metal angular deposition and nanosphere lithography. With the addition of an optimized polymethyl methacrylate spacer, the effective plasmonic coupling and interfacial passivation of QDs were successfully achieved in the hybrid system. As a result, the QD films exhibited a significant and approximately 3.95-fold overall fluorescence enhancement when using blue light excitation, showing the novel advantages of dual-mode plasmonic coupling of semiconductor quantum structures for color conversion applications.

Engineering aluminum hydroxyphosphate nanoparticles with well-controlled surface property to enhance humoral immune responses as vaccine adjuvants

Aluminum phosphate adjuvants play a critical role in human inactivated and subunit prophylactic vaccines. However, a major challenge is that the underlying mechanism of immune stimulation remains poorly understood, which impedes the further optimal design and application of more effective adjuvants in vaccine formulations. To address this, a library of amorphous aluminum hydroxyphosphate nanoparticles (AAHPs) is engineered with defined surface properties to explore the specific mechanism of adjuvanticity at the nano-bio interface. The results demonstrate that AAHPs could induce cell membrane perturbation and downstream inflammatory responses, with positively-charged particles showing the most significantly enhanced immunostimulation potentials compared to the neutral or negatively-charged particles. In a vaccine using Staphylococcus aureus (S. aureus) recombinant protein as antigens, the positively-charged particles elicit long-lasting and enhanced humoral immunity, and provide protection in S. aureus sepsis mice models. In addition, when formulated with human papillomavirus type 18 virus-like particles, it is demonstrated that particles with positive charges outperform in promoting serum antigen-specific antibody productions. This study shows that engineering AAHPs with well-controlled physicochemical properties enable the establishment of a structure-activity relationship that is critical to instruct the design of suitable engineered nanomaterial-based adjuvants within vaccine formulations for the benefits of human health.

Directly sputtered nickel electrodes for alkaline water electrolysis

Hydrogen is regarded as a highly clean and renewable future energy resource. Water electrolysis (WE) is the most promising technology to produce hydrogen at large scale without carbon dioxide generation. In this study, we prepared Ni electrodes for alkaline water electrolysis purpose using various methods, including direct sputtering (DC and RF operational modes) and the Raney Ni process, and investigated their morphologies and electrochemical activities in the hydrogen evolution reaction (HER). The DC-sputtered Ni electrode showed well-controlled surface morphology with around 40-fold roughness enhancement, compared to the Ni substrate. Half-cell HER test showed that DC-sputtered Ni electrode provides the best electrochemical performance, including the lowest overpotential of 100 mV at a current density of 50 mA/cm2, and provides the lowest Tafel slope, representing the fastest charge transfer reaction and kinetics of HER. More importantly, for practical application purposes, single-cell test was also conducted to confirm the on/off durability and long-term stability, which showed highly stable electrochemical activity under harsh operational conditions. We expect that our approach will launch a new trajectory for realizing CO2-free, cost-effective, and scalable hydrogen production for industrial application purpose, even in combination with renewable power sources, including solar, wind, and hydro energy.

Noble-metal-free hydroxyapatite activated by facile mechanochemical treatment towards highly-efficient catalytic oxidation of volatile organic compound

Controlling of volatile organic compound (VOC) emitted from industrial processes as most abundant and harmful air pollutant, has become one of the most important global environmental issues due to the rapid urbanization and industrialization. As an alternative and new type catalyst instead of conventional noble-metal nanoparticles widely utilized in oxidative decomposition of VOC, here we report the superior catalytic performance with 100% CO2/CO conversion on hydroxyapatite (HAp, Ca10(PO4)6(OH)2) with structurally well-controlled active surface tailored via facile one-step mechanochemical treatment in ambient air. With detailed characterizations of particle morphology, crystallinity and chemical structure with respects to surface defect/oxygen vacancy formation, acidity/basicity and VOC affinity on HAps activated through different mechanical stresses when altered ball size is utilized in planetary ball-milling assisted mechanochemical process, it was found that the predominant defect/oxygen vacancy generation in PO43− site and enhanced basic site population established by selective mechanochemical activation of c-plane, facilitates the favorable catalytic oxidation route towards highly-efficient CO2/CO conversion of VOC. Regards to the cost-effectiveness and non-toxic nature of HAp, incorporated with the sustainable mechanochemical surface structure tuning process, the results presented in this work opens new strategy in development of novel noble-metal-free catalyst for VOC elimination and environmental cleaning techniques.