As a significant metal chalcogenide, copper sulfide (Cu2−xS, 0 < x < 1), with a unique semiconducting and nontoxic nature, has received significant attention over the past few decades. Extensive investigations have been employed to the various Cu2−xS micro-/nanostructures owing to their excellent optoelectronic behavior, potential thermoelectric properties, and promising biomedical applications. As a result, micro-/nanostructured Cu2−xS with well-controlled morphologies, sizes, crystalline phases, and compositions have been rationally synthesized and applied in the fields of photocatalysis, energy conversion, in vitro biosensing, and in vivo imaging and therapy. However, a comprehensive review on diversified Cu2−xS micro-/nanostructures is still lacking; therefore, there is an imperative need to thoroughly highlight the new advances made in function-directed Cu2−xS-based nanocomposites. In this review, we have summarized the important progress made in the diversified Cu2−xS micro-/nanostructures, including that in the synthetic strategies for the preparation of 0D, 1D, 2D, and 3D micro-/nanostructures (including polyhedral, hierarchical, hollow architectures, and superlattices) and in the development of modified Cu2−xS-based composites for enhanced performance, as well as their various applications. Furthermore, the present issues and promising research directions are briefly discussed.

Hollow micro/nanostructures possess fascinating physicochemical properties that would generate great application potential in the fields of catalysis, sensing and energy conversion. In the past decades, much more efforts have been employed in the exploration and enrichment of copper-based binary oxides, CuxO (x = 2, 1); thus a number of CuxO micro/nanostructures with well-controlled ingredients and morphologies have been rationally synthesized and applied. However, a thorough summary on hollow CuxO materials has been lacking so far and it is urgently necessary to further promote the progress in novel function-directed CuxO-based micro/nanostructures. In this review, we will comprehensively summarize the important advances in hollow CuxO micro/nanostructures with tailored morphologies, including the universal synthesis strategies and formation mechanisms, the interfacial Cu–O atomic structures as well as the intrinsic properties, and their potential applications. Remarks on emerging issues and promising research directions are also discussed.

Novel etched Cu2O cubes with exposed {110} facets are synthesized via an oxidative etching method at room temperature. The photocatalytic performance indicates that these architectures show higher photocatalytic activity than that of the normal Cu2O cubes in the degradation of methylene orange.

Inspired by a sequential hydrolysis–precipitation mechanism, morphology-controllable hierarchical cupric oxide (CuO) nanostructures are facilely fabricated by a green water/ethanol solution-phase transformation of Cux(OH)2x−2(SO4) precursors in the absence of any organic capping agents and without annealing treatment in air. Antlerite Cu3(OH)4(SO4) precursors formed in a low volume ratio between water and ethanol can transform into a two-dimensional (2D) hierarchical nanoporous CuO ribbon assembly of free-standing nanoneedle building blocks and hierarchical nanoneedle-aggregated CuO flowers. Brochantite Cu4(OH)6(SO4) precursors formed in a high volume ratio between water and ethanol can transform into hierarchical nanoplate-aggregated CuO nanoribbons and nanoflowers. Such 2D hierarchical nanoporous CuO ribbons serving as a promising electrode material for nonenzymatic glucose detection show high sensitivity, a low detection limit, fast amperometric response and good selectivity. Significantly, this green water-induced precursor-hydrolysis method might be used to control effectively the growth of other metal oxide micro-/nanostructures.

Owing to the shape-dependent catalytic activity of Fe3O4 nanoparticles, controlling their morphology is of great significance. In this work, we propose a simple, nontoxic, water-based strategy for the fabrication of magnetic nanoparticle/hydrogel nanocomposites in which highly crystalline Fe3O4 nanooctahedra can be fabricated in situ within a negatively charged hydrogel matrix. The morphology of the Fe3O4 nanocrystals can be easily tuned by adjusting the crosslinking concentration of the hydrogel. Furthermore, the catalytic activities of the magnetic nanocomposites were studied, and the magnetic nanocomposite loaded with Fe3O4 nanooctahedra exhibited excellent catalytic activity and provided a sensitive response toward H2O2 detection. This scalable approach for the fabrication of magnetic nanocomposites, loaded with morphology controllable Fe3O4 nanoparticles, potentially promotes their applications in biotechnology and environmental chemistry.

