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Polycarboxylate superplasticizers (PCEs) are the most commonly used admixture in the concrete industry. Their premise for work is often considered to be the adsorption of the cement particles through the anchoring groups. Here we suggest a nanoscale perspective to understand the effects of anchoring groups on the adsorption of PCEs by employing the density functional theory (DFT) method. The electronic structural analyses consider various typically anchoring groups of (COO−, PO 4 2−, PO 3 2−, Silanol, and SO 3 −). The findings indicate that anchoring adsorption predominantly occurs at apex calcium and silicon hydroxyl (Si–OH) sites on the C–S–H surface. Specifically, PCEs containing the PO 3 2− groups exhibit the highest degree of chemical adsorption at the apex cacium site, whereas those with COO− groups show the most pronounced chemical adsorption affinity at the Si–OH site. This observation suggests that varying calcium content in cementitious materials may necessitate the use of different anchoring groups for optimal PCE performance. Further analyses of the Reduced Density Gradient (RDG) indicate that PCE with the COO− and PO 3 2− groups demonstrate the most robust adsorption with the corresponding site. Furthermore, quantitative examination of the peak value at the intersection of the electron localization function (ELF) curve derived an inference that aligns with the findings from the RDG analysis. This study provides a robust framework for understanding the adsorption mechanisms of PCEs with various anchoring groups and offers valuable insights for evaluating the performance of PCEs in more complex cementitious systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A one-step method for high-yield paper-based self-synthesis of gold nanoparticles. • Nano-gold is formed without the use of any externally added reducing agent. • Opto-active and catalytic applicability of paper-supported nano-gold is illustrated. The paper (a typical nanoparticle support scaffold) is generally considered to be chemically inert and their inherent capabilities to self-generate nanoparticles have been largely overlooked. Here we present our experimental findings on the use of simple paper as a versatile green nanochemical reactor. We find that gold nanoparticles can be massively formed in paper in the absence of any externally added reducing agent or applied charge. Employing only an aqueous chloroauric solution under rather mild pH condition on paper at room temperature, this method is capable of efficiently fabricating supported nanoparticles. The flexible application of the paper-supported nanoparticles in opto-functional or catalytic frameworks is also illustrated. [ABSTRACT FROM AUTHOR]

High-burnup Zr-based nuclear fuel claddings exhibit accelerated irradiation growth, corrosion and hydrogen pick-up, all correlated with the emergence of c-component dislocation loops. We made use of sub-nm-resolution atom probe tomography to characterize the nanoscale chemistry of c-loops in fuel cladding from boiling water reactor operation. We found segregation of Fe, Ni and Sn to dislocation lines and depletion of Sn and O inside the loops, resulting in nearly pure Zr islands. We also observed nucleation of suboxide inside one c-loop, pointing to a possible mechanism of accelerated in-reactor corrosion. Such Zr-islands might also promote hydride precipitation and associated degradation. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Three Co mineralization stages in the Tuolugou deposit are identified. • Mineral chemistry and nanoscale textural study of the Co pyrite were investigated. • Co mineralization here is related to SEDEX genesis. The Tuolugou sedimentary-exhalative (SEDEX) Co-Au deposit is located in the eastern Kunlun metallogenic belt of the northern Qinghai-Tibet Plateau in China. Pyrite is the prevalent Co-hosting sulfide mineral that occurs in the Tuolugou deposit. In this study, we investigated mineral characteristics of Co-bearing pyrite and effect of Co on crystal structure of the pyrite to obtain a better understanding of Co mineralization. Three pyrite generations were identified, including Co-barren pyrite (Py-1, formed during the early mineralization stage I, with Co content of 1-3844 ppm), Co-rich pyrite (Py-2, formed during the sedimentary-exhalative stage II, Co content 15–36522 ppm), and Co-rich pyrite (Py-3, formed during metamorphic stage III, with Co contents of 448–10505 ppm in Py-3A, and 1371–14904 ppm in Py-3B). As Co enters the pyrite structure, it is discovered that the octahedrons in pyrite is twisted and tilted, the lattice parameters (a 0) rise, and the sulfur atom positions alter. The Co-rich Py-2 shows a similar REE and trace element distribution as those in quartz albitite, which indicates that Co mineralization is related to SEDEX genesis. Subsequent metamorphism resulted in additional Co enrichment. This detailed study of Co-bearing pyrite provides insights on the details of isomorphism Co in pyrite similar to the situation of this deposit as medium–low Co grade. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen embrittlement (HE) studied in wire arc additive manufactured (WAAM) Al. • Reporting for the first time, WAAM effectively suppresses HE in Al-Zn-Mg-Cu alloys. • Cu content of strengthening precipitates in peak-aged WAAM sample increases. • Many finer precipitates are distributed within grains of peak-aged WAAM sample. • Cu makes strengthening precipitate/matrix interfaces as strong H-trapping sites. In this work, atom probe tomography technique is used to investigate how wire arc additive manufacturing (WAAM) changes the nanochemistry of nanoprecipitates and grain boundaries after peak aging of a high strength Al-Zn-Mg-Cu alloy. The effect of the change in nanochemistry of nanoprecipitates on the hydrogen embrittlement of the additively manufactured aluminum alloy is investigated using a three-point bending test in humid air. The results show that the unique in-process heat treatment during WAAM, offers the possibility to modify the nanochemistry of nanoprecipitates and improve the resistance to hydrogen embrittlement of the Al-Zn-Mg-Cu alloys in the peak aged state without sacrificing mechanical performance. Density functional theory shows that the WAAM process transforms the interfaces between matrix and precipitate into a strong hydrogen trap, which can reduce the hydrogen content of grain boundaries and suppress hydrogen-induced intergranular fracture. [ABSTRACT FROM AUTHOR]

[Display omitted] Lithium iron phosphate (Li x FePO 4), a cathode material used in rechargeable Li-ion batteries, phase separates upon de/lithiation under equilibrium. The interfacial structure and chemistry within these cathode materials affects Li-ion transport, and therefore battery performance. Correlative imaging of Li x FePO 4 was performed using four-dimensional scanning transmission electron microscopy (4D-STEM), scanning transmission X-ray microscopy (STXM), and X-ray ptychography in order to analyze the local structure and chemistry of the same particle set. Over 50,000 diffraction patterns from 10 particles provided measurements of both structure and chemistry at a nanoscale spatial resolution (16.6–49.5 nm) over wide (several micron) fields-of-view with statistical robustness. Li x FePO 4 particles at varying stages of delithiation were measured to examine the evolution of structure and chemistry as a function of delithiation. In lithiated and delithiated particles, local variations were observed in the degree of lithiation even while local lattice structures remained comparatively constant, and calculation of linear coefficients of chemical expansion suggest pinning of the lattice structures in these populations. Partially delithiated particles displayed broadly core–shell-like structures, however, with highly variable behavior both locally and per individual particle that exhibited distinctive intermediate regions at the interface between phases, and pockets within the lithiated core that correspond to FePO 4 in structure and chemistry. The results provide insight into the Li x FePO 4 system, subtleties in the scope and applicability of Vegard's law (linear lattice parameter-composition behavior) under local versus global measurements, and demonstrate a powerful new combination of experimental and analytical modalities for bridging the crucial gap between local and statistical characterization. [ABSTRACT FROM AUTHOR]

