The direct exploitation of 'electrons' as reagents in synthetic organic transformations is on the verge of a renaissance by virtue of its greenness, sustainability, atom economy, step economy and ...inherent safety. Achieving stereocontrol in such organic electrochemical reactions remains a major synthetic challenge and hence demands great expertise. This review provides a comprehensive discussion of the details of stereoselective organic electrochemical reactions along with the synthetic accomplishments achieved with these methods.
► The ecofriendly deposition of Ga-doped zinc oxide. ► Influence of Ga doping onto physicochemical properties in aqueous media. ► Electron–phonon coupling by Raman. ► Chemical bonding structure and ...valence band analysis by XPS.
Ga-doped ZnO thin films are synthesized by chemical spray pyrolysis onto corning glass substrates in aqueous media. The influence of gallium doping on to the photoelectrochemical, structural, Raman, XPS, morphological, optical, electrical, photoluminescence and thermal properties have been investigated in order to achieve good quality films. X-ray diffraction study depicts the films are polycrystalline and fit well with hexagonal (wurtzite) crystal structure with strong orientations along the (002) and (101) planes. Presence of E2high mode in Raman spectra indicates that the gallium doping does not change the wurtzite structure. The coupling strength between electron and LO phonon has experimentally estimated. In order to understand the chemical bonding structure and electronic states of the Ga-doped ZnO thin films XPS analysis have been studied. SEM images shows the films are adherent, compact, densely packed with hexagonal flakes and spherical grains. Optical transmittance and reflectance measurements have been carried out. Room temperature PL spectra depict violet, blue and green emission in deposited films. The specific heat and thermal conductivity study shows the phonon conduction behavior is dominant in these polycrystalline films.
The development of an electrochemical cobalt catalyzed C-Cl bond activation at room temperature for the nucleophilic addition of aryl and vinyl chlorides to α-ketoamides is described. The overall ...method operates through an electrochemically induced low valent cobalt catalyst that oxidatively adds to aryl or vinyl chlorides affording medicinally important 3-hydroxy oxindole and 3-hydroxypyrrolidinone scaffolds. The development of an enantioselective version using a chiral pyrox ligand is also demonstrated.
Indium doped zinc oxide (IZO) thin films are grown onto Corning glass substrates using the spray pyrolysis technique. The effect of doping concentration on the structural, electrical and optical ...properties of IZO thin films is studied. X-ray diffraction studies show a change in preferential orientation from the (0 0 2) to the (1 0 1) crystal planes with increase in indium doping concentration. Scanning electron microscopy studies show polycrystalline morphology of the films. Based on the Hall-effect measurements and analysis, impurity scattering is found to be the dominant mechanism determining the diminished mobility in ZnO thin films having higher indium concentration. The addition of indium also induces a drastic decrease in the electrical resistivity of films; the lowest resistivity (4.03 X 10-5 Omega cm) being observed for the film deposited with 3 at% indium doping. The effect of annealing on the film properties has been reported. Films deposited with 3 at% In concentration have relatively low resistivity with 90% transmittance at 550 nm and the highest value of figure of merit 7.9 X 10-2 Omega-1.
We report the temperature-dependent photoluminescence (PL) properties of polymeric graphite-like carbon nitride (g-C3N4) and a methodology for the determination of quantum efficiency along with the ...activation energy. The PL is shown to originate from three different pathways of transitions: σ*–LP, π*–LP, and π*−π, respectively. The overall activation energy is found to be ∼73.58 meV which is much lower than the exciton binding energy reported theoretically but ideal for highly sensitive wide-range temperature sensing. The quantum yield derived from the PL data is 23.3%, whereas the absolute quantum yield is 5.3%. We propose that the temperature-dependent PL can be exploited for the evaluation of the temperature dependency of quantum yield as well as for temperature sensing. Our analysis further indicates that g-C3N4 is well-suited for wide-range temperature sensing.
In recent years, enantioselective cooperative catalytic reactions, wherein two catalysts work simultaneously to form products which cannot be obtained by the use of a single catalyst alone, have ...attracted considerable attention. This review focuses on this emerging field, with particular emphasis on mechanistic aspects, which will help readers to understand the role of each catalyst.
This review focuses on enantioselective cooperative catalytic reactions, wherein two catalysts work simultaneously to form products which cannot be obtained by the use of a single catalyst alone, which have attracted considerable attention in recent years.
