Caponetti Eugenio, Martino Delia Chillura, Leone Maurizio, Pedone Lucia, Saladino Maria Luisa, Vetri Valeria
Dipartimento di Chimica Fisica F. Accascina, Università di Palermo, Viale delle Scienze, Parco d'Orleans II, I-90128 Palermo, Italy.
J Colloid Interface Sci. 2006 Dec 15;304(2):413-8. doi: 10.1016/j.jcis.2006.09.026. Epub 2006 Sep 16.
Microwave irradiation at a frequency of 2.45 GHz and a power ranging between 22 and 30 W was used, in a water-oil microemulsion at 35+/-2 degrees C, to obtain stable, small, crystalline, anhydrous CdS nanoparticles exhibiting enhanced luminescence properties. The process of nanoparticles growth at different irradiation times was followed by UV-vis spectroscopy. It was observed that irradiated nanoparticles grew faster and their size reached a constant value. The final mean nanoparticle diameter was 2.7 nm, smaller than that observed in a non-irradiated sample, in which particle dimensions slowly increased even after 10 h. This finding was confirmed by high resolution transmission electron microscopy which also suggested that the spherical nanoparticles had a narrow size distribution and were spatially well separated. Furthermore, Fourier transform infrared spectroscopy was used to obtain information about structural changes that the microemulsion underwent when irradiated by microwaves. In particular, the evolution of the stretching and bending bands of water molecules along with the CO and SO3 stretching bands of the surfactant molecules, showed that water was selectively and almost completely extracted from the aqueous core of the reversed micelles. Changes in the surroundings of the nanoparticles surface were monitored by photoluminescence spectroscopy and variations in the emission band profiles indicated enhanced luminescence properties. The latter finding, as well as the inhibition of the nanoparticles growth process, are attributable to the progressive reduction of water content in the core of the reversed micelles.
在35±2℃的水 - 油微乳液中，使用频率为2.45 GHz、功率在22至30 W之间的微波辐射，以获得具有增强发光特性的稳定、小尺寸、结晶态、无水硫化镉纳米颗粒。通过紫外 - 可见光谱跟踪不同辐照时间下纳米颗粒的生长过程。观察到辐照后的纳米颗粒生长更快，其尺寸达到恒定值。最终纳米颗粒的平均直径为2.7 nm，小于未辐照样品中的观察值，在未辐照样品中，即使在10小时后颗粒尺寸仍缓慢增加。高分辨率透射电子显微镜证实了这一发现，该显微镜还表明球形纳米颗粒具有窄的尺寸分布且在空间上分离良好。此外，使用傅里叶变换红外光谱来获取有关微乳液在微波辐照时所经历的结构变化的信息。特别是，水分子的伸缩和弯曲带以及表面活性剂分子的CO和SO3伸缩带的演变表明，水被选择性地且几乎完全从反胶束的水核中提取出来。通过光致发光光谱监测纳米颗粒表面周围环境的变化，发射带轮廓的变化表明发光特性增强。后一发现以及纳米颗粒生长过程的抑制归因于反胶束核心中含水量的逐渐减少。
