Tzounis Lazaros, Doña Manuel, Lopez-Romero Juan Manuel, Fery Andreas, Contreras-Caceres Rafael
Department of Materials Science & Engineering , University of Ioannina , GR-45110 Ioannina , Greece.
Printed Electronic Devices of Things P.C. (PDoT) , Makrinitsis 122 , GR-38333 Volos , Greece.
ACS Appl Mater Interfaces. 2019 Aug 14;11(32):29360-29372. doi: 10.1021/acsami.9b10773. Epub 2019 Aug 1.
A novel wet-chemical protocol is reported for the synthesis of "temperature-programmable" catalytic colloids consisting of bimetallic core@shell AuAg nanoparticles encapsulated into poly(-isopropylacrylamide) (pNIPAM) microgels with silver satellites (AgSTs) incorporated within the microgel structure. Spherical AuNPs of 50 nm in diameter are initially synthesized and used for growing a pNIPAM microgel shell with temperature stimulus response. A silver shell is subsequently grown on the Au core by diffusing Ag salt through the hydrophilic pNIPAM microgel (AuAg@pNIPAM microgel). The use of allylamine as a co-monomer during pNIPAM polymerization facilitates the coordination of Ag with the NH nitrogen lone pair of electrons, which are reduced to Ag seeds (∼14 nm) using a strong reducing agent, obtaining thus AuAg@pNIPAM@Ag hybrid microgels. The two systems are tested as catalysts toward the reduction of 4-nitrophenol (4-Nip) to 4-aminophenol (4-Amp) by NaBH. Both exhibit extremely sensitive temperature-dependent reaction rate constants, with the highest value of the order of 0.6 L/m s, which is one of the highest values ever reported. The presence of plasmonic entities is confirmed by UV-vis spectroscopy. Dynamic light scattering proves the temperature responsiveness in all cases. Transmission electron microscopy and energy-dispersive X-ray (EDX) elemental mapping highlight the monodispersity of the synthesized hybrid nanostructured microgels, as well as their size and metallic composition. The amount of gold and silver in both systems is obtained by thermogravimetric analysis and the EDX spectrum. The reduction reaction kinetics is monitored by UV-vis spectroscopy at different temperatures for both catalytic systems, with the AuAg@pNIPAM@Ag microgels showing superior catalytic performance at all temperatures because of the synergistic effect of the AuAg core and the AgSTs. The principal novelty of this study lies in the "hierarchical" design of the metal-polymer-metal core@shell@satellite nanostructured colloids exhibiting synergistic capabilities of the plasmonic NPs for, among others, temperature-controlled catalytic applications.
报道了一种新型的湿化学方法，用于合成“温度可编程”催化胶体，该胶体由双金属核壳结构的金银纳米颗粒组成，这些纳米颗粒被包裹在聚（N-异丙基丙烯酰胺）（pNIPAM）微凝胶中，且微凝胶结构中含有银卫星颗粒（AgSTs）。首先合成直径为50nm的球形金纳米颗粒，并用于在温度刺激响应下生长pNIPAM微凝胶壳。随后通过使银盐扩散穿过亲水性pNIPAM微凝胶（AuAg@pNIPAM微凝胶）在金核上生长银壳。在pNIPAM聚合过程中使用烯丙胺作为共聚单体，有助于银与NH氮孤对电子配位，使用强还原剂将其还原为银种子（约14nm），从而得到AuAg@pNIPAM@Ag杂化微凝胶。测试了这两种体系作为催化剂，用于通过硼氢化钠将4-硝基苯酚（4-Nip）还原为4-氨基苯酚（4-Amp）的性能。两者均表现出对温度极为敏感的反应速率常数，最高值约为0.6L/（m·s），这是有史以来报道的最高值之一。通过紫外可见光谱证实了等离子体实体的存在。动态光散射证明了在所有情况下均具有温度响应性。透射电子显微镜和能量色散X射线（EDX）元素映射突出了合成的杂化纳米结构微凝胶的单分散性，以及它们的尺寸和金属组成。通过热重分析和EDX光谱获得了两种体系中的金和银含量。通过紫外可见光谱在不同温度下监测两种催化体系的还原反应动力学，由于AuAg核和AgSTs的协同作用，AuAg@pNIPAM@Ag微凝胶在所有温度下均表现出优异的催化性能。本研究的主要新颖之处在于金属-聚合物-金属核壳卫星纳米结构胶体的“分级”设计，该胶体展现了等离子体纳米颗粒在温度控制催化应用等方面的协同能力。