Rational design of efficient and durable bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is critical for rechargeable metal–air batteries. Here, we ...developed a facile strategy for fabricating three-dimensional phosphorus and sulfur codoped carbon nitride sponges sandwiched with carbon nanocrystals (P,S-CNS). These materials exhibited high surface area and superior ORR and OER bifunctional catalytic activities than those of Pt/C and RuO2, respectively, concerning its limiting current density and onset potential. Further, we tested the suitability and durability of P,S-CNS as the oxygen cathode for primary and rechargeable Zn–air batteries. The resulting primary Zn–air battery exhibited a high open-circuit voltage of 1.51 V, a high discharge peak power density of 198 mW cm–2, a specific capacity of 830 mA h g–1, and better durability for 210 h after mechanical recharging. An extraordinary small charge–discharge voltage polarization (∼0.80 V at 25 mA cm–2), superior reversibility, and stability exceeding prolonged charge–discharge cycles have been attained in rechargeable Zn–air batteries with a three-electrode system. The origin of the electrocatalytic activity of P,S-CNS was elucidated by density functional theory analysis for both oxygen reactions. This work stimulates an innovative prospect for the enrichment of rechargeable Zn–air battery viable for commercial applications such as armamentaria, smart electronics, and electric vehicles.
Isoprenoids, often called terpenoids, are the most abundant and highly diverse family of natural organic compounds. In plants, they play a distinct role in the form of photosynthetic pigments, ...hormones, electron carrier, structural components of membrane, and defence. Many isoprenoids have useful applications in the pharmaceutical, nutraceutical, and chemical industries. They are synthesized by various isoprenoid synthase enzymes by several consecutive steps. Recent advancement in metabolic engineering and synthetic biology has enabled the production of these isoprenoids in the heterologous host systems like
Escherichia coli
and
Saccharomyces cerevisiae.
Both heterologous systems have been engineered for large-scale production of value-added isoprenoids. This review article will provide the detailed description of various approaches used for engineering of methyl-
d
-erythritol-4-phosphate (MEP) and mevalonate (MVA) pathway for synthesizing isoprene units (C
5
) and ultimate production of diverse isoprenoids. The review particularly highlighted the efforts taken for the production of C
5
–C
20
isoprenoids by metabolic engineering techniques in
E. coli
and
S. cerevisiae
over a decade. The challenges and strategies are also discussed in detail for scale-up and engineering of isoprenoids in the heterologous host systems.
Key points
• Isoprenoids are beneficial and valuable natural products.
• E. coli and S. cerevisiae are the promising host for isoprenoid biosynthesis.
• Emerging techniques in synthetic biology enabled the improved production.
• Need to expand the catalogue and scale-up of un-engineered isoprenoids.
Graphical abstract
Metabolic engineering and synthetic biology for isoprenoid production in
Escherichia coli
and
Saccharomyces cerevisiae
Electrocatalytic hydrogen evolution using non-precious metals or metal-free catalysts is critically necessary because platinum-based electrocatalysts are greatly limited in scalable commercialization ...of hydrogen generation due to their high cost. Here, we report the facile synthesis of metal-free hybrid catalysts, in which graphitic carbon nitride (g-C sub(3)N sub(4)) is coupled with nanoporous graphene doped by S and Se. The S and Se co-doped hybrid catalyst (g-C sub(3)N sub(4)S-Se-p Gr) reveals superior electrocatalytic performances, including an exchange current density of 6.27 10 super(-6) A cm super(-2), an on-set potential of 0.092 V, a Tafel slope of 86 mV dec super(-1), an adsorption free energy of -0.13 eV, and long-term stability comparable to those of commercial Pt/C catalysts. Volcano plots showing the hydrogen evolution activity versusadsorption free energy are also compatible with those of the conventional metal catalysts. Our strategy has the potential to allow a new paradigm for the development of high-performance metal-free electrocatalysts for energy conversion devices.
We report a trouble-free chemical synthesis of copper oxide (CuO) nanoflowers on flexible copper foil (Cu) and their use as electrodes for supercapacitors. Various characterization techniques, such ...as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and Brunauer-Emmett-Teller (BET) analysis, have been used to characterize CuO nanostructure. Supercapacitive properties show that CuO electrodes exhibit a high specific capacitance of about 498 F g
−1
at 5 mV s
−1
, with a high energy density of 26 W h kg
−1
in KOH electrolyte. Moreover, impedance analysis showed lower ESR value, high power performance, and an excellent rate as well as frequency response for the CuO electrodes. The excellent electrochemical properties of the CuO electrodes indicate that they have many potential applications in high-performance supercapacitors.
We present a novel route for the synthesis of CuO thin films. The nano-flower like nanostructures provide high surface area, and the CuO shows excellent supercapacitive properties.
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