The effective chemical modification and self-assembly of diamond-based hierarchical composite materials are of key importance for a broad range of diamond applications. Herein, we report the preparation of novel core-shell diamond-based nanocomposites for dye adsorption toward wastewater treatment through a layer-by-layer (LbL) assembled strategy. The synthesis of the reported composites began with the carboxyl functionalization of microdiamond by the chemical modification of diamond@graphene oxide composite through the oxidation of diamond@graphite. The carboxyl-terminated microdiamond was then alternatively immersed in the aqueous solution of amine-containing polyethylenimine and carboxyl-containing poly acrylic acid, which led to the formation of adsorption layer on diamond surface. Alternating (self-limiting) immersions in the solutions of the amine-containing and carboxyl-containing polymers were continued until the desired number of shell layers were formed around the microdiamond. The obtained core-shell nanocomposites were successfully synthesized and characterized by morphological and spectral techniques, demonstrating higher surface areas and mesoporous structures for good dye adsorption capacities than nonporous solid diamond particles. The LbL-assembled core-shell nanocomposites thus obtained demonstrated great adsorption capacity by using two model dyes as pollutants for wastewater treatment. Therefore, the present work on LbL-assembled diamond-based composites provides new alternatives for developing diamond hybrids as well as nanomaterials towards wastewater treatment applications.

a Diamond@graphene oxide@gold nanoparticle (D@GO@AuNP) nanocomposite materials were synthesized by a modified Hummers method using diamond@graphite composites that were obtained by the spark plasma sintering treatment of diamond, and gold nanoparticles that were prepared from a solution of HAuCl 4 via reduction by NaBH 4 . The obtained diamond@graphene oxide utilized as a catalytic carrier has great advantages, such as high specific surface area and a porous structure, which provide more opportunities for the gold nanoparticles to access the catalytic carrier. In addition, the prepared hierarchical diamond-based D@GO@AuNP nanocomposites are beneficial to improve the catalytic capacity of gold nanoparticles with higher dispersion on the GO surface. Catalytic experiments with 4-nitrophenol and 2-nitroaniline were carried out using the synthesized D@GO@AuNP material. The obtained nanocomposites demonstrated excellent catalytic activity and high recyclability, without any decrease in the weight of gold nanoparticles after eight cycles of catalytic reduction, indicating the potential applications of the composite catalytic materials.

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