Colloidosome-based synthesis of a multifunctional nanostructure of silver and hollow iron oxide nanoparticles

Synthetic Approaches to Colloidal Nanocrystal Heterostructures Based on Metal and Metal-Oxide Materials

Composite inorganic nanoarchitectures, based on combinations of distinct materials, represent advanced solid-state constructs, where coexistence and synergistic interactions among nonhomologous optical, magnetic, chemical, and catalytic properties lay a basis for the engineering of enhanced or even unconventional functionalities. Such systems thus hold relevance for both theoretical and applied nanotechnology-based research in diverse areas, spanning optics, electronics, energy management, (photo)catalysis, biomedicine, and environmental remediation. Wet-chemical colloidal synthetic techniques have now been refined to the point of allowing the fabrication of solution free-standing and easily processable multicomponent nanocrystals with sophisticated modular heterostructure, built upon a programmed spatial distribution of the crystal phase, composition, and anchored surface moieties. Such last-generation breeds of nanocrystals are thus composed of nanoscale domains of different materials, assembled controllably into core/shell or heteromer-type configurations through bonding epitaxial heterojunctions. This review offers a critical overview of achievements made in the design and synthetic elaboration of colloidal nanocrystal heterostructures based on diverse associations of transition metals (with emphasis on plasmonic metals) and transition-metal oxides. Synthetic strategies, all leveraging on the basic seed-mediated approach, are described and discussed with reference to the most credited mechanisms underpinning regioselective heteroepitaxial deposition. The unique properties and advanced applications allowed by such brand-new nanomaterials are also mentioned.

Plasmonic Metallic Heteromeric Nanostructures

Binary, ternary, and other high-order plasmonic heteromers possess remarkable physical and chemical properties, enabling them to be used in numerous applications. The seed-mediated approach is one of the most promising and versatile routes to produce plasmonic heteromers. Selective growth of one or multiple domains on desired sites of noble metal, semiconductor, or magnetic seeds would form desired heteromeric nanostructures with multiple functionalities and synergistic effects. In this work, the challenges for the synthetic approaches are discussed with respect to tuning the thermodynamics, as well as the kinetic properties (e.g., pH, temperature, injection rate, among others). Then, plasmonic heteromers with their structure advantages displaying unique activities compared to other hybrid nanostructures (e.g., core-shell, alloy) are highlighted. Some of the main most recent applications of plasmonic heteromers are also presented. Finally, perspectives for further exploitation of plasmonic heteromers are demonstrated. The goal of this work is to provide the current know-how on the synthesis routes of plasmonic heteromers in a summarized manner, so as to achieve a better understanding of the resulting properties and to gain an improved control of their performances and extend their breadth of applications.

