Process Optimization of Silver Nanoparticle Synthesis and Its Application in Mercury Detection

Abstract

Silver nanoparticles (AgNPs) have stable reactivity and excellent optical absorption properties. They can be applied in various industries, such as environmental protection, biochemical engineering, and analyte monitoring. However, synthesizing AgNPs and determining their appropriate dosage as a coloring substance are difficult tasks. In this study, to optimize the process of AgNP synthesis and obtain a simple detection method for trace mercury in the environment, we evaluate several factors—including the reagent addition sequence, reaction temperature, reaction time, the pH of the solution, and reagent concentration—considering the color intensity and purity of AgNPs as the reaction optimization criteria. The optimal process for AgNP synthesis is as follows: Mix 10 mM of silver nitrate with trisodium citrate in a hot water bath for 10 min; then, add 10 mM of sodium borohydride to produce the AgNPs and keep stirring for 2 h; finally, adjust the pH to 12 to obtain the most stable products. For AgNP-based mercury detection, the calibration curve of mercury over the concentration range of 0.1–2 ppb exhibits good linearity (R2 > 0.99). This study provides a stable and excellent AgNP synthesis technique that can improve various applications involving AgNP-mediated reactions and has the potential to be developed as an alternative to using expensive detection equipment and to be applied for the detection of mercury in food.

Design of an Integrated Microfluidic Paper-Based Chip and Inspection Machine for the Detection of Mercury in Food with Silver Nanoparticles

“…The formation of AgNPs is related to the reaction conditions. The procedure for this experiment can be found in our previous report [ 41 ]. The measured particle size was in the range of 20–110 nm, and the size with the highest frequency was approximately 47 nm, similar to the results obtained using a nanoparticle size analyzer [ 45 ].…”

“…Our previous research reported that linearity is the evaluation criterion for the best volume ratio, and 400 nm absorbance is used as the observation condition. The best volume ratio of reagents is 1:0.5, in order to achieve a linearity of at least R2 > 0.99 [ 41 ]. As the standard concentration of mercury increases, the color produced by the reaction between AgNPs and mercury gradually changes from yellow to light yellow and finally becomes transparent through the adsorption of mercury ions into AgNPs to form amalgam crystals [ 45 , 51 ].…”

“…The reaction volume ratio between the color reagent and test substance influences the color change result. For this experiment, we followed the procedure in a previous research report [ 41 ]. First, the two reagents were mixed at the same volume ratio, which was set as the initial test condition.…”

Strategies in Improving Sensitivity of Colorimetry Sensor Based on Silver Nanoparticles in Chemical and Biological Samples

“…The formation reaction of silver nanoparticles was compared with the use of hot water and an ice bath. When using hot water, the characteristic of the color and absorption is better than in cold water [55].…”

“…Fu et al [55], that use silver nanoparticles as a colorimetric sensor for mercury detection in the environment, also evaluated several factors optimization on the formation of AgNPs, including reaction temperature. The formation reaction of silver nanoparticles was compared with the use of hot water and an ice bath.…”