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In this article, we reported the electrochemical reduction of CO 2 at Cu–Ag bimetallic electrocatalysts, which can be facilely and reproducibly synthesized by hydrogen bubble template method and galvanic displacement reaction. An interesting finding was that the faradic yields of products can be tuned by changing the composition of the Ag component. The as-prepared catalyst can maintain higher activity and stability, especially the positively shifted potential to −0.74 V (vs. reversible hydrogen electrode) of detectable 14% C 2 products and suppression of H 2 for the Cu–Ag catalyst with the replacement time of 10 s. The synergistic effect of the catalyst has been reported to C 2 . In addition, the potential dependent rule for products was illustrated as well and volcano shape change towards C 2 was worthy to be pointed. Our research will deepen the understanding of the surface electrocatalytic reaction and provide the insight into the factors to design excellent catalysts.

A series of morphology/component-controllable Sn-Sb micro/nano-structures are fabricated by a one-pot replacement reaction technique employing metallic Sn as both template and reducing agent. Typically, nanoscaled Sn as template and ethyl alcohol as solvent give the hollow structure, while micron-sized Sn as precursor and ethylene glycol as solvent produce the dendritic product. Other mixed structures are also obtained by this one-pot route. As anode materials for lithium-ion batteries, the hollow or dendritic Sn-Sb materials exhibit higher discharge capacities compared with the corresponding Sb samples as well as the Sn templates. Especially, for the Sn-Sb hollow spheres, a high discharge capacity of 820.7 mAh g −1 after first cycle and a reversible capacity of 751 mAh g −1 are achieved after 100 cycles at a current density of 100 mA g −1 . Meanwhile, the hollow Sn-Sb structure delivers a specific capacity of 451.3 mA h g −1 at 500 mA g −1 after 150 cycles when used for sodium ion batteries. The superior electrochemical performance that are higher than many reported results can be attributed to the special morphology and structure, which can shorten the transportation distance of lithium/sodium ion and provide extra free space to buffer the volume expansion during the lithium/sodium insertion/extraction.

We report on Ni nanoparticles supported on boron nitride spheres (BNSP) and sheets (BNSH) as catalysts for hydrogen generation via hydrolysis of ammonia borane (NH 3 BH 3 , AB). The Ni/BN catalysts were prepared through a redox replacement reaction. The structure, morphology, and chemical composition of the obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectroscopy (EDX), and inductively coupled plasma emission spectroscopy (ICP). The characterization results showed that Ni nanoparticles were well dispersed on the BNSP and BNSH supports for the four Ni/BN catalysts prepared (Ni atomic contents of 6.8, 9.0, 9.2, and 12 wt%). The catalytic activity toward the hydrolysis of AB was found to correlate with the loading of the Ni/BN catalysts, which showed great cycle performance. Theoretical calculations revealed that BN sheets significantly influenced the electric character of Ni catalysts and thereby their catalytic properties.

A direct Z-scheme BiOI–CdS photocatalyst has been successfully synthesized by an electrostatic interaction mechanism and used for selective photoelectrochemical sensing of Cu2+. The BiOI–CdS photocatalyst shows higher photocatalytic activity and photoelectrochemical performance than pure CdS and BiOI. The photocurrent intensity generated by the BiOI–CdS-3 electrode is about 62 and 10 times of those induced by BiOI and CdS under visible-light irradiation, respectively. The enhanced photocatalytic activity is attributed to the formation of a hierarchical direct Z-scheme BiOI–CdS photocatalyst and its high Brunauer–Emmett–Teller (BET) specific surface area, which benefit the efficient spatial separation of charge and capture of visible-light. Moreover, a photoelectrochemical sensor is developed based on the selective replacement reaction between Cu2+ and CdS. The photoelectrochemical sensor is easily fabricated and presents good selectivity, acceptable detection range (0.1–100 μM) and detection limit (0.02 μM). It has been applied to the detection of Cu2+ ions in drinking water with a satisfactory result.

Sb nanoparticles encapsulated in 1-D N-doped porous carbon (denoted as Sb/NPC) have been fabricated by an in situ nanoconfined replacement reaction between SbCl3 and the intermediate Ni/NPC, in which Ni/NPC was obtained by annealing the hydrothermally synthesized nickel–nitrilotriacetic acid (Ni–NTA) precursor in an argon atmosphere. The Sb nanoparticles with a size of 10–20 nm were uniformly encapsulated in the 1-D N-doped porous carbon scaffolds. When the Sb/NPC composite was applied as an anode material in the batteries, it exhibited a high reversible capacity of 556 mA h g−1 at 200 mA g−1 after 100 cycles for Li-ion batteries (LIBs) and a reversible capacity of 400.9 mA h g−1 at 100 mA g−1 after 100 cycles for Na-ion batteries (NIBs). Such enhanced electrochemical performance of the designed Sb/NPC can be attributed to the synergistic effect between uniformly dispersed Sb nanoparticles and the 1-D N-doped porous carbon matrices.

We report a facile route for the successful synthesis of urchin-like Au nanocages via galvanic displacement reaction, which can be used as excellent SERS-active substrates.

Microscale and nanoscale magnetic objects can be driven and assembled in defined locations efficiently and rapidly in magnetic fields. In this study, we present a strategy to fabricate flexible electronic circuits using non-contact magnetic printing and a volume additive substitution reaction. The process involves assembling iron nanoparticles in designated fields in the magnetic field, thereby forming patterns of iron nanoparticles. Thereafter, the nanoparticles were fused together by converting the iron nanoparticles to silver through an Fe–Ag replacement reaction. A silver flexible electronic circuit was fabricated conveniently through this process. Using this approach, flexible electronic circuits with double-sided conductive patterns could be prepared. This method provides a general and highly effective approach to fabricate various conductive silver patterns on flexible materials, such as paper, PI, PET, and others.

