Reactivity and Lability Modulated by a Valence Electron Moving in and out of 25-Atom Gold Nanoclusters

The emergence of atomically precise metal nanoclusters with unique electronic structures provides access to currently inaccessible catalytic challenges at the single-electron level. We investigate the catalytic behavior of gold Au₂₅(SR)₁₈ nanoclusters by monitoring an incoming and outgoing free valence electron of Au 6s¹. Distinct performances are revealed: Au₂₅(SR)₁₈⁻ is generated upon donation of an electron to neutral Au₂₅(SR)₁₈⁰ and this is associated with a loss in reactivity, whereas Au₂₅(SR)₁₈⁺ is generated from dislodgment of an electron from neutral Au₂₅(SR)₁₈⁰ with a loss in stability. The reactivity diversity of the three Au₂₅(SR)₁₈ clusters stems from different affinities with reactants and the extent of intramolecular charge migration during the reactions, which are closely associated with the valence occupancies of the clusters varied by one electron. The stability difference in the three clusters is attributed to their different equilibria, which are established between the AuSR dissociation and polymerization influenced by one electron.     

“非保护型”金属胶体纳米簇形成机理研究

碱-乙二醇法制备的"非保护型"金属及合金纳米簇由表面吸附的溶剂分子和简单离子实现稳定化,它们被广泛用于制备高性能复相催化剂和研究复相催化剂中的尺寸、组成、载体表面基团以及修饰剂对催化性能的影响。关于此类非保护金属纳米簇的形成过程及机理的认识尚有待进一步深化。本文采用原位快速扫描X射线吸收精细结构谱(QXAFS)、原位紫外-可见(UV-Vis)吸收光谱、透射电子显微镜和动态光散射技术研究了碱-乙二醇法合成中非保护型金属胶体纳米簇的形成过程与机理。结果表明,在碱-乙二醇法合成非保护型Pt金属纳米簇的过程中,室温下即有部分Pt(IV)被还原至Pt(II)。随着反应温度的升高,OH-逐渐取代与Pt离子配位的Cl-,在Pt―Pt键形成之前,反应体系的UV-Vis吸收光谱中可观察到明显的纳米粒子的散射信号,原位QXAFS分析表明Pt纳米簇是由Pt氧化物纳米粒子还原所形成的;在Ru金属纳米簇的形成过程中,OH-首先取代了Ru Cl_3中的Cl~-,形成羟基配合物Ru(OH) _6~(3-),后者进一步缩合形成氧化钌纳米粒子,最终Ru金属纳米簇由乙二醇还原氧化钌纳米粒子形成。由于先形成了氧化物纳米粒子,后续的还原反应被限制在氧化物纳米粒子内,使最终得到的非保护型金属纳米簇具有尺寸小、分布窄的特点。本工作所获得的知识对发展高性能能源转化催化剂、精细化学合成催化剂、传感器等功能体系具有重要意义。     

纳米银/二维石墨相氮化碳/还原氧化石墨烯复合材料的制备及其光催化降解抗生素

为优化石墨相氮化碳(g-C₃N₄)光催化剂的结构,改善其对污染物的降解性能,本文以三聚氰胺为前驱体,通过高温煅烧和热氧化剥离制备了二维石墨相氮化碳(2D-C₃N₄),并用光还原法一步合成纳米银/二维石墨相氮化碳/还原氧化石墨烯(Ag/2D-C₃N₄/rGO)复合光催化剂。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、光致发光光谱(PL)、X射线光电子能谱(XPS)、氮气吸附脱附等温曲线(BET)等对材料进行表征。 以头孢曲松钠为目标污染物,探究pH值、催化剂用量、头孢曲松钠初始浓度等因素对催化剂的吸附、降解性能的影响,并探究降解反应机理。 当pH=6.0,催化剂用量为0.3 g/L,头孢曲松钠初始浓度为10.0 mg/L时,复合材料对头孢曲松钠的降解率可达到89.1%。 催化剂的稳定性较强,具有实际应用价值,可用于处理含头孢类抗生素的废水。     

银纳米簇荧光探针检测L-半胱氨酸

常温下合成了二氢硫辛酸(DHLA)包裹的银纳米簇(AgNCs),并基于L-半胱氨酸对AgNCs的荧光猝灭现象构建了AgNCs荧光探针对Cys的检测方法。结果表明,在优化条件下,AgNCs的荧光猝灭程度和Cys浓度在2.0~100μmol/L范围内呈现良好的线性关系(R2=0.998),检出限为1.77μmol/L(S/N=3)。在人体血清样品中Cys检测的加标回收率为94.0%~102.4%。     

Ag3PO4量子点/石墨相氮化碳纳米片复合光催化剂的制备及其对苯甲醇选择性氧化活性

以热氧化剥离法得到的超薄石墨相氮化碳(g-C₃N₄)纳米片为载体,首次在室温条件下,制备了系列Ag₃PO₄量子点/g-C₃N₄纳米片复合光催化剂;通过透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、紫外-可见漫反射光谱(UV-Vis DRS)、荧光光谱(PL),对复合光催化剂的形貌、结构和光学性质进行了表征,考察了系列光催化剂对苯甲醇的光催化选择性氧化性能。 结果表明,粒径为3~5 nm Ag₃PO₄颗粒均匀分散g-C₃N₄纳米片上,结晶度良好。 以乙腈为溶剂时,当m(Ag₃PO₄)/m(g-C₃N₄)=0.6时,苯甲醇具有32.1%的最大转化率,对产物苯甲醛具有90%的最高选择性;活性物种捕捉实验结果表明,该催化氧化反应的主要活性物是光生空穴的氧化作用,能带计算结果表明,该复合催化剂结构具有合适的苯甲醇的氧化电位而选择性生成苯甲醛。     