We have demonstrated a facile anion-assisted strategy for the synthesis of nanoparticle-aggregated CuO nanoellipsoids. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). The nanoparticle-aggregated CuO nanoellipsoids serve as a promising electrode material for a non-enzymatic glucose biosensor which shows high sensitivity, good reproducibility, a fast amperometric response and good selectivity. The study is of great importance in the bottom-up assembly of tunable ordered architectures, and offers a chance to understand the formation mechanism and fundamental significance of an anion-assisted strategy for the synthesis of metal oxides. Significantly, it is believed that the anion-assisted synthetic approach reported here could provide a facile way to design more novel metal oxide architectures with well-defined shapes.

In this report, a novel type of a hollow CuO polyhedron-modified electrode for sensitive nonenzymatic glucose detection has been fabricated by a templating approach. The morphologies and structures were characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS). These results show that the as-prepared hollow CuO consists of numerous CuO nanoplates. The electrochemical performance for glucose detection was investigated by cyclic voltammetry and chronoamperometry. The hollow CuO polyhedron-modified electrode exhibits a high sensitivity of 1112 μA mM−1 cm−2 with a detection limit of 0.33 μM (S/N = 3) at +0.55 V, and the linear range is up to 4 mM. Moreover, the hollow CuO polyhedron-modified electrode is highly resistant to the interference from interfering species such as sodium chloride (NaCl), ascorbic acid (AA) and uric acid (UA). The hollow CuO polyhedron-modified electrode exhibits high sensitivity, low detection limit, good stability and fast response towards the oxidation of glucose; thus, it may be a promising nonenzymatic glucose sensor.

The template-strategy is one of the most significant techniques for the controllable synthesis of hollow architectures with unique structures, morphologies and properties. In this review, we selectively summarize the general principles of the Cu2O-templated strategy for the synthesis of definable hollow architectures and cover the recent progress in this area. We elaborate on the use of low-cost Cu2O templates for synthesizing different types of hollow cages (including copper sulfide, metal oxide, and metal) categorized by their chemical reaction mechanisms, followed by the challenges and perspective on Cu2O-templated strategy and its potential future directions.

For the first time, one-pot solution-phase selective-etching to create cuboctahedral Cu2O crystals enclosed by both stepped {111} surfaces and smooth {100} surfaces has been demonstrated. Investigation of photocatalytic performances indicates that the stepped cuboctahedral Cu2O crystals have higher photocatalytic activities than those of the common smooth ones.

Morphology is a primary part of designing metal nanocrystals and nanomaterials with controlled functional properties. Here, we demonstrate the potential of foreign sulfate ions to tune the silver dendrites to highly branched chains through a simple galvanic replacement reaction without introducing any organic surfactants. We further illustrate the underlying mechanism according to diffusion-limited aggregation (DLA) in the presence of sulfate ions. The special aspects of this simple synthetic strategy are the control of both the nucleation process and the subsequent crystal growth stage by using sulfate ions as the ionic surfactants thereby tuning the total surface energies on various crystal facets in solution and transforming crystal growth habits of the products. Moreover, the highly branched silver chains (HBSCs) with pure surfaces have been successfully employed as a Raman probe for surface-enhanced Raman spectroscopic analysis of rhodamine 6G (R6G). The particular morphology of those HBSCs also makes them find potential applications in biosensing, catalysis and optics.

We have demonstrated a facile copper-templated approach for synthesis of nanoparticle-aggregated hollow gold microcages. The as-prepared gold microcages, as active substrates, exhibit remarkable surface-enhanced Raman scattering activity for 4-mercaptobenzoic acid.

Polyhedral inorganic crystals exposed with controllable-index facets is as significant as size, composition, phase and crystallinity in determining their chemical and physical properties. To accurately tune the exposed facets and morphologies of crystals is imperative because a thorough understanding of the formation mechanism and unique performance has significant scientific value. Better understanding of the control of exposed facets would bring about new capability for us to design necessary structures for actual applications. This article presents recent research progress in the development of polyhedral Cu2O architectures, focusing on the expanding of crystal-facet-dependent properties. The challenge and prospects of polyhedral Cu2O architectures are discussed. The present article provides important scientific references and a basis for future work.

An interesting morphology-evolution of Cu2O from cubic, edge-truncated cubic, edge- and corner-truncated octahedral, truncated octahedral, and finally to octahedral architectures was readily achieved by adjusting the concentration of hydroxyl. When evaluated for their photocatalytic performances, these polyhedral Cu2O crystals manifest shape-dependent properties.

