N2 Protection Research Articles

High-pressure crystallization of poly(lactic acid) with and without N2 atmosphere protection

High-pressure crystallization experiments of poly(lactic acid) (PLA) were conducted under air and N2 atmosphere. Compared with the sharp decrease of the molecular weight of air sample from 1.63 × 105 to 3.11 × 104, the weight loss of N2 protection sample was successfully restricted to the value below 10 %. Stable α-crystals were generated in both air and N2 protection samples which both exhibited very high crystallinity up to 66.3 and 64.5 %, respectively. It is high pressure that leads to the perfect crystalline structure by inducing crystalline reorganization and lamellar thickening. A diffraction streak appeared in the 2D-SAXS pattern of air sample in contrast to the broad scattering signal in N2 protection sample, implying the formation of oriented crystals during PLA degradation. As observed from scanning electron microscopy, the spherulite size of air sample was larger than that of N2 protection sample, for the radius growth rate of PLA crystals increased as molecular weight decreased. Accordingly, N2 atmosphere protection can not only effectively prevent PLA from degradation, but also acquire highly crystallized PLA.

Sonoelectrochemical synthesis of water-soluble CdTe quantum dots

A facile and fast one-pot method has been developed for the synthesis of CdTe quantum dots (QDs) in aqueous phase by a sonoelectrochemical route without the protection of N2. The morphology, structure and composition of the as-prepared products were investigated by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDS). The influences of current intensity, current pulse width, and reaction temperature on the photoluminescence (PL) and quantum yield (QY) of the products were studied. The experimental results showed that the water-soluble CdTe QDs with high PL qualities can be conveniently synthesized without precursor preparation and N2 protection, and the PL emission wavelength and QY can be effectively controlled by adjusting some parameters. This method can be expected to prepare other QDs as promising building blocks in solar cell, photocatalysis and sensors.

Functions of surfactants in the one-step synthesis of surfactant-intercalated LDHs

Surfactant-intercalated Zn and Al layered double hydroxides (ZnAl-LDHs) were synthesized via spontaneous self-assembly of the surfactants (sodium dodecyl sulfate and sodium dodecyl benzene sulfonate) and the LDH salt precursors. To understand the function of the surfactants in the synthesis, the surfactant-modified ZnAl-LDHs and their intermediates before aging were characterized via X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, and thermogravimetric analysis. In addition, fluorescence spectroscopy was used to in situ trace the microenvironmental variations of the reactants in the synthesis. It was found that the anionic surfactants can interact with the LDH precursors to form cooperative micellar assemblies, which increase the concentration of cationic counter ions around the micelles leading to enhanced growth of the LDH sheets along their lamellar surface direction and the stacking of LDH sheets into nanoparticles as the surfactant possesses longer molecular length. Because of the hydrophobicity of the intermediate sheets coated with surfactants, the reaction between the dissolved CO32− and the LDH intermediate sheets can be greatly reduced, and thus no strict N2 protection was necessary in this method. This mechanistic understanding of the effects of the surfactants on the formation of LDHs is critical in successful synthesis of organic-intercalated LDHs in complicated system by void the interruption of competitive ions.

Effect of nitrogen-doped acetylene carbon black supported Pd nanocatalyst on formic acid electrooxidation

Nitrogen-doped acetylene carbon black (N-C) is prepared by annealing acetylene carbon black and melamine under the protection of N2 at different temperatures. The resultant N-C materials are used as the support of Pd catalyst (Pd/N-C) for formic acid electrooxidation (FAEO). The catalytic activity of the Pd/N-C catalyst towards FAEO is evaluated by cyclic voltammetry, COad stripping voltammetry and chronoamperometry. The results show that when the heat-treatment temperature of support is 900 °C, the corresponding catalyst, Pd/N-C-900, generate 2.84-fold and 0.96-fold higher activity than homemade and commercial Pd/C catalysts in 0.5 M H2SO4 and 0.5 M HCOOH solution. The COad stripping voltammetry results demonstrate that Pd/N-C-900 has much better resistance to CO poisoning. Moreover, the effect of formic acid concentration and the temperature on the Pd/N-C catalysts are also explored, which confirms the really enhanced performances for FAEO. It is founded that the doping of nitrogen results an increase in the performance for FAEO due to the improved Pd nanoparticles (Pd NPs) dispersion and the modified electronic effect. The results indicate that the Pd/N-C catalyst has great application prospect as a high-performance anode catalyst for direct formic acid fuel cells (DFAFCs).

