Core-shell Nanocubes Research Articles

Strain-Enhanced Metallic Intermixing in Shape-Controlled Multilayered Core-Shell Nanostructures: Toward Shaped Intermetallics.

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd-Ni-Pt core-shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low-temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape-controlled multimetallic nanoparticles tailored to each potential application.

Environment-friendly synthesis of carbon-encapsulated SnO2 core-shell nanocubes as high-performance anode materials for lithium ion batteries

Rational design and fabrication of SnO2@C composites with tailored structures enables the advanced electrochemical behaviors for the next-generation lithium-ion batteries. Benefiting from the enhanced electronic conductivity and porous structure, the integrated composites deliver the high reversible capacity as well as the outstanding rate capability. A high discharge capacity of 745.7 mAh g−1 is achieved at 0.1 A g−1 after 150 cycles. The discharging capacity of 292.0 mAh g−1 is observed at the high rate of 2 A g−1. Remarkably, the negligible capacity degradation is discerned under low and high current density (100, 500 mA g−1) in long-term electrochemical stability test. Therefore, the novel structure design for carbon-encapsulated SnO2 makes it a promising strategy to fabricate more efficient anode materials for lithium-ion batteries.

The controlled fabrication of hierarchical CoS2@NiS2 core-shell nanocubes by utilizing prussian blue analogue for enhanced capacitive energy storage performance

In this project, for the first time we successfully develop an approach to fabricate a novel core-shell structure of CoPBA@Ni(OH)2, in which Ni(OH)2 nano-sheets covered on the surface of CoPBA nanocubes through in-situ etching and growing processes, furthermore, being sulfurized into its hierarchical porous structure of CoS2@NiS2. The CoS2@NiS2 composite as a high-performance surpercapacitor electrode has been demonstrated. It exhibits very high specific capacitance value of 1731.2 F g−1 at 1 A g−1, excellent rate performance of 83.5% retention at 10 A g−1 and cycle performance with 87.1% retention after 5000 cycles together with distinguished coulombic efficiency of around 100%. Kinetic analysis and electrochemical impedance spectroscopy (EIS) results reveal the related mechanism. Herein, prussian blue analogue (PBA) as central core with cubic skeleton displays some great advantages, (1) it can provide more efficient electron conduction path to reduce the resistance of composite, (2) it can effectively prevent the agglomeration of electroactive Ni(OH)2 as well as sulfurized CoS2@NiS2 composite, (3) it can reduce ion diffusion pathway with mesoporous structure and enlarged surface area, greatly improving cycle stability. Such synthetic strategy opens up a new avenue for the effective construction of core-shell structure based on PBA basement for promising supercapacitor application.

Photothermal and colorimetric dual mode detection of nanomolar ferric ions in environmental sample based on in situ generation of prussian blue nanoparticles

Iron ions play a key role in many physiological processes, which can provide feedback for the evaluation of biological systems and environmental processes. New strategies for portable determination of Fe3+ therefore are still in urgent need. Here, through an in situ generation of prussian blue nanoparticles (PB NPs) in aqueous solution, we developed a bimodal method for photothermal and colorimetric detection of Fe3+. The sensing mechanism is based on the effective oxidation etching of Au–Cu core-shell nanocubes induced by Fe3+, accompanied by the in situ generation of PB NPs. It can be attributed to the specific reaction between ferrous ions (Fe2+) from the reduction of Fe3+ and potassium ferricyanide (K3[Fe(CN)6]) in the reaction solution. The in situ produced PB NPs show distinct bare-eye-detectable readouts with highly sensitive colorimetric and photothermal responses and thus can be used for Fe3+ determination. Such colorimetric change signals of characteristic absorbance at 740 nm in the UV–vis spectra showed a sensitive response to Fe3+ with a LOD of 210 nM. Moreover, as a sensitive photothermal probe, PB NPs generated in our Fe3+-enabled reaction system also exhibited a sensitive response to Fe3+ with a LOD of 70 nM. In addition, the standard addition experiments demonstrate our photothermal and colorimetric probe has good applicability for Fe3+ detection in the river water sample. What’s more, the proposed strategy opens a new horizon for affordable detection of metal ions using a common thermometer, and therefore has a great potential for analytical chemistry and some important applications such as environmental monitoring, disease diagnostics and food analysis.

