To explore the interactions of nanoparticles and bioresources and elucidate their effects on the morphology of the resulting composite, hierarchically structured cellulose@ZnO composites have been ...synthesized by an environmentally friendly hydrothermal method in one step. First, self-assembly induces the formation of hierarchical three-level structures, including cellulose/ZnO nanofibers, layers, and microfibers. Then, ZnO microparticles deposit onto the surface of the third-level cellulose/ZnO microfibers and accomplish the fabrication of a cellulose@ZnO composite, which eventually defines the hierarchical morphology of synthesized materials. The self-assembly mechanism was comprehensively examined. The electrostatic attraction between cellulose and ZnO, not hydrogen bonding, was found to be the main driving force for the formation of the first-level structure. A density functional theory study was conducted to support the self-assembly mechanism by optimizing the cellulose/ZnO structures at the molecular level, computing the corresponding thermodynamic energies and examining the spectroscopic properties. A hierarchically structured cellulose@ZnO composite is found to enhance the antibacterial activities. The diameters of the inhibition zone were found to be 48.8 and 45.5 mm against the Gram-positive bacterium Staphylococcus aureus (S. aureus) and the Gram-negative bacterium Escherichia coli (E. coli), respectively. This study is expected to improve food packaging materials while utilizing our newly synthesized cellulose@ZnO composite.
The hydrothermal reaction of uranyl ions with (5-methyl-1,3-phenylene)diphosphonic acid (H4MPDP) in the presence of additives such as nitric acid, N-bearing species, and heterometal ions yielded ...five new uranyl organic hybrids: (H3O)(UO2)5(H2O)4(H3DPB)2(H2DPB)(HDPB)·2H2O (1), (Hphen)(phen)(UO2)3(H2DPB)(HDPB) (2), (H2dipy)(UO2)3(MPDP)2 (3), Zn(bipy)(UO2)(MPDP) (4), and Co(bipy)(UO2)(MPDP)·H2O (5) (H5DPB = 3,5-diphosphonobenzoic acid; phen = 1,10-phenanthroline; dipy = 4,4′-bipyridine; bipy = 2,2′-bipyridine). Single-crystal X-ray diffraction (XRD) demonstrates that 1 and 2 are 3D frameworks constructed of uranyl centers and carboxyphosphonate DPB ligands; the latter were formed via the in situ oxidation of H4MPDP. In the homometallic uranyl diphosphonate 3, less common UO6 square bipyramids connected by MPDP ligands were incorporated to form the 2D assembly. A further introduction of heterometal ions produced two heterobimetallic uranyl phosphonates 4 and 5. Both of them show layered structures, formed by UO6 square bipyramids linked by MPDP ligands with heterometal-centered polyhedra decorated on the sides of the layers. It is found that the pH and heterometal ions have significant effects on the structures of the complexes. In addition to the syntheses and XRD characterization, the spectroscopic properties of these uranyl complexes were also addressed. To complement the experimental results, density functional theory calculations were carried out on several model complexes that feature a homo- or heterobimetallic molecular skeleton. Geometrical/electronic structures, IR spectra, and electronic absorptions were discussed.
Designing novel catalysts is essential for the efficient conversion of metal alkylidyne into metal oxo ketene complexes in the presence of CO2, which to some extent resolves the environmental ...concerns of the ever-increasing carbon emission. In this regard, a series of metal alkylidyne complexes, b-ONO MCCH3(THF)2 ( b-ONO = {(C6H4C(CF3)2O)2N}3–; M = Cr, Mo, W, and U), have been comprehensively studied by relativistic density functional theory calculations. The calculated thermodynamics and kinetics unravel that the tungsten complex is capable of catalyzing the CO2 cleavage reaction, agreeing with the experimental findings for its analogue. Interestingly, the uranium complex shows superior catalytic performance because of the associated considerably lower energy barrier and larger reaction rate constant. The MC moiety in the complexes turns out to be the active site for the 2 + 2 cyclic addition. In contrast, complexes of Cr and Mo could not offer good catalytic performance. Along the reaction coordinate, the M–C (M = Cr, Mo, W, and U) bond regularly transforms from triple to double to single bonds; concomitantly, the newly formed M–O in the product is identified to have a triple-bond character. The catalytic reactions have been extensively explained and addressed by geometric/electronic structures and bonding analyses.
