Toward monodispersed silver nanoparticles with unusual thermal stability
Toward monodispersed silver nanoparticles with unusual thermal stability
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DOI：
10.1021/ja064884j
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发表时间：
2006-12-13
影响因子：
15
通讯作者：
Su, Dangsheng
中科院分区：
文献类型：
--
作者：
Sun, Junming;Ma, Ding;Su, Dangsheng
一种新的原位自还原途径已经被开发出来，通过该途径，尺寸可调的单分散银纳米粒子可以很容易地在二氧化硅基材料上制备，特别是在介孔二氧化硅（MPS）的通道内。采用碳 - 13交叉极化/魔角旋转核磁共振波谱来监测整个组装过程。结果表明，氨丙基三乙氧基硅烷（APTS）修饰的MPS的氨基可用于锚定甲醛以形成新的还原物种（NHCH₂OH），硝酸银氨（Ag(NH₃)₂NO₃）可在其上原位还原。从而得到单分散的银纳米粒子。采用原位X射线衍射和原位透射电子显微镜实验来研究和比较硅胶外表面（无约束）的银纳米粒子和位于SBA - 15通道内（有约束）的银纳米粒子的热稳定性。观察到无约束的银纳米粒子在低温（即低于773 K）下倾向于团聚。在773 K时银纳米粒子的团聚变得更加严重。然而，对于那些有约束的银纳米粒子，在773 K时没有观察到粗化过程，这个温度远高于其塔曼温度（即617 K）。只有当处理温度高于873 K时，那些有约束的银纳米粒子才会通过奥斯特瓦尔德熟化过程随时间发生团聚。介孔的约束在提高银纳米粒子的热稳定性方面起着关键作用（在高达773 K时稳定，没有任何可观察到的粗化），这对于进一步研究它们的化学（例如催化）性质至关重要。
A novel in situ autoreduction route has been developed, by which monodispersed silver nanoparticles with tunable sizes could be easily fabricated on silica-based materials, especially inside the channels of mesoporous silica (MPS). C-13 CP/MAS NMR spectroscopy was employed to monitor the whole assembly process. It was demonstrated that the amino groups of APTS (aminopropyltriethoxyl silane)modified MPS can be used to anchor formaldehyde to form novel reducing species (NHCH2OH), on which Ag(NH3)(2)NO3 could be in situ reduced. Monodispersed silver nanoparticles were thus obtained. In situ XRD and in situ TEM experiments were used to investigate and compare the thermal stabilities of silver nanoparticles on the external surface of silica gels (unconfined) and those located inside the channels of SBA-15 (confined). It was observed that unconfined silver nanoparticles tended to agglomerate at low temperatures (i.e., lower than 773 K). The aggregation of silver nanoparticles became more serious at 773 K. However, for those confined silver nanoparticles, no coarsening process was observed at 773 K, much higher than its Tammann temperature (i.e., 617 K). Only when the treating temperature was higher than 873 K could the agglomeration of those confined silver nanoparticles happen with time-varying via the Ostwald ripening process. The confinement of mesopores played a key role in improving the thermal stabilities of silver nanoparticles (stable up to 773 K without any observable coarsening), which is essential to the further investigations on their chemical (e.g., catalytic) properties.