Graphitic carbon
nitride materials have attracted significant interest
in recent years and found applications in diverse light-to-energy
conversions such as artificial photosynthesis, CO2 reduction,
or degradation of organic pollutants. However, their utilization in
synthetic photocatalysis, especially in the direct functionalization
of C(sp3)–H bonds, remains underexplored. Herein,
we report mesoporous graphitic carbon nitride (mpg-CN) as a heterogeneous
organic semiconductor photocatalyst for direct arylation of C(sp3)–H bonds in combination with nickel catalysis. Our
protocol has a broad synthetic scope (>70 examples including late-stage
functionalization of drugs and agrochemicals), is operationally simple,
and shows high chemo- and regioselectivities. Facile separation and
recycling of the mpg-CN catalyst in combination with its low preparation
cost, innate photochemical stability, and low toxicity are beneficial
features overcoming typical shortcomings of homogeneous photocatalysis.
Detailed mechanistic investigations and kinetic studies indicate that
an unprecedented energy-transfer process (EnT) from the organic semiconductor
to the nickel complex is operating.
Synthetic photoelectrochemistry (PEC) is receiving increasing attention as a new frontier for the generation and handling of reactive intermediates. PEC permits selective single‐electron transfer (SET) reactions in a much greener way and broadens the redox window of possible transformations. Herein, the most recent contributions are reviewed, demonstrating exciting new opportunities, namely, the combination of PEC with other reactivity paradigms (hydrogen‐atom transfer, radical polar crossover, energy transfer sensitization), scalability up to multigram scale, novel selectivities in SET super‐oxidations/reductions and the importance of precomplexation to temporally enable excited radical ion catalysis.
The total and ionization cross sections for electron scattering by benzene, halobenzenes, toluene, aniline, and phenol are reported over a wide energy domain. The multi-scattering centre spherical complex optical potential method has been employed to find the total elastic and inelastic cross sections. The total ionization cross section is estimated from total inelastic cross section using the complex scattering potential-ionization contribution method. In the present article, the first theoretical calculations for electron impact total and ionization cross section have been performed for most of the targets having numerous practical applications. A reasonable agreement is obtained compared to existing experimental observations for all the targets reported here, especially for the total cross section.
Molecular photoelectrochemistry , allowing access to a broader window of single electron transfer chemistry in a greener way, is a rapidly expanding toolbox for synthesis and selective functionalizations of complex molecules. In their Review (e202107811), Joshua P. Barham and co‐workers capture exciting synthetic opportunities, key mechanistic insights and evolving batch and flow reactor platforms allowing screening and scalability of reactions.
Silicon solar cells are the most widely deployed modules owing to their low-cost manufacture, large market, and suitable efficiencies for residential and commercial use. Methods to increase their solar energy collection must be easily integrated into module fabrication. We perform a theoretical and experimental study on the light collection properties of an encapsulant that incorporates a periodic array of air prisms, which overlay the metallic front contacts of silicon solar cells. We show that the light collection efficiency induced by the encapsulant depends on both the shape of the prisms and angle of incidence of incoming light. We elucidate the changes in collection efficiency in terms of the ray paths and reflection mechanisms in the encapsulant. We fabricated the encapsulant from a commercial silicone and studied the change in the external quantum efficiency (EQE) on an encapsulated, standard silicon solar cell. We observe efficiency enhancements, as compared to a uniform encapsulant, over the visible to near infrared region for a range of incident angles. This work demonstrates exactly how a periodic air prism architecture increases light collection, and how it may be designed to maximize light collection over the widest range of incident angles.
A photocatalyst-free
and mild visible light photochemical procedure
for C(sp3)–H arylation of amides is described. The
reaction proceeds via an electron donor–acceptor (EDA) complex
between an electron-rich arene substrate and electron-poor persulfate
oxidant. C(sp3)–H arylation of the amide occurs
selectively with the most electron-rich arene of the substrate. Mechanistic
studies corroborate the reaction taking place in a solvent cage holding
components in a close proximity.
5The present article reports calculation of electron impact total ionisation cross sections for C 3 to C 6 ethanoates for the energy range from ionisation threshold of the target to 5000 eV. The spherical complex optical potential and complex scattering potential ionisation contribution methods are employed to calculate the cross sections. The results presented here show consistent variation with previous measurements and theoretical values, wherever available. The dependence of isomeric effect on the ionisation cross section is also studied. Plot for the peak of ionisation cross section against the square root of the ratio of polarisability to
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