We have demonstrated an interesting approach for the one-pot synthesis of cupric oxide (CuO) nanourchins with sub-100 nm through a sequential dissolution–precipitation process in a water/ethanol system. The first stage produces a precursory crystal [Cu7Cl4(OH)10H2O] that is transformed into monoclinic CuO nanourchins during the following stage. Water is a required reactant for the morphology-controlled growth of different CuO nanostructures. When evaluated for their nonenzymatic glucose-sensing properties, these CuO nanourchins manifest higher sensitivity. Significantly, this water-dependent precursor transformation method may be widely used to effectively control the growth of other metal oxide nanostructures.Keywords: copper oxide; nanourchins; nonenzymatic glucose sensor; water/ethanol;

We have demonstrated a facile Cu2O-templated approach for the synthesis of nanoparticle-aggregated hollow copper microcages (HCMC). As substrates, these HCMC exhibit surface enhanced Raman scattering (SERS) activity for rhodamine 6G (R6G) and 4-mercaptobenzoic acid (4-MBA).

We have demonstrated the significant evidence on a green synthesis for the ordered-aggregation-driven growth from surfactant-free one-dimensional (1D) CuO nanosubunits into dimension-controlled mesostructures (three-dimensional (3D) mesospindles and two-dimensional (2D) mesoplates) by an additive-free complex–precursor solution route. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). The formation of CuO mesostructures here is essentially determined by the characteristic of [Cu(OH)4]2− precursors, and an oriented nanoparticle aggregation with tailoring shapes in different dimensions can be achieved in different concentration of reactants at higher reaction temperature. The 3D “layer-by-layer” growth of mesostructural CuO spindles is successfully synthesized in low concentrations of reagents, while the 2D “shoulder-by-shoulder” growth of mesostructural CuO plates is obtained in high concentrations of reagents. The study is of great importance in the bottom-up assembly of controllable ordering architectures, and offers a good opportunity to understand the fundamental significance for the investigation of the formation mechanism and growth process of surfactant-free CuO mesostructures with controllable aggregation-based behaviours. Additionally, we further demonstrated that such CuO mesocrystals could serve as a potential photocatalyst for the degradation of rhodamine B (RhB) under visible light irradiation in the presence of hydroxide water (H2O2). The results also suggest that these 3D mesostructural CuO spindles exhibit a higher adsorption and photocatalytic degradation of RhB than that of 2D mesostructural CuO plates.

We have demonstrated significant evidence of a solvent-dependent synthesis of hierarchical Cu7S4 polycrystalline nanocage assemblies with controllable aggregation-based building blocks by a sacrificial Cu2O template approach. The formation of a hierarchical Cu7S4 polycrystalline nanocage is essentially determined by a Kirkendall effect, which is attributed to the tailored-aggregation behaviour of the nanoscale building blocks during the replacement/etching process in different polarities of solvent. The hierarchical Cu7S4 polycrystalline nanocage assembly of nanoparticle building blocks was prepared in pure water, while the hierarchical Cu7S4 polycrystalline nanocage assembly of twinned nanoplate building blocks was successfully synthesized in an anhydrous ethanol capping environment. Such a hierarchical Cu7S4 polycrystalline nanocage assembly of twinned nanoplate building blocks exhibits a higher photocatalytic activity than that of the common polycrystalline ones. A nanotwin-dependent photochemical mechanism has been proposed. Significantly, this study is of great importance in bottom-up assembly of controllable ordered architectures, and offers a good opportunity to understand the fundamental importance of the formation mechanism and growth process of hierarchical Cu7S4 polycrystalline nanocages with controllable aggregation-based building blocks.

For the first time, a facile, one-pot water/ethanol solution-phase transformation of Cu2(NO3)(OH)3 precursors into bicomponent CuO hierarchical nanoflowers is demonstrated by a sequential in situ dissolution–precipitation formation mechanism. The first stage produces a precursory crystal (monoclinic Cu2(NO3)(OH)3) that is transformed into monoclinic CuO nanoflowers during the following stage. Water is a required reactant, and the morphology-controlled growth of CuO nanostructures can be readily achieved by adjusting the volume ratio between water and ethanol. Such a bicomponent CuO hierarchical nanoflower serving as a promising electrode material for a nonenzymatic glucose biosensor shows higher sensitivity and excellent selectivity. The findings reveal that the different CuxMy(OH)z (M = acidic radical) precursors synthesized in a water/ethanol reaction environment can be utilized to obtain new forms of CuO nanomaterials, and this unique water-dependent precursor-transformation method may be used to effectively control the growth of other metal oxide nanostructures.

