Han Yandong, Yang Wensheng
Institute of Nanoscience and Engineering, National & Local Joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials, Henan University, Zhengzhou 450000, China.
College of Chemistry, Jilin University, Changchun 130012, China.
Langmuir. 2024 Jan 30;40(4):2352-2361. doi: 10.1021/acs.langmuir.3c03548. Epub 2024 Jan 19.
In this study, we present a novel modified Stöber method utilizing cetyltrimethylammonium bromide (CTAB) as a mediator for the preparation of monodispersed, micron-sized supermicroporous silica particles. Observed results show prepared silica particles ranging in size from 0.64 to 1.36 μm with an increase in CTAB concentration from 1.0 to 5.0 mM. The particles exhibited low polydispersity (<5%), a high Brunauer-Emmett-Teller surface area (570 to 1064 m/g), and pore volumes ranging from 0.22 to 0.39 cm/g. The pore size, determined using the Barrett-Joyner-Halenda method from the adsorption branches of the isotherms, was approximately 1.9 nm, specifically 1.83, 1.85, and 1.90 nm, as the CTAB concentration increased from 1.0 to 2.5 and 5.0 mM, respectively. The resulting particles displayed a narrow distribution of pore diameters. In addition, to obtain an in-depth understanding of the role of CTAB on the preparation of silica particles, a possible mechanism is also investigated using conductivity, dynamic light scattering (DLS), zeta potential, FT-IR spectra, and transmission electron microscopy. Our findings demonstrate that CTAB plays multiple roles in the hydrolysis/condensation of TEOS (tetraethyl orthosilicate) and subsequent nucleation and growth of silica particles. CTAB acts as a template for superporosity, a stabilizer for colloids, and an accelerator for nucleation and growth, leading to formation of monodispersed micrometer silica particles. Further characterization through FT-IR and Si solid NMR spectra revealed that the micron silica particles were obtained with inhomogeneity in the condensation degree, allowing for selective etching through hot incubation to form micron-sized hollow silica spheres.
在本研究中，我们提出了一种新颖的改进的Stöber方法，该方法利用十六烷基三甲基溴化铵（CTAB）作为介质来制备单分散的微米级超微孔二氧化硅颗粒。观察结果表明，随着CTAB浓度从1.0 mM增加到5.0 mM，制备的二氧化硅颗粒尺寸范围为0.64至1.36μm。这些颗粒表现出低多分散性（<5%）、高比表面积（570至1064 m/g）以及0.22至0.39 cm/g的孔体积。使用等温线吸附分支的Barrett-Joyner-Halenda方法测定的孔径约为1.9 nm，具体而言，随着CTAB浓度分别从1.0 mM增加到2.5 mM和5.0 mM，孔径分别为1.83、1.85和1.90 nm。所得颗粒的孔径分布狭窄。此外，为了深入了解CTAB在二氧化硅颗粒制备中的作用，还使用电导率、动态光散射（DLS）、zeta电位、傅里叶变换红外光谱（FT-IR）和透射电子显微镜对可能的机制进行了研究。我们的研究结果表明，CTAB在正硅酸乙酯（TEOS）的水解/缩合以及随后二氧化硅颗粒的成核和生长过程中发挥多种作用。CTAB充当超孔隙率的模板、胶体的稳定剂以及成核和生长的促进剂，从而导致形成单分散的微米级二氧化硅颗粒。通过FT-IR和硅固体核磁共振光谱进一步表征表明，获得的微米级二氧化硅颗粒在缩合程度上存在不均匀性，通过热孵育进行选择性蚀刻可形成微米级中空二氧化硅球。
