Solution-Based SERS Detection of Weak Surficial Affinity Molecules Using Cysteamine-Modified Au Bipyramids.

Area of Science:

• Nanotechnology
• Spectroscopy
• Analytical Chemistry

Background:

• Ultrasensitive detection of trace targets is crucial for various applications.
• Solution-based surface-enhanced Raman spectroscopy (SERS) requires efficient target molecule adsorption onto SERS-active surfaces.
• Weakly adsorbing molecules pose a significant challenge for current SERS detection methods.

Purpose of the Study:

• To develop a SERS-active substrate for ultrasensitive detection of trace targets, particularly those with weak affinity to gold surfaces.
• To investigate the effect of gold nano-bipyramid aspect ratio and concentration on SERS performance.
• To demonstrate a simple and rapid method for enhancing SERS detection sensitivity.

Main Methods:

• Preparation of cetyltrimethylammonium bromide (CTAB)-capped gold nano-bipyramids (Au BPs) with varying aspect ratios.
• Surface modification of Au BPs via ligand exchange using cysteamine to form cysteamine-capped gold nano-bipyramids (cyst-Au BPs).
• Application of cyst-Au BPs in solution-based SERS detection of pigment molecules with weak gold affinity.

Main Results:

• Cysteamine modification enabled hydrogen bonding with pigment molecules, inducing Au BP aggregation and local electromagnetic field enhancement.
• The aspect ratio and concentration of Au BPs significantly influenced SERS properties.
• Ultrasensitive SERS detection of weak-affinity molecules was achieved, with limits of detection as low as 0.1 ppb for allura red and 1 ppb for sunset yellow.

Conclusions:

• Cyst-Au BPs demonstrate significantly higher sensitivity for detecting weak-affinity molecules compared to CTAB-capped Au BPs.
• The proposed strategy offers a simple, fast, and highly sensitive approach for trace analysis of molecules with weak surface affinity.
• This method holds promise for advancing ultrasensitive detection capabilities in various analytical fields.