Oxidation-assisted alkaline precipitation : the effect of H2O2 on the size of CuO and FeOOH nanoparticles

H2O2 was demonstrated to narrow the size distribution and decrease the size of CuO and hydrous FeOOH (2-line ferrihydrite) nanoparticles under conditions of high supersaturation. We introduce oxidation-assisted alkaline precipitation (Ox-AP) and compare it to traditional alkaline precipitation (AP). While for AP, a metal salt solution (e.g., CuCl2) is mixed with an alkali (e.g., NaOH), for Ox-AP, the more reduced form of that metal salt solution (e.g., CuCl) is simultaneously mixed with that alkali and an oxidant (e.g., H2O2). The resulting precipitates were characterized with SEM, XRD, DLS and single particle ICP-MS and shown to be nanoparticles (NPs). Ox-AP CuO NPs were up to 3 times smaller than AP NPs. Ox-AP FeOOH NPs were up to 22.5% smaller than AP NPs. We discuss and propose a possible mechanism of Ox-AP through careful consideration of the known reaction chemistry of iron and copper. We propose that an increased monomer formation rate enhances the nucleation rate, which ultimately results in smaller particles with a more narrow distribution. The more distinct effect of Ox-AP on copper, was attributed to the fast formation of the stable CuO monomer, compared to AP, where the Cu(OH)(2) and/or Cu-2(OH)(3)Cl monomers are more likely formed. Although, the exact mechanism of Ox-AP needs experimental confirmation, our results nicely demonstrate the potential of using Ox-AP to produce smaller NPs with a more narrow distribution in comparison to using AP

Investing in a Customer Relationship Management System : Case Esa Print Oy

The intention of this thesis is to help and guide a Finnish printing company Esa Print to invest in a customer relationship management (CRM) system. Also the main purpose of this thesis is to improve Esa Prints awareness towards these CRM systems and give a deeper insight how these systems could benefit their sales organization

Scalable electrodeposition of liquid metal from an acetonitrile-based electrolyte for highly-integrated stretchable electronics

For the advancement of highly-integrated stretchable electronics, the development of scalable sub-micrometer conductor patterning is required. Eutectic gallium indium EGaIn is an attractive conductor for stretchable electronics, as its liquid metallic character grants it high electrical conductivity upon deformation. However, its high surface energy precludes patterning it with (sub)-micron resolution. Herein, we overcome this limitation by reporting for the first time the electrodeposition of EGaIn. We use a non-aqueous acetonitrile-based electrolyte that exhibits high electrochemical stability and chemical orthogonality. The electrodeposited material led to low-resistance lines that remained stable upon (repeated) stretching to a 100 percent strain. Because electrodeposition benefits from the resolution of mature nanofabrication methods used to pattern the base metal, the proposed bottom-up approach achieved a record-high density integration of EGaIn regular lines of 300 nm half-pitch on an elastomer substrate by plating on a gold seed layer pre-patterned by nanoimprinting. Moreover, vertical integration was enabled by filling high aspect ratio vias. This capability was conceptualized by the fabrication of an omnidirectionally stretchable 3D electronic circuit, and demonstrates a soft-electronic analogue of the stablished damascene process used to fabricate microchip interconnects. Overall, this work proposes a simple route to address the challenge of metallization in highly integrated (3D) stretchable electronics.Comment: The main manuscript contains 29 pages and 5 figures. The supporting information, attached to the document after the references, contains 8 pages and 8 figures. The manuscript is submitted to the journal Advanced Materials. Francisco Molina-Lopez an Jan Fransaer share the role of corresponding autho

Gas diffusion electrodes on the electrosynthesis of controllable iron oxide nanoparticles

