Role of 2‒13C Isotopic Glyphosate Adsorption on Silver Nanoparticles Based on Ninhydrin Reaction: A Study Based on Surface—Enhanced Raman Spectroscopy

Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. However, sensitivity in SERS experiments is quite low, caused by different orientation/conformation of the adsorbed molecules on the metal surface, which limit its detection by using SERS. In this paper, 2‒13C‒glyphosate (hereafter: 13–GLP) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Vibrational modes were assigned based on the modeling results obtained at the B3LYP/6-311++G** level by density functional theory (DFT) calculations, which were performed to predict the FT‒IR and Raman spectra. Band downshifts were caused by 13C atom isotopic substitution with mass changed. Moreover, SERS spectra of 13–GLP by combining ninhydrin reaction on Ag NPs were obtained. Isotopic Raman shifts are helpful in identifying the components of each Raman band through vibrations across the molecular system. They are coupled by probe molecules and thus bind to the substrates, indirectly offering the opportunity to promote interactions with Ag NPs and reduce the complex equilibrium between different orientation/conformation of glyphosate molecules on the metal surface.

On Some Issues of Handprints Detection and the Mechanism of Trace Formation on Porous Surfaces

Problems of detecting sweat and grease deposits on porous surfaces are common for forensic practice, and usually, they are successfully resolved with the help of chemical methods. Meanwhile, the interaction process in the system “porous surface – deposit – chemical agent" concerning clarification and identification of the trends within chemical reaction is not reviewed in literature sufficiently. For more comprehensive research of this process, the authors of the article have conducted multiple experiments on the ninhydrin reaction with the sweat and grease of the deposits, analyzed the interaction of the chemical agent with the sweat and grease, with the properties of porous (paper) materials using electron microscopy, and also looked into the display features of pore and edgeoscopic signs in the deposits under different storage conditions.As a result of the research, it is shown that such parameters of deposits carriers (paper) as porosity and hydrophilic properties and ambient humidity as well as the time of storage have a significant influence on the process of detecting the sweat and grease deposits on porous surfaces and their quality.

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

A camphor-derived sulfonimine with a conjugated carbonyl group, oxoimine 1 (O2SNC10H13O), reacts with amino acids (glycine, L-alanine, L-phenylalanine, L-leucine) to form a compound O2SNC10H13NC10H14NSO2 (2) which was characterized by spectroscopic means (MS and NMR) and supported by DFT calculations. The product, a single diastereoisomer, contains two oxoimine units connected by a –N= bridge, and thus has a structural analogy to the colored product Ruhemann´s purple obtained by the ninhydrin reaction with amino acids. A plausible reaction mechanism that involves zwitterions, a Strecker degradation of an intermediate imine and water-catalyzed tautomerizations was developed by means of DFT calculations on potential transition states.