这项工作主要由国家科学基金会 (NSF) 资助, 化学司 (奖项编号 CHE-1507370) 得到承认。在3M 的非终身教师奖中, 他和文汇李承认部分财政支持。这项研究使用了先进的光子源 (光束线 12-C, 用户建议 GUP-45774) 的资源, 美国能源部 (能源部) 在阿贡国家实验室为能源部科学办公室操作的合同号。DE-AC02-06CH11357。作者想感谢弗吉尼亚理工大学化学工程系的博士 Yubing, 他对 SAXS 测量的帮助。所提出的工作部分是在综合纳米技术公司中心执行的, 一个科学用户设施办公室为美国能源部科学办公室操作。洛斯阿拉莫斯国家实验室, 一个平权行动平等机会雇主, 由洛斯阿拉莫斯国家安全有限责任公司管理, 为美国能源部国家核安全管理局根据合同 DE-AC52-06NA25396。

1. 醋酸钯再结晶
注意: 此协议涉及使用高温玻璃器皿和解决方案的动手操作。使用个人防护设备, 包括护目镜和耐热手套。所有涉及解决方案处理的操作都应在通风罩中进行, 并避免由于无水乙酸的腐蚀性和易燃性质而在附近的其他热源。
<ol><li>将40毫升无水乙酸加入50毫升三颈圆底烧瓶, 0.75 克醋酸钯和搅拌棒。将冷凝器连接到中间颈部, 盖上其他两个开口, 并将烧瓶固定在搅拌板上。</li>
	<li>慢慢打开冷凝水阀, 让水流流经冷凝器。在室温300转时搅拌溶液10-15 分钟, 直到没有更多的醋酸钯能溶解。</li>
	<li>将热板温度设置为摄氏100摄氏度。温度达到100摄氏度后, 等待30分钟左右, 直到醋酸钯完全溶解。</li>
	<li>在此期间, 预加热两个20毫升玻璃瓶和所有的过滤部分在90°c 在烘干烤箱。另外, 在500毫升烧杯中加热一些水, 直到它接近沸点为止。</li>
	<li>快速组装过滤部件, 并将过滤器瓶放在预热的热板上 (摄氏100摄氏度)。将真空泵与滤瓶连接。快速从热板中取出三颈圆底烧瓶, 在真空下过滤醋酸钯溶液。</li>
	<li>过滤后, 迅速将液体倒入两个20毫升的瓶子。把瓶子盖上, 把它们浸入烧杯中的热水中。</li>
	<li>把烧杯放在80摄氏度的热板上, 慢慢地将温度降低到室温, 每小时将加热板温度降低20摄氏度。</li>
	<li>3小时后关闭热板, 让烧杯一夜之间结晶。</li>
	<li>把醋酸从瓶子里倒出来。把醋酸钯三聚体晶体放在瓶子里。清洗晶体3次, 以去除乙酸残留物, 将2毫升的己烷均匀地分配到晶体上, 然后排出溶液。</li>
	<li>用铝箔盖住瓶子以避免光线。在室温下将2的晶体干燥一夜。将水晶储存在惰性大气中。</li>
</ol>2. 醋酸钯的制备–顶部合成溶液14
<ol><li>德加每个溶剂 (吡啶, 甲苯或 1-hexanol) 在 N2流动在10毫升/分钟30分钟。</li>
	<li>在7毫升瓶中, 对2.5 毫升20毫米溶液中的0.0112 克醋酸盐进行重结晶。将瓶子盖上, 然后用插入的针出口在隔膜的入口上清除并填充 N2 。</li>
	<li>将溶剂和醋酸钯瓶转化为 N2 glovebox。在醋酸钯瓶中加入2.5 毫升的吡啶或甲苯。油脂实验瓶40分钟溶解所有醋酸钯。</li>
	<li>对于每个样品, 将1毫升20毫米的醋酸钯溶液转化为7毫升的小瓶, glovebox 中有一个微搅拌条。添加 8.9 ul 的 trioctylphosphine (顶部: Pd 摩尔比 = 2) 到解决方案。三十年代用手摇瓶, 混合剂好。然后, 在每个样品瓶中加入1毫升的 1-hexanol (溶剂: hexanol = 50:50 的体积)。</li>
</ol>3. 胶体钯纳米粒子合成14
<ol><li>预热的热板加热插入100摄氏度。清除反应瓶的10毫升/分钟的2以上流动超过溶液水平, 创造一个惰性的气氛和恒定的压力。</li>
	<li>将反应瓶放在预加热的热板内插入 300 rpm 搅拌开始反应。</li>
	<li>要终止反应, 从插入物中取出瓶子, 将瓶子冷却到室温。</li>
</ol>4. Pd 纳米粒子表征-原位小角 X 射线散射 (SAXS)34
<ol><li>平均尺寸和尺寸分布特征
	<ol>
<li>初始化 SAXS 仪器。单击测量软件中的 "指挥官" 窗口, 分别调整电压和电流至50伏和1000µA。</li>
		<li>加载背景溶液 (1:1 混合物的溶剂 (吡啶或甲苯) 和 1-hexanol) 到毛细管持有人。将毛细管密封并固定在与 X 方向平行的支架上。将支架安装在仪表箱内。</li>
		<li>启动真空泵并等待, 直到真空水平在房间稳定 (低于0.3 毫巴)。</li>
		<li>固定 x 轴 (沿毛细管) 和扫描在 Y 方向 (横跨毛细管), 以找到中间位置作为测量位置, X 射线路径长度通过液体样品达到最大 (毛细管直径)。</li>
		<li>安装并运行向导以执行步骤 4.1.5-4.1.8。设置毛细管位置, 并通过 x 射线通道安装玻碳, 使 x 射线将通过玻璃碳首先, 然后毛细管。采取十年代的测量和保存2D 散射图。</li>
		<li>将玻璃碳移出通路。对背景溶液进行十九世纪年代的测量, 并保存背景散射图。</li>
		<li>将毛细管移出通路, 只安装玻碳, 并采取十年代测量。</li>
		<li>将玻璃碳移出通路。采取黑色电流的十年代测量 (仅真空室)。</li>
		<li>要测量纳米微粒溶液, 将样品装入毛细管中, 并遵循与 4.1.2-4.1.6 相同的步骤。</li>
		<li>对于数据分析, 通过文件打开 SAXS 分析软件|从文件导入| 导入背景和示例文件。</li>
		<li>选择背景的2D 模式。单击工具中的间接传输计算。输入的背景与玻碳, 玻碳和空白框架文件, 并点击OK。对示例模式执行相同的操作。传输将自动计算。</li>
		<li>将圆环光标从边缘拖动到2D 散射图案的中心, 将背景和2D 图样本与1D 散射曲线结合起来。</li>
		<li>在列表中选择背景曲线。在SAXS 信息中作为背景测量进行检查。</li>
		<li>选择背景和示例曲线一起。右键单击并选择背景校正以从示例中减去背景。</li>
		<li>在背景校正后右键单击曲线。选择SAXS 建模 |直接建模 |球形 |舒尔茨 |没有互动。</li>
		<li>将 Q 范围设置为0.02 到0.3 之间。单击初始猜测, 对拟合结果进行估计。然后点击合适的适合 1D SAXS 曲线与舒尔茨多分散球模型, 以获得平均直径<img alt="Equation 01" src="/files/ftp_upload/57667/57667eq1v3.jpg">和标准偏差<img alt="Equation 02" src="/files/ftp_upload/57667/57667eq2v3.jpg"> (对应的大小分布的纳米粒子)。</li>
