•Uniform eccentric Ag@polypyrrole nanostructure was achieved via the reaction between AgNO3 and pyrrole.•Embedding ratio was proposed based on encapsulation degree of Ag into a polypyrrole sphere.•The embedding ratio was dependent on the interfacial tension between Ag, polypyrrole and solution.•Highly active mushroom-like Au/Ag-polypyrrole was obtained from galvanic replacement reaction between Ag@polypyrrole and HAuCl4.Eccentric encapsulation of silver by polypyrrole was realized via the direct redox reaction between AgNO3 and pyrrole in the presence of sodium dodecyl sulfate. A facile method based on the relative amount of the Ag embedded in the normalized PPy sphere was developed and utilized to compare the interface tension between Ag, PPy and the solution. Via the aid of the embedding ratio, the formation of the eccentric silver@polypyrrole (Ag@PPy) was investigated by a temporal process and tuning the surfactant concentration and reaction temperature. Furthermore, such a unique nanostructure allowed the manipulation on the Ag end to achieve mushroom-like Au/Ag-PPy via the galvanic replacement reaction between Ag and HAuCl4, which was also dependent on the embedding ratio. After generating the above later nanostructure, much more active sites were available and much better catalytic activity was achieved taking the reduction of 4-nitrophenol by NaBH4 as an example reaction.An embedding ratio of Ag into a normalized polypyrrole sphere was proposed for explanation on the generation of eccentric Ag@polypyrrole with different encapsulation degrees and mushroom-like Au/Ag-polypyrrole nanostructure was obtained with highly catalytic performance.Download high-res image (165KB)Download full-size image

We report multi-site nucleation and growth of Ag islands on colloidal Au nanoparticles. By modifying a single factor, a range of products from Janus nanoparticles to satellite nanostructures are obtained. The identification of these key factors reveals the correlation between the concentration gradient and the choice of nucleation sites. In contrast to the inhibited homogeneous nucleation in the bulk solution, we argue that the non-steady-state concentration gradient plays a critical role in inhibiting nucleation within nanometer distance during the initial stage of growth—an essential but not yet recognized factor in colloidal synthesis. A depletion sphere model was developed, so that the multi-site nucleation is well integrated with the classic theory of nucleation and growth. Alternative explanations are carefully examined and ruled out. We believe that the synthetic know-how and the mechanistic insights can be broadly applied and are of importance to the advance of nanosynthesis.

•Hierarchical hollow nanostructured MnO2 is prepared via a facile route at room temperature in 10 min.•Polyaniline spheres are used as reactive templates to reduce KMnO4.•The hollow structure is obtained via establishing a diffusion/reaction rate equilibrium.•The MnO2 electrode and the asymmetric supercapacitor with activated carbon exhibit excellent electrochemical performance.Hierarchical hollow nanostructured MnO2 has been fabricated using polyaniline spheres as reactive templates. The reaction between KMnO4 and polyaniline leads to the reduction of KMnO4 into Mn2+ ions that are further oxidized by excessive KMnO4 into MnO2 layers. Meanwhile, the polyaniline cores are over-oxidized and diffuse into the solution to form the cavity. The ratio of the KMnO4 and polyaniline plays an important role in achieving the hollow structure via establishing a reasonable diffusion/reaction rate equilibrium. Owing to the unique nanostructure, the MnO2 electrode exhibits a specific capacitance of 308 F g−1 at a current density of 0.2 A g−1 and maintains 91% capacitance value after 3000 cycles at a current density of 2 A g−1. An asymmetric supercapacitor assembled by the hollow MnO2 and activated carbon presents energy densities of 20.93∼7.23 W h kg−1 under the power densities of 180∼9000 W kg−1 and 24% capacitance fading is detected after 2000 cycles at a current density of 4 A g−1.

•Activated multiporous carbon (AMC)@nickel cobalt sulfide nanostructure: self-assembly.•Analysis on sulfidation impact on structural and electrochemical change.•High specific capacitance of AMC@NiCo2S4: 651.1 F g−1 at 0.6 A g−1.•Good rate property of AMC@NiCo2S4: 88.1% retention.•Excellent cycling stability of AMC@NiCo2S4: 87.4% retention after 2000 cycles.A facile two-step hydrothermal method is modified to synthesize NiCo2S4 nanosheets on activated multiporous carbon (AMC) for application in supercapacitors. The structure and performance of both NiCo2S4 and the intermediate product, i.e. NiCo2O4 on AMC are investigated in detail to clarify the effect of the sulfidation treatment. Owing to the high electronic conductivity of NiCo2S4, the unique designed nanostructure exhibits a high specific capacitance (651.1 F g−1 at 0.6 A g−1), good rate performance (88.1% retention for current increases around 17 times) and excellent cycling stability (87.4% retention after 2000 cycles). These results suggest this hybrid composite to be a promising electrode material for high-performance supercapacitors and the rational fabrication provides an approach to improve the electrochemical energy storage for other transition metal sulfides and oxides.

