STUDIES ON THE EFFECT OF DISSOLVED IONS ON SCO DEPRESSING PROPERTY USING ULTRAVIOLET ABSORPTION SPECTRA

SCO is a selective dolomite deperessant in the flotation system of collophane and dolomite. However,experi-ments confirmed that reverse phenomenon would occur for some phosphatic mines. In order to explain the SCO depress-ing mechanism i this paper describes studying results on the ef-fect of dissolved ions on SCO depressing property using ul-traviolet absorption spectra. It is found that the effect of dis-solved ions, especially Mg2+ ?on the SCO adsorption property is strong. When Mg2+ concentration is low,dolomite adsorbs SCO and is depressed. When Mgz+ concentration is more than 90g/t in pulp.SCO adsorption capacity on colophane is obvi-ously greater than that on dolomite,which results in the de-pression of collophane. The adsorption results are consistent with flotation results.

Synthesis of Ultraviolet Absorption Polylactide via Immortal Polymerization of rac-Lactide Initiated by a Salan-yttrium Catalyst

A highly efficient strategy for the synthesis of polylactide with the UV absorption ability was established by employing a Salan-yttrium complex（acting as a fast runing catalyst） combined with large excess hydroxyl functionalized benzophenone, BP′-OH. During polymerization, BP′-OH, acting as the chain transfer agent, attached to the active rare-earth metal catalyst via a rapid-reversible exchange reaction to initiate the polymerization. Thus, more polyester chains appeared to grow from one active metal species, and the UV absorption fragments were incorporated into the polymer chains at specific sites, in situ. A high productivity up to 1000 mol LA/mol（Salan-Y） was successfully achieved and 100 BP′-labeled PLA chains grew from each active metal center.

Improved Visible Transparency of SiO_2/ZnO:Al/CeO_2-TiO_2/SiO_2 Multilayer Films with High UV Absorption and Infrared Reflection Rate

New visible transparent, UV absorption, and high infrared reflection properties have been realized by depositing multilayer Si O2/Zn O: Al/Ce O2-Ti O2/Si O2 films onto glass substrates at low temperature by radio frequency magnetron sputtering. Optimum thickness of Si O2, Zn O: Al(ZAO) and Ce O2-Ti O2(CTO) films were designed with the aid of thin film design software. The degree of antireflection can be controlled by adjusting the thickness and refractive index. The outer Si O2 film can diminish the interference coloring and increase the transparency; the inner Si O2 film improves the adhesion of the coating on the glass substrate and prevents Ca2+, Na+ in the glass substrate from entering the ZAO film. The average transmittance in the visible light range increases by nearly 18%-20%, as compared to double layer ZAO/CTO films. And the films display high infrared reflection rate of above 75% in the wavelength range of 10-25 μm and good UV absorption(> 98%) properties. These systems are easy to produce on a large scale at low cost and exhibit high mechanical and chemical durability. The triple functional films with high UV absorption, antireflective and high infrared reflection rