Lei Liu,Xiang Cheng,Xiwang Miao,Ying Zhang,Min Guo,Fangqin Cheng,Mei Zhang
In this work, a series of SiO 2 @n-octadecane capsules were prepared by one step emulsion polymerization, the influence of emulsifying speed, ammonia and TEOS contents, reaction temperature, concentration of emulsifier and the amount of PVP on the size, structure and performance was detailed investigated. It can be seen from SEM characterization that among these factors emulsification speed had the greatest influence on capsule size, while followed by the ammonia and TEOS content. According to TEM results, the ammonia and TEOS contents were the most important factors on the structure (shell thickness and surface smoothness) of the capsules, attributing to ammonia and TEOS were the catalyst and reactant of hydrolysis polymerization, respectively. Generally, the crystallinity of the samples became worse as the size decreased. DSC results showed that excessive ammonia or TEOS caused a significant drop in the enthalpy of the samples, furthermore, the enthalpy basically decreased with the attenuation of the inner radius of the sample. The target SiO 2 @n-octadecane capsule was sample C2 with high enthalpy (127.7 J/g), size of 1.62 μm, shell thickness of 68 nm, and smooth surface. More importantly, within the parameters studied, a series of SiO 2 @n-octadecane capsules were successfully synthesized with different enthalpy values (min 85.9 J/g, max 144.3 J/g), sizes ranging from 0.63–2.75 μm, shell thickness 32–79 nm and different smooth surfaces. Therefore, the controllable synthesis of SiO 2 @n-octadecane capsules within the above range can be achieved by simulating different parameters and their development.
WO 3 :Eu 3+ powder was prepared by microemulsion method with cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The prepared WO 3 :Eu 3+ samples were wrapped with SiO 2 by a coating method. The WO 3 :Eu 3+ @ SiO 2 nanocomposites with the core-shell structure were prepared by controlling tetraethyl orthosilicate (TEOS) content (1, 3, 5 and 7%) and water–alcohol ratio (1:3, 1:1.5, 1:1 and 2:1). The structure, morphology and luminescence properties of the prepared WO 3 :Eu 3+ @ SiO 2 samples were characterized by XRD, SEM, TEM and fluorescence spectra. The results show that the prepared WO 3 :Eu 3+ @SiO 2 nanocomposites are spherical and granular, and the average particle size is below 100 nm. Under the condition of different TEOS contents, the strongest characteristic peak is located at 554 nm in the green light band at the excitation wavelength of 328 nm. Among the different water–alcohol ratio conditions, the prepared WO 3 :Eu 3+ @SiO 2 nanocomposite has the strongest luminescence intensity at the water–alcohol ratio of 1:3, and the excitation wavelength is 328 nm. The excitation spectra measured at 612 nm have prominent characteristic peaks at 362, 394, 422, 465 and 499 nm, which correspond to the transition of 7 F 0 → 5 D 4 , 7 F 0 → 5 L 6 , 7 F 0 → 5 D 3 , 7 F 0 → 5 D 2 and 7 F 0 → 5 D 1 , respectively.
危险品化学品经营许可证（带存储）