•The Cu nanoparticles (NPs) anchoring on the nitrogen-doped carbon film (NCF) are achieved in one pot.•The CuNPs are highly dispersed on the surface of the NCF.•The urea benefits for enlarging the surface area of carbon film.•The Cu-NCF displays excellent catalytic performance.Highly dispersible copper nanoparticles (CuNPs) anchoring on the N-doped carbon films are achieved by pyrolyzing urea, citric acid and copper nitrate in one pot. The presence of the CuNPs and the N-doped carbon film is investigated by transmission electron microscopic, X-ray diffraction, X-ray photoelectron and Raman spectra. The citric acid is used as a carbon source to support the as-synthesized CuNPs and the urea takes a role as a nitrogen source to dope into the carbon structure and localize the CuNPs with a separated state. Such an N-doped carbon film with well-dispersed CuNPs on its surface presents an excellent catalytic performance and stability via using the reduction of 4-nitrophenol by NaBH4 as a model reaction.

Different nickel particle morphologies, including spheres, chains and urchins, were achieved in ethylene glycol solvent upon simply tuning both the amount of water and NaOH. The synthesis route was based on a routine solvothermal technique, in which nickel chloride and hydrazine hydrate were the nickel source and reductant, respectively. The shape transformation might be induced by an accelerated reaction rate and a change of the polarity of the solvent. Owing to the various morphology, these three kinds of nickel particles presented different catalytic performance. The reduction of 4-nitrophenol by NaBH4 as a typical catalytic model revealed that the urchin-like nickel particles behaved with the highest catalytic effect because of their unique structure with tips on the surface, which endowed much more active sites for the catalytic reaction. The good magnetic properties allowed these nickel particles to be readily recycled after application and they presented a much high cycling stability.

Correction for ‘Manipulating the nickel shape and catalytic performance: from spheres to chains to urchins’ by Lin Chen et al., CrystEngComm, 2015, 17, 4343–4348.

•Photo and temperature responsive amphiphilic diblock copolymer was successfully prepared.•The fluorescence of the polymeric assemblies could be efficiently modulated by a photochromic naphthopyran and temperature.•Such polymeric assemblies could be used as sensitive ratiometric fluorescent thermometers.A dual-responsive amphiphilic diblock copolymer, poly(styrene-co-1-(2-methacryloxyethoxy)-2-(2-pyridyl)benzimidazole)-block-Poly(N-isopropylacrylamide-co-3-biphenyl-3-phenyl-8-methacryloxy-3H-naphtho[2,1-b]pyran-co-4-methamino-9-allyl-1,8-naphthalimide), also denoted as P(St-co-PBI)-b-P(NIPAM-co-NP-co-MANI), was synthesized by reversible addition fragmentation chain transfer polymerization followed by assembling into micelles with hydrophobic P(St-co-PBI) block as core and thermoresponsive P(NIPAM-co-NP-co-MANI) block as the shell in aqueous solution. Dynamic light scattering, transmission electron microscopy and optical transmittance were used to characterize the particle morphology and thermosensitivity of the micelles solution. In addition, the fluorescence emission of the micelles could be reversibly modulated “on” and “off” by the photochromic naphthopyran upon UV and thermal back reaction, which promoted naphthopyran transformation between merocyanine forms and original closed form. Moreover, the spatial distance between the two fluorescence dyes could be regulated by temperature, resulting from the collapse or extension of PNIPAM in aqueous solution. This property enabled the polymeric assemblies to serve as sensitive ratiometric fluorescent thermometers.

