Oriented-assembly of hollow FePt nanochains with tunable catalytic and magnetic properties

Carbon-Supported PdCu Alloy as Extraordinary Electrocatalysts for Methanol Electrooxidation in Alkaline Direct Methanol Fuel Cells

Palladium (Pd) nanostructures are highly active non-platinum anodic electrocatalysts in alkaline direct methanol fuel cells (DMFCs), and their electrocatalytic performance relies highly on their morphology and composition. This study reports the preparation, characterizations, and electrocatalytic properties of palladium-copper alloys loaded on the carbon support. XC-72 was used as a support, and hydrazine hydrate served as a reducing agent. Pd_xCu_y/XC-72 nanoalloy catalysts were prepared in a one-step chemical reduction process with different ratios of Pd and Cu. A range of analytical techniques was used to characterize the microstructure and electronic properties of the catalysts, including transmission electron microscopy (TEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma emission spectroscopy (ICP-OES). Benefiting from excellent electronic structure, Pd₃Cu₂/XC-72 achieves higher mass activity enhancement and improves durability for MOR. Considering the simple synthesis, excellent activity, and long-term stability, Pd_xCu_y/XC-72 anodic electrocatalysts will be highly promising in alkaline DMFCs.

Developing a dynamic magnetic flux template to guide 1D nanomaterial growth

A dynamic magnetic flux template (DMT) has been developed for preparing 1D nanomaterials efficiently. It can be quickly established and revoked without introducing any pollution. The DMT behaves like a template for guiding the orientation, bearing a 1D structure, activating the nucleation, and providing a driving force for 1D nanomaterial growth.

Hollow Multicomponent Capsules for Biomedical Applications: A Comprehensive Review

Hollow capsules with multi-shelled or multicomponent structures are essential materials for various applications. Biomedical applications like disease diagnosis, therapy, and monitoring have special significance as they aim to improve health conditions. This review demonstrated a comprehensive overview of hollow, multifunctional structures incorporating meaningful use of nanotechnology and its’ unique prospects in medicine such as patient-specific treatment, multimodal imaging, multimodal therapy, simultaneous delivery of drugs and imaging probes, and actively targeted delivery. The internal hollow cavity provides safe and controlled drug release while also enabling transport of functional moieties to target sites. This review explored the performance of different organic, inorganic, and metallic multicomponent capsules that have been reported for biomedical applications, mainly diagnostic imaging and drug delivery. Material compositions, morphologies, and synthesis strategies involved in fabricating such multifunctional systems have been discussed in detail. It is expected that with time, more sophisticated and precise systems will come to light as the outcome of ongoing concentrated research efforts.

1D Colloidal chains: recent progress from formation to emergent properties and applications

Integrating nanoscale building blocks of low dimensionality (0D; i.e., spheres) into higher dimensional structures endows them and their corresponding materials with emergent properties non-existent or only weakly existent in the individual building blocks. Constructing 1D chains, 2D arrays and 3D superlattices using nanoparticles and colloids therefore continues to be one of the grand goals in colloid and nanomaterial science. Amongst these higher order structures, 1D colloidal chains are of particular interest, as they possess unique anisotropic properties. In recent years, the most relevant advances in 1D colloidal chain research have been made in novel synthetic methodologies and applications. In this review, we first address a comprehensive description of the research progress concerning various synthetic strategies developed to construct 1D colloidal chains. Following this, we highlight the amplified and emergent properties of the resulting materials, originating from the assembly of the individual building blocks and their collective behavior, and discuss relevant applications in advanced materials. In the discussion of synthetic strategies, properties, and applications, particular attention will be paid to overarching concepts, fresh trends, and potential areas of future research. We believe that this comprehensive review will be a driver to guide the interdisciplinary field of 1D colloidal chains, where nanomaterial synthesis, self-assembly, physical property studies, and material applications meet, to a higher level, and open up new research opportunities at the interface of classical disciplines.

Biosensors and Bioanalytical Devices based on Magnetic Particles: A Review

Magnetic particles play an important role in current technology, and this field of technology extends to a broader progression. The term magnetic particles typically cover the paramagnetic particles and super-paramagnetic particles. Various materials like iron oxide are common, but other materials are available as well; a survey of such materials has been included in this work. They can serve for technological purposes like separation and isolation of chemical products or toxic waste, their use in the diagnosis of pathologies, drug delivery and other similar applications. In this review, biosensors, bioanalytical devices and bioassays, have been discussed. Materials for magnetic particles preparation, methods of assay, biosensors and bioassays working in stationary as well as flow-through arrangements are described here. A survey of actual literature has been provided as well.

