Visual detection of melamine in milk products by label-free gold nanoparticles

A simple, rapid, field-portable colorimetric method for the detection of melamine based on melamine-induced color change of label-free gold nanoparticles (Au NPs) was developed in this study. Melamine can induced the aggregation of Au NPs and results in the color change from wine-red to purple, which provided a platform for rapid and field-portable colorimetric detection of melamine. The proposed method can be used to detect melamine in liquid milk and infant formula with a detection limit of 1.0 and 4.2 ppm, respectively, within 30 min by naked eyes observation without the aid of any advanced instrument and the need of any complex pretreatment, and detect as low as 0.15 ppm of melamine in liquid milk and 2.5 ppm of melamine in infant formula with UV-vis-spectroscopy. The proposed method is promising for on-site screening of melamine adulterant in milk products.     

Quantitative analysis of triazine herbicides in environmental samples by using high performance liquid chromatography and diode array detection combined with second-order calibration based on an alternating penalty trilinear decomposition algorithm

A novel application of second-order calibration method based on an alternating penalty trilinear decomposition (APTLD) algorithm is presented to treat the data from high performance liquid chromatography-diode array detection (HPLC-DAD). The method makes it possible to accurately and reliably analyze atrazine (ATR), ametryn (AME) and prometryne (PRO) contents in soil, river sediment and wastewater samples. Satisfactory results are obtained although the elution and spectral profiles of the analytes are heavily overlapped with the background in environmental samples. The obtained average recoveries for ATR, AME and PRO are 99.7 ± 1.5, 98.4 ± 4.7 and 97.0 ± 4.4% in soil samples, 100.1 ± 3.2, 100.7 ± 3.4 and 96.4 ± 3.8% in river sediment samples, and 100.1 ± 3.5, 101.8 ± 4.2 and 101.4 ± 3.6% in wastewater samples, respectively. Furthermore, the accuracy and precision of the proposed method are evaluated with the elliptical joint confidence region (EJCR) test. It lights a new avenue to determine quantitatively herbicides in environmental samples with a simple pretreatment procedure and provides the scientific basis for an improved environment management through a better understanding of the wastewater-soil-river sediment system as a whole.     

Three New Illudalane Sequiterpenoids from Pteris semipinnata

The chemical investigation of the aerial parts of Pteris semipinnata resulted in the isolation of three illudalane sesquiterpenoids, namely (2R)‐norpterosin B ( 1 ), (2R)‐12‐O‐β‐D ‐glucopyranosylnorpterosin B ( 2 ), and semipterosin A ( 3 ), along with three known compounds. The structures of 1 – 3 were established by spectroscopic methods, including extensive 2D‐NMR and CD analyses.     

Theoretical studies on the electronic structures and spectroscopic properties of a series of novel N?C?N‐coordinating Pt(II) complexes

The electronic structures and spectroscopic properties of the three tridentate cyclometalated Platinum(II) complexes PtL¹Cl [L¹ = 1,3‐di(2‐pyridyl)‐5‐methyl‐benzene] ( 1 ), PtL²Cl [L² = 1‐(2‐pyridyl)‐3‐(1‐pyrazolyl)‐5‐methyl‐benzene] ( 2 ), and PtL³Cl [L³ = 1,3‐bis(1‐pyrazolyl)‐5‐methyl‐benzene] ( 3 ) were calculated to explore their spectroscopic nature. The geometry structures of 1 – 3 in the ground and excited states were optimized under the density functional theory (DFT) and the single‐excitation configuration interaction (CIS) level, respectively. The absorption and emission spectra in CH₂Cl₂ solution were calculated by the time‐dependent density‐functional theory (TD‐DFT) with the polarized continuum model solvent model. As revealed from the calculations, the LUMO of 1 and 2 are localized on phenyl and pyridyl, but that of 3 has 50.3% π*(pyrazolyl) and 47.8% π*(phenyl). The energy gap of the d‐d state was much greater than that of the CT transitions. With the replacement of pyridyl by pyrazolyl, the electron‐donating ability of N atom decreases, whereas the LUMO energy level increases. The lowest‐energy absorptions and emissions are blue‐shifted in the order 1 > 2 > 3 , which are assigned as the ILCT/MLCT/LLCT and ³ILCT/³MLCT/³LLCT characters, respectively. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

[Cd2(tren)2(dl-alaninato)](ClO4)3: an efficient water-compatible Lewis acid catalyst for chemo-, regio-, and diastereo-selective allylation of various aldehydes

The use of [Cd₂(tren)₂(dl-alaninato)](ClO₄)₃·H₂O (I) (tren = tris(2-aminoethyl)amine) as an efficient water-compatible Lewis acid catalyst for the allylation of aldehydes in aqueous media was described. The reaction proceeded smoothly to afford the corresponding homoallyl alcohols in up to 96% yield. Additionally, cinnamyltributylstannane was selected as the allylation reagent, the regio- and diastereoselectivity of the reaction favors the formation of the γ-product and the anti isomers, respectively.     

