Effect of alkali metal oxides on upconversion fluorescence properties of germanatetellurite glasses

Upconversion emissions of Yb^3 /Er^3 -codoped germanate-tellurite glasses have been investigated upon the excitation of 980 nm laser diode (LD). It is found that upconversion luminescence intensities significantly increase with the increasing size of alkali metal ions. Raman spectra show that the maximum phonon energies (MPE) of glass hosts are unchanged with the replacement of alkali metal oxides, indicating that MPE is not the reason for the increase of upconversion fluorescence intensities. The analysis of the non-radiative transition of Er^3 demonstrates that the decrease of the maximum energy phonon density is the main reason for the enhanced fluorescence intensities.     

Hydroxylated graphene quantum dots as fluorescent probes for sensitive detection of metal ions

Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater. Here, we developed a new probe for the determination of metal ions by fluorescence quenching. The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation. It is a non-reactive indicator with high sensitivity and detection limits of 0.01 μM for Cu~(2+), 0.005 μM for Al~(3+), 0.04 μM for Fe~(3+), and 0.02 μM for Cr~(3+). In addition, the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.     

羟基化石墨烯量子点作为灵敏检测金属离子的荧光探针

Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater. Here, we developed a new probe for the determination of metal ions by fluorescence quenching. The probe consists of hydroxylated graphene quantum dots (H-GQDs), prepared from GQDs by electrochemical method followed by surface hydroxylation. It is a non-reactive indicator with high sensitivity and detection limits of 0.01 μM for Cu2+, 0.005 μM for Al3+, 0.04 μM for Fe3+, and 0.02 μM for Cr3+. In addition, the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.     

Carbazole—containing light—emitting polymers：Properties of excited states

A series of light-emitting conjugated polymers alternatively involving carbazole and bivinylene arylene moieties in the main chain were synthesized via Wit-tig-Horner type copolymerization.The photoinduced charge transfer process relating to these polymers was investigated by using the technique of fluorescence spectroscopy.The interaction between excited copolymers and C60 in benzene solution was studied.The fluorescence quenching can be well described by the “sphere-of-action” mechanism.It is be-lieved that two basic steps are involved in the quenching process,i.e. the diffusion of excitation within the comjugated polymers and the dissociation of the exctions trapped by fullerene,The radius of the sphere-of-action can be related to the excitation diffusion length,which depends on the lifetime of the exciton.The dynamic fluorescence quenching of the copolymers by another quencher,1,4-dicyanobenzene(DCB) was also surveyed.Copolymers with different chain confor-mations show different temperature effects in the dynamic quenching.A planar conformation is beneficial for the quenching via bimolecular collision.     

A Rhodamine-Based Sensor-for Chromogenic Detection of Cu^2＋ and Fluorescent Detection of Fe^3＋

A rhodamine-benzimidazole conjugate(RB) as a probe was investigated.UV-Vis analysis showed that a strong absorption band at 552 nm was formed with the addition of Cu~(2+),while other transition metal ions induced a little more absorption.The absorption value of RB solution at 552 nm has a linear correlation with Cu~(2+) concentration between 35-70 μmol/L;the detection limit reached 6.82×10~(-2) μmol/L,which is lower than the settled limitation for copper in the drinking water(~30 μmol/L) standardized by World Health Organization(WHO).Moreover,FL analysis showed that only Fe~(3+) could induce large fluorescence intensity enhancement at 582 nm;other common metal ions including Cu~(2+) cannot induce the enhancement.There was a good linear correlation between relative fluorescence intensity and Fe~(3+) concentration ranging from 2 μmol/L to 20 μmol/L,and the detection limit reached1.70×10~(-2) μmol/L.The results showed that RB could detect Cu~(2+)and Fe~(3+) simultaneously,with the UV-Vis and fluorescence spectroscopy,respectively.     