One-dimensional hollow FePt nanochains: applications in hydrolysis of NaBH4 and structural stability under Ga+ ion irradiation

Pt-based one-dimensional hollow nanostructures are promising catalysts in fuel cells with excellent activity. Herein, one-dimensional hollow FePt nanochains were shown to be efficient nanocatalysts in the hydrolysis of NaBH₄. The characterization of composition, structure and morphology identifies an ultrathin shell (∼3 nm) with uniformly distributed Fe₃₀Pt₇₀ constituents. The H₂ generation rate of hollow Fe₃₀Pt₇₀ nanochains achieves 16.9 l/(min · g) at room temperature, while the activation energy is as low as 17.6 kJ mol^-1 based on the fitting over the whole reaction time span. After the catalysis of NaBH₄ hydrolysis, the morphology and composition of hollow FePt nanochains remain unchanged. Furthermore, the structural stability of hollow FePt nanochains under Ga⁺ ion irradiation is clarified. Theoretical simulation indicates that the stopping range of such a Fe₃₀Pt₇₀ shell is 7.7 keV, which offers a prediction that structure evolves diversely under Ga⁺ ions below and above such energy. The Ga⁺ ion irradiation experiments show a consistent trend with the simulation, where Ga⁺ ions with kinetic energy of 30 keV make the hollow architecture subside and sputter away, while Ga⁺ ions with kinetic energy of 5 keV only etch the top and lead to an eggshell structure.

In Situ SERS Detection of Photocatalytic Degradation of Aminothiophenol on Carbon-Nanotubes/CoPt Hollow Nanoparticles Composite

The phenol derivatives, as one kind of hormone, are analogous to endocrine disruptors with high carcinogenicity. The photocatalytic technology is an effective approach to mitigate environmental pollution by utilizing solar energy to degrade organic pollutants. In this work, CoPt hollow nanoparticles (NPs) attached to carbon nanotubes (CNTs) are employed to catalytically decompose the p-aminothiophenol (PATP) molecules under light irradiation, which is monitored by using surface-enhanced Raman scattering spectra. The effect of temperature on the catalytic efficacy of CoPt hollow NPs is investigated. Moreover, the use of CNTs coating on CoPt NPs is found to accelerate the photocatalytic degradation rate of PATP molecules, attributed to the enhanced plasmon-exciton coupling interaction of the CoPt/CNTs hybrid configuration.

Self-assembly of nickel: from nanoparticles to foils with tunable magnetic properties

Self-assembly of nickel from nanoparticles to nanowires and foils can be achieved by controlling the concentrations of sodium citrate during the electroless deposition process.

Nanostructure Optimization of Platinum-Based Nanomaterials for Catalytic Applications

Platinum-based nanomaterials have attracted much interest for their promising potentials in fields of energy-related and environmental catalysis. Designing and controlling the surface/interface structure of platinum-based nanomaterials at the atomic scale and understanding the structure-property relationship have great significance for optimizing the performances in practical catalytic applications. In this review, the strategies to obtain platinum-based catalysts with fantastic activity and great stability by composition regulation, shape control, three-dimension structure construction, and anchoring onto supports, are presented in detail. Moreover, the structure-property relationship of platinum-based nanomaterials are also exhibited, and a brief outlook are given on the challenges and possible solutions in future development of platinum-based nanomaterials towards catalytic reactions.

Low Pt Alloyed Nanostructures for Fuel Cells Catalysts

Low-noble metal electrocatalysts are attracting massive attention for anode and cathode reactions in fuel cells. Pt transition metal alloy nanostructures have demonstrated their advantages in high performance low-noble metal electrocatalysts due to synergy effects. The basic of designing this type of catalysts lies in understanding structure-performance correlation at the atom and electron level. Herein, design threads of highly active and durable Pt transition metal alloy nanocatalysts are summarized, with highlighting their synthetic realization. Microscopic and electron structure characterization methods and their prospects will be introduced. Recent progress will be discussed in high active and durable Pt transition metal alloy nanocatalysts towards oxygen reduction and methanol oxidation, with their structure-performance correlations illustrated. Lastly, an outlook will be given on promises and challenges in future developing of Pt transition metal alloy nanostructures towards fuel cells catalysis uses.