We studied the initial stage of a Pt monolayer produced by surface-limited redox replacement (SLRR) using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). Different from the widely accepted understanding that a metallic monolayer island is formed, our XAFS showed that the Pt monolayer, initially present on the Au(111) substrate, was mainly in the form of a planar [PtCl4]2- complex with its molecular plane parallel to the Au(111). This result provides a new insight into the mechanism of SLRR.

1D Ag3PO4-NPs/Cu-NWs have been constructed to enhance visible-light-driven photocatalytic activity via biomimetic synthesis. Cu nanowires (NWs) were synthesized by a facile hydrothermal method. During the process of biomimetic synthesis, the porous PTFE film, which can mimic the transport process of cell membranes, plays an important role in controlling the transport speed of silver ions (Ag+) to decrease the reaction speed. Thus inhibition of the replacement reaction of Ag+/Cu and the uniform growth of Ag3PO4 nanoparticles (NPs) with a diameter of about 10 nm on Cu-NWs can be realized simultaneously. The diameter of Ag3PO4-NPs/Cu-NW is about 70 nm. Owing to the high electron transport of single crystal Cu-NWs, the free electrons in Ag3PO4 are transferred out to promote photogenerated electron–hole pair separation. The stability of Ag3PO4 NPs of the Ag3PO4-NPs/Cu-NWs was improved and the photodecomposition no longer occurred. Meanwhile, the band-gap of Ag3PO4 decreased to 2.07 eV after being coated on Cu-NWs and expanded the absorption scope of visible-light. In addition, the active species-trapping experiments indicated that the holes and ˙O2− play important roles in the photocatalytic reactions. The novel Ag3PO4-NPs/Cu-NWs were used for the degradation of ciprofloxacin (CPFX) for the first time and showed high photocatalytic degradation performance. After visible-light irradiation for 15 min, the degradation rates of CPFX with pure Ag3PO4 NPs and AC0.3 as catalysts were about 27% and 53%. In the end, the degradation efficiency of Ag3PO4-NPs/Cu-NWs was 6.07 times that of the pure Ag3PO4 NPs.

A facile, convenient, and mild method has been developed for large-scale synthesis of uniformly dispersed 2D six-pointed star-like gibbsite micro–nano crystals with lateral size around 2.5 μm and thickness around 100 nm, through a replacement reaction between Al powder and water. Investigation of the influence of solvent in a series allows for conclusion that replacing the reactant solvent water with ethylene glycol not only effectively moderates the reaction, but also benefits control of shape, crystal structure, and dispersibility. In contrast, besides decreasing the reaction speed, the same function cannot be attributed to another inorganic solvent candidate absolute ethanol. This conclusion was supported by XRD, FE-SEM, TEM, FT-IR, TGA and PSD measurements. Moreover, the band gap of as-prepared gibbsite powder in EG–H2O mixture is 5.78 eV, which is mainly attributed to its surface low coordinated O2−. Theoretically, scale-up of this simple synthetic procedure for large-scale production of gibbsite powder with high crystallinity and purity should be very easy.

In this work, we demonstrated facile and low-cost fabrication of highly sensitive SERS substrates via replacement reaction by immersing Cu foils into a AgNO 3 solution. Different morphologies of Ag nanostructures were observed on the substrate surface by controlling the reaction time. The growth mechanism of Ag nanostructures on the Cu substrates was also analyzed based on the nanostructure evolution. The Ag-Cu substrates showed optimum SERS enhancement at certain reaction time, and the minimum detected concentration of Rhodamine 6G is as low as 10 −13 M. The easy and low-cost fabrication makes the Ag-Cu SERS substrates promising for rapid, sensitive detection of targeted analytes, such as biomolecules, pollutants, and explosives in the environment.

Herein a rigid three-dimensional (3D) DNA "nanosafe-box" (DNB) for encapsulation and release of a recognition probe (N3) is designed to construct an electrochemical biosensor with the use of electroactive two-dimensional metal-organic framework (2D MOF) nanosheets as signal tags for ultrasensitive detection of mercury ion (Hg2+). Initially, N3 is locked in the 3D cavity of DNB by blocker DNA. After addition of target Hg2+, exonuclease III (Exo-III) digestion is initiated to the liberate DNA "key" (K); thereby, the free K triggers a strand displacement reaction for exposing the prelocked N3 to successfully ligate dibenzocyclooctyne (DBCO)-tagged anchor via metal-catalyst-free click chemistry, in which amounts of 2D MOF nanosheets containing Co(II) as electron mediator are introduced accompanied by significant electrochemical response. Compared with traditional linear or stem-loop DNA nanostructure, the well-designed 3D DNB possesses remarkably enhanced mechanical rigidity and structural stability, resulting in improved accessibility of probes and increased loading amounts of signal tags. More importantly, by this way of encapsulation and release of recognition probes, the background signal is decreased dramatically, leading to increased sensitivity of the proposed biosensor. Consequently, this electrochemical biosensor exhibits outstanding analytical performance for Hg2+ detection with a low detection limit of 33 fM and dynamic linear range of 0.1 pM to 10 nM. This strategy offers an ingenious method for detection of metal ions and biomarkers, possessing potential applications in environmental tests and clinical diagnosis.