With the advancement of nanochemistry, artificial nanozymes with high catalytic stability, low manufacturing and storage cost, and greater design flexibility over natural enzymes, have emerged as a next-generation nanomedicine. The catalytic activity and selectivity of nanozymes can be readily controlled and optimized by the rational chemical design of nanomaterials. This review summarizes the various chemical approaches to regulate the catalytic activity and selectivity of nanozymes for biomedical applications. We focus on the in-depth correlation between the physicochemical characteristics and catalytic activities of nanozymes from several aspects, including regulating chemical composition, controlling morphology, altering the size, surface modification and self-assembly. Furthermore, the chemically designed nanozymes for various biomedical applications such as biosensing, infectious disease therapy, cancer therapy, neurodegenerative disease therapy and injury therapy, are briefly summarized. Finally, the current challenges and future perspectives of nanozymes are discussed from a chemistry point of view. As a kind of nanomaterials that performs enzyme-like properties, nanozymes perform high catalytic stability, low manufacturing and storage cost, attracting the attention of researchers from various fields. Notably, chemically designed nanozymes with robust catalytic activity, tunable specificity and multi-functionalities are promising for biomedical applications. It's crucial to define the correlation between the physicochemical characteristics and catalytic activities of nanozymes. To help readers understand this rapidly expanding field, in this review, we summarize various chemical approaches that regulate the catalytic activity and selectivity of nanozymes together with the discussion of related mechanisms, followed by the introduction of diverse biomedical applications using these chemically well-designed nanozymes. Hopefully our review will bridge the chemical design and biomedical applications of nanozymes, supporting the extensive research on high-performance nanozymes. [Display omitted] [ABSTRACT FROM AUTHOR]

Guinier-Preston (GP) zones, which form in Al–Cu alloys, exhibit characteristic patterns of Cu-rich, disk-shaped atomic clusters along the {100} planes. GP zones have received much attention not only for their precipitation-hardening effect on the Al matrix, but also from fundamental interest in the physics and chemistry of the nanoscale organization of solute atoms. In this study, we established an atomistic kinetic Monte Carlo (kMC) modeling technique for exploring the nucleation and formation processes of GP zones in Al–Cu alloys by constructing an effective on-lattice multibody potential for a dilute Al–Cu-vacancy system by density functional theory calculations. Our model can describe the clustering of Cu atoms via successive exchanges with vacancies and reproduce the characteristic planar nanoprecipitates along the {100} planes in a manner consistent with the crystallographic nature of the GP zones in the early-stage aging of Al–Cu alloys. The time evolution and critical nucleus size of Cu clusters were characterized at various temperatures based on the kMC results. Consequently, we predicted the existence of an optimum temperature (i.e., nose temperature) for the formation of Cu clusters at which the cluster growth was maximized, which was attributable to the interplay between the critical nucleation barrier and the diffusion rate. In addition, the critical nucleus size and temperature for cluster formation were examined based on classical nucleation theory along with the developed multibody potential. These provided an insight into the competition between the enthalpic and entropic effects on the formation of GP zones in the Al–Cu system. Image 1 [ABSTRACT FROM AUTHOR]

The present study investigated the solid products of heterogeneous catalytic oxidation of aqueous Mn(II) by O 2 in the presence of hematite nanoparticles (NPs) using transmission electron microscopy (TEM), scanning TEM (STEM), and electron energy-loss spectroscopy (EELS). The oxidation experiments were conducted at room temperature (22 ± 2 °C) in solutions containing 10−3 M Mn(II) at pH 7.5 in the dark. During 48 h of reaction, a single-phase manganite (a Mn oxyhydroxide) nanowire was formed by way of metastable groutite and feitknechtite nanowires, both of which are polymorphs of manganite. Between 48 and 168 h, the manganite further altered to core-shell structured nanowires with hausmannite (a mixed valent Mn oxide) forming a very thin (2 nm) outer-shell on the manganite wire core. The formation of Mn-oxyhydroxide nanowires was catalyzed by the hematite NPs surface through electrochemical pathways. This is described via the electron transfer across a redox couple from adsorbed Mn(II) to another site with adsorbed O 2 via the band structure of the semiconducting hematite. On the other hand, the Ostwald step rule was operative in the sequential crystallization from metastable groutite and feitknechtite to stable manganite, which could have resulted from the differences in the surface free energies, sizes, and morphologies of product polymorphs at the nanoscale. The final product (at least in the time range of our experiments) exhibited manganite/hausmannite core-shell structures. This product is most likely to be formed by the reactions catalyzed by the manganite nanowires themselves. Microscopic investigation of interfacial changes in structure and chemistry at the nanoscale is key, and it can be essential to understand the kinetic and thermodynamic phenomena related to the redox chemistry and phase stability of nanoparticles in complex, heterogeneous systems such as natural environments. [ABSTRACT FROM AUTHOR]

Environmental control on graphene is becoming increasingly necessary to study fundamental processes and to achieve graphene-based technological developments. Here, we designed dynamic actuation on split graphene fluid-environments by supporting graphene sheets on mesoporous thin films (air up - nanopore-confined fluid down). This approach allows transporting species and performing nanochemistry at specific sites under the graphene membrane. We also show distinctive behavior affecting graphene permeability linked to the driving force of the involved water-nanopore interplay processes. This novel precise control of graphene environment offers possibilities for further graphene-based technological developments, such as sensor and actuator tools highly required in lab-on-a-chip devices, as well as to perform fundamental yet elusive studies on water interactions in integrated nanomaterials. Image 1 • Disparate environments in graphene supported on nanoporous film were created. • Dynamic actuation on split graphene environments was designed. • Distinctive graphene-water-nanopore interplay processes were observed. • Sectorial chemistry confined under the graphene membrane was achieved. [ABSTRACT FROM AUTHOR]

Abstract Understanding the sintering kinetics of plasma-sprayed thermal barrier coatings (PS-TBCs) is crucial to retard their performance degradation. However, under real service condition, the sintering kinetics is often affected by multiple factors. This study investigated the sintering kinetics, in a novel scale-progressive view, under the combined-effect of internal and external factors. Results show that the sintering kinetics of PS-TBCs was highly associated with their unique sintering process from nanoscale to microscale. Firstly, sintering leads to nanoscopic roughening of the pore surface. Subsequently, multiple contacts are formed between counter-surfaces. As a result, microscopic healing of pores can be finally observed. In terms of external factors, the temperature further affects the level and rate of nanoscopic roughening. This is responsible for the differences of the microscopic healing ratios, as well as the macroscopic elastic modulus. [ABSTRACT FROM AUTHOR]

Highlights • The growth mode of InAs on GaAs depending on substrate orientation is successfully clarified using nano- and macro-theories. • The misfit dislocation formation energy is closely related to the dependence of the growth mode on orientation. • The growth mode boundary is simply determined by surface energy and degree of strain relaxation. • Growth mode transition appears in InAs/GaAs (1 1 0) due to strain relaxation at the interface. Abstract Growth mode in semiconductor heteroepitaxial system such as InAs/GaAs is systematically investigated from nano- and macro-theoretical viewpoints, where ab initio, empirical interatomic potential, and phenomenological macroscopic theory are used. The nanoscopic theories clarify that the misfit dislocation (MD) formation energy depends on orientation such as 1.14 eV/Å for (0 0 1), 0.96 eV/Å for (1 1 0), and 0.68 eV/Å for (1 1 1)A. On the basis of these calculated results, growth mode boundary between two-dimensional with MD formation (2D-MD) and three-dimensional Stranski-Krastanov island (3D-SK) growth modes is successfully determined as functions of surface energy and degree of strain relaxation. The region of 3D-SK growth mode is the largest for (0 0 1) while (1 1 1)A has the largest 2D-MD region and that for (1 1 0) is in between. Using surface energy obtained by ab initio calculations and the degree of strain relaxation estimated by continuum elasticity theory, it is found that (0 0 1) favors 3D-SK growth mode while 2D-MD growth mode appears for (1 1 0) and (1 1 1)A. It should be noted that the (1 1 0) data stay near the growth mode boundary between 3D-SK and 2D-MD growth modes. Reflecting this, growth mode transition from 2D-MD to 3D-SK occurs for (1 1 0) due to In 0.25 Ga 0.75 As layer insertion at the interface that decreases surface energy from 50.9 meV/Å2 to 49.1 meV/Å2. Versatility of this approach is discussed by comparing with experimental findings. [ABSTRACT FROM AUTHOR]

