Dissolution Of Metal Nanoparticles Research Articles

Renewable electrochemical detection interface for thousand times based on zinc doping perovskite-like material

Simple and multiple regeneration of electrochemical detection interface is still an extreme challenge. Inspired by reversible exsolution and dissolution of metal nanoparticles in perovskite, a renewable electrochemical detection interface modified with Zn0.5NiOOH enabling zinc to undergo switching from multivalent-zinc to zero-valent-zinc driven by potential was designed. Zinc was doped into NiOOH lattice along (003) facet in an interstitial mechanism, which empowered zinc to exsolve from NiOOH. Solvation and electrostatic effects enabled zinc to re-dissolve into the lattice. Zn0.5NiOOH-modified electrochemical detection interface for tumor marker can be rapidly regenerated in 50 s, regeneration rate was more than 99%, and number of reuses reached 1000 times. As a proof-of-concept, an electrochemical immunoassay based on the Zn0.5NiOOH-modified detection interface was constructed for detection of squamous cell carcinoma (SCCA), whose platform can be easily regenerated and exhibit an excellent analytical performance with a wide range from 1 μg mL−1 to 1 pg mL−1 and ultralow detection limit of 100.98 fg mL−1. The work represents a significant improvement of electrochemical sensor in practical applications.

Exsolution of Co-Fe Alloy Nanoparticles on the PrBaFeCoO5+δ Layered Perovskite Monitored by Neutron Powder Diffraction and Catalytic Effect on Dry Reforming of Methane.

Reversible exsolution and dissolution of metal nanoparticles (NPs) in complex oxides have been investigated as an efficient strategy to improve the performance and durability of the catalysts for thermal and electrochemical energy conversion. Here, in situ exsolution of Co-Fe alloy NPs from the layered perovskite PrBaFeCoO5+δ (PBFC) and their dissolution back into the oxide host have been monitored for the first time by in situ neutron powder diffraction and confirmed by X-ray diffraction and electron microscopy. Catalytic tests for dry reforming of methane showed stable operation over ∼100 h at 800 °C with negligible carbon deposition (<0.3 mg/gcat h). The CO2 and CH4 conversions are among the highest achieved by layered double perovskites. The cyclability of the PBFC catalyst and the potential to improve the catalytic activity by adjusting the composition, size, and the NP distribution would pave the way for highly efficient energy conversion applications.

On the Stability of Pt‐Based Catalysts in HBr/Br2 Solution

AbstractStability studies on supported metal nanoparticles are essential for gaining insight into the design and optimization of high‐performance materials. In this work, the dissolutions of Pt‐based catalysts in HBr/Br2 mixture of various concentration regimes were studied and correlated with material structural properties. The dissolution of metal nanoparticles was enhanced by adding Br2 to the HBr solution. Comparing with commercial Pt/C catalyst, the well‐alloyed PtIr/C catalyst was observed to exhibit high resistance towards dissolution. In addition, regulating the accessibility of the metal sites to dissolution‐inducing species contributed to the marked stability of the nanoparticles in HBr/Br2 solutions, as shown for the surface‐modified PtIr/C catalysts with organic diamine molecules.

In Situ Investigation of Reversible Exsolution/Dissolution of CoFe Alloy Nanoparticles in a Co-Doped Sr2 Fe1.5 Mo0.5 O6- δ Cathode for CO2 Electrolysis.

Reversible exsolution and dissolution of metal nanoparticles in perovskite has been investigated as an efficient strategy to improve CO2 electrolysis performance. However, fundamental understanding with regard to the reversible exsolution and dissolution of metal nanoparticles in perovskite is still scarce. Herein, in situ exsolution and dissolution of CoFe alloy nanoparticles in Co-doped Sr2 Fe1.5 Mo0.5 O6-δ (SFMC) revealed by in situ X-ray diffraction, scanning transmission electron microscopy, environmental scanning electron microscopy, and density functional theory calculations are reported. Under a reducing atmosphere, facile exsolution of Co promotes reduction of the Fe cation to generate CoFe alloy nanoparticles in SFMC, accompanied by structure transformation from double perovskite to layered perovskite at 800 °C. Under an oxidizing atmosphere, spherical CoFe alloy nanoparticles are first oxidized to flat CoFeOx nanosheets, and then dissolved into the bulk with structure evolution from layered perovskite back to double perovskite. Electrochemically, CO2 electrolysis performance can be retrieved during 12 redox cycles due to the regenerative ability of the CoFe alloy nanoparticles. The anchoring of the CoFe alloy nanoparticles in SFMC perovskite via reduction shows enhanced CO2 electrolysis performance and stability compared with the parent SFMC perovskite.