Reactivity characteristics of SiO2-coated zero-valent iron nanoparticles for 2,4-dichlorophenol degradation

Core–shell SiO2-coated iron nanoparticles were synthesized using a one-step Stöber method in the presence and absence of PEG400. The 2,4-dichlorophenol degradation and antioxidation abilities of the nanoparticles were investigated. The effects of isopropanol/H2O ratio, NaOH dosage, tetraethyl orthosilicate (TEOS) dosage, and reaction time used in the synthesis were investigated. The SiO2-coated iron nanoparticles were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The results showed that N2 protection during filtration and drying were unnecessary, and the iron particle preparation was simple. The nanoparticles were stable in the presence of PEG400. The effects of isopropanol/H2O ratio and TEOS dosage on 2,4-dichlorophenol degradation and antioxidation abilities were significant, although the effects of NaOH dosage and reaction time were small. The isopropanol/H2O ratio changed the nanoparticle nucleation process, whereas NaOH dosage, TEOS dosage, and reaction time changed the mesoporous coating structure. A comparison of the removal rates of 2,4-dichlorophenol using pure iron nanoparticles and using SiO2-coated iron nanoparticles showed an improvement of about 30% using SiO2-coated iron nanoparticles, suggesting that SiO2-coated iron nanoparticles improve the antioxidation abilities and reducing capacity of iron nanoparticles; such nanoparticles could have wide applications in chlorophenol degradation.

Electrodeposition of Sb x Te y Thermoelectric Films from Dimethyl Sulfoxide Solution

The electrochemical behaviors of nonaqueous dimethyl sulfoxide solutions containing TeIV and SbIII were investigated using cyclic voltammetry. On this basis, SbxTey thermoelectric films were prepared by the potentiodynamic electrodeposition technique from nonaqueous dimethyl sulfoxide solution, and the composition, morphology, and thermoelectric properties of the films were analyzed. SbxTey thermoelectric films prepared under different potential ranges all possessed smooth morphology. After annealing treatment at 200°C under N2 protection for 4 h, all the deposited films showed p-type semiconductor properties. Sb1.87Te3.13 thermoelectric film, which most closely approached the stoichiometry of Sb2Te3 and possessed the highest Seebeck coefficient, could be potentiodynamically electrodeposited in the potential range of −200 mV to −600 mV.

Synthesis of Continuous Boron Nitride Nanofibers by Electrospinning

Abstract Continuous boron nitride nanofibers (BNNFs) have been gotten by electrospinning. The appropriate precursor of BNNFs was electrospinned to green born nitride nanofibers (GBNNFs) with temperatures from 80°C to 100°C in the protection of N2. By successive heat treatments in N2, the organics in GBNNFs disappeared and BN ceramics nanofibers came into being. The average diameters of BNNFs by electrospinning are less than 10 μm

Facile one-step photochemical synthesis of water soluble CdTe(S) nanocrystals with high quantum yields

This paper describes a successful synthesis of water soluble CdTe(S) nanocrystals (NCs) with high quantum yields (QYs) via a mild photochemical route in one step with thioglycolic acid as the stabilizer and sulfur source. The precursor solution of mixed cadmium chloride, freshly prepared sodium hydrogen telluride and thioglycolic acid was subjected directly to UV irradiation using a 500 W high-pressure mercury lamp under the protection of N2. NCs with a small particle size (2.2 nm) and a high photoluminescence quantum yield (up to 80% at room temperature) were formed within 25 min. The NCs were characterized by UV-vis absorption and fluorescence spectroscopy, transmission electron microscopy, powder X-ray diffraction and energy-dispersive X-ray spectroscopy to evaluate their structure, size and composition. The photochemically prepared NCs were compared with CdTe NCs prepared by conventional hydrothermal synthesis and CdTe/CdS core/shell NCs obtained by post-preparative photochemical passivation. The effects of UV irradiation intensity, illumination time, temperature and concentration of Te2− on the optical properties of NCs were studied in detail.