The electrosynthesis of iron oxide nanoparticles offers a green route, with significant energy and environmental advantages. Yet, this is mostly restricted by the oxygen solubility in the electrolyte. Gas-diffusion electrodes (GDEs) can be used to overcome that limitation, but so far they not been explored for nanoparticle synthesis. Here, we develop a fast, environmentally-friendly, room temperature electrosynthesis route for iron oxide nanocrystals, which we term gas-diffusion electrocrystallization (GDEx). A GDE is used to generate oxidants and hydroxide in-situ, enabling the oxidative synthesis of a single iron salt (e.g., FeCl_2) into nanoparticles. Oxygen is reduced to reactive oxygen species, triggering the controlled oxidation of Fe^(2+) to Fe^(3+), forming Fe_(3-x)O_(4-x) (0 <= x <= 1). The stoichiometry and lattice parameter of the resulting oxides can be controlled and predictively modelled, resulting in highly-defective, strain-heavy nanoparticles. The size of the nanocrystals can be tuned from 5 nm to 20 nm, with a large saturation magnetization range (23 to 73 A m^2 kg^(-1)), as well as minimal coercivity (similar to 1 kA m^(-1)). Using only air, NaCl, and FeCl_2, a biocompatible approach is achieved, besides a remarkable level of control over key parameters, with a view on minimizing the addition of chemicals for enhanced production and applications

Spin transition nanoparticles made electrochemically

Materials displaying novel magnetic ground states signify the most exciting prospects for nanoscopic devices for nanoelectronics and spintronics. Spin transition materials, e.g., spin liquids and spin glasses, are at the forefront of this pursuit; but the few synthesis routes available do not produce them at the nanoscale. Thus, it remains an open question if and how their spin transition nature persists at such small dimensions. Here we demonstrate a new route to synthesize nanoparticles of spin transition materials, gas-diffusion electrocrystallization (GDEx), wherein the reactive precipitation of soluble metal ions with the products of the oxygen reduction reaction (ORR), i.e., in situ produced H_2O_2, OH^-, drives their formation at the electrochemical interface. Using mixtures of Cu^(2+) and Zn^(2+) as the metal precursors, we form spin transition materials of the herbertsmithite family-heralded as the first experimental material known to exhibit the properties of a quantum spin liquid (QSL). Single-crystal nanoparticles of similar to 10-16 nm were produced by GDEx, with variable Cu/Zn stoichiometry at the interlayer sites of Zn_xCu_(4-x)(OH)_6Cl_2. For x = 1 (herbertsmithite) the GDEx nanoparticles demonstrated a quasi-QSL behavior, whereas for x = 0.3 (0.3 < x < 1 for paratacamite) and x = 0 (clinoatacamite) a spin-glass behavior was evidenced. Finally, our discovery not only confirms redox reactions as the driving force to produce spin transition nanoparticles, but also proves a simple way to switch between these magnetic ground states within an electrochemical system, paving the way to further explore its reversibility and overarching implications

A yolk-albumen-shell structure of mixed Ni-Co oxide with an ultrathin carbon shell for high-sensitivity glucose sensors

Altres ajuts: ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. TZ has received funding from the CSC-UAB PhD scholarship program.Non-enzymatic glucose sensors based on different Co-Ni-C composite materials were developed by pyrolysis of bimetallic or single metal based metal-organic frameworks (MOFs). The structure and composition of the resulting materials were explored by XRD, nitrogen adsorption/desorption isotherms, SEM, HRTEM and STEM-EELS. The electrochemical performance of the bimetallic MOF derived novel yolk-albumen-shell structure of Ni-Co@C (YASNiCo@C) stands out from these materials. The YASNiCo@C electrode exhibited a sensitivity of 1964 μA cm-2 mM-1 with the detection limit of 0.75 μM, a linear range from 5 μM to 1000 μM and good stability for the detection of glucose. These promising electrochemical performances prove that YASNiCo@C is a promising material for glucose sensors. Moreover, the strategy outlined in this work for the design of MOF based nanomaterials can also be used beyond glucose sensors

A universal strategy for metal oxide anchored and binder-free carbon matrix electrode : a supercapacitor case with superior rate performance and high mass loading

