A power-free single channel microfluidic device was designed for rapid and sensitive detection of cadmium (Cd 2+ ). Unmodified gold nanoparticles (AuNP) colloid was prepared by an electrochemical method to detect Cd 2+ into water upon colorimetric assay and electric resistance. The detection method based on color changes resulted from AuNP aggregation and their impact on surface Plasmon resonance. Colloidal solutions of AuNPs have high extinction coefficients and absorption band in the visible region of the UV-Visible spectrum. Its position depends upon the Au particle size and inter-particles distance. Therefore, a well-designed chemical interaction between the analytic and AuNPs surroundings resulted in aggregates and changes in surface plasmon resonance band position and width that lead to visual detection of Cd 2+ . These visual results could be observed by the naked eye when the mixture color changed from red in blue with Cd 2+ concentration. Optical property's changes with Cd 2+ concentrations in water were studied via UV-Visible spectrometer. Using PDMS surface modified to construct microfluidic device supported to get stable electric resistance values for AuNP colloid and Cd aqueous solution mixture. Electric resistance results accomplished with UV-Visble results could be employed to detect low ion concentrations in water (10 µM) sensitively.

A highly toxic heavy metal Cd2+ not only pollutes the environment but also poses a serious health risk to humans through water intake and food chains. Thus, to measure the concentration of Cd2+ with simplicity, sensitivity, and rapidity in tap water, soil, and rice is important particularly. In the work, an efficient sensor based on gold nanoparticles (AuNPs) modified with 3-(1H-Tetrazol-5-yl) aniline (TAA) for the colorimetric detection of Cd2+ is rationally proposed. The chelation between Cd2+ and TAA@AuNPs is characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible spectroscopy, Fourier transforms infrared (FTIR) and analyzed by Gaussian16w and Multiwfn simulations. The system color from wine-red to gray-blue with raising Cd2+ concentration resulted from the agglomeration of AuNPs with high anti-interference and selectivity, which could be visually perceived with the naked eye. The limit of detection (LOD) is 1.0 µM by the unaided eye, and 31 nM by UV-vis spectroscopy with the excellent linear relationship (R2 = 0.99049) in the range of 0.0 ~ 8.0µM (Cd2+ concentration) showing that AuNPs modified with TAA could serve as the quantitative determination of Cd2+. After testing the tap water, soil, and rice, it is considered that the new test way can be practically applied to the monitoring of harmful metal Cd2+ in environmental systems.

Mercury is unacceptable as a whitening agent in cosmetics because it is highly toxic and much harmful to the digestive, respiratory, circulatory, and nervous systems of humans. Therefore, it is of fundamental and practical importance to detect whether the concentration of mercury in cosmetics meets national standards. In this work, a new way for the simple visual and rapid colorimetric detection of Hg2+ using gold nanoparticle (AuNPs) modified with amrinone (3‐amino‐5‐pyridin −4‐yl‐1H‐pyridin‐2‐one, ALN) is proposed and characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV‐vis, Fourier transform infrared (FTIR) and analyzed of Gaussian16w and Multiwfn simulations. The solution colors changed from wine‐red to gray‐blue with increasing Hg2+ concentration resulting from the agglomeration of AuNPs with favorable anti‐interference and selectivity. The limit of detection (LOD) is 0.8 μmol/L by the unaided eye, and 18.2 nmol/L by UV‐vis spectroscopy with the excellent linear relationship (R2=0.9935) in the range of 0.0∼6.0 μmol/L (Hg2+ concentration), showing that AuNPs modified with ALN can serve as the quantitative determination of Hg2+. After testing actual samples, it is found that the test method can be practically applied to the monitoring of heavy metal mercury in cosmetics.

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