A one-pot method based on cyclic voltammetric scan was used to fabricate a glassy carbon electrode modified with nanocomposites consisting of poly(thionine) and amino-functionalized graphene quantum dots (afGQDs). Under near-neutral conditions, the dye polymer was effectively oxidized by hydroxyl radicals (·OH) that were derived from the copper-catalyzed Fenton-like reaction, and the cathodic peak current on the modified electrode greatly increased. The reaction of Cu2+ with thiourea (TU) and the generation of a complex, CuTU2+, led to the decrease of Cu2+/Cu+ species, which inhibited the Fenton-like reaction and reduced the electrochemical response change. Due to a displacement reaction, the addition of Hg2+ into the H2O2-Cu2+-TU system resulted in the release of cuprous ions that benefited the Fenton-like reaction. Under the following optimal conditions: 6 mg mL−1 afGQDs and the 25-cycle potential cycling for the fabrication of the modified electrode, pH 6.5, and the $$ {c}_{{\mathrm{Cu}}^{2+}}/{c}_{\mathrm{TU}} $$ ratio of 1.0, the increasing extent of the cathodic peak current exhibited a good linear response to the logarithm of the Hg2+ concentration in the range of 1 pM–1 μM with a detection limit of 0.6 pM. Mercury ions in a water sample were determined with good recovery, ranging from 97 to 103%. The investigation on the uptake of Hg2+ into human vascular endothelial cells, HUVEC, shows that the cells incubated in the high-concentration glucose medium absorbed more mercury ions than HUVEC incubated in the normal medium. As a result, Hg2+ could lead to the greater damage to the former.

Synthesis of silver (Ag) nanoparticles with controllable morphology and with high purity remains challenging. In this work, single crystalline Ag nanoparticles with uniform morphology and high purity are successfully synthesized based on the replacement reaction between aqueous Ag nitrate (AgNO3) and solid copper (Cu) via jet. We further demonstrate that the developed jet method is facile and morphology-controllable. It is believed that diffusion limited aggregation and oriented attachment mechanisms are responsible for the formation of Ag nanostructures. The synthesized nanoparticles were characterized by different techniques. Finally, the Ag nanoparticles are successfully applied to prepare the conductive ink for flexible electronics and wearable equipment. Furthermore, the conductivity, flexibility and stability of the conductive material are measured. The conductive pattern exhibits lowest resistivity of 6.7 μΩ cm, showing the good conductivity of the prepared conductive material. In addition, the prepared conductive material is flexible in nature and exhibits stability over a long period.

A luminescent edge-interlocked heteroleptic metallocage based on Cu3(pyrazolate)3 was prepared through a ligand replacement reaction from a homoleptic metallocage and a new ligand. Its structure was confirmed by XRD and MALDI-TOF mass spectrometry. Theoretical calculations revealed the new ligand was evidently responsible for the bathochromic shift of the optimal excitation. This work provides a heteroleptic strategy to regulate the interlocking fashion and photophysical mechanism of metallocages based on Cu3(pyrazolate)3.

Metallic dendrites with uniform morphology, high purity, and large yield remain challenging to synthesize. In this work, single-crystalline silver (Ag) dendrites with uniform morphology, high purity, and large yield are successfully synthesized by employing single replacement reaction between aqueous silver nitrate (AgNO3) and solid copper (Cu) by jet. The combined effect of diffusion-limited aggregation and the locally oriented attachment of Ag particles is responsible for the formation of silver dendrites under nonequilibrium conditions. Finally, the potential applications of as-synthesized silver dendrites are demonstrated by successfully preparing silver-based conductive ink for flexible electronics and wearable equipment. The conductive pattern exhibits resistivity of 7.2 μΩ·cm, showing good conductivity of the prepared conductive material. This facile and time-efficient synthetic route can be extended to synthesize other noble metal nanostructures with desired morphologies by adopting selective precursor salt concentrations and substrate metals with proper redox potentials.

Because of its high theoretical volumetric capacity and dendrite-free stripping/plating of Mg, rechargeable magnesium batteries (RMBs) hold great promise for high energy density in consumer electronics. However, the lack of high-energy-density cathodes severely constrains their practical applications. Herein, for the first time, we report that a CuS cathode can fully reversibly work through a displacement reaction in CuS/Mg pouch cells at room temperature and provide a high capacity of ∼400 mA h/g in a MACC electrolyte, corresponding to the gravimetric and volumetric energy density of 608 W h/kg and1042 W h/L, respectively. Even after 80 cycles, CuS/Mg pouch cells can maintain a high capacity of 335 mA h/g. Detailed mechanistic studies reveal that CuS undergoes a displacement reaction route rather than a typical conversion mechanism. This work will provide a guide for more discovery of high-performance cathode candidates for RMBs.

In this paper, ultrasonic-enhanced replacement of lead by zinc in lead leaching solution was studied. The effects of reaction time, rotational speed, temperature, concentration of leaching solution and the ratio of the surface area of the zinc plate immersed in the leaching solution to the volume of leaching solution (S : V) were studied under both conventional and ultrasonic conditions. The optimum ultrasonic-assisted replacement conditions were as follows: the S : V of 0.04 (4 cm 2 100 ml −1 ), reaction temperature of 30°C, replacement time of 30 min and the concentration of leaching solution is 5 g l −1 , leading to a lead replacement rate of 94.84%. Compared with the conventional replacement process, the reaction time of ultrasonic-enhanced substitution could be reduced to one half, and the demand of reaction temperature, leaching solution concentration and other conditions were decreased accordingly. Introducing ultrasonic into the replacement reaction is promising to reduce the energy consumption in the hydrometallurgical industry also caters to the demands of environment protection.