Abstract The reduced-order modeling and performance of single-layered functionally graded piezoelectric energy harvesting systems are investigated. The choice of single-layered functionally graded materials gives the opportunity to minimize the volume of the energy harvesting system and hence increases its power density. Also, the unique composition of a functionally graded material allows for the creation of durable piezoelectric energy harvesters. As for the modeling of functionally graded piezoelectric materials, there has been some debate due to the location of the neutral axis compared to the central axis of the system. To this end, the use of the geometric central axis as the neutral axis to approximate the behavior of single-layered functionally graded cantilever piezoelectric energy harvesters and the possibility of getting erroneous predictions are explored. The effects of the material distribution and the scaling of the energy harvesting system form macro- to nano-scale are also considered. It is proved that the use of the central axis model can lead to significant inaccuracies in the estimation of the natural frequencies of the energy harvester for certain material distributions. Additionally, the central axis approximation exhibits a reduced coupling between the electrical circuit and the beam structure which could result in inefficient design of the energy harvester. It is also shown that the percentage of the metallic material can significantly affect both the natural frequencies and the power density of the system. The obtained results show the importance of considering the neutral axis modeling for efficient and optimal design of functionally graded piezoelectric energy harvesters. [ABSTRACT FROM AUTHOR]

Abstract The material investigated is highly concentrated water-in-oil emulsion (w/o) with a dispersed phase concentration of approximately 90 wt%. Instability of such emulsions arises mostly from coalescence of the dispersed droplets in the system during ageing. Here, we report a new approach to stabilize this highly concentrated w/o emulsion by using Polyhedral Oligomeric Silsesquioxane (POSS) nanomolecules. POSS AM0275 nanomolecules were dissolved into the oil phase prior to both interfacial properties measurements and emulsification. A series of three industrial grade (Mosspar-H, Ash-H, Parprol) and one laboratory grade (Dodecane) oils were used. The interfacial tension, the interfacial elasticity and stability against coalescence of the resulting emulsions were investigated for varying oil type. The results showed that POSS AM0275 nanomolecules are surface actives. Interestingly the investigation clearly demonstrated that this nanomolecule can generate an interfacial layer with completely new properties that are not available neither with conventional surfactants nor nanoparticles. First, unlike nanoparticles, POSS nanomolecules significantly reduce the interfacial tension at the same extent as do surfactants. Second, both the interfacial tension and the interfacial elasticity measurements demonstrated that unlike surfactants, POSS AM0275 nanomolecule induces gelation of the interface resulting in the formation of a rigid and flexible gel-like bag which encapsulates the aqueous phase at such extent that one can suck out all the aqueous phase leaving an empty gel-like bag. Third, unlike nanoparticles, POSS AM0275 nanomolecules have a high capacity to form highly concentrated emulsions. The resulting emulsions demonstrated outstanding stability against coalescence though this was found to be sensitive to the type of oil used. Highlights • Poss nanomolecules generate an inelastic gel-like interfacial layer • The interfacial layer encapsulate an emulsion drop • Encapsulated drops possess outstanding stability against coalescence [ABSTRACT FROM AUTHOR]

Abstract The central nervous system (CNS) in neurodegenerative diseases is a battlefield in which microglia fight a highly atypical battle. During the inflammatory process microglia themselves become dysfunctional and even with all the available immune arsenal including cytokine or/and antibody production, the battle is eventually lost. A closer look into the picture will reveal the fact that this is mainly due to the atypical characteristics of the infectious agent. The supramolecular assemblies of misfolded proteins carry unique features not encountered in any of the common pathogens. Through misfolding, proteins undergo conformational changes which make them become immunogenic, neurotoxic and highly infective. The immunogenicity appears to be triggered by the exposure of previously hidden hydrophobic portions in proteins which act as damage-associated molecular patters (DAMPs) for the immune system. The neurotoxicity and infectivity are promoted by the small oligomeric forms of misfolded proteins/peptides. Oligomers adopt conformations such as tubular-like, beta-barrel-like, etc., that penetrate cell membranes through their hydrophobic surfaces, thus destabilizing ionic homeostasis. At the same time, oligomers act as a seed for protein misfolding through a prion/prion-like mechanism. Here, we propose the hypothesis that oligomers have catalytic surfaces and exercise their capacity to infect native proteins through specific characteristics such as hydrophobic, electrostatic and π-π stacking interactions as well as the specific surface area (SSA), surface curvature and surface chemistry of their nanoscale supramolecular assemblies. All these are the key elements for prion/prion-like mechanism of self-replication and disease spreading within the CNS. Thus, understanding the mechanism of prion's templating activity may help us in the prevention and development of novel therapeutic strategies for neurodegenerative diseases. Highlights • The atypical nature of infectious agent as main culprit behind the unorthodox inflammation in neurodegenerative diseases. • The presence of autoantibodies and the molecular mimicry point to an autoimmune component in neurodegenerative diseases. • The revealed hydrophobicity in proteins triggers inflammation, aggregation and perturbs the dynamic of water in the brain. • Oligomers and protofibrils in disease may have catalytic surfaces promoting protein destabilization onto their surfaces. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • An enhanced petrorefining scenario with a novel catalyst for steam catalytic cracking. • A composite nanocatalyst (CNM) afforded the improved upgrading of fuel oil. • Enhanced propylene production compared to commercial FCC and ZSM-5 catalysts. • Olefin content of >80 wt% in the gases with the P/E severity factor of 2.18. • The total distillate (gasoline and diesel fuel) amounted to 46 wt%. Abstract A novel composite nanocatalyst (CNM) was fabricated and identified using XRD, NH 3 -TPD, FTIR, SEM, EDX, and N 2 physisorption, and was further assessed for the catalytic cracking of a heavy feedstock to value-added chemicals, including light alkenes and liquid fuels. Multiple phases (MEL, MFI, CHA, and AlPO) and a moderately tuned acidity different from those in FCC and ZSM-5 catalysts were identified for the investigated catalyst. More than 80 wt% of the dry gas stream was occupied by light olefins (ethylene, propylene, and butenes) with the remarkable propylene-to-ethylene ratio of 2.18, surpassing the two benchmark ZSM-5 and FCC samples. Meanwhile, the total yield of gasoline and diesel fuel amounted to ˜46 wt%. The influence of operating conditions including reaction temperature and contact time on the catalytic performance of CNM was further investigated. The results indicated that a temperature of 823 K was most promising for obtaining notable yields of light olefins, particularly propylene, while at lower temperatures (723 K), the yield of liquid products became almost three times the gaseous species. The observed activation energy was about 36.7 kJ/mol with the CNM catalyst. Interestingly, by increasing the space velocity by a factor of five, the productivity to light olefins increased by 11.4% on a feed basis, indicating the high potential of the new catalyst for the catalytic conversion of heavy hydrocarbons to light olefins. An eight-lump kinetic model with varying orders of reaction successfully described the obtained results. The overall reaction order for the conversion of fuel oil on CNM was 1.47, whereas a negative reaction order for coke formation was observed in reasonable agreement with the phase separation theory. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Body-centered-orthorhombic martensite (bco) is stable under compressive stress. • Supersaturated ferrite exhibits a superelastic behavior near the critical point. • Martensite softens under compression and tension, and presents a Bauschinger-like effect. • Mechanical instability and variant texturing will occur in martensitic microstructures. Abstract We studied the elastic response of body-centered iron-carbon crystals. By coupling a mean-field elastochemical model with a kinetic Monte Carlo algorithm, we computed stress – composition and stress – temperature state diagrams and simulated uniaxial tensile-compressive tests on oriented variants. We found that, in addition to the well-known ferrite and bct-martensite phases, the phase diagram comprises the body-centered-orthorhombic martensite (bco), which is stable under compressive stress. The elastic response of supersaturated ferrite appears highly non-linear and exhibits a superelastic behavior near the critical point of the phase diagram. When submitted to a strain cycle, martensite softens under both compression and tension, in association with a lattice-scale Bauschinger effect. Our results suggest the occurrence of mechanical instability and resulting variant texturing in polycrystalline martensitic structures. [ABSTRACT FROM AUTHOR]