The polymerization of aniline was realized in a confined space by using CeO2 nanoparticles as reactive templates that were encapsulated by SiO2. The weak solubility of CeO2 in acidic solution, resulting in the slow release of Ce4+ ions with a high oxidizing potential, and the porous structure of the SiO2 shell allowed an equilibrium to be established between the diffusion of aniline inward and Ce4+ ions outward from the shell, and the polymerization of aniline in the cavity. The influence of the shell thickness, reaction temperature and aniline concentration on the generation of the yolk–shell nanostructures was investigated in detail. By virtue of the excellent photothermal property of polyaniline that was confined in the SiO2 shell, the product was applied in drug loading and photothermal release using 5-fluorouracil as a representative anticancer drug.

It is of great importance to prevent catalysts from aggregating in order to maintain their high activity and stability for various applications. Based on a typical sacrificed SiO2 template route, gold nanoparticles (AuNPs) stabilized on an Fe3O4@SiO2 surface were anchored onto the inner layer of a polyaniline (PANI) shell, endowing a protection effect to avoid direct contact with the aiming molecules. The existence of the Fe3O4 core allowed the facile recycling of the catalysts from the reaction system. Compared to the sample without the protection of the PANI shell, Fe3O4@Au–PANI presented a much higher catalytic stability using the reduction of 4-nitrophenol by NaBH4 as a model reaction.

A fast reaction between zinc acetate and hexamethylenetetramine was carried out to produce peanut-shaped ZnO–Ag heterostructures in ethylene glycol/water mixed solvent using Ag nanoparticles as seeds and polyvinylpyrrolidone as surfactant. The Ag nanoparticles were well-dispersed on the ZnO particles, providing them with better photocatalytic performance in the decomposition of methylene blue than the pure ZnO. Furthermore, the introduction of a layer of polypyrrole coating on the ZnO–Ag surface enhanced the catalytic activity in two ways. On one hand, polypyrrole could protect the Ag from oxidation and being lost under both UV irradiation and visible light. On the other hand, polypyrrole could prominently increase the absorption of photons under the visible light.

•NiO as active electrode material direct grows on nickel foam.•Hexamethylenetetramine is used as both alkaline solvent and complex agent.•The effect of nickel salts on the morphology and electrochemical performances was investigated.Uniform NiO hierarchical nanostructures assembled by NiO nanosheets have grown directly on nickel foam substrate via a mild hydrothermal reaction between nickel salts and hexamethylenetetramine (HMT), followed by a subsequent calcinations process. HMT was employed as both alkaline source and complex agent. Several kinds of nickel salts (NiSO4, Ni(NO3)2, NiCl2 or Ni(CH3COO)2) were introduced as nickel source to investigate their effect on the morphology and electrochemical performances of NiO nanostructure. Cyclic voltammetry and constant current charge–discharge measurement illustrated these NiO electrodes presented good electrochemical performance. Especially the electrode with NiSO4 as nickel source gave a maximum specific capacitance of 349 F g−1 at a current density of 0.25 A g−1, which was superior to others owing to the smaller particle size that provided more active sites to ensure sufficient Faradaic reaction.

Raspberry-like nanostructured aniline oligomers were synthesized by using copper acetate as an oxidant in the presence of p-phenylenediamine. The formation of raspberry-like nanostructures perhaps has originated from the assembly of smaller nanoparticles in order to decrease the total surface energy. The introduction of p-phenylenediamine accelerated the polymerization rate and was beneficial for the generation of nearly monodispersed aniline oligomers. A kinetic control process might exist in the preparation of raspberry-like aniline oligomers. Furthermore, versatile nanostructured aniline oligomers, including hollow and linked ones, could be achieved by further oxidation and by decreasing the pH. Compared with polyaniline spheres with smooth surface, the product showed superior adsorption–desorption properties.

Polypyrrole (PPy)–Ag composites have been directly deposited on a nickel foam via the redox reaction between pyrrole and silver nitrate. As a catalyst, the nickel foam was able to accelerate the redox reaction and lead to the formation of PPy–Ag composites, which shows a strong adhesive force to the substrate. The electrochemical properties of the PPy–Ag–nickel foam electrode were systematically investigated by using cyclic voltammetry, galvanostatic charge–discharge and cycle stability measurements in 0.5 M K2SO4 electrolyte. The redox performance properties, good charge–discharge stability and high specific capacitance of 493 F g−1 at a current density of 1 A g−1 demonstrated the appropriate application of the PPy–Ag–nickel foam electrode for the high energy density supercapacitors.

