Organic functionalization of luminescent oxide nanoparticles toward their application as biological probes

Luminescent inorganic nanoparticles are now widely studied for their applications as biological probes for in vitro or in vivo experiments. The functionalization of the particles is a key step toward these applications, since it determines the control of the coupling between the particles and the biological species of interest. This paper is devoted to the case of rare earth doped oxide nanoparticles and their functionalization through their surface encapsulation with a functional polysiloxane shell. The first step of the process is the adsorption of silicate ions that will act as a primary layer for the further surface polymerization of the silane, either aminopropyltriethoxysilane (APTES) or glycidoxypropyltrimethoxysilane (GPTMS). The amino- or epoxy- functions born by the silane allow the versatile coupling of the particles with bio-organic species following the chemistry that is commonly used in biochips. Special attention is paid to the careful characterization of each step of the functionalization process, especially concerning the average number of organic functions that are available for the final coupling of the particles with proteins. The surface density of amino or epoxy functions was found to be 0.4 and 1.9 functions per square nanometer for GPTMS and APTES silanized particles, respectively. An example of application of the amino-functionalized particles is given for the coupling with alpha-bungarotoxins. The average number (up to 8) and the distribution of the number of proteins per particle are given, showing the potentialities of the functionalization process for the labeling of biological species.     

简易电沉积法制备CoFe-P催化剂用于高效析氧反应

开发低成本、高活性且稳定的非贵金属催化剂是实现大规模电解水制氢的关键所在。在此,我们通过简便、合理的电沉积法在泡沫镍(NF)上构建了一种具备超薄二维纳米片形貌的高度非晶相Co1Fe1-P薄膜用于高效催化析氧反应（OER）。在1.0mol·L^-1 KOH溶液中,所制备的Co1Fe1-P/NF催化剂在电流密度为10和100 mA·cm^-2处的过电位分别为274.4和329.5 mV,Tafel斜率仅为45.3 mV·dec^-1,可以媲美商业RuO₂催化剂。此外,Co1Fe1-P/NF催化剂在10 mA·cm^-2的100 h计时电压法测试和1 000次循环伏安法测试中均表现出卓越的催化稳定性。Co1Fe1-P/NF催化剂优秀的催化活性归因于其独特的形貌、高度非晶相结构提供的低能垒、优化的电子结构以及钴磷化物和铁磷化物的强协同效应。     

简易电沉积法制备CoFe-P催化剂用于高效析氧反应

开发低成本、高活性且稳定的非贵金属催化剂是实现大规模电解水制氢的关键所在。在此,我们通过简便、合理的电沉积法在泡沫镍(NF)上构建了一种具备超薄二维纳米片形貌的高度非晶相Co1Fe1-P薄膜用于高效催化析氧反应(OER)。在1.0mol·L^-1 KOH溶液中,所制备的Co1Fe1-P/NF催化剂在电流密度为10和100 mA·cm^-2处的过电位分别为274.4和329.5 mV,Tafel斜率仅为 45.3 mV·dec^-1,可以媲美商业 RuO₂催化剂。此外,Co1Fe1-P/NF 催化剂在 10 mA·cm^-2的 100 h 计时电压法测试和1 000次循环伏安法测试中均表现出卓越的催化稳定性。Co1Fe1-P/NF催化剂优秀的催化活性归因于其独特的形貌、高度非晶相结构提供的低能垒、优化的电子结构以及钴磷化物和铁磷化物的强协同效应。     

Nickel oxide nanoparticles catalyzed synthesis of poly-substituted quinolines via Friedlander hetero-annulation reaction

Reusable acidic nickel oxide nanoparticles have been synthesized,characterized and applied as a catalyst to convert 2-aminoaryl ketones and β-ketoesters/ketones into the corresponding quinolines in good yields with high selectivity.This could serve as a simple and convenient procedure for the Friedlander annulations.     