A surfactant-free strategy for controllable growth of various hierarchical CuO nanostructures was successfully achieved through a facile, one-pot solution-phase transformation of CuxMy(OH)z (M = SO42−, Cl−, NO3− and CH3COO−) precursors method without extra heat treatment in air. The formation of CuO nanostructures here is essentially determined by the species of CuxMy(OH)z precursors. The nanoparticle aggregation with controllable shapes can be formed under different concentrations of reactants. Hierarchical CuO nanoflowers with different branched building blocks were prepared by the transformation of Cu4(SO4)(OH)6 precursors. Hierarchical CuO nanospindles and nanoplates were fabricated by the transformation of Cu2(OH)3NO3 precursors. Hierarchical CuO nanoplate assemblies and nanoplates were synthesized by the transformation of Cu7Cl4(OH)10H2O and C8H6Cu3O104H2O precursors, respectively. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). This study is of great importance in controllable synthesis of surfactant-free CuO nanostructures, because it not only enriches the family of CuO architectures but also offers a good chance to understand the nature of the solution-phase precursor transformation method for synthesizing CuO nanostructures. Significantly, it is believed that this surfactant-free solution-phase precursor-driven synthesis of nanostructures presented here might provide a green approach to design and growth other well-defined metal oxide nanostructures.

Hierarchically polyhedral (octahedral and cubic) Cu7S4 hollow cages have been synthesized by an ethanol-assisted sacrificial Cu2O template approach. The above two Cu7S4 cages were assembled from nanotwinned building blocks. When evaluated for their photocatalytic performances, these cages manifest structure-dependent properties. A higher amount of nanotwinned building blocks would be formed in original octahedral templates, so such an octahedral Cu7S4 microcage serving as a photocatalyst shows better performance than that of the cubic one. This highly active twinned structure concept might be used in the design and synthesis of functional nanostructures with improved physical and chemical properties.

We have demonstrated a facile strategy for synthesizing hierarchical CuO nanourchins (<300 nm) made from nanopetal building blocks by using a Cu2O-templated oxidative method. These hierarchical CuO nanourchins can serve as a promising electrode material and display an excellent response to glucose in comparison to interfering agents that normally co-exist in solution (such as ascorbic acid, uric acid and sodium chloride). The linear detection range is estimated to be from 50 μM to 5 mM at +0.57 V vs. Ag/AgCl (correlation coefficient = 0.9996), and the sensitivity is 1634 μA mM−1 cm−2. The as-prepared hierarchical CuO nanourchins open up a new avenue for exploring the synthesis of highly sensitive CuO nanostructures for potential applications in the field of enzyme-free amperometric sensing of glucose. Significantly, it is anticipated that different nanostructured Cu2O templates can be utilized to synthesize new forms of CuO nanomaterial.

Properties of natural fiber vary with its growth conditions even with different parts of the fiber. The main objective of this work is to study the effect of the fragment height in the fiber stem (FHFS) on the mechanical properties of abaca fibers and their unidirectional composites. Abaca fibers were cut into sequent fragments, and their unidirectional epoxy composites were fabricated by means of a compression molding technique. Tensile tests of fibers as well as composites were conducted, followed by the physicochemical analysis such as morphology, density, chemical compounds, and crystal structure. The results showed that the tensile strength and Young’s modulus of abaca fiber greatly increased to the maximum at about 1.0 m from the bottom and then slightly decreased with the increasing FHFS. This can be attributed to the different physicochemical properties caused by FHFS. Different to fiber, the tensile strength of composites presented a remarkable decrease with increasing FHFS due to the different stochastic nature of fiber which is varied with FHFS.

We have systematically investigated the crystal-facet-dependent effect of polyhedral Cu2O microcrystals exposed with different-index facets on photodegradation of methyl orange, which provides the convincing evidence that the performance of catalysts can be enhanced by high-index facets tailoring.

We present the first evidence for the synthesis of nanotwinned polyhedral 26-facet Cu7S4 microcages enclosed within polycrystalline shells. The photocatalytic superiority of these cages is attributed to the presence of a larger number of nanotwinned building blocks, which exhibited higher adsorption ability and catalytic activity for enhancing photodegradation of methylene blue (MB) dye.

