Colloids and Nanomaterials Laboratory, Department of Chemical Engineering, Visvesvaraya National Institute of Technology, South Ambazari Road, Nagpur 440010, Maharashtra, India.
Langmuir. 2023 Jul 11;39(27):9325-9342. doi: 10.1021/acs.langmuir.3c00676. Epub 2023 Jun 27.
A nanoparticle (NP) formation mechanism based on thermal energy equilibration is proposed to explain the formation of NPs in the liquid-phase thermal decomposition route. The prevailing mechanism of monodisperse NP formation in this route limits the nucleation process to be single and instantaneous, followed by growth via monomeric addition. Herein, the extensive investigations carried out in the heat-up method of iron oxide NP synthesis reveal that multiple nucleation events occur in the system when the thermal energy remains constant or varies minimally with time, accompanied by particle growth. In addition, the growth occurs via coagulation and/or monomeric addition depending on the aggregation barrier established by the supplied energy, ligand used, heating rate applied, and the allowed aging period. By fundamentally understanding the influence of these parameters on the precursor decomposition process, a generalized NP formation mechanism in the heat-up approach is proposed and used as a guideline to prepare anisotropic particles without using any shape-directive agents. The mechanistic understandings were further extended to hot-injection and seed-mediated growth protocols which exhibited an analogous NP formation pathway.
提出了一种基于热能平衡的纳米颗粒（NP）形成机制，用于解释液相热分解途径中 NP 的形成。该途径中单分散 NP 形成的主要机制将成核过程限制为单一和瞬时的，随后通过单体添加进行生长。在此，通过对氧化铁 NP 合成的升温方法进行广泛研究，发现当热能保持恒定或随时间变化很小，同时伴有颗粒生长时，系统中会发生多次成核事件。此外，根据所提供的能量、所用配体、施加的加热速率以及允许的老化期建立的聚集势垒，生长通过凝聚和/或单体添加进行。通过从根本上了解这些参数对前体分解过程的影响，提出了一种在升温方法中通用的 NP 形成机制，并将其用作制备无需使用任何形状导向剂的各向异性颗粒的指南。该机理理解进一步扩展到热注入和种子介导的生长方案，它们表现出类似的 NP 形成途径。
