Raman scattering

Raman spectroscopy

Adsorption

Composite number

Engineering

Nanoparticle

Materials science

Scattering

Molecule

Chemical engineering

Surface (topology)

Physics

Nanotechnology

Organic chemistry

Mathematics

Optics

Hydrothermal circulation

Geometry

Composite material

Chemistry

Nanostructure

Rhodamine 6G

Applied Surface Science

We used a simple two-step hydrothermal method to synthesize ZnO nanoflowers (NFs) evenly decorated with silver nanoparticles (NPs) and evaluated their efficiency as organic-molecule detectors during surface-enhanced Raman scattering (SERS). These three-dimensional (3D) hierarchically structured substrates exhibited high SERS sensitivity with respect to Rhodamine 6G (R6G), with the enhancement factor being as high as 107. And the characteristic peaks of R6G could be identified even at the concentration as low as 10−12 M. SERS maps collected through a point-by-point evaluation suggested that only some parts of the substrates could yield "hot spots," which exhibited extremely high spectral intensities even at relatively low concentrations of the analyte organic molecule. Owing to the synergistic effects of the hierarchically structured semiconductor nanocrystals and the metal NPs, the degree of increase in SERS was much higher than that in the case of Ag NPs alone. This could be ascribed to the high-intensity electromagnetic fields induced at the junction spots formed between the Ag NPs, the chemical enhancement properties of the ZnO NFs, and the ability of the 3D hierarchical nanostructures to create a large number of the adsorption sites and hot spots necessary for SERS.

ZnO/Ag composite nanoflowers as substrates for surface-enhanced Raman scattering