Two novel three-dimensional interpenetrated uranyl–organic frameworks, (NH4)4(UO2)4(L1)3·6H2O (1) and (UO2)2(H2O)2L2·2H2O (2), where L1 = tetrakis(3-carboxyphenyl)silicon and L2 = ...tetrakis(4-carboxyphenyl)silicon, were synthesized by a combination of two isomeric tetrahedral silicon-centered ligands with 3-connected triangular (UO2)(COO)3− and 4-connected dinuclear (UO2)2(COO)4 units, respectively. Structural analyses indicate that 1 possesses a 2-fold interpenetrating anion bor network, while 2 exhibits a 3-fold interpenetrated 4,4-connected neutral network with pts topology. Both compounds were characterized by thermogravimetric analysis and IR, UV–vis, and photoluminescence spectroscopy. A relativistic density functional theory (DFT) investigation on 10 model compounds of 1 and 2 shows good agreement of the structural parameters, stretching vibrational frequencies, and absorption with experimental results; the time-dependent DFT calculations unravel that low-energy absorption bands originate from ligand-to-uranium charge transfer.
Catalysis operated on supported single metal atom is considered as one of the vital efforts for chemical and energy conversion. Despite the enormous amount of research on single transition metal (TM) ...enhanced graphdiyne (GDY) material, its modification with slightly depleted uranium remains unexplored. Herein, we conducted relativistic density functional theory (DFT) calculations for the accumulation of atomic uranium inside size-suitable GDY pore. The stability of graphdiyne-uranium (GDY-U) is corroborated in terms of short U–C bond distances (2.34–2.44 Å), with local depletion of charge and greater U(5f)-C(p) molecular orbital overlap. The magnificent structural and electronic properties of GDY-U system qualify it for the investigation of hydrogen evolution reaction (HER). The HER performance of all exposed sites, including central metal atom and four dissimilarly coordinated acetylenic carbons has been examined and compared with that of pure GDY. As the overall HER interfacial descriptor, free energy change of the intermediate state (ΔGH∗) at the central metal surface of GDY-U was found to be most favorable (0.153 eV) amongst all sites and far superior to those of pure GDY. In addition to the uranium surface, the coordinated carbons also show improved HER activity, indicating the enhancement of the system upon metal insertion. The calculated ΔGH∗ of the GDY-U system here is comparable to some of the recently reported GDY-TM materials, suggesting that atomic uranium could be an exceptional alternative for applied common catalysts.
The atomic-uranium was encapsulated into graphdiyne, leading to the activation of central metal and connected carbons (C1, C2, C3, C4). The free energy for the Volmer step at uranium is 0.153 eV, while the molecular H2 formation is favored by Volmer-Tafel route. Display omitted
•Graphdiyne-uranium as single-atom-catalysis material shows good HER performance.•Strong-Metal-Support-Interaction with great U(5f)-C(2p) overlap and localization.•Activation of all exposed sites including metal surface and connected carbons.•GH∗ = 0.153 eV at metal center and carbons shows superiority for overall HER.•Volmer-Tafel is slightly favored over Volmer-Heyrovsky at the metal surface.
Hierarchical petaloid-array structure of carbon dots/Mg(OH)2 (marked as CDs/Mg(OH)2) composite was prepared via a facile method. The synergistic effect of Mg(OH)2 and CDs enable composite o recover ...Cd(II) ions at a controllable rate and produce Cd(OH)2 1D nanowires.
