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Exploiting the chirality of nanometric structures to modulate biological systems is an emerging and compelling area of research. In this study, we reveal that chiral polyurea nanocapsules exhibit significant stereoselective interactions with albumins from various sources despite their nearly neutral surface potential. Moreover, these interactions can be modulated by altering the nanocapsule surface composition, offering new opportunities to impact their distribution and, if used as a drug delivery system, the pharmacokinetics of the drug. Notably, these interactions promote preferential cellular internalization of only one chiral configuration. We synthesized chiral polyurea nanocapsules with reproducible sizes via interfacial polymerization between toluene 2,4-diisocyanate and d- or l-lysine enantiomers on a volatile oil-in-water emulsion interface, followed by solvent evaporation. Further synthesis optimization reduced the capsule size to a range compatible with in vivoadministration, and capsules with alternating chiral patterns were also produced. The stereoselective interactions with albumins were assessed through capsule size changes, fluorescence quenching, and surface charge measurements. Biocompatibility, stability, and cellular internalization were evaluated. Additionally, scanning transmission electron and atomic force microscopy were carried out to assess the capsule shape, surface composition, and morphology. We discovered that d-nanocapsules exhibited 2.1–2.6 times greater albumin adsorption compared with their l-counterparts. This difference is attributed to the distinct morphology of d-nanocapsules, characterized by a more concave shape, central depression, and rougher surface. The extent of adsorption could be finely tuned by adjusting the d- and l-lysine monomer ratios during synthesis. Both chiral configurations demonstrated biocompatibility and stability with d-nanocapsules showing a 2.5-fold increase in cellular internalization.

Phosphide-based nanocrystals (NCs), including InP and Cu3–xP, are relevant for applications in light-emitting devices and catalysis, yet their synthetic design is limited in terms of size range and homogeneity. We report the synthesis of uniform and size-controlled emissive wurtzite-phase InP NCs formed via cation exchange from Cu3–xP. First, size-controlled Cu3–xP NCs are synthesized by the formation of metallic Cu0NCs and their phosphidation to Cu3–xP. By changing the ligands and precursor concentrations, the NC size is varied between 5 and 13 nm. Using cation exchange, InP NCs are then generated. As the surface of InP NCs is prone to oxidation and defects that decrease their emission, we performed a reaction with NOBF4. This yields InP NCs with resolved absorption features and efficient band-gap emission as a result of impurity removal and surface passivation. The effect of water, acid, and halides on the balance of NC etching and surface passivation is studied. With this approach, high-quality wurtzite InP NCs are obtained while the emission is tuned between 810 and 600 nm. The obtained NCs are potential building blocks for catalytic and optoelectronic applications.

The fusion step in the formation of colloidal quantum dot molecules, constructed from two core/shell quantum dots, dictates the coupling strength and hence their properties and enriched functionalities compared to monomers. Herein, studying the monomer size effect on fusion and coupling, we observe a linear relation of the fusion temperature with the inverse nanocrystal radius. This trend, similar to that in nanocrystal melting, emphasizes the role of the surface energy. The suggested fusion mechanism involves intraparticle ripening where atoms diffuse to the reactive connecting neck region. Moreover, the effect of monomer size and neck filling on the degree of electronic coupling is studied by combined atomistic-pseudopotential calculations and optical measurements, uncovering strong coupling effects in small QD dimers, leading to significant optical changes. Understanding and controlling the fusion and hence coupling effect allows tailoring the optical properties of these nanoscale structures, with potential applications in photonic and quantum technologies.