Symmetry-Breaking Synthesis of Multicomponent Nanoparticles

Multicomponent nanoparticles (MCNs) composed of disparate inorganic colloidal components have attracted great attention from researchers in both the academic and industrial community, because of their unique properties and diverse applications in energy conversion and storage; heterogeneous catalysis; optics and electronics; and biomedical imaging, diagnosis, and therapy. Compared with single-component nanoparticles (NPs), new or advanced properties of MCNs arise from the synergistic effect between their constituent components and the presence of nanoscale interfaces between distinct materials within the particles. Consequently, the spatial arrangement of nanoscale domains of MCNs becomes equally important in property or function control of MCNs as their size, shape, and composition, if not more. In particular, compositionally asymmetric MCNs may outperform their symmetric counterparts in many of their applications. To this end, the seed-mediated growth (SMG) method, which involves depositing a second material onto seed NPs, has been considered as the most common strategy for the synthesis of asymmetric MCNs with desired complexity. In this approach, the control of symmetry breaking during MCN growth is usually achieved by manipulating the growth kinetics or using seed NPs with asymmetric shapes or surfaces. Although great progress has been made in the past decade, there remains a challenge to control the shape, orientation and organization of colloidal components of MCNs with a high yield and reproducibility. Recently, several unconventional methods have been developed as an important addition to the synthetic toolbox for the production of complex MCNs that otherwise may not be readily attainable. This Account summarizes recent advancements on the development of unconventional synthetic strategies for breaking the growth symmetry in the synthesis of asymmetric MCNs. We start with a brief discussion of the achievements and limitations of the conventional strategies for symmetry breaking synthesis. In the subsequent section, we present three unconventional approaches toward symmetry-breaking synthesis of asymmetric MCNs, namely, surface-protected growth, interface-guided growth, and welding-induced synthesis. First, we discuss how commonly used soft agents (e.g., collapsed polymer) and hard agents (e.g., silica) can be asymmetrically coated on seed NPs to template the asymmetric growth of secondary material, generating a broad range of MCNs with complex architectures. The unique features and key factors of this surface-protected synthesis are discussed from the viewpoints of the surface chemistry of seed NPs. We further discuss the use of a solid/liquid or liquid/liquid interface to guide the synthesis of Janus or more complex MCNs through two general mechanisms; that is, selective blocking or impeding the access of precursors to one side of seed NPs and interfacial reaction-enabled generation of asymmetric seeds for further growth. Finally, we discuss a symmetry-breaking method beyond the SMG mechanism, directed welding of as-synthesized single-component NPs. Moreover, we discuss how the unique structural symmetry and compositional arrangement of these MCNs significantly alter the physical and chemical properties of MCNs, thus facilitating their performance in exemplary applications of photocatalysis and electrocatalysis. We finally conclude this Account with a summary of recent progress and our future perspective on the future challenges.

Regioselective surface encoding of nanoparticles for programmable self-assembly

Surface encoding of colloidal nanoparticles with DNA is fundamental for fields where recognition interaction is required, particularly controllable material self-assembly. However, regioselective surface encoding of nanoparticles is still challenging because of the difficulty associated with breaking the identical chemical environment on nanoparticle surfaces. Here we demonstrate the selective blocking of nanoparticle surfaces with a diblock copolymer (polystyrene-b-polyacrylic acid). By tuning the interfacial free energies of a ternary system involving the nanoparticles, solvent and copolymer, controllable accessibilities to the nanoparticles' surfaces are obtained. Through the modification of the polymer-free surface region with single-stranded DNA, regioselective and programmable surface encoding is realized. The resultant interparticle binding potential is selective and directional, allowing for an increased degree of complexity of potential self-assemblies. The versatility of this regioselective surface encoding strategy is demonstrated on various nanoparticles of isotropic or anisotropic shape and a total of 24 distinct complex nanoassemblies are fabricated.

Biofunctional magnetic hybrid nanomaterials for theranostic applications

Cancer is a major disease that seriously threatens human health and is a leading cause of human death. At present, the commonly used cancer treatment methods are surgical therapy, chemical drug therapy and radiation therapy (RT). However, these treatments all have their own shortcomings and cannot perfectly meet the needs of clinical diagnosis and treatment. It is of great significance to improve the diagnosis and treatment level, so that the curative effect and quality of life of tumor patients can be improved. The rapid development of nanotechnology has brought hope to the diagnosis and treatment of cancer and the appearance of biofunctional magnetic hybrid nanomaterials (MHNs) has provided a new possibilities for the integration of cancer diagnosis and treatment. As a promising research direction, the multifunctional nanoplatform integrates imaging diagnosis, drug therapy and drug delivery. Better treatment effects and fewer side effects can be achieved by optimizing materials to build stable, efficient, and safe MHNs with combined functions of multimodal imaging and various treatments. This review focuses on not only the research progress of MHNs but also their applications and development trend in the integration of cancer diagnosis and treatment. A description of the applications of MHN structure optimization for both magnetic resonance imaging-based multimodal diagnosis and cancer therapy is given. Furthermore, RT is introduced and the development of MHNs for diagnosis and treatment system is investigated.

