Growth and Optical Properties of the Whole System of Li(Mn1-x,Nix)PO4 (0 ≤ x ≤ 0.5) Single Crystals.

A series of single crystals of Li(Mn1-x,Nix)PO4 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.10, 0.15, 0.20, and 0.50) have been grown to large sizes up to 5 mm in diameter and 120 mm in length using the floating zone method for the first time. The comprehensive characterizations of the as-grown crystals were performed before further physical property measurements. The composition of the grown crystals was determined by energy-dispersive X-ray spectroscopy. The crystal structures were characterized by the X-ray powder diffraction method with a GSAS fitting for structural refinement, which reveals a high phase purity of the as-obtained crystals. The polarized microscopic images and Laue patterns prove the excellent quality of the single crystals. Oriented cuboids with sizes of 2.7 × 3.8 × 2.1 mm3 along the a, b, and c crystalline directions were cut and polished for further anisotropic magnetic and transparent measurements. We also first proposed a new potential application in the non-linear optical (NLO) and laser generation application for LiMPO4 (M = transition metal) materials. The optical and laser properties, such as the absorption spectra and the second harmonic generation (SHG), have been investigated and have furthermore confirmed the good quality of the as-grown single crystals.

Investigations of the Kinetics and Mechanism of Reduction of a Carboplatin Pt(IV) Prodrug by the Major Small-Molecule Reductants in Human Plasma.

The development of Pt(IV) anticancer prodrugs to overcome the detrimental side effects of Pt(II)-based anticancer drugs is of current interest. The kinetics and reaction mechanisms of the reductive activation of the carboplatin Pt(IV) prodrug cis,trans-[Pt(cbdca)(NH3)2Cl2] (cbdca = cyclobutane-1,1-dicarboxylate) by the major small-molecule reductants in human plasma were analyzed in this work. The reductants included ascorbate (Asc), the thiol-containing molecules L-cysteine (Cys), DL-homocysteine (Hcy), and glutathione (GSH), and the dipeptide Cys-Gly. Overall second-order kinetics were established in all cases. At the physiological pH of 7.4, the observed second-order rate constants k' followed the order Asc << Cys-Gly ~ Hcy < GSH < Cys. This reactivity order together with the abundances of the reductants in human plasma indicated Cys as the major small-molecule reductant in vivo, followed by GSH and ascorbate, whereas Hcy is much less important. In the cases of Cys and GSH, detailed reaction mechanisms and the reactivity of the various protolytic species at physiological pH were derived. The rate constants of the rate-determining steps were evaluated, allowing the construction of reactivity-versus-pH distribution diagrams for Cys and GSH. The diagrams unraveled that species III of Cys (-SCH2CH(NH3+)COO-) and species IV of GSH (-OOCCH(NH3+)CH2CH2CONHCH(CH2S-)- CONHCH2COO-) were exclusively dominant in the reduction process. These two species are anticipated to be of pivotal importance in the reduction of other types of Pt(IV) prodrugs as well.

Spectroscopic, kinetic, and theoretical analyses of oxidation of dl-ethionine by Pt(IV) anticancer model compounds.

Ethionine is an S-ethyl analog of methionine (Met) having a small change in structure. But it is a chemical carcinogen and an antagonist of Met, thus displaying a disparate biological profile. The oxidations of ethionine by biologically important oxidants have not been exploited. Oxidations of dl-ethionine by Pt(IV) anticancer model complexes trans-[PtX2(CN4)]2- (X = Cl or Br) were thus analyzed by time-resolved and stopped-flow spectral techniques. Overall second-order kinetics was established, being first-order in [Pt(IV)] and [Ethionine]tot (the total concentration of ethionine); the observed second-order rate constant k' versus pH profiles were obtained. A stoichiometry of Δ[Pt(IV)]:Δ[Ethionine]tot = 1:1 was unraveled, indicating that ethionine was oxidized to ethionine-sulfoxide which was confirmed by NMR spectroscopic and high-resolution mass spectral analyses. In the proposed reaction mechanism which is similar to that for the oxidation of Met by the same Pt(IV) compounds, the rate-determining steps are rationalized in terms of a bridge formation between one of the coordinated halides in [PtX2(CN4)]2- and the sulfur atom in ethionine, followed by an X+ transfer. Moreover, a large rate enhancement for the reaction of ethionine with [PtBr2(CN4)]2- compared with [PtCl2(CN4)]2- strongly supports an X+ transfer mechanism. Furthermore, a combined quantum-mechanical/molecular-mechanical (QM/MM) method was utilized to simulate a Cl+ transfer mechanism from trans-[PtCl2(CN)4]2- to ethionine. The simulations unraveled the energetically stable structures of reactants and products, which favor the Cl+ transfer process. Rate constants of the rate-determining steps have been derived. Ratios of k (ethionine)/k (Met) are between 2.2 and 2.6 obtained for the three protolytic species of ethionine and Met; the enhanced reactivity might be partially responsible for the disparate biological profiles.

