Part-Per-Billion Level Chemical Sensing with a Gold-Based SERS-Active Substrate.

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Nanotechnology

Background:

• Surface-enhanced Raman spectroscopy (SERS) offers sensitive detection for trace chemical analysis.
• Portable SERS devices are crucial for applications in law enforcement, medicine, environmental monitoring, and food quality control.
• Developing robust SERS sensors is key to realizing these applications.

Purpose of the Study:

• To develop and benchmark a portable SERS sensor for caffeine detection and quantification.
• To evaluate the sensor's sensitivity, concentration dependence, and reproducibility.
• To investigate the influence of pH on SERS measurements of caffeine.

Main Methods:

• Utilized a SERS-active substrate with gold nanoparticles in a porous glass matrix.
• Measured aqueous caffeine solutions to determine Lowest Measured Concentration (LMC) and Limit of Detection (LOD).
• Constructed calibration curves and assessed sensor performance at pH 3, 7, and 11.

Main Results:

• Achieved a Lowest Measured Concentration (LMC) of 50 parts per billion (ppb) for caffeine.
• Determined an estimated Limit of Detection (LOD) of 0.63 ppb.
• Demonstrated sensor stability and reproducible measurements across a wide pH range (3-11).

Conclusions:

• The developed SERS sensor is highly sensitive and stable for caffeine detection.
• The sensor's performance is reliable under varying pH conditions, suitable for diverse analytical applications.
• First-time vibrational assignments for caffeine on a gold SERS substrate are reported.