3D-2D heterostructure of PdRu/NiZn oxyphosphides with improved durability for electrocatalytic methanol and ethanol oxidation

The rational design and engineering of bimetallic Pd-based nanocatalysts with both high activity and durability are of paramount significance for the practical applications of fuel cells. Herein, a new class of well-defined 2D NiZn oxyphosphide nanosheets (NiZnP NSs) have been successfully engineered to support unique 3D PdRu nanoflowers (PdRu NFs) via a facile strategy. Such nanohybrids with abundant surface active areas and modified electronic structure exhibit a great enhancement in electrocatalytic activity for the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR), whose mass/specific activities are 1739.5 mA mg-1/4.5 mA cm-2 and 4719.8 mA mg-1/12.3 mA cm-2, which are 8.3/9.0 and 8.3/9.5 times higher than those of commercial Pd/C catalysts, respectively. More interestingly, with the remarkable promotional effect of NiZnP NSs, such 3D-2D PdRu/NiZn oxyphosphide nanohybrids can even retain 72.4% and 70.1% of initial catalytic activity toward MOR and EOR for 1000 potential cycles with negligible morphological or compositional variations. The successful construction of this new class of electrocatalysts opens up a new way for designing 3D-2D nanohybrids with high performance for electrochemical reactions and beyond.

Magnetic field modulated SERS enhancement of CoPt hollow nanoparticles with sizes below 10 nm

It is well known that Pt shows much weaker plasmonic effects in the visible spectrum when compared to Au, Ag and Cu. Therefore, the realization of efficient optical absorption by Pt nanoparticles with sizes below 10 nm in the visible spectrum remains a challenge. One possible way to enhance the optical absorption is to prepare Pt-based bimetallic magnetic nanoparticles. Furthermore, if an external magnetic field is applied, the synergistic effect of both electric and magnetic fields may provide sufficient SERS enhancement. In this paper, CoPt hollow nanoparticles (NPs) with sizes below 10 nm and ultrathin shells (∼2 nm) were synthesized in solution, at room temperature. The NPs have high surface-to-volume ratios and excellent structural stability. The hollow NPs exhibited enhanced light absorption characterized by surface-enhanced Raman scattering (SERS) with 4-mercaptobenzoic acid (4-MBA) as tip molecules. It is noted that the SERS enhancement of these alloyed NPs can be tuned by using an external magnetic field. A synergistic optical effect between these hollow NPs and the Ag film substrate is obtained. Hence, CoPt hollow NPs show promise as SERS substrates and potential for other applications in optical enhancement.

Unexpected compositional and structural modification of CoPt3 nanoparticles by extensive surface purification

We combined synchrotron small angle X-ray scattering, X-ray fluorescence and extended X-ray absorption fine structure spectroscopy to probe the structure of chemically synthesized CoPt3 nanoparticles (NPs) after ligand removal via the commonly accepted solvent/nonsolvent approach. We showed that the improved catalytic activity of extensively purified NPs could not be explained only in terms of a "cleaner" surface. We found that extensive surface purification results in the substantial leaching of the Co atoms from the chemically synthesized CoPt3 NPs transforming them into CoPt3/Pt core/shell structures with an unexpectedly thick (∼0.5 nm) Pt shell. We indicated that the improved catalytic activity of extensively purified NPs in octyne hydrogenation reaction can be explained by the formation of CoPt3/Pt core/shell structures. Also, we demonstrated that drastic compositional and structural transformation of water transferred CoPt3 NPs was rather a result of extensive removal of native ligands via a solvent/nonsolvent approach than leaching of cobalt atoms in aqueous media. We expect that these findings can be relevant to other transition metal based multicomponent NPs.

Precise Assembly of Particles for Zigzag or Linear Patterns

Precise control of particles assembly has tremendous potential for fabricating intricate structures and functional materials. However, it is still a challenge to achieve one-dimensional assembly with precisely controlled morphology. An effective strategy is reported to precisely assemble particles into well-defined patterns by liquid confinement through controlling the viscosity of the assembly system. It is found that high viscosity of the system impedes particles rearrangement and facilitates the generation of zigzag or twined zigzag assembly structures, while low viscosity of the system allows particles to rearrange into linear or zipper structures driven by lowering the surface deformation of the liquid. As a result, precise control of different assembly patterns can be achieved through tuning the viscosity of solvent and size confinement ratios. This facile approach shows generality for particles assembly of different sizes and materials.

