Microfluidic synthesis of gold nanoparticle-doped microspherical photonic crystal as SERS substrate for methylene blue detection

A novel microfluidic approach is presented for the one-step synthesis of gold nanoparticle-doped microspherical photonic crystal (AuNP–MPC) for ultrasensitive surface-enhanced Raman spectroscopy (SERS) detection of methylene blue (MB), a common environmental pollutant. The AuNP–MPC microspheres exhibited excellent SERS activity due to the surface plasmon resonance of Au nanoparticles. And the SERS signal was significantly enhanced by strategically manipulating the photonic band gap (PBG) of the AuNP–MPC microspheres to achieve optimal overlap with the excitation laser wavelength. The SERS signal of MB was significantly enhanced by this, reaching an EF as high as 3.03 × 10⁶. The AuNP–MPC microspheres demonstrated rapid adsorption of MB within just 5 min, making them suitable for rapid detection applications. Notably, the limit of quantification was as low as 1 × 10⁻⁸ mol/L, highlighting the exceptional sensitivity of this approach. Furthermore, the AuNP–MPC microspheres exhibited excellent homogeneity, reproducibility, and stability of SERS signals, which are crucial qualities for practical SERS applications. This work presents a promising avenue for developing SERS-active microfluidic platforms for the rapid detection of trace organic pollutants in environmental monitoring.

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