Search

Herein, we report for the first time the use of ternary oxide nanoheterostructure photocatalysts derived from (Nby, Ti1-y)2CTx MXene in the treatment of water. Three different compositions of binary MXenes, viz., (Ti0.75Nb0.25)2CTx, (Ti0.5Nb0.5)2CTx, and (Ti0.25Nb0.75)2CTx (with Tx = OH, F, and Cl), were used as single-source precursor to produce TiNbOx-3:1, TiNbOx-1:1, and TiNbOx-1:3 by controlled-atmosphere thermal oxidation. Phase identification and Le Bail refinements confirmed the presence of a mixture of rutile TiO2 and monoclinic Ti2Nb10O29. Morphological investigations through scanning and transmission electron microscopies revealed the retention of layered nanostructures from the MXene precursors and the fusion of TiO2 and Ti2Nb10O29 nanoparticles in forming nanosheets. Among the three oxide nanoheterostructures, TiNbOx-3:1 exhibited the best photocatalytic performance by the removal of 83% of sulfamethoxazole (SMX) after 2 h of reaction. Such a result is explained by a complex influence of structural, morphological, and electronic properties since TiNbOx-3:1 consisted of small-sized crystallites (40-70 nm) and possessed a higher surface area. The suggested electronic band structure is a type-II heterojunction, where the recombination of electrons and holes is minimized during photocatalytic reactions. The photocatalytic degradation of SMX was promoted by the attack of •OH, as evidenced by the detection of 2.2 μM •OH, using coumarin as a probe. This study highlights the potential application of MXene-derived oxide nanoheterostructures in wastewater treatment. [ABSTRACT FROM AUTHOR]

Density functional cluster model calculations are performed to explore the mechanism and regioselectivity for the reactions of propylene oxide with X(100)-2x1 surfaces (X = C, Si, Ge). It is demonstrated that the reactions of propylene oxide with X(100)-2x1 surfaces (X = C, Si, Ge) are barrierless and highly exothermic, whereas the reaction of propylene oxide with the C(100)-2x1 surface could be kinetically prohibited at room temperature.

Theoretical predictions on the selectivities and mechanisms for the attachments of diacetylene on Si(100)-2 * 1, Ge(100)-2 *1, and Si(111)-7 *7 surfaces are provided. It is shown that the adsorption of diacetylene gives rise to enynic adspecies on Si(100)-2 * 1, [3]cumulenic adspecies on Si(111)-7 * 7, and both [3]cumulenic and enynic adspecies on Ge(100)-2 * 1.

The first theoretical investigation of the mechanisms for reactions of unsaturated hydrocarbons and the allied heterocyclic aromatics with the Si(111)-7x7 surface is reported. The density functional cluster model calculations predict stepwise, diradical pathways for these reactions.

Research has been conducted on the dipolar cycloadditions of the dipolar molecules onto the C(100)-2 x 1 surface. The study of these cycloadditions has been carried out via the use of the hybrid density functional method combined with the cluster model approach and the results are reported.

The article discusses research methods used to discover the quantum chemical properties of surface bonding.

The endohedral fullerene [Sc.sub.3]NC@[C.sub.80]-[I.sub.h] is prepared and analyzed, which has an unprecedented planar quinary cluster in a fullerene cage. The intramolecular dynamics in [Sc.sub.3]NC@[C.sub.80]-[I.sub.h] has enabled the whole molecule to exhibit high polarity and ferroelectricity.

An operable combustion method is used for preparing non-IPR fullerene, and an octahydro[60]fullerene with a non-IPR [C.sub.60] cage produced by combustion is isolated and characterized. The studies have shown that along with chlorine, hydrogen is an ample cataloreactant for the production of non-IPR fullerene derivatives under the conditions such as arc-burning and diffusion combustion.

A new [C.sub.1]-symmetric non-IPR hollow isomer, [super #23863][C.sub.78], was captured as [super #23863][C.sub.78][Cl.sub.8] and then subjected to a regioselective substitution reaction with benzyl hydroperoxide to obtain [super #23863][C.sub.78](OOC[H.sub.2][C.sub.6][H.sub.5])[Cl.sub.7]. The differences observed in in C-Cl bond length, intermediate stability, and steric effects of the involved molecules accounted for the chemical regioselectivity of the substitution reaction.

