Abstract:

The genetic engineering Shewanella oneidensis (SO) strain was used as a biological template, to synthesize ternary SO/CdS/ZnO integrated photocatalysts, wherein, the recombinant SO strain could overexpress cysteine desulfurase for the extracellular growth of CdS nanoparticles by adding L-cysteine and cadmium ions, and zinc oxide nanoparticles were further loaded. The physicochemical properties of SO/CdS/ZnO photocatalysts were characterized by SEM, TEM, EDX, XRD, and XPS. The catalytic performance was evaluated in the photocatalytic degradation of organic dyes. The results showed that CdS and ZnO nanoparticles were uniformly loaded on the external surface of the recombinant SO strain. The as-prepared integrated nanocatalysts could effectively photodegrade organic dyes, and the amount of zinc source showed a significant effect on the degradation efficiency. When the amount of zinc acetate was 0.22g, the best photodegradation performance was achieved, e.g., the photodegradation efficiency of organic dyes could reach 100% within 60min. Moreover, the ternary integrated nanocatalysts could be reused 5 times with more than 80% of the original photodegradation efficiency. It was found that CdS nanoparticles could produce photogenerated electrons and holes under light irradiation, while ZnO nanoparticles inhibited the recombination of e^- and h⁺, and their synergistic effect improved the photodegradation efficiency. Accordingly, we provide a simple and feasible synthetic route for the multicomponent photocatalysts, and particularly we demonstrate that the assembly of semiconductor nanoparticles on the genetic engineering microorganisms as a platform has promising prospects in photocatalysis.

Key words: biotemplate, cadmium sulphide, zinc oxide, integrated catalyst, genetic engineering bacteria

摘要：

以希瓦氏菌基因工程菌（Shewanella oneidensis，SO）为生物模板载体，基于其过表达半胱氨酸脱硫酶的特性，利用外源添加半胱氨酸和镉离子在细菌表面合成并固定硫化镉纳米颗粒，再进一步负载氧化锌纳米颗粒，构建三元集成光催化剂（SO/CdS/ZnO）。采用SEM、TEM、EDX、XRD和XPS等技术对集成催化剂的理化性质进行充分表征；通过光催化降解染料实验评价其光催化性能。研究结果表明，CdS和ZnO纳米颗粒能够均匀负载在生物菌体外表面。所制备的集成催化剂能够有效光降解有机染料，并且锌源添加量对催化剂的降解效率有显著影响。当醋酸锌的添加量为0.22g时，集成催化剂的光降解效率最佳，有机染料在60min内光降解效率可达约100%。此外，集成催化剂重复使用5次后，光降解有机染料的效率仍能维持在80%左右。在有机染料降解过程中CdS纳米颗粒作为光吸收剂产生光生电子和空穴，而ZnO纳米颗粒抑制了光生电子和空穴对复合，双组分的协同作用提高了光降解效率。本文为构建多组分的集成光催化剂提供了简易可行的技术路线，证明了以基因工程菌为平台材料组装半导体纳米颗粒在光催化领域具有应用前景。

关键词: 生物模板, 硫化镉, 氧化锌, 集成催化剂, 基因工程菌