Meniscus-confined capping-free 3D printed gold nanoparticles for quantitative SERS detection of bisphenol A

Abstract

Exposure to plasticizers may lead to serious health problems in humans; hence, a rapid technique to quantitatively detect their ultra-low concentrations is highly required. The surface-enhanced Raman spectroscopy (SERS) technique has gained popularity regarding plasticizer detection. The present study demonstrated meniscus-confined electrochemically 3D printed capping agent-free gold nanoparticles (3DPAu) as a SERS substrate for quantitatively detecting one of such common plasticizers, bisphenol A (BPA). The 3DPAu substrates of 14 nm size are fabricated using a meniscus of 0.8 mm size at 0.4 mm s⁻¹ printing speed and 2.5 V potential using the localized redox chemistry process. The 3DPAu substrates are fabricated without using any capping agents, which helps in enhancing their SERS activity as the capping agents increase the gap between the metal nanoparticles and analyte molecules, which in turn results in abrupt decay of the enhancement in the Raman signal. The BPA detection limit is as low as 0.25 ppm, lower than the standard value prescribed for human intake (0.6 ppm). The 3DPAu electrodes showed excellent repeatability (tested 36 times) and reproducibility (tried 5 times). The relative standard deviation (RSD) values for repeatability and reproducibility are only 4.9 and 2.6%, respectively. The ability to retain up to 89% of the initial SERS signal value, even after a long period of 7 weeks, indicated the long-term stability of the 3DPAu substrates. Furthermore, the leached-out BPA concentration from the commercial plastic products is also quantified to test the suitability of 3DPAu substrates for analyzing actual samples. This work also proposes a possible mechanism for BPA SERS detection through 3DPAu substrates.