One-Step Facile Synthesis of Highly Magnetic and Surface Functionalized Iron Oxide Nanorods for Biomarker-Targeted Applications

We report a one-step method for facile and sustainable synthesis of magnetic iron oxide nanorods (or IONRs) with mean lengths ranging from 25 to 50 nm and mean diameters ranging from 5 to 8 nm. The prepared IONRs are highly stable in aqueous media and can be surface functionalized for biomarker-targeted applications. This synthetic strategy involves the reaction of iron(III) acetylacetonate with polyethyleneimine in the presence of oleylamine and phenyl ether, followed by thermal decomposition. Importantly, the length and diameter as well as the aspect ratio of the prepared IONRs can be controlled by modulating the reaction parameters. We show that the resultant IONRs exhibit stronger magnetic properties compared to those of the widely used spherical iron oxide nanoparticles (IONPs) at the same iron content. The increased magnetic properties are dependent on the aspect ratio, with the magnetic saturation gradually increasing from 10 to 75 emu g^-1 when increasing length of the IONRs, 5 nm in diameter, from 25 to 50 nm. The magnetic resonance imaging (MRI) contrast-enhancing effect, as measured in terms of the transverse relaxivity, r₂, increased from 670.6 to 905.5 mM^-1 s^-1, when increasing the length from 25 to 50 nm. When applied to the immunomagnetic cell separation of the transferrin receptor (TfR)-overexpressed medulloblastoma cells using transferrin (Tf) as the targeting ligand, Tf-conjugated IONRs can capture 92 ± 3% of the targeted cells under a given condition (2.0 × 10⁴ cells/mL, 0.2 mg Fe/mL concentration of magnetic materials, and 2.5 min of incubation time) compared to only 37 ± 2% when using the spherical IONPs, and 14 ± 2% when using commercially available magnetic beads, significantly improving the efficiency of separating the targeted cells.

Surface and interface engineering of FePt/C nanocatalysts for electro-catalytic methanol oxidation: enhanced activity and durability

A methodology by coupling a microfluidic-batch process with in situ carbon-black mixing, successive annealing and de-alloying post-treatment was developed for engineering surface and interface microstructures of FePt/C nanocomposites. Ultra-small angular FePt nanocrystals rich in vertexes/terraces/steps and with Pt contents gradually increasing from the inner to the outer part can be synthesized at certain Fe/Pt atomic ratios (2/1 or 1.1/1), which can directly grow on carbon-black for enhanced nanocrystal-carbon interface interaction by introducing the in situ carbon-black mixing process. Composition and structure characterization suggests that FePt@(Fe_1-xPt_x)O_y(OH)_z/C nanocomposites with FePt alloy cores and surface Pt-doping hydroxyl iron oxide shells are formed after annealing. After controlled de-alloying of Fe in annealed nanocrystals with a Fe/Pt ratio of 2/1, the finally formed nanocatalysts exhibited excellent electrochemical catalytic performance using the methanol oxidation reaction as a model, preserving an activity of 1610 mA mg^-1 Pt^-1 (12 times the commercial Pt/C catalysts, higher than the best result (7.9 times the commercial Pt/C catalysts) just published in Science (Science, 2016, 354, 1410-1414), enhanced durability and high tolerance to CO poisoning.

Self-Stable WP/C Support with Excellent Cocatalytic Functionality for Pt: Enhanced Catalytic Activity and Durability for Methanol Electro-Oxidation

To endow catalyst support with excellent stability and cocatalytic activity toward methanol, oxidation reaction (MOR) is an effective way to strengthen the electrocatalytic activity of Pt-based catalysts. Tungsten phosphide/3D-corrugated porous carbon (WP/C) composite as Pt-support and cocatalyst for MOR is prepared via a synchronous synthesis method. Porous 3D-tufted structure and high surface area of WP/C with abundant oxygen-containing groups (such as C-O-C, C-O-H, or C-OH) can significantly improve the exposure of active sites, which enlarge the contact area with electrolyte and facilitate the mass transfer and absorption of methanol for promoting the MOR activity in acidic electrolyte. Pt-WP/C exhibits a considerably higher mass activity (1559.3 mA mg_Pt^-1) for MOR than that of Pt/C (488.2 mA mg_Pt^-1), owing to the special activity of W^δ+ and P^δ- sites for the decomposition reaction of water. With the introduction of W species, more available P species (passivated or not) are activated for further enhancing the cocatalytic activity of WP for MOR. Furthermore, the CO tolerance and durability of Pt-WP/C are also remarkable, which should benefit from the fast surface transport of adsorbed CO on different crystalline faces of WP and the extremely stable WP-C structure originating from the existence of P-P chains between the adjacent WP particles, respectively. The design of the porous structure and cocatalytic effect of this catalyst support (WP/C) provides a promising method to drastically enhance MOR activity.

Preparation of one-dimensional Fe3O4@P(MAA-DVB)–Pd(0) magnetic nanochains and application for rapid degradation of organic dyes

One dimensional (1D) magnetic Fe₃O₄@P(MAA-DVB)–Pd(0) nanochains are successfully prepared through distillation precipitation of methacrylic acid (MAA) and divinylbenzene (DVB) over Fe₃O₄ nanochains procured from magnetic-field-induction of hollow magnetic nanoparticles.