Ultrasensitive and stable SERS detection by defect engineering constructed Ag@Ga-doped ZnO core-shell nanoparticles

There has been increasing interest in evolution of semiconductor-based SERS-active substrates to achieve ul-trasensitive detection of trace analyte molecules. This work presents a simple solvothermal method and further defect engineering technology to obtain Ag@Ga-doped ZnO core-shell nanoparticles (Ag@n%Ga-ZnO CSNPs), which have both local electromagnetic enhancement from Ag-core and efficient charge transfer enhancement due to the plasmon and photo-induced electrons and numerous deficiency sites after Ga-doping, for achieving ultrahigh detection sensitivity, stability and repeatability. Specifically, the unique Ag@2.6%Ga-ZnO CSNPs exhibited good linearity in the range from 10-6 to 10-12 M for the typical dye analyte rhodamine 6G (R6G), and the limit of detection could be down to 10-12 M. The Raman signal intensity of the Ga-doped core-shell structure was stable after 60 days of storage at room temperature. Moreover, the as-prepared Ag@2.6%Ga-ZnO CSNPs shows excellent signal repeatability as SERS substrate, and the relative standard deviation (RSD) is calculated to be about 9.71%. To illustrate the usefulness for detection of hazardous substance, we showed that such substrate can detect a pesticide, thiram, at a concentration as low as 10-9 M, which is far lower than the national standard. In addition, due to the construction of the core-shell structure and the introduction of Ga-doping, the photo-electric properties of the material have also been greatly improved. Under the irradiation of xenon lamp, the Ag@2.6%Ga-ZnO CSNPs can complete catalytic degradation of organic dye molecule R6G and pesticide molecule thiram within 40 to 50 min. This study demonstrated that the Ag@Ga-doped ZnO core-shell nanoparticles could serve as an effective and versatile SERS platform for reproducible, fast and in-field detection of organic analytes at trace levels.

Automated summary

This study presents the synthesis of Ag@Ga-doped ZnO core-shell nanoparticles (Ag@n%Ga-ZnO CSNPs) using a solvothermal method and defect engineering technology. The nanoparticles show both local electromagnetic enhancement and efficient charge transfer enhancement, enabling ultrahigh detection sensitivity, stability, and repeatability in surface-enhanced Raman scattering (SERS) detection. The Ag@2.6%Ga-ZnO CSNPs exhibit good linearity in the detection range of 10-6 to 10-12 M for the dye analyte rhodamine 6G (R6G), with a limit of detection of 10-12 M. The nanoparticles also demonstrate excellent signal repeatability and catalytic degradation of organic dye and pesticide molecules.