Magnetic-Plasmonic Heterodimer Nanoparticles: Designing Contemporarily Features for Emerging Biomedical Diagnosis and Treatments

Magnetic-plasmonic heterodimer nanostructures synergistically present excellent magnetic and plasmonic characteristics in a unique platform as a multipurpose medium for recently invented biomedical applications, such as magnetic hyperthermia, photothermal therapy, drug delivery, bioimaging, and biosensing. In this review, we briefly outline the less-known aspects of heterodimers, including electronic composition, interfacial morphology, critical properties, and present concrete examples of recent progress in synthesis and applications. With a focus on emerging features and performance of heterodimers in biomedical applications, this review provides a comprehensive perspective of novel achievements and suggests a fruitful framework for future research.

Functional magnetic hybrid nanomaterials for biomedical diagnosis and treatment

Magnetic nanomaterials integrating supplemental functional materials are called magnetic hybrid nanomaterials (MHNs). Such MHNs have drawn increasing attention due to their biocompatibility and the potential applications either as alternative contrast enhancing agents or effective heat nanomediators in hyperthermia therapy. The joint function comes from the hybrid nanostructures. Hybrid nanostructures of different modification can be easily achieved owing to the large surface-area-to-volume ratio and sophisticated surface characteristic. In this focus article, we mainly discussed the design and synthesis of MHNs and their applications as multimodal imaging probes and therapy agents in biomedicine. These MHNs consisting magnetic nanomaterials with functional nanocomponents such as noble metal or isotopes could perform not only superparamagnetism but also features that can be adapted in, for example, enhancing computed tomography contrast modalities, positron emission tomography, and single-photon emission computed tomography. The combination of several techniques provides more comprehensive information by both synergizing the advantages, such as quantitative evaluation, higher sensitivity and spatial resolution, and mitigating the disadvantages. Such hybrid nanostructures could also provide a unique nanoplatform for enhanced medical tracing, magnetic field, and light-triggered hyperthermia. Moreover, potential advantages and opportunities will be achieved via a combination of diagnostic and therapeutic agents within a single platform, which is so-called 'theranostics.' We expect the combination of unique structural characteristics and integrated functions of multicomponent magnetic hybrid nanomaterials will attract increasing research interest and could lead to new opportunities in nanomedicine and nanobiotechnology. WIREs Nanomed Nanobiotechnol 2018, 10:e1476. doi: 10.1002/wnan.1476 This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices.

Nanostructured Co(ii)-based MOFs as promising anodes for advanced lithium storage

A novel kind of Co-containing metal–organic frameworks (Co-BTC MOFs) are firstly developed as anodes for LIBs with excellent electrochemical performance.

Interfaced heterogeneous nanodimers

Dimerization of different nanocomponents in single nanoparticles becomes interesting due to not only inheritance of properties of both components but also generation of new properties associated with strong coupling of the two components. As a class of emerging nanomaterials, interfaced heterogeneous nanodimers (IHNDs) are attracting more attentions in the field of materials research, in particular, nanoscience and nanotechnology. This review provides a timely and comprehensive overview on the general principles for the synthesis of IHNDs and typical examples of IHNDs made of various compositional combinations. The current challenges related to the synthesis and characterization of IHNDs are summarized at the end of the review and future research directions are also discussed.

Gold Nanoframes by Nonepitaxial Growth of Au on AgI Nanocrystals for Surface-Enhanced Raman Spectroscopy

Plasmonic noble metal nanoparticles with defined interior nanogaps are of great significance to surface-enhanced Raman spectroscopy (SERS) applications owing to the presence of intraparticle hotspots. In this contribution, we discovered site-selective nonepitaxial growth of Au on nonmetallic AgI nanocrystals, and on the basis of this observation, we designed an unconventional route to synthesize monometallic Au nanoframes that possess ∼7 nm of interior nanogaps and ∼23 nm of overall size by templating of small AgI nanocrystals. Chemical bonding between Au and the iodide-rich surface of the AgI nanocrystals was proposed to play a critical role in the nonepitaxial growth of the Au nanoframes against the AgI nanocrystals. The Au nanoframes obtained from this synthesis showed superior SERS activity in detecting molecules of interest in low concentrations owing to the presence of intraparticle hotspots in additional to the interparticle ones, benchmarking against Au nanospheres. This intriguing synthesis may open up new opportunities toward a variety of noble metal/semiconductor nanoconjugates for a broad range of applications such as synergistic catalysis.

