Development of determination method of trace nickel in natural water by ID-oxygen added nitrogen-MIP-MS with direct measurement of liquid–liquid extracted organic phase

This work introduces the development of a novel determination method of trace nickel (ng l^–1 level) in natural water samples. Nickel in the water samples is liquid–liquid extracted into methyl isobutyl ketone (MIBK) as nickel-diethyldithiocarbamate (DDTC) complex, and isotope dilution-oxygen added nitrogen-microwave induced plasma mass spectrometry (ID-oxygen added nitrogen-MIP-MS) is conducted by direct measurement of the liquid–liquid extracted organic MIBK phase. The accuracy of the proposed method was confirmed by analysing certified reference materials (NRC NASS-5 seawater, NRC SLRS-3 riverine water and NRC SLRS-4 river water), and the analytical results obtained were in good agreement with the certified values. The detection limit for nickel is 1.3?ng?l^?1 when the water sample is 50 times concentrated. The precision as RSD is <4%. The proposed method was applied to clarify the concentration-depth vertical profiles of nickel in Lake Mashu, Japan, as the Baseline Station of the United Nations GEMS/Water (Global Environment Monitoring System/Water) Programme.     

Abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds to initiate radical and cationic photopolymerizations

This study explored the abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds, which absorb long‐wavelength light (>350 nm), to photochemically initiate radical and cationic polymerizations. It was found that the irradiation of the title compounds initiates the radical polymerization of styrene whereas the cationic polymerization of oxetane proceeds in the presence of these photoinitiators to a negligible extent. The behavior of 9‐anthrylmethyloxyl and amidyl radicals in the photopolymerization process of styrene was discussed based on ¹H NMR, UV, and fluorescence spectral data. In addition, the photoinitiation ability of the anthrylmethyloxyl end group was also investigated by using its model compound. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2859–2865, 2004     

Preparation and block copolymerization of oligodihexanoylchitin having hydroxy groups at both ends

The preparation of oligodihexanoylchitin (3) having hydroxy groups at the both ends was carried out by an acid hydrolysis of a parent dihexanoylchitin in a mixed solution of acetic acid and conc. hydrochloric acid (11 : 1 in volume) at a room temperature. After 13–21 h, the products were isolated and their molecular weights were calculated as 7400–1100 by GPC analyses. The structure of the product 3 was determined by ¹H and ¹³C-NMR and IR spectra. The IR spectra of the products yielded for longer hydrolysis times than 30 h, however, indicated the occurrence of the dehexanoylation. The block copolymerization of 3 with poly (propylene glycol) (PPG) using 4,4'-methylenedi (phenyl isocyanate) (MDI) as a coupling reagent gave the block copolymer 6 . The molecular weight of 6 as obrained by GPC was 52,000. © 1994 John Wiley & Sons, Inc.     

New surface-modified zinc oxide nanoparticles with aminotriethylene oxide chains linked by 1,2,3-triazole ring: Preparation, and visible light-emitting and noncytotoxic properties

Novel surface-modified, visible light-emitting and noncytotoxic ZnO nanoparticles (NPs) (ZPAZ) having aminotriethylene oxide chains linked by 1,4- and/or 1,5-disubstituted 1,2,3-triazole rings were prepared from ZnO NPs (ZPA) with ethynyl groups on the surfaces and an azide derivative of triethylene oxide chain linking terminal amino group (ATA) via 1,3-dipolar azide/alkyne click reaction by heating without Cu(I) catalyst. FTIR spectroscopy, elemental analysis, XRD analysis and TEM observation suggested that the resulting ZPA and ZPAZ NPs have the particle sizes below 10 nm in diameters, triethylene oxide chains linking the terminal amino groups and wurtzite crystal structure. UV-vis absorption spectrum of the ZPAZ NPs in methanol showed maximum absorption band at 346.5 nm, supporting the TEM observation. PL spectra depicted that the ZPA and ZPAZ NPs display broad light green and lightly greenish yellow visible light emitting bands in methanol. Zeta potentials measured in distilled water suggested that the ZPAZ NPs have a low tendency to aggregate and possess better stability than the ZPA NPs. Cytotoxicity assay revealed that the ZPAZ NPs, having water-dispersion properties, are noncytotoxic at low concentrations and almost all RAW264.7 cells are alive after 24 h of treatment.     