Financial support from China Fund KU Leuven (ISP/13/02SJT) is acknowledged. J. Luo acknowledges the Research Foundation - Flanders (FWO) for FWO Postdoctoral Fellowship (12F5514N), a Research Grant (Project number: 1529816N) and a travel grant (V410316N) for a Visiting Professorship in Technical University of Denmark. X. Zhang is grateful to the China Scholarship Council. We thank Prof. Dirk De Vos (KU Leuven) for technical discussions, Prof. Lei Li (Shanghai Jiao Tong University) for providing nickel foams and Prof. Qingfeng Li (Technical University of Denmark) for assistance in TEM measurements. Appendix ADespite the significant advances in preparing carbon-metal oxide composite electrodes, strategies for seamless interconnecting of these two materials without using binders are still scarce. Herein we design a novel method for in situ synthesis of porous 2D-layered carbon-metal oxide composite electrode. Firstly, 2D-layered Ni-Co mixed metal-organic frameworks (MOFs) are deposited directly on nickel foam by anodic electrodeposition. Subsequent pyrolysis and activation procedure lead to the formation of carbon-metal oxides composite electrodes. Even with an ultrahigh mass loading of 13.4 mg cm, the as-prepared electrodes exhibit a superior rate performance of 93% (from 1 to 20 mA cm), high capacitance (2098 mF cm at a current density of 1 mA cm), low resistance and excellent cycling stability, making them promising candidates for practical supercapacitor application. As a proof of concept, several MOF derived electrodes with different metal sources have also been prepared successfully via the same route, demonstrating the versatility of the proposed method for the preparation of binder-free carbon-metal oxide composite electrodes for electrochemical devices

Critical Role of Phosphorus in Hollow Structures Cobalt-Based Phosphides as Bifunctional Catalysts for Water Splitting

Cobalt phosphides electrocatalysts have great potential for water splitting, but the unclear active sides hinder the further development of cobalt phosphides. Wherein, three different cobalt phosphides with the same hollow structure morphology (CoP-HS, CoP-HS, CoP-HS) based on the same sacrificial template of ZIF-67 are prepared. Surprisingly, these cobalt phosphides exhibit similar OER performances but quite different HER performances. The identical OER performance of these CoP-HS in alkaline solution is attributed to the similar surface reconstruction to CoOOH. CoP-HS exhibits the best catalytic activity for HER among these CoP-HS in both acidic and alkaline media, originating from the adjusted electronic density of phosphorus to affect absorption–desorption process on H. Moreover, the calculated ΔG based on P-sites of CoP-HS follows a quite similar trend with the normalized overpotential and Tafel slope, indicating the important role of P-sites for the HER process. Moreover, CoP-HS displays good performance (cell voltage of 1.67 V at a current density of 50 mA cm) and high stability in 1 M KOH. For the first time, this work detailly presents the critical role of phosphorus in cobalt-based phosphides for water splitting, which provides the guidance for future investigations on transition metal phosphides from material design to mechanism understanding.W.Z. and N.H. contributed equally to this work. X.Z. and J.F. are grateful for the Research Foundation-Flanders (FWO) project (12ZV320N). Funding from National Natural Science Foundation of China (project No.: 22005250, 21776120, and 51901161) is appreciated. M.X. is grateful to the National Natural Science Foundation of China (project No.: 22179109). W.Z. is grateful to the China Scholarship Council (NO. 201808310068). W.G. is grateful to the China Scholarship Council (NO. 201806030189). S.X. is grateful to the China Scholarship Council. K.W. is grateful to the Oversea Study Program of Guangzhou Elite Project. Funding from the Research Foundation–Flanders (FWO) (project No.: G0B3218N) and Natural Science Foundation of Fujian Province, China (No.: 2018J01433) is acknowledged. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project ECOCAT and subproject NANOGEN. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. This work has received funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No. 654360 NFFA-Europe. X.H. thanks China Scholarship Council for scholarship support (201804910551)