A facile additive-assisted complex-precursor solution method is demonstrated for one-pot assembly of well-defined hierarchical Cu2O nanospheres with tunable sizes and shapes. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). The formation mechanism of these hierarchical nanostructures was rationally proposed, which can be attributed to the synergic effect of nanoparticle-aggregation and ripening with facet-selective adsorption. Significantly, it is believed that the additive-driven assembly of hierarchical architectures reported here would provide a facile way to design other exciting metal oxide nanostructures with controllable sizes. The photocatalytic superiority and stability for the methyl orange (MO) photodegradation by the hierarchical Cu2O nanospheres could be attributed to their exposed high active facets, which would be quite feasibly used for application in the fields of photocatalytic hazard pollutants.

Unusual polyhedral 26-facet Cu7S4 cages wholly exposed with amazingly unique nanotwinned structures as building blocks were successfully synthesized via a facile ethanol-assisted sacrificial Cu2O templates approach. Furthermore, a solvent-controlled fabrication of polyhedral copper sulfides (Cu7S4 and CuS) with different stoichiometries and microstructures can be artificially achieved, which is determined by the intrinsic difference of the surface states of Cu2O templates. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). Stoichiometric-dependent characteristics were demonstrated in the UV–vis absorption investigations. The as-prepared Cu7S4 microcages exhibit higher photocatalytic activity for enhancing degradation of methylene blue, which might be attributed to their special nanotwinned building blocks. This study is of great importance in “bottom-up” assembly of unusual ordering hollow copper sulfides superstructures, but also offers a good opportunity to understand the fundamental significance of nanotwinned structures for their potential applications.

We have demonstrated a facile protocol for the synthesis of CuS cages wholly exposed with nanotwinned building blocks via a sacrificial Cu2O template solution route. The as-prepared CuS cages exhibit higher photocatalytic activity for enhancing degradation of methylene blue.

An unusual designated-tailoring on zone-axis preferential growth of surfactant-free ZnO mesocrystals with different features (shapes and sizes) was successfully achieved via an additive-free complex-precursor solution method. The formation of ZnO mesocrystals here is essentially determined by the characteristic of [Zn(OH)4]2– precursors, and an oriented nanoparicle aggregation with tailoring sizes and shapes can occur in different concentration of reactants at higher reaction temperature. Spindle-like ZnO mesocrystals with tunable sizes (along the c-axis direction) were synthesized by adjusting the concentration of hydroxyl ions, and peanut-like ZnO mesocrystals with controllable sizes (along the c-axis direction) and shapes (perpendicular c-axis direction) were prepared by tailoring the concentration of zinc ions. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). The study is of great significance in bottom-up assembly of controllable ordering architectures, and provides a good opportunity to understand the formation mechanism and fundamental significance of zone-axis preferential growth of ZnO mesocrystals. Significantly, it is believed that the precursor driven assembly of mesostructures reported here would provide a green way to design more and more surfactant-free metal oxide architectures with well-defined shapes.

Novel nanocube-aggregated cauliflower-like copper hierarchical 3D nanostructures were successfully synthesized by a facile electroless deposition method. The formation and evolution can be attributed to the synergic effect of aggregation and ripening mechanisms. Moreover, such nanostructures exhibit electrocatalytic activity in the electoreduction of oxygen.

A self-assembly process has been developed to artificially fabricate hierarchical Au architectures without adding any templates or directing agents via an external electric field assisted particle-mediated “bottom-up” assembling methodology. The investigation on the morphology evolution reveals that the parameters (including various growth times, applied potentials and concentrations of HAuCl4 solution) were critical to control the assembly of the hierarchical Au architectures. The appearance of these novel hierarchical Au architectures can be attributed to the OA and external electric field assisted ordering alignment mechanism. The obtained Au architectures are found to yield large surface enhanced Raman spectroscopy (SERS) enhancement factors for rhodamine 6G (R6G).

We have demonstrated a facile protocol for the synthesis of facet-selective growth of low-cost metal Cu nanoparticles on {111} facets of polyhedral 26-facet Cu2O architectures. The novel Cu–Cu2O heterogeneous architectures show better adsorption and photodegradation of methyl orange than those of the original Cu2O architectures.

We have demonstrated a facile protocol to artificially design and synthesize uniform and monodisperse urchin-like Cu2O architectures via a selective-etching growth route. The urchin-like Cu2O architectures exhibit higher photocatalytic activity for enhancing degradation of methyl orange.

We have demonstrated a facile strategy to artificially design and synthesize novel polyhedron-aggregated multi-facet Cu2O homogeneous structures via a seed-mediated solution method. The polyhedron-aggregated Cu2O homogeneous structures with high-index {522} facets exhibit higher photocatalytic activity for enhancing degradation of methyl orange.

