Researchers at National Cheng Kung University, Taiwan, have shaped micro/nanostructured patterns using a physical process such as vertically sensitive nano-indentation or FIB (described here). These identified SERS-active substrates were applied for the detection or distinction of different viruses.

First, the SERS mechanism on these fibAu patterns is estimated by low-concentration molecular probes as the target molecules with respect to a suitable laser wavelength as the excitation source. Second, these SERS-active fibAu patterns are further optimized by considering geometrical, dimensional and spacing factors.

The results indicate that a hexagon-like fibAu pattern may induce a very high electromagnetic mechanism based on the availability of multiple edges and small curvature. By decreasing the dimensions from 300 to 150 nm, the laser-focused area contains an increasing number of micro/nanostructures and therefore intensifies the excitation of SERS signals.

If the geometry and dimensions of the micro/nanostructures are optimized, the relative intensity/surface area value may reach a maximum as the spacing approaches 22 nm. However, an exponential decrease is found as the spacing increases, which most probably results from the loss of electromagnetic effect.

Comparing the factors of geometry, dimension and spacing between two micro/nanostructures, a statistical analysis indicates that spacing is the dominant factor for the effect of SERS.

Third, the optimized fibAu pattern has been experimentally configured to detect the influenza virus. Based on the resulting SERS spectrum, the major part of the fingerprint information from the outermost surface of the influenza virus can be clearly assigned.

Accordingly, the group will now tailor these fibAu patterns and enable them for fast-screening detection of size-dependent or envelop-sensitive viruses.

The researchers presented their work in the journal Nanotechnology.