Nanosized semiconductor CdS immobilized onto modified multi-walled carbon nanotubes (MWCNTs) carrying poly(amidoamine) dendron units were visualized by HR-TEM. Evidently, spherical CdS nanoparticles 3–5 nm in diameter were identified. Moreover, EDX spectroscopy gave additional spectroscopic proof of the presence of CdS in the CdS-MWCNTs hybrid material. The photocatalytic activity of CdS-MWCNTs toward the decomposition of rhodamine B (RhB) was examined by monitoring spectral changes in the characteristic absorption band of RhB centred at 554 nm. The latter absorption band of RhB was found to continuously depress during visible light irradiation in the presence of CdS-MWCNTs, with faster kinetic rates as compared with the case when only reference CdS was present. The current result was rationalized in terms of efficient photoinduced electron-transfer from CdS to MWCNTs within the intrahybrid CdS-MWCNTs. In this frame, the suggested mechanism for the high and fast photocatalytic decomposition of RhB supports the accumulation of electrons in MWCNTs, which then react with molecular oxygen, thus reducing it to superoxide radical anion O2˙− responsible for the generation of the highly reactive species of HO˙ and HOO˙. The latter together with the holes generated in photoexcited CdS were responsible for the decomposition of RhB. Finally, the photocatalyst CdS-MWCNTs was recovered and efficiently reused for four consecutive catalytic cycles, thus highlighting its wider applicability in removing organic pollutants from water.
利用 HR-
TEM 对固定在带有聚(
氨基胺)树枝状单元的改性多壁碳纳米管(MWCNTs)上的纳米级半导体
镉进行了观察。结果表明,CdS 纳米颗粒呈球形,直径为 3-5 纳米。此外,EDX 光谱法还进一步证明了 CdS-MWCNTs 杂化材料中 CdS 的存在。通过监测以 554 纳米为中心的
罗丹明 B(RhB)特征吸收带的光谱变化,考察了 CdS-MWCNTs 对
罗丹明 B(RhB)分解的光催化活性。研究发现,在有 CdS-MWCNT 存在的情况下,RhB 的后一吸收带在可见光辐照过程中会持续减弱,与只有参考 CdS 存在的情况相比,其动力学速率更快。目前的结果可以从杂化 CdS-MWCNT 内 CdS 向 MWCNT 的高效光诱导电子转移的角度得到合理解释。在此框架下,所提出的 RhB 高、快光催化分解机制支持电子在 MWCNT 中积累,然后与分子氧反应,从而将其还原为超氧自由基阴离子 O2˙--负责生成高活性物种 HO˙和 HOO˙。后者与光激发 CdS 产生的空穴一起导致了 RhB 的分解。最后,光催化剂 CdS-MWCNTs 被回收并有效地重复使用了四个连续催化循环,从而突出了其在去除
水中有机污染物方面的广泛适用性。