A simple and economical one-pot method to synthesize high-quality water soluble CdTe QDs

A simple and economical one-pot method to synthesize high-quality water soluble CdTe QDs is reported. An 83% quantum yield (QY) was reached using TGA as the ligand in aqueous solution without protection of nitrogen gas when using K2TeO3 as a stable Te source and NaBH4 as reducing agent. The size of the CdTe NCs could be tuned by the duration of reflux and easily monitored by absorption and PL spectra. At the optimum conditions (pH = 10.5, the concentration of Cd2+ was 1.0 mmol l−1 and the ratio of Cd2+ : Te2− : TGA : NaBH4 was 1 : 0.2 : 1 : 10), the maximal QY reached 83%, which was much higher than that of samples prepared by the traditional refluxing aqueous solution method. The X-ray diffraction (XRD) patterns indicated that CdS was formed in the preparation process of CdTe NCs. This CdS shell could effectively passivate the surface trap states, and enhance the PL QY and stability of the CdTe QDs. The temporal evolution of the absorption spectrum of thioglycolic acid indicated that TGA was decomposed and released S2− during the preparation of CdTe QDs. The S2− reacted with Cd2+ to form CdS, this is consistent with the XRD results. 3-Mercaptopropionic acid (MPA) was also used as a ligand in this system and the results indicate that high quality multi colour CdTe NCs could also be obtained using MPA as the ligand. By this simple method, there is no need of N2 protection, buffering solution, special ligands, large quantity of N2H4 or particular treatment (such as microwave, or ultrasonication).

Simple Synthesis of Highly Luminescent Water-Soluble CdTe Quantum Dots with Controllable Surface Functionality

Highly luminescent quantum dots (QDs) could be synthesized in “conical flask” now. Through a room-temperature N2H4-promoted strategy, water-soluble CdTe QDs were facilely synthesized by a stepwise addition of raw materials in one pot. No prepreparation of precursors, pH adjustment, heating, and even N2 protection were required. Just by adjusting the feed ratio of the reagents, different-sized QDs were easily obtained within a shortened time. More importantly, besides conventional thiol-ligands, such as thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), 1-thioglycerol (TG), 2-mercaptoethylamine (MA), glutathione (GSH), and l-cysteine (LCS), some special mercapto-compounds, for instance, 4-mercaptobenzoic acid (MBA), per-6-thio-α-cyclodextrin (α-CD-SH), and per-7-thio-β-cyclodextrin (β-CD-SH), were also practicable, which were impossible in the conventional reflux method because of the poor water-solubility of them. Furthermore, a spontaneous aggregation of MA-stabilized QDs was observed after synthesis, which facilitated the separation of QDs and recycle of N2H4-containing growth solution.

Involvement of Cytoskeleton-associated Proteins in the Commitment of C3H10T1/2 Pluripotent Stem Cells to Adipocyte Lineage Induced by BMP2/4

The developmental pathway that gives rise to mature adipocytes involves two distinct stages: commitment and terminal differentiation. Although the important proteins/factors contributing to terminal adipocyte differentiation have been well defined, the proteins/factors in the commitment of mesenchymal stem cells to the adipocyte lineage cells have not. In this study, we applied proteomics analysis profiling to characterize differences between uncommitted C3H10T1/2 pluripotent stem cells and those that have been committed to the adipocyte lineage by BMP4 or BMP2 with the goal to identify such proteins/factors and to understand the molecular mechanisms that govern the earliest stages of adipocyte lineage commitment. Eight proteins were found to be up-regulated by BMP2, and 27 proteins were up-regulated by BMP4, whereas five unique proteins were up-regulated at least 10-fold by both BMP2/4, including three cytoskeleton-associated proteins (i.e. lysyl oxidase (LOX), translationally controlled tumor protein 1 (TPT1), and αB-crystallin). Western blotting further confirmed the induction of the expression of these cytoskeleton-associated proteins in the committed C3H10T1/2 induced by BMP2/4. Importantly, knockdown of LOX expression totally prevented the commitment, whereas knockdown of TPT1 and αB-crystallin expression partially inhibited the commitment. Several published reports suggest that cell shape can influence the differentiation of partially committed precursors of adipocytes, osteoblasts, and chondrocytes. We observed a dramatic change of cell shape during the commitment process, and we showed that knockdown of these cytoskeleton-associated proteins prevented the cell shape change and restored F-actin organization into stress fibers and inhibited the commitment to the adipocyte lineage. Our studies indicate that these differentially expressed cytoskeleton-associate proteins might determine the fate of mesenchymal stem cells to commit to the adipocyte lineage through cell shape regulation.

