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With the development of nanotechnology, the preparation method of surface-enhanced Raman scattering (SERS) substrate has made significant progress, which promotes the application of SERS in food safety, environmental protection, and medical testing. We reported on the fabrication of silver-coated magnetic Fe3O4@phenolic resin (Fe3O4@RF) core–shell particles by a facile solvothermal method, followed by deposition of high-density Ag nanoparticles onto the phenolic resin surfaces through an in-situ reduction process. Analysis of Raman spectroscopy was performed by laser Raman spectrometer. The as-synthesized Ag-coated Fe3O4@RF particles as sensitive SERS substrates showed outstanding SERS performances toward probe molecules of 4-aminothiophenolas with a detection limit of 1 × 10–9 mol L–1. Moreover, the enhancement factor of the substrate was calculated to be about 2.86 × 105. Importantly, profiting from the excellent magnetism, the signal attenuated slightly only after three cycles measurements of SERS based on such composite substrates, indicating that Fe3O4@RF@Ag magnetic composite microspheres possessed the outstanding repeatability. On the basis of these results, it is believed that such Fe3O4@RF@Ag substrates are promising for the reusable detection of toxic molecules in practical applications.

Purpose For oil film thickness measurement using ultrasonic spring model, obtaining the isolated reflection from the oil film layer is the key point. While for oil film thickness measurement in thrust bearings with thin liner, the reflection from the substrate-Babbitt interface will overlap with the reflection from the oil film layer. This overlapping will render the ultrasonic spring model invalid. To obtain the isolated reflected signal from the oil film layer accurately, an adaptive method was developed to recover the overlapping echoes. Design/methodology/approach A genetic-algorithm-based support matching pursuit (GA-based SMP) was developed to provide the optimal echo number and initial parameters guesses automatically and efficiently. Then, the traditional expectation maximization (EM) model was used to fine tune the accurate results. Findings The developed method was tested using both simulated echoes and the overlapping echoes encountered in the ultrasonic oil film thickness measurement of thrust bearings. The results demonstrated that the developed method performed well on recovering overlapping echoes adaptively. Originality/value The work shows an adaptive method to recover the ultrasonic overlapping echoes. When used in ultrasonic oil film thickness measurement, it can help extend the application of traditional ultrasonic spring model to objects with four or more layers.

Ultrasonic method is promising in oil film thickness measurement, while the commonly used commercial transducers are bulky and then sometimes hinder the application of this technology in field. Using the piezoelectric element is an alternative method and has the advantage of being convenient to be fixed. In this work, the key points of the use of the piezoelectric element are summarized. A calibration rig is set up to test the performance of oil film thickness measurement using piezoelectric element. The results show that using the piezoelectric element can measure the oil film thickness effectively and accurately.