Magnetic Rhodamine B-Imprinted Polyacrylamide pH Probe Using Resonance Rayleigh Scattering

A new nanosurface molecularly imprinted polyacrylamide nanoprobe (Fe₃O₄@MIP_B) for pH sensing was prepared by using Fe₃O₄ magnetic nanoparticles as a substrate, rhodamine B (RhB) as a template and sensing molecule, acrylamide (AM) as a functional monomer, and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The nanoprobe was characterized by scanning electron microscopy (SEM), hysteresis loop, Fourier transform infrared spectroscopy (FT-IR), and resonance Rayleigh scattering (RRS) spectroscopy. Fe₃O₄@MIP_B exhibited a strong RRS peak at 375 nm, and the sensing molecule RhB as the acceptor was enhanced with increasing pH in the pH range of 2.2-6.2, which enhanced the RRS-ET effect, resulting in a linear decrease in the RRS intensity at 375 nm. In the pH range of 7.0-9.8, the RRS intensity at 375 nm decreased linearly with increasing pH. Accordingly, a novel pH sensor platform was constructed for the detection of pH in Li River water samples and food samples, with relative standard deviations (RSDs) of 0.43-1.4 and 0.28-4.1%, respectively. In this study, a novel RhB-imprinted magnetic molecularly imprinted polymer was prepared, and it was combined with the RRS method to detect pH for the first time. High sensitivity, a wide pH detection range, and excellent selectivity and stability in complex matrices were demonstrated.