An etching-limited branching growth mechanism has been elucidated during ethanol-assisted solution synthesis of octahedral Cu2O crystals, which is different from the conventional diffusion-limited aggregate and recent overpotential-limited branching mechanism. It provides an innovative approach for revealing the shape evolution from habit formation (octahedron) to branching growth (hexapod-like architecture) via adjusting the competition between preferential growth and selective oxidative etching, and displays a constructive model system for fundamental research of crystal growth and design.

Novel highly symmetric multi-faceted polyhedral Cu2O crystals enclosed by controllable high-index facets and different low-index facets have been synthesized via a template-free complex-precursor solution route. The formation and evolution of these polyhedral shapes can be attributed to the aggregation and ripening mechanism with face-selective adsorption. The appearance of these novel polyhedral architectures further enriches the current morphologies of Cu2O crystals, and might become useful for the fundamental study of crystals design.

In this paper, an HCuCl2 solution has been discovered for high-yield fabrication of paddy-like copper dendritic nanostructuresvia electroless deposition route. The morphology of the copper dendritic nanostructure is obviously better than that synthesized in CuCl2 aqueous solution under otherwise the same experimental conditions. The appearance of these novel paddy-like copper nanodendrites can be attributed to diffusion-limited aggregation and oriented attachment mechanism. The dendritic morphology can be tailored via physical field, such as thermal field and magnetic field. Significantly, the HCuCl2 solution reported in this work might provide a new way for the shape-controlled synthesis of metal copper or copper based alloy.

A facile solution route has been developed to synthesize nanoparticle-aggregated octahedral copper hierarchical nanostructures. The formation of these novel octahedral copper hierarchical nanostructures can be attributed to a gas bubbles assisted aggregation mechanism. Based on the shape evolution and corresponding growth mechanism, it is believed that more and more copper crystals with novel hierarchical nanostructures could be obtained.

We have demonstrated a facile protocol of synthesizing 1D-aligned Ag superstructures via a magnetic field driven assembly in a template-free electrodeposition, which could provide an innovative approach to design more and more novel superstructures.

This paper describes a method for patterning of continuous monolayer gold nanoparticle films to form circular morphology at the pentanol–water interface. Time-dependent coalescence process indicates that the sintering between nanoparticles is the main reason for inducing the shrinking and splitting of the continuous monolayer nanofilm to circular morphology. Such a shrinking process generates a large number of “nanogaps” on circular networks, which leads to about a ten-fold enhancement of Raman signals over that initial formed continuous nanofilm. The approach of sintering improved reconstructing the continuous nanofilm is important for the design of 2D nanostructures with some of excellent properties through self–assembly at interface.

In this paper, shape-controlled synthesis of well-defined truncated edge polyhedral Cu2O architectures, including truncated edge cubic and truncated edge octahedral Cu2O crystals with three pairs of {100} facets, four pairs of {111} facets, and six pairs of {110} facets, and {100} etched truncated edge cubic Cu2O crystals, were achieved via a facile template-free complex-precursor aqueous solution route. The growth process and mechanism of Cu2O crystals are discussed in detail. The appearance of various morphologies can be attributed to the selective oxidative etching and preferential growth on different facets of Cu2O crystals.

Ultrathin Pt-based PtM (M = Pd, Ru, Au, Fe) alloy nanowire networks could be facilely synthesized using a soft template formed by cetyltrimethylammonium bromide in a two-phase water−chloroform system. The as-synthesized Pt-based alloyed nanowires show the fcc crystal phase. They have an average diameter of ∼2.3 nm and form porous nanonetworks, which can be potentially used for a number of catalytic applications. It was found that PtRu alloy nanonetworks showed more efficient catalytic activity for the hydrogenation of azo bonds in methyl orange than that of PtPd, PtAu, and pure Pt.

Palladium membrane with porous structure was synthesized through self-assembly of Pd nanoparticles (NPs) at the interface between water and pentanol under ambient condition. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that the as-synthesized Pd membrane presented nano-network structure with very high porosity. The porous Pd membrane exhibited well electrocatalytic activity and high sensitivity toward nonenzymatic glucose oxidation. It might have a promising outlook in the applications for glucose sensor due to its facility in preparation and well properties.Graphical abstractResearch highlights▶ 3D structured Pd nano-networks with very high porosity can be obtained by interface self-assembly. ▶ Porosity can be well controlled by changing Pd concentrations. ▶ The membrane exhibited well electrocatalytic activity and high sensitivity toward nonenzymatic glucose oxidation.