	</ol></li>
	<li>颗粒浓度 (<img alt="Equation 03" src="/files/ftp_upload/57667/57667eq3v3.jpg">) 萃取
	<ol>
<li>使用<img alt="Equation 04" src="/files/ftp_upload/57667/57667eq4v3.jpg">绝对强度 (), 它可以与溶液中纳米粒子的大小和浓度相关联, 如以下14,35: <img alt="Equation 05" src="/files/ftp_upload/57667/57667eq5v3.jpg"> 在<img alt="Equation 06" src="/files/ftp_upload/57667/57667eq6v3.jpg">哪里是散射矢量, Np 是纳米粒子的浓度, <img alt="Equation 07" src="/files/ftp_upload/57667/57667eq7v3.jpg">是纳米粒子的体积, <img alt="Equation 08" src="/files/ftp_upload/57667/57667eq8v3.jpg">是单粒子的形式因子。用以下表达式计算多分散球形纳米粒子的舒尔茨分布因子36 <img alt="Equation 09" src="/files/ftp_upload/57667/57667eq9v3.jpg"> </img> : <img alt="Equation 10" src="/files/ftp_upload/57667/57667eq10v3.jpg"> 这里<img alt="Equation 11" src="/files/ftp_upload/57667/57667eq11v3.jpg">。</li>
		<li>考虑<img alt="Equation 06" src="/files/ftp_upload/57667/57667eq6v3.jpg"> → 0, 这是 SAXS 曲线的外推到 Y 轴的截距: <img alt="Equation 12" src="/files/ftp_upload/57667/57667eq12v3.jpg"> ∆<img alt="Equation 13" src="/files/ftp_upload/57667/57667eq13v3.jpg"> </img>是金属与溶剂之间的散射长度密度差, <img alt="Equation 14" src="/files/ftp_upload/57667/57667eq14v3.jpg">是粒子体积的平均平方。</li>
		<li>使用<img alt="Equation 14" src="/files/ftp_upload/57667/57667eq14v3.jpg">等式计算: <img alt="Equation 15" src="/files/ftp_upload/57667/57667eq15v3.jpg">
</li>
		<li>为了获得<img alt="Equation 16" src="/files/ftp_upload/57667/57667eq16v3.jpg"> </img>, 使用水 (作为标准) 校准的散射强度为绝对尺度由于其众所周知的绝对差分散射截面的 1.632×10-2 cm-1在室温34。测量空毛细管和水, 并减去空毛细管作为背景水后的过程从4.1.2 到4.1.14。</li>
		<li>水的1D 散射曲线是一条平行于 X 轴的直线。推断直线以获取 Y 轴上的<img alt="Equation 17" src="/files/ftp_upload/57667/57667eq17v3.jpg">截距强度 (厘米-1)。计算校准系数 (CF) 作为 <img alt="Equation 18" src="/files/ftp_upload/57667/57667eq18v3.jpg">.</li>
		<li>找出纳米粒子曲线<img alt="Equation 19" src="/files/ftp_upload/57667/57667eq19v3.jpg">的外推强度。校准<img alt="Equation 19" src="/files/ftp_upload/57667/57667eq19v3.jpg"> , 以<img alt="Equation 16" src="/files/ftp_upload/57667/57667eq16v3.jpg">获得在绝对规模使用 CF: <img alt="Equation 20" src="/files/ftp_upload/57667/57667eq20v3.jpg">
</li>
		<li>从 (3) 派生的以下方程中提取粒子的浓度: <img alt="Equation 21" src="/files/ftp_upload/57667/57667eq21v3.jpg">
</li>
	</ol></li>
	<li><img alt="Equation 22" src="/files/ftp_upload/57667/57667eq22v3.jpg">原位和原位SAXS萃取纳米粒子中原子的浓度
	<ol>
<li>使用纳米粒子的浓度 (<img alt="Equation 59" src="/files/ftp_upload/57667/57667eq59v3.jpg">) 和每个纳米粒子 (N大道) 原子数的平均值来计算原子的总浓度, 如下所述。</li>
		<li>根据以下等式计算 N大道37: <img alt="Equation 24" src="/files/ftp_upload/57667/57667eq24v3.jpg"> 其中r是纳米粒子半径, <img alt="Equation 25" src="/files/ftp_upload/57667/57667eq25v3.jpg">是阿佛加德罗的数量, ρ是金属密度, <img alt="Equation 26" src="/files/ftp_upload/57667/57667eq26v3.jpg">是金属分子量。为钯, ρ = 12023 公斤/米3并且<img alt="Equation 26" src="/files/ftp_upload/57667/57667eq26v3.jpg"> = 0.1064 公斤或摩尔。</li>
		<li>为解释纳米粒子中原子总浓度的大小分布, 计算<img alt="Equation 27" src="/files/ftp_upload/57667/57667eq27v3.jpg">使用方程 (7) 以及舒尔茨分布因子: <img alt="Equation 28" src="/files/ftp_upload/57667/57667eq28v3.jpg">
</li>
