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International audience; Plasma etching techniques can result in damage and contamination of materials, which, if not removed, can interfere with further processing. Therefore, characterisation of the etched surface is necessary to understand the basic mechanisms involved in the etching process and enable process control and cleaning procedures to be developed. A detailed investigation by means of the combined use of scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and optical microscopy (OM) has been carried out on deep titanium trenches etched by plasma. This innovative approach has provided a further insight into the microchemical structure of the surface contamination layer on both the titanium and the nickel hard mask surfaces. The described experiments were conducted on 25 to 100-mu m wide trenches, first etched in bulk titanium by an optimised Cl-2/SF6/O-2-based inductively coupled plasma process, through an electroplated nickel hard mask. The results allow to identify chlorine, fluorine and carbon as the main contaminating agents of the nickel mask and to associate three oxidation states around the etched trenches highlighting certain specific aspects related to the passivation mechanism. These observations reinforce the scientific relevance of the combined use of complementary optical and imaging analytical techniques.

Surface terminations of two-dimensional MXene (Ti3 C2 Tx ) considerably impact its physicochemical properties. Commonly used etching methods usually introduce -F surface terminations or metallic impurities in MXene. We present a new molten-salt-assisted electrochemical etching method to synthesize fluorine-free Ti3 C2 Cl2 . Using electrons as reaction agents, cathode reduction and anode etching can be spatially isolated; thus, no metallics are present in the Ti3 C2 Cl2 product. The surface terminations can be in situ modified from -Cl to -O and/or -S, which considerably shortens the modification steps and enriches the variety of surface terminations. The obtained -O-terminated Ti3 C2 Tx are excellent electrode materials for supercapacitors, exhibiting capacitances of 225 F g-1 at 1.0 Ag-1 , good rate performance (91.1 % at 10 Ag-1 ), and excellent capacitance retention (100 % after 10000 charge/discharge cycles at 10 Ag-1 ), which is superior to multi-layered Ti3 C2 Tx prepared by other etching methods.

Hierarchically porous MOFs (HP-MOFs) present advantageous synergism of micro- and mesopore but challenging in synthetic control at molecular scale. Herein, we present the first example of reversible and controllable mesopore generation and renovation in a microporous MOF of HKUST-1 via synthetic manipulation at molecular scale. An ammonia-gas etching strategy is proposed to create mesopores in carboxylate-based microporous MOFs and thus produce HP-MOFs. Gas-phase etching ensures uniform mesopore formation inside the MOF crystals via plane-oriented cutting the carboxylate-metal bonds off without affecting the crystal size and morphology. The mesopore size is controlled by the etching temperature, while the mesopore volume could be tuned by adjusting etchant pressure. The generated mesopores could be renovated using MOF precursors solutions so that to achieve controllable mesopore generation/closure, and encapsulation of the adsorbed molecules. This work demonstrates a powerful protocol for precisely tailoring and tuning the properties of MOF materials at molecular scale.

The introduction of mesoporosity into the microporous metal-organic frameworks (MOFs) is expected to expand their applications. Herein, we report a green and facile method to obtain hierarchically porous MOF structures by using an air-steam etching process. By virtue of the protonation reaction between the imidazole moiety and water vapor, the protonated imidazole related linkers leave the framework, resulting in the formation of mesopores in the zeolitic imidazolate frameworks (ZIFs), as exemplified by ZIF-8. Given the mild etching process, the materials’ structural integrity and crystallinity are well maintained. Remarkably, the proposed steam etching approach is generally applicable, which can be readily extended to other ZIFs, such as ZIF-14, ZIF-69, and ZIF-71, thus representing a powerful strategy to construct hierarchically porous MOF materials.

