磁性荧光双功能复合纳米粒子Fe3O4@SiO2@ZrO2:Tb3+的合成和表征

通过原位反应合成法成功合成了一种新型水溶性的磁性荧光复合纳米粒子Fe₃O₄@SiO₂@ZrO₂:Tb³⁺,并通过扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)、红外光谱仪(FT-IR)、磁性测试仪和荧光(PL)光谱对其形貌、尺寸、相组成、磁性和荧光性能进行了表征。 结果表明,核(Fe₃O₄@SiO₂)壳(ZrO₂:Tb³⁺)结构组成的磁性荧光复合纳米粒子具有超顺磁性,其饱和磁化强度达到36 emu/g,并且在494 nm(⁵D₄→⁷F₆)、549 nm(⁵D₄→⁷F₅)、587 nm(⁵D₄→⁷F₄)和625 nm(⁵D₄→⁷F₃)处具有4个Tb³⁺特有的荧光发射光谱带峰值。 磁性荧光双功能的复合纳米粒子在生物医学领域具有潜在的应用价值。     

锌活化Fe/Co/N掺杂的生物质碳基高效氧还原催化剂

为了推动清洁能源-燃料电池的广泛应用, 迫切需要研发成本低、 原料来源广泛的过渡金属基高效氧还原反应(ORR)催化材料, 来替代目前使用的贵金属铂基催化材料. 本文以铁和钴等非贵金属离子作为催化材料的主要活性位点, 通过金属-羧基/羟基螯合键原位预锚定在具有三维(3D)孔道结构、 富含羧基和羟基以及极易在水溶液中形成凝胶网络的海洋生物质材料海藻酸钠上, 经冷冻干燥得到气凝胶; 然后通过高温碳化, 得到活性位点均匀分布在具有多级孔结构的碳骨架中的高活性、 高稳定的Co/Zn/Fe/N@bio-C-2氧还原催化剂材料, 该催化剂包含2种不同的铁基活性材料(Fe₂O₃和Fe)以及2种不同的钴基活性材料(CoO和Co).利用硝酸锌作为活化剂来改善催化材料的孔道结构, 使制备碳材料的总面积从149.3 m²/g增加到325.3 m²/g. 通过一系列对比实验发现, Fe/Co双活性位点与合适比表面积的协同作用使得Co/Zn/Fe/N@bio-C-2获得了最佳的ORR催化活性.其在0.1 mol/L KOH溶液中起始电位达到0.99 V, 半波电位可达0.87 V.     

电化学合成纳米材料和小分子材料在电解制氢领域的应用

氢气是一种清洁、高效、可再生的新型能源,并且是未来碳中和能源供应中最具潜力的化石燃料替代品。因此,可持续氢能源制造具有极大的吸引力与迫切的需求,尤其是通过清洁、环保、零排放的电解水方法。然而,目前的电解水反应受到其缓慢的动力学以及低成本/能源效率的制约。在这些方面,电化学合成通过制造先进的电催化剂和提供更高效/增值的共电解替代品,为提高水电解的效率和效益提供了广阔的前景。它是一种环保、简单的通过电解或其他电化学操作,对从分子到纳米尺度的材料进行制造的方法。本文首先介绍了电化学合成的基本概念、设计方法以及常用方法。然后,总结了电化学合成技术在电解水领域的应用及进展。我们专注于电化学合成的纳米结构电催化剂以实现更高效的电解水制氢,以及小分子的电化学氧化以取代电解水制氢中的析氧共反应,实现更高效、 增值的共电解制氢。我们系统地讨论了电化学合成条件与产物的关系,以启发未来的探索。最后,本文讨论了电化学合成在先进电解水以及其他能量转换和储存应用方面的挑战和前景。     

Highly Active Electrocatalyst Derived from ZIF-8 Decorated with Iron(III) and Cobalt(III) Porphyrin Toward Efficient Oxygen Reduction in Both Alkaline and Acidic Media

Zeolite imidazole frameworks 8(ZIF-8) and modified ones after pyrolysis are highly promising toward oxygen reduction reaction(ORR). Especially, the compositional modification of ZIF-8 is crucial to the enhancement of ORR performance, yet limited to the substitution of skeletal Zn(II) with other cations or simple physical adsorption of cations. Herein, we report the decoration of ZIF-8 with ORR active hemin(FeP) and Co(III) protoporphyrin(CoP) via the coordination between the peripheral carboxylic group of FeP and CoP with skeletal Zn(II). This allows well control over the quantity of loaded FeP and CoP, critical to the synthesis of advanced electrocatalysts. Subsequent pyrolysis of FeP and CoP co-decorated ZIF-8 leads to highly active ORR electrocatalysts with a half-wave potential(E_1/2) of 0. 913 V(vs. RHE) in 0.1 mol/L KOH aq. and an E_1/2 of 0.803 V(vs. RHE) in 0.1 mol/L HClO₄ aq. Moreover, our electrocatalyst shows much more improved and comparable durability in alkaline and acidic media, respectively, during 3000 cycles of cyclic voltammetry(CV) scanning relative to commercial Pt/C.     