Improved hydrolytic stability of poly(dl-lactide) with epoxidized soybean oil

The multi-arm star polymer (ESOPLA) was obtained by ring-opening polymerization of dl-lactide using multifunctional epoxidized soybean oil (ESO) as an initiator in the presence of a stannous actuate (SnOct₂) catalyst. Gel permeation chromatography with multi-angle laser light scattering (GPC-MALLS), FTIR, ¹H NMR, thermal analysis and in vitro degradation were used to qualitatively characterize the synthesized polymers. The results revealed that ESO plays an important role in increasing the molecular weight, polymerization rate and monomer conversion rate. Degradation analysis demonstrated that the decrease in molecular weight and the weight loss ratio of the star-shaped ESOPLA were lower than that of linear poly(dl-lactide) (PDLLA). The surface topography of pre- and post-degradation materials was characterized by scanning electron microscopy (SEM). These SEM images showed that the linear PDLLA films underwent water erosion more readily than the star-shaped polymer films.     

Bi3In4S10 and Bi14.7In11.3S38: Two new bismuth sulfides with interesting Bi-Bi bonding

Two new ternary bismuth chalcogenides, Bi₃In₄S₁₀ and Bi_14.7In_11.3S₃₈, were synthesized from the reactions of binary sulfides via a two-step flux technique. Single-crystal X-ray diffraction analyses indicate that Bi₃In₄S₁₀ crystallizes in the non-centrosymmetric space group Pm and Bi_14.7In_11.3S₃₈ crystallizes in the centrosymmetric space group P2₁/m. Both compounds adopt three-dimensional frameworks. A distinct structural feature in the two structures is the presence of chains of Bi atoms with alternating short Bi-Bi bonds of around 3.1 Å and longer distances of around 4.6 Å. The optical band gaps of 1.42(2) eV for Bi₃In₄S₁₀ and 1.45(2) eV for Bi_14.7In_11.3S₃₈ were deduced from the diffuse reflectance spectra.     

A novel extended architecture with 4·6 topology based on mixed-valence Wells-Dawson arsenotungstate and mixed-ligand Cu(I) units

A novel inorganic-organic hybrid compound based on mixed-valence Wells-Dawson arsenotungstate and mixed-ligand Cu(I) units, Cu₈^I(imi)₄(bpy)₆(H₂O)[As₂^VW₂^VW₁₆^VlO₆₂]·2H₂O (1) (bpy=4,4′-bipydine; imi=imidazole), has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, luminescent spectrum and single crystal X-ray diffraction. Single-crystal X-ray diffraction revealed that four terminal and three bridging oxygen atoms of the Wells-Dawson cluster are coordinated to Cu(I) ions and form an unprecedented hepta-supporting polyoxometalate. The functionalized arsenotungstates are further connected by two kinds of tridentate linkers, Imi-Cu-(bpy)-Cu-(bpy)-Cu-(bpy)-Cu-Imi and Imi-Cu-(bpy)-Cu-(bpy)-Cu-H₂O, to construct a 3D framework with 4⁶·6⁴ topology. The hybrid material has an intense emission at about 397 nm.     

KBiMS4 (M=Si, Ge): Synthesis, structure, and electronic structure

Two new bismuth sulfides KBiSiS₄ and KBiGeS₄ have been synthesized by means of the reactive flux method. They adopt the RbBiSiS₄ structure type and crystallize in space group P2₁/c of the monoclinic system. The structure consists of (M=Si, Ge) layers separated by bicapped trigonal-prismatically coordinated K atoms. The M atom is tetrahedrally coordinated to four S atoms and the Bi atom is coordinated to a distorted monocapped trigonal prism of seven S atoms. The optical band gap of 2.25(2) eV for KBiSiS₄ was deduced from the diffuse reflectance spectrum. From a band structure calculation, the optical absorption for KBiSiS₄ originates from the layer. The Si 3p orbitals, Bi 6p orbitals, and S 3p orbitals are highly hybridized near the Fermi level. The orbitals of K have no contributions on both the upper of valence band and the bottom of conduction band.     

Microwave hydrothermal synthesis and photocatalytic activity of AgIn5S8 for the degradation of dye

AgIn₅S₈ powders were successfully synthesized by a microwave hydrothermal method for the first time. This method is a mild and highly efficient route involves no templates, catalysts, or surfactants. Therefore, it is very promising for the low-cost and large-scale industrial production. The samples were characterized by X-ray diffraction, UV-vis spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The photocatalytic activity of AgIn₅S₈ nanoparticles was investigated through the degradation of methyl orange under visible light irradiation. Compared with TiO_2−xN_x, AgIn₅S₈ has exhibited a superior activity under the same condition. A liquid chromatogram-mass spectrometer was used to separate and identify the dye and degradation products generated during the reaction. According to the experiment results, a possible mechanism for the degradation of organic pollutant over AgIn₅S₈ was proposed.