Iodide‐mediated surface etching can tailor the surface plasmon resonance of gold nanostars through etching of the high‐energy facets of the nanoparticle protrusions in a rapid and sensitive way. By exploring the underlying mechanisms of this etching and the key parameters influencing it (such as iodide, oxygen, pH, and temperature), we show its potential in a sensitive biosensing system. Horseradish peroxidase‐catalyzed oxidation of iodide enables control of the etching of gold nanostars to spherical gold nanoparticles, where the resulting spectral shift in the surface plasmon resonance yields a distinct color change of the solution. We further develop this enzyme‐modulated surface etching of gold nanostars into a versatile platform for plasmonic immunoassays, where a high sensitivity is possible by signal amplification via magnetic beads and click chemistry., We outline a rapid and sensitive nanoparticle etching‐based strategy for biosensing. Iodide modulates the plasmonic features of gold nanostars by etching them into spherical nanoparticles, being a versatile biosensing platform for enzyme detection and plasmonic immunoassays.

Conventional templating synthesis confines the growth of seeds in rigid spaces to achieve faithful morphological replication. Herein, we explore the use of spherical shape-deformable polymeric nanoshells to regulate the anisotropic growth of Ag nanoplates. The flexible shells deform adaptively to accommodate the initial overgrowth of the seeds but restrict the growth in the directions where the shells are fully stretched, eventually producing nanoplates with an unconventional circular profile. The diameter of the final Ag nanoplates can be precisely predicted by stretching and flattering the nanoshells into a plate-like capsule while retaining their original internal surface area. Furthermore, unlike conventional templates, the polymer shells eventually turn themselves into a conformal coating that binds to the surface of the full-grown Ag nanoplates and significantly enhances their stability against oxidative etching.

The rational design and synthesis of frame-like hollow structures with unique three-dimensional open architectures for their diverse applications is still challenging. We herein propose a facile anisotropic surface modification and etching strategy for the synthesis of hollow structured ZIF-67 nanoframes. Our strategy relies on the structural and compositional distinctions between each crystallographic facet of truncated rhombic dodecahedrons ZIF-67 (tZIF-67 RDs) and the moderate coordinating and etching effects of cyanuric acid (CA). Thereby, the CA can anisotropically modify and protect the {110} facets from etching, causing the six {100} facets be selectively etched via an inside-out manner, and finally forming the hollow nanoframes. Interestingly, the surface modified hollow tZIF-67 RDs can further be facet-selectively etched by metal salts via an outside-in manner to give metal-doped tZIF-67 nanoframes. After calcination in reducing atmosphere, the metal-tZIF-67 hydrids are converted into metal-Co alloy/C composite catalysts with hollow nanoframed structures. Among them, the PtCo/C catalyst with only 5.9 wt.% Pt exhibits high catalytic activities and stabilities in the hydrogen evolution reaction (HER) in acidic solutions, outperforming the commercial 20 wt.% Pt/C catalyst. Our results offer insight into the development of metal-organic frameworks with compositional and structural multiplicity, which in turn could encourages more practical catalytic applications.

Adhesive bond strength at the composite/dentin interface is influenced by various factors, including the etching mode and composite resin type. The purpose of this study was to evaluate the influence of the total-etch and self-etch mode on the microtensile bond strength (μTBS) of conventional and bulk-fill composite to dentin, using the universal adhesive system. Sixty non-carious human teeth were sectioned parallel to their longitudinal axis, using a low-speed diamond saw to obtain a flat dentin surface. According to the etching technique and composite resin type used, teeth were randomly divided into four different groups (n = 15): TC (total-etch/conventional composite), TB (total-etch/bulk-fill composite), SC (self-etch/conventional composite), and SB (self-etch/bulk-fill composite). Cylindric composite build-ups were made with 3M Filtek Z250 and 3M Filtek Bulkfill Posterior, using a plastic mold, 4 mm in diameter and 4 mm in height. The specimens were subjected to the μTBS test in a universal testing machine and failure force was recorded. Failure modes were determined using stereoscopic and scanning electron microscopy. Data were analyzed using the two-way ANOVA and Student's t test. The μTBS was significantly affected by the etching technique. A significant statistical difference was determined between total-etch and self-etch groups, irrespective of the composite resin type used. Higher bond strength was obtained in total-etch groups. The μTBS was not affected by the composite resin type. No significant statistical difference was determined between the conventional and bulk-fill groups, irrespective of the etching-mode.