Electrochemical and optical studies of thick oxide layers on iridium and their electrocatalytic activities for the oxygen evolution reaction

Thick oxide layers can be grown on iridium in 0.5 M H₂SO₄ by a potential multicyling treatment, mainly due to the highly irreversible reaction — the electroreduction of the lower hydroxide. The optical analysis of such layers was performed by combined ellipsometric and reflectometric measurements. The results of these measurements show that a hydroxide layer with n_film=1.44–0.01 i and a thickness which may exceed 2000 Å remains even at cathodic potentials on the Ir electrode, as a result of multicycling. Application of anodic potentials close to the OER region results in an increase of the extinction coefficient to a level typical for semiconductors (n_film=1.43–0.10 i at 1.50 V). This thick semiconducting phase oxide on Ir in the OER region seems to have a high level of bulk defects and a high surface concentration of active sites, the generation of both being related to the gradual variation of the oxidation state of the Ir ions in the oxide, prior to and simultaneously with the evolution of oxygen. The oxygen evolution rates on Ir between 1.50–1.60 V are shown to increase significantly in the presence of such thick oxide layers (as compared with electrodes not coverred by thick layers); a lower Tafel slope is also observed on these thick oxides.     

Surface facets dependent oxygen evolution reaction of single Cu2O nanoparticles

Understanding and establishing the structure-activity relation of nanoparticles is a prerequisite for rational design of high-performance electrocatalysts. Cu₂O nanoparticles enclosed with different crystal facets, namely, o-Cu₂O NPs with {111} facets, c-Cu₂O NPs with {100} facets are prepared and their electrocatalytic properties for oxygen evolution reaction (OER) in alkaline condition are evaluated at single nanoparticle level with a combination of scanning electrochemical cell microscopy and scanning electron microscopy. It is found that the o-Cu₂O NPs have significantly superior OER electrocatalytic activity compared to c-Cu₂O, which is almost inert. The estimated turnover frequency (TOF) at 1.97 V vs. RHE on {111} facet increases from 4 s^?1 to 115 s^?1 with the octahedron edge length decreasing from 1.3 µm to 100 nm. Deposition of carbon on c-Cu₂O surface barely promotes the activity, suggesting the inherent poor electric conductivity within the nanocrystal is most likely the reason for low activity. This work provides direct probing to single transition metal oxide crystals with dramatically different activity.     

Nickel iron carbonate hydroxide hydrate decorated with CeOx for highly efficient oxygen evolution reaction

Journal of Solid State Electrochemistry - Highly active, durable, and inexpensive nanostructured catalysts are crucial for achieving efficiently and economically electrochemical water splitting. In...     

二氧化铈纳米微粒过氧化物酶活性及其在葡萄糖检测中的应用

合成了一种稳定和水溶性的聚丙烯酸修饰CeO2 NPs,利用动态光散射(DLS)、傅里叶变换红外光谱(FT-IR)和X射线光电子能谱(XPS)进行表征.结果表明,CeO2 NPs能够催化H2O2氧化3,3′,5,5′-四甲基联苯胺(TMB)发生显色反应,表现出过氧化物模拟酶催化活性.利用Raman和顺磁共振(EPR)光谱技术研究了其催化机理.基于CeO2 NPs催化TMB变色反应对H2O2浓度的依赖性和葡萄糖氧化酶能够催化溶解氧氧化葡萄糖产生H2O2的原理,构建了一种简单、灵敏、选择性高的测定血清中葡萄糖的检测方法.在优化条件下,测定葡萄糖的线性范围为0.5~10 mmol/L,检出限(3σ)为0.1 mmol/L.对1.0 mmol/L葡萄糖进行11次平行测定,其相对标准偏差为2.4%.该方法已成功用于血清样品中葡萄糖的测定.     

The sum is more than its parts: stability of MnFe oxide nanoparticles supported on oxygen-functionalized multi-walled carbon nanotubes at alternating oxygen reduction reaction and oxygen evolution reaction conditions

Successful design of reversible oxygen electrocatalysts does not only require to consider their activity towards the oxygen reduction (ORR) and the oxygen evolution reactions (OER), but also their electrochemical stability at alternating ORR and OER operating conditions, which is important for potential applications in reversible electrolyzers/fuel cells or metal/air batteries. We show that the combination of catalyst materials containing stable ORR active sites with those containing stable OER active sites may result in a stable ORR/OER catalyst if each of the active components can satisfy the current demand of their respective reaction. We compare the ORR/OER performances of oxides of Mn (stable ORR active sites), Fe (stable OER active sites), and bimetallic Mn_0.5Fe_0.5 (reversible ORR/OER catalyst) supported on oxidized multi-walled carbon nanotubes. Despite the instability of Mn and Fe oxide for the OER and the ORR, respectively, Mn_0.5Fe_0.5 exhibits high stability for both reactions.

