Controlled Synthesis of Hyperbranched Gold Nanostars Using Gallic Acid and Triton X-100 to Develop SERS Nanosubstrates

Hyperbranched gold nanostars (h-AuNSs) with highly generated electromagnetic fields (EMF) are consistently favored and researched in surface-enhanced Raman scattering (SERS) substrates. This unique morphology enables a broader detection range for various analyte molecules through the local surface plasmon resonance effect, spanning from the visible to the near-infrared region. However, synthesizing gold nanostars (AuNSs) necessitates strict control over reaction conditions, along with specific reducing and structure-directing agents, which often results only in the formation of star-like structures with short branches. This research introduces an alternative approach to traditional reducing agents and surfactants, such as ascorbic acid and cetyl trimethyl ammonium bromide. It details a modified seed-mediated method for efficiently synthesizing AuNSs with a very small core (≈25 ± 5 nm) and elongated branches (h-AuNSs) with a length growth of ≈115 ± 8 nm, employing gallic acid as the reducing agent and Triton X-100 as the surfactant. This method produce high-quality, reproducible long-branch AuNSs for SERS substrates for detecting trace organic dye, crystal violet, detection limits of 11.76 ppm and quantification limits of 35.65 ppm. Moreover, the prepared h-AuNSs shows excellent reproducibility with only 4.58% variability across 20 points at 40 ppm. These novel nanomaterials could enable many applications in SERS.