Ultrafast and sensitive colorimetric detection of ascorbic acid with Pd-Pt core-shell nanostructure as peroxidase mimic

In recent years, nanostructures with peroxidase-like properties (i.e. peroxidase mimics) have attracted special interest due to their low costs, decent stabilities, and high catalytic activities. Herein, we demonstrate the use of Pd-Pt core-shell nanocubes (NCs) as efficient peroxidase mimics to achieve rapid and sensitive colorimetric detection of ascorbic acid (AA, which is commonly known as vitamin C). The color signal generated by the Pd-Pt NCs catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 is quenched in presence of AA based on its antioxidant property. This colorimetric method attains a detection limit of 0.40 μM and a linear range of 0–15 μM, with good linearity. To the best of our knowledge, the method reported in this work presents the fastest AA detection among all the other reported colorimetric methods, with only a 3-min reaction time. Furthermore, this method features a simple procedure, cost-effectiveness, room temperature conditions and good stability.

Sensitive and reliable detection of deoxynivalenol mycotoxin in pig feed by surface enhanced Raman spectroscopy on silver nanocubes@polydopamine substrate.

Deoxynivalenol (DON) is one of the trichothecene mycotoxin, a frequent contaminant of pig feed. Surface-enhanced Raman spectroscopy (SERS) is a fast and ultrasensitive analytical tool for point-of-need applications to identify molecular fingerprint structures at low concentrations. However, the use of SERS for analyte detection with flexible and robust structures is still challenging. Herein, we have developed core-shell silver nanocubes coated with polydopamine (Ag NCs@PDA) SERS substrate for the quantitative detection of deoxynivalenol in pig feed. The Ag NCs@PDA substrate with ultrathin (1.6nm) PDA shell thickness enhances the absorption of DON via hydrogen bonding and π-π stacking interactions, as well as improves the stability of the substrate. The results of the SERS showed a high analytical enhancement factor (AEF) of 1.82×107 and a detection limit (LOD) as low as femtomolar range (0.82fM). The LOD of the Ag NCs@PDA substrate for DON detection is 1.8 times lower than the bare Ag NCs. Furthermore, the Ag NCs@PDA substrate is stable which retains 88.24% of the original Raman intensity after storage for three months. The obtained results demonstrate that the Ag NCs@PDA substrates can realize label-free detection of deoxynivalenol mycotoxin with high sensitivity, reproducibility, and stability. Our work proposes a low-cost method for the designing of the SERS sensing device, and has great potential to be applied in food safety, biomedical sciences, and environmental monitoring.

Atomic-level insights into strain effect on p-nitrophenol reduction via Au@Pd core–shell nanocubes as an ideal platform

Tuning the surface strain of metallic nanocrystals represents a powerful strategy to engineer their catalytic properties by altering the electronic structures. However, a clear and systematic understanding of strain effect in catalytic reactions is still lacking, which restricts the use of surface strain as a tool to enhance the catalytic property of such nanocrystals. Here we use Au@Pd core–shell nanocubes and Pd nanocubes as a well-defined platform to study the strain effect in the reduction of p-nitrophenol by NaBH4. The Au@Pd core–shell nanocubes exhibited lower apparent activation energy than Pd nanocubes in the reduction of p-nitrophenol. The combination of molecular dynamic simulations and density functional theory calculations revealed that the tensile strain on Au@Pd core–shell nanocubes boosted the catalytic activity by shifting up the d-band center and thus strengthening the adsorption of p-nitrophenol.

Synthesis and high-resolution structural and chemical analysis of iron-manganese-oxide core-shell nanocubes

We have investigated the structure and chemical composition of nanoparticles synthesized by thermal decomposition of a mixture of iron oleate and manganese oleate in a high-boiling solvent in the presence of Na-oleate and oleic acid as surfactants by analytical transmission electron microscopy (TEM). The particles appear core-shell like in bright field TEM images. Higher spatial resolution TEM (HRTEM) analysis reveals a FeO/MnO like structure in the core and a spinel like structure in the shell. With high-resolution analytical methods like energy dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), the distribution of the metals Mn and Fe was investigated. Differences in the oxidation state of these metals were found between the core and the shell region. The presence of sodium from the used surfactant (Na-oleate) on the surface of the particles has been proved.