This in vitro study aimed to assess the influence of different concentrations and durations of hydrofluoric acid (HF) and Monobond Etch & Prime (MEP) etching on the surface roughness (Ra ) of different CAD/CAM materials and on the shear bond strength (SBS) of a self-adhesive resin bonded to the materials. Seventy specimens of hybrid ceramic, leucite-based glass-ceramic, lithium disilicate glass-ceramic, and zirconia-reinforced lithium silicate glass-ceramic were prepared and divided into seven groups according to the surface treatments: Control (C); MEP etching for 60 (MEP60 ) and 120 (MEP120 ) s; 5% HF etching for 60 (HF-5%60 ) and 120 (HF-5%120 ) s; 9.5% HF etching for 60 (HF-9.5%60 ) and 120 (HF-9.5%120 ) s. The Ra was measured using a 3D profilometer. All groups were treated with a universal primer except for the C, MEP60 , and MEP120 groups. A self-adhesive resin cement was bonded to all specimens, and the bond strengths were measured using a universal testing machine. All surface treatments increased both Ra and SBS values compared to the control in each material. Neither the duration of surface treatments nor the HF acid concentrations had a statistically significant effect on SBS. Within the limitations of this experimental study, it can be concluded that Monobond Etch & Prime may be a preferable method to achieve high bond strength values.

Journal of the American Ceramic Society (2020). doi:10.1111/jace.17556, Published by American Ceramic Society, Westerville, Ohio

Background: There are different etching gels available, which have different composition, different pH, and different viscosity, and there is little information in the literature comparing all these products. Objective: To evaluate the mean microshear bond strength and morphological characteristics of tooth enamel by evaluating different phosphoric acids combined with a universal adhesive system. Materials and Methods: Eighty-four enamel samples were used, which were divided according to the acid conditioning: G1: Scotchbond Etchant (3M Oral Care), G2: Ultra-Etch (Ultradent), G3: Eco-Etch (IvoclarVivadent), G4: ETCH-37 with BAC (Bisco), G5: Etching gel (Densell), G6: Condac 37 (FGM), and G7: Scotchbond Universal Adhesive (3M Oral Care) in self-etch mode. For the adhesive procedure, Scotchbond Universal Adhesive was the one used as indicated the manufacturer's instructions, 0.9-mm-diameter resin cylinders were placed. The microshear bond strength test was performed after being stored for 24 hours in water. The morphological characteristics of tooth enamel were analyzed using the Raman confocal microscope alpha300RA. The analysis of variance (ANOVA) test and Tukey post-test were used to analyze the differences between the groups. Results: The mean microshear bond strength values obtained for groups 1, 4, 5 were significantly greater than groups 2, 3, 6 and 7 (p

This chapter reviews the state‐of‐the‐art in development of the 2‐D micro‐machined whole‐angle gyroscopes. Lumped mass systems closely resemble micro‐machined gyroscopes, they are composed of one or more proof masses, shuttle assemblies, and arrays of parallel plates or comb fingers for actuation and detection. In multi‐mass systems, weak springs and lever mechanisms can be included in order to synchronize different proof masses. Axisymmetric silicon micro‐electromechanical system gyroscopes typically take the form of extruded 2‐D geometries such as rings, concentric ring systems, and disks. The most common fabrication method is Deep Reactive Etching of crystalline silicon, although polysilicon and even fused silica variants do exist. The chapter presents common 2‐D micro‐machining processes for fabrication of whole‐angle gyroscopes. Epitaxial Silicon Encapsulation process utilizes epitaxially grown silicon to seal the device layer at extremely high temperatures, which results in an ultra‐clean wafer‐level seal.

