Zinc oxide/graphene composite for the selective SPME of sulfur compounds

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Zinc oxide has been used as coating in solid phase microextraction (SPME) due to its good properties including thermal stability and affinity towards different analytes. In this sense, ZnO presents a high interaction with sulfur-containing molecules due to the strong coordination between Zn and S. However, this interaction is not completely exploited in SPME since pure ZnO coatings, prepared by sol-gel procedures, have a low surface area due to the enwrapping of ZnO nanoparticles (NPs) in the sol-gel network. In a recent article accepted for publication in Journal of Chromatography A, researchers from the Sun Ya-sen University at China have proposed a new approach to avoid this shortcoming. The proposal consists of the use of graphene as ZnO NPs support.

The ZnO NPs are grown in the graphene (G) surface producing a composite which is final attached to a silica fiber by a sol-gel reaction in order to prepare the SPME coating. The whole synthetic procedure is described in detail in the article so the discussion will be focused only in several key-steps. First of all, the combination of ZnO and graphene is produced in the form Zn(OH)2/graphene oxide (GO) using precursors that can be easily dispersed in an aqueous media. The composite is later on immobilized by a sol-gel reaction producing a Zn(OH)2/GO coating in a silica fiber. The final coating is subsequently desiccated at high temperature and reduced using hydrazine transforming the original coating into ZnO/GO and ZnO/G, successively.

The synthesized coating has a BET area of 169.4 m2/g which is higher than the obtained with the pure ZnO coating (only 1.2 m2/g). The presence of G provides a higher surface area and the ratio ZnO/G marks the selectivity of the coating towards sulfur-containing molecules. In fact, the new coating has been compared with classical fibers (PDMS and PDMS/DVB) providing a better selectivity and it has been finally applied to the determination of sulfides in some samples.

Readers are referred to the original article where they will find the description of the synthetic procedure and the coating characterization. Special attention should be given to Figure 1 of the manuscript which clearly explains the role that graphene plays.

References
(1) Graphene-Supported Zinc Oxide Solid-Phase Microextraction Coating with Enhanced Selectivity and Sensitivity for the Determination of Sulfur Volatiles in Allium Species. Link to the article

Related posts
(1) Zinc oxide nanorods for the solid phase microextraction of volatile aldehydes. Link to the post
(2) Graphene as coating in solid phase microextraction. Link to the post

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