Synthesis of Conducting Polyaniline Using Compound Oxidant

Conductive polyaniline (PANI) was synthesized by the oxidation of aniline with complex oxidant composed of ammonium persulfate ((NH4)2S2O8) and ascorbic acid (C6H8O6) in a reaction media containing sulfuric acid (H2SO4). The effects of concentration of H2SO4, (NH4)2S2O8 and (NH4)2S2O8/C6H8O6 mol ratio on the polymerization of aniline were studied. The optimal polymerization condition was aniline 1mol/L, H2SO4 1mol/L, and compound oxidant (mole ratio of (NH4)2S2O8 to C6H8O6 as to 10:1) 1mol/L at room temperature without the protection of N2. The conductivity and yield of PANI reach 13.3S/cm and 96.7%, respectively. The structural changes of PANI were measured by FTIR, Raman and XRD. The results indicated that PANI was some crystal and its groups took place red shift.

Synthesis of monodisperse styrene/methyl methacrylate/acrylic acid latex using surfactant‐free emulsion copolymerization in air

AbstractMonodisperse styrene/methyl methacrylate/acrylic acid (St/MMA/AA) copolymer microspheres have been prepared with surfactant‐free emulsion polymerization in air. The presence of oxygen in the system not only caused an induction period but also decreased the average particle size (Dp). However increasing AA concentration ([AA]) gave a reduction in the induction period. The FTIR and NMR analysis of the latex copolymer confirmed that the correlation of the copolymer compositions with the feed compositions was much better at the lower [AA] than at the higher levels. The AA contents of the copolymers obtained in air were much lower than those of the copolymers obtained under N2 protection. Decreasing [AA] led to decrease in the copolymer molecular weight and broadening of the molecular weight distribution, but the particle size distribution (δ/Dp) was unaffected. In addition, the average particle diameter (Dp) was proportional to [AA]–0.255, and increasing comonomers feed content caused linear increase of Dp, and a monodisperse sample with final solids contents up to 34.2 wt % was obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Enhancement of visible photoluminescence in the SiNx films by SiO2 buffer and annealing

The authors report a simple method to significantly enhance the photoluminescence (PL) of SiNx films by incorporating a SiO2 buffer and annealing treatment under N2 protection. Strong visible PL is achieved with annealing temperature above 650°C. Optimal PL is obtained at 800°C. The composition and structure analysis reveal that strong PL is directly related to the content of the Si–O and Si–N bonds in the SiNx films. These bonds provide effective luminescent centers and passivate the interface between Si core and the surrounding oxide.

Ce(IV)‐induced graft copolymerization of methacrylic acid on electrospun polysulphone nonwoven fiber membrane

AbstractCe(IV)‐induced graft copolymerization of methacrylic acid (MAA) on polysulphone (PSU) surface is studied. After pretreatment either by formaldehyde solution or by air glow discharge plasma, the PSU fiber membrane was immersed in MAA solution with Ce(IV) and heated under 80°C under N2 protection. The MAA was induced by the Ce(IV) redox initiation system to polymerize on the PSU fiber membrane surface. It was found that the pretreatment of the membrane is a very necessary condition for the graft copolymerization to obtain high graft degree. For both the formaldehyde and the air glow discharge plasma pretreated membrane, the graft degree increase with the reaction time. To study the reaction mechanism, control experiments were carried out. Membrane surfaces were characterized by ATR‐FTIR and XPS. The reaction mechanism of the graft copolymerization was discussed based on the experimental data. The effect of the graft copolymerization on the membrane's structure and water permeability was finally studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3835–3841, 2006

Electronic sensory behavior of titanylphthalocyanine revealed by scanning tunneling spectroscopy and cyclic voltammetry methods

The electronic characteristics of titanylphthalocyanine (TiOPc) were examined by scanning tunneling microscopy and spectroscopy (STM/STS) and electrochemical cyclic voltammetry (CV) methods. The STS spectra of TiOPc molecules acquired under ambient conditions suggest the same semiconducting characteristics as those deduced from the CV results in o-dichlorobenzene (DCB) exposed to air while opposite to those under N2 protection. These results revealed that oxygen doping in air greatly affected the electronic structures of TiOPc molecules in ultra-thin films.