The excessively high and inconsistent literature values for Km,Fe and Km,O2 prompted us to examine the iron oxidation kinetics in ferritin, the major iron storage protein in mammals, and to determine whether a traditional Michaelis–Menten enzymatic behavior is obeyed. The kinetics of Fe(ii) oxidation and mineralization catalyzed by three different types of ferritins (recombinant human homopolymer 24H, HuHF, human heteropolymer ∼21H:3L, HL, and horse spleen heteropolymer ∼3.3H:20.7L, HosF) were therefore studied under physiologically relevant O2 concentrations, but also in the presence of excess Fe(ii) and O2 concentrations. The observed iron oxidation kinetics exhibited two distinct phases (phase I and phase II), neither of which obeyed Michaelis–Menten kinetics. While phase I was very rapid and corresponded to the oxidation of approximately 2 Fe(ii) ions per H-subunit, phase II was much slower and varied linearly with the concentration of iron(ii) cations in solution, independent of the size of the iron core. Under low oxygen concentration close to physiological, the iron uptake kinetics revealed a Michaelis–Menten behavior with Km,O2 values in the low μM range (i.e. ∼1–2 μM range). Our experimental Km,O2 values are significantly lower than typical cellular oxygen concentration, indicating that iron oxidation and mineralization in ferritin should not be affected by the oxygenation level of cells, and should proceed even under hypoxic events. A kinetic model is proposed in which the inhibition of the protein’s activity is caused by bound iron(iii) cations at the ferroxidase center, with the rate limiting step corresponding to an exchange or a displacement reaction between incoming Fe(ii) cations and bound Fe(iii) cations.

Traditional electrochemical hydrogen peroxide (H2O2) assays all indispensably require the immobilization of enzyme or nanomaterials on electrode surface. These complex electrode surface modifications are laborious and time-consuming. To overcome such limitations, we developed here a facile homogeneous electrochemical biosensor based on displacement reaction for detection of intracellular and extracellular H2O2 produced by living cells. Methylene blue-labeled short single-stranded DNA strand (DNA-MB) was ingeniously designed as the reporter, which was adsorbed on CeO2 nanoparticles to result in low electrochemical signal. In the presence of H2O2, DNA-MB was released from CeO2 nanoparticles, leading to the significant enhancement of current signal. Therefore, a simple homogeneous electrochemical H2O2 assay is successfully achieved. This strategy also displays excellent anti-interference capability and reproducibility for H2O2 determination. More importantly, this method was capable of conveniently realizing intracellular and extracellular H2O2 assay. Thus, with the excellent merits of simplicity, rapidness, good repeatability, high specific and sensitivity, the proposed strategy has great potential to be applied in exploring the roles of H2O2 in physiological and pathological processes.

A wettable well was fabricated on an electrode, which was further modified with carbon quantum dot-scaffolded nanocomposites of melamine and copper for probing histidine through a unique displacement reaction route. The developed electrode with wettable well enables the condensing enrichment of analytes from the sample droplets, improving the electroanalytical sensitivity.

New MAX phases Ti2(AlxCu1-x)N and Nb2CuC were synthesized by A-site replacement by reacting Ti2AlN and Nb2AlC, respectively, with CuCl2 or CuI molten salt. X-ray diffraction, scanning electron microscopy, and atomically-resolved scanning transmission electron microscopy showed complete A-site replacement in Nb2AlC, which lead to formation of Nb2CuC. However, the replacement of Al in Ti2AlN phase was only close to complete at Ti2(Al0.1Cu0.9)N. Density-functional theory calculations corroborated the structural stability of Nb2CuC and Ti2CuN phases. Moreover, the calculated cleavage energy in these Cu-containing MAX phases are weaker than in their Al-containing counterparts, indicating that they are precursor candidates for MXene derivation., Comment: author name corrected

We have deposited gold (Au) thin film on silicon (Si) substrate by galvanic displacement reaction (GDR). After thin film (≈ 87 nm) deposition Si surface become very rough as observed by cross sectional transmission electron microscopy (XTEM). Rapid thermal annealing (RTA) at ambient atmosphere produces spherical shaped Au nanoparticles along with a number of endotaxial Au nanonarticle associated with each spherical one. However, normal annealing at ambient atmosphere at same temperature produces continuous film which is also associated with endotaxial particles.

The Palladium (Pd) nanoparticles were immobilized on the boron (B), nitrogen (N) doped porous carbon (BNC-50) through replacing cobalt path at room temperature, which was derived from the high-temperature pyrolysis of the modified Zeolitic Imidazolate Frameworks (ZIF) composes coated with 5-boronoisophthalic acid. The Pd nanoparticles could be uniformly dispersed on the BNC-50 supports by replacement reaction to effectively avoid the Pd nanoparticles agglomeration. Meanwhile, the B, N doping can further grapple the palladium nanoparticles with luxuriant activity sites during the loading process. The highly order carbon frameworks also offer more porous paths and interspace to enhance the mass and charge delivery. Therefore, the synthetic catalysis of palladium nanoparticles immobilized on the porous B, N-doped carbon displays excellent activity (Pd/BNC-50) for ethanol oxidation reaction (EOR). The catalytic activities of the Pd/BNC-50 with peak current density (2638.41 mA mg−1) are 3.77 times than that of Pd/C in the basic reaction solution.

The effect of Ag on cathodic activation and corrosion behaviour of Mg-Mn-Ag alloys are investigated in the present work. During corrosion, Mg-Ag intermetallic phase undergoes dealloying to form porous Ag-rich remnant whereas Ag in the alloy matrix is dissolved to form Ag+ ions that subsequently redeposit on the alloy surface via displacement reaction with Mg to form Ag nanoparticles, which lead to significant cathodic activation. The cathodic activation is a self-catalysed process since enhanced cathodic activity promotes anodic dissolution which, consequently, results in further enhancement of cathodic activity. Thus, the corrosion rate of Mg-2 Mn-4Ag alloy increases significantly with immersion time.