Wire arc additive manufacturing (WAAM) of Mg-RE (rare-earth)-Zn alloys is important for meeting the requirements of lightweight large-scale components with high manufacturing flexibility. The Mg-8.1Gd-2.6Y-0.7Zn-0.5Zr (GWZ831K, wt.%) alloys were fabricated through the use of WAAM technology, and the microstructure evolution along the building direction and corresponding mechanical properties were then studied. The as-built sample in this paper was composed of finely equiaxed ɑ-Mg grains, eutectic (Mg, Zn)3(Gd, Y) phase, cubic phase, and γʹ precipitates. Furthermore, due to the in-suit heat treatments that were induced by the multiple thermal cycles, more γʹ precipitates were observed in the middle region. The microstructures at different heights were characterized by alternatively distributed fine equiaxed grains (melt pool boundaries, MPB) and coarse equiaxed grains (melt pools, MP). The mechanical properties of the as-built component were found to exhibit yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of 159 ± 1.0 MPa, 237 ± 4.0 MPa, and 6.7 ± 0.4 % in the building direction (BD) and 163 ± 5.1 MPa, 242 ± 8.7 MPa, and 7.0 ± 0.7 % in the traveling direction (TD). This demonstrates that the WAAM-processed GWZ831K alloy has good isotropy.

In this paper, the effect of two-stage homogenisation treatment on the evolution of the second phase was investigated. The microstructure of the extruded 7055 aluminium alloy was composed of α(Al) matrix and other second phases, including MgZn2, Al2CuMg, and Al7Cu2Fe phases. The segregation of second phase was serious and the content was 27.9%. During the 460°C × 24 h homogenisation, MgZn2phases dissolved quickly, but there was still a significant amount of Al2CuMg phases present. After two-stage homogenisation (460°C × 24 h + 480°C × 10 h), the content of Al2CuMg phase decreased from 15% to 3% and the degree of segregation was reduced. In addition, the mechanical properties of the extruded 7055 alloy were effectively improved.

In this paper, the effect of two-stage homogenisation treatment on the evolution of the second phase was investigated. The microstructure of the extruded 7055 aluminium alloy was composed of a(Al) matrix and other second phases, including MgZn2, Al2CuMg, and Al7Cu2Fe phases. The segregation of second phase was serious and the content was 27.9%. During the 460°C?×?24?h homogenisation, MgZn2phases dissolved quickly, but there was still a significant amount of Al2CuMg phases present. After two-stage homogenisation (460°C?×?24?h?+?480°C?×?10?h), the content of Al2CuMg phase decreased from 15% to 3% and the degree of segregation was reduced. In addition, the mechanical properties of the extruded 7055 alloy were effectively improved.

Colloidal semiconductor quantum dots are robust emitters implemented in numerous prototype and commercial optoelectronic devices. However, active fluorescence colour tuning, achieved so far by electric-field-induced Stark effect, has been limited to a small spectral range, and accompanied by intensity reduction due to the electron–hole charge separation effect. Utilizing quantum dot molecules that manifest two coupled emission centres, we present a unique electric-field-induced instantaneous colour-switching effect. Reversible emission colour switching without intensity loss is achieved on a single-particle level, as corroborated by correlated electron microscopy imaging. Simulations establish that this is due to the electron wavefunction toggling between the two centres, induced by the electric field, and affected by the coupling strength. Quantum dot molecules manifesting two coupled emission centres may be tailored to emit distinct colours, opening the path for sensitive field sensing and colour-switchable devices such as a novel pixel design for displays or an electric-field-induced colour-tunable single-photon source.

Semiconductor nanocrystals (NCs) are promising photocatalysts due to their high surface area to volume ratio and tunable physicochemical properties. Of particular interest are earth-abundant metal oxides, such as ZnO and CuO, which are stable under ambient conditions and in aqueous media and are environmentally and biologically compatible. While CuO NCs are efficient catalytic and antimicrobial materials featuring strong and broad absorption in the visible region, their challenging surface chemistry and low colloidal stability so far limited their wide implementation as photocatalysts. On the other hand, colloidal ZnO NCs function as excellent photocatalysts in various media, but their absorption is limited to the UV region. Herein, colloidal antimicrobial Cu1–xZnxO NCs are synthesized via a facile and cost-effective method, forming a unique spatial dependent structure and composition, with higher zinc concentration on the surface. The doped NCs show enhanced antimicrobial activity increasing with higher amount of dopant. Furthermore, the NCs exhibit superior antimicrobial activity upon visible light illumination effectively eradicating even multidrug resistant bacteria, due to increased ion migration and photocatalytic formation of reactive oxygen species. Such Cu1–xZnxO NCs, therefore, show promise as biocompatible antimicrobial materials that can be utilized under ambient conditions in diverse scenarios enabled by wet chemical processing.