Abstract We review the origins of capacitive phenomena at the nanoscale to demonstrate that electrochemistry cannot be understood without a critical re-reading of nanoscale electronics, and vice-versa. The fundamentals are stated at a mesoscopic physical level at which both classical and quantum mechanical terms are important to the explanation of different capacitive contributions. At this mesoscopic physical scale, a quantum mechanical Hamiltonian can be analytically solved for a metal-electrolyte interface modified with an ensemble of molecular-scale building blocks. This mesoscopic electrochemical state arises in most situations involving nanostructured electrochemical junctions, while the outcome of resolving the Hamiltonian associated with this mesoscopic problem is electrochemical capacitance. Therefore, in the present study, we departed from the conventional meaning of electrochemical capacitance to demonstrate that non-faradaic and faradaic charging events are identical phenomena. Using specific examples in which these approximations apply, we elucidate and generalize the common molecular origin of double-layer and pseudo-capacitive charging phenomena. This important fundamental knowledge obviously impacts the development of nanostructured super-capacitors, researchable batteries, etc. Additionally, we discuss the principle of operation of non-faradaic and faradaic capacitive sensing devices, which are notable for conforming to equivalent principles. In summary, super-capacitance phenomena are introduced and elucidated from first-principles quantum mechanics outcomes. [ABSTRACT FROM AUTHOR]

Highlights • Structure of CHT Type I and II characterized at the nanoscale. • Adsorption of antibody monomer-dimer mixtures controlled by CEX mechanism. • Antibody monomer and dimer adsorption kinetics is mass transfer controlled. • Mass transfer model predicts two-component binding kinetics. Abstract The internal structure of ceramic hydroxyapatite CHT Type I and Type II and the adsorption behavior of a monoclonal antibody in monomeric and dimeric forms are determined. Both CHT types contain elongated nanocrystals with size about 20 x 100 nm for Type I and about 50 x 200 nm for Type II. Internal porosities and apparent pore radii based on inverse size exclusion chromatography are 0.73 and 30 nm for Type I and 0.70 and 49 nm for Type II. Adsorption isotherms show maximum capacities of 95 and 110 mg/mL of particle for monomer and dimer on Type I and of 55 and 67 mg/mL of particle on Type II, in approximate agreement with the ratio of surface areas. The isotherms are dependent on the Na+ concentration consistent with an electrostatically driven mechanism. Mixture adsorption shows selectivity toward the dimer, with mean α-values of 4.3 and 5.8 for Type I and II, respectively. Effective pore diffusivities for non-binding conditions are 0.54 × 10−7 and 0.33 × 10−7 cm2/s for monomer and dimer in CHT Type I increasing to 0.94 × 10−7 and 0.66 × 10−7 cm2/s as a result of the larger pore size of Type II. Effective pore diffusivities for strong binding conditions, obtained by confocal microscopy, are much smaller than the non-binding values for Type I but essentially the same for Type II, indicating that diffusional hindrance by the bound protein is greater in the smaller pores of Type I. Mixture confocal adsorption experiments show that the competitive binding kinetics is largely controlled by pore diffusion in both CHT types with the dimer readily displacing the monomer even for strong binging conditions, but is much faster on Type II. [ABSTRACT FROM AUTHOR]

Abstract One of the most important effects of water on earth is that surfaces in air adsorb small amounts of water, usually in the form of a thin film. Real surfaces, especially the rather soft biomolecular surfaces, are covered by highly curved micro- and nanostructures, which induce more complex wetting geometries, such as films, droplets, and filaments. This effect, though ubiquitous, has not yet been investigated on the nanoscale. We have approached the situation by combining a soft proteinous surface, made up from very resilient tubular plant viruses, with ionic liquids. Their low vapor pressure allowed us to observe nanoscale wetting patterns at very high spatial resolution with AFM (atomic force microscopy), SEM (scanning electron microscopy) and STEM (scanning transmission electron microscopy). We found droplets, filaments and layers, with meniscus diameters down to below 10 nm. All geometries are comparable with results obtained on the microscale, and with standard macroscale wetting models. Highlights • Soft biomolecular surfaces, covered by highly curved micro- and nanostructures • Complex wetting geometries, not yet been investigated on the nanoscale • Combination of nanotubular of Tobacco Mosaic Virus with ionic liquids • Nanoscale wetting patterns observed by AFM and electron microscopy [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The photodegradation of PET fibers under accelerated aging conditions is investigated at the nanoscale. • An understanding complementary for the photodegradation mechanism at the surface of PET fibers is proposed. • The 3D chemical images at submicrometer of functional groups of aged PET fibers are, for the first time, provided. • The change in molecular trans-gauche conformation during the PET photodegradation has been proven. Abstract This work aims to mainly use a recent resonance-enhanced atomic force microscopy coupled with infrared spectroscopy (AFM-IR) to follow the accelerated degradation process of a polyester (PET) membrane at the surface. By analyzing at the nanoscale of the chemical composition and the distribution of functional groups appearing on the aged sample surface, an understanding complementary on the mechanism of degradation under artificial weathering conditions is proposed, in which hydrolysis and photo-oxidation processes via perester and aromatic acid species are mainly observed. At the molecular level, our finding show a transfer from the trans conformer to the gauche conformer during the aging process, as shown by the increase of the characteristic IR bands of the gauche conformer at 1096 cm−1 and the decrease of the IR bands of the trans conformer at 1340 cm−1. It also appears that oxidation and chain scission reactions are mainly responsible of a reduction in degree of crystallinity, tensile properties and molecular weight of polyester membrane. The effect of thermal and physical degradation is negligible in this condition. [ABSTRACT FROM AUTHOR]

Abstract Nanoscale precipitation and its influence on the strengthening mechanisms in low-carbon ultra-high-strength steel, hot-rolled at different temperatures and subjected to various isothermal aging conditions, are studied. The steel has a yield strength of ∼1730 MPa and elongation-to-failure of ∼13% under the peak aging condition, of which ∼740 MPa is contributed by precipitation strengthening. The precipitation strengthening mechanisms, including both the shearing mechanism and the Orowan mechanism, are quantitatively analyzed based on the mechanical properties and precipitate properties determined by small-angle neutron scattering, and atom probe tomography (APT). The APT results show that the average Guinier radius of the nanoscale precipitates under the peak aging condition is 1.4 nm at a number density of 6.19 × 1023 m − 3 . These nanoscale precipitates consist of a Cu-enriched core, in which the depletion of Fe and enrichment of Cu change monotonically towards the center of the precipitates, whereas the concentrations of Ni, Al, and Mn exhibit diffused enrichment near the precipitate-matrix interfaces. Until the peak aging, precipitation strengthening mainly arises from shearing mechanism, among which the order and modulus strengthening mechanisms play the most significant role. Beyond peak aging, the shearing mechanism is not valid and the Orowan mechanism is the dominant contributor to the increase in yield strength due to the coarsening of the precipitates. The effect of the matrix microstructure on strength is also addressed and discussed. Graphical abstract Image 1 Highlights • 740 MPa increment in yield strength is obtained through precipitation strengthening. • The precipitates consist of Cu-enriched core encased by Ni(Al,Mn) phase. • Precipitation strengthening is contributed by shear mechanism under and at the peak aging. • Orowan mechanism dominates the increase in yield strength beyond peak aging. [ABSTRACT FROM AUTHOR]

Abstract The possibility and the mechanisms of liquid transport in nanotubes by the effect of thermal transpiration phenomenon are discussed using molecular dynamics simulation (MD) method. Based on the results, it is demonstrated that the thermal transpiration flow for liquids can be established by imposing a temperature gradient to the wall of a nanoscale tube. It can be deduced from MD results that this flow is mainly due to the asymmetric pressure distribution in a narrow region near the tube wall. Fluid layering phenomenon near the wall together with the induced temperature gradient causes the potential component of the pressure in the narrow region near the cold side of the tube becomes higher than the hot side. This causes the fluid to flow in the direction of the temperature gradient. It is shown that the thermal transpiration flow is a plug-like flow. This phenomenon can be used in designing thermal pumps for fluids. The effect of several effective parameters in fluid pumping is investigated. Results show that increasing the imposed temperature gradient, decreasing the nanotube diameter and increasing the fluid-wall binding energy augments the thermal transpiration effect. [ABSTRACT FROM AUTHOR]