Redispersion of dried gold nanorods in the presence of 6-amino-1-hexanethiol hydrochloride

Aggregates of phosphatidylcholine-passivated gold nanorods were prepared by the addition of hydrochloric acid in the presence of 6-amino-1-hexanethiol hydrochloride (AHT). The aggregates dried in vacuum formed a solid film showing a metallic gold color. In spite of the absence of the stable surface-wrapping agents, such as balky polymer or thiol-molecules that form stable self-organized films on a gold surface, the dried aggregates dispersed again in water. The redispersed gold nanorods in water did not form aggregates. If the dried nanorods were kept at room temperature for 24 h, they did not disperse in water again; however, at –30 °C, some of gold nanorods could be redispersed in water. At –80 °C, gold nanorods could be redispersed in water as colloidal nanoparticles even after 2 months. The phosphatidylcholine and AHT molecules on the nanorod surfaces contributed to the suppression of the contact of nanorods, which were in the metallic gold color films.     

Highly phosphorescent crystals of vaulted trans-bis(salicylaldiminato)platinum(II) complexes

Unprecedented strong phosphorescent emission in the crystalline state is observed for a variety of vaulted trans-bis(salicylaldiminato)platinum(II) complexes which are newly synthesized as a third coordination mode of well-studied bis(salicylaldiminato) complexes. This Communication describes the dynamic photophysical properties of these complexes in the liquid and crystalline states and a mechanistic rationale for the strong emission in the crystalline state.     

Determination of azide in gastric fluid and urine by flow-injection electrospray ionization tandem mass spectrometry

A rapid method was developed to identify and quantify the azide ion (N(3)(-)) in gastric fluid and urine. N(3)(-) in diluted biological fluids was reacted with NaAuCl(4) to produce Au(N(3))(2)(-), which was extracted with octanol. Five microliters of the extract were flow-injected into an electrospray ionization tandem mass spectrometric instrument. Quantification of N(3)(-) was performed by selected reaction monitoring of the product ion Au(N)(N(3))(-) at m/z 253, which was derived from the precursor ion Au(N(3))(2)(-) at m/z 281, using 50 μL of aqueous solution within 10 min. This method was found to be linear up to 10(-5) M, to have a limit of quantification of 10(-7) M, a limit of detection of 3.0?×?10(-8) M, and a coefficient of variation of ≦10% at 10(-7) M. In the case of urine, 50 μL of urine were spiked with N(3)(-), this was diluted 10-fold and passed through 1 mL of a resin, and finally diluted to 100-fold of the original. This method was linear up to 10(-3) M, had a limit of quantification of 10(-5) M, a limit of detection of 3.0?×?10(-6) M, and coefficient of variation of ≦8.8% for an original urine concentration of 10(-5) M. The practical applicability of this method was checked by diluting 1 μL of a suspected suicide victim's gastric fluid 20,000-fold and 1 μL of the victim's urine 5,000-fold and then measuring the N(3)(-) levels. These levels were found to be (7.5?±?1.0)?×?10(-2) M and (3.2?±?0.4)?×?10(-3) M, respectively.     

Asymptotics for a nonlinear integral equation with a generalized heat kernel

This paper is concerned with a nonlinear integral equation $$(P)\qquad u(x, t)=\int_{{\bf R}^N}G(x-y, t)\varphi(y){d}y+\int_0^t \int_{{\bf R}^N}G(x-y, t-s)f(y, s:u){d}y{d}s, \quad $$ where N ≥  1, \({\varphi \in L^\infty({\bf R}^N) \cap L^1({\bf R}^N,(1+|x|^K){d}x)}\) for some K ≥  0. Here, G = G(x,t) is a generalization of the heat kernel. We are interested in the asymptotic expansions of the solution of (P) behaving like a multiple of the integral kernel G as \({t \to \infty}\) .     

Production of nanofibers by electrospinning under pressurized CO2

Electrospinning is one of the simple technical methods for the production of polymer nanoparticles and nanofibers. Various polymers have been successfully electrospun into ultrafine particles and fibers in recent years mostly in solvent solution and some in melt form. In this work, near- and supercritical CO₂ were used as media for this process. At these conditions, the solubility can be tuned by controlling the temperature and pressure. Therefore, it is possible to form particles and fibers within a thermodynamic window where the biopolymer has been softened, but not dissolved. The experiments were conducted by using electrospinning under pressurized CO₂ system at pressures of ～ 8.0 MPa and temperature of 313 K to produce several polymers fibers. Polyvinylpyrrolidone was used as the starting material. During the electrospinning process, the applied voltage was 10–17 kV and the distance of nozzle and collector was 8 cm. The concentration of polymer solution was 4 wt%. The morphology- and structure-produced fibers were observed by scanning electron microscopy. The results showed that temperature and pressure affected the morphology of fibers produced by electrospinning in pressurized CO₂. This suggests that the thermal behavior of the polymer can be optimized by adjusting the polymer through the adjustment of pressure and temperature by using CO₂ as a solvent.