Yuan-Ru Guo

Low-temperature precipitation synthesis of flower-like ZnO with lignin amine and its optical properties

A facile precipitation method has been developed to synthesize ZnO with [bis(2-aminoethyl)amino]methyl lignin (lignin amine) that is chemically modified from low-cost pulp industrial lignin. The obtained ZnO crystallites have been characterized to exhibit a hexagonal wurtzite structure, and their sizes have been determined at ca. 24 nm (mean value). These ZnO nanocrystallites are of high purity and well crystallized. Our present synthetic approach apparently exempts the commonly used calcining purification procedure. It is found that the morphology of ZnO and its specific surface area are capable of being tuned by varying the added lignin amine amount. Using the optimal 10 mL lignin amine, the synthesized ZnO exhibits flower-like morphology with proper specific surface area. Additionally, photoluminescence property of the obtainable ZnO displays two emissive bands at 383 nm (sharp) and in the range of 480 to 600 nm (broad) at room temperature. Their intensities were revealed to depend on the added lignin amine amount as well as on the molar ratio of Zn2+/OH-. The present investigation demonstrates that our method is simple, eco-friendly, and cost-effective for the synthesis of small-size ZnO materials.

Cellulose nanofiber induced self-assembly of zinc oxide nanoparticles: Theoretical and experimental study on interfacial interaction

In-depth understanding of interfacial behavior between biopolymer and semiconductor metal oxides is crucial to developing potential applications of their composites. A structure-ordered cellulose/zinc oxide composite was synthesized and systematically examined by a relativistic density functional theory. The prepared composite shows a hierarchical structure. ZnO nanoparticles of around 30 nm in size are found to uniformly grow along the cellulose fiber, which together construct the primary-structure unit. Associated with experimental characterizations, calculations unravel that the electrostatic attraction between cellulose and ZnO is the main driving force to form the primary structure and the subsequent electron transfer from cellulose to ZnO enhances their interfacial interaction; moreover, an exothermic process was computed. The interfacial interaction is mainly contributed by Zn-Oc (Oc denotes the cellulose oxygen atom), which is intrinsically of a dative bond; the interaction was calculated between -1.39 and -1.83 eV in strength and dominated by orbital attractions.

A Theoretical Probe for Structures, Metal–Metal Bonding, and Electronic Spectra of Paramagnetic Tetrapyrrolic RuII Complex

Dimeric complexes (RuIIPz)2 have been investigated using density functional theory (DFT), where Pz is a porphyrazine ligand that features a 16-atom, 18-π-electron cyclic polyene aromatic skeleton. Structural optimizations in various configurations and spin states indicate that (RuPz)2 favours a Pz–Pz staggered conformer over an eclipsed one; the paramagnetic triplet state with the staggered configuration is found as the global ground state. This agrees with experimental magnetic results of (RuOEPor)2 (OEPor = octaethylporphyrin) and (RuPc)2 (Pc = phthalocyanine). The Ru–Ru bond length was optimized to be 2.38 A, close to the experimental bond length of 2.40–2.41 A. The Ru2 doubly bonded nature has been evidenced by the Ru–Ru stretching vibrational frequency of 202 cm–1, bond energy of 30.7 kcal mol–1, and electronic arrangement of σ2π4(nonbonding-δ)4(π*)2. Further confirmation was obtained from high-level wave function theory calculations (complete active space self-consistent field and n-electron valence state second-order perturbation theory). Associated with the solvation of the explicit pyridine accounting for the first coordination sphere and the implicit continuum model for the long-range interaction, the electronic spectra of tetrapyrrolic ruthenium complex were calculated at the time-dependent DFT level.

A relativistic DFT probe of polypyrrolic macrocyclic diuranium(III) complexes with terminal solvents and iodines

AbstractRelativistic density functional theory finds that two isomers of a diuranium(III) complex of a polypyrrolic macrocycle (H4L) feature active sites on uranium moieties, allowing for their potential application in activating industrially and economically important small molecules. To address this, a series of adducts [(X)nU2(L)](2–m)+ (X = THF, I− and HI; n = 1 and 2; m = 0, 1 and 2) have been examined. The coordination from X to the exposed uranium(s) changes the general geometry and electronic structure slightly. Thermodynamic calculations reveal that iodine termination is energetically favored over THF/HI coordination. Graphical abstractScalar and spin-orbit coupling relativistic DFT calculation reveals that the active sites on the uranium moieties of [U2(L)]2+ lead to formation of adducts [(THF)nU2(L)]2+, [InU2(L)](2–n)+ and [(HI)nU2(L)]2+ (n = 1 and 2). Coordination to the exposed uranium(s) changes geometrical and electronic properties slightly, but iodine termination is the most energetically favored.

Structural/electronic properties and reaction energies of a series of mono- and bis-uranyl dihalides equatorially coordinated by N/O ligands

AbstractMonometallic (UO2)(X)2(L)3 (L = pyridine (py), X = F (1), Cl (2), Br (3) and I (4); L = tetrahydrofuran (thf), X = Cl (5); L = pyrrole (pl), X = Cl (6)) as well as bimetallic [(UO2)(μ2-X)(X)(L)2]2 (L = py, X = F (7), Cl (8), Br (9) and I (10); L = thf, X = Cl (11); L = pl, X = Cl (12); μ2 = doubly bridged) were examined using relativistic density functional theory. With changing from F, Cl, Br to I irregardless of in mono- or bis-uranyl complexes, bond lengths of U = O were calculated to be decreasing, resulting from strengthening of axial U = O bonds while weakening equatorial X → U coordination. This is further evidenced by calculated bond orders of U = O and stretching vibrational frequencies. A similar situation was is found in 2, 5 and 6 as well as in 8, 11 and 12, where N/O ligands are varied but the chlorine atoms are retained. The present study reveals that all these complexes have U(f)-character low-lying unoccupied orbitals, and their π*(U = O) antibonds are located on higher-energy orbitals. Complex 1 was calculated to show σ(U = O) bonding character for HOMO, and pyridine-character for other occupied orbitals; the fluorine ligand occurs in a relatively low-energy region. In contrast, the π(p) characters of heavier halogen atoms significantly contribute to most frontier molecular orbitals of 2, 3 and 4. Unlike this electronic feature of 2, complexes 5 and 6 exhibit mainly thf and pyrrole characters, respectively, for their high-lying occupied orbitals. Electronic structures of bisuranyl complexes 7–12, albeit a little more complicated, are revealed to be similar to those of the corresponding monouranyl complexes. Finally, energies of formation reactions of the above complexes were calculated and compared with available experimental results. FigureA series of mono- and bis-uranyl complexes, including experimentally known as well as theoretically designed (in silico) complexes, have been studied for their structural, electronic and energetic properties using relativistic density functional theory. Regular changes, for instance, are revealed for orbitals with σ(U = O) + π[pz(X)] character. Calculations of thermodynamic energies evidenced an experimental transformation from monouranyl to bisuranyl complex.