Well-aligned Cu@C nanocubes for highly efficient nonenzymatic glucose detection in human serum

Unique and well-aligned Cu@C core-shell nanocubes were rationally designed for nonenzymatic glucose detection using cubic Cu2O nanoparticles immerged in water-soluble polyvinyl pyrrolidone (PVP) coatings as precursor. As a consequence, the optimum Cu@C nanocubes with a shell thickness of ∼6.48 nm were prepared by the initial coating of Cu2O nanoparticles with 1.5 mg/mL PVP and subsequent annealing at 600 °C. After thermal annealing process, Cu2O nanoparticles were reduced to Cu nanocubes; at the same time, PVP was pyrolyzed to carbon shell encapulating the cubic Cu core. Due to efficient protection of the carbon shell of Cu core from oxidization and the advantageous inter-connected core-shell conductive networks, the hierarchical Cu@C nanocubes exhibit excellent electrocatalytic activity towards glucose oxidation. Under optimum condition, the resulted 600 °C annealed 1.5 mg/mL-Cu@C/Nafion modified glassy carbon electrode displayed high efficient nonenzymatic glucose detection, offering a wide linear range of 40 μM – 40 mM, with low detection limit at 21.35 μM (S/N = 3) and high sensitivity peak of 2565 μA mM–1 cm–2. More importantly, the well-designed Cu@C core-shell nanocubes could be utilized as a promising nonenzymatic sensor in practical biological applications for the detection of glucose concentration in human serum samples.

Synthesis of Cu2O@Cu-Fe-K Prussian Blue analogue core–shell nanocube for enhanced electroreduction of CO2 to multi-carbon products

Cu2O@Cu-Fe-K Prussian Blue analogue (K-PBA) core–shell nanocube was synthesized by a facile template-engaged redox deposition approach, and could be used as an efficient catalyst for CO2 electrochemical reduction (CO2ER). The presence of K-PBA shell not only can protect the Cu2O active core, but also promote the ratios of multi-carbon products to competing methane in CO2ER, achieving a total C2+ Faradaic efficiency (FE) of 23.9% (ethylene 10.8%, ethanol 3.6% and n-propanol 9.5%) at −1.11 V (vs. reversible hydrogen electrode (RHE), while jtotal = 6.2 mA cm−2. It is suggested that K-PBA shell coating alter inherent adsorption energetics of Cu2O, which contributes to the C–C coupling step in CO2ER.

Fe2O3@FeP core-shell nanocubes/C composites supported irregular PtP nanocrystals for enhanced catalytic methanol oxidation

The construction of highly active Pt-based catalyst for methanol electrooxidation is still an ongoing challenge. Herein, irregular PtP nanocrystals with the length is around 7 nm supported on the Fe2O3@FeP/C composites consisting of Fe2O3@FeP core-shell nanocubes and carbon black particles are synthesized by an integrated hydrothermal, low temperature phosphidation and NaBH4 reduction process. TEM and EDS reveal that both the presence of phosphorus (P) and the mild Pt reduction method are play a critical role in constructing irregular PtP nanocrystals. Interestingly enough, the confinement effect of carbon particles on iron ions in the process of hydrothermal reaction leads to the generation of Fe-precursor nanocubes. Benefiting from the P can effectively modify the electronic state of the Pt surface, the strong interaction between special irregular PtP nanocrystals and the support surface as well as Fe2O3@FeP core-shell nanocubes for the enhanced activation and decomposition of H2O molecules, the as-prepared PtP-Fe2O3@FeP/C-8 h catalyst exhibits better anti-CO poisoning ability, stability and excellent catalytic activity for methanol oxidation. Specifically, the mass activity (831 mA mg−1Pt) of PtP-Fe2O3@FeP/C-8 h is 4.6- and 2.1-times greater than that of home-made Pt/C (Pt/C-H) (180 mA mg−1Pt) and commercial Pt/C (Pt/C-JM) (393 mA mg−1Pt) catalyst in acidic medium. At the same time, the mass activity of PtP-Fe2O3@FeP/C-8 h is as high as 3215 mA mg−1Pt, which is much higher than those of Pt/C-H (1298 mA mg−1Pt) and Pt/C-JM (1548 mA mg−1Pt) catalysts in alkaline medium. The present work provides a new entry points into the synthetic way for the irregular PtP nanocrystals and cheap co-catalytic species for methanol oxidation reaction (MOR).

