SERS-substrates based on ZnO nanoflowers prepared by green synthesis

ZnO nanoparticles (NPs) with a flower-like morphology, synthesized by an affordable colloidal route using an aqueous fungi extract of Ganoderma lucidum as a reducing agent and stabilizer, are investigated as SERSsubstrate. Each flower has large effective surface that is preserved at packing particles into a dense film and thus exhibits an advantageous property for SERS and similar sensing applications. The mycoextract used in our low-cost and green synthesis as surface stabilizer allows subsequent deposition of metal NPs or layers. One type of SERS substrates studied here was ZnO NPs decorated in situ in the solution by Ag NPs, another type was prepared by thermally evaporating Ag layer on the ZnO NP film on a substrate. A huge difference in the enhancement of the same analyte in the solution and in the dried form is found and discussed. Detection down to 10- 7 M of standard dye analytes such as rhodamine 6G and methylene blue was achieved without additional optimization of the SERS substrates. The observed SERS-activity demonstrate the potential of both the freestanding flower-like ZnO NPs and thereof made dense films also for other applications where large surface area accessible for the external agent is crucial, such as catalysis or sensing.

Automated summary

In this study, flower-like zinc oxide nanoparticles (NPs) were synthesized using a cost-effective colloidal route with Ganoderma lucidum extract. These NPs demonstrated advantageous properties for surface-enhanced Raman spectroscopy (SERS) and other sensing applications due to their large effective surface area. The use of mycoextract as a surface stabilizer allowed for subsequent deposition of metal NPs or layers. The SERS activity of the ZnO NPs was demonstrated through the detection of standard dye analytes without additional optimization of the substrates. The observed results highlight the potential of these freestanding ZnO NPs and their dense films for various applications, including catalysis and sensing.