A low-cost microcontrolled photometer with one color recognition sensor for selective detection of Pb2+ using gold nanoparticles
The present work describes a microcontrolled photometer based on light-emitting-diodes (LEDs) for detection of Pb2+ using gold nanoparticles (AuNPs). The photometer makes use of a single LED as a light source, a sensor TCS230 (TAOS, USA) and an Arduino electronic card as an acquisition system. On the sensor, the light from the three closely adjoined red, green, and blue LEDs composing the “white” light source LED is contact-coupled to the map-illumination pointed toward the detection cell. To maintain a constant light intensity, a common white-color LED (emitting a 450–620 nm continuous spectrum) was employed as a controllable light source. Software was written in C++ to control the photometer through a USB interface and for data acquisition. Pb2+ measurements are based on the color change of AuNPs due to their aggregation provoked by Pb2+. The method showed excellent selectivity for Pb2+ compared to other 19 metal ions (Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Hg+, K+, Li+, Mg2+, Mn2+, Na+, Ni2+, Sn2+, Sr2+, and Zn2+). Pb2+ was detected with the photometer and also monitored via UV-Vis. Solutions containing Pb2+ in the concentration range from 0.6 to 10 mmol L−1 were employed to construct the analytical curves, proving a limit of detection (LOD) of 0.89 mmol L−1. The sensitivity was compared to that obtained with a UV-Vis spectrophotometer at 520 nm. A repeatability of 4.11% (expressed as the relative standard deviation of 10 measurements) was obtained. The proposed method was successfully applied to detect Pb2+ in spiked water samples.