Self-sacrificial template synthesis of mixed-valence-state cobalt nanomaterials with high catalytic activities for colorimetric detection of glutathione

- A new type of mixed-valence-state cobalt nanomaterials was fabricated by a self-sacrificial template strategy, which possessed extremely high specific surface area and outstanding oxidase-like catalytic activity than other types of nanostructured Co3O4.
- The relationship between catalytic activity and the Co2+/Co3+ ratio was investigated for the first time.
- This new synthetic strategy provided an approach for regulating catalytic activity by changing the Co2+/Co3+ ratio.
- The proposed sensor was validated for the detection of glutathione in a health care product, eye drops.

Mixed-valence-state cobalt (MVSC) nanomaterials have attracted tremendous interest because of their extraordinarily high electron mobilities and catalytic activities. The design and synthesis of highly active MVSC nanomaterials with appropriate Co2+/Co3+ ratios are extremely desirable. In this work, MVSC nanomaterials with high surface areas and uniform size distributions were fabricated using a self-sacrificial template strategy. The MVSC nanomaterial with the optimum Co2+/Co3+ ratio showed excellent catalytic activity in the oxidation of 3,3′,5,5′-tetramethylbenzidine than other types of nanostructured Co3O4, e.g., nanoplates, nanorods, and nanocubes. Based on the catalytic activity of the MVSC nanomaterial, a simple and sensitive colorimetric sensor of glutathione (GSH) was developed due to the antioxidant ability of GSH. The linear range was 0.5-40 μM, and the limit of detection was 0.03 μM. The proposed sensor was used to determine GSH in eye drops and health care products. The recoveries ranged from 97.3% to 104.0%, indicating that the proposed colorimetric sensor for GSH quantification is reliable in practical applications.