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A novel method based on surface-enhanced Raman scattering (SERS) was developed to estimate the reducing capacity of phenolic acids by using self-assembled three-dimensionally (3D) ordered gold nanoparticles (GNPs) precursor composite (SiO2/GNPs) arrays as nanoprobes. In the present work, the 3D ordered SiO2/GNPs arrays immersed in the growth solution containing different phenolic acids, the SiO2/GNPs were enlarged to varying degrees. Phenolic acids with one or more phenolic hydroxyl groups served as reductants for the growth of GNPs. The enlargement conditions varied with the different reducing capacity of phenolic acids, exhibiting specific morphologies differ from the complete gold nanoshells (GNSs). Consequently, the UV–vis spectra and SERS spectra for the phenolic acid-treated SiO2/GNPs arrays were gradually changed. The change of the intensities of the SERS spectra correlated well with phenolic acids concentration which indicated that this SiO2/GNPs array is a suitable SERS nanoprobe for phenolic acids. Results showed that the higher reducing capacity of phenolic acid, the stronger SERS of the enlarged GNSs. Thus, the SERS results could be used to evaluate the antioxidant capacity of phenolic acids by utilizing 3D ordered SiO2/GNPs arrays as nanoprobes. The results also indicated that the reducing capacity of these three phenolic acids was in the order gallic acid > syringic acid > vanillic acid. The detection ranges of vanillic acid, syringic acid and gallic acid were 10–250 µM, 10–110 µM and 5–55 µM, respectively.

A three-dimensional (3D) photocatalyst was synthesized through the self-assembly of graphitic carbon nitride (g-C3N4), TiO2, graphene (Gr), and carbon nanotubes (CNTs), in which both Gr and CNTs act as electron mediators, to form an all-solid-state g-C3N4/Gr-CNTs/TiO2 Z-scheme photocatalytic system. In this Z-scheme photocatalyst, the highly interconnected CNTs not only can effectively promote the transfer of photogenerated charge carriers, but also built a 3D open frame network to harvest more incident light and provide more specific surface area for photoreactions. Benefiting from the 3D nanostructure and Z-scheme system, phenol removal over g-C3N4/Gr-CNTs/TiO2 reached up to 90% within 120 min using a high-pressure Xe short-arc lamp as light source, which was much higher than that achieved over pure g-C3N4. The 3D Z-scheme photocatalyst fabricated in this study may be an attractive material for many environmental and energy-related applications.