		<li>通过在任何给定时间乘以<img alt="Equation 29" src="/files/ftp_upload/57667/57667eq29v3.jpg"> <img alt="Equation 27" src="/files/ftp_upload/57667/57667eq27v3.jpg">纳米粒子 (<img alt="Equation 59" src="/files/ftp_upload/57667/57667eq59v3.jpg">) 的浓度来估计原子的浓度 (), 如下所示: <img alt="Equation 30" src="/files/ftp_upload/57667/57667eq30v3.jpg">
</li>
	</ol></li>
</ol>5. 同步辐射胶体钯纳米粒子合成原位SAXS 动力学数据的获取
<ol><li>在开始反应之前, 采取 SAXS 测量空毛细管, 毛细管充满水, 和毛细管填充溶剂: hexanol 在50:50。</li>
	<li>考虑到原位SAXS 的代理准备程序与步骤1和2相同, 但总反应溶液体积为6毫升 (10 毫米 Pd (华侨)2毫升吡啶或甲苯混合3毫升 3-hexanol, 顶部: Pd 摩尔比 = 2)。</li>
	<li>在 glovebox 中, 将反应溶液转化为25毫升的圆底烧瓶, 里面有一个搅拌棒。用 N2 (10 毫升/分钟) 清除解决方案上方的空间。</li>
	<li>设置搅拌速度为 300 rpm。把瓶子放在预热的热板内插入, 以触发反应。</li>
	<li>采取 300 ul 的反应溶液进入毛细管安装通过 X 射线光束路径每 8 s 使用程控注射器泵。通过探测器收集散射数据。 注: 样品的传输由电离室直接测量 (不含玻碳)。每次测量后, 溶液被泵回散装反应器。</li>
	<li>考虑数据可以自动转换为1D 曲线与光束线程序。用舒尔茨多分散球模型拟合数据, 得到了平均直径和标准差。在步骤4.2 中, 利用同步辐射 X 射线对粒子浓度的提取遵循相同的步骤。</li>
</ol>6. 钯 (Pd) 金属纳米粒子成核和生长的建模方法和模拟程序
<ol><li>将还原和成核视为一阶伪初等反应 (方程 (10))。 注意: 一个伪初等反应被定义为一个 (或更多) 缓慢的基本反应的总和, 其次是快速的基本反应 (非速率决定反应)。在此, 伪基本反应代表了慢反应的动力学, 但有反应顺序等于总和反应的计量学 (因此, 期限伪初级)38。例如, 相应的反应, pd (华侨)2减少和核 (顶部: Pd 摩尔 ratio=1) 在超过 1-hexanol 被提出低于15: (i) Pd (顶部) (华侨)2(解决) + r ' CH2OH→Pd0 + 顶 + r ' CHO + 2AcOH + 解决 (整体配体离解和还原), 可分为步骤 (ii) 和 (iii): (ii) Pd (顶部) (华侨)2(解决) + 解决→ Pd (华侨)2(解决)2 + 顶部 (配体离解) (iii) Pd (华侨)2(解决)2 + r ' CH2OH→Pd0 + r ' CHO + 2AcOH + (解决)2 (减少) (iv) n Pd0 →Pd0n (成核) 将还原 (iii) 和成核 (iv) 反应组合, 并显示为一个伪初等还原-成核步骤 (A→B)。请注意, A 代表动力学活动前体, 当它被写作为 Pd (华侨)2(解决)2在反应 (iii), 其他 Pd 复合物可能存在。</li>
	<li>考虑纳米粒子的表面生长是可催化的。自催化生长是通过减少纳米粒子表面的前驱体 (方程式 (11))37而产生的一种生长方式。</li>
	<li>用前体 (它改变前体反应性) 以及粒子表面来解释上限配体 (顶部) 的结合。 注: 配体的离解 (反反应 12) 对红外纳米粒子的核化有重要意义39。另外, 其他研究表明, 配体对前驱反应 (反应 12) 以及胶体纳米粒子14、15、16的生长速率有影响。包括这些反应在模型 (等式 (12) 和 (13)) 作为二个可逆的反应 (在反应期间不假设是平衡)14。请注意, 我们的固件机制13 (反应10和 11) 的扩展第一次占配体的可逆约束力与前驱 (反应 12) 和纳米粒子 (反应 13) 的表面。14</li>
	<li>假设以下反应是伪初等的。 <img alt="Equation 31" src="/files/ftp_upload/57667/57667eq31v3.jpg"> <img alt="Equation 32" src="/files/ftp_upload/57667/57667eq32v3.jpg"> <img alt="Equation 34" src="/files/ftp_upload/57667/57667eq34v3.jpg"> <img alt="Equation 35" src="/files/ftp_upload/57667/57667eq35v3.jpg"> 这里<img alt="Equation 36" src="/files/ftp_upload/57667/57667eq36v3.jpg">是还原/成核速率常数, <img alt="Equation 37" src="/files/ftp_upload/57667/57667eq37v3.jpg">表面生长速率常数, <img alt="Equation 38" src="/files/ftp_upload/57667/57667eq38v3.jpg">反应的正反应速率常数 (12), <img alt="Equation 39" src="/files/ftp_upload/57667/57667eq39v3.jpg">配体金属前体结合的平衡常数 (即反应 12),<img alt="Equation 40" src="/files/ftp_upload/57667/57667eq40v3.jpg">反应的正向反应速率常数 (13), 与<img alt="Equation 41" src="/files/ftp_upload/57667/57667eq41v3.jpg">纳米粒子表面的配体结合的平衡常数 (即反应 13)。 注: 此外, A是代表动力学活性前体, L帽配体 (这里顶部), AL ligand–metal 复合体 (这里 Pd (II) –TOP), 可与不同的配位协调 (如醋酸, 1-hexanol 或吡啶), B名额钯表面原子, 和BL的 pd 原子与配体, pd0 –TOP。此外, 请参阅以前的出版物14中的模型描述和假设的完整列表。</li>
	<li>根据下面的方程, 从动力学<img alt="Equation 29" src="/files/ftp_upload/57667/57667eq29v3.jpg">模型中计算 Pd 原子的浓度。 <img alt="Equation 42" src="/files/ftp_upload/57667/57667eq42v3.jpg"></li>
