Bis(trifluoromethyl)methylene addition to vinyl-terminated SAMs: a gas-phase C-C bond-forming reaction on a surface

A Review on Reactions of Polycyclic Aromatic Hydrocarbons with the Most Abundant Atmospheric Chemical Fragments: Theoretical and Experimental Data

Aerosols are ubiquitous in the atmosphere and have strong effects on climate and public health due to the importance of reactions of polycyclic aromatic hydrocarbon (PAH) compounds in air. Over the last decade, study of the reactions of PAHs and their derivatives in the atmosphere has become a key topic to find an effective way to decrease the impact of this spontaneous reaction and so reduce air pollution. This article aims to pool the majority of research on the reactions of PAHs with atmospheric agents such as oxygen, hydrogen and ozone and compare the theoretical and experimental results. In examining theoretical research, the number of aromatic rings is very important in calculating the rate constants and determining the main pathway of the reaction. So, while there are weak theoretical data, several papers issued in this field have concurred with key experimental results. For reactants with more than six aromatic rings, small basis sets have good conformity with experimental outcomes. Due to the abundance of OH in the atmosphere, much research has been done to find the best reaction pathway and calculate the associated rate constants experimentally and theoretically. In future, the opportunity exists for new researchers to detect the main intermediates, most important pathways, rate constants and the products of reactions with more than six aromatic rings and to detect PAHs in a dense atmosphere. Product identification will help to reduce air pollution.

Two-Dimensional Zirconium-Based Metal-Organic Framework Nanosheet Composites Embedded with Au Nanoclusters: A Highly Sensitive Electrochemical Aptasensor toward Detecting Cocaine

Two-dimensional (2D) zirconium-based metal-organic framework nanosheets embedded with Au nanoclusters (denoted as 2D AuNCs@521-MOF) were prepared via a one-pot method under mild conditions. The optimized 2D AuNCs@521-MOF nanosheets not only possessed high specific surface area, physicochemical stability, and good electrochemical activity but also exhibited strong bioaffinity toward biomolecule-bearing phosphate groups. Consequently, a large amount of cocaine aptamer strands can be immobilized onto the substrate modified by 2D AuNCs@521-MOF nanosheet, further leading to the formation of a constructed biosensitive platform, which can be used to successfully detect cocaine through the specific binding interactions between cocaine and aptamer strands. The results demonstrated that the 2D AuNCs@521-MOF-based aptasensor had high sensitivity for detecting cocaine within the broad concentration range of 0.001-1.0 ng·mL^-1 and the low limit of detection of 1.29 pM (0.44 pg·mL^-1) and 2.22 pM (0.75 pg·mL^-1) as determined by electrochemical impedance spectroscopy and differential pulse voltammetry, respectively. As expected, with the advantages of high selectivity, repeatability, stability, and simple operation, this new strategy is believed to exhibit great potential for simple and convenient detection of cocaine.

Isothiourea-Mediated Organocatalytic Michael Addition-Lactonization on a Surface: Modification of SAMs on Silicon Oxide Substrates

Tailoring the functionality of self-assembled monolayers (SAMs) can be achieved either by depositing prefunctionalized molecules with the appropriate terminal groups or by chemical modification of an existing SAM in situ. The latter approach is particularly advantageous to allow for diversity of surface functionalization from a single SAM and if the incorporation of bulky groups is desired. In the present study an organocatalytic isothiourea-mediated Michael addition-lactonization process analogous to a previously reported study in solution is presented. An achiral isothiourea, 3,4-dihydro-2H-pyrimido[2,1-b]benzothiazole (DHPB), promotes the intermolecular Michael addition-lactonization of a trifluoromethylenone terminated SAM and a variety of arylacetic acids affording C(6)-trifluoromethyldihydropyranones tethered to the surface. X-ray photoelectron spectroscopy, atomic force microscopy, contact angle, and ellipsometry analysis were conducted to confirm the presence of the substituted dihydropyranone. A model study of this approach was also performed in solution to probe the reaction diastereoselectivity as it cannot be measured directly on the surface.