Jatav Hemant, Mičetic Maja, Chakravorty Anusmita, Mishra Ambuj, Schwartzkopf Matthias, Chumakov Andrei, Roth Stephan V, Kabiraj Debdulal
Materials Science Department, Inter-University Accelerator Centre, New Delhi, India.
Ruđer Bošković Institute, Bijenička Cesta 54, Zagreb 10000, Croatia.
Nanoscale. 2023 Jul 20;15(28):12025-12037. doi: 10.1039/d3nr01595e.
Thermal growth kinetics of embedded bimetallic (AuAg/SiO) nanoparticles are explored and compared with their monometallic (Au/SiO and Ag/SiO) counterparts, as their practical applicability demands stability and uniformity. The plasmonic properties of these nanoparticles (NPs) significantly improve when their size falls in the ultra-small region (diameter < 10 nm), owing to their large active surface area. Interestingly, the bimetallic NPs exhibit better optical properties and structural stability as compared to their monometallic counterparts. This calls for a thorough understanding of the nucleation and temperature-dependent growth to ensure size stability against thermal coarsening that most bimetallic NPs completely lack. Herein, the atom beam sputtered AuAg NPs are systematically analysed over a wide range of annealing temperatures (ATs), and the results are compared with those of Au and Ag NPs. The X-ray photoelectron spectroscopy spectra and other experimental results confirm the formation of AuAg alloy NPs inside the silica matrix. Furthermore, techniques like transmission electron microscopy and grazing-incidence small-/wide-angle X-ray scattering were used to explore the temperature-dependent structural and morphological stability of the NPs. Our results show that the deposited AuAg NPs retain their spherical shape and remain as an alloy for the entire range of ATs. When the AT increases from 25 °C to 800 °C, the size of the NPs also increases from 3.5 to 4.8 nm; beyond that, their size grows substantially to 13.6 nm at 900 °C. We observed that the NPs remain in the ultra-small size range (∼5 nm) until an AT of 800 °C. Beyond that Ostwald ripening is ascribed to be the major cause of particle growth, resulting in an active surface area loss. Based on the outcomes, a three-step nucleation and growth mechanism is proposed.
研究了嵌入的双金属（AuAg/SiO）纳米颗粒的热生长动力学，并将其与单金属（Au/SiO和Ag/SiO）纳米颗粒进行了比较，因为它们的实际应用需要稳定性和均匀性。当这些纳米颗粒（NPs）的尺寸处于超小区域（直径<10 nm）时，由于其较大的活性表面积，其等离子体特性会显著改善。有趣的是，与单金属纳米颗粒相比，双金属纳米颗粒表现出更好的光学性能和结构稳定性。这就需要深入了解成核和温度依赖的生长过程，以确保尺寸稳定性，防止大多数双金属纳米颗粒完全缺乏的热粗化现象。在此，对原子束溅射的AuAg纳米颗粒在广泛的退火温度（ATs）范围内进行了系统分析，并将结果与Au和Ag纳米颗粒的结果进行了比较。X射线光电子能谱和其他实验结果证实了二氧化硅基质内AuAg合金纳米颗粒的形成。此外，还使用了透射电子显微镜和掠入射小/广角X射线散射等技术来探索纳米颗粒的温度依赖结构和形态稳定性。我们的结果表明，沉积的AuAg纳米颗粒在整个AT范围内都保持其球形并作为合金存在。当AT从25°C增加到800°C时，纳米颗粒的尺寸也从3.5 nm增加到4.8 nm；超过该温度后，在900°C时其尺寸大幅增长至13.6 nm。我们观察到，在800°C的退火温度之前，纳米颗粒保持在超小尺寸范围内（约5 nm）。超过该温度后，奥斯特瓦尔德熟化被认为是颗粒生长的主要原因，导致活性表面积损失。基于这些结果，提出了一种三步成核和生长机制。