Core-shell gold @silver hollow nanocubes for higher SERS enhancement and non-enzymatic biosensor

Here we report a simple low-cost method to produce surface-enhanced Raman scattering (SERS) substrates with improved efficiency and high sensitivity towards uric acid and ascorbic acid sensing using non-enzymatic amperometric electrochemical method. Trisoctahedral gold (Au) core-silver (Ag) shell cubical shaped nanoparticles were synthesized simply by varying the surfactant in the reaction medium, and afterwards we made them hollow by galvanic displacement reaction. Spherical core-shell nanoparticles (both solid and hollow) were also prepared to compare results with cubical one. We have performed transmission electron microscopy (TEM) studies to understand the morphology of these nanoparticles and UV–vis–NIR and Raman spectroscopy studies to understand optical properties. We have obtained a huge SERS enhancement (~109) for hollow Au@Ag nanocube using 4-mercapto benzoic acid (4-MBA) as analyte. Because of the very thin Ag shell wall, both core Au and shell Ag interacts with the incoming electromagnetic wave, and also due to the presence of multiple sharp edges and corners in both core and shell part of the nanoparticles there is a large enhancement of the electromagnetic field. We have performed cyclic voltammetry study using the nanoparticles as electrode to understand how interfacial charge transfer and electron accumulation is happening in between an electrode and electrolyte interface and we have obtained a very high current response for hollow core-shell nanocube due to more surface area. High current response with voltage enable us to use hollow core-shell nanocubes as non-enzymatic electrochemical sensor for sensing uric acid (UA) and ascorbic acid (AA). We found a good sensitivity (1.509 μAmM−1cm−2 and 209.027 μAmM−1cm−2 for UA and AA, respectively) and very low detection limit (0.36 μM and 0.019 μM for UA and AA, respectively) towards sensing, which allows us to use Au@Ag hollow nanocube as a good UA and AA sensors.

Metal–organic framework-derived Co3O4/CoFe2O4 double-shelled nanocubes for selective detection of sub-ppm-level formaldehyde

Constructing complex interior nanostructures by metal-organic framework (MOF)-assisted strategy have attracted tremendous attention in the field of material science. Herein, the Co3O4/CoFe2O4 double-shell nanocubes (CCFO DSNCs) were synthesized by a metal–organic framework (MOF) route. The approach included the formation of a zeolite imidazolate framework-67 (ZIF-67)/Co–Fe Prussian blue analogue (PBA) core–shell nanocubes (CSNCs) precursor and then transformation to CCFO DSNCs by thermal annealing in air. A series of techniques were employed in order to investigate the morphology and structure of the CCFO DSNCs. The gas sensing properties of CCFO DSNCs were studied systematically. The results showed that the CCFO1 DSNCs sensor showed a high response toward formaldehyde with fast response and recovery speeds, and low detection limit (300 ppb). The enhanced properties were attributed to the double-shell nanostructure and the heterojunction between Co3O4 and CoFe2O4.

Investigation of the localized surface plasmon resonance of Ag@SiO2 core-shell nanocubes and its application in high-performance blue organic light-emitting diodes

