Hu Zeshan, Escamilla Ramírez David J, Heredia Cervera Beatriz E, Oskam Gerko, Searson Peter C
Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Phys Chem B. 2005 Jun 9;109(22):11209-14. doi: 10.1021/jp0506033.
We report on the synthesis of ZnO particles from Zn(CH(3)CO(2))(2) in 2-propanol as a function of the concentration of water, in the absence of a base such as NaOH. Particles with diameters of 3-5 nm are formed depending on time, temperature, and water concentration. The nucleation and growth are slower than in the presence of NaOH, and at longer times the increase in particle size is dominated by diffusion-limited coarsening. The rate constant for coarsening increases with increasing water concentration up to 150 mM, above which the rate constant is 1.1 x 10(-4) cm(3) s(-1), independent of the water concentration. The width of the particle size distribution decreases with increasing water concentration, and at 250 mM water, the full width at half-maximum of the distribution function is essentially the same as for the synthesis of ZnO using NaOH as a reactant. The temperature dependence of coarsening is determined by the bulk solubility of the ZnO nanoparticles and yields an apparent activation energy of 1.12 eV. This is significantly larger than the activation energy of 0.35 eV for coarsening of ZnO from 1 mM Zn(CH(3)CO(2))(2) in 2-propanol with 1.6 mM NaOH.
我们报道了在不存在诸如NaOH等碱的情况下，由Zn(CH₃CO₂)₂在2-丙醇中合成ZnO颗粒时，颗粒尺寸与水浓度的关系。根据时间、温度和水浓度的不同，会形成直径为3-5纳米的颗粒。其成核和生长速度比在有NaOH存在时要慢，并且在较长时间下，颗粒尺寸的增加主要由扩散限制粗化主导。粗化的速率常数随着水浓度增加到150 mM而增大，高于此浓度时，速率常数为1.1×10⁻⁴ cm³ s⁻¹，与水浓度无关。颗粒尺寸分布的宽度随着水浓度的增加而减小，在水浓度为250 mM时，分布函数的半高宽与以NaOH作为反应物合成ZnO时基本相同。粗化的温度依赖性由ZnO纳米颗粒的本体溶解度决定，其表观活化能为1.12 eV。这明显大于在2-丙醇中1 mM Zn(CH₃CO₂)₂与1.6 mM NaOH反应时ZnO粗化的活化能0.35 eV。