Control of cells behavior through topography of substrates is an important theme in biomedical applications. Among many materials used as substrates, polymers show advantages since they can be tailored by chemical functionalization. Fabrication of polymer substrates with nano- and microscale topography requires processing by lithography, microprinting, etching, and so forth. In this work, we introduce a different approach based on anisotropic elastic properties of polymerized smectic A (SmA) liquid crystal elastomer (LCE). When the SmA liquid crystal coating is deposited onto a substrate with planar alignment of the molecules, it develops nanogrooves at its free surface. After photopolymerization, these nanogrooves show an excellent ability to align human dermal fibroblasts over large areas. The alignment quality is good for both bare SmA LCE substrates and for substrates coated with fibronectin. The SmA LCE nano-topographies show a high potential for tissue engineering.

Low-cost Si-based anode materials with excellent electrochemical lithium storage present attractive prospects for lithium-ion batteries (LIBs). Herein, porous Si-Cu3 Si-Cu microsphere@C composites are designed and prepared by means of an etching/electroless deposition and subsequent carbon coating. The composites show a core-shell structure, with a porous Si/Cu microsphere core surrounded by the N-doped carbon shell. The Cu and Cu3 Si nanoparticles are embedded inside porous silicon microspheres, forming the porous Si/Cu microsphere core. The microstructure and lithium storage performance of porous Si-Cu3 Si-Cu microsphere@C composites can be effectively tuned by changing electroless deposition time. The Si-Cu3 Si-Cu microsphere@C composite prepared with 12 min electroless deposition delivers a reversible capacity of 627 mAh g-1 after 200 cycles at 2 A g-1 , showing an enhanced lithium storage ability. The superior lithium storage performance of the Si-Cu3 Si-Cu microsphere@C composite can be ascribed to the improved electronic conductivity, enhanced mechanical stability, and better buffering against the large volume change in the repeated lithiation/delithiation processes.

Lithium-ion batteries (LIBs) providing high energy and power densities as well as long cycle life are in high demand for various applications. Benefitting from its high theoretical specific charge capacity of ≈4200 mAh g-1 and natural abundance, Si is nowadays considered as one of the most promising anode candidates for high-energy-density LIBs. However, its huge volume change during cycling prevents its widespread commercialization. Si/C-based electrodes, fabricated through top-down mechanical-milling technique and etching, could be particularly promising since they can adequately accommodate the Si volume expansion, buffer the mechanical stress, and ameliorate the interface/surface stability. In this Review, the current progresses in the top-down synthesis of Si/C anode materials for LIBs from inexpensive Si sources via the combination of low-cost, simple, scalable, and efficient ball-milling and etching processes are summarized. Various Si precursors as well as etching routes are highlighted in this Review. This review would be a guide for fabricating high-performance Si-based anodes.

This study was focused on dual effects of 20 wt % hydrochloric acid etching treatment on cell responses and mechanical properties of a porous titanium with controllable open-porous structure. The results show that the acid etching induced the formation of a rough surface on the porous titanium, resulting in a remarkable improvement of the MG-63 osteoblasts adhesion and proliferation on the porous titanium. The surface roughness is found to be mainly dependent on the etching time. As increasing etching time, the surface roughness exhibited a noticeable rise. After etching for 90 min, the best cell response was achieved on the rough surface with a roughness value of 3.7 mm. However, the acid etching treatment displayed a negative effect on the porous titanium strength, and the yield strength was reduced down to 106 MPa as the etching time increased to 150 min. Taking both the cell responses and strength into account, an optimal etching time was determined as 60 min by experiments.

Thiol etching reaction of gold is still suffering from a lack of deep understandings on the reaction kinetics and mechanism. Herein, by using the sensor of quartz crystal microbalance (QCM) as the sacrificial probe, the etching reaction of gold has been studied in employing cysteamine (CS) as a typical thiol etchant. The etching reaction is verified as diffusion-controlled and shows a half-order reaction kinetics. It is demonstrated that intact thiol and amino on CS are both crucial for its etching ability to gold. Applied potentials can affect the electron transferring and hence can be used to regulate the etching of gold. Our results also reveal that only two carbon atoms of the spacer between thiol and amino on CS are very critical to the excellent etching ability. This work exhibits a new route to explore the thiol etching reaction of gold and well elucidates the reaction kinetics and mechanism.

