Constructing a CdS QDs/silica gel composite with high photosensitivity and prolonged recyclable operability for enhanced visible-light-driven NADH regeneration

• Published in: Journal of colloid and interface science 2023-12, Vol.652, p.1043-1052
• Main Authors: Gao, Chun-Hui, Zhang, Shi-Ming, Feng, Fang-Fang, Hu, San-San, Zhao, Qian-Fan, Chen, Yong-Zheng
• Format: Article
• Language: English
• Subjects: adsorption; alcohol dehydrogenase; benzaldehyde; benzyl alcohol; bioactive properties; cadmium sulfide; catalytic activity; CdS QDs/silica gel composite; High photosensitivity; hydrogenation; light; lighting; NAD (coenzyme); NADH regeneration; Photo-enzyme catalysis; photocatalysts; photosensitivity; Prolonged recyclable operability; silica gel
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2023.08.090

Nicotinamide adenine dinucleotide (NADH) is a critical cofactor for many redox enzymatic reactions, however due to its high cost and stoichiometric consumption, in-situ regeneration is required to keep certain redox enzymatic reactions sustainable. In this work, a CdS quantum dots (QDs) embedded onto silicagel (CdS QDs/Silica gel) composite with high photosensitivity and recyclable operability was constructed for visible-light-driven NADH regeneration by a successive ionic layer adsorption reaction and ball milling method. The silicagel is employed as the loader for the CdS QDs formation and shielding agent. The CdS QD nanocrystals embedded into the silicagel loader can effectively protect themselves from photocorrosion and then enhance their structure stability. The obtained CdS QDs/Silica gel composites show the highest regeneration yields of NADH from 63.0% to 68.8% within 12 min. More importantly, CdS QDs/Silica gel composite photocatalysis can be reused for over 40 cycles, which is nearly 4 times of the bulk CdS. Finally, the in-situ regenerative NADH has excellent biological activity and can be used as the coenzyme for the enzymatic synthesis of benzaldehyde to benzyl alcohol by alcohol dehydrogenase (ADH). [Display omitted] Visible-light-driven nicotinamide adenine dinucleotide (NADH) regeneration is one of the most effective measures, and cadmium sulfide (CdS) materials are typically used as low-cost photocatalysts. The CdS photocatalysts, however, still suffer from low regeneration efficiency and poor cycle stability. In this work, the CdS quantum dots (QDs) less than 10 nm embedded onto silica gel (CdS QDs/Silica gel) were constructed for visible-light-driven NADH regeneration by a successive ionic layer adsorption reaction and ball milling method. Results demonstrate that the photosensitivity of the CdS QDs/Silica gel composite was 31 times higher than that of the bulk CdS. Moreover, the conduction band (CB) edge of the CdS QDs/Silica gel composite is −1.34 eV, which is more negative 0.5 eV than that of the bulk CdS. The obtained CdS QDs/Silica gel composites showed the highest NADH regeneration yields of 68.8% under visible-light (LED, 420 nm) illumination and can be reused for over 40 cycles. Finally, the bioactivity of NADH toward enzyme catalysis is further confirmed by the hydrogenation of benzaldehyde to benzyl alcohol catalyzed with an alcohol dehydrogenase as enzyme catalysis.