Four unusual isomorphous metal–organic frameworks, [M2(L1)(L2)2] (M = Co for 1, Mn for 2, Zn for 3, and Cd for 4), where H4L1 = tetrakis[4-(carboxyphenyl)-oxamethyl]methane acid and L2 = 4-tolyl-2,2′:6′,2″-terpyridine, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra, elemental analyses, powder X-ray diffraction, UV–vis absorption spectra, and optical energy gaps. In compounds 1–4, the metal atoms are linked by the L1 anions to yield a chain with a loop. Every loop of each chain is penetrated by two L2 ligand rods belonging to the two nearest chains, resulting in an unusual 1D → 2D interdigitated network. In the 2D interdigitated network, there exist weak π–π interactions between pyridyl groups of L2 ligands. If the π–π interactions are regarded as linkers, the 2D interdigitated network belongs to an uneven (3,4)-connected layer. Furthermore, each individual (3,4)-connected layer is polycatenated with an infinite number of other perpendicular layers, yielding an unusual 2D → 3D polycatenane framework. The luminescent properties of compounds 3 and 4 have been studied. In addition, compounds 1–4 exhibit photocatalytic activities for MB degradation under UV irradiation. Submicrometer fiber 1′ shows high photocatalytic efficiency for MB degradation with respect to its corresponding macroscaled crystalline 1.

Silver@polyaniline (Ag@PANI) nanofibers with length up to several micrometers were achieved through a simple “mix-and-wait” method, where silver nitrate was reduced by aniline in aqueous solution and Ag and PANI were produced simultaneously to form core-shell nanostructure in the absence of any other additives. A thermodynamic-controlled process was considered for the generation of the long fibers of Ag@PANI since the low oxidation ability of silver nitrate to aniline and low reactants concentrations preferred a slow reaction rate. Furthermore, after removing the polymer shell by incubating the Ag@PANI in N,N-dimethylformamide, the 1D Ag core structure kept unchanged and could be found application in surface-enhanced Raman scattering fields.Graphical abstractThe direct reaction between AgNO3 and aniline led to the well-defined silver@polyaniline nanofibers at room temperature and their application in surface-enhanced Raman scattering was investigated.Highlights► Silver@polyaniline nanofibers were obtained via reaction between AgNO3 and aniline. ► This reaction was carried out at room temperature without any additives. ► A thermodynamic-controlled process was considered for the nanofiber generation. ► Removing the polymer shell retained the well-defined 1D Ag cores. ► The 1D Ag nanostructure showed high surface-enhanced Raman scattering activity.

A category of gas sensing hollow core waveguide that was operated in near infrared was designed to solve their major obstacles in application including high scattering and high losses. An attenuated total reflection structure was developed by using MS theory and dynamic liquid phase processing. An explanation on how the loss was reduced by total reflectance was provided and a suitable thickness of Ag film by controlling the deposition time was achieved. The guide we designed had a simple structure, low loss and hence increased the sensitivity.

Using glucose and Ni(NO3)2 as precursors, the nickel oxide–carbon (NiO–C) composites are directly formed on the nickel foam by a one-pot hydrothermal method. The product presents a spherical morphology with the carbon component in the composite being a non-graphitic phase. The presence of NiO provides additional pseudo-capacitance for the electrode materials and the composites exhibit superior specific capacitance to the pure carbon materials formed on the nickel foam. Apart from that, compared with the nickel sheet substrate, the utilization of the nickel foam benefits for the achievement of higher performance and stability owing to its unique 3D structure. The highest specific capacitance for the NiO–C–nickel foam electrode of 265.3 F g−1 is obtained at a discharge current density of 0.25 A g−1.

The galvanic replacement reaction between Ag nanoparticles (NPs) and HAuCl4 followed by addition of ascorbic acid led to the formation of AuNPs sharing both urchin-like and hollow structures. The AgNPs took as sacrificial templates to guide the hollow structure and the intermediates provided rough surface and active sites for the further deposition of AuNPs, which originated from the reduction of excess HAuCl4 by ascorbic acid. These unique structured AuNPs presented excellent optical properties and great advantages in catalysis applications.

A facile route was introduced to generate uniform raspberry-like gold@polyaniline (AuNP@PANI) particles in the presence of sodium dodecylsulfate (SDS). The surfactant SDS played an important role in both generating a uniform structure and stabilizing these particles. Upon addition of low-molecular weight organics, the regulation on the gold architecture was realized from a compact to stretched configuration owing to the change of surface tension and a possible swell process. The catalytic activity of the raspberry-like AuNP@PANI was investigated using the reduction of 4-nitrophenol by NaBH4 and electrocatalytic oxidation of glucose as model reactions. It was found that the AuNP@PANI particles with the most stretched architecture presented the highest catalytic activity owing to their largest contact surface to the reactants.

