Photocatalytic H2 generation holds promise in the green production of alternative fuels and valuable chemicals. Seeking alternative, cost-effective, stable, and possibly reusable catalysts represents ...a timeless challenge for scientists working in the field. Herein, commercial RuO2 nanostructures were found to be a robust, versatile, and competitive catalyst in H2 photoproduction in several conditions. We employed it in a classic three-component system and compared its activities with those of the widely used platinum nanoparticle catalyst. We observed a hydrogen evolution rate of 0.137 mol h–1 g–1 and an apparent quantum efficiency (AQE) of 6.8% in water using EDTA as an electron donor. Moreover, the favorable employment of l-cysteine as the electron source opens possibilities precluded to other noble metal catalyst. The versatility of the system has also been demonstrated in organic media with impressive H2 production in acetonitrile. The robustness has been proved by the recovery of the catalyst by centrifugation and reusage alternatively in different media.
Photocatalytic H
generation holds promise in the green production of alternative fuels and valuable chemicals. Seeking alternative, cost-effective, stable, and possibly reusable catalysts represents ...a timeless challenge for scientists working in the field. Herein, commercial RuO
nanostructures were found to be a robust, versatile, and competitive catalyst in H
photoproduction in several conditions. We employed it in a classic three-component system and compared its activities with those of the widely used platinum nanoparticle catalyst. We observed a hydrogen evolution rate of 0.137 mol h
g
and an apparent quantum efficiency (AQE) of 6.8% in water using EDTA as an electron donor. Moreover, the favorable employment of l-cysteine as the electron source opens possibilities precluded to other noble metal catalyst. The versatility of the system has also been demonstrated in organic media with impressive H
production in acetonitrile. The robustness has been proved by the recovery of the catalyst by centrifugation and reusage alternatively in different media.
Herein we report that 4-pyridinylboronic acid (1) in the solid state self-assembles into tetrameric macrocycles via B–N bond formation. The tetramers are linked via O–H···O bonds resulting in a ...material that can be exfoliated via sonication to give thinner sheets as we demonstrate via Fourier transform infrared spectroscopy, transmission electron microscopy, selected area electron diffraction, and atomic force microscopy experiments. For comparison, the structure of the related compound 4-(pyridin-4-yl) phenylboronic acid (2) is also discussed.
We have designed a new multichromophoric system based on a tetra(phenylthio)pyrene core appended with four terpyridine units. The system behaves as a molecular antenna that collects light with the ...peripheral units and funnels the energy to the very highly luminescent core. The addition of metals ions to the investigated system can not only switch the direction of the intramolecular energy transfer, but also control the formation of three‐dimensional nanoscopic objects in a dual function.
Alternating one‐way: We report the synthesis, characterization, and photophysical behavior of a highly luminescent supramolecular antenna based on a tetra(thio)pyrene core appended with four phenylated terpyridine units (see figure). The coordination of metals ions can not only switch the direction of the intramolecular energy transfer (En.Tr.), but can also can control the formation of three‐dimensional nanoscopic objects in a dual function.
A new 3,4-ethylenedioxythiophene (EDOT) monomer derivatized with aminopropyl-triethoxysilane (APTES-EDOT) was prepared via a simple two step reaction in high yield. The new monomer can be firmly ...grafted to the fluorine–tin-oxide (FTO) conductive glass, where the irreversible electro-oxidation of surface bound APTES-EDOT, in the presence of unsubstituted EDOT monomers in solution, triggers the cationic polymerization of EDOT, resulting in the incorporation of PEDOT chains into APTES-EDOT. As a result, the modified PEDOT film (Si-PEDOT) is covalently bound to the FTO surface and easily withstands mechanical stresses that are critical for the adhesion of regular PEDOT. When tested with Co(III)/(II) redox shuttles, electrodeposited Si-PEDOT films showed decreased charge transfer and mass transport resistances with respect to both platinum and conventional PEDOT films, leading to enhanced relative efficiencies (≈10%) when employed as counter electrode in transparent dye sensitized solar cells.
We describe the preparation of poly(3-hexylthiophene-S,S-dioxide) nanoparticles using Rozen’s reagent, HOF·CH3CN, either on poly(3-hexylthiophene) (P3HT) or on preformed P3HT nanoparticles ...(P3HT-NPs). In the latter case, core–shell nanoparticles (P3HT@PTDO-NPs) are formed, as confirmed by X-ray photoelectron spectroscopy measurements, indicating the presence of oxygen on the outer shell. The different preparation modalities lead to a fine-tuning of the chemical–physical properties of the nanoparticles. We show that absorption and photoluminescence features, electrochemical properties, size, and stability of colloidal solutions can be finely modulated by controlling the amount of oxygen present. Atomic force microscopy measurements on the nanoparticles obtained by a nanoprecipitation method from preoxidized P3HT (PTDO-NPs) display spherical morphology and dimensions down to 5 nm. Finally, Kelvin probe measurements show that the coexistence of p- and n-type charge carriers in all types of oxygenated nanoparticles makes them capable of generating and separating charge under illumination. Furthermore, in core–shell nanoparticles, the nanosegregation of the two materials, in different regions of the nanoparticles, allows a more efficient charge separation.