Chelators effect on soil Cu extractability and uptake by Elsholtzia splendens

Phytoremediation is emerging as a potential cost-effective solution for remediation of contaminated soils, and bioavailability of metal in the soil for plant uptake is an important factor for successful phytoremediation.This study aimedat investigating the ability of EDTA and citric acid for enhancing soil bioavailability of Cu and phytoremediation by E1sholtzia splendens in two types of soils contaminated with heavy metals [i.e. mined soil from copper mining area (MS), and paddy soil (PS) polluted by copper refining].The results showed that addition of 2.5 mmol/kg EDTA significantly increased the H2O extractable Cu concentration from 1.20 to 15.78mg/kg in MS and from 0.26 to 15.72mg/kg in PS,and that shoot Cu concentration increased 4-fold and 8-fold as compared to the control.There was no significant difference between the treatment with 5.0mmol/kg EDTA and that with 2.5mmol/kg EDTA, probably because that 2.5mmol/kg EDTA was enough for elevating Cu bioavailability to the maximum level.As compared with the control, citric acid had no marked effect on both soil extractable Cu and shoot Cu concentration or accumulation. The results indicated that EDTA addition can increase the potential and efficiency of Cu phytoextraction by E.splendens in polluted soils.     

A specific fluorescent chemosensor for copper(Ⅱ) cation recognition

The fluorescent spectra of 2, 6-bis(benzimidazol-2-yl) pyridine (compound 2) and its N-substituted compound (1) are studied. The fluorescent characteristics of these compounds and the complexes formed from these compounds with different metal ions have also been investigated. The results show that compound 1 possesses a specific ability to form complex with Cu2+ ions, but compound 2 has not such a property. It is proposed that the specific recognition ability of compound 1 to Cu2+ may attribute to the cyclic configuration of this compound in polar solvent.     

Macrocyclic compound as ionophores in lead（Ⅱ） ion-selective electrodes with excellent response characteristics

Macrocyclic compounds, such as crown ethers, azacrown ethers, thiacrown ethers, calixarenes and porphyrins, which act as ionophores in lead（Ⅱ） ion-selective electrodes, are systematically summarized based on the latest literatures. The molecular structure characteristics of the ionophores are generalized. The modification regulations for the substituted ionophores are elaborated with the purpose of improving the response features of the lead（Ⅱ） ion-selective electrodes assembled by them. It is pointed out that the introduction of pendant moieties which contain soft base coordination centers like N, S and P atoms is in favor of adjusting the cavity size and conformation of the macrocyclic com- pounds. Furthermore, there is synergic effect between the cavity and the donor sites of the ligand and thus the selective complexation of lead ions is easily realized, resulting in significant avoidance of the interference from other metal ions. The macrocyclic ionophore having the best response characteristics thus far was found to be N,N＇-dimethylcyanodiaza-18-crown-6 with the detection limit of 7.0×10^8 （14.5 μg/L）, which is one of the uncommon ionophores that can really eliminate the interference from silver and mercury ions. The selectivity coefficients of the ionophore for lead ions over other metal ions, such as alkali, alkaline earth and transition metal ions are in the order of 10^-4 or smaller, where the selectivity coefficient of lead（Ⅱ） over mercury（Ⅱ） ions is much lower, down to 8.9×10^4, The structure design idea for high-performance ionophore is proposed according to present results. The incorporation of nitrogen atom, especially cyano group or thiocyano group or amino/imino groups, rather than thio atom alone could result in new excellent lead ionophores. The aborative design for metacyclophanes containing aromatic nitrogen atoms with the aim of creating excellent ionophores would also become a potential research trend. The lead（Ⅱ） ion-selective electrodes have shown wid     

Fluorescence Spectral Study on the Rhodamine B- I3^- Association Nanoparticle System and Its Analytical Applications

In acid medium, rhodamine B（RhB）, rhodamine S（RhS）, rhodamine 6G（RhG） and butyl rhodamine B（b-RhB） have a fluorescence peak at 580, 549, 553 and 580nm, respectively. BrO^-3 oxidizes excess I^- into I^-3 Rhodamine dyes combine I^-3 to form ion association nanoparticles, resulting in fluorescence quenching at 580, 549, 553 and 580 rim, respectively. The fluorescence quenching intensity is proportional to the concentration of BrO^-3 in the range of 0.020 4 - 0.710 μg/mL for RhB, 0.025 - 0. 512μg/mL for RhS, 0.025 - 0.260 μg/mL for RhG, 0.025 - 1.28μg/mL for b-RhB, respectively. In the four systems, RhB system has good stability and high sensitivity. Thus, a simple, sensitive fluorescence method was proposed for the determination of BrO^-3 in commercial bread additives and flours, with satisfactory results. The results of the fluorescence spectra and scan electron microscopy show that the formation of about 60 ran （RhB - I^-3） n association nanoparticles and the interface between the nanoparticles and solution are main factors that cause the fluorescence quenching.     