Biomedical Applications of Magnetically Functionalized Organic/Inorganic Hybrid Nanofibers

Nanofibers are one-dimensional nanomaterial in fiber form with diameter less than 1 µm and an aspect ratio (length/diameter) larger than 100:1. Among the different types of nanoparticle-loaded nanofiber systems, nanofibers loaded with magnetic nanoparticles have gained much attention from biomedical scientists due to a synergistic effect obtained from the unique properties of both the nanofibers and magnetic nanoparticles. These magnetic nanoparticle-encapsulated or -embedded nanofiber systems can be used not only for imaging purposes but also for therapy. In this review, we focused on recent advances in nanofibers loaded with magnetic nanoparticles, their biomedical applications, and future trends in the application of these nanofibers.

Polysaccharide-Coated Magnetic Nanoparticles for Imaging and Gene Therapy

Today, nanotechnology plays a vital role in biomedical applications, especially for the diagnosis and treatment of various diseases. Among the many different types of fabricated nanoparticles, magnetic metal oxide nanoparticles stand out as unique and useful tools for biomedical applications, because of their imaging characteristics and therapeutic properties such as drug and gene carriers. Polymer-coated magnetic particles are currently of particular interest to investigators in the fields of nanobiomedicine and fundamental biomaterials. Theranostic magnetic nanoparticles that are encapsulated or coated with polymers not only exhibit imaging properties in response to stimuli, but also can efficiently deliver various drugs and therapeutic genes. Even though a large number of polymer-coated magnetic nanoparticles have been fabricated over the last decade, most of these have only been used for imaging purposes. The focus of this review is on polysaccharide-coated magnetic nanoparticles used for imaging and gene delivery.

Substrate-bound growth of Au-Pd diblock nanowire and hybrid nanorod-plate

We expand the scope of the previously developed Active Surface Growth mode for growing substrate-bound ultrathin Pd (d = 4 nm) and Ag nanowires (d = 30 nm) in aqueous solution under ambient conditions. Using Au nanorods as the seeds, selective growth at the contact line between the rod and the substrate eventually leads to an attached Pd nanoplate. The unique growth mode also allows sequential growth of different materials via a single seed, giving substrate-bound Au-Pd diblock nanowires. The new abilities to use seed shape to pre-define the active sites and to apply sequential growth open windows for new pathways to hybrid nanostructures.

Silver-modified nanosized ferroelectrics as a novel photocatalyst

Monodispersed ferroelectric BaTiO3 nanoparticles are synthesized as a model system to investigate the effect of ferroelectricity on a photocatalytic process. The results demonstrate that ferroelectricity can directly affect the photocatalytic activity due to promotion of the separation of photo-excited carriers by spontaneous polarization in ferroelectric materials. Moreover, Ag nanoparticles are attached on these BaTiO3 to further improve the photocatalytic property.

Synthesis of Pt dendritic nanocubes with enhanced catalytic properties

Pt dendritic nanocubes (DNCs) were successfully synthesized in oleylamine under a 1 bar H₂ atmosphere. The catalytic activity of Pt DNCs was much greater than conventional Pt nanoparticles (NPs) for methanol electrooxidation.

Facile synthesis of Au–Pt bimetallic nanocomplexes for direct oxidation of methanol and formic acid

Au–Pt bimetallic nanocomplexes were synthesized and the composition and morphology of the nanocomplexes could be easily controlled by a facile synthesis method.