The grain boundary is an intrinsic defect within mono- and multi-layer polygonal graphene islands during the chemical vapor deposition growth process. It greatly influences their mechanical and electronic properties. However, the precise characterization and formation mechanism of grain boundaries still remain unclear. In this work, H2 etching experiments show that a polygonal etched hole originates from the natural location of a grain boundary beyond the nucleation site in polygonal monolayer graphene. Furthermore, colorful Raman mapping provides a visualized method to explore the distribution of grain boundaries in polygonal bilayer graphene. Therefore, a deep understanding of the growth kinetics of mono- and bi-layer polygonal graphene was obtained through etching engineering combined with Raman spectroscopy.

We report a new series of step-etch experiments to reveal the influence of microscopy technique on track selection bias. Two different aliquots of induced tracks in Durango apatite were etched for ...

Contamination commonly observed on the graphene surface is detrimental to its excellent properties and strongly hinders its application. It is still a great challenge to produce large-area clean graphene film in a low-cost manner. Herein, we demonstrate a facile and scalable chemical vapor deposition approach to synthesize meter-sized samples of superclean graphene with an average cleanness of 99 %, relying on the weak oxidizing ability of CO to etch away the intrinsic contamination, i.e., amorphous carbon. Remarkably, the elimination of amorphous carbon enables a significant reduction of polymer residues in the transfer of graphene films and the fabrication of graphene-based devices and promises strongly enhanced electrical and optical properties of graphene. The facile synthesis of large-area superclean graphene would open the pathway for both fundamental research and industrial applications of graphene, where a clean surface is highly needed.

The purpose of this study was to determine the immediate bond effectiveness of universal adhesives to unground and ground enamel surfaces in different etching modes, through shear bond strength (SBS) tests and scanning electron microscopy observations. Three universal adhesives, a conventional two-step self-etch adhesive, and a conventional single-step self-etch adhesive were compared. Human enamel specimens from lower anterior teeth were divided into four groups and subjected to the following treatments: (i) unground enamel in self-etch mode; (ii) ground enamel in self-etch mode; (iii) unground enamel in etch-&-rinse mode; and (iv) ground enamel in etch-&-rinse mode. Bonded assemblies were subjected to SBS testing. All the adhesives showed significantly higher SBS values in etch-&-rinse mode than in self-etch mode, regardless of whether enamel was unground or ground. The influence of the enamel surface condition on SBS was different in different etching modes. Without pre-etching, all tested materials showed lower SBS values in unground enamel than in ground enamel. In etch-&-rinse mode, no significant differences in SBS values were observed between unground enamel and ground enamel for any of the adhesives tested. Phosphoric acid pre-etching before application of self-etch adhesives to an unground enamel surface is essential to enhance initial enamel bond effectiveness.

Rolling contact fatigue cracks and thermally induced defects are common problems in the railway industry especially as demands for increasing loads, speeds, and safety continue to rise. Often, the two types of defects are found together in the field, however, whether one causes the other to occur is not completely agreed upon. The effect of thermal damage, in the form of a martensite spot on pearlitic steel test bars, on the fatigue life in uniaxial low cycle fatigue experiments was investigated by the authors. However, the focus of the current work was to characterize the damage evolution from the low cycle fatigue (LCF) tests and correlate the crack initiation and propagation with the initial thermal damage. Residual stress measurements, digital image correlation, and X-ray tomography were used to characterize the effects of the thermal damage before, during, and after fatigue testing, respectively. It was found that the thermal damage causes strain accumulation and crack initiation at the interface between the two materials. The strain evolution was visualized using digital image correlation (DIC), clearly showing the strain concentrations at the top and bottom of the white etching layers (WEL), where the residual stresses are also most tensile. X-ray tomography confirmed the planar crack growth from the martensite spot.

