Chronopoulos D D, Karousis N, Zhao S, Wang Q, Shinohara H, Tagmatarchis N
Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, Athens 11635, Greece.
Dalton Trans. 2014 May 28;43(20):7429-34. doi: 10.1039/c3dt53338g.
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.
通过高分辨透射电子显微镜（HR-TEM）观察到，负载聚（酰胺胺）树枝状单元的改性多壁碳纳米管（MWCNTs）上固定有纳米尺寸的半导体硫化镉（CdS）。显然，已鉴定出直径为3-5纳米的球形CdS纳米颗粒。此外，能量散射X射线光谱（EDX）为CdS-MWCNTs杂化材料中CdS的存在提供了额外的光谱证据。通过监测罗丹明B（RhB）在554纳米处特征吸收带的光谱变化，研究了CdS-MWCNTs对RhB分解的光催化活性。发现在CdS-MWCNTs存在下进行可见光照射时，RhB的后一个吸收带持续下降，与仅存在参比CdS的情况相比，动力学速率更快。根据CdS-MWCNTs杂化体内从CdS到MWCNTs的有效光致电子转移，对当前结果进行了合理解释。在此框架下，所提出的RhB高效快速光催化分解机制支持电子在MWCNTs中的积累，然后电子与分子氧反应，从而将其还原为超氧自由基阴离子O2˙(-)，该阴离子负责生成高活性物种HO˙和HOO˙。后者与光激发的CdS中产生的空穴一起导致了RhB的分解。最后，光催化剂CdS-MWCNTs被回收并有效地连续重复使用四个催化循环，从而突出了其在从水中去除有机污染物方面更广泛的适用性。
