Efficient CO Oxidation by 50-Facet Cu₂O Nanocrystals Coated with CuO Nanoparticles

As carbon monoxide oxidation is widely used for various chemical processes (such as methanol synthesis and water-gas shift reactions H₂O + CO ⇄ CO₂ + H₂) as well as in industry, it is essential to develop highly energy efficient, inexpensive, and eco-friendly catalysts for CO oxidation. Here we report green synthesis of ∼10 nm sized CuO nanoparticles (NPs) aggregated on ∼400 nm sized 50-facet Cu₂O polyhedral nanocrystals. This CuO-NPs/50-facet Cu₂O shows remarkable CO oxidation reactivity with very high specific CO oxidation activity (4.5 μmol_CO m^–2 s^–1 at 130 °C) and near-complete 99.5% CO conversion efficiency at ∼175 °C. This outstanding catalytic performance by CuO NPs over the pristine multifaceted Cu₂O nanocrystals is attributed to the surface oxygen defects present in CuO NPs which facilitate binding of CO and O₂ on their surfaces. This new material opens up new possibilities of replacing the usage of expensive CO oxidation materials

Accelerated Bone Regeneration by Two-Photon Photoactivated Carbon Nitride Nanosheets

Human bone marrow-derived mesenchymal stem cells (hBMSCs) present promising opportunities for therapeutic medicine. Carbon derivatives showed only marginal enhancement in stem cell differentiation toward bone formation. Here we report that red-light absorbing carbon nitride (C₃N₄) sheets lead to remarkable proliferation and osteogenic differentiation by runt-related transcription factor 2 (Runx2) activation, a key transcription factor associated with osteoblast differentiation. Accordingly, highly effective hBMSCs-driven mice bone regeneration under red light is achieved (91% recovery after 4 weeks compared to 36% recovery in the standard control group in phosphate-buffered saline without red light). This fast bone regeneration is attributed to the deep penetration strength of red light into cellular membranes <i>via</i> tissue and the resulting efficient cell stimulation by enhanced photocurrent upon two-photon excitation of C₃N₄ sheets near cells. Given that the photoinduced charge transfer can increase cytosolic Ca²⁺ accumulation, this increase would promote nucleotide synthesis and cellular proliferation/differentiation. The cell stimulation enhances hBMSC differentiation toward bone formation, demonstrating the therapeutic potential of near-infrared two-photon absorption of C₃N₄ sheets in bone regeneration and fracture healing

Halogen−π Interactions between Benzene and X₂/CX₄ (X = Cl, Br): Assessment of Various Density Functionals with Respect to CCSD(T)

Various types of interactions between halogen (X) and π moiety (X−π interaction) including halogen bonding play important roles in forming the structures of biological, supramolecular, and nanomaterial systems containing halogens and aromatic rings. Furthermore, halogen molecules such as X₂ and CX₄ (X = Cl/Br) can be intercalated in graphite and bilayer graphene for doping and graphene functionalization/modification. Due to the X−π interactions, though recently highly studied, their structures are still hardly predictable. Here, using the coupled-cluster with single, double, and noniterative triple excitations (CCSD­(T)), the Møller–Plesset second-order perturbation theory (MP2), and various flavors of density functional theory (DFT) methods, we study complexes of benzene (Bz) with halogen-containing molecules X₂ and CX₄ (X = Cl/Br) and analyze various components of the interaction energy using symmetry adapted perturbation theory (SAPT). As for the lowest energy conformers (S1), X₂–Bz is found to have the T-shaped structure where the electropositive X atom-end of X₂ is pointing to the electronegative midpoint of CC bond of the Bz ring, and CX₄–Bz has the stacked structure. In addition to this CX₄–Bz (S1), other low energy conformers of X₂–Bz (S2/S3) and CX₄–Bz (S2) are stabilized primarily by the dispersion interaction, whereas the electrostatic interaction is substantial. Most of the density functionals show noticeable deviations from the CCSD­(T) complete basis set (CBS) limit binding energies, especially in the case of strongly halogen-bonded conformers of X₂–Bz (S1), whereas the deviations are relatively small for CX₄–Bz where the dispersion is more important. The halogen bond shows highly anisotropic electron density around halogen atoms and the DFT results are very sensitive to basis set. The unsatisfactory performance of many density functionals could be mainly due to less accurate exchange. This is evidenced from the good performance by the dispersion corrected hybrid and double hybrid functionals. B2GP-PLYP-D3 and PBE0-TS­(Tkatchenko-Scheffler)/D3 are well suited to describe the X−π interactions adequately, close to the CCSD­(T)/CBS binding energies (within ∼1 kJ/mol). This understanding would be useful to study diverse X−π interaction driven structures such as halogen containing compounds intercalated between 2-dimensional layers