This study reports a range of etching and annealing experiments to establish the optimum conditions for the etching of fission tracks in monazite. The previously reported concentrated (12 M) HCl etchant at 90°C was found to cause grain loss from epoxy mounts and high degrees of grain corrosion, as did much longer etching times at lower temperatures. Using implanted 252Cf semi-tracks, a series of experiments were performed on internal prismatic faces of monazite-(Ce) crystals from the Palaeozoic Harcourt Granodiorite (Victoria, Australia) using an alternative 6 M HCl etchant, also at 90°C. Step-etch results show optimal etching at 60–90 min. Further, an isothermal annealing experiment illustrated that the degree of annealing that can be expected during etching at 90°C under laboratory time scales is negligible. The etching rate between grains is not uniform, with a correlation demonstrated between over-etched grains and high U and Th concentrations.

Surface reactions constitute the foundation of various energy conversion/storage technologies, such as the lithium-sulfur (Li-S) batteries. To expedite surface reactions for high-rate battery applications demands in-depth understanding of reaction kinetics and rational catalyst design. Now an in situ extrinsic-metal etching strategy is used to activate an inert monometal nitride of hexagonal Ni3 N through iron-incorporated cubic Ni3 FeN. In situ etched Ni3 FeN regulates polysulfide-involving surface reactions at high rates. Electron microscopy was used to unveil the mechanism of in situ catalyst transformation. The Li-S batteries modified with Ni3 FeN exhibited superb rate capability, remarkable cycling stability at a high sulfur loading of 4.8 mg cm-2 , and lean-electrolyte operability. This work opens up the exploration of multimetallic alloys and compounds as kinetic regulators for high-rate Li-S batteries and also elucidates catalytic surface reactions and the role of defect chemistry.

International audience; Since SrVO3 (SVO) can be used as a highly conductive material for perovskite heterostructures, the control of surface morphology and chemistry of such thin-films are essential. Using pulsed laser deposition, two distinct topographies can be produced. Thus, by tuning oxygen pressure in the growth chamber during cooling, smooth or partially covered by self-oriented Sr3V2O8 nanorods surfaces can be grown. This study manages to correlate the two typical topographies, revealed by atomic force microscopy (AFM), with their chemical compositions obtained by X-ray photoelectron spectroscopy (XPS). At first, a model describes their initial surface chemistry through the Sr/V cationic ratio and the (Sr+V)/Oox ratio. Furthermore, using sputter-depth profiling, post-thermal treatments and wet chemical etching, SVO thin-film chemical compositions are extensively studied. We demonstrate that they are composed of stoichiometric SVO phase covered by Sr-rich layer on top. Finally, treatment in water for 180 seconds helps to remove Sr-rich phases. Sr3V2O8 nanorods are found selectively dissolved leaving a surface nano-imprint. Moreover, on smooth SVO surfaces, a balanced Sr/V cationic ratio of 1.0±0.1 is obtained. These results appear very promising for SVO thin-films surface preparation and further development as electrodes for electronic devices.

The occurrence of preferential grain etching (PGE) during alkaline etching of aluminum extrusion alloys from the 6XXX series is often linked to the presence of certain impurity elements such as zinc, causing an undesired etching appearance. In the presented work, an additional culprit in this context is identified, which has not been investigated yet. A clear relation between PGE and the presence of a subsurface shear layer is identified for extruded Al 6060 alloys containing 0.02 and 0.06 wt% Zn. This shear layer can be distinguished from the bulk of the metal by its difference in crystallographic texture as visualized by electron backscatter diffraction (EBSD). For the Zn enriched alloy, the //ND grains are etched away faster than grains with other orientations, resulting in the grainy appearance typical for PGE. Independent of the Zn content in the alloy, once the shear layer is removed and //ND grains are practically absent on the new surface, the depths variations caused by preferential etchingdisappear. Instead, the surface of the alloy is attacked uniformly by the caustic etch bath.

