锰掺杂硫化锌量子点LED蓝光灯光催化还原六价铬

通过共沉淀法合成了锰掺杂硫化锌量子点(ZnS∶Mn QDs)，该催化剂可在450 nm LED蓝光灯下光催化还原Cr(Ⅵ)。采用TEM、XRD、PL分别对ZnS∶Mn QDs的形貌、物相和发光特性进行了表征，结果表明：ZnS∶Mn QDs的尺寸小于10 nm；Mn掺杂没有改变ZnS的晶体结构；ZnS在掺杂Mn后，可在598 nm处产生橘黄色荧光。UV-vis表征结果显示，与纯ZnS相比，ZnS∶Mn QDs具有更强的光吸收能力。考察了不同因素对光催化效果的影响。结果表明，Mn掺杂浓度3%较为合适，酸性pH有利于光催化反应。当Cr(Ⅵ)浓度为25 mg·L⁻¹，pH为5.8时，光催化25 min后Cr(Ⅵ)去除率为99%。与其他光催化剂还原Cr(Ⅵ)相比，ZnS: Mn QDs使用低能耗LED灯作为光源，催化速率高，且能够吸附还原产物Cr(Ⅲ)。探究了光催化机理，发现在450 nm光激发下，Mn²⁺自身能级⁴T₁→⁶A₁发生跃迁产生光生电子，Cr(Ⅵ)捕获光生电子被还原，价带上余留的空穴参与水的氧化。结合表征结果，ZnS可通过掺杂Mn离子改善光吸收能力提高光催化还原Cr(Ⅵ)的性能。

Photocatalytic reduction of hexavalent chromium by manganese-doped zinc sulfide quantum dots under the LED bule light irradiation

The manganese-doped zinc sulfide quantum dots (ZnS∶Mn QDs) were synthesized by co-precipitation method, this catalysts had a good photocatalytic performance on photoreduction of Cr(Ⅵ) under 450 nm blue light irradiation. TEM images showed that the size of ZnS∶Mn QDs was below 10 nm. XRD patterns indicated that Mn doping did not change the crystal structure of ZnS. From the PL spectrum, the ZnS∶Mn QDs produced orange fluorescence at 598 nm under light irradiation. UV-vis characterization showed that ZnS∶Mn QDs had stronger light absorption capacity than pure ZnS. The influences of different factors on photocatalysis were investigated. The results showed that the suitable Mn dopant concentration was 3%, and acidic pHs were conducive to photocatalysis. When the concentration of Cr(Ⅵ) was 25 mg·L−1 and pH was 5.8, the removal rate of Cr(Ⅵ) was 99% after 25 min photocatalysis. Compared with other photocatalysts, ZnS∶Mn QDs could use low-energy LED lamps as light sources, had higher catalytic rate to Cr(Ⅵ) reduction, and could adsorb the reduction product Cr(Ⅲ). Photocatalytic mechanism was following: the 4T1→6A1 transition of Mn2+ was excited to generate photogenerated electrons under 450 nm light irradiation, then Cr(Ⅵ) could capture the photogenerated electrons for itself reduction. Meanwhile, the photogenerated holes left in the valence band participated in water oxidation. Combined with the characterization results, Mn ions doping could improve the ZnS light absorption capacity and enhance the performance of photoreduction of Cr(Ⅵ).