Customized heat treatment is essential for enhancing the mechanical properties of additively manufactured metallic materials, especially for alloys with complex phase constituents and heterogenous microstructure. However, the interrelated evolutions of different microstructure features make it difficult to establish optimal heat treatment processes. Herein, we proposed a method for customized heat treatment process exploration and establishment to overcome this challenge for such kind of alloys, and a wire arc additively manufactured (WAAM) Mg-Gd-Y-Zn-Zr alloy with layered heterostructure was used for feasibility verification. Through this method, the optimal microstructures (fine grain, controllable amount of long period stacking ordered (LPSO) structure and nano-scale β′ precipitates) and the corresponding customized heat treatment processes (520 °C/30 min + 200 °C/48 h) were obtained to achieve a good combination of a high strength of 364 MPa and a considerable elongation of 6.2%, which surpassed those of other state-of-the-art WAAM-processed Mg alloys. Furthermore, we evidenced that the favorable effect of the undeformed LPSO structures on the mechanical properties was emphasized only when the nano-scale β′ precipitates were present. It is believed that the findings promote the application of magnesium alloy workpieces and help to establish customized heat treatment processes for additively manufactured materials.

Transition metal oxides (TMOs) have been widely studied as potential next-generation anode materials, owing to their high theoretical gravimetric capacity. However, to date, these anodes syntheses are plagued with time-consuming preparation processes, two-dimensional electrode fabrication, binder requirements, and short operational cycling lives. Here, we present a scalable single-step reagentless process for the synthesis of highly dense Mn3O4-based nanonetwork anodes based on a simple thermal treatment transformation of low-grade steel substrates. The monolithic solid-state chemical self-transformation of the steel substrate results in a highly dense forest of Mn3O4nanowires, which transforms the electrochemically inactive steel substrate into an electrochemically highly active anode. The proposed method, beyond greatly improving the current TMO performance, surpasses state-of-the-art commercial silicon anodes in terms of capacity and stability. The three-dimensional self-standing anode exhibits remarkably high capacities (>1500 mA h/g), a stable cycle life (>650 cycles), high Coulombic efficiencies (>99.5%), fast rate performance (>1.5 C), and high areal capacities (>2.5 mA h/cm2). This novel experimental paradigm acts as a milestone for next-generation anode materials in lithium-ion batteries, and pioneers a universal method to transform different kinds of widely available, low-cost, steel substrates into electrochemically active, free-standing anodes and allows for the massive reduction of anode production complexity and costs.

One of the challenges for metasurface research is upscaling. The conventional methods for fabrication of metasurfaces, such as electron-beam or focused ion beam lithography, are not scalable. The use of ultraviolet steppers or nanoimprinting still requires large-size masks or stamps, which are costly and challenging in further handling. This work demonstrates a cost-effective and lithography-free method for printing optical metasurfaces. It is based on resonant absorption of laser light in an optical cavity formed by a multilayer structure of ultrathin metal and dielectric coatings. A nearly perfect light absorption is obtained via interferometric control of absorption and operating around a critical coupling condition. Controlled by the laser power, the surface undergoes a structural transition from random, semiperiodic, and periodic to amorphous patterns with nanoscale precision. The reliability, upscaling, and subwavelength resolution of this approach are demonstrated by realizing metasurfaces for structural colors, optical holograms, and diffractive optical elements.