Through a replacement reaction approach, Ag nanostructure was easily prepared on economical digital video disc (DVD) and polydimethysiloxane (PDMS) with surface structure duplicating from the former. Distinct nanoscale morphology was observed, featuring intersecting Ag nanoplates with abundant hot spots on the DVD and spherical Ag nanoparticles on the PDMS. Surface-enhanced Raman scattering (SERS) spectra, using crystal violet as a probe, revealed a superior enhancement effect in Ag/DVD versus that in Ag/PDMS. Considering the desirable flexibility and transparency of PDMS for in situ detection, we further developed a protocol to introduce intersecting Ag nanoplates onto the PDMS surface. The resulting Ag/PDMS substrate was endowed with remarkable sensitivity, excellent uniformity and good stability under mechanical bending. Furthermore, effective in situ detection of malachite green on fish was demonstrated, highlighting the great potential of our approach for the in situ detection of target molecules on a curved surface.

To deal with the removal of PbO2 during the purification process of the Zn-containing rotary hearth furnace (RHF) dust, this study adopts a choline chloride-urea (ChCl-urea) based deep eutectic solvent system and water-washed Zn-containing RHF dust as the main target of investigations, preparing ZnO nanoparticles using a Zn-induced PbO2 removal and thermal treatment of the precursor. The effects of the mass ratio of Zn particles and Zn dust (maked as Zn particles - Zn dust), reaction temperature, and reaction time on the removal of PbO2 were also investigated. The ZnO nanoparticles and the PbO2-removed products were characterized by X-ray diffractometry, X-ray fluorescence spectroscopy, scanning and transmission electron microscopy. The results showed that the optimal conditions for efficient removal of PbO2 included the reaction temperature of 80 °C, The Zn particles - Zn dust is 1.6, with a reaction time of 3 h. The final product had a ZnO content of 98.332% with a particle size distribution in the range of 10–100 nm with an average diameter of 39 nm, belonging to the Category-II ZnO nanoparticles. The PbO2 removal mechanism mainly involved the dissolving of PbO2 in ChCl-urea, forming [Pb(ClO·urea)2]2−, and the replacement reaction between Zn particles and [Pb(ClO·urea)2]2−, producing metallic Pb and [ZnClO·urea]−.

The Ag/Ni(OH)2 composite has grown directly on Cu foam substrate via a modified galvanic displacement reaction between the mixed solution (AgNO3 and KBr) and Cu foam, followed by subsequent electrodeposition. Cu foam functions as a reducing agent and electrode substrate. The in situ growth strategy enables the active material to form a strong connection with the substrate, which is beneficial for the fast ionic/electronic transport and lowers the equivalent series resistance. On the other hand, the introduction of Ag improves the electrical conductivity of the material and increases the specific surface area, and even participates in the electrochemical reaction as an effective constituent. Such factors can significantly boost the electrochemical performances of the product, including a high specific capacitance of 1755[Formula: see text]F[Formula: see text]g[Formula: see text] at 2.5[Formula: see text]A[Formula: see text]g[Formula: see text] coupled with long-term cyclic stability at 83.87% (5000 cycles).

The propensity of Zn-metal anodes to form non-uniform or dendritic electrodeposits is bound up with the nature of the electrode surface. However, the effect of surface structure on the inherent nucleation and deposition of Zn is not yet well understood. Here, the surface structure of a Zn-metal anode is reconstructed with Sn-crystal textures via a facile chemical displacement reaction. Compared to the bare Zn, the high-affinity Zn binding sites of Sn afford lower deposition energy barrier, which promotes deposition kinetics. What is more, a Sn-textured surface with moderate Zn affinity but high average surface energy ensures a better wettability from the deposits, leading to the lateral growth of Zn crystals. The resultant Sn-textured Zn-metal anode exhibits an extremely low voltage hysteresis of 20 mV and achieves a prolonged cycling stability over 500 h cycles without dendrite formation. This work provides new insights into the crystal-texture-dependent Zn electrodeposition process and offers direction for direct surface texturing to better stabilize Zn-metal anodes with improved reversibility.

Kinds of β-diketiminato aluminum complexes, L1AlMe2 (1), L1AlMeI (2), L1AlI2 (3), L1AlBr2 (4), L2AlBr2 (5), L1AlCl2 (6), L2AlCl2 (7) (L1 [1] = [C(Ph)C(CH2)4C(NDip)2]-, L2 [2] = [PhC(PhCN-Dip)2]-, where Dip = 2,6-iPr2C6H3) were obtained from the reaction of trimethylaluminum, iodine, aluminum tribromide, KCl with the corresponding β-diketiminate or β-diketiminato aluminum complex, respectively. All compounds were characterized by 1H NMR and 13C NMR spectroscopy, single-crystal X-ray structural analysis, and elemental analysis. Compound 3 was found to be obtained from compound 1 or 2 with two or one equivalent of iodine, respectively. We found an intermediate, L1AlMe3 (8) in the process of that ligand formed compound 1 and separated its single crystal structure. In the process of reduction of β – diimidaluminium diiodide with potassium powder, we were surprised to find that the halogen replacement reaction can occur when β - diimidaluminium diiodide and KCl efficiently generate β – diimidaluminium dichloride.

Functional nanoporous metals and alloys can be fabricated by chemical or electrochemical dealloying routes in corrosive media, followed by customized surface functionalization. The present work describes how a combination of displacement reaction and dealloying can provide a facile one-pot procedure to nanoporous alloys such as PtAu, and the resulted electrocatalysts are characterized by highly dispersed Pt atoms or small clusters embedded within a high surface area Au matrix. These dilute alloy electrocatalysts with low Pt contents exhibit remarkable activity toward formic acid oxidation via a favorable dehydrogenation mechanism. At 0.6 V versus reversible hydrogen electrode, they can demonstrate over 70-fold enhancement in Pt mass activity than that of the commercial Pt/C.