Chemical vapor deposition (CVD) utilizing metal cluster nanoparticle catalysts is commonly used to synthesize carbon nanotubes (CNT), with oxygen-containing species such as water or alcohol included in the feedstock for enhanced yield. However, the etching effect of these additives on the growth mechanism has rarely been investigated, despite evidence suggesting that etching potentially affects the chirality distribution of product CNTs. We used quantum chemical methods to study how water-based etchant radicals (OH and H) may enhance the chiral selectivity during CVD growth using CNT cap models. Chemical reactivities of the caps with the etchant radicals were evaluated using density functional theory (DFT). It was found that the reactivities on the cap edges correlate with the chirality of the caps. These results suggest that proper selection of etchant species can provide opportunities for selective chirality control of the product CNTs. © 2018 Wiley Periodicals, Inc.

This study aimed at determining the enamel bond durability of universal adhesives to intact enamel (IE) and ground enamel (GE) in different etching modes under thermal cycling (TC) and fatigue stresses. Two universal adhesives and a two-step self-etch adhesive were used. Enamel specimens were divided into four groups by treatment: (i) GE in etch-and-rinse, (ii) IE in etch-and-rinse, (iii) GE in self-etch, and (iv) IE in self-etch. Bonded specimens were subjected to TC, and then shear bond strengths (SBS) were conducted. SBS tests were also conducted after storage in 37°C water for 24 h (baseline). For shear fatigue strength (SFS) testing, bonded specimens were subjected to fatigue stress at a frequency of 10 Hz for 50,000 cycles. At baseline, all adhesives showed significantly higher SBS values with GE than IE in self-etch mode in contrast to in etch-and-rinse mode. After TC, the universal adhesives with IE showed lower SBS values than the baseline, regardless of the etching mode. Universal adhesives showed significantly lower SFS values with IE in etch-and-rinse, but not in self-etch mode. Phosphoric acid pre-etching or grinding of the aprismatic enamel may be helpful in establishing reliable initial and long-term bonds to enamel when using universal adhesives in self-etch mode.

Hollow spheres are charming objects in nature. In this work, an unexpected deflation–inflation asymmetric growth (DIAG) strategy is reported, generating hollow nanoparticles with tailored concave geometry for interface catalysis. Starting from aminophenol‐formaldehyde (APF) nanospheres where the interior crosslinking degree is low, fully deflated nanobowls are obtained after etching by acetone. Due to APF etching and repolymerization reactions occuring asymmetrically within a single particle, an autonomous inflation process is observed similar to a deflated basketball that inflates back to a “normal” ball, which is rare at the nanoscale. A nucleophilic addition reaction between acetone and APF is elucidated to explain the chemistry origin of the DIAG process. Interestingly, the deflated APF hollow spheres enable preferential immobilization of lipase in the concave domain, which facilitates the stabilization of Pickering emulsion droplets for enhanced enzymatic catalysis at the oil–water interface. The study provides new understandings in the designable synthesis of hollow nanoparticles and paves the way toward a wide range of applications of asymmetric architectures., Concave hollow nanospheres are tailored through an unprecedented deflation–inflation asymmetric growth strategy, with both the structural evolution and chemistry origin of this process clearly elucidated. The unique concave architecture favors localized enzyme immobilization, enabling oriented assembly at the oil–water interface of Pickering emulsion stabilization for enhanced enzymatic catalysis.

Renewable‐electricity‐driven N2 reduction is an attractive approach for ambient NH3 synthesis, but active electrocatalysts are needed to enable the N2 reduction reaction. Monolithic electrodes with active components anchored on conductive supports provide many advantages like structural stability, large surface area, and low electrical resistance. Here, a novel “oxidation‐etching” strategy is proposed to carve the surface of Cu foam into structures of particles, cubes, and sheets for N2 reduction electrocatalysis. The optimal catalyst achieves a Faradic efficiency as high as 18% at −0.35 V vs reversible hydrogen electrode (RHE) and a large NH3 yield of 2.45 × 10−10 mol s−1 cm−1 at −0.40 V vs RHE in 0.1 M HCl. Notably, it also shows superior long‐term electrochemical durability, with the preservation of electro‐activity for at least 20 hours.