In the Search for Nanospecific Effects of Dissolution of Metallic Nanoparticles at Freshwater-Like Conditions: A Critical Review.

Knowledge on relations between particle properties and dissolution/transformation characteristics of metal and metal oxide nanoparticles (NPs) in freshwater is important for risk assessment and product development. This critical review aims to elucidate nanospecific effects on dissolution of metallic NPs in freshwater and similar media. Dissolution rate constants are compiled and analyzed for NPs of silver (Ag), copper (Cu), copper oxide/hydroxide (CuO, Cu(OH)2), zinc oxide (ZnO), manganese (Mn), and aluminum (Al), showing largely varying (orders of magnitude) constants when modeled using first order kinetics. An effect of small primary sizes (<15 nm) was observed, leading to increased dissolution rate constants and solubility in some cases. However, the often extensive particle agglomeration can result in reduced nanospecific effects on dissolution and also an increased uncertainty related to the surface area, a parameter that largely influence the extent of dissolution. Promising ways to model surface areas of NPs in solution using fractal dimensions and size distributions are discussed in addition to nanospecific aspects related to other processes such as corrosion, adsorption of natural organic matter (NOM), presence of capping agents, and existence of surface defects. The importance of the experimental design on the results of dissolution experiments of metal and metal oxide NPs is moreover highlighted, including the influence of ionic metal solubility and choice of particle dispersion methodology.

Hybrid PtCo Alloy Nanocatalysts Encapsulated by Porous Carbon Layers for Oxygen Reduction Reactions

During a long-term operation of polymer electrolyte membrane fuel cells(PEMFCs), the fuel cell performance may degrade due to severe agglomeration and dissolution of metal nanoparticles in the cathode. To enhance the electrochemical durability of metal catalysts and to prevent the particle agglomeration in PEMFC operation, this paper proposes a hybrid catalyst structure composed of PtCo alloy nanoparticles encapsulated by porous carbon layers. In the hybrid catalyst structure, the dissolution and migration of PtCo nanoparticles can be effectively prevented by protective carbon shells. In addition, O2 can properly penetrate the porous carbon layers and react on the active Pt surface, which ensures high catalytic activity for the oxygen reduction reaction. Although the hybrid catalyst has a much smaller active surface area due to the carbon encapsulation compared to a commercial Pt catalyst without a carbon layer, it has a much higher specific activity and significantly improved durability than the Pt catalyst. Therefore, it is expected that the designed hybrid catalyst concept will provide an interesting strategy for development of high-performance fuel cell catalysts.

(Invited) Stability of Palladium Electrocatalysts in Alkaline Solutions

It has been found that the durability of Pt/C in alkaline solutions is worse than in acidic medium during potential cycling.1 The durability of Pd/C, which shows even higher activity toward oxygen reduction reaction than Pt/C in alkaline solutions, has not been systematically studied. In this study, the commercial Pt/C (46%, TEC10E50E, TKK) and Pd/C (30%, TECPdE30, TKK) were chosen to evaluate the durability during potential cycling in various potential windows and cycling patterns. The potential decay in terms of half-wave potential was compared after 2500, 5000 and 10000 cycles. It was found that the Pd/C had a much better durability than Pt/C under the same conditions. The dissolution of metal nanoparticles was detected by utilizing an electrochemical cell directly coupled to an inductively coupled plasma mass spectrometer (ICP-MS) to understand the origins of the higher stability of Pd/C. References Anicet Zadick, Laetitia Dubau, Nicolas Sergent, Gregory Berthome, and Marian Chatenet. Huge instability of Pt/C catalysts in alkaline medium[J]. ACS Catalysis, 2015, 5(8): 4819-4824.

