A new composite material based on alumina nanofibers and detonation nanodiamonds: synthesis, characterization, and sensing application

The development of inexpensive, easy-to-produce, and easy-to-use analytical tools for detection of harmful and toxic substances is a relevant research problem with direct applications in environmental monitoring and protection. In this work, we propose a novel composite material based on alumina nanofibers and detonation nanodiamonds for detection of phenol in aqueous medium. The composite material was obtained by mixing an aqueous suspension of alumina nanofibers with a diameter of 10-15 nm and a length of several microns and a hydrosol of nanodiamonds with an average cluster size of 70 nm. The mechanisms underlying the interaction of these nanomaterials are clarified and the physicochemical properties of the composite are investigated. The SEM and TEM studies show that the obtained composite has a network structure, in which clusters of nanodiamonds (10-20 nm in diameter) are distributed over the surface of nanofibers. Coupling of nanomaterials occurs due to opposite signs of their zeta potentials, which results in electrostatic attraction and subsequent chemical bonding as indicated by the X-ray photoelectron spectroscopy and simultaneous thermal analysis. The bonding apparently occurs between functional groups (mainly carboxyl) on the surface of nanodiamonds and amphoteric hydroxyl groups on the surface of alumina nanofibers. The proposed composite allows an easy-to-perform colorimetric analysis for qualitative and quantitative determination of phenol in aqueous samples with linear response over a wide range of concentrations (0.5-106 mu M). Multiple tests have shown that the composite is reusable and retains its catalytic function for at least 1 year during storage at room temperature.