	<li>从模型中计算纳米粒子<img alt="Equation 59" src="/files/ftp_upload/57667/57667eq59v3.jpg">() 的浓度 (如果没有聚集的证据), 如下所示: <img alt="Equation 43" src="/files/ftp_upload/57667/57667eq43v3.jpg"> 在这里<img alt="Equation 44" src="/files/ftp_upload/57667/57667eq44v3.jpg"> , 是反应时间<img alt="Equation 45" src="/files/ftp_upload/57667/57667eq45v3.jpg"> , 活跃前体浓度<img alt="Equation 46" src="/files/ftp_upload/57667/57667eq46v3.jpg"> , 阿佛加德罗的数量 (6.022 x 1023) <img alt="Equation 48" src="/files/ftp_upload/57667/57667eq48v3.jpg">和核大小 (原子/核)。<img alt="Equation 48" src="/files/ftp_upload/57667/57667eq48v3.jpg">根据反应过程中检测到的最小尺寸选择为 "4"。</li>
	<li>利用以下微分方程和初始条件 (MATLAB) 得到不同物种的浓度分布。 微分方程: <img alt="Equation 49" src="/files/ftp_upload/57667/57667eq49v3.jpg"> <img alt="Equation 50" src="/files/ftp_upload/57667/57667eq50v3.jpg"> <img alt="Equation 51" src="/files/ftp_upload/57667/57667eq51v3.jpg"> <img alt="Equation 52" src="/files/ftp_upload/57667/57667eq52v3.jpg"> <img alt="Equation 53" src="/files/ftp_upload/57667/57667eq53v3.jpg"> 此外, 对于金属前驱体和配体浓度 (等式21和 22) 在任何给定的时间 "t", 以下关系可以写成如下: <img alt="Equation 54" src="/files/ftp_upload/57667/57667eq54v3.jpg"> <img alt="Equation 55" src="/files/ftp_upload/57667/57667eq55v3.jpg"> <img alt="Equation 56" src="/files/ftp_upload/57667/57667eq56v3.jpg"> 注意: 反应<img alt="Equation 57" src="/files/ftp_upload/57667/57667eq57v3.jpg">被认为是在 time=0 的平衡。反应后, 反应不再被限制在平衡。 <img alt="Equation 58" src="/files/ftp_upload/57667/57667eq58v3.jpg"></li>
	<li>最小化的SR (i., 规范化平方误差的总和) 之间的实验和模型<img alt="Equation 59" src="/files/ftp_upload/57667/57667eq59v3.jpg">和<img alt="Equation 62" src="/files/ftp_upload/57667/57667eq62v3.jpg">使用 MATLAB 函数 fminsearch 提取拟合参数 (率常数显示在等式 10-13)。 <img alt="Equation 60" src="/files/ftp_upload/57667/57667eq60v3.jpg"> 这里<img alt="Equation 61" src="/files/ftp_upload/57667/57667eq61v3.jpg">是实验数据点的数量。</li>
	<li>选择沿反应时间和 Y 轴 (<img alt="Equation 59" src="/files/ftp_upload/57667/57667eq59v3.jpg"> </img>或<img alt="Equation 62" src="/files/ftp_upload/57667/57667eq62v3.jpg"> </img>) 的数据点个数的相似分布, 以确保在早期或更高的反应时间内, 最小化函数不会加权到数据点。</li>
</ol>7. 从实验数据和模型中获得成核和生长速率
<ol><li>用以下方程计算模型的成核和生长速率。 <img alt="Equation 63" src="/files/ftp_upload/57667/57667eq63v3.jpg"> <img alt="Equation 64" src="/files/ftp_upload/57667/57667eq64v3.jpg"> 在这里,<img alt="Equation 65" src="/files/ftp_upload/57667/57667eq65v3.jpg">[] 表示只贡献粒子生长的原子的浓度。 注: 使成核和生长速率单位相同 (i.、摩尔。L-1. s-1), 需要用 [<img alt="Equation 66" src="/files/ftp_upload/57667/57667eq66v3.jpg">] 乘以等式 (26)。这使我们可以比较的利率。</li>
	<li>利用短时间间隔, 从实验测量的粒子数中估算成核速率。 <img alt="Equation 67" src="/files/ftp_upload/57667/57667eq67v3.jpg">
</li>
	<li>通过从原子的总浓度 (<img alt="Equation 68" src="/files/ftp_upload/57667/57667eq68v3.jpg">) 或金属前驱体消耗中减去核的贡献来估计生长速率。"<img alt="Equation 68" src="/files/ftp_upload/57667/57667eq68v3.jpg">" 量化了粒子 (原子核) 的形成和粒子的生长。 <img alt="Equation 69" src="/files/ftp_upload/57667/57667eq69v3.jpg">
</li>
</ol>