Research on Preparation Methods of Carbon Nanomaterials Based on Self-Assembly of Carbon Quantum Dots

Here, based on self-assembly of carbon quantum dots (CDs), an innovative method to prepare nanomaterials under the action of a metal catalyst was presented. CDs were synthesized by a one-step hydrothermal method with citric acid (CA) as the carbon source, ethylenediamine (EDA) as the passivator and FeSO₄•7H₂O as the pre-catalyst. In the experiment, it was found that the nano-carbon films with a graphene-like structure were formed on the surface of the solution. The structure of the films was studied by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR), etc. The results demonstrated that the films were formed by the self-assembly of CDs under the action of the gas–liquid interface template and the metal catalyst. Meanwhile, the electrochemical performance of the films was evaluated by linear cyclic voltammetry (CV) and galvanostatic charge discharge (GOD) tests. In addition, the bulk solution could be further reacted and self-assembled by reflux to form a bifunctional magnetic–fluorescent composite material. Characterizations such as X-ray diffractometer (XRD), fluorescence spectra (FL), vibrating sample magnetometer (VSM), etc. revealed that it was a composite of superparamagnetic γ-Fe₂O₃ and CDs. The results showed that self-assembly of CDs is a novel and effective method for preparing new carbon nanomaterials.     

Synthesis of α,ω‐di(iodo)PVC and of four‐arm star PVC with identical active chain ends by SET‐DTLRP of VC initiated with bifunctional and tetrafunctional initiators

Na₂S₂O₄‐catalyzed single‐electron transfer – degenerative chain transfer‐mediated living radical polymerization (SET‐DTLRP) of VC initiated with the bifunctional initiators 1,2‐bis(iodopropionyloxy)ethane, dimethyl 2,5‐diiodohexanedioate, and bis(2‐methoxyethyl)‐2,5‐diiodohexanedioate as well as the tetrafunctional initiator pentaerythritol tetrakis(2‐iodopropionate) is reported. This SET‐DTLRP was performed in water at ambient temperature in the presence of polyvinyl alcohol and hydroxypropyl methylcellulose surfactants and provides methods for the synthesis of α,ω‐di(iodo)PVC with two identical active chain ends and of four‐arm star PVC with four identical active chain ends. These difunctional and tetrafunctional derivatives of PVC are also macroinitiators for the synthesis of ABA triblock copolymers and four‐arm star block copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 635–652, 2009     

C_9N_4 as excellent dual electrocatalyst: A first principles study

We perform first principles calculations to investigate the catalytic behavior of C_9 N_4 nanosheet for water splitting.For the pristine C_9 N_4,we find that,at different hydrogen coverages,two H atoms adsorbed on the 12-membered ring and one H atom adsorbed on the 9-membered ring show excellent performance of hydrogen evolution reaction(HER).Tensile strain could improve the catalytic ability of C_9 N_4 and strain can be practically introduced by building C_9 N_4/BiN,and C_9 N_4/GaAs heterojunctions.We demonstrate that the HER performance of heterojunctions is indeed improved compared with that of C_9 N_4 nanosheet.Anchoring transition metal atoms on C_9 N_4 is another strategy to apply strain.It shows that Rh@C_9 N_4 exhibits superior HER property with very low Gibbs free energy change of-30 meV.Under tensile strain within ～2%,Rh@C_9 N_4 could catalyze HER readily.Moreover,the catalyst Rh_9 C_9 N_4 works well for oxygen evolution reaction(OER)with an overpotential of 0.58 V.Our results suggest that Rh@C_9 N_4 is favorable for both HER and OER because of its metallic conductivity,close-zero Gibbs free energy change,and low oneset overpotential.The outstanding performance of C_9 N_4 nanosheet could be attributed to the tunable porous structure and electronic structure compatibility.     

Reverse micelle synthesis of perovskite oxide nanoparticles

La_0.6Sr_0.4Co_xFe_1−xO_3−δ (LSCF), La_0.6Sr_0.4Cu_0.2Fe_0.8O_3−δ, Ba_0.5Sr_0.4Co_0.8Fe_0.2O_3−δ and LaFeO_3−δ nanoparticles were synthesized by a reverse micelle procedure. Controlling the size of the micelles through the water:oil phase ratio enabled synthesis of phase pure perovskite particles with average sizes from 14 nm to 50 nm. Small amounts of an impurity phase, likely cobalt oxide, were detected in the XRD spectrum of high cobalt content samples of LSCF (x = 0.8). La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ nanoparticles were utilized to coat the surface of a dense thin-film La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ solid oxide fuel cell cathode. The polarization resistance of the nanoparticle coated electrode, measured at open circuit in air at 973 K, was 20% lower than an equivalent un-coated electrode.