An official website of the United States government
Abstract Electrochemical approaches to form C(sp2)−C(sp3) bonds have focused on coupling C(sp3) electrophiles that form stabilized carbon‐centered radicals upon reduction or oxidation. Whereas alkyl bromides are desirable C(sp3) coupling partners owing to their availability and cost‐effectiveness, their tendency to undergo radical‐radical homocoupling makes them challenging substrates for electroreductive cross‐coupling. Herein, we disclose a metal‐free regioselective cross‐coupling of 1,4‐dicyanobenzene, a useful precursor to aromatic nitriles, and alkyl bromides. Alkyl bromide reduction is mediated directly by 1,4‐dicyanobenzene radical anions, leading to negligible homocoupling and high cross‐selectivity to form 1,4‐alkyl cyanobenzenes. The cross‐coupling scheme is compatible with oxidatively sensitive and acidic functional groups such as amines and alcohols, which have proven difficult to incorporate in alternative electrochemical approaches using carboxylic acids as C(sp3) precursors.
more »
« less
Graphene Defects in Saccharide Carbon Dots Govern Electrochemical Sensitivity
Abstract Galactose (Gal), lactose (Lac), and glucose (Glu) derived carbon dots (CDs) were evaluated for their utility as electrochemical sensing composites using acetaminophen (APAP) as a probe molecule. The goal of this work is to ascertain the role of graphene defects on electrochemical activity. Higher sp2‐to‐sp3hybridized carbon ratios (in parentheses) in the CDs correlated with higher sensitivity in the order according to measured Raman IG/IDintensities: GluCDs (6.53)−3APAP range at pH=7.0 was achieved, suitable for practical APAP toxicity monitoring. Defect density within the GalCDs provided the highest sensitivity.
more »
« less
- Award ID(s):
- 2041413
- PAR ID:
- 10448019
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Electroanalysis
- Volume:
- 33
- Issue:
- 11
- ISSN:
- 1040-0397
- Page Range / eLocation ID:
- p. 2261-2266
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The effect of rare earth (RE) single atoms on photocatalytic activity is very complex due to its special electronic configuration, which leads to few reports on the RE single atoms. Here, Dy3+single atom composite photocatalysts are successfully constructed based on both the special role of Dy3+and the special advantages of CdS/g‐C3N4heterojunction in the field of photocatalysis. The results show that an efficient way of electron transfer is provided to promote charge separation, and the dual functions of CO2molecular activation of rare‐earth single atom and 4flevels as electron transport bridge are fully exploited. It is exciting that under visible‐light irradiation, the catalytic performance of CdS:Dy3+/g‐C3N4is≈6.9 times higher than that of pure g‐C3N4. The catalytic performance of CdS:Dy3+and CdS:Dy3+/g‐C3N4are≈7 and≈13.7 times higher than those of pure CdS, respectively. Besides, not all RE ions are suitable for charge transfer bridges, which is not only related to the 4flevels of RE ions but also related to the bandgap structure of CdS and g‐C3N4. The pattern of combining single‐atom catalysis and heterojunction opens up new methods for enhancing photocatalytic activity.more » « less
-
Nanoparticle organic hybrid materials (NOHMs) have been proposed as excellent electrolytes for combined CO2capture and electrochemical conversion due to their conductive nature and chemical tunability. However, CO2capture behavior and transport properties of these electrolytes after CO2capture have not yet been studied. Here, we use a variety of nuclear magnetic resonance (NMR) techniques to explore the carbon speciation and transport properties of branched polyethylenimine (PEI) and PEI-grafted silica nanoparticles (denoted as NOHM-I-PEI) after CO2capture. Quantitative13C NMR spectra collected at variable temperatures reveal that absorbed CO2exists as carbamates (RHNCOO−or RR′NCOO−) and carbonate/bicarbonate (CO32−/HCO3−). The transport properties of PEI and NOHM-I-PEI studied using1H pulsed-field-gradient NMR, combined with molecular dynamics simulations, demonstrate that coulombic interactions between negatively and positively charged chains dominate in PEI, while the self-diffusion in NOHM-I-PEI is dominated by silica nanoparticles. These results provide strategies for selecting adsorbed forms of carbon for electrochemical reduction.more » « less
-
Molecular Ag(II) complexes are superoxidizing photoredox catalysts capable of generating radicals from redox-reticent substrates. In this work, we exploited the electrophilicity of Ag(II) centers in [Ag(bpy)2(TFA)][OTf] and Ag(bpy)(TFA)2(bpy, 2,2′-bipyridine; OTf, CF3SO3–) complexes to activate trifluoroacetate (TFA) by visible light–induced homolysis. The resulting trifluoromethyl radicals may react with a variety of arenes to forge C(sp2)–CF3bonds. This methodology is general and extends to other perfluoroalkyl carboxylates of higher chain length (RFCO2–; RF, CF2CF3or CF2CF2CF3). The photoredox reaction may be rendered electrophotocatalytic by regenerating the Ag(II) complexes electrochemically during irradiation. Electrophotocatalytic perfluoroalkylation of arenes at turnover numbers exceeding 20 was accomplished by photoexciting the Ag(II)–TFA ligand-to-metal charge transfer (LMCT) state, followed by electrochemical reoxidation of the Ag(I) photoproduct back to the Ag(II) photoreactant.more » « less
-
Abstract Multifunctional nanozymes can benefit biochemical analysis via expanding sensing modes and enhancing analytical performance, but designing multifunctional nanozymes to realize the desired sensing of targets is challenging. In this work, single‐atomic iron doped carbon dots (SA Fe‐CDs) are designed and synthesized via a facile in situ pyrolysis process. The small‐sized CDs not only maintain their tunable fluorescence, but also serve as a support for loading dispersed active sites. Monoatomic Fe offers SA Fe‐CDs exceptional oxidase‐mimetic activity to catalyze 3,3′,5,5′‐tetramethylbenzidine (TMB) oxidation with fast response (Vmax = 10.4 nM s‐1) and strong affinity (Km = 168 µM). Meanwhile, their photoluminescence is quenched by the oxidation product of TMB due to inner filter effect. Phosphate ions (Pi) can suppress the oxidase‐mimicking activity and restore the photoluminescence of SA Fe‐CDs by interacting with Fe active sites. Based on this principle, a dual‐mode colorimetric and fluorescence assay of Pi with high sensitivity, selectivity, and rapid response is established. This work paves a path to develop multifunctional enzyme‐like catalysts, and offers a simple but efficient dual‐mode method for phosphate monitoring, which will inspire the exploration of multi‐mode sensing strategies based on nanozyme catalysis.more » « less