报告没有利益冲突。

在这项研究中, 我们提出了一个强大的方法来检查上限配体对金属纳米粒子的成核和生长的影响。以醋酸钯为金属前驱体和顶部作为配位剂, 合成了不同溶剂 (甲苯和吡啶) 的 pd 纳米颗粒。我们利用原位SAXS 提取还原原子 (成核和生长事件) 的浓度以及纳米粒子 (成核事件) 的浓度, 并将实验观测量用作模型输入。此外, 通过考虑粒子浓度的斜率和原子在早期反应时间的浓度, 我们的方法 (使用...

由于纳米材料在催化、光伏、光子学、传感器、药物输送1、2、3等领域的广泛应用, 金属纳米粒子的控制合成具有重要的意义. 4,5。为了合成具有特定尺寸和粒径分布的纳米粒子, 了解颗粒成核和生长的基本机理至关重要。然而, 获得这种标准的纳米粒子对纳米合成群落提出了挑战, 因为在理解合成机制方面进展缓慢, 而文献中缺乏健壮的动力学模型。在二十世纪五十年代, 拉美提出了硫溶胶的成核和生长模型, 在那里有一个核爆发, 随后是6、7核的扩散控制生长。在该模型中, 假设单体浓度增加 (由于前体的还原或分解), 一旦水平高于临界过饱和度, 就可以克服粒子核的能量屏障,产生爆裂成核 (均质成核)。由于所提出的爆破成核, 单体浓度下降, 当它低于临界过饱和水平时, 成核停止。其次, 通过单体向纳米粒子表面扩散, 形成的核被假定生长, 而不会发生额外的成核事件。这就有效地分离出成核和生长的时间, 并控制在生长过程中的大小分布8。该模型用于描述不同纳米粒子的形成, 包括 Ag9、Au10、CdSe11和 Fe3O412。然而, 一些研究表明, 经典的核化理论 (碳纳米管) 不能描述胶体纳米粒子的形成, 特别是金属纳米粒子, 其中的核和生长的重叠观察1, 13,14,15,16,17。在其中一项研究中, Watzky 和 Finke 建立了两个步骤的机制, 形成铱纳米粒子13, 其中一个缓慢的连续核重叠与快速纳米粒子表面生长 (在那里增长是自催化)。对不同类型的金属纳米粒子, 如 Pd14、15、18、Pt19、20和 Rh 21, 也观察到了缓慢的成核和快速的自催化生长. ,22。尽管最近发展成核和生长模型1,23,24,25, 配体的作用在建议的模型经常被忽略。然而, 配体被显示影响纳米粒子的大小 14,15,26和形态学 19,27以及催化活性和选择性28,29. 例如, 杨等。30控制了 Pd 纳米粒子的大小, 范围从9.5 和 15 nm, 通过改变 trioctylphosphine 的浓度 (顶部)。在磁性纳米粒子 (Fe3O4) 的合成中, 当配体 (胺) 与金属前驱体比从1增加到60时, 其大小明显地从11降到 5 nm。有趣的是, 铂纳米粒子的大小被证明对链长度的胺配体 (e., n-己和胺), 在那里可以获得更小的纳米粒度, 可利用较长的链 (i. e.,胺)31。
不同浓度和不同类型的配体所引起的尺寸变化是配体在成核和生长动力学中贡献的明显证据。不幸的是, 很少有研究表明配体的作用, 在这些研究中, 为了简单起见, 通常会做出几个假设, 这反过来又使这些模型仅适用于特定条件32,33。更具体地说, Rempel 和同事们开发了一个动力学模型来描述量子点 (CdSe) 在有盖配体存在时的形成。然而, 在他们的研究中, 假定配体与纳米粒子表面的结合在任何给定时间32的平衡。当配体大量过剩时, 这种假设可能会成立。我们集团最近开发了一种新的配体模型14 , 它占盖配体的结合与前驱 (金属复合体) 和纳米粒子表面作为可逆反应14。此外, 我们的配体模型可能被用于其他金属纳米粒子系统, 其中合成动力学似乎受到配体存在的影响。
在目前的研究中, 我们使用我们新近开发的配体模型来预测钯纳米粒子在不同溶剂中的形成和生长, 包括甲苯和吡啶。对于模型输入, 利用原位 SAXS 在合成过程中获得纳米粒子的浓度和粒度分布。测量粒子的大小和浓度, 辅以动力学建模, 使我们能够提取出关于成核和生长速率的更精确的信息。我们进一步证明, 我们的配体模型, 明确地描述配体-金属结合, 是高度预测性的, 可用于设计合成程序, 以获得所需尺寸的纳米粒子。