     

One-pot synthesis of NiPt core–shell nanoparticles toward efficient oxygen reduction reaction

Journal of Solid State Electrochemistry - Creating bimetallic Pt-based nanocrystals with core–shell structures has widely been recognized as the most effective way for improving their...     

Cuprous oxide nanoparticles dispersed on reduced graphene oxide as an efficient electrocatalyst for oxygen reduction reaction

Cuprous oxide (Cu(2)O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu(2)O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction.     

Pseudo-potentiostatic electrolysis by potential buffering induced by the oxygen evolution reaction

A new approach is proposed in order to perform electrochemical oxidation of organics by working under galvanostatic conditions with the potential ‘buffered’ by the competing side reaction of oxygen evolution (OER). According to this process the working potential is fixed by the nature of electrode material and is buffered during organics oxidation by the side reaction of OER. This principle has been used for the selective oxidation of some model organic compounds on Ti/IrO₂ anode.     

Application of metal chalcogenide-based anodic electrocatalyst toward substituting oxygen evolution reaction in water splitting

Electrochemical water splitting for producing hydrogen has received increasing attention. However, the large overpotential of oxygen evolution reaction (OER) is a bottleneck in water splitting. Exploiting value-added alternative reactions to replace the OER semi-reaction in water splitting can not only produce valuable products at both electrodes, but also reduce the overpotential of water splitting. Recently, metal chalcogenides (sulfides and selenides) have been widely studied in electrocatalytic reactions. This review concentrates on the recent application of metal chalcogenides in value-added anodic reactions by replacing the OER during electrochemical water splitting, including urea oxidation reaction (UOR), 5-hydroxymethylfurfural electrochemical oxidation reaction (HMF-EOR), which provides the guidance for the rational design of advanced metal chalcogenide electrocatalysts in renewable energy.     

Nickel surface anodic oxidation and electrocatalysis of oxygen evolution

The processes of nickel surface anodic oxidation taking place within the range of potentials preceding oxygen evolution reaction (OER) in the solutions of 1 M KOH, 0.5 M K₂SO₄, and 0.5 M H₂SO₄ have been analyzed in the present paper. Metallic nickel, thermally oxidized nickel, and black nickel coating were used as Ni electrodes. The methods of cyclic voltammetry and X-ray photoelectron spectroscopy were employed. The study was undertaken with a view to find the evidence of peroxide-type nickel surface compounds formation in the course of OER on the Ni electrode surface. On the basis of experimental results and literature data, it has been suggested that in alkaline solution at E ≈ 1.5 V (RHE) reversible electrochemical formation of Ni(IV) peroxide takes place according to the reaction as follows: This reaction accounts for both the underpotential (with respect to ) formation of O₂ from NiOO₂ peroxide and also small experimental values of dE/dlgi slope (<60 mV) at low anodic current densities, which are characteristic for the two-electron transfer process. It has been inferred that the composition of the γ-NiOOH phase, indicated in the Bode and revised Pourbaix diagrams, should be ∼5/6 NiOOH + ∼1/6 NiOO₂. The schemes demonstrating potential-dependent transitions between Ni surface oxygen compounds are presented, and the electrocatalytic mechanisms of OER in alkaline, acid, and neutral medium have been proposed.     

Fractional reaction orders in oxygen evolution from acidic solutions at ruthenium oxide anodes

Oxygen evolution at RuO₂ anodes from acidic solutions exhibits a fractional reaction order with respect to H⁺. This is close to −1 for a set of “compact” film electrodes, and close to −2 for a set of “cracked” film electrodes. The difference in mechanism is related to the different defect structure of the surface. Possible reasons for the observed fractional reaction orders are discussed. It is suggested that the experimental observation may be explained in terms of the reaction proceeding with different mechanisms in parallel on different patches of the surface whose structure is governed by the acid-base properties of the oxide.     