Facile synthesis of Pt/Pd nanodendrites for the direct oxidation of methanol

The demand for clean and energy-efficient fuel cell systems requires electrocatalysts with greater activity and stability. Here, we report a facile wet-chemical approach for the synthesis of high-quality three-dimensional (3D) Pt/Pd bimetallic nanodendrites. The simple and unique process developed here used oleylamine as a reducing agent, and hydrogen gas to control the morphology. The as-prepared Pt/Pd nanodendrites were characterized by transmission electron microscopy, x-ray diffraction and energy dispersive x-ray spectroscopy, cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The nanodendrites showed superior electrocatalytic activity (609.565 mA mg(-1) Pt) for the oxidation of methanol compared with Pt nanoparticle electrocatalysts. This method could provide a general approach for the morphology-controlled synthesis of bimetallic Pt-based nanocatalysts, which are promising materials for applications in fuel cells.

Preparation of fluorine-doped, carbon-encapsulated hollow Fe3O4 spheres as an efficient anode material for Li-ion batteries

Herein we report the design and synthesis of fluorine-doped, carbon-encapsulated hollow Fe3O4 spheres (h-Fe3O4@C/F) through mild heating of polyvinylidene fluoride (PVDF)-coated hollow Fe3O4 spheres. The spheres exhibit enhanced cyclic and rate performances. The as-prepared h-Fe3O4@C/F shows significantly improved electrochemical performance, with high reversible capacities of over 930 mA h g(-1) at a rate of 0.1 C after 70 cycles, 800 mA h g(-1) at a rate of 0.5 C after 120 cycles and 620 mA h g(-1) at a rate of 1 C after 200 cycles. This improved lithium storage performance is mainly ascribed to the encapsulation of the spheres with fluorine-doped carbon, which not only improves the reaction kinetics and stability of the solid electrolyte interface film but also prevents aggregation and drastic volume change of the Fe3O4 particles. These spheres thus represent a promising anode material in lithium-ion battery applications.

Multiwalled functional colloidosomes made small and in large quantities via bulk emulsification

Colloidosomes are attractive microcarriers for encapsulation and controlled release. If their shell is composed of multiple layers of particles they are very robust against defects, which ensures a well-defined permeability. So far most capsules with multilayer particle shells could only be assembled using microfluidic emulsification, a technique that offers unparalleled encapsulation control but that is difficult to scale up for high material throughput. Here we propose a method that allows for high throughput assembly of multiwalled colloidosomes using double emulsion templates made in two simple bulk emulsification steps. Stabilization of the emulsion with interfacially adsorbed particles is key to enable control over the colloidosome architecture, which can display single or multiple internal compartments depending on the magnitude of the applied shear. In addition to the high throughput, our method also allows for the assembly of capsules with magnetically responsive shells and controllable release properties in a size range that has previously not been possible for multiwalled colloidosomes. The potential of such systems is illustrated by producing large quantities of multiwalled colloidosomes that are small enough to display Brownian motion in a fluid and that can be externally triggered to release molecular encapsulants on demand.

Facile synthesis of pseudo-peanut shaped hematite iron oxide nano-particles and their promising ethanol and formaldehyde sensing characteristics

Herein, pseudo-peanut shaped hematite iron oxide nano-particles are prepared through a facile cost effective wet chemical synthesis route.

Engineering nanointerfaces for nanocatalysis

We focus on recent advances in the delicate design of well-defined nanointerfaces to promote nanocatalysis towards renewable energy.

A hollow porous magnetic nanocarrier for efficient near-infrared light- and pH-controlled drug release

A NIR light and pH dual responsive nanocarrier was fabricated for anti-cancer drug delivery as well as MRI and fluorescence cell imaging.

Surface matters: enhanced bactericidal property of core-shell Ag-Fe2O3 nanostructures to their heteromer counterparts from one-pot synthesis

A facile one-pot synthesis of Ag@Fe2 O3 core-shell and Ag-Fe2 O3 heteromer nanoparticles is developed, and the core-shell nanoparticles show superior antibacterial properties compared to their heteromer counterparts and plain Ag nanoparticles. The mechanism for the increased efficiency is proposed to be due to the enhanced Ag ion release from the iron oxide shell-protected pristine Ag surface.