<table><tbody><tr><td>palladium acetate (Pd(OAc)2)</td><td>ALDRICH</td><td>520764</td><td></td></tr><tr><td>anhydrous acetic acid</td><td>SIAL</td><td>338826</td><td></td></tr><tr><td>trioctylphosphine</td><td>ALDRICH</td><td>718165</td><td></td></tr><tr><td>pyridine</td><td>MilliporeSigma</td><td>PX2012-7</td><td></td></tr><tr><td>toluene</td><td>SIAL</td><td>244511</td><td></td></tr><tr><td>1-hexanol</td><td>SIAL</td><td>471402</td><td></td></tr><tr><td>N8 Horizon SAXS</td><td>Bruker</td><td>A32-X1</td><td></td></tr><tr><td>glovebox</td><td>Vaccum Atmospheres Co.</td><td>109035</td><td></td></tr><tr><td>MR HEI-TEC 115V Hotplate</td><td>Heidolph</td><td>5053000000</td><td></td></tr><tr><td>hotplate Monoblock insert</td><td>Heidolph</td><td>5058000800</td><td></td></tr><tr><td>heat-On 25-ml insert</td><td>Heidolph</td><td>5058006200</td><td></td></tr><tr><td>7 mL vials</td><td>SUPELCO</td><td>27518</td><td></td></tr><tr><td>micro stir bar PTFE&amp;nbsp;</td><td>VWR</td><td>58948-353</td><td></td></tr><tr><td>egg-Shaped Bars&amp;nbsp;</td><td>Fisherbrand&amp;trade;&amp;nbsp;</td><td>14-512-121</td><td></td></tr><tr><td>25 mL round bottom flasks</td><td>ALDRICH</td><td>Z167495</td><td></td></tr><tr><td>quartz capillary</td><td>Hampton Research</td><td>HR6-148</td><td></td></tr><tr><td>MATLAB R2016b</td><td>MathWorks</td><td></td><td></td></tr><tr><td>Bruker SAXS 1.0v</td><td>Bruker</td><td></td><td></td></tr><tr><td>Diffrac Measurement Center 4.0v</td><td>Bruker</td><td></td><td></td></tr></tbody></table>

ligand-mediated nucleation and growth of palladium metal nanoparticles

胶粒的大小、分布和稳定性受到上限配体的存在影响很大。尽管在合成反应过程中, 封盖配体的关键贡献, 但它们在调节胶体纳米粒子的成核和生长速率方面的作用还不清楚。在这项工作中, 我们用原位SAXS 和配体为基础的动力学模型, 证明了 trioctylphosphine (顶部) 在不同溶剂 (甲苯和吡啶) 中的作用。我们在不同合成条件下的结果揭示了钯纳米粒子在反应过程中的成核和生长重叠, 这与拉美型成核和生长模型相矛盾。该模型说明了前驱体和粒子表面的 Pd-顶结合的动力学, 这对于捕获粒径演化和原位粒子浓度是必不可少的。此外, 我们通过设计合成条件以获得所需尺寸的纳米粒子, 说明了我们配体模型的预测力。所提出的方法可以应用于其他合成系统, 因此是预测合成胶体纳米粒子的有效策略。

为了系统地研究封盖配体是否改变了成核和生长的动力学, 我们采取了以下两种方法: (i) 在与前人研究类似的动力学模型中未考虑配位与金属的结合 (i.、成核和自催化生长) (ii.) 在模型 (i.、以配体为基础的模型中, 考虑了纳米粒子的前体和表面) 对封盖配体的可逆结合。关于甲苯的 Pd 合成, 如图 1所示, 不考虑配体-金属结合, 该模型未能?...

Watch this Scientific Journal Video about Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles at JoVE.com

Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

配体介导成核与钯金属纳米粒子的生长

本研究的主要目的是通过结合 i.原位小角 x 射线散射 (SAXS) 和配体的动力学建模, 阐明封盖剂在调节钯纳米粒子尺寸中的作用。

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution ...

ligand-mediated-nucleation-and-growth-of-palladium-metal-nanoparticles

Universidad San Sebastian

Research

Education

JoVE Journal

JoVE Core

Chemistry

Transition Metals and Coordination Complexes

SCIENTISTS IN ACTION

10.3K 次观看.  Virginia Polytechnic Institute and State University. 本研究的主要目的是通过结合 i.原位小角 x 射线散射 (SAXS) 和配体的动力学建模, 阐明封盖剂在调节钯纳米粒子尺寸中的作用。

视频: Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and scalable technique efficiently functionalizes metallic nanoparticles with thiol-ligands in a miscible water/organic solvent mixture allowing for rapid grafting of thiol groups onto the gold nanoparticle surface. The hydrophobic ligands on the nanoparticles then quickly phase separate the nanoparticles from the aqueous based suspension and confine them to the air-fluid interface. This drives the ligand-capped nanoparticles to form monolayer domains at the air-fluid interface.&#160; The use of water-miscible organic solvents is important as it enables the transport of the nanoparticles from the interface onto template-free substrates.&#160; The flow is mediated by a surface tension gradient3,4 and creates macroscopic, high-density, monolayer nanoparticle-ligand films.&#160; This self-assembly technique may be generalized to include the use of particles of different compositions, size, and shape and may lead to an efficient assembly method to produce low-cost, macroscopic, high-density, monolayer nanoparticle films for wide-spread applications.

A simple, robust and scalable technique to functionalize and self-assemble macroscopic nanoparticle-ligand monolayer films onto template-free substrates is described in this protocol.

一种技术，功能化和自组装纳米宏观 - 配体单层膜模板上无基材

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and ...

科研

化学

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 &#176;C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 &#176;C make 1 to one of the most attractive and greenest Heck catalysts available.
We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 &#176;C and show that this catalyst is suitable for its use in organic syntheses.

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1) is an easy accessible, cheap, and air stable, but highly active Heck catalyst with an excellent functional group tolerance that efficiently operates under mild reaction conditions to give the coupling products in very high yields.

Mizoroki-哎呀交叉偶联反应由二氯{双[1,1&#39;，1&#39;&#39;  - （phosphinetriyl）tripiperidine]}钯催化在温和的反应条件

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family ...

Generation of Zerovalent Metal Core Nanoparticles Using n-(2-aminoethyl)-3-aminosilanetriol

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of n-(2-aminoethyl)-3-aminosilanetriol is presented. This compound can be used to effectively reduce and complex metal salts into metal core nanoparticles coated with the compound. By controlling the concentrations of salt and silane one is able to control reaction rates, particle size, and nanoparticle coating. The effects of these changes were characterized through transmission electron microscopy (TEM), UV-Vis spectrometry (UV-Vis), Nuclear Magnetic Resonance spectroscopy (NMR) and Fourier Transform Infrared spectroscopy (FTIR). A unique aspect to this reaction is that usually silanes hydrolyze and cross-link in water; however, in this system the silane is water-soluble and stable. It is known that silicon and amino moieties can form complexes with metal salts. The silicon is known to extend its coordination sphere to form penta- or hexa-coordinated species. Furthermore, the silanol group can undergo hydrolysis to form a Si-O-Si silica network, thereby transforming the metal nanoparticles into a functionalized nanocomposites.