The stable compound [Sc.sub.4][C.sub.2]@[C.sub.80]-[I.sub.h] is produced and characterized as a metal carbide endofullerene by Fourier transform infrared (FTIR) and Raman spectroscopies along with density functional theory (DFT) calculations. DFT calculations have shown that this molecule has a Russian-doll-type structure, [C.sub.2]@[Sc.sub.4]@[C.sub.80].

The isolation and characterization of the [C.sub.56][Cl.sub.10] are described. The crystallographic data of [C.sub.56][Cl.sub.10] have shown an unusual Cl...Cl short contact and the alignment of pearl-necklace-like molecular chains, which can be converted into a class of useful one-dimensional fullerene polymer through regioselective reactions.

Density functional theory (DFT) quantum chemical calculations are used for predicting the [super 31]P NMR chemical shifts of adsorbed trimethylphosphine oxide (TMPO) and the configurations of the corresponding TMPO[H.sup.+] complexes on Bronsted acid sites with varying acid strengths in modeled zeolites. Correlations are obtained between the [super 31]P chemical shifts and proton affinities of the solid acid.

The regioselective synthesis of a Dy@[C.sub.82 ] derivative bearing a single phosphorus substituent via a zwitterion intermediate, generated by the addition of a nucleophile to an activated electrophile, is described. The new metallofullerene reaction has shown a high chemoselectivity that is different from that of [C.sub.60].

All-electron relativistic density functional computations have shown that the dimetalloendofullerene ([U.sub.2]@[C.sub.60]) has an unprecedented U-U multiple bond consisting solely of sixfold ferromagnetically coupled one-electron-two-center bonds. The bonding scheme is distinct from the metal-metal bonds, thus initiating the connection of the metal-metal multiple bonding chemistry and the fullerene chemistry.

The addition reaction of Grignard reagents to malimides is investigated by using hybrid density functional theory calculations. A summary of the reaction mechanism, regio- and diastereoselectivity, and substituent effects on the selectivities is presented.

The density functional calculations are used to show that an unprecedented [mu]4-[C2.sup.6-] anion can viably exist as an endohedral [[Sc4C2].sup.6+] cluster in the endofullerene Sc4C2 at the rate of C80. The predicted Sc4C2 at the rate of C80 structure has a stable closed-shell electronic configuration and has a five-membered endohedral cluster.

The first NMR mapping of the surface of a J domain recognizing a mammalian hsp70, the ATPase domain of Hsc70, is presented. T antigen is hypothesized to position Hsc70 for direct action upon an E2F bound to a pocket protein such as pRb, and this region binding with E2F1 is demonstrated to be an excellent substrate for Hsc70 in vitro, possibly because of an inherently unfolded region.

The synthesis of a stable unconventional unconventional fullerene derivative [C.sub.64][H.sub.4] which was carried out by introducing methane in the fullerene productions with normal Kratschmer-Huffman method is described. Once the four carbon atoms at vertexes of the fused pentagon sites were chemically modified by hydrogen additions, the s[p.sup.2] to s[s.sup.3] hybridization change of the vertex carbon atoms would release remarkably the bond strains, affording the high stability of the [C.sub.64][H.sub.4] structure.

Quantum chemical calculations are used to show that the inorganic ions Se2I4(super 2+) and S2O4(super 2-) have aromaticity resulting from through-space conjugation. This aromaticity is analogous to the aromaticity in the transition states of some pericyclic reactions, such as Cope rearrangements and Diels-Alder reactions.

The La2 (at the rate of) C72 and Sc2 (at the rate of) C72 metallofullerenes are characterized by systematic density functional computations and on the basis of the most stable geometry of 39 C72 hexaanions and the computed energies of the best endofullerene candidates, the experimentally isolated La2 (at the rate of) C72 species are assigned the structure coded #10611.The geometry, IR vibrational frequencies, and (super 12)C chemical shifts of Sc2 (at the rate of) C72 are predicted to assist its future experimental characterization.

The theoretical investigation aims to resolve the electronic structure and explore the redox properties of Sc(sub 3)C(sub 2)@C(sub 80) to know how the structure of the encased cluster responds to the redox. The electrochemical redox properties of the open-shell metal-carbide endofullerene are elucidated in terms of electronic structure theory and density functional theory (DFT) calculations show its valence state.

