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.