Phosphorene as a Template Material for Physisorption of DNA/RNA Nucleobases and Resembling of Base Pairs: A Cluster DFT Study and Comparisons with Graphene

A quantum chemistry study was performed to study the interaction of single deoxyribonucleic/ribonucleic acid (DNA/RNA) nucleobases and hydrogen-bonded base pairs onto a phosphorene nanosheet. Adenine (A), cytosine (C), guanine (G), thymine (T), and uracyl (U) were considered as the adsorbates that are physisorbed onto phosphorene in stacking patterns, reaching adsorption energies of 0.64–0.94 eV and sorting the physisorption stability as G > C > A > T > U. The structure and aromaticity of all the nucleobases are not affected upon complexation. Likewise, the hydrogen-bonded base-pairs (CG, AT, and AU) are adsorbed in the armchair plane of phosphorene with high adsorption energies of 1.28–1.44 eV and sorting the physisorption stability as CG > AT > AU. The hydrogen bond energies of the base pairs are slightly affected by binding on phosphorene, retaining its stability at room temperature (300 K). Furthermore, comparison analyses showed that phosphorene is better suited for physisorption of nucleobases and base pairs than graphene, improving the stability in up to 27%. This improvement is based on the interplay between enhanced dispersion and electrostatic interactions. Otherwise, all the nucleobases behave as mild <i>n</i>-dopants, introducing up to ∼0.1 <i>e</i>/molecule in phosphorene. The charge doping and bandgap changes suggest that the phosphorene conductance could be sensitive to the physisorption of nucleobases and base pairs. Finally, the new insights from this work shed light onto the physisorption phenomena of biomolecules occurring at phosphorene interfaces, indicating that phosphorene emerges as a promising template for self-assembly of nucleobases in nanobiological devices

Binding of Trivalent Arsenic onto the Tetrahedral Au₂₀ and Au₁₉Pt Clusters: Implications in Adsorption and Sensing

The interaction of arsenic­(III) onto the tetrahedral Au₂₀ cluster was studied computationally to get insights into the interaction of arsenic traces (presented in polluted waters) onto embedded electrodes with gold nanostructures. Pollutant interactions onto the vertex, edge, or inner gold atoms of Au₂₀ were observed to have a covalent character by forming metal–arsenic or metal–oxygen bonding, with adsorption energies ranging from 0.5 to 0.8 eV, even with a stable physisorption; however, in aqueous media, the Au–vertex–pollutant interaction was found to be disadvantageous. The substituent effect of a platinum atom onto the Au₂₀ cluster was evaluated to get insights into the changes in the adsorption and electronic properties of the adsorbent–adsorbate systems due to chemical doping. It was found that the dopant atom increases both the metal–pollutant adsorption energy and stability onto the support in a water media for all interaction modes; adsorption energies were found to be in a range of 0.6 to 1.8 eV. All interactions were determined to be accompanied by electron transfer as well as changes in the local reactivity that determine the amount of transferred charge and a decrease in the HOMO–LUMO energy gap with respect to the isolated substrate

Supramolecular Reversible On–Off Switch for Singlet Oxygen Using Cucurbit[<i>n</i>]uril Inclusion Complexes

A novel strategy to control the generation of singlet oxygen by a photosensitizer using cucurbit­[<i>n</i>]­urils inclusion complexes is shown herein, and the strategy has great potential for therapeutic applications. We show the basic requirements of the photosensitizer complexes in order to develop an <i>on</i>–<i>off</i> switch for singlet oxygen that is reversible using competitive binding. The supramolecular strategy proposed in this paper avoids complex synthetic schemes in order to activate or deactivate the photosensitizer as previous work has shown and supports the use of biocompatible materials. Mechanistic insights into the control over the generation of singlet oxygen are provided, which strongly emphasize the key role of the cucurbit­[<i>n</i>]­uril macrocycles in the stabilization or deactivation of the triplet excited state

Reaction Electronic Flux Perspective on the Mechanism of the Zimmerman Di-π-methane Rearrangement

The reaction electronic flux (REF) offers a powerful tool in the analysis of reaction mechanisms. Noteworthy, the relationship between aromaticity and REF can eventually reveal subtle electronic events associated with reactivity in aromatic systems. In this work, this relationship was studied for the triplet Zimmerman di-π-methane rearrangement. The aromaticity loss and gain taking place during the reaction is well acquainted by the REF, thus shedding light on the electronic nature of reactions involving dibenzobarrelenes