Preparation of reagent indicator papers with silver triangular nanoplates for chemical analysis

Preparation of Reactive Indicator Papers Based on Silver-Containing Nanocomposites for the Analysis of Chloride Ions

In recent decades, metal-containing nanocomposites have attracted considerable attention from researchers. In this work, for the first time, a detailed analysis of the preparation of reactive indicator papers (RIPs) based on silver-containing nanocomposites derived from silver fumarate was carried out. Thermolysis products are silver-containing nanocomposites containing silver nanoparticles uniformly distributed in a stabilizing carbon matrix. The study of the optical properties of silver-containing nanocomposites made it possible to outline the prospects for their application in chemical analysis. RIPs were made by impregnating a cellulose carrier with synthesized silver fumarate-derived nanocomposites, which change their color when interacting with chlorine vapor. This made it possible to propose a method for the determination of chloride ions with preliminary oxidation to molecular chlorine, which is then separated from the solution by gas extraction. The subsequent detection of the active zone of RIPs using colorimetry makes it possible to identify mathematical dependences of color coordinates on the concentration of chloride ions. The red (R) color coordinate in the RGB (red-green-blue) system was chosen as the most sensitive and promising analytical signal. Calibration plots of exponential and linear form and their equations are presented. The limit of detection is 0.036 mg/L, the limits of quantification are 0.15-2.4 mg/L, and the time of a single determination is 25 min. The prospects of the developed technique have been successfully shown in the example of the analysis of the natural waters of the Don River, pharmaceuticals, and food products.

Silver Itaconate as Single-Source Precursor of Nanocomposites for the Analysis of Chloride Ions

At present, conjugated thermolysis of metal-containing monomers is widely used as single-source precursors to obtain new metal- and metal oxide-containing nanocomposites. In this study, a detailed analysis of the main stages of conjugated thermolysis of silver itaconate was carried out. The obtained nanocomposites containing silver nanoparticles are evenly distributed in a stabilizing carbon matrix. The structural characteristics and properties of the resulting nanomaterials were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). We have developed a method of test analysis of chlorides using paper modified with the obtained silver-containing nanocomposites. The analysis technique is based on the in situ conversion of chlorides to molecular chlorine, its dynamic release, and colorimetric detection using NP-modified paper test strips. A simple installation device is described that allows this combination to be realized. The proposed approach seems promising for nanoparticle-based determinations of other analytes that can be converted into volatile derivatives.

An improved step-by-step airflow/paper-based colorimetric method for highly selective determination of halides in complex matrices

An improved step-by-step colorimetric method for determination of halides has been developed. The method is based on successive selective oxidation of iodide, bromide and chloride into corresponding free halogens, their extraction by airflow and colorimetric detection with different paper test-strips. This procedure can be performed in a single analyzed solution and possesses high selectivity and good sensitivity due to the extraction step. Three types of paper test-strips were examined: paper modified with tetramethylammonium iodide and starch, paper modified with methyl orange and paper modified with silver triangular nanoplates. Limits of detection for iodide, bromide and chloride are 0.01, 0.02, and 0.04 mg L^-1 respectively in case of the last mentioned paper. The method was applied to the analysis of samples having complex matrices, such as various seafood, preserves, bread, and natural waters, showing good accuracy of the analysis with recoveries of 95-105% and relative standard deviations not higher than 6%.