Fluorescence study on the interactions of PAMAM dendrimers and their derivatives with bovine serum albumin

The interactions of amino-terminated, and ethylenediamine core poly（amidoamine） （PAMAM） dendrimers and their derivatives with bovine serum albumin （BSA） were investigated by fluorescence spectroscopy. Experimental results showed that the fluorescence intensity of BSA decreased after the addition of different modified dendrimers, and the extent of the fluorescence quenching caused by various modified dendrimers strongly depends upon the different functional groups on their surfaces. We also investigated the influence of pH and ionic strength on the interaction between various modified dendrimers and BSA. Circular dichroism （CD） spectroscopic measurements showed that the content of α-helix structure of BSA decreased after the addition of different modified dendrimers, which indicated that dendrimers induced changes in the secondary structure of BSA.     

Macrocyclic compound as ionophores in lead(Ⅱ) ion-selective electrodes with excellent response characteristics

Macrocyclic compounds,such as crown ethers,azacrown ethers,thiacrown ethers,calixarenes and porphyrins,which act as ionophores in lead(Ⅱ) ion-selective electrodes,are systematically summarized based on the latest literatures.The molecular structure characteristics of the ionophores are general-ized.The modification regulations for the substituted ionophores are elaborated with the purpose of improving the response features of the lead(Ⅱ) ion-selective electrodes assembled by them.It is pointed out that the introduction of pendant moieties which contain soft base coordination centers like N,S and P atoms is in favor of adjusting the cavity size and conformation of the macrocyclic com-pounds.Furthermore,there is synergic effect between the cavity and the donor sites of the ligand and thus the selective complexation of lead ions is easily realized,resulting in significant avoidance of the interference from other metal ions.The macrocyclic ionophore having the best response characteris-tics thus far was found to be N,N'-dimethylcyanodiaza-18-crown-6 with the detection limit of 7.0×10-8(14.5 μg/L),which is one of the uncommon ionophores that can really eliminate the interference from silver and mercury ions.The selectivity coefficients of the ionophore for lead ions over other metal ions,such as alkali,alkaline earth and transition metal ions are in the order of 10-4 or smaller,where the se-lectivity coefficient of lead(Ⅱ) over mercury(Ⅱ) ions is much lower,down to 8.9×10-4.The structure de-sign idea for high-performance ionophore is proposed according to present results.The incorporation of nitrogen atom,especially cyano group or thiocyano group or amino/imino groups,rather than thio atom alone could result in new excellent lead ionophores.The aborative design for metacyclophanes containing aromatic nitrogen atoms with the aim of creating excellent ionophores would also become a potential research trend.The lead(Ⅱ) ion-selective electrodes have shown widely potential applications in the potentiometric titration,and flow injection potentiometry,and in the direct determination of lead in stack emissions of lead smelters,and assay of lead in rocks,particularly in the direct measurements of trace amount of lead(Ⅱ) in human hair,blood,edible oil,food,water,and air.     

EAF steelmaking process with increasing hot metal charging ratio and improving slagging regime

