Insights into the synthesis of layered double hydroxide (LDH) nanoparticles: Part 2. Formation mechanisms of LDH.
Insights into the synthesis of layered double hydroxide (LDH) nanoparticles: Part 2. Formation mechanisms of LDH.
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DOI：
10.1016/j.jcis.2015.06.025
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发表时间：
2015-11-15
影响因子：
9.9
通讯作者：
Dey SK
中科院分区：
文献类型：
--
作者：
Sun X;Dey SK
本研究揭示了共插层阴离子组成对纳米结构演变的影响，以了解共沉淀和水热处理后层状双氢氧化物(LDH)纳米颗粒的形成机理。最初，由于表面电荷密度低，室温共沉淀导致了无定形的初级纳米颗粒在边缘聚集。这种团聚的可逆性是由表面电荷密度和表面电荷密度决定的，而表面电荷密度又受插层阴离子组成的强烈影响。在晶化过程中，团聚的Zn2Al(OH)6(NO3)0.3(CO3)0.35·xH2O一次纳米颗粒重新分散，但稳定性较低和无序度较高(尤其是边缘)的Zn2Al(OH)6(NO3)·xH2O纳米颗粒表现出不可逆的团聚现象，并通过团聚生长转变为二次纳米颗粒。此外，对纳米锌铝铝(氢氧化锌)6(硝酸根)y(CO3)0.5(1-y)·xH2O(y=0-1)的稳定性研究表明，当≥y≥为0.6时，共插层阴离子之间的尺寸差异导致了相分离，导致了双峰尺寸分布。此外，通过共插层阴离子组成来控制粗化速度。通过逐渐改变共插层NO3-−与CO32-−的比例，在85℃下高温处理12h，得到了单分散的、粒径在200-400 nm之间的单分散的(1-y)·xH2O(0.5≥y≥0)纳米粒子。
This study demonstrates the effect of (co)intercalated anion compositions on nanostructure evolution to understand the formation mechanisms of layered double hydroxide (LDH) nanoparticles following coprecipitation and hydrothermal treatments (HT). Initially, the room temperature coprecipitation resulted in amorphous primary nanoparticles that agglomerated at the edges due to low surface charge densities. The reversibility of such agglomeration was determined by the crystalline quality upon HT and consequent surface charge density, which in turn were strongly influenced by the composition of the intercalated anions. Upon crystallization, the agglomerated Zn2Al(OH)6(NO3)0.3(CO3)0.35·xH2O primary nanoparticles re-dispersed, but the Zn2Al(OH)6(NO3)·xH2O nanoparticles with much lower stability and higher disorder (especially at the edges) exhibited irreversible agglomeration, and transformed into secondary nanoparticles via aggregational growth. Additionally, the stability studies on Zn2Al(OH)6(NO3)y(CO3)0.5(1-y)·xH2O nanoparticles (y = 0–1) showed that the size difference between the cointercalated anions caused phase separation when 0.9 ≥ y ≥ 0.6, leading to bimodal size distributions. Moreover, the coarsening rates were controlled through the cointercalated anion compositions. By gradually varying the ratio of cointercalated NO3− to CO32−, monodispersed Zn2Al(OH)6(NO3)y(CO3)0.5(1-y)·xH2O (0.5 ≥ y ≥ 0) nanoparticles with systematic variation in the particle size of ~200–400 nm were obtained after HT at 85 °C for 12 h.