Indium phosphide (InP) nanocrystals are emerging as an alternative to heavy metal containing nanocrystals for optoelectronic applications but lag behind in terms of synthetic control. Herein, luminescent wurtzite InP nanocrystals with narrow size distribution were synthesized via a cation exchange reaction from hexagonal Cu3P nanocrystals. A comprehensive surface treatment with NOBF4was performed, which removes excess copper while generating stoichiometric In/P nanocrystals with fluoride surface passivation. The attained InP nanocrystals manifest a highly resolved absorption spectrum with a narrow emission line of 80 meV, and photoluminescence quantum yield of up to 40%. Optical anisotropy measurements on ensemble and single particle bases show the occurrence of polarized transitions directly mirroring the anisotropic wurtzite lattice, as also manifested from modeling of the quantum confined electronic levels. This shows a green synthesis path for achieving wurtzite InP nanocrystals with desired optoelectronic properties including color purity and light polarization with potential for diverse optoelectronic applications.

Epitaxial growth of a protective semiconductor shell on a colloidal quantum dot (QD) core is the key strategy for achieving high fluorescence quantum efficiency and essential stability for optoelectronic applications and biotagging with emissive QDs. Herein we investigate the effect of shell growth rate on the structure and optical properties in blue-emitting ZnSe/ZnS QDs with narrow emission line width. Tuning the precursor reactivity modifies the growth mode of ZnS shells on ZnSe cores transforming from kinetic (fast) to thermodynamic (slow) growth regimes. In the thermodynamic growth regime, enhanced fluorescence quantum yields and reduced on–off blinking are achieved. This high performance is ascribed to the effective avoidance of traps at the interface between the core and the shell, which are detrimental to the emission properties. Our study points to a general strategy to obtain high-quality core/shell QDs with enhanced optical properties through controlled reactivity yielding shell growth in the thermodynamic limit.

Mixed cation perovskites are currently the most efficient perovskite materials used in perovskite solar cells. Mixing two cations inside a perovskite structure results in enhanced flexibility when designing interesting material properties. Moreover, using two inorganic cations in the same perovskite maintains the advantage of fully inorganic structures. A fascinating subject to investigate is therefore the nanoscale synthesis and the properties of such mixed inorganic cation perovskites. In this work we mixed Rb and Cs inorganic atoms inside perovskite nanoparticles. We explored down to the atomic resolution different Rb and Cs concentrations and performed the chemical mapping of single nanoparticles. At medium concentrations, the Rb atoms are observed in the core of the particles, whereas the Cs atoms are located in the shell region, forming core–shell structures. However, if there are high concentrations of Rb, a phase separation occurs because bulk perovskite based solely on Rb cations is not stable at room temperature. Density functional theory calculations support our experimental observations by showing that a stable nanoparticle is formed when the Rb atoms are located inside the particle and not on the surface. Our work demonstrates the importance of understanding the perovskite structure at the atomic level, leading to the formation of mixed cation bulk perovskites and nanoparticles and to improved perovskite stability. A new phase of cesium lead bromide (Cs6Pb5Br16) related to the Rb6Pb5Cl16structure is also reported.

Magnesium and its alloys, as a promising class of materials, is popular in lightweight application and biomedical implants due to their low density and good biocompatibility. Additive manufacturing (AM) of Mg and its alloys is of growing interest in academia and industry. The domain-by-domain localized forming characteristics of AM leads to unique microstructures and performances of AM-process Mg and its alloys, which are different from those of traditionally manufactured counterparts. However, the intrinsic mechanisms still remain unclear and need to be in-depth explored. Therefore, this work aims to discuss and analyze the possible underlying mechanisms regarding defect appearance and elimination, microstructure formation and evolution, and performance improvement, based on presenting a comprehensive and systematic review on the relationship between process parameters, forming quality, microstructure characteristics and resultant performances. Lastly, some key perspectives requiring focus for further progression are highlighted to promote development of AM-processed Mg and its alloys and accelerate their industrialization.