A new electric arc furnace (EAF) steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a year at No. 1 Steelmaking Plant of Shanxi Taigang Stainless Corporation Limited. The essential fact of the new EAF steelmaking process was to charge hot metal in two portions or steps: firstly, 35wt%-40wt% hot metal was pretreated by blowing oxygen in a specially designed reactor for decar burization and improving hot metal temperature and melting premelted slag; secondly, 30wt% hot metal was charged into EAF with high basicity refining slags from ladle furnace (LF)-vacuum degassing furnace (VD) refining process. The results show that the hot metal charging ratio can reach to about 65wt%-70wt% for the new EAF steelrnaking process; meanwhile, the tap-to-tap time of a 50 t EAF can shorten by 5-10 min, the electricity consumption can decrease by 35-50 kW·h/t, the lime consumption can reduce by 10.5 kg/t of molten steel, and the content of harmful heavy metals in molten steel can be easily controlled to less than the upper limits of aimed steel specification or grade compared with the traditional EAF steelmaking process. In addition, the dephosphorization ability shows a slight strengthening, however, a small degree of lessening for desulphurization ability is observed for the new EAF steelmaking process, but the weakness of desulphurization ability cannot become an obstacle to its further application since a stronger desulphurization ability can be achieved during secondary refining of LF coupled with VD after EAF steelmaking process.     

Graphene-reinforced aluminum matrix composites prepared by spark plasma sintering

Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering (SPS). The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide (Al₄C₃) is not formed during SPS processing. Further addition of graphene (above 1wt%) results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.     

New Voronoi Diagram Algorithm of Multiply-Connected Planar Areas in the Selective Laser Melting

This paper studies the practical generation of Voronoi diagrams for multiply-connected planar areas bounded by line segments. The core of the algorithm was calculating Voronoi polygon of every Voronoi object in planar areas independently. The main approach had two steps. The first step was calculating all relevant bisectors of every Voronoi object. The second was combining obtained bisectors into completed Voronoi polygons individually. All code was implemented in Visual C++ platform. The resulting code was extensively tested in real-world data and its practical running time grew only linearly. Three statistical CPU-consumption charts had been drawn with the Voronoi diagrams computation data, and compared with other published codes for computing Voronoi diagrams. The algorithm was applied to compute offsetting of slice area consisting of large-scale line segments for the selective laser melting (SLM) trajectory scanning technology which is a kind of rapid prototyping (RP). The experimental results of offsetting for slice area based on Voronoi diagrams show that the approach is effective and simple for polygon offsetting problems. The method is helpful to those offsetting work and can provide more effective offsetting solution.     

Synthesis of Conjugated Polymers for Light Emitting and Photovoltalc Applications

1 Results The initial report of polymeric light-emitting diodes (PLEDs) based on poly(p-phenylenevinylene) gave birth to an intense research effort in conjugated polymers, primarily focused on the development of optoelectronic and electrochemical devices. Significant developments in modern synthetic chemistry, especially the chemistry of carbon-carbon bond formation have allowed the synthesis of various well-defined conjugated polymers and oligomers with optimized physical properties.Meanwhile, these reactions normally require a transition metal catalyst, which results in a problem in materials purification that is harmful to materials physical properties. On the other hand, Wittig and Knovenagel condensations are also famous reactions for the formation of carbon-carbon double bond, which can proceed without a transition metal catalyst.     

Influence and determinative factors of ion-to-atom arrival ratio in unbalanced magnetron sputtering systems

Low pressure sputtering with a controlled ratio of ion flux to deposited atom flux at the condensing surface is one of the main directions of development of magnetron sputtering methods. Unbalanced magnetron sputtering, by producing dense secondary plasma around the substrate, provides a high ion current density. The closed-field unbalanced magnetron sputtering system (CFUBMS) has been established as a versatile technique for high-rate deposition high-quality metal, alloy, and ceramic thin films. The'key factor in the CFUBMS system is the ability to transport high ion currents to the substrate, which can enhance the formation of full dense coatings at relatively low value homologous temperature. The investigation shows that the energy of ions incidenced at the substrate and the ratio of the flux of these ions to the flux of condensing atoms are the fundamental parameters in determining the structure and properties of films produced by ion-assisted deposition processes. Increasing ion bombardment during deposition combined with increasing mobility of the condensing atoms favors the formation of a dense microstructure and a smooth surface.     