Monolayer sheets have gained attention due to the unique properties derived from their two-dimensional structure. One of the key challenges in sheet modification/synthesis is to exchange integral ...parts while keeping them intact. We describe site-to-site transmetalation of Zn2+ in the netpoints of cm2-sized, metal–organic sheets by Fe2+, Co2+, and Pb2+. This novel transformation was done both randomly and at predetermined patterns defined by photolithography to create monolayer sheets composed of different netpoints. All transmetalated sheets are mechanically strong enough to be spanned over 20 × 20 μm2 sized holes. Density functional theory calculations provide both a model for the molecular structure of an Fe2+-based sheet and first insights into how transmetalation proceeds. Such transmetalated sheets with random and patterned netpoints can be considered as two-dimensional analogues of linear copolymers. Their nanoscale synthesis presents an advance in monolayer/polymer chemistry with applications in fields such as surface coating, molecular electronics, device fabrication, imaging, and sensing.
We have studied the adducts formed by eosin (E) with a fourth generation dendrimer (D) that comprises 30 tertiary amine units in the interior and 32 naphthyl and 32 trans azobenzene units in the ...periphery. We have found that: (i) the all trans dendrimer D(32t) can be converted by irradiation with 365 nm light (Φ=0.12) into species containing, as an average, 4 trans and 28 cis azobenzene units, D(4t28c), that at 313 K undergoes a D(4t28c) → D(32t) thermal back reaction (k = 7.0 × 10-5 s-1); (ii) D(32t) and D(4t28c) extract 8 and, respectively, 6 eosin molecules from water at pH 7, yielding the species D(32t)⊃8E and D(4t28c)⊃6E; (iii) eosin uptake is significantly faster for D(32t) than for D(4t28c); (iv) irradiation at 365 nm of the D(32t)⊃8E species at 298 K leads to the release of two eosin molecules with formation of a photostable D(15t17c)⊃6E species (Φ = 0.15) that is also obtained from the back thermal reaction of D(4t28c)⊃6E at 313 K (k = 2.7 × 10-5 s-1); (v) thermal release of E from D(32t)⊃6E is much faster than from D(4t28c)⊃6E; and (vi) excitation of E in the adducts sensitizes the cis → trans (but not the trans → cis) isomerization. The results obtained show that the isomerization of the 32 peripheral azobenzene units controls to some extent the hosting capacity of the dendrimer and, viceversa, eosin molecules hosted in the dendrimer affect the isomerization process of its azobenzene units.
Carbon‐heteroatom cross‐coupling reactions are significant for numerous industrial chemical processes, in particular for the synthesis of pharmaceuticals, agrochemicals, and biologically active ...compounds. Photocatalyst/transition metal dual catalytic systems pave a new avenue for organic cross‐coupling reactions. Specifically, the use of semiconductor nanoparticles as heterogeneous light sensitizers is highly beneficial for industrial‐scale applications owing to their low‐cost production, tunable photophysical properties, facile separation, high photostability, and recyclability. Here, CdSe@CdS nanorod photocatalysts are combined with a Ni complex catalyst for the promotion of selective light‐induced C−O cross‐coupling reactions between aryl halides and alkyl carboxylic acids. This efficient dual photocatalytic system displays a high yield (∼96 %), with an impressive turnover number (TON) of over 3×106, and within a relatively short reaction time as a result of high turnover frequency (TOF) of ∼56 s−1. In addition, the nanorod photocatalysts harness light with improved solar to product efficiency compared to alternative systems, signaling towards potential solar‐powered chemistry. A reaction mechanism involving energy transfer from the nanorods to the Ni complex is proposed and discussed, along with specific benefits of the seeded rod morphology.
Photocatalytic synthesis: A unique dual photocatalytic system utilizes colloidal nanorods as heterogeneous photosensitizers, in combination with a nickel complex catalyst, for the promotion of selective and efficient light induced carbon‐heteroatom cross‐coupling reactions. A Dexter energy transfer reaction mechanism is proposed and discussed. The system displays superior catalytic performance and additional benefits towards industrial scale applications.
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