Abstract In this study, the influence mechanism of the coupling effect on the material removal process of SiC in nanoscale condition is investigated using the molecular dynamics method. The geometrical characteristics of a machined surface and the damage distribution under a coupling effect are analyzed. The influence law of the coupling effect on surface/subsurface features is also presented. According to the analysis results, the repeated and interference scratches with multi-abrasives, large-area machined surface morphology, and damage distribution are analyzed. This study is significant in understanding the removal mechanism of SiC during the grinding process at the nanoscale. [ABSTRACT FROM AUTHOR]

Abstract High thermal conductivity metal materials such as metal foams, metal particles and even metal fins can effectively improve the thermal conduction of alkanes as phase change energy storage materials. For investigating the microscopic behaviors of alkanes interacted with nanoscale copper surface, the molecular system composed of copper surface and amorphous n-octadecane (denoted by system A) was initially constructed. Simultaneously, the single wall carbon nanotubes were added into the previous system (denoted by system B) to understand their effect on the alkane. By performing molecular dynamics simulations, the potential energy components, diffusion coefficient, structural evolution, spatial orientation correlation function, relative concentration and thermal conductivity were calculated, respectively. The results showed that the crystallization of alkane induced by copper contributing to the enhancement of thermal conductivity of alkane/copper compound phase change materials. And the additive of carbon nanotubes can significantly promote the ordered alignment of alkane molecules. The results also showed that the phase transition temperature of n-octadecane in system B was more than that in system A by about 10 K owing to the further crystallization of n-octadecane induced by single wall carbon nanotubes as illustrated from the diffusion coefficient trends and potential energy component analysis. Highlights • Cu/C 18 H 38 & Cu/C 18 H 38 /SWCNT systems were built and MD simulations were performed. • Thermal diffusion and phase transition of C 18 H 38 were investigated in detail. • Thermal conductivities of C 18 H 38 based on different states were calculated. [ABSTRACT FROM AUTHOR]

Highlights: • A bio-inspired textured surface enables fully texture-driven fog harvesting. • The textures simultaneously maximize fog condensation and droplet disposal. • Consequently, the surface exhibits nearly six-fold increase in fog harvesting efficiency. • The texture is fabricated by a single-step nanoimprinting on large-area substrates. Abstract Fog harvesting is recognized as one of the most sustainable means of freshwater collection. Synthetic fog harvesting surfaces have been predominantly inspired from the desert beetle's exoskeleton which exhibits a bumpy topography. This topography underlies an alternating hydrophilic-hydrophobic pattern which has been the basis of several bio-inspired fog harvesting surfaces. However, replication of such hydrophilic-hydrophobic patterns involves multiple processing steps and tedious incorporation of functional/chemical groups at precise locations. On the other hand, surface topography or texture has proven to be insufficient in realizing an efficient fog harvesting surface. This is because micro- or nano-scale textures alone fail to simultaneously maximize the rate of droplet condensation and disposal, which are the two key aspects of efficient fog harvesting. Herein, we report that a hierarchically-textured surface, consisting of micro-lenses arrays covered with high aspect-ratio nanoscale fibrils, can fulfil these two key requirements for maximizing fog harvesting efficiency. While the micro-lenses enable faster droplet condensation, the cluster of nanoscale fibrils impart superhydrophobicity that aids in intermittent droplet disposal. Together, the topography achieves a fog collection efficiency ∼5–6 times higher than that of the planar counterpart. Moreover, this hierarchical texture is fabricated by a simple one-step nanoimprinting approach which is scalable to arbitrarily large-area flexible substrates. [ABSTRACT FROM AUTHOR]

Abstract Using the Monte Carlo simulation, the magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2, 2) ternary metal nanoisland with core–shell structure in external magnetic field have been researched detailedly. The effects of crystal-field, exchange coupling and temperature on magnetization, susceptibility, blocking temperature and internal energy as well as hysteresis loops behavior of the system have been exhibited. Some interesting phenomena such as multiple saturation magnetizations and rich hysteresis loops behaviors have been found. The results can be comparable with some theoretical and experimental researches. Highlights • The mixed-spin (1 , 3 ∕ 2 , 2) ternary metal nanoisland in the longitudinal magnetic field has been studied. • Magnetization, susceptibility, internal energy and blocking temperature have been discussed. • The triple and double hysteresis loops behaviors have been found in the nanoisland for certain physical parameters. [ABSTRACT FROM AUTHOR]

Abstract Hydroxyapatite (HA), Ca 10 (PO 4) 6 (OH) 2 , is a key material used to manufacture thin, bioactive coatings on metal implants for hard tissue regeneration. Technical challenges in their fabrication include control of the coating structure and chemical composition, as well as managing surface activation via ionic substitution. In this study, 15 – 216 nm-thick zinc-doped HA (ZnHA) thin films were grown via magnetron sputtering at room temperature. The effect of substituting Zn2+ for Ca2+ on the ultrastructures of the HA films was analyzed during several stages of film growth. Infrared vibrational scattering scanning near-field optical microscopy (s-SNOM) using the ultra-broad-band IR beam from synchrotron radiation was compared with Fourier transform infrared spectroscopy in attenuated total reflectance (FTIR/ATR) to reveal the close relationships between local topography and the chemical compositions of the film surface and the bulk of the film. The energy delivered via ionic bombardment induced the formation of complex structures: island-shaped nanoparticles of amorphous zinc-doped calcium phosphate, coalescent islands, disordered non-stoichiometric ZnHA nanoparticles, and long-range structures of nearly stoichiometric and crystalline ZnHA. Grazing incidence X-ray diffraction (GIXRD) from synchrotron radiation, X-ray photoelectron spectroscopy (XPS), focusing ion beam (FIB), and high-resolution transmission electron microscopy (HRTEM) confirmed Zn substitution into the HA lattice. Zinc was distributed homogeneously within the film structure (1.6 at%) but its concentration increased slightly on the film surface. The bulk of the film consisted of crystalline, columnar ZnHA domains oriented perpendicular to the substrate surface while the regions near the film/substrate interface were preferentially disordered and non-stoichiometric. [ABSTRACT FROM AUTHOR]

Abstract Novel nanoscale drug delivery biomaterials are of great importance for the diagnosis and treatment of different cancers. We have developed a new pegylated squalene (SQ-PEG) derivative with self-assembly properties. Supramolecular assembly with a lipophilic photosensitizer pyropheophorbide-a (Ppa) by nanoprecipitation gave nanoconstructs SQ-PEG:Ppa with an average size of 200 nm in diameter and a drug loading of 18% (w/w). The composite material demonstrates nanoscale optical properties by tight packing of Ppa within Sq-PEG:Ppa resulting in 99.99% fluorescence self-quenching. The biocompatibility of the nanomaterial and cell phototoxicity under light irradiation were investigated on PC3 prostate tumor cells in vitro. SQ-PEG:Ppa showed excellent phototoxic effect at low light dose of 5.0 J/cm2 as a consequence of efficient cell internalization of Ppa by the nanodelivery system. The diagnostic potential of SQ-PEG:Ppa nanoconstructs to deliver Ppa to tumors in vivo was demonstrated in chick embryo model implanted with U87MG glioblastoma micro tumors. Graphical Abstract Pegylated squalene (SQ-PEG) derivative and a lipophilic photosensitizer pyropheophorbide-a (Ppa) form supramolecular structures by self-assembly. SQ-PEG:Ppa nanoconstructs with average size of 200 nm in diameter and a drug loading of 18% (w/w). Nanoscale optical properties of Sq-PEG:Ppa result in 99.99% fluorescence self-quenching. SQ-PEG:Ppa composites promote cell internalization of Ppa which leads to excellent phototoxic effect at low light doses. SQ-PEG:Ppa efficiently deliver Ppa to U87MG glioblastoma micro tumors implanted in chick embryos in vivo demonstrating their diagnostic potential for cancer fluorescence detection. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract In the present investigation, a novel strategy of continuous microwave assisted flow synthesis (CMFS) has been adopted in comparison to traditional synthesis procedures (sol-gel and chemical precipitation method) for the quick production of TiO 2 nanoparticles with very fine particle properties. The X-ray powder diffraction analysis (XRPD) and transmission electron microscopy (TEM) were two techniques used for analysing the properties related to structure and particle morphology of the resultant samples. It was observed that the particles formed by using continuous flow route were less agglomerated, and particle size (~ 6 nm) was smaller in comparison with others obtained using sol-gel (~ 9 nm) and chemical precipitation method (~ 15 nm). X-ray diffraction impressions established the generation of Anatase phase with preferential [101] dimension. Zeta potential computations were taken to inspect the colloidal stability of nanoparticles. Antimicrobial nature of TiO 2 nano-samples was analyzed by using various bacterial and fungal strains. The nanostructured TiO 2 particles confirmed outstanding uniformity with respect to chemical and structure. This new ceramic substance with strong antimicrobial activity promised magnificent potential in bone tissue engineering. [ABSTRACT FROM AUTHOR]

