Efficient cooperative lubrication can be achieved via the introduction of core-shell structure lubricant additives with hard core and soft shell, for obtaining the expected anti-wear performance from the structural changes in the friction process. In this study, C@Ag microspheres with a core-shell structure were prepared by the redox method with carbon spheres as the core and Ag nanoparticles as the shell. Their tribological behaviors as base oil (G1830) additive with different concentrations were investigated in detail. Compared with base oil, the addition of C@Ag particles at 0.5 wt% can reduce the coefficient of friction (COF) and wear volume (Wv) up to 15.5% and 88%, respectively. More importantly, C@Ag particles provide superior lubrication performance to single additive (like carbon sphere (CS) and Ag nanoparticle). C@Ag core-shell particles contribute to the formation of tribo-film by melt bonding of flexible Ag and carbon sphere (CS) toward excellent self-repair performance and high-efficiency lubrication. Hence, core-shell structural nanoparticles with hard-core and soft-shell hold bright future for high-performance lubrication application.
A time- and energy- saving solution-based chemical precipitation method was developed to synthesize leaf-like CuO nanostructures. The morphology and size of the leaf-like CuO nanostructures could be simply manipulated by controlling the type and concentration of precursors, and the oriented attachment mechanism is responsible for the formation of leaf-like shape. With the concurrent reduction reaction and at appropriate concentration, CuO/Ag microspheres could be prepared and the growth mechanism is proposed. These two structures could serve as effective photocatalyst for the degradation of rhodamine B under visible light irradiation in the presence of hydrogen peroxide. Moreover, compared to pure CuO nanostructures, the photodecomposition activity of CuO/Ag microspheres increases by 42.9% due to plasmon-enhanced light absorption.
It is a challenging and valuable work to synthesize surface enhanced Raman scattering (SERS) substrate with low cost and high performance by simple methods, and use it to detect pesticide residues in food. Here, Ferrero® chocolate-like Cu 2 O@Ag microspheres (FRC-Cu 2 O@Ag) were fabricated by a facile in-situ redox reaction. Cu 2 O directly acted as templates and reducing agents to induce the nucleation and growth of Ag nanoparticles on the microspheres surfaces. The prepared semiconductor-noble metal hybrids of Cu 2 O@Ag were utilized as SERS substrates to detect 4-mercaptobenzoic acid (4-MBA) and thiram molecules. The distinguished SERS effect was achieved when target molecules absorbed on the FRC-Cu 2 O@Ag composite. The substrate presented excellent sensitivity and reproducibility for the detection of 4-MBA and thiram with the limit of 10 −10 and 10 −9 M, respectively. Due to combining both advantages of electromagnetic enhancement of Ag metals and chemical enhancement of Cu 2 O semiconductors, the obtained FRC-Cu 2 O@Ag microspheres provided a SERS platform to conveniently detect molecules with thiol groups. When it was applied to detect thiram residues on apple peel and the detection limit was 1.2 × 10 −7 M, low than maximal residue limit (MRL) of 7 × 10 −6 M in fruit prescribed by the U.S. Environmental Protection Agency (EPA).
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