Generation of Zerovalent Metal Core Nanoparticles Using n-2-aminoethyl-3-aminosilanetriol

A novel method for metal core nanoparticle synthesis using a water stable silanol is described.

使用N-零价金属芯纳米粒子的生成（2-氨基乙基）-3- aminosilanetriol

In this work, a facile one-pot reaction for the formation of metal nanoparticles in a water solution through the use of ...

Synthesis of Bimetallic Pt/Sn-based Nanoparticles in Ionic Liquids

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular physico-chemical properties of ionic liquids (ILs) are exploited to control both nucleation and growth processes. The nanoparticles form colloidal sols of very high colloidal stability in the IL, which is particularly interesting in view of their use as quasi-homogeneous catalysts. Procedures for both nanoparticle extraction in conventional solvents and for nanoparticle precipitation are presented. The size, structure and composition of the synthesized nanocrystals are confirmed using inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDX). By this, we show that the nanocrystals are random-type alloy and of small (2-3 nm) size. The catalytic activity and selectivity in the hydrogenation of &#945;,&#946;-unsaturated aldehydes is tested in a semi-continuous batch-type reactor. In this context, the bimetallic Pt/Sn-based nanoparticles reveal a high selectivity towards the unsaturated alcohol.

A protocol for the synthesis of bimetallic nanoparticles in ionic liquids and the procedure of their catalytic testing in the selective hydrogenation of unsaturated aldehydes are described.

离子液体中双金属 Pt/锡基纳米粒子的合成

We demonstrate a method for the synthesis of bimetallic nanoparticles consisting of Pt and Sn. A synthesis strategy is used in which the particular ...

A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic nanoparticles is developed. Guidelines for the replication of the reactor and its operation are provided in detail. Three different composite systems (Pt/graphene, Pt/TiO2, and Au/TiO2) with monodisperse and uniformly distributed particles are produced by this reactor, and the photodeposition mechanism, as well as the synthesis optimization strategy, are discussed. The synthesis methods and their technical aspects are described comprehensively. The role of the ultraviolet (UV) dose (in each excitation pulse) on the photodeposition process is investigated and the optimum values for each composite system are provided.

For a continuous and scalable synthesis of noble-metal-based nanocomposites, a novel photocatalytic reactor is developed and its structure, operation principles, and product quality optimization strategies are described.

一种用于金属纳米粒子精确控制沉积的连续流动光催化反应器

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic ...

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often result in fragile aerogels with poor shape control. The use of carboxymethylated cellulose nanofibers (CNFs) to form a covalently bonded hydrogel allows for the reduction of metal ions such as palladium on the CNFs with control over both nanostructure and macroscopic aerogel monolith shape after supercritical drying. Crosslinking the carboxymethylated cellulose nanofibers is achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the presence of ethylenediamine. The CNF hydrogels maintain their shape throughout synthesis steps including covalent crosslinking, equilibration with precursor ions, metal reduction with high concentration reducing agent, rinsing in water, ethanol solvent exchange, and CO2 supercritical drying. Varying the precursor palladium ion concentration allows for control over the metal content in the final aerogel composite through a direct ion chemical reduction rather than relying on the relatively slow coalescence of pre-formed nanoparticles used in other sol-gel techniques. With diffusion as the basis to introduce and remove chemical species into and out of the hydrogel, this method is suitable for smaller bulk geometries and thin films. Characterization of the cellulose nanofiber-palladium composite aerogels with scanning electron microscopy, X-ray diffractometry, thermal gravimetric analysis, nitrogen gas adsorption, electrochemical impedance spectroscopy, and cyclic voltammetry indicates a high surface area, metallized palladium porous structure.

A synthesis method for cellulose nanofiber biotemplated palladium composite aerogels is presented.The resulting composite aerogel materials offer potential for catalysis, sensing, and hydrogen gas storage applications.

纤维素纳米纤维生物模板复合气凝胶的合成方法

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often ...

Photodeposition of Pd onto Colloidal Au Nanorods by Surface Plasmon Excitation

A protocol is described to photocatalytically guide Pd deposition onto Au nanorods (AuNR) using surface plasmon resonance (SPR). Excited plasmonic hot electrons upon SPR irradiation drive reductive deposition of Pd on colloidal AuNR in the presence of [PdCl4]2-. Plasmon-driven reduction of secondary metals potentiates covalent, sub-wavelength deposition at targeted locations coinciding with electric field &#8220;hot-spots&#8221; of the plasmonic substrate using an external field (e.g., laser). The process described herein details a solution-phase deposition of a catalytically-active noble metal (Pd) from a transition metal halide salt (H2PdCl4) onto aqueously-suspended, anisotropic plasmonic structures (AuNR). The solution-phase process is amenable to making other bimetallic architectures. Transmission UV-vis monitoring of the photochemical reaction, coupled with ex situ XPS and statistical TEM analysis, provide immediate experimental feedback to evaluate properties of the bimetallic structures as they evolve during the photocatalytic reaction. Resonant plasmon irradiation of AuNR in the presence of [PdCl4]2- creates a thin, covalently-bound Pd0 shell without any significant dampening effect on its plasmonic behavior in this representative experiment/batch. Overall, plasmonic photodeposition offers an alternative route for high-volume, economical synthesis of optoelectronic materials with sub-5 nm features (e.g., heterometallic photocatalysts or optoelectronic interconnects).