Abstract Advanced ceramics after sintering are almost processed by grinding or non-traditional machining. Nevertheless, these methods are limited by complexity of processing efficiency, tool wear and economic effectiveness. So machining green ceramics before sintering is introduced, it is environmentally friendly, efficient and cheap with high removal rate of materials. During dry turning green ceramics, flank-wear of tools and processing quality of compacts are two main elements to evaluate cutting performance of tools. The processing efficiency and economic effectiveness are mainly effected by the cutting performance of tools. In this paper, polished tool, tool with nano-scale textured flank-face, tool with TiAlN coating deposited on polished flank-face, and tool with TiAlN coating deposited on nano-scale textured flank-face were prepared. Effect of nano-scale texture pretreatment on wear-resistance of WC/Co tools with/without TiAlN coated flank-face was studied in turning of green Al 2 O 3 ceramics. Results displayed that nano-scale textures on the flank-face had prominent effects on the enhancement of flank-wear resistance of tools. Relevant mechanisms were explored that nano-scale textures exhibited "derivative cutting" to protect unworn face from abrasion, and nano-scale textures pretreated on the flank-face could enhance the adhesion strength between coating and matrix. These developed tools could also significantly improve the processing quality of machined surfaces. [ABSTRACT FROM AUTHOR]

Abstract The atomic nature of topologically protected ferroelectric (FE) walls in hexagonal ReMnO 3 oxides (R: Sc, Y, Er, Ho, Yb, Lu) creates an interesting playground to study effects of defects on domain walls. The 6-fold FE vortices in this multiferroic family lose the ordering by the rule of 6 in the presence of partial edge dislocations (PED) besides it can be modified by chemical doping. Therefore, it is essential to comprehend the cross coupling of FE walls and defects or vacancies in the lattice of multiferroics. Atomic resolution STEM is used to explore the correlative response of electrical polarization of FE domains in the presence of defects in multiferroic ceramics. Such level of resolution also allows the study of switching of FE domains on encounter of lattice defects. The driving force behind appearance of dispersed, small FE domains in images of piezo force microscopy is revealed by observation of lattice defects and FE boundaries simultaneously at the nano-scale. Planar defects and FE domain walls play their role of internal interfaces consequently such interplaying duly modifies the magnetic and FE properties of multiferroic oxides. Highlights • Aberration corrected STEM is used to link ferroelectric properties of vacancy doped multiferroic LuMnO3 ceramics to lattice defects. • Nano-scale perturbation in lattice or chemistry provokes polarization switching or phase shift of ferroelectric domains. • Partial edge dislocations modify rule of 6 in topologically protected 6-fold vortices in hexagonal RMnO3 ceramics. • Chemistry shift/lattice distortions modify ferroelectric properties, domain size and polarization switching in multiferroic. • Change in ferroelectric properties results in modification of magnetic properties in magnetoelectric h-RMnO3 multiferroic. [ABSTRACT FROM AUTHOR]

Nanoscale phosphors of Yb 3+ /Er 3+ /Tm 3+ -doped GdPO 4 with different morphologies were synthesized using the solvothermal method with annealing at 750 °C and 1000 °C. A high concentration of Yb 3+ (35%mol) ions was successfully doped in the powders. Crystal structures were characterized through powder XRD measurement and Fourier transform infrared spectroscopy. SEM images have shown that the morphologies of the samples can be controlled by adjusting the pH value during their synthesis. Upconversion luminescence was investigated under 980 nm diode laser excitation. The upconversion processes were assessed on the basis of the power dependence of upconversion emission intensity. The light colour was investigated with respect to the 1931 CIE diagram. The samples show good emission tunability by monitoring the annealing temperature and the diode laser pump intensity. By properly adjusting the excitation power, white upconversion luminescence can be attained. Yb 3+ /Er 3+ /Tm 3+ -doped GdPO 4 nanophosphors appear, which have potential applications in the field of upconversion-based white lighting devices. [ABSTRACT FROM AUTHOR]

This study was focused on the development of an optimized method for the rapid synthesis of nano-scale HKUST-1 with high yield, high surface area and high CO 2 uptake capacity but under mild conditions. A series of HKUST-1 were synthesized under different conditions, such as preparation time, temperature, activation method, etc. It was found that the nano-scale HKUST-1 MOFs (T85-3-Pm4-120) was successfully synthesized at a high yield (87%) under low temperature (85 °C) using a mixture of Triethylamine (TEA), Cu 2+ and trimesic acid (TMA) with a molar ratio of 6:3:2. The highest porosity was achieved via this pristine HKUST-1 being activated (powder activation, drying at 120 °C) four times using methanol to remove impurities trapped in the pores. The best HKUST-1 MOFs (T85-3-Pm4-120) hereby prepared was then tested in CO 2 adsorption and exhibited an adsorption capacity of 2.5 mmol/g. It is therefore demonstrated that the new approach proposed in this study is a rapid and effective way to synthesize highly porous HKUST-1 MOFs under mild conditions, which is of comparable surface area and CO 2 uptake capacity with those MOFs prepared under harsh conditions. [ABSTRACT FROM AUTHOR]

Abstract It has been two decades since the lipid raft hypothesis was first presented. Even today, whether these nanoscale cholesterol-rich domains are present in cell membranes is not completely resolved. However, especially in the last few years, a rich body of literature has demonstrated both the presence and the importance of non-random distribution of biomolecules on the membrane, which is the focus of this review. These new developments have pushed the experimental limits of detection and have brought us closer to observing lipid domains in the plasma membrane of live cells. Characterization of biomolecules associated with lipid rafts has revealed a deep connection between biological regulation and function and membrane compositional heterogeneities. Finally, tantalizing new developments in the field have demonstrated that lipid domains might not just be associated with the plasma membrane of eukaryotes but could potentially be a ubiquitous membrane-organizing principle in several other biological systems. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo. Graphical abstract Unlabelled Image Highlights • Emergence of evidence showing compositional heterogeneity in plasma membrane • Functional organization of lipids is important for signaling and pathogen entry. • Lipid mediated organization is an emergent theme in diverse biological systems. [ABSTRACT FROM AUTHOR]

The nanoscale zero valent iron (NZVI) modified coal fly ash (CFA) magnetic composites (NZVI/CFA) were synthesized from the waste CFA and applied for the high-efficiency sequestration of U(VI) ions from water solution. The sequestration capacity of U(VI) ions on NZVI/CFA (0.62 mmol·g −1 ) was larger than that on bare CFA (0.25 mmol·g −1 ) or NZVI (0.38 mmol·g −1 ). The sequestration of U(VI) on NZVI and NZVI/CFA was primary controlled by outer-sphere surface complexation at low pH, and by inner-sphere surface complexation at high pH. According to the thermodynamic data and the adsorption isotherms' analysis, the U(VI) sorption process to the NZVI/CFA was spontaneous and endothermic. The main reaction mechanism was that, most of the soluble U(VI) ions were firstly adsorbed to NZVI/CFA and then the surface adsorbed U(VI) was partly reduced to U(VI) on the porous NZVI/CFA composites, and this synergistically affected U(VI) removal from solution to NZVI/CFA. The results of DFT calculation indicated that the NZVI/CFA had a strong sequestration capacity towards U(VI) and U(IV) ions, and the binding energy of U(IV) species was larger than that of U(VI) species, which evidenced the higher sorption of U(IV) than U(VI) on NZVI/CFA. The results showed that NZVI/CFA was an appropriate material for U(VI) sequestration from large volumes of actual effluent in wastewater cleanup. [ABSTRACT FROM AUTHOR]