Multinuclear solid-state NMR techniques and DFT quantum chemical calculations were employed to investigate the detailed structure of acid sites on the BF(sub 3)/Gamma-Al2O3 alkylation catalyst. DFT calculations revealed the detailed structure of various acid sites formed on the BF(sub 3)/Gamma-Al2O3 catalyst and the interaction of probe molecules with these sites.

A comprehensive survey of different C-H activation pathways over various kinds of active sites of terminal oxygens [=O] and bridge oxygens [-O-] by using Mo3O9 model systems is presented. The results suggest that H abstraction is the most feasible reaction pathway for the activation of a C-H bond on molybdenum oxides and that [=O] is more active than [-O-].

A systematic density functional study on the electronic and spectroscopic properties of C50, its anions and derivatives such as C50Cl10 and C50Cl12 is performed. Findings show that both D3 and D5h isomers of C50 have high electron affinities and can be reduced easily. Due to the unstable fused pentagon structural features, C50 is chemically labile and subject to addition reactions such as chlorination, dimerization and polymerization.

The systematic density functional cluster model calculations reveal that the [2+2] cycloadditions of ethylene follow diradical mechanisms on the (100) surfaces of group IV semiconductors (silicon, germanium and diamond). The reaction pathway varies with the bonding nature of the surface dimers which includes their zwitterionicity, weakness of their pi-bond, and readiness to react as a diradical.

An exploration of the reaction pathway and site selectivity or the [2+1] cycloadditions of dicholorocarbene and oxycarbonylnitrene onto the sidewalls of single-wall nanotube (SWNTs) is carried out. In addition, it is predicted that whether such [2+1] cycloaddition chemistry can be extended to other reactants, such as silylenes and germylenes, on the sidewalls of SWNTs.

A study showed that by means of density functional cluster model calculations, the adsorption of ethylene on Si(100) surface follows a diradical mechanism, proceeding visa pai-complex precursor and a singlet diradical intermediate. The calculations confirmed the scanning tunneling microscopy (STM) observation that the adsorption of an alkene on Si(100) is not stereospecific but highly stereoselective in nature.

A theoretical prediction of the facile 1,3-dipolar cycloaddition of an organic azide (methyl azide) and a diazo compound (diazo-methane) onto the diamond (100) surface, a new type of surface reaction that can be used to functionalize diamond surface at a low temperature is presented. This new type of surface reaction in combination with the wide variety of 1,3-dipolar molecules provides high flexibility of functionalizing and fabricating the diamond films at a low temperature.

The adsorption and adsorption-induced dimerization and trimerization of CO over the low-coordinated oxygen anions of MbO solid is explored by the hybrid B3LYP density functional method together with cluster models. The findings suggest that the dimeric adspecies are unlikely to be stable adspecies, but may be the intermediates for the formation of higher oligomeric adspecies of CO.

A novel fibrous sorbent, amidoxime-grafted activated carbon fibers (ACFs-AO), was prepared using a chemical grafting method and tested for the efficient removal of uranium from aqueous solution. The sorbent was characterized using X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, elemental analysis, thermogravimetric analysis, and Brunauer-Emmett-Teller. The effects of pH, contact time, initial concentration, and temperature on the sorption of U(VI) were investigated. The sorption of U(VI) on ACFs-AO obeyed the pseudo-second-order model and Langmuir isotherm. The sorption capacity of ACFs-AO for U(VI) (about 191.6 mg/g) was much higher than that of activated carbon fibers (ACFs) (about 70.52 mg/g), which was mainly attributed to surface complexation between U(VI) and the amidoxime group on ACFs-AO. Additionally, the thermodynamic parameter results showed that the sorption process of U(VI) was spontaneous, feasible, and endothermic. Moreover, ACFs-AO adsorbed U(VI) selectively in an aqueous solution containing competitive ions, and was regenerated and reused efficiently. The findings of this work indicate that ACFs-AO could be a promising sorbent for the effective removal of U(VI) from aqueous solution. [ABSTRACT FROM AUTHOR]

The study conducted suggests that the central 7-7 ring fusion at the Stone-Wales defect in the (5,5) single-wall carbon nanotubes (SWNT) sidewall is less reactive than the defect-free sites. Density functional calculations using periodic boundary conditions are performed for an infinite (5,5) single-wall carbon nanotube without/with a Stone-Wales defect.