The galvanic displacement reaction between sacrificial PbO2 layers and Fe(II) ions has been carried out in mildly acid acetate solutions. The effect of experimental variables, like morphology of the PbO2 layers, solution pH, temperature and concentration of Fe(II) ions, has been investigated by combining electrochemical methods, SEM-EDS, XRD and XPS. The reaction between PbO2 and Fe(II) ions produced secondary dual layers, consisting of an inner amorphous FeOOH film and an outer crystalline γ-FeOOH deposit, respectively. This peculiar behavior was in contrast with analogous reactions involving other transition metal ions, which yielded only continuous amorphous secondary oxide layers. PbO2/FeOOH layers were tested as anodes for the oxygen evolution reaction in basic media.

A scalable and binder-free Cu2Sb/Cu electrode has been synthesized via replacement reaction as an anode for sodium-ion batteries (SIBs). The thickness of Cu2Sb formed on Cu foil can be facilely tuned by adjusting the concentration of Sb3+ and reaction time. A high capacity of 318.4 mAh g–1 is obtained at 0.08 A g–1, and a capacity retention of 98.5% is also maintained after 200 cycles at 0.8 A g–1. The reaction mechanism of the as-synthesized Cu2Sb/Cu is investigated by using ex situ X-ray diffraction and transmission electron microscopy. The porous Cu2Sb nanoparticle film and its intrinsic contact with the Cu foil result in the good electrochemical performance. This facile synthetic route for the integrity of Cu2Sb nanoparticles and Cu foil allow for simplifying the preparation processes of SIBs in large-scale applications and is applicable for advanced material design and synthesis.

Pt decorated CoCu bimetallic nanoparticles (NPs) coated by silica (Pt-CoCu@SiO2) were synthesized for efficient catalytic hydrogen production from hydrolysis of ammonia–borane (NH3·BH3; AB). Initially, silica-coated CoCu bimetallic NPs (CoCu@SiO2) were prepared by a modified co-reduction method from reverse microemulsion. Further, Pt-CoCu@SiO2 was obtained by a facile spontaneous displacement reaction by using CoCu@SiO2 and H2PtCl6 as the starting materials. The catalytic activity of Pt on bimetallic support was compared to that of monometallic supports, i.e., Co and Cu. The results of catalytic experiments showed that the support of CoCu bimetal can significantly enhance the activity of Pt as compared to that of pure Cu or Co. An impressive turnover frequency (TOF) value of 272.8 molH2 molPt–1 min–1 was achieved at the hydrolysis temperature of 30 °C for Pt-CoCu@SiO2. The detailed formation process of catalysts was described, and the samples were characterized by TEM, STEM, XPS, EDS element mapping, etc.

Development of sodium-ion battery (SIB) electrode materials currently lags behind electrodes in commercial lithium-ion batteries (LIBs). However, in the long term, development of SIB components is a valuable goal. Their similar, but not identical, chemistries require careful identification of the underlying sodiation mechanism in SIBs. Here, we utilize in situ transmission electron microscopy to explore quite different sodiation behaviors even in similar electrode materials through real-time visualization of microstructure and phase evolution. Upon electrochemical sodiation, single-crystalline ZnO nanowires (sc-ZNWs) are found to undergo a step-by-step electrochemical displacement reaction, forming crystalline NaZn13 nanograins dispersed in a Na2O matrix. This process is characterized by a slowly propagating reaction front and the formation of heterogeneous interfaces inside the ZNWs due to non-uniform sodiation amorphization. In contrast, poly-crystalline ZNWs (pc-ZNWs) exhibited an ultrafast sodiation process, which can partly be ascribed to the availability of unobstructed ionic transport pathways among ZnO nanograins. Thus the reaction front and heterogeneous interfaces disappear. The in situ TEM results, supported by calculation of the ion diffusion coefficient, provide breakthrough insights into the dependence of ion diffusion kinetics on crystallization form. This points toward a goal of optimizing the microstructure of electrode materials in order to develop high performance SIBs.

Pt alloy catalysts, especially alloyed with Fe, Co, Ni, show greatly improved activities for oxygen reduction reaction (ORR) compared with Pt/C. In this work, Co (core)@PtCo (shell) is successfully synthesized based on the successful synthesis of the Co core by wet chemical way. Pt alloy shell is directly formed on Co core by the spontaneous galvanic displacement reaction in acid. The hollow Pt 3 Co alloy nanospheres are formed when Co@PtCo nanoparticles are treated in 1 mol l −1 sulfuric acid for 8 h. It is thought that the integral and contiguous PtCo alloy shell is important to form the hollow Pt 3 Co alloy nanospheres. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive X-ray spectroscopy (EDX), are used to characterize crystallite morphology and composition. The ORR activities of the nanoparticles are measured with a rotating ring disk electrode (RRDE) technique. The hollow Pt 3 Co alloy nanospheres with the size of about 10 nm show approximately 8 times in specific surface area activity and over 4 times in specific mass activity than that of the state-of-the art Pt/C. The electrochemical tests for duration of 5000 cycles at the sweep rate of 100 mVs −1 between 0.6 and 1.0 V (vs. RHE) in O 2 saturated electrolyte show that the hollow Pt 3 Co alloy nanospheres have a remarkable stability. These render the synthesized hollow Pt 3 Co alloy nanospheres as a promising candidate for the ORR electrocatalyst in Proton Exchange Membrane Fuel Cells (PEMFCs).

