Label-free highly sensitive probe detection with novel hierarchical SERS substrates fabricated by nanoindentation and chemical reaction methods

Abstract

Nanostructures have been widely employed in surface-enhanced Raman scattering (SERS) substrates. Recently, in order to obtain a higher enhancement factor at a lower detection limit, hierarchical structures, including nanostructures and nanoparticles, appear to be viable SERS substrate candidates. Here we describe a novel method integrating the nanoindentation process and chemical redox reaction to machine a hierarchical SERS substrate. The micro/nanostructures are first formed on a Cu(110) plane and then Ag nanoparticles are generated on the structured copper surface. The effect of the indentation process parameters and the corrosion time in the AgNO 3 solution on the Raman intensities of the SERS substrate with hierarchical structures are experimentally studied. The intensity and distribution of the electric field of single and multiple Ag nanoparticles on the surface of a plane and with multiple micro/nanostructures are studied with COMSOL software. The feasibility of the hierarchical SERS substrate is verified using R6G molecules. Finally, the enhancement factor using malachite green molecules was found to reach 5.089 × 10 9 , which demonstrates

Fabrication of nano/microstructures for SERS substrates using an electrochemical method

“…A single-cavity structure can significantly enhance the Raman signal [ 48 – 50 ]. Chang et al [ 48 ] fabricated cavities by using an indentation method and found that the Raman intensities of R6G were influenced by indentation depth and tip-to-tip displacement.…”

“…Chang et al [ 48 ] fabricated cavities by using an indentation method and found that the Raman intensities of R6G were influenced by indentation depth and tip-to-tip displacement. In our previous studies [ 49 – 50 ], a cavity depth of 1.7 µm was generated using a normal force of 10 mN with the force modulation indentation method. However, nanocavities were formed by the overlap of adjacent cavities.…”

Study of the Fabrication of Gold Nanoparticle–Graphene-Arrayed Micro/Nanocavities as SERS Substrates Compared to Two Different Angles of Triangular Pyramid Tips

“…SERS amplifies Raman signals to detect molecules with low concentrations and obtain the spectral fingerprints of molecules using a single excitation light source. SERS substrates have been employed in many fields, including environmental quality monitoring, medical diagnosis, food analysis, and other aspects of detection. − At present, researchers generally believe that the causes of SERS are electromagnetic enhancement and chemical enhancement. , In electromagnetic enhancement, localized surface plasmon resonance plays a non-negligible role, and its strength is affected by several factors, such as the shape, size, and distribution of the SERS substrate . The chemical enhancement is due to the movement of electric charges and the interaction between the different molecules and the different SERS substrates.…”

“…Nanocavities with good uniform are obtained by using this method. For example, Chang and Zhang used the Berkovich tip and the cube-corner tip to machine triangular pyramid cavities as SERS substrates, respectively. ,− Chang et al fabricated six different arrayed cavities with different depths and spaces on a coated Au/Si surface using the Berkovich tip. The SERS performance of arrayed structures with the depth of 90 nm and the space of adjacent cavities of 500 nm is better than that of other structures.…”

“…The enhancement factor of R6G molecules ranged from 7.5 × 10 5 to 6 × 10 6 . The cavities and Ag nanoparticles as SERS substrates were machined by combining nanoindentation with redox reaction methods, and the 10 –7 mol/L MG solution was detected …”