A blue organic light-emitting diode (OLED) with silica-coated silver nanocubes (Ag@SiO2 NCs) inserted at the hole transporting layer/emission layer interface is reported. The localized surface plasmon resonance (LSPR) properties of the Ag@SiO2 NCs were characterized by the measured absorption spectra, stable-stated and transient photoluminescence, and calculated dipole radiation power. The results suggest that the Ag NCs significantly improved the radiation intensity of the nearby excitons due to their sharp corners and edges, but had less impact on the radiation rate of the excitons. The exciton recombination zone in the blue OLED was confirmed by a group of devices with an ultra-thin yellow emission layer located at different places, which helped to figure out the distribution of the excitons around the Ag@SiO2 NCs and deeply understand the coupling between the excitons and the Ag@SiO2 NCs. In our blue OLED, an appropriate distance between the Ag NCs and the excitons was realized by the SiO2 coating layer and the exciton distribution, which greatly improved the energy transfer between the excitons and the Ag NCs. In addition, the LSPR enhanced electric field around the Ag@SiO2 NCs improved the carrier injection at the hole transporting layer/emission layer interface and increased the current density of the blue OLED. Finally, the blue OLED with a simple triple layer structure achieved a high current efficiency of 51.1 cd A−1.

Stable Pd@Cu Core–Shell Nanocubes with Finely Tuned Sizes for the Reduction of Nitroaromatics

This paper reports a seed-mediated growth of Pd@Cu core–shell nanocubes with controllable edge lengths from 49 to 103 nm in an aqueous system using cetyltrimethylammonium bromide (CTAB) capped Pd n...

An electrochemical sandwich immunosensor for cardiac troponin I by using nitrogen/sulfur co-doped graphene oxide modified with Au@Ag nanocubes as amplifiers.

A voltammetric sandwich immunoassay is described for the biomarker cardiac troponin I (cTnI). The gold nanocube-functionalized graphene oxide (AuNC/GO) is employed as a substrate to accelerate the electron transfer and to immobilize more primary antibodies. It also employs composite materials prepared from bimetallic gold/silver core-shell nanocubes and nitrogen and sulfur co-doped reduced graphene oxide as the signal amplifier. The introduction of N and S into GO enlarges the active surface and accelerates the electron transfer rate. Such unique characteristics render the material an effective support substrate to load more Au@AgNC and to immobilize an increasing number of second antibodies via Ag-N bonds. After specific binding with cTnI, the immunosensor was incubated in a labeled cTnI secondary antibody solution. The amperometric signal change is then measured at 0.34V (vs. SCE) using o-phenylenediamine and hydrogen peroxide as an electrochemical probe. Response is linear in theconcentration range from 100fg∙mL-1 to 250ng∙mL-1, and the detection limit is 33fg∙mL-1. Graphical abstract Schematic presentation of cardiac troponin I (cTnI) electrochemical immunosensor based on gold nanocube-functionalized graphene oxide (AuNC/GO) as substrate material, bimetallic gold/silver core-shell nanocubes and nitrogen and sulfur co-doped reduced graphene oxide (Au@AgNC/N, S-rGO) as signal amplifier, and hydrogen peroxide (H2O2) and o-phenylenediamine (o-PD) as redox probe.

Indepth Studies on Working Mechanism of Plasmon-Enhanced Inverted Perovskite Solar Cells Incorporated with Ag@SiO2 Core–Shell Nanocubes

Noble metal nanoparticles-induced localized surface plasmon resonance as a useful approach has been widely used in solar cells including perovskite solar cells (PSCs) to improve their light-harvesting. Herein, we synthesize Ag@SiO2 core–shell nanocubes and investigate their application in CH3NH3PbI3-based PSCs due to both the large local EM field induced by the nanocube with sharp corners and the effective avoidance of exciton/carrier recombination at the surfaces of Ag nanocubes via covering a ∼5 nm ultrathin SiO2 shell. Incorporating an appropriate concentration of Ag@SiO2 nanocubes into the CH3NH3PbI3 PSCs realizes a best-performing efficiency of 17.22% with an enhancement factor of 18.1%. Indepth studies on the plasmon-enhanced working mechanism of Ag@SiO2 nanocubes with UV–vis absorption spectra, steady-state and time-resolved transient photoluminescence, and electrochemical impedance spectroscopy characterizations eventually demonstrate both the increasing light harvesting and the improving charge transportation and extraction contribute to better performances of PSCs.

Direct Observation of Early Stages of Growth of Multilayered DNA-Templated Au-Pd-Au Core-Shell Nanoparticles in Liquid Phase.