Assessing the toxicity and the dissolution rate of zinc oxide nanoparticles using a dual-color Escherichia coli whole-cell bioreporter

Particle toxicity and metal ions from the dissolution of metallic nanoparticles (NPs) can have environmentally toxic effects. Among the diverse metallic NPs, four types of zinc oxide NPs (ZnO-NPs)—two spherical (diameters <50 nm and <100 nm) and two wire (50 nm × 300 nm and 90 nm × 1000 nm) shaped—were examined using dual-color whole-cell bioreporters (WCBs) to elucidate the relationships among size, shape, and toxicity. The amount of Zn(II) ions dissolved from NPs was determined by measuring mCherry expression because the presence of Zn(II) ions induced the expression of mCherry from pZnt-mCherry in dual-color WCBs. The overall toxic effects were assessed by measuring Escherichia coli cell growth. The toxic effect on cell growth was determined by measuring the expression of eGFP from the dual-color WCBs to avoid interferences in the signal acquisition caused by inseparable NPs. The novel approach demonstrated here used dual-color WCBs to simultaneously assess the toxicity of ZnONPs on E. coli and the dissolution rates of ZnO-NPs. Toxicity varied depending upon the size and shape of the ZnONPs. The dissolution rate did not vary significantly according to size and shape; smaller sizes and wire shapes showed higher toxicity. Therefore, the physical properties of ZnONPs play a role in the overall toxic effect as well as dissolved Zn(II) ions.

Assessing bioavailability and genotoxicity of heavy metals and metallic nanoparticles simultaneously using dual-sensing Escherichia coli whole-cell bioreporters

Genetically engineered bacterial strains called whole-cell bioreporters (WCBs) generated by fusing the promoter region of stress-responsive genes and reporter genes have been widely used as biosensors to detect toxic materials in the environment. In this study, we report a dual-sensing WCB harboring recAp::egfp and zntAp::mcherry to measure the genotoxicity and bioavailability of heavy metals and metallic nanoparticles (NPs) simultaneously. Since the dual-sensing WCB harbored recAp::egfp and zntAp::mcherry, the genotoxicity and bioavailability of heavy metals and metallic NPs that activate ZntR would be assessed by measuring the fluorescence signal of enhanced green fluorescent protein (eGFP) and mCherry, respectively. Among the tested heavy metal(loid)s, only Cr induced both eGFP and mCherry expression, and some of them only induced mCherry, thereby suggesting that Cr is genotoxic. In case of the tested metallic NPs, Ti2O NPs, ZnO NPs, and Au NPs showed weak inhibitory effects on growth, but the eGFP was not induced. It was inferred that the tested NPs were not genotoxic and the inhibitory effects would not be related to direct DNA damage pathways. In addition, it was observed that ZnO NPs induced mCherry expression, indicating that the Zn ion was dissolved from the NPs. Although the dual-sensing WCB described here was limited to ZnO NPs, WCBs would be an alternative tool to investigate the dissolution of metallic NPs when the corresponding metal ion sensing systems were available.

Uniformly oriented, ellipsoidal nanovoids in glass created by electric-field-assisted dissolution of metallic nanoparticles

Nanoporous glass containing spherical or ellipsoidal nanovoids, respectively, has been produced by electric-field-assisted dissolution of Ag nanoparticles embedded in glass-metal nanocomposites. Small angle x-ray scattering before and after particle dissolution gives evidence that in the case of spherical nanoparticles the remaining nanovoids have the same size distribution ($\ensuremath{\approx}20\text{ }\text{nm}$ average diameter) as the original silver particles. Spheroidal particles of uniform orientation leave strongly aspherical nanovoids, which undergo a slight shape relaxation from aspect ratio 4.7 (particles) to 3.8 (holes).

Laser annealing of metal-dielectric nanocomposites formed by ion implantation

Metal-dielectric composites have been fabricated by ion synthesis of silver nanoparticles in soda-lime silicate glass. Ion implantation has been performed with Ag + ions at 60keV to a dose of 4 10 16 ionscm -2 . The glass was annealed using pulses of a high-power KrF excimer laser (248nm) in an ambient atmosphere. This employed a single (25ns) pulse fluence of 0.25Jcm -2 for implanted samples. From 1 to 250 pulses with the same energy densities and at a frequency of 1Hz were accumulated in the same area on the glass surface. The formation and modification of metal nanoparticles were assessed via optical reflectance, combined with Rutherford back-scattering analysis. Generally, changes induced by laser pulses suggest there are both reductions in the nanoparticles and some longer-range diffusion of metal atoms into the glass. However, before the total dissolution of metal nanoparticles occurs, increases in the substrate temperature during many-pulse treatments initiate the regrowth of new metal nanoparticles, which leads to a rise in the reflectance. These results are discussed on the basis of surface substrate melting.