A protocol for anisotropic photodeposition of Pd onto aqueously-suspended Au nanorods via localized surface plasmon excitation is presented.

通过表面等离子体激发将 Pd 光沉积到胶体 Au 纳米棒上

A protocol is described to photocatalytically guide Pd deposition onto Au nanorods (AuNR) using surface plasmon resonance (SPR). Excited plasmonic hot ...

Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular transformations. This opens possibilities for the use of visible or near-IR light as a sustainable input to drive and control reactions when plasmonic nanoparticles supporting LSPR excitation in these ranges are employed as catalysts. Unfortunately, this is not the case for several catalytic metals such as palladium (Pd). One strategy to overcome this limitation is to employ bimetallic NPs containing plasmonic and catalytic metals. In this case, the LSPR excitation in the plasmonic metal can contribute to accelerate and control transformations driven by the catalytic component. The method reported herein focuses on the synthesis of bimetallic silver-palladium (Ag-Pd) NPs supported on ZrO2 (Ag-Pd/ZrO2) that acts as a plasmonic-catalytic system. The NPs were prepared by co-impregnation of corresponding metal precursors on the ZrO2 support followed by simultaneous reduction leading to the formation of bimetallic NPs directly on the ZrO2 support. The Ag-Pd/ZrO2 NPs were then used as plasmonic catalysts for the reduction of nitrobenzene under 425 nm illumination by LED lamps. Using gas chromatography (GC), the conversion and selectivity of the reduction reaction under the dark and light irradiation conditions can be monitored, demonstrating the enhanced catalytic performance and control over selectivity under LSPR excitation after alloying non-plasmonic Pd with plasmonic metal Ag. This technique can be adapted to a wide range of molecular transformations and NPs compositions, making it useful for the characterization of the plasmonic catalytic activity of different types of catalysis in terms of conversion and selectivity.

Presented here is a protocol for the synthesis of silver-palladium (Ag-Pd) alloy nanoparticles (NPs) supported on ZrO2 (Ag-Pd/ZrO2). This system allows for harvesting energy from visible light irradiation to accelerate and control molecular transformations. This is illustrated by nitrobenzene reduction under light irradiation catalyzed by Ag-Pd/ZrO2 NPs.

在可见光照射下为质子催化准备银-铂合金纳米粒子

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular ...

Studying the Effects of Temperature on the Nucleation and Growth of Nanoparticles by Liquid-Cell Transmission Electron Microscopy

Temperature control is a recent development that provides an additional degree of freedom to study nanochemistry by liquid cell transmission electron microscopy. In this paper, we describe how to prepare an in situ heating experiment for studying the effect of temperature on the formation of gold nanoparticles driven by radiolysis in water. The protocol of the experiment is fairly simple involving a special liquid cell with uniform heating capabilities up to 100 &#176;C, a liquid-cell TEM holder with flow capabilities and an integrated interface for controlling the temperature. We show that the nucleation and growth mechanisms of gold nanoparticles are drastically impacted by the temperature in liquid cell. Using STEM imaging and nanodiffraction, the evolution of the density, size, shape and atomic structure of the growing nanoparticles are revealed in real time. Automated image processing algorithms are exploited to extract useful quantitative data from video sequences, such as the nucleation and growth rates of nanoparticles. This approach provides new inputs for understanding the complex physico-chemical processes at play during the liquid-phase synthesis of nanomaterials.

Temperature control during liquid-phase electron microscopy experiments opens up new perspectives of studying the dynamic of nanoparticles in liquid environments mimicking their formation or application media. Using recently developed heating liquid cells, we directly observed the influence of temperature on the nucleation and growth processes of gold nanoparticles in water.

研究温度对液细胞传输电子显微镜对纳米粒子核化和生长的影响

Temperature control is a recent development that provides an additional degree of freedom to study nanochemistry by liquid cell transmission electron ...

Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes

Ligands like amines are used in the colloidal synthesis approach to protect platinum nanoparticles (Pt NP&#39;s) from agglomeration. Normally, ligands like amines are removed by diverse pre-treatment procedures before use in heterogeneous catalysis as amines are considered as a catalyst poison. However, a possible beneficial influence of these surface modifiers on hydrogenation reactions, which is known from spectator species on metal surfaces, is often neglected.
Therefore, amine-stabilized Pt nanoparticles supported by titania (P25) were used without any pre-treatment in order to elucidate a possible influence of the ligand in liquid phase hydrogenation reactions. The catalytic activity of amine-stabilized Pt nanoparticles of two different sizes was investigated in a double-walled stirring tank reactor at 69 &#176;C to 130 &#176;C and 1 atm hydrogen pressure. The conversion of cyclohexene to cyclohexane was determined by gas chromatography (GC) and was compared to ligand-free Pt particles. All catalysts were checked before and after reaction by transmission electron spectroscopy (TEM) and X-ray photoelectron spectroscopy (XPS) for possible changes in size, shape, and ligand shell. The hydrogenation of cyclohexene in liquid phase revealed a higher conversion for amine-stabilized Pt nanoparticles on titania than the ligand-free particles. The hydrogenation of 5-methylfurfural (5-MF) was chosen for a further test reaction, since the hydrogenation of &#945;, &#946;-unsaturated aldehydes is more complex and exhibits various reaction paths. However, XPS and infrared spectroscopy (IR) proved that 5-MF acts as catalyst poison at the given reaction conditions.

This protocol shows a convenient method for comparing the catalytic properties of supported platinum catalysts, synthesized by deposition of nanosized colloids or by impregnation. The hydrogenation of cyclohexene serves as a model reaction to determine the catalytic activity of the catalysts.

烯烃和醛加氢过程中负载在二氧化钛上的胺稳定和无配体铂纳米颗粒的催化反应

Ligands like amines are used in the colloidal synthesis approach to protect platinum nanoparticles (Pt NP&#39;s) from agglomeration. Normally, ligands ...