Two steps of wet chemical processes have been developed for the preparation of core-shell nanostructures of copper and silver, which is a facile and low cost method for the production of large quantity of dendritic powders. First step involves a galvanic displacement reaction with hydrogen evolution which is the motive force of spontaneous electrochemical reaction. To achieve the core-shell structure, silver has been coated on the dendritic copper using the galvanic displacement reaction. The dendritic silver-coated copper powders exhibit high surface-area, excellent conductivity, and good oxidation resistance. It has been found that silver-coated copper powders maintain the electrical conductivity even after annealing at 150 °C for several to tens of minutes, thus it is a promising material and an alternative to pure silver powders in printed electronics application.

The mobility of toxic elements, such as lead (Pb) can be attenuated by adsorption, incorporation, and precipitation on carbonate minerals in subsurface environments. Here, we report a study of the bulk transformation of single-crystal calcite (CaCO3) into polycrystalline cerussite (PbCO3) through reaction with acidic Pb-bearing solutions. This reaction began with the growth of a cerussite shell on top of calcite surfaces followed by the replacement of the remaining calcite core. The external shape of the original calcite was preserved by a balance between calcite dissolution and cerussite growth controlled by adjusting the Pb2+ concentration and pH. The relation between the rounded calcite core and the surrounding lath-shaped cerussite aggregates was imaged by transmission X-ray microscopy, which revealed preferentially elongated cerussite crystals parallel to the surface and edge directions of calcite. The replacement reaction involved concurrent development of ∼100 nm wide pores parallel to calcite c-gl...

High energy milling in combination with galvanic displacement were used for the preparation of bimetallic nanocatalysts. Co and Ni monometallic powders milled for 30 and 20 h, respectively were both produced in air atmosphere and used as precursors for the preparation of M-Pt (M = Co,Ni) compounds. Nanosized monometallic powders were physically supported on Vulcan carbon, and covered with 20 wt%Pt through a Galvanic Displacement Reaction (GDR) to produce Co-20Pt/C and Ni-20Pt/C electrocatalysts. XRD was used for phase identification on milled powders and for demonstrating structural transformations of Co powders during milling. Results on unmilled metallic Co powder show a predominant HCP structure modifying to a FCC structure after milling. Ni powders maintain their same FCC structure. Energy Dispersive X-Ray Spectometry (EDX) was used for chemical composition analysis on milled powders at several milling times. Scanning Transmission Electron Microscopy (STEM) show the formation of heterogeneous particle with ∼10 nm in size for both electrocatalysts. The electrocatalytic activity was evaluated by Cyclic Voltammetry (CV) and steady state Rotating Disk Electrode (RDE) for the Oxygen Reduction Reaction (ORR) in 0.1 M HClO 4 . The kinetic parameters on Co-20Pt/C conducted to the highest mass activity for the cathodic reaction.

A novel Sb/C polyhedra composite is successfully fabricated by a galvanic replacement reaction technique using metal organic frameworks as templates. In this composite, the ultrasmall Sb nanoparticles with an average size of 15 nm are homogeneously encapsulated into the carbon matrixes, forming a hierarchical porous structure with nanosized building blocks. Used as an anode material for lithium ion batteries, this composite exhibits high lithium storage capacities, excellent rate capability and superior cycle stability, higher than many reported results. Notably, a discharge capacity of 565 mAh g −1 at a current density of 0.2 A g −1 is delivered after 100 repeated cycles. Even at a high current density of 1 A g −1 , a discharge capacity of 400.5 mAh g −1 is also maintained after 500 cycles. Such superior cycling stability and rate discharge performance of the designed Sb/C composite can be attributed to the synergistic effect between Sb nanoparticles and the porous carbon matrixes.

Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl2 + HCl solution. Compared to Cu40Al60 and Cu45Al55 alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu17Al83 alloy as the starting alloy. The growth direction of the FDC is , and all angles between the trunks and branches are 60°. Nanoscale Cu2O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu17Al83 alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl2 intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

In this work, an in situ growth protocol is introduced to fabricate three-dimensional graphene films (3D GFs) on gold substrates, which are successfully utilized as working electrode for electrochemical detection of nucleic acid (microRNA) and protein (lysozyme) based on a signal-on sensing mechanism. To realize the bridge between the gold substrate and graphene film, a monolayer of 4-aminothiophenol is self-assembled on the substrate, which is then served as connectors for the growth of 3D GFs on the gold substrate by the hydrothermal reduction (HR) technique. Moreover, given the excellent properties, such as enlarged surface area, strong binding strength between 3D GFs and gold substrate, and improved conductivity, the proposed 3D GF-fabricated gold substrate is readily employed to the construction of electrochemical biosensing platforms through introduction of magnetic nanoparticles (MNPs) as probe carriers. On the basis of the strand displacement reaction and specific binding between aptamer and its target, the developed biosensors achieve signal-on detection of microRNA-155 (miR-155) and lysozyme (Lyz) with high sensitivity and selectivity and further successfully applied to human serum assay. Overall, the proposed strategy for in situ growth of 3D GFs provides a powerful tool for a wide range of applications, which is not limited to electrochemical biosensors and can be extended to other areas, such as electrocatalysis and electronic energy-related systems.

Heterointerface tailoring is of importance for the catalytic activity enhancement of nanomaterials in various reactions owing to the charge polarization at the interface. We report an accurate manipulation of a replacement reaction for Pt/PtTe heteronanowire and PtTe homonanowire fabrication. Their geometric structures are controlled by using the aged K2PtCl4 in ethylene glycol (EG) as Pt precursors with self-tuned coordination state and structure. The aging process enables the slow conversion of PtCl42– to linear structured PtmCln leading to their tunable oxidation ability. The Pt–Pt bond formation during aging has been revealed by time-resolved in situ UV–vis and X-ray absorption fine structure (XAFS) spectroscopies. The coexistence of a highly active Te template, PtCl42– ions, and linear structured PtmCln complexes allows Pt nanoparticles (NPs) to grow in situ on the PtTe nanowires (NWs), forming a controllable interface structure that served as catalytic active sites and charge transfer location. In c...

