The present study was conducted to prepare and investigate
large-area,
high-sensitivity surface-enhanced Raman scattering (SERS) substrates.
Organic/inorganic nanohybrid dispersants consisting of an amphiphilic
triblock copolymer (hereafter referred to simply as “copolymer”)
and graphene oxide (GO) were used to stabilize the growth and size
of gold nanoparticles (AuNPs). Ion–dipole forces were present
between the AuNPs and copolymer dispersants, while the hydrogen bonds
between GO and the copolymer prevented the aggregation of GO, thereby
stabilizing the AuNP/GO nanohybrids. Transmission electron microscopy
(TEM) revealed that the AuNPs had particle sizes of 25–35 nm
and a relatively uniform size distribution. The AuNP/GO nanohybrids
were deposited onto the glass substrate by using the solution drop-casting
method and employed for SERS detection. The self-assembling properties
of two-dimensional sheet-like GO led to a regular lamellar arrangement
of AuNP/GO nanohybrids, which could be used for the preparation of
large-area SERS substrates. Following removal of the copolymer by
annealing at 300 °C for 2 h, measurements were obtained under
scanning electron microscopy. The results confirmed that 2D GO nanosheets
were capable of stabilizing AuNPs, with the final size reaching approximately
40 nm. These AuNPs were adsorbed on both sides of the GO nanosheets.
Because the GO nanosheets were merely 5 nm-thick, a good three-dimensional
hot-junction effect was generated along the z-axis
of the AuNPs. Lastly, the prepared material was used for the SERS
detection of rhodamine 6G (R6G), a commonly used highly fluorescent
dye. An enhancement factor (EF) of up to 3.5 × 106 was achieved, and the limit of detection was approximately 10–10 M. Detection limits of 10–10 M
and < 10–10 M were also observed with the detection
of Direct Blue 200 and the biological molecule adenine. It is therefore
evident that AuNP/copolymer/GO nanohybrids are large-area flexible
SERS substrates that hold great potential in environmental monitoring
and biological system detection applications.