内嵌硫化镉与上转换纳米颗粒的二氧化钛复合纳米管用于近红外光驱动光催化

摘要

We report a colloidal process to coat a layer of TiO2 onto SiO2 composite nanofibers containing em-bedded CdS and upconversion nanoparticles (UCNPs). The SiO2 composite nanofibers were fabri-cated by electrospinning. To improve the energy transfer efficiency, UCNPs and CdS nanoparticles were bound in close proximity to each other within the SiO2 matrix. β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%) core-shell nanoparticles were used as na-notransducers for near infrared light. These nanoparticles exhibited enhanced upconversion fluo-rescence compared with β-NaYF4:Yb(30%),Tm(0.5%) or β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4 nanoparticles. The morphologies, size and chemical compositions have been extensively investi-gated using field emission scanning electron microscopy (FESEM), transmission electron microsco-py (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS), respectively. The TEM images showed that the TiO2 composite nanotubes were embedded with a large amount of UCNPs and CdS nanoparticles. The composite TiO2 nanotubes degraded more than 90% of rhodamine B (RhB) dye during 20 min of irradiation by simulated solar light. In particular, more than 50% of RhB was decomposed in 70 min, under irradiation of near infrared light (NIR). This high degradation was attributed to the full spectrum absorption of solar light, and the enhanced transfer efficiency for near infrared light. The as-prepared nanostructures can harness solar energy, and provide an alter-native to overcome energy shortages and environmental protection.%由于近红外光在太阳光谱中占44%,因此,近红外光驱动的光催化剂的研制具有十分重要的意义.上转换发光材料可将低能量的近红外光子转换为高能光子,这种高能光子可以通过构建荧光共振转移系统将能量转移并活化量子效率较高的半导体材料,对于太阳能的转化利用具有潜在的应用前景.在本文中,通过胶体化学的过程在电纺丝制备的内嵌CdS纳米颗粒以及上转换荧光纳米颗粒(UCNPs)的二氧化硅复合纳米纤维表面外延生长一层二氧化钛层,通过高温煅烧得到二氧化钛复合纳米管.我们通过二氧化硅结构将CdS纳米颗粒与上转换荧光纳米颗粒紧紧束缚在一起,实现较高的荧光共振能量转移.而且,选择β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)作为纳米能量转换器,替代以前研究工作中使用的β-NaYF4:Yb(30%),Tm(0.5%)或者β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4纳米颗粒,来进一步提高近红外光的转换效率.通过透射电子显微镜照片很清楚的观察到制备的TiO2复合纳米管内部内嵌有大量的CdS与上转换纳米颗粒.通过X-射线衍射以及X-射线光电子能谱能仪器对产物的物相以及表面的化学组成进行了细致的表征.结果显示,通过本实验方法已经成功获得了TiO2复合纳米管.用稳态与瞬态荧光仪研究了最终样品的荧光性质.研究结果揭示,与上转换纳米颗粒以及二氧化硅复合纳米纤维相比,复合二氧化钛纳米管可以将上转换荧光纳米颗粒的(UV-Vis)部分荧光完全淬灭了.特别是,铒离子的荧光(650 nm)也被有效淬灭转移,说明本研究采用β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)纳米能量转换器,可以提高近红外光的转换效率,紫外-可见吸收光谱证实,这种二氧化钛纳米管在紫外-可见光区中的吸收光谱与β-NaYF4:Yb(30%),Tm(0.5%)@NaYF4:Yb(20%),Er(2%)纳米颗粒的荧光光谱具有较大的重叠,使得上转换荧光纳米颗粒与CdS以及二氧化钛组分之间的荧光共振转移的效率大大提高,进而会显著提高光催化的效果.以罗丹明染料作为污染物为模型,我们研究了罗丹明染料在氙灯下或者近红外光光照下的光催化分解实验.研究结果表明,90%的罗丹明染料分子在20 min内就被降解掉,效率高于其它的近红外光催化剂.上转换荧光纳米颗粒的能量转换效率可以得到大幅度提高,本研究工作中制备的光催化剂利用太阳能的效率将会得到极大提高,在未来为能源危机以及环境保护提供一种可供选择的方法与技术.