Kinetics of Monodisperse Iron Oxide Nanocrystal Formation by “Heating-Up” Process

Abstract

We studied the kinetics of the formation of iron oxide nanocrystals obtained from the solution-phase thermal decomposition of iron-oleate complex via the "heating-up" process. To obtain detailed information on the thermal decomposition process and the formation of iron oxide nanocrystals in the solution, we performed a thermogravimetric-mass spectrometric analysis (TG-MS) and in-situ magnetic measurements using SQUID. The TG-MS results showed that iron-oleate complex was decomposed at around 320 degrees C. The in-situ SQUID data revealed that the thermal decomposition of iron-oleate complex generates intermediate species, which seem to act as monomers for the iron oxide nanocrystals. Extensive studies on the nucleation and growth process using size exclusion chromatography, the crystallization yield data, and TEM showed that the sudden increase in the number concentration of the nanocrystals (burst of nucleation) is followed by the rapid narrowing of the size distribution (size focusing). We constructed a theoretical model to describe the "heating-up" process and performed a numerical simulation. The simulation results matched well with the experimental data, and furthermore they are well fitted to the well-known LaMer model that is characterized by the burst of nucleation and the separation of nucleation and growth under continuous monomer supply condition. Through this theoretical work, we showed that the "heating-up" and "hot injection" processes could be understood within the same theoretical framework in which they share the characteristics of nucleation and growth stages.

Advancing colloidal quantum dot photovoltaic technology

“…An alternative synthesis method, known as the "heating-up" method, involves mixing all precursors, reagents and solvent together at a low temperature and heating the mixture to a specific temperature [69]. This method yields similar size dispersity as the hot injection method, but may offer greater scalability potential due to its simplicity.…”

Thermodynamics and Kinetics in the Synthesis of Monodisperse Nanoparticles

“…[17,18] Therefore, to inhibit Ostwald ripening, the supersaturation for growth should be maintained much higher than that by the Gibbs-Thompson effect. This aspect was studied in detail by Kwon et al [8].…”

“…Although nanoparticles have some size distribution in the nucleation stage, they became gradually monodisperse during growth. In this case, the principle for the direct synthesis of monodisperse nanoparticles could be approached by sustained growth of nuclei formed by burst nucleation with some initial size distribution [8].…”

Os nanomateriais e a descoberta de novos mundos na bancada do químico

“…Após o sistema atingir este grau de sobressaturação crítico, a nucleação ocorre de forma semelhante à descrita para o mecanismo de injeção a quente. 35 Se o processo de nucleação instantânea permitiu a formação de um elevado número de núcleos primários de dimensões reduzidas (ainda assim superiores ao raio crítico, r*), por diminuição da sobressaturação e, por consequência da energia livre, as condições de sobressaturação existentes e a elevada energia superficial destes núcleos primários são suficientes para que o processo de crescimento das partículas ocorra de forma a atingirem maiores dimensões. As NP formadas possuem uma elevada energia de superfície e têm tendência para continuar a crescer.…”