Nanostructured β-Ni(OH)2 was synthesized on nickel foam substrate via a mild hydrothermal process in an aqueous solution containing only Ni(NO3)2 and NaOH. The reaction conditions including reaction time and reaction temperature played crucial roles in the construction of different morphological Ni(OH)2 nanostructures. Cyclic voltammetry and constant current charge–discharge measurements illustrated the good electrochemical performance of the Ni(OH)2 electrode, and it displayed a maximum specific capacitance as high as 1778 F g−1 at a current density of 2.5 A g−1.Graphical abstractHighlights► Nanostructured Ni(OH)2 as active electrode material directly grows on nickel foam. ► The 3D structured nickel foam benefits for the sufficient loading of Ni(OH)2. ► Surface reconstruction occurs depending on the reaction conditions. ► The Ni(OH)2 as electrode materials shows good electrochemical performance.

Binary nanoassembly was realized by mixinggold@polyaniline nanoparticles with diblock copolymers in the DMF/H2O system and the products present a controlled transformation from symmetrical shells into spatially distributed petal-like polymer shells on gold cores.

Polyaniline (PANI) nanofibers were prepared via a novel interfacial polymerization method. In this method, aniline dissolved in xylene that is immiscible to water was directly added into the aqueous solution of the oxidant under stirring. The polymerization was carried out at the interface formed between the organic liquid drops and the water. The morphology, structure and water-dispersity of the samples prepared under different conditions were investigated by the aid of TEM, SEM, FT-IR and UV–vis spectra. The conductivity of the samples was also measured through typical four-probe technique.

Polypyrrole (PPy)–Ag nanofiber composites were synthesized with one step by the redox reaction between silver nitrate and pyrrole monomer in dilute mixed cetyltrimethyammonium bromide (CTAB)/sodium dodecyl sulfate (SDS) aqueous solution. The morphology and structure of the resulting composites were investigated by SEM and TEM images, FT-IR, Raman and XRD spectra, respectively. The results showed a strong compound interaction existing between PPy nanofibers and Ag nanoparticles.

•Polyaniline confined in SiO2 shell was pyrolized into carbon.•The confined effect allowed the maintenance of well-dispersed nanostructure with mesopores.•The SiO2 protection and NaOH etching ensured the effective O doping into the carbon.•The sample presented good electrocatalytic activity and stability for oxygen reduction reaction.Based on the previous generation of yolk-shell nanostructured polyaniline@SiO2 particles, a confined carbonization process followed by etching the SiO2 layer is carried out to achieve carbon particles. The existence of the SiO2 shell helps to preserve the original well-dispersed morphology of the polyaniline that retains amounts of active sites for oxygen reduction reaction. Furthermore, the CeO2 oxidant and the SiO2 shell lead to the increased amount of oxygen existing in the product and the oxygen reduction reaction results show the well-maintained nanostructure with mesopores and the effective O doping benefit for achieving enhanced catalytic activity.Mesoporous carbons from pyrolizing and etching confined polyaniline@SiO2 demonstrated good oxygen reduction reaction activity, high stability and strong methanol tolerance.Figure optionsDownload full-size imageDownload high-quality image (151 K)Download as PowerPoint slide

Binary nanoassembly was realized by mixinggold@polyaniline nanoparticles with diblock copolymers in the DMF/H2O system and the products present a controlled transformation from symmetrical shells into spatially distributed petal-like polymer shells on gold cores.

We report multi-site nucleation and growth of Ag islands on colloidal Au nanoparticles. By modifying a single factor, a range of products from Janus nanoparticles to satellite nanostructures are obtained. The identification of these key factors reveals the correlation between the concentration gradient and the choice of nucleation sites. In contrast to the inhibited homogeneous nucleation in the bulk solution, we argue that the non-steady-state concentration gradient plays a critical role in inhibiting nucleation within nanometer distance during the initial stage of growth—an essential but not yet recognized factor in colloidal synthesis. A depletion sphere model was developed, so that the multi-site nucleation is well integrated with the classic theory of nucleation and growth. Alternative explanations are carefully examined and ruled out. We believe that the synthetic know-how and the mechanistic insights can be broadly applied and are of importance to the advance of nanosynthesis.