Biomineralization is a mineral precipitation process occurring in the presence of organic molecules and used by various organisms to serve a structural and/or a functional role. Many biomineralization processes occur in the presence of extracellular matrices that are composed of proteins and polysaccharides. Recently, there is growing evidence that bacterial biofilms induce CaCO3mineralization and that this process may be related with their extracellular matrix (ECM). In this study we explore, in vitro, the effect of two bacterial ECM proteins, TasA and TapA, and an exopolysaccharide, EPS, on calcium carbonate crystallization. We have found that all the three biopolymers induce the formation of complex CaCO3structures. The crystals formed in the presence of the EPS are very diverse in morphology and they are either calcite or vaterite in structure. However, more uniformly sized calcite crystals are formed in the presence of the proteins; these crystals are composed of single crystalline domains that assemble together into spherulites (in the presence of TapA) or dumbbell-like shapes (in the presence of TasA). Our results suggest the EPS affects the nucleation of calcium carbonate when it induces the formation of vaterite crystals and that unlike EPS, the proteins stabilize preformed calcite nuclei and induce their aggregation into complex calcite structures. Biomineralization processes induced by bacterial ECM macromolecules make biofilms more robust and difficult to remove when they form, for example, on pipes and filters in water desalination systems or on ship hulls. Understanding the formation conditions and mechanism of formation of calcium carbonate in the presence of bacterial biopolymers may lead to the design of suitable mineralization inhibitors.

CrGeTe3(CGT) is a semiconducting vdW ferromagnet shown to possess magnetism down to a two-layer thick sample. Although CGT is one of the leading candidates for spintronics devices, a comprehensive analysis of CGT thickness dependent magnetization is currently lacking. In this work, we employ scanning SQUID-on-tip (SOT) microscopy to resolve the magnetic properties of exfoliated CGT flakes at 4.2 K. Combining transport measurements of CGT/NbSe2samples with SOT images, we present the magnetic texture and hysteretic magnetism of CGT, thereby matching the global behavior of CGT to the domain structure extracted from local SOT magnetic imaging. Using this method, we provide a thickness dependent magnetization state diagram of bare CGT films. No zero-field magnetic memory was found for films thicker than 10 nm, and hard ferromagnetism was found below that critical thickness. Using scanning SOT microscopy, we identify a unique edge magnetism, contrasting the results attained in the CGT interior.

Coupled colloidal quantum dot (CQD) dimers represent a new class of artificial molecules composed of fused core/shell semiconductor nanocrystals. The electronic coupling and wave function hybridization are enabled by the formation of an epitaxial connection with a coherent lattice between the shells of the two neighboring quantum dots where the shell material and its dimensions dictate the quantum barrier characteristics for the charge carriers. Herein we introduce a colloidal approach to control the neck formation at the interface between the two CQDs in such artificial molecular constructs. This allows the tailoring of the neck barrier in prelinked homodimers formed via fusion of multifaceted wurtzite CdSe/CdS CQDs. The effects of reaction time, temperature, and excess ligands are studied. The neck filling process follows an intraparticle ripening mechanism at relatively mild reaction conditions while avoiding interparticle ripening. The degree of surface ligand passivation plays a key role in activating the surface atom diffusion to the neck region. The degree of neck filling strongly depends also on the initial relative orientation of the two CQDs, where homonymous plane attachment allows for facile neck growth, unlike the case of heteronymous plane attachment. Upon neck filling, the observed red-shift of the absorption and fluorescence measured both for ensemble and single dimers is assigned to enhanced hybridization of the confined wave function in CQD dimer molecules, as supported by quantum calculations. The fine-tuning of the particle interface introduced herein provides therefore a powerful tool to further control the extent of hybridization and coupling in CQD molecules.