多尺度Ag/CuO复合光热材料的制备及在海水淡化中的应用

采用原位化学反应和热处理相结合的策略,在泡沫铜表面形成丝线状与花瓣状的立体无机物阵列,然后在其表面蒸镀Ag纳米颗粒(NPs),成功制备了基于泡沫铜的Ag/CuO复合光热材料。该复合材料因表面三维立体阵列结构以及Ag NPs而具备较高的太阳光吸收率。故而,Ag/CuO复合光热材料结合三聚氰胺泡沫组成的蒸发器件实现了高效的海水淡化。本研究除了探索光陷阱深度和金属掺杂对吸收体光热转换效率增强之外,还搭建了太阳能驱动界面蒸汽生成测试系统,测试了样品的光热蒸发性能。在1倍太阳(1 kW·m~(-2))辐照下,该器件整体蒸发速率高达1.097 6 kg·m~(-2)·h~(-1),即其蒸发效率可达78.38%。     

介孔SBA-15棒负载的Pd3Cl催化剂催化Sonogashira偶联反应（英文）

通过静电吸引策略将具有高度分散性的原子精确纳米团簇[Pd3Cl(PPh2)2(PPh3)3]+(Pd3Cl)负载在介孔SBA-15棒上。结构明确的Pd3Cl/SBA-15催化剂在以水作为溶剂以及温和的反应条件下对催化Sonogashira碳-碳偶联反应展现了较好的催化性能以及循环性。在此基础上,我们研究了Pd3Cl团簇结构与性能之间的关系,并证实内核的Pdδ+(0<δ<2)与配体之间的协同效应是催化反应的关键。     

Synthesis of Z-scheme g-C3N4 nanosheets/Ag3PO4 photocatalysts with enhanced visible-light photocatalytic performance for the degradation of tetracycline and dye

Graphene-like C3N4/Ag3PO4 photocatalysts are synthesized by calcination and solutions precipitating method.The obtained g-C3N4/Ag3PO4 composites display excellent photocatalytic activity for the degradation of methylene orange(MO),rhodamine B(RhB)and tetracycline(TC)under visible light irradiation.The solutions containing RhB(10 mg/L)and MO(10 mg/L)can be efficiently degraded within15 min and 30 min.Especially,nearly 80%of TC(50 mg/L)is degraded within 20 min.which are much better than those of pure g-C3N4 nanosheets and Ag3PO4,implying that strong interaction and reasonable energy band alignment in the contact interface can effectively transfer the carries.Furthermore,the g-C3N4/Ag3PO4 composites exhibit the improved stability,and only a slight decrease is observed after three recycling runs.Moreover,the impact of inorganic ions and PH values on the degradation performance is rather small.The Z-scheme photocatalytic mechanism of the g-C3N4/Ag3PO4 composites based on the active species trapping experimental is proposed.This work demonstrates the promising applications of the g-C3N4/Ag3PO4 composites in environmental issues.     

纳米银刻蚀比色法检测褪黑激素

该文构建了一种基于氯金酸刻蚀球形纳米银检测褪黑激素的简单、高灵敏比色探针。纳米银可被氯金酸氧化刻蚀为Ag+,同时还原生成的纳米金沉积在刻蚀后的纳米银表面,导致其溶液的吸光度降低和颜色增强(由黄色变为橘黄色)。当向体系中加入褪黑激素时,氯金酸被还原,抑制了纳米银的刻蚀,从而使得溶液吸光度增加和颜色变浅。结果显示,在0.1 nmol/L~1.0 mmol/L范围内,褪黑激素浓度对数值(lgC)与其吸光度改变值(ΔA)呈良好的线性关系,线性方程为ΔA=0.049 8+0.516lgC,相关系数(R2)为0.996 4,检出限为0.09 nmol/L。该方法成功应用于人体尿液和葡萄中的褪黑激素的测定。     

Unraveling the Impact of Gold(I)–Thiolate Motifs on the Aggregation‐Induced Emission of Gold Nanoclusters

Aggregation‐induced emission (AIE) provides an efficient strategy to synthesize highly luminescent metal nanoclusters (NCs), however, rational control of emission energy and intensity of metal NCs is still challenging. This communication reveals the impact of surface Au^I‐thiolate motifs on the AIE properties of Au NCs, by employing a series of water‐soluble glutathione (GSH)‐coordinated Au complexes and NCs as a model ([Au₁₀SR₁₀], [Au₁₅SR₁₃], [Au₁₈SR₁₄], and [Au₂₅SR₁₈]^?, SR=thiolate ligand). Spectroscopic investigations show that the emission wavelength of Au NCs is adjustable from visible to the near‐infrared II (NIR‐II) region by controlling the length of the Au^I‐SR motifs on the NC surface. Decreasing the length of Au^I‐SR motifs also changes the origin of cluster luminescence from AIE‐type phosphorescence to Au⁰‐core‐dictated fluorescence. This effect becomes more prominent when the degree of aggregation of Au NCs increases in solution.