Conjugated Thermolysis of Metal-Containing Monomers: Toward Core–Shell Nanostructured Advanced Materials

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.

Preparation of FeCo/C-N and FeNi/C-N Nanocomposites from Acrylamide Co-Crystallizates and Their Use as Lubricant Additives

FeCo and FeNi nanoalloy particles encapsulated in a nitrogen-doped carbonized shell (FeCo/C-N and FeNi/C-N) were synthesized by thermolysis at 400 °C of polyacrylamide complexes after frontal polymerization of co-crystallizate of Fe and Co or Ni nitrates and acrylamide. During the thermolysis of polyacrylamide complexes in a self-generated atmosphere, Co(II) or Ni(II) and Fe(III) cations are reduced to form FeCo and FeNi nanoalloy particles, while polyacrylamide simultaneously forms a nitrogen-doped carbon shell layer. This unique architecture provides high chemical and thermal stability of the resulting nanocomposites. The average crystallite size of FeCo and FeNi nanoparticles is 10 and 12 nm, respectively. The nanocomposites were studied by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The nanocomposites have been tested as antifriction and antiwear additives in lubricating oils. The optimal concentrations of nanoparticles were determined, at which the antifriction and antiwear properties of the lubricant manifest themselves in the best possible way.