Syntheses of New Functionalized Monomers for π-Conjugated Polymers

1 Results Tailored monomers based on the activated esters of 2,5-dibromobenzoic (sulfonic) acid derivatives, the 3-substituted 2,5-dibromothiophenes, the 9-substituted 2,7-dibromocarbazoles, and on the brominated 1,10-phenanthrolines suitable for Suzuki, Yamamoto or Grignard metathesis (GRIM) coupling reactions were synthesized and characterized by melting point, elemental analysis, 1H NMR, FTIR and TLC. The Horner-Wadsworth-Emmons reaction mechanism was utilized for the preparation of the 3-[2-(pyren-1-yl)vinyl]- or 3-[2-(quinolin-1-yl)vinyl]-2,5-dibromothiophenes. 4-Nitrophenol or N-hydroxysuccinimide were used for the preparation of activated esters. The Cadogan ring closure was utilized for the synthesis of 2,7-dibromocarbazole derivatives. A monomer with β-diketone structure was prepared and characterized as well. 1,10-Phenanthroline (phen) is a typical β-deficient aromatic compound and experience (and literature) advises that simple bromination is poor and nonselective. Of course, bromo derivatives can be obtained by the Skraup synthesis, but the low-yield and multi-step procedure is tedious. There are two main reasonable procedures available at present for the synthesis of 3,8-dibromo-1,10-phenanthroline. The methods utilize either phen monohydrochloride monohydrate for bromination or phen with addition of pyridine and sulfur chloride S2Cl2. We have found in our laboratory that the replacement of sulfur chloride by sulfur dichloride SCl2 and the use of phen monohydrate gives the possibility to prepare 3-bromo-, 3,8-dibromo-, 3,5,8-tribromo- and 3,5,6,8-tetrabromo-1,10-phenanthrolines in reasonable yields, and these derivatives can be separated by crystallization or by column chromatography.     

Form factors for B meson weak decays in QCD light cone sum rules with a chiral current correlator

We report some applications of QCD light cone sum rules （LCSR） to B meson weak decays. Special emphasis is on estimates of the form factors for B decays into a pseudoscalar （P）/vector （V） meson, with a certain chiral current correlator. The main new ingredient, as compared with the case of the standard correlators, is that in the operator product expansion calculations, the contributions due to the twist-3 distribution amplitudes of the related light mesons, which are less known and would bring a larger uncertainty to the calculations with the standard correlators, cancel out fully in the B →P case and do out partially in the B → V one. An important observa- tion, which is similar to that in soft collinear effective theory, is made in twist-3 approximation： whereas only one independent form factor is needed for parameterizing the hadronic matrix elements for a B →P transition induced by all the relevant heavy-light quark currents, there exist two independent form factors under the condition of neglecting the terms suppressed by a factor of m^2, for the B → V transition. Therefore, the improved LCSR approach could be of stronger predictive power for the weak form factors. Also, this approach is employed to understand the B →D transitions by introducing a leading twist-2 DA for an energetic D meson, combined with some of other QCD- based approaches. A detailed QCD next-to-leading order calculation of the B →π form factors is presented for an illustrative purpose, and the sum rule results are used to extract the Cabibbo-Kobayashi-Maskawa matrix element IVubl from the latest BaBar data.     

Thermal residual stress analysis of coated diamond grits

Residual stresses of coated diamond grits were analyzed by a finite element unit cell model. Diamond grits coated with four types of metals, W, Mo, Ti, and Cr, were considered. The numerical results show that compressive stress occurs in the diamond particles and tensile stress occurs in the metal matrix; compressive stress is concentrated in the diamond sharp comer; interface stresses decrease by more than 1000 MPa with a metal interlayer; plastic deformation of the matrix begins near the sharp corner of diamond grits and extends toward the peripheral zone. Stress concentration dramatically decreases due to plastic deformation of the matrix. The deposition of transition metals on a diamond surface can dramatically promote the adhesion between diamond grits and the metal bond.     

A View on Wear Mechanism of Metallic Card Clothing

The wear mechanism of metallic card clothing, used in textile industry, was analyzed. A fast wear test for metallic card clothing racks was developed, which was used as collecting the wear metal particles. The failure type of card clothing was analyzed by the mean of scanning electron microscopy （SEM） and ferro-spectrum technology. The results show that the main wear mechanism of metallic card clothing is low load and high repetition interval fatigue wear caused by friction force between fiber and metal wire teeth. The appropriate quenching microstructure, which improves the wear resistance of the metallic card clothing rack is also discussed.