We report here on direct observation of early stages of formation of multilayered bimetallic Au-Pd core-shell nanocubes and Au-Pd-Au core-shell nanostars in liquid phase using low-dose in situ scanning transmission electron microscopy (S/TEM) with the continuous flow fluid cell. The reduction of Pd and formation of Au-Pd core-shell is achieved through the flow of the reducing agent. Initial rapid growth of Pd on Au along <111> direction is followed by a slower rearrangement of Pd shell. We propose the mechanism for the DNA-directed shape transformation of Au-Pd core-shell nanocubes to adopt a nanostar-like morphology in the presence of T30 DNA and discuss the observed nanoparticle motion in the confined volume of the fluid cell. The growth of Au shell over Au-Pd nanocube is initiated at the vertices of the nanocubes, leading to the preferential growth of the {111} facets and resulting in formation of nanostar-like particles. While the core-shell nanostructures formed in a fluid cell in situ under the low-dose imaging conditions closely resemble those obtained in solution syntheses, the reaction kinetics in the fluid cell is affected by the radiolysis of liquid reagents induced by the electron beam, altering the rate-determining reaction steps. We discuss details of the growth processes and propose the reaction mechanism in liquid phase in situ.

Au@Cu Core–Shell Nanocubes with Controllable Sizes in the Range of 20–30 nm for Applications in Catalysis and Plasmonics

Predominantly covered by a single type of {100} facets, Cu nanocubes are attractive catalytic material toward reactions such as electrochemical reduction of CO2. Here we report a seed-mediated approach to the facile synthesis of Au@Cu core–shell nanocubes with hexadecylamine and Cl– serving as capping agents toward the {100} facets of Cu and glucose as a reducing agent. The large (12%) lattice mismatch between Cu and Au led to the localized epitaxial growth of Cu shells on the Au seeds and the formation of nanocubes with randomly distributed Au cores. Compared to the same synthesis in the absence of Au seeds, the reduction of Cu(II) ions was greatly accelerated in the presence of Au seeds because of the autocatalytic surface reduction. It was also found that the structure and morphology of the products were highly dependent on the concentration of Cu(II) precursor in the reaction solution. Nanoplates rather than nanocubes were obtained when the concentration of Cu(II) precursor was reduced down to a certain level. By variation of the reaction time and/or the amount of Au seeds, the size of the Au@Cu nanocubes could be tuned in a range of 20–30 nm. The as-synthesized core–shell nanocubes exhibited a strong localized surface plasmon resonance peak at 581 nm, and the resonance was dominated by absorption rather than scattering. It is expected that the Au@Cu nanocubes with uniform and controllable sizes will find use in a variety of applications such as plasmonics and catalysis.

Enhanced light harvesting and electron-hole separation for efficient photocatalytic hydrogen evolution over Cu7S4-enwrapped Cu2O nanocubes

P-type Cu2O is an advantageous photocatalyst as the appropriate bandgap structure and low-cost. However, poor photocatalytic and instability of such promising material is still a great challenge. Here the core-shell Cu7S4-coated Cu2O nanocubes (Cu2O/Cu7S4 NCs) were successfully synthesized by solution method coupled with anion exchange, and were firstly employed to hydrogen evolution reaction (HER). The resultant integrated structure of Cu2O/Cu7S4 NCs exhibited apparent improved photocatalytic hydrogen evolution activity compared with Cu2O photocatalyst. Particularly, Cu2O/Cu7S4 NCs had a high hydrogen production rate of 1689.00 μmol g−1 h−1 under full spectra irradiation with additive of Na2SO3, which was higher than that of Cu2O NCs with a factor of 1.71 times. Excellent synergistic effect of Cu2O and Cu7S4 can be responsible for the improved hydrogen evolution properties, namely, the presence of Cu7S4 with localized surface plasma resonance (LSPR) can promote the photogenerated electrons transfer from the Cu2O surface, prolong the photogenerated holes lifetime, accelerate the separation of photogenerated electrons and holes, and ameliorate the photoelectric properties of semiconductors. The in situ formed multifunctional Cu7S4 layer offers a promising avenue to design photocathodes rationally for photocatalytic water reduction.