Two novel fluorescence “turn-on” cyanide probes based on the 1,3-dihydroisobenzofuran skeleton have been designed and synthesized: a terpyridyl-Cu 2+ ensemble sensed CN − in THF-H 2 O (1:1, v/v), and a dicyanovinyl-containing compound sensed CN − in CH 2 Cl 2 and THF. Titration of CN − with terpyridine-Cu 2+ complex caused a displacement reaction that turned on the fluorescence of A-Cu 2+ at 605 nm. The detection limit of A-Cu 2+ for CN − was calculated to be 3.15 × 10 −6 M. In the presence of CN − , the dicyanovinyl-bearing probe underwent a nucleophilic addition, showing 85-fold enhancement of fluorescence, with a detection limit of 5.39 × 10 −8 M. Our results demonstrate that these two strategies for designing a fluorophore skeleton based on the 1,3-dihydroisobenzofuran lead to highly selective “turn-on” probes for CN − .

Rechargeable performance was realized in a Mg-battery using a β-Cu 2 Se cathode. The average specific capacity was approximately 120 mAh/g for the first 35 cycles at room temperature, which was comparable with that of Chevrel phase as a prototype cathode material for Mg-batteries. The specific capacity was improved up to about 230 mAh/g by downsizing β-Cu 2 Se crystals, the short side length of which is about ∼100 nm. The displacement reaction, in which the inserted Mg ions induce the displacement and extrusion of Cu ions from Se-sublattices, was suggested as the plausible mechanism for the reversible electrochemical reaction in the battery cell cathode. This mechanism was supposed from the structural relationship between β-Cu 2 Se and MgSe.

Here we report a study on the role of chemical diffusion and reaction on the morphology evolution of silver particles. Electrochemical reaction is employed to synthesize silver particles. The reaction rate is regulated by current density while the diffusion rate of silver ions is regulated by the viscosity of solution. Silver dendritic particles are largely synthesized at various diffusion and reaction conditions. At a high reaction rate, silver dendrites are formed at the medium diffusion rates of silver ions while the dendritic structures are only formed at an extremely low diffusion rate of silver ions when the reaction proceeds slowly. Therefore, the interplay of diffusion and reaction plays a key role on the structure development of dendrites because the interplay determines the chemical distribution on the growth front of crystals. Once a chemical concentration gradient is established at the growth front, the dendritic structures is triggered.

The reaction process of copper–aluminum displacement in agar gel was observed at the microscopic level with a stereomicroscope; pine-like branches of copper crystals growing from aluminum surface into gel at a constant rate were observed. Students were asked to make hypotheses on the pattern formation and design new research approaches to prove their hypotheses. Results of the experiments designed by students well proved the existence of microcells in reaction system, which caused continuous growth of copper branches. The whole experimental teaching process motivated students by stimulating their interest and enthusiasm.

The synthesis of thioethers in excellent yields was achieved under mild conditions via the displacement reaction of halogens by sulfur. The cross-reaction of 2-(α-bromoacetyl)thiophene with triethylamine-activated phosphorus decasulfide (Et3N–P2S5) was elaborated by utilizing DFT calculations.

We have successfully developed a magnetic Al/Ni core–shell pigment via a galvanic displacement reaction to obtain low infrared emissivity pigment with low lightness and visible light reflectance. Al/Ni core–shell particles were prepared via a simple one-step synthetic method where Ni was deposited onto the Al surface at the expense of Al atoms. The influence of pH and the amount of NH4F complexing agent on phase structure, surface morphology, optical and magnetic properties were studied systematically. The neutral condition and high concentration of NH4F forms smooth, flat, uniform and dense Ni shell on the surface of flake Al particles, which can significantly reduce the lightness and visible light reflectance but slightly increase the infrared emissivity. When the core–shell pigments are prepared in neutral pH solution at NH4F = 11.2 g/L, the lightness (L*) and visual light reflectivity can be reduced by 12.6 and 0.46, respectively versus uncoated flake Al pigments, but the infrared emissivity is only increased by 0.02. The color changes from brilliant silver to gray black and the saturation magnetization value is 6.59 emu/g. Therefore, these Al/Ni magnetic composite pigments can be used as a novel low infrared emissivity pigment to improve the multispectral stealth performance of low-E coatings in the visual, IR and Radar wavebands.

A two-step method was used for fabricating PtCo alloy nanowires supported on free-standing carbon foam network (PtCo-NWs/CF). First, Co nanowires (Co-NWs) were successfully in situ formed on CF (Co-NWs/CF) through a hydrothermal procedure with a subsequent post annealing treatment. Second, PtCo-NWs/CF composite was prepared via the displacement reaction between PtCl42- and the as-synthesized Co-NWs in the presence of ascorbic acid. Moreover, by a simple electrochemical process, a “Pt-skin” can be formed on the PtCo nanowires. Due to the 3D hierarchical micron-grade porous carbon support and the PtCo alloy nanowires with a synergy effect between Pt and Co, the PtCo-NWs/CF shows excellent electrocatalytic activity toward ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR, undergoes a 4e− pathway). The prepared PtCo-NWs/CF displayed a more negative onset potential and higher current density for the ethanol oxidation compared to commercial Pt/C and the Pt/CF. For ORR, at −0.6 V, the PtCo-NW/CF shows a mass activity of 2.03 A mgPt−1, which is almost 6.34 and 3.44 times higher than those of the commercial Pt/C (0.32 A mgPt−1) and Pt/CF (0.59 A mgPt−1). Such high electrocatalytic performances of the PtCo-NWs/CF for both ethanol oxidation and oxygen reduction render it a promising catalyst for fuel cells.