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•Petaloid-array carbon dots/Mg(OH)2 was prepared by a facile method.•DFT study recognized the composite structure and explored interfacial property.•Cd(II) was removed at a controllablerate by synergistic effect of composite.•Cd(OH)2 was recovered as 1D nanowires.•The removal capacity of composite reaches 1015.4 mg g−1.
The ever-growing contamination of water resources generated by heavy metals is posing significant threat to sustainable development, and urging the necessity of safe disposal. In this work, we designed a facile method to prepare carbon dots/Mg(OH)2 (marked as CDs/Mg(OH)2) composite, which enables to remove and recover potentially toxic metal of Cd2+ from water. The newly-prepared CDs/Mg(OH)2 features a hierarchical petaloid-array structure and has large specific surface area of 96.2 m2 g−1. It is evident that the composite is composed of Mg(OH)2 slices, to which CDs are attached. Density functional theory calculation recognized the composite microstructure at the atomic level. Weak chemical coupling between sub-units were borne out by optimized structures, energetics, infrared vibrations, and electronic structures. The CDs/Mg(OH)2 composite shows high removal capacity and long durability while treating Cd(II)-contaminated water. The incorporation of CDs could regulate and control the up-taking rate of Cd2+ ions and consequently fabricate well-dispersed 1D nanowires of Cd(OH)2. The corresponding mechanism was proposed. Specifically, the sample CDs/Mg(OH)2-60 reaches 1015.4 mg g−1 removal capacity; it can be used for 12 cycles and still keep removal efficiency as high as 98.6%.
The infectious diseases caused by various bacteria pose serious threat to human health. To solve this problem, antibacterial agents have been widely used in people’s daily life to deactivate or kill ...these bacteria. Among the antibacterial agents, ZnO is one of the most promising metal oxide antibacterial agents due to its non-toxic nature and safe properties. To expand its application, many composites of ZnO have been widely studied. Cellulose, as one of the most abundant biopolymers, has many merits like biodegradability, biocompatibility and low cost. Thus, many studies focus on synthesized cellulose/ZnO. The synthetic strategy includes both chemical and physical methods. Many of them have been shown that cellulose/ZnO composites have excellent antibacterial activity and are environment-friendly and have many applications for example food packing, antibacterial fibers and so on. This review mainly discusses the preparation methods of cellulose/ZnO and their effect on the morphology and properties.
To explore the innovative uranyl(V) complexes by deeply understanding their coordination stability, relativistic density functional theory calculations have been performed to investigate the ...experimentally reported (py)(R2AlOUVO)(py)(H2L) R = Me (1), i Bu (2) and {(py)3MOUVO}(py)(H2L) M = Li (3), Na (4), K (5) and their uranyl(VI) counterparts. Structural and topological analyses along with transformation-reaction energies and redox potentials were systematically studied. Geometrical and quantum theory of atoms in molecules analyses implied a linear U–O exo –M feature in 1–3 and a bent one in 4 and 5. The calculated free energies (Δr G) of reactions transforming 1/2 into 3/4/5 confirmed a higher stability of the latter ones, which were further corroborated by their reduction potentials (E 0). The E 0 value of 5 versus uranyl(VI) is close to its experimental value, particularly in solvation with spin–orbit coupling. The highest occupied and lowest unoccupied molecular orbitals of uranyl(V) and uranyl(VI) have predominant U(5fδ) character. Compared to mononuclear uranyl(VI), the coordination of aluminum and alkali metals to uranyl exo-oxo significantly contributes to the stabilization of uranyl(V) by altering the E 0 value from −1.59 to −0.85, −0.91, −1.33, −1.50, and −1.46 V, respectively. The calculation results show a more positive E 0 than that of the precursor 6 VI /6 without exo-oxo coordination. The calculated E 0 values of 3–5 are certainly more negative than those of 1 and 2. The alkali metals were found to activate UO bonds more easily/readily than aluminum by coordination to the exo-oxo atom. In brief, the uranyl exo-oxo cation–cation-interaction enhanced the reduction ability from its uranyl(VI) analogue and raised the stability of the UV center.
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