Effects of implant surface microtopography on osteoblast gene expression

The promotion of osteoblast attachment and differentiation has been evaluated on various implant surfaces. However, the effects of different implant surface properties on gene expression of key osteogenic factors are not fully understood. The objectives of this study were to evaluate how topographical effects on titanium surface alter the expression of bone-related genes and transcription factors. Osteoblasts were cultured on titanium disks prepared with a titanium dioxide grit blasting (TiOBlast) or grit blasted and etched with hydrofluoric acid (Osseospeed), grit blasted and etched (SLA-1), or grit blasted, etched and rinsed with N2 protection and stored in isotonic NaCl (SLA-2) commercially pure titanium implant discs. High-density cultures of human mesenchymal pre-osteoblastic cells (HEPM 1486, ATCC) were grown for 72 h and real-time PCR used for quantitative analysis of alkaline phosphatase (ALP), core-binding factor alpha1 (Cbfa1), Osterix, Type I Collagen, Osteocalcin and bone sialoprotein II gene expression. Real-time PCR showed significant (P<0.001) increases in ALP gene expression in osteoblasts grown on SLA-2, relative to all other surfaces. Cbfa1/RUNX-2 gene expression was significantly (P<0.01) increased on Osseospeed and TiOBlast surface as compared with SLA-1 and SLA-2 surfaces. The expression of Osterix had a trend similar to that of Cbfa1. In conclusion, implant surface properties may contribute to the regulation of osteoblast differentiation by influencing the level of bone-related genes and transcription factors in human mesenchymal pre-osteoblastic cells.

1545 POSTER Added value of specific nurse care in a one-stop breast unit

Core–shell SiO2-coated iron nanoparticles were synthesized using a one-step Stöber method in the presence and absence of PEG400. The 2,4-dichlorophenol degradation and antioxidation abilities of the nanoparticles were investigated. The effects of isopropanol/H2O ratio, NaOH dosage, tetraethyl orthosilicate (TEOS) dosage, and reaction time used in the synthesis were investigated. The SiO2-coated iron nanoparticles were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The results showed that N2 protection during filtration and drying were unnecessary, and the iron particle preparation was simple. The nanoparticles were stable in the presence of PEG400. The effects of isopropanol/H2O ratio and TEOS dosage on 2,4-dichlorophenol degradation and antioxidation abilities were significant, although the effects of NaOH dosage and reaction time were small. The isopropanol/H2O ratio changed the nanoparticle nucleation process, whereas NaOH dosage, TEOS dosage, and reaction time changed the mesoporous coating structure. A comparison of the removal rates of 2,4-dichlorophenol using pure iron nanoparticles and using SiO2-coated iron nanoparticles showed an improvement of about 30% using SiO2-coated iron nanoparticles, suggesting that SiO2-coated iron nanoparticles improve the antioxidation abilities and reducing capacity of iron nanoparticles; such nanoparticles could have wide applications in chlorophenol degradation.

Some New Features on Synthesis of Titanium Silicalite-1 in a Non-TPAOH Inorganic Reactant Synthetic System

Various effects on the synthesis of titanium silicalite-1 (TS-1) were discussed in the non-TPAOH (tetrapropyl ammonium hydroxide) inorganic reactant synthesis system, in which cheap colloidal silica and TiCl3 aqueous solution, TiCl4 were used as the silicon and titanium sources, respectively, TPABr (tetrapropyl ammonium bromide) as the template reagent, and weak organic bases as the base source to provide the alkalinity needed for crystallization. The influence of diverse synthesis parameters such as different base sources, SiO2/TiO2 ratio, silicon source, titanium source, amounts of template, N2 protection, seed crystals, aging period, amount of water, crystallization temperature, and crystallization time have been investigated in detail.

Synthesis and antiproliferative activity of 2,6-diamino-9-benzyl-9-deazapurine and related compounds

Treatment of 6-bromomethyl- or 6-dibromomethyl-5-nitropyrimidine-2,4-diamine with KCN gave the same product––(2,6-diamino-5-nitropyrimidinyl)acetonitrile. Benzylation of the nitrile took place on the α-carbon to the cyano group preferentially affording the corresponding mono- and dibenzyl derivative, whose reductive cyclization resulted in 7-benzyl-5H-pyrrolo[3,2-d]pyrimidine-2,4-diamine and 7,7-dibenzyl-7H-pyrrolo[3,2-d]pyrimidine-2,4,6-triamine, respectively. Suitability of the protection of N2 and N4 atoms with benzyl, acetyl, or benzoyl groups was also investigated. The in vitro evaluation of cell growth inhibition on CCRF-CEM, HL-60, HeLa S3, and L1210 cell lines showed significant activity in 8 new compounds. The most potent compounds were the above mentioned 6-dibromomethyl derivative (IC50=0.54, 1.7, 5.0, and 1.9 mol L−1) and 7,N2,N4-tribenzyl-5H-pyrrolo[3,2-d]pyrimidine-2,4-diamine (IC50=1.9, 2.7, 7.3, and 1.0 mol L−1).