Porous carbon protected magnetite and silver hybrid nanoparticles: morphological control, recyclable catalysts, and multicolor cell imaging

A simple and facile synthetic strategy is developed to prepare a new class of multifunctional hybrid nanoparticles (NPs) that can integrate a magnetic core with silver nanocrystals embedded in porous carbon shell. The method involves a one-step solvothermal synthesis of Fe3O4@C template NPs with Fe3O4nanocrystals in the core protected by a porous carbon shell, followed by loading and in situ reduction of silver ions in the carbon shell in water at room temperature. The core-satellite and dumbbell-like nanostructures of the resulted Fe3O4@C-Ag hybrid NPs can be readily controlled by loading amount of silver ions. The hybrid NPs can efficiently catalyze the reduction reaction of organic dyes in water. The easy magnetic separation and high stability of the catalytically active silver nanocrystals embedded in the carbon shell enable the hybrid NPs to be recycled for reuse as catalysts. The hybrid NPs can also overcome cellular barriers to enter the intracellular region and light up the mouse melanoma B16F10 cells in multicolor modal, with no cytotoxicity. Such porous carbon protected Fe3O4@C-Ag hybrid NPs with controllable nanostructures and a combination of magnetic and noble metallic components have great potential for a broad range of applications in the catalytic industry and biomedical field.

Multifunctional superparamagnetic iron oxide nanoparticles: design, synthesis and biomedical photonic applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have shown great promise in biomedical applications. In this review, we summarize the recent advances in the design and fabrication of core-shell and hetero-structured SPIONs and further outline some exciting developments and progresses of these multifunctional SPIONs for diagnosis, multimodality imaging, therapy, and biophotonics.

New forms of superparamagnetic nanoparticles for biomedical applications

Magnetic nanoparticles (MNPs) based on iron oxide, especially magnetite (Fe3O4), have been explored as sensitive probes for magnetic resonance imaging and therapeutic applications. Such application potentials plus the need to achieve high efficiency and sensitivity have motivated the search for new forms of superparamagnetic NPs with additional chemical and physical functionalities. This review summarizes the latest development of high moment MNPs, multifunctional MNPs, and porous hollow MNPs for biosensing, molecular imaging, and drug delivery applications.

Superparamagnetic Ag@Fe3O4 core-shell nanospheres: fabrication, characterization and application as reusable nanocatalysts

Superparamagnetic Ag@Fe(3)O(4) nanospheres with core-shell nanostructures have been prepared by a facile one-pot method. The diameter of the as-synthesized nanospheres was about 200 nm and the core sizes were between 50 and 100 nm. By varying the concentrations, particles with tunable core size and total size are successfully achieved. Time dependent experiments were constructed to investigate the synthesis mechanism, which indicated that the present method corresponded to an Ostwald ripening progress. The BET area of the core-shell nanospheres is about 22.6 m(2)/g and this result indicates that the product shows a porous character. The saturated magnetization of the superparamagnetic Ag@Fe(3)O(4) nanospheres is 27.4 emu g(-1) at room temperature, which enables them to be recycled from the solution by simply applying a small magnet. Due to the unique nanostructure, these particles show high performance in catalytic reduction of 4-nitrophenol and can be used as reusable nanocatalysts.

Preparation of functional magnetic nanocomposites and hybrid materials: recent progress and future directions

The aim of this article is to provide an overview of current research activities on functional, magnetic nanocomposite materials. After a brief introduction to general strategies for the synthesis of superparamagnetic nanoparticles (NPs), different concepts and state-of-the-art solution chemical methods for their integration into various types of functional, magnetic nanocomposite materials will be reviewed. The focus is on functional materials which are based on discrete magnetic NPs, including multicomponent nanostructures, colloidal nanocrystals, matrix-dispersed composite materials and mesoscaled particles. The review further outlines the magnetic, structural, and surface properties of the materials with regard to application.