Tailoring the properties of intermetallic alloys and phases, which resemble the foundation of a vast variety of high-temperature materials like nickel-based superalloys, is a challenge for improving this class of materials that requires comprehensive understanding of their three-dimensional (3D) nanochemistry. Here we use high-resolution microscopy techniques to reveal the microstructural and 3D nanochemical evolution of disordered γ particles from nanoscale nickel-rich heterogeneities (clusters) to γ spheres and then γ plates in an inverse Ni 78 Al 13 Ti 9 alloy having an ordered (L1 2 ) γ′ matrix. The γ particles require aging to achieve a thermodynamically stable morphology and composition, determined by reducing the Gibbs free energy. The fundamental analogy between γ particles in a γ′ matrix of an inverse alloy and γ particles in γ′ precipitates of a hierarchical Ni 86.1 Al 8.5 Ti 5.4 alloy is established. Our results demonstrate that this analogy can be harnessed as a novel approach for improving the properties of nickel-based superalloys. [ABSTRACT FROM AUTHOR]

Effect of surface spins in chromium oxide (Cr 2 O 3 ) coated maghemite (γ-Fe 2 O 3 ) nanoparticles (13 nm) as prepared by microwave plasma technique have been studied in detail. The temperature dependent zero field cooled/field cooled (ZFC/FC) measurements revealed the blocking temperature at T B  = 75 K. Simulated ZFC/FC curves exhibited large value of effective anisotropy of Cr 2 O 3 coated γ-Fe 2 O 3 nanoparticles as compared to bulk γ-Fe 2 O 3 but less than bare γ-Fe 2 O 3 nanoparticles. Bloch's law was fitted on M S -T data and revealed the values of Bloch's constant B = 3.523 × 10 −4  K −b and Bloch's exponent b = 1.10. The higher value of B than in bulk is due to weaker exchange coupling J (B ̴ 1/J) on the surface of nanoparticle due to disorder surface spins, while lower value of b is due to no spin wave excitation in presence of large energy band gap at nanoscale. Kneller's law fit on H C -T data deviated in all temperature range which is due to strong surface anisotropy, core-shell interactions and superparamagnetism. Interparticle interactions and spin glass behavior were investigated by using different physical laws for f-dependent ac susceptibility and they confirmed the presence of spin glass behavior which is due to disordered frozen surface spins and random interparticle interactions. [ABSTRACT FROM AUTHOR]

We review first how properties of curved surfaces can be studied using Hill’s thermodynamics, also called nano-thermodynamics. We proceed to show for the first time that Hill’s analysis is equivalent to Gibbs analysis for surfaces of constant curvatures (cylinders or spheres). This simplifies the study of such surfaces on the nano-scale, and opens up a possibility to study non-equilibrium systems in a systematic manner. [ABSTRACT FROM AUTHOR]

Nanoscale heterojunction of asymmetrical band structures and electron distributions at the interfaces is critical for activity enhancement in various catalytic applications. However, realization of facet-specific heterojunction remains challenging; yet it has been rarely studied in electrocatalysis. In this work, we first report the enhanced electrocatalytic performance of monolith Au/Si (111) heterojunction on Si micron-scale pyramids, prepared by alkaline Si-wafer etching with surface decoration of isolated gold nanoparticles (5–15 nm). The Au/Si (111) heterojunction exhibits the facet-dependent electrochemical activities superior to Au/Si (100). Varied Si etching levels enable the mixed exposure of Si (111) and Si (100); and the results further support the facet-dependent electrochemical enhancement. By excluding the effects of surface areas and defects, studies on the role of Si (111) reveal that the Au/Si (111) interface is very essential in improving the sensitivity and the detection limit at the heterojunction. This means that usage of well-controlled facets instead of merely facilitating electron transport can be considered in heterojunction electrocatalyst design. The H 2 O 2 sensing performance of Au/Si (111) is synergistically enhanced achieving 194 times greater sensitivity than the Au/Si (100) with a wide linear range from 0.01 to 55.55 mM, high sensitivity (171 μA mM −1  cm −2 ), and low detection limit of 1.24 μM. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) are defined as crystalline, open, coordination network architectures with potential voids. They have drawn momentous attention across several crossroads of material chemistry since their discovery, owing to an exciting plethora of application-oriented footprints left by this class of supramolecular network solids. The unmatched aspect of tunable coordination nanospace arising from the countless choice of pre-functionalized organic struts pertaining to varying lengths alongside multivariate coordination geometries/oxidation states of the metal nodes, bestows a distinct chemical tailorability facet to this class of porous materials. Amidst the two-decade long attention dedicated to the adsorption–governed purification of gases, the MOF literature has substantially expanded its horizon into the manifestation of industrially relevant liquid mixtures’ adsorptive separation–driven purification. Such chemical separation phenomena categorically encompasses high importance to the manufacturing and processing industry sectors, apart from the fundamental scientific pursuit of discovering novel physicochemical principles. Aimed at the energy-economic preparation of pure industrial feedstocks and their consequent usage as end products, structure–property correlations pursued in the alleys of coordination chemistry has led to major advancements in a number of critical separation frontiers, inclusive of biofuels (alcohol/water), diverse hydrocarbon mixtures, and chiral species. This comprehensive review summarizes the topical developments accrued in the field of MOF based liquid mixtures’ adsorptive separation phenomena, structure–selectivity relationships as well as the associated plausible mechanisms substantiating such behavior. [ABSTRACT FROM AUTHOR]

The scratching processes of monocrystalline and polycrystalline silicon carbide (SiC) with diamond grit were studied by molecular dynamics simulation to investigate the nanoscale material removal behavior. The results showed that, for both monocrystalline and polycrystalline SiC, the material removal processes were achieved by the phase transition to the amorphous structure. Large depth of cut and low scratching speed induced the large scratching forces, stress, and surface damage layer thickness. Less amorphous structure phase transition, smaller normal scratching force, and higher tangential stress were found in polycrystalline SiC, comparing to the monocrystalline SiC, due to the material soften caused by the microstructure, under all scratching conditions. Furthermore, the tangential stress showed highly dependent on the grain geometry and grain boundary (GB) location in polycrystalline. The subsurface damage layer in polycrystalline was little thinner than that in monocrystalline before the new GB generation at a low depth of cut and deteriorated at large depth of cut. In addition to the plastic deformation, which occurred in the monocrystalline SiC nanoscale scratching, the intergranular fracture and transgranular fracture were also observed through the GB generation and connection in polycrystalline SiC. [ABSTRACT FROM AUTHOR]

Microplastics and nanoplastics are emerging pollutants of global importance. They are small enough to be ingested by a wide range of organisms and at nano-scale, they may cross some biological barriers. However, our understanding of their ecological impact on the terrestrial environment is limited. Plastic particle loading in agroecosystems could be high due to inputs of some recycled organic waste and plastic film mulching, so it is vital that we develop a greater understanding of any potentially harmful or adverse impacts of these pollutants to agroecosystems. In this article, we discuss the sources of plastic particles in agroecosystems, the mechanisms, constraints and dynamic behaviour of plastic during aging on land, and explore the responses of soil organisms and plants at different levels of biological organisation to plastic particles of micro and nano-scale. Based on limited evidence at this point and understanding that the lack of evidence of ecological impact from microplastic and nanoplastic in agroecosystems does not equate to the evidence of absence, we propose considerations for addressing the gaps in knowledge so that we can adequately safeguard world food supply. [ABSTRACT FROM AUTHOR]

