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Through computational analysis we found that pentazine and hexazine, two hypothetical high-energy density materials, exhibit inherent instability due to quantum tunneling effects. This instability remains even near the absolute zero, and therefore they can be deemed as unsynthesizable. We propose substituents that could potentially stabilize pentazine, especially dimethylamine.

Many diamond properties are defined by substitutional defects (i. e., a carbon atom replaced by another element), which may involve the formation of structural isomers that can interconvert. Herein, we analysed by computational means the structure, thermodynamics, and kinetics of substitutional nitrogen, boron, and oxygen from small diamondoids up to the diamond bulk, focusing on the possibility of heavy atom quantum tunnelling rearrangement between the isomers. The large range of threshold energies and bond lengths lead to a variety of intriguing behaviours, including cage size dependent thermally activated tunnelling of nitrogen, and quantum delocalization of boron. In addition, we predict that applying an external electric field makes it possible to control the rearrangement thermodynamics and kinetics through tunnelling, which lets us hypothesize that these systems can potentially be used as atomic memory devices., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Sensor arrays use pattern recognition for the identification and quantification of analytes. In the presented work, a gold nanoparticle (GNP) based optical sensor array was employed to classify and quantify seven toxic metals (arsenic, barium, cadmium, cerium, chromium, lead, and mercury). The sensor array receptors were GNPs functionalized by mercaptoundecanoic acid, 2-mercaptoethanesulfonate, and a 1:1 mixture of the two ligands. The mixed-ligand particle responds to the same analytes as the mono-ligand particles but in a distinctive way. This behavior demonstrates the high potential of mixed-ligand particles in the fabrication of sensor array receptors. The responses of the GNPs to different concentrations of the seven metal ions were analyzed, and a unique "classification trajectory" was produced for every metal. Samples of different metal concentrations were then measured and identified using the "classification trajectories". Once sample composition has been identified, a PLSR model, produced from the concatenated sensor array spectra of four calibration samples for each nanoparticle, was used to determine the metal concentration., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Isotopic composition analysis of natural and depleted uranium by inductively coupled plasma optical emission spectrometry (ICP-OES) requires the use of a high-resolution instrument due to the very slight isotopic shifts between the atomic emission spectra of the 238 U and 235 U isotopes. In this work, we show that conventional ICP-OES (without high-resolution optics) can be used for highly accurate uranium isotopic analysis, on par with the results obtained by ICP-MS. Such accurate measurements are achieved by applying a preparatory mathematical procedure termed the optimal sensitivity position (OSP) procedure. In the OSP procedure, a theoretical spectrum for 238 U is constructed and subtracted from the measured spectra of calibration solutions encompassing various isotopic ratios. The resultant spectra are used to locate the optimal measurement positions for both major uranium isotopes ( 238 U and 235 U) and the background measurement position. Herein, the optimal measurement positions are revealed to be located not at each isotope's peak maximum but at 424.427, 424.409, and 424.390 nm for 238 U, 235 U, and the background position, respectively. These locations remained stationary during the period of this work, implying that the use of a routine mathematical procedure is not required before every analysis. The OSP procedure offers a direct and highly accurate approach for determining the isotopic ratio of uranium in a relatively cheap and simple fashion. Furthermore, this work also demonstrates the possibility of greatly enhancing ICP-OES capabilities using mathematical analysis of spectra.

The uncertainty on XeF 6 geometry persisted for over five decades, with elusive multiple C 3v equivalent minima as an outcome of the Jahn-Teller effect. Herein we theoretically prove that XeF 6 shows a genuine fluorine quantum mechanical tunnelling rearrangement, rapidly "jumping" between isomers even close to 0 K. The isoelectronic anions IF 6 - and TeF 6 2- behave in the same way as XeF 6 , but with a lower and shorter energetical barrier they have a faster tunnelling rate. A complete isotopic analysis revealed a large k( 18 F)/k( 19 F) kinetic isotope effect. We speculate that it would be possible to experimentally observe the tunnel effect in XeF 6 by means of cryogenic NMR or IR.

The degenerate rearrangement on Jahn-Teller distorted metal complexes is a promising reaction for the observation of significant heavy atom quantum mechanical tunnelling. Herein, a family of Cu(ii)-N 6 complexes are theoretically proven to exhibit rapid dynamical Jahn-Teller tunneling even close to the absolute zero. The manifestation of our predictions apparently appeared in solid state EPR experimental measurements on [Cu(en) 3 ]SO 4 more than 40 years ago, without the authors realizing that it was a quantum outcome., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This article presents a new method for the simpler and faster determination of tin in beverages using EDXRF. Absorption coefficients for aqueous calibration samples were calculated and shown to be nearly identical to those of the beverage samples, thus permitting the use of aqueous standard solutions for external calibration. Beverage samples could then be measured directly using the external calibration. Determination of tin using this method takes 4 min. The LOD and LOQ were 4 mg L -1 and 15 mg L -1 respectively, and the precision was 3.89%. Different canned beverages (cold coffee, various fruit juices) were measured and the results compared to the concentrations obtained using ICP-OES after digestion. The two methods showed good compatibility, thus establishing the newly developed method as a rapid, simple, and accurate method for the determination of tin in beverages., (Copyright © 2019 Elsevier B.V. All rights reserved.)