In this study, we design a FRET system consisting of gold nanorod (AuNR) and quantum dots (QDs) for turn-on fluorescent sensing of 2,4,6-trinitrotoluene (TNT) in near-infrared region. The amine-terminated AuNR and carboxyl-terminated QDs first form a compact hybrid assembly through amine-carboxyl attractive interaction, which leads to a high-efficiency (>92%) FRET from QDs to AuNRs and an almost complete emission quenching. Next, added TNT molecules break the preformed assembly because they can replace the QDs around AuNRs, based on the specific reaction of forming Meisenheimer complexes between TNT and primary amines. Thus, the FRET is switched off, and a more than 10 times fluorescent enhancement is obtained. The fluorescence turn-on is immediate, and the limit of detection for TNT is as low as 0.1 nM. Importantly, TNT can be well distinguished from its analogues due to their electron deficiency difference. The developed method is successfully applied to TNT sensing in real environmental samples.

Remote difunctionalization of unactivated alkenes is challenging but a highly attractive tactic to install two functional groups across long distances. Reported herein is the first remote difunctionalization of alkenes with CO2. This visible‐light photoredox catalysis strategy provides a facile method to synthesize a series of carboxylic acids bearing valuable fluorine‐ or phosphorus‐containing functional groups. Moreover, this versatile protocol shows mild reaction conditions, broad substrate scope, and good functional‐group tolerance. Based on DFT calculations, a radical adds to an unactivated alkene to smoothly form a new carbon radical, followed by a 1,5‐hydrogen atom‐transfer process, the rate‐limiting step, generating a more stable benzylic radical. The reduction of the benzylic radicals by an IrII species generates the corresponding benzylic carbanions as the key intermediates, which further undergo nucleophilic attack with CO2 to generate carboxylates.

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Fluorescence sensing of enantiomers is a much needed yet very challenging task due to nearly identical chemical and physical properties of the chiral isomers also known as chiral equivalence. In this study, we propose a novel strategy for fluorescence sensing of enantiomers using chiral nanoparticles and their ability to form dynamic assemblies. Fluorescence resonance energy transfer (FRET) in nanoscale assemblies consisting of either L-cysteine- or D-cysteine-modified quantum dots (QDs) and gold nanorods (GNRs) was found to be strongly dependent on traces of cysteine. This occurs due to high sensitivity of dynamic assemblies to the weak internanoparticle interactions that can exponentially increase energy transfer efficiencies from QDs to GNRs. Comprehensive analysis of the fluorescence responses in the two types of chiral nanoscale assemblies enables accurate determination of both concentration and enantiomeric composition of the analyte, i.e., cysteine. The described method can quantify the composition of a chiral sample, even the content of one enantiomer is as low as 10% in the mixture. Exceptional selectivity in respect to D/L-cysteine in comparison to analogous small molecules was observed. Versatility of nanoparticle-nanorod assemblies and tunability of intermolecular interactions in them open the road to adaptation of this sensing platform to other chiral analytes.

Reported is the first oxy-trifluoromethylation of allylamines with carbon dioxide (CO2 ) using copper catalysis, thus leading to important CF3 -containing 2-oxazolidones. It is also the first time CO2 , a nontoxic and easily available greenhouse gas, has been used to tune the difunctionalization of alkenes from amino- to oxy-trifluoromethylation. Of particular note, this multicomponent reaction is highly chemo-, regio-, and diastereoselective under redox-neutral and mild reaction conditions. Moreover, these reactions feature good functional-group tolerance, broad substrate scope, easy scalability and facile product diversification. The important products could also be formed with either spirocycles or two adjacent tetrasubstituted carbon centers.