With the development of NEMSs (nano-electro-mechanical systems), the size-dependent behavior has been an active topic. The scale parameter seems an essential factor dominating mechanical behavior at nanoscale. However, is it always dominant? This is a question deserving careful investigation. For this reason, the buckling of a bi-layered PE (piezoelectric) nanobeam is analyzed. The main purpose is to reveal and compare the effects of the nonlocal scale, imperfect interface, interlaminar van der Waals force and loading ratio. The imperfect interface is modeled by normal and shear springs, and the van der Waals force is represented by the Hamaker formula. Based on the principle of virtual work, the analytical solution of the critical buckling loading is derived by using the trigonometric shear deformation theory. After the verification in some degenerated cases, parametric studies are conducted. It is indicated that if the nonlocal parameter varies in the typical range [0, 4 nm^2], it only has quite limited effect on the buckling behavior, as compared with the other three factors. In this case, although the buckling relies on the nonlocal scale, it is far more dependent on the conventional non-nanoscale factors. The conclusions can provide references for optimal design of NEMSs. [ABSTRACT FROM AUTHOR]

Much attention has been paid to extracting and isolating specific and well-known nanoparticles (especially for engineered nanomaterials) from complex environmental matrices. However, such research may not provide global information on actual contamination because nanoscale fragments exist as mixtures of various elements and matrices in the real environment. The present work first isolated and characterized nanoscale fragments in effluents from municipal wastewater treatment plants (WWTPs). The nanoscale fragments were found to be composed of 70–85% carbon and low amounts of oxygen, heavy metals and other elements and exhibited nanosheet topographies (approximately 0.87–1.31 nm thickness and 68–187 nm lateral length). Because the isolated nanoscale fragments were mixtures rather than one specific type of nanoparticle, they were present at high concentrations ranging from 0.07 to 0.55 mg/L. It was also found that the accumulation of nanoscale fragments in rice reached 0.59 mg/g under exposure to environmentally relevant concentrations, leading to marked phytotoxicity (e.g., ultrastructural damage to chloroplasts and mitochondria). Metabolic analysis revealed the toxicological mechanisms to be related to disorders of carbohydrate, amino acid and fatty acid metabolism. This study is the first to characterize the properties and analyze the toxicity of nanoscale fragments in the effluents of WWTPs. Given that WWTP effluents containing nanoscale fragments are continuously discharged to the soil, surface water and seas, nanoscale fragment materials deserve considerable attention in future work compared with the few widely studied engineered nanoparticles. [ABSTRACT FROM AUTHOR]

Friction on few-layer graphene supported by Si/SiO x and mica substrates was investigated using atomic force microscopy (AFM) and coordinated molecular dynamics (MD) simulations to examine friction hysteresis and wetting transparency. Experiments showed that graphene exhibited higher overall friction, as well as hysteresis, in high humidity conditions, while the hysteresis was not observed under dry conditions. Additionally, as samples were aged under ambient environmental conditions, the work of adhesion increased by an approximate factor of two, likely from oxidation of the surface or adsorption of oxygen containing species from the lab environment. When graphene was supported by mica substrates no significant friction hysteresis was observed. MD simulations showed similar influences to the friction forces with surface energy. Both experiments and simulations suggest that wetting transparency, or a small variation in surface energy resulting from varying the number of graphene layers, contributes to the layer dependent friction forces measured on graphene. [ABSTRACT FROM AUTHOR]

Increasing the recrystallization resistance and the mechanical properties of aluminum-based alloys is possible due to the formation of a nanoscale L1 2 -structured Al 3 Zr phase. Treatment conditions and alloys composition affect the size and density of dispersoids and their final properties. In this work we analyze the decomposition of the supersaturated solid solution in the as-cast Al-3%Mg-0.25%Zr alloy for different annealing modes to understand the precipitation kinetics of the Al 3 Zr phase in the presence of Mg. We found that both discontinuous and continuous precipitation mechanisms of the Al 3 Zr phase are possible in the studied low-alloyed material. One-step annealing leads to the formation of coarse (17 nm) spherical precipitates of a coherent L1 2 -structured Al 3 Zr phase and discontinuously formed fan-shaped aggregations of the same phase. Two-step annealing provided for the maximum precipitation hardening with the formation of high-density nanoscale (7 nm) dispersoids of the Al 3 Zr phase. This study highlights the importance of the annealing mode of the as-cast material for achieving a high density of the fine L1 2 structured Al 3 Zr phase and the maximum hardening effect. [ABSTRACT FROM AUTHOR]

Two wear methods, line scanning and area scanning, were investigated to clarify their effect on wear experimental results at nanoscale. Wear tests of pure copper against diamond tip in vacuum and silicon against SiO 2 tip in water were performed using atomic force microscopy. Results show that two scanning methods can result in marked differences in experimental results for either pure mechanical wear or tribochemical wear. The variation in wear rate with sliding cycle indicates that the nanowear of material surface is a dynamic evolution process, which highly depends on the scanning methods. Line scanning is usually a simple and efficient wear method that can markedly change the interfacial contact profile and even induce a regional “work hardening” on the contact interface. By tuning the scan overlap rate, area scanning can reduce the influence of thermal drift of instrument and local defects of samples, as well as better present wear behaviors of material surface in initial wear stage. This study not only elucidates the importance of choosing wear methods as well as scan parameters in nanotribological investigations, but also provides an in-depth understanding of nanowear behaviors of material surfaces. [ABSTRACT FROM AUTHOR]

Hierarchical ZSM-5 zeolites were prepared by “Dry Gel Conversion-Steam Assisted Crystallization” (DGC-SAC) procedure without the involvement of additional template. Moreover, the formation mechanism and feather of mesopores were summarized. Nanoscale Kirkendall effect was existed in the growth of zeolite crystals under high SiO 2 /TPA + ratio, which was responsible for the production of intra-crystal mesopores. However, small ZSM-5 nano-crystallites, with the average diameter of <50 nm, were successfully synthesized under low SiO 2 /TPA + ratio. The random assembly of these nano-crystallites gave rise to abundant inter-crystal mesopores within these nano-crystallites zeolites. Benefiting from the significantly higher concentration of TPA + at the surface of amorphous aluminosilicate during the DGC-SAC process, the DGC-SAC procedure exhibited higher usage efficiency of template (TPA + ) than that of conventional “Hydrothermal Crystallization” (HC) route, and the ZSM-5 zeolites with a low consumption of TPA + (SiO 2 /TPA +  = 53.7) could be successfully synthesized by DGC-SAC method. Compared with the conventional ZSM-5 zeolites prepared by HC routes, the hierarchical ZSM-5 zeolites prepared by DGC-SAC procedure exhibited significantly higher catalytic lifetime and selectivity of light aromatics (benzene (B), toluene (T) and xylene (X)) in aromatization of methanol under same low addition of TPA + (SiO 2 /TPA +  = 13.5). Moreover, the produced hierarchical ZSM-5 zeolites (SiO 2 /TPA +  = 13.5) also exhibited superior catalyst stability after being further hydrothermally treated at 160 °C for 72 h. TG analysis of all used catalysts confirmed that the produced hierarchical ZSM-5 zeolites had higher coke capability and lower average rate of coke formation. [ABSTRACT FROM AUTHOR]

Hydrogen is an important biomarker for the human digestive system. However, accurate detection of ppm-level hydrogen in breath is difficult due to the competing detection of high concentration water. We fabricated Pt thin films that respond to hydrogen in air at concentrations as low as 500 ppb. In both dry and humid air, these films have almost identical response to hydrogen, i.e., their resistance decreases linearly with increasing hydrogen concentration regardless of relative humidity. Even at high relative humidity, these Pt thin films can detect ppm-level hydrogen. Furthermore, it was strongly suggested that these films can be applied to low-level hydrogen in the air expired by a healthy human. Based on the chemical kinetics, namely the adsorption and desorption of hydrogen and oxygen, the sensor response is quantitatively described by relating the hydrogen surface coverage to the magnitude of electron scattering at the Pt surface. The proposed model successfully reproduces the effects of hydrogen concentration and time on the sensor response, particularly at hydrogen concentrations below 20 ppm. Based on this model, these Pt thin film sensors have the potential to detect 1 ppm hydrogen in expired air within 30 s. [ABSTRACT FROM AUTHOR]