Manganese oxide with hollow rambutan-like morphology as highly efficient electrocatalyst for oxygen evolution reaction

The research about oxygen evolution reaction (OER) has attracted extensive attention. In this work, different manganese oxides with different shell thickness were firstly grown on the surface of carbon ball template, and then the carbon ball was removed by high-temperature calcination in air to obtain hollow rambutan-like Mn₂O₃ and MnO₂–Mn₂O₃ with long nanowires. The concentration of inorganic manganese salt and the reaction time has a determining influence on the morphologies of manganese oxide. The as-prepared MnO₂–Mn₂O₃ exhibits a lower overpotential than the Mn₂O₃ to achieve a current density of 10 mA cm^?2. The Faradic efficiency of MnO₂–Mn₂O₃ reaches to 94.1% during the bulk electrolysis, and the morphology of MnO₂–Mn₂O₃ remains virtually unchanged after electrolysis, indicating the outstanding stability of the as-obtained MnO₂–Mn₂O₃.     

Nitrogen-enriched carbon powder prepared by ball-milling of graphene oxide with melamine: an efficient electrocatalyst for oxygen reduction reaction

A simple strategy for the production of an efficient platinumfree electrocatalyst for the oxygen reduction reaction was demonstrated. Nitrogen-enriched carbon powder was synthesized by a solid-phase method consisting of grinding graphene oxide and melamine in a planetary ball mill without any solvents and high-temperature processing. Based on XPS and IR spectroscopy data, it was assumed that the high electrocatalytic activity of the obtained material is due to the presence of nitrogen atoms and quinone groups on its surface.     

Biosynthesis of Nickel oxide Nanoparticles from Euphorbia heterophylla (L.) and their biological application

Nickel oxide Nanoparticles (NiO NPs) were synthesized from E. heterophylla (L.) leaves extract act as reducing/capping agent by biosynthesis process. Further the synthesized NiO NPs was subjected for structural, optical and biological properties. The XRD pattern of NiO NPS exhibit face centred cubic (FCC) crystalline structure. The UV-DR spectrum of biosynthesized NiO NPs exhibited optical properties with well-defined at 321 nm and its exhibits optical band gap is 3.24 eV. The FT-IR spectrum of NiO NPs shows stretching vibration of Ni-O at 452 cm⁻¹. The morphological features of NiO NPs are rhombohedra and slightly agglomerated and then size of the biosynthesized NiO NPs as found in the range of 12–15 nm. The NiO NPs shows vital non-toxic properties on human erythrocytes and its interference in activity coagulation cascade both on PRP and PPP on human blood. The Bactericidal activity of NiO NPs was shows significant inhibitory activity against pathogenic bacterial strains. Further, NiO NPs show significant cytotoxicity against human lung cancer cell line (A549) and human hepatocarcinoma (HepG2) cell lines. Therefore, the study reveals states that, the E. heterophylla (L.) leaves extract is an effective reducing/capping agent for the formation of NiO NPs and its exhibits biological properties.     

The ladder towards understanding the oxygen evolution reaction

Understanding the atomic-scale mechanistic details of the oxygen evolution reaction (OER) remains an unresolved challenge in electrochemistry owing to the complexity of the OER. In this short review we discuss how, with the advent of new experimental and computational methodologies, the OER can be treated with increasingly sophisticated models to aid in our complete understanding. For the case of steady state catalyst surfaces, we define a six-rung ladder of complexity to frame how far this understanding reaches and in which aspects our understanding could still improve.     

Iron and cobalt oxide and metallic nanoparticles prepared from ferritin

Metallic Fe and Co and Fe- and Co-based oxide nanoparticles were prepared by a novel method utilizing the biologically relevant protein ferritin. In particular, iron and cobalt oxyhydroxide nanoparticles were assembled within horse spleen and Listeria innocua derived ferritin, respectively, in the aqueous phase. Ferritin containing either Fe or Co oxide was transferred and dried on a SiO2 support where the protein shell was removed during exposure to a highly oxidizing environment. It was also shown that the metal oxide particles could be reduced to the respective metal by heating in hydrogen. X-ray photoelectron spectroscopy was used to characterize the composition of the particles and atomic force microscopy was used to characterize the size of the nanoparticles. Depending on the Fe or Co loading and/or type of ferritin used, metallic and oxide nanoparticles could be produced within a range of 20-60 A.