Photocatalytic Overall Water Splitting over MIL-125(Ti) upon CoPi and Pt Co-catalyst Deposition.

Photocatalytic overall water splitting is realized by taking advantage of the semiconductive and porous properties of MIL-125(Ti). CoPi and Pt are deposited into MIL-125(Ti) in two steps. The co-catalysts CoPi and Pt not only act as reactive sites for oxygen and hydrogen evolution, respectively, but also improve the photogenerated charge separation efficiency. The above conclusions are supported by the photoelectrical and photophysical results.

NiII Coordination to an Al-Based Metal-Organic Framework Made from 2-Aminoterephthalate for Photocatalytic Overall Water Splitting.

The aluminum-based metal-organic framework (MOF) made from 2-aminoterephthalate is a photocatalyst for oxygen evolution. This MOF can be modified by incorporating Ni2+ cations into the pores through coordination to the amino groups, and the resulting MOF is an efficient photocatalyst for overall water splitting.

An efficient visible-light photocatalyst made from a nonpolar layered semiconductor by grafting electron-withdrawing organic molecules to its surface.

A nonpolar inorganic layered semiconductor becomes an efficient visible-light photocatalyst when its surface layer becomes polar by chemically attaching electron-withdrawing 4-substituted thiophenolates -S-C6H4Z (Z = NO2, COOH, Cl, Br, H, CH3, NH2) via Bi-S bonds. An in-depth study finds a correlation between the apparent rate constant (kapp) and the Hammett constants σpara of the 4-substituted groups.

Novel heterostructured Bi2S3/BiOI photocatalyst: facile preparation, characterization and visible light photocatalytic performance.

Novel Bi(2)S(3)/BiOI heterostructures were successfully synthesized through a facile and economical ion exchange method between BiOI and thioacetamide (CH(3)CSNH(2)), and characterized by multiform techniques, such as XRD, Raman, FT-IR, XPS, SEM, TEM, HRTEM, SAED, BET and DRS. The obtained Bi(2)S(3)/BiOI photocatalysts showed excellent photocatalytic performance for decomposing organic dye methyl orange (MO) compared with pure BiOI under visible light irradiation (λ > 420 nm). Among the Bi(2)S(3)/BiOI photocatalysts with different molar percentage of Bi(2)S(3) to initial BiOI (from 2 to 8%), 4% Bi(2)S(3)/BiOI exhibited the highest photocatalytic activity with apparent k(app) of 0.2968 h(-1). Differently, Bi(2)S(3)/BiOI displayed low photocatalytic activity for many colorless organic substrates, such as phenol, 2-chlorophenol, dimethyl phthalate and 5-sulfosalicylic acid. Moreover, the study on the mechanism suggested that the enhanced photocatalytic activity mainly resulted from the role of Bi(2)S(3)-BiOI heterojunctions formed in the Bi(2)S(3)/BiOI, which could lead to efficient separation of photoinduced carriers.

Visible light photocatalytic activity enhancement and mechanism of AgBr/Ag3PO4 hybrids for degradation of methyl orange.

Novel AgBr/Ag(3)PO(4) hybrids were synthesized via an in situ anion-exchange method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and UV-vis diffuse reflectance spectroscopy (DRS). Under visible light (λ>420 nm), AgBr/Ag(3)PO(4) degraded methyl orange (MO) efficiently and displayed much higher photocatalytic activity than that of pure AgBr or Ag(3)PO(4). X-ray photoelectron spectroscopy (XPS) suggests that AgBr/Ag(3)PO(4) transformed to be Ag@AgBr/Ag(3)PO(4)@Ag system while remained good photocatalytic activity after 5 times of cycle experiments. In addition, the quenching effects of different scavengers proved that reactive OH and h(+) played the major role for the MO degradation. The photocatalytic activity enhancement of AgBr/Ag(3)PO(4) is closely related to the efficient separation of electron-hole pairs derived from the matching band potentials between AgBr and Ag(3)PO(4), as well as the good electron trapping role of Ag nanoparticles in situ formed on the surfaces of AgBr and Ag(3)PO(4) particles during the photocatalytic reaction.