Bimetallic Ag/Au nanoparticles (NPs) with alloyed and core–shell structures were synthesized at a low temperature (75 °C) from the preformed gold and silver NPs in aqueous solution. The transmission electron microscope (TEM) mapping images, as well as the evolution of UV/vis spectroscopy, revealed that both the digestive ripening and Ostwald ripening were responsible for the formation of above structures during the heating process. Higher Ag ratios led to the growth of silver shell on the surface of Ag/Au alloy core, while lower Ag ratios tended to the formation of alloy particles. Interparticle diffusion, ligands and chemical potential were presumed to play important roles in the formation of alloyed and core–shell bimetallic Ag/Au NPs.Graphical abstractResearch highlights▶ Bimetallic Ag/Au nanoparticles (NPs) with alloyed and core–shell structures can be synthesized at 75 °C from the preformed gold and silver NPs in aqueous solution. ▶ Both the digestive ripening and Ostwald ripening should be responsible for the formation of above structures. ▶ This method can be facilely scaled up for the bimetallic NPs synthesis.

 Vacuum arcs generated on nanocrystalline CuCr5 alloys were observed by a digital high-speed video camera. Experimental results show that nanosized Cr particles have strong influence on arc characteristics. The arcs are much more stable on nanocrystalline CuCr5 alloys and the chopping current is about 0.8 A, which is much lower than that on coarse crystalline CuCr5 alloys. Spots can directionally move a long distance on nanocrystalline CuCr alloy whereas the spot motion is totally random walk on Cr particles for coarse crystalline CuCr alloy.

For the first time, a facile, one-pot water/ethanol solution-phase transformation of Cu2(NO3)(OH)3 precursors into bicomponent CuO hierarchical nanoflowers is demonstrated by a sequential in situ dissolution–precipitation formation mechanism. The first stage produces a precursory crystal (monoclinic Cu2(NO3)(OH)3) that is transformed into monoclinic CuO nanoflowers during the following stage. Water is a required reactant, and the morphology-controlled growth of CuO nanostructures can be readily achieved by adjusting the volume ratio between water and ethanol. Such a bicomponent CuO hierarchical nanoflower serving as a promising electrode material for a nonenzymatic glucose biosensor shows higher sensitivity and excellent selectivity. The findings reveal that the different CuxMy(OH)z (M = acidic radical) precursors synthesized in a water/ethanol reaction environment can be utilized to obtain new forms of CuO nanomaterials, and this unique water-dependent precursor-transformation method may be used to effectively control the growth of other metal oxide nanostructures.

For the first time, one-pot solution-phase selective-etching to create cuboctahedral Cu2O crystals enclosed by both stepped {111} surfaces and smooth {100} surfaces has been demonstrated. Investigation of photocatalytic performances indicates that the stepped cuboctahedral Cu2O crystals have higher photocatalytic activities than those of the common smooth ones.

We have demonstrated significant evidence of a solvent-dependent synthesis of hierarchical Cu7S4 polycrystalline nanocage assemblies with controllable aggregation-based building blocks by a sacrificial Cu2O template approach. The formation of a hierarchical Cu7S4 polycrystalline nanocage is essentially determined by a Kirkendall effect, which is attributed to the tailored-aggregation behaviour of the nanoscale building blocks during the replacement/etching process in different polarities of solvent. The hierarchical Cu7S4 polycrystalline nanocage assembly of nanoparticle building blocks was prepared in pure water, while the hierarchical Cu7S4 polycrystalline nanocage assembly of twinned nanoplate building blocks was successfully synthesized in an anhydrous ethanol capping environment. Such a hierarchical Cu7S4 polycrystalline nanocage assembly of twinned nanoplate building blocks exhibits a higher photocatalytic activity than that of the common polycrystalline ones. A nanotwin-dependent photochemical mechanism has been proposed. Significantly, this study is of great importance in bottom-up assembly of controllable ordered architectures, and offers a good opportunity to understand the fundamental importance of the formation mechanism and growth process of hierarchical Cu7S4 polycrystalline nanocages with controllable aggregation-based building blocks.

Morphology is a primary part of designing metal nanocrystals and nanomaterials with controlled functional properties. Here, we demonstrate the potential of foreign sulfate ions to tune the silver dendrites to highly branched chains through a simple galvanic replacement reaction without introducing any organic surfactants. We further illustrate the underlying mechanism according to diffusion-limited aggregation (DLA) in the presence of sulfate ions. The special aspects of this simple synthetic strategy are the control of both the nucleation process and the subsequent crystal growth stage by using sulfate ions as the ionic surfactants thereby tuning the total surface energies on various crystal facets in solution and transforming crystal growth habits of the products. Moreover, the highly branched silver chains (HBSCs) with pure surfaces have been successfully employed as a Raman probe for surface-enhanced Raman spectroscopic analysis of rhodamine 6G (R6G). The particular morphology of those HBSCs also makes them find potential applications in biosensing, catalysis and optics.

Novel etched Cu2O cubes with exposed {110} facets are synthesized via an oxidative etching method at room temperature. The photocatalytic performance indicates that these architectures show higher photocatalytic activity than that of the normal Cu2O cubes in the degradation of methylene orange.

In this report, a novel type of a hollow CuO polyhedron-modified electrode for sensitive nonenzymatic glucose detection has been fabricated by a templating approach. The morphologies and structures were characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS). These results show that the as-prepared hollow CuO consists of numerous CuO nanoplates. The electrochemical performance for glucose detection was investigated by cyclic voltammetry and chronoamperometry. The hollow CuO polyhedron-modified electrode exhibits a high sensitivity of 1112 μA mM−1 cm−2 with a detection limit of 0.33 μM (S/N = 3) at +0.55 V, and the linear range is up to 4 mM. Moreover, the hollow CuO polyhedron-modified electrode is highly resistant to the interference from interfering species such as sodium chloride (NaCl), ascorbic acid (AA) and uric acid (UA). The hollow CuO polyhedron-modified electrode exhibits high sensitivity, low detection limit, good stability and fast response towards the oxidation of glucose; thus, it may be a promising nonenzymatic glucose sensor.

We have demonstrated a facile anion-assisted strategy for the synthesis of nanoparticle-aggregated CuO nanoellipsoids. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). The nanoparticle-aggregated CuO nanoellipsoids serve as a promising electrode material for a non-enzymatic glucose biosensor which shows high sensitivity, good reproducibility, a fast amperometric response and good selectivity. The study is of great importance in the bottom-up assembly of tunable ordered architectures, and offers a chance to understand the formation mechanism and fundamental significance of an anion-assisted strategy for the synthesis of metal oxides. Significantly, it is believed that the anion-assisted synthetic approach reported here could provide a facile way to design more novel metal oxide architectures with well-defined shapes.

Unusual polyhedral 26-facet Cu7S4 cages wholly exposed with amazingly unique nanotwinned structures as building blocks were successfully synthesized via a facile ethanol-assisted sacrificial Cu2O templates approach. Furthermore, a solvent-controlled fabrication of polyhedral copper sulfides (Cu7S4 and CuS) with different stoichiometries and microstructures can be artificially achieved, which is determined by the intrinsic difference of the surface states of Cu2O templates. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). Stoichiometric-dependent characteristics were demonstrated in the UV–vis absorption investigations. The as-prepared Cu7S4 microcages exhibit higher photocatalytic activity for enhancing degradation of methylene blue, which might be attributed to their special nanotwinned building blocks. This study is of great importance in “bottom-up” assembly of unusual ordering hollow copper sulfides superstructures, but also offers a good opportunity to understand the fundamental significance of nanotwinned structures for their potential applications.

The template-strategy is one of the most significant techniques for the controllable synthesis of hollow architectures with unique structures, morphologies and properties. In this review, we selectively summarize the general principles of the Cu2O-templated strategy for the synthesis of definable hollow architectures and cover the recent progress in this area. We elaborate on the use of low-cost Cu2O templates for synthesizing different types of hollow cages (including copper sulfide, metal oxide, and metal) categorized by their chemical reaction mechanisms, followed by the challenges and perspective on Cu2O-templated strategy and its potential future directions.

We present the first evidence for the synthesis of nanotwinned polyhedral 26-facet Cu7S4 microcages enclosed within polycrystalline shells. The photocatalytic superiority of these cages is attributed to the presence of a larger number of nanotwinned building blocks, which exhibited higher adsorption ability and catalytic activity for enhancing photodegradation of methylene blue (MB) dye.

We have systematically investigated the crystal-facet-dependent effect of polyhedral Cu2O microcrystals exposed with different-index facets on photodegradation of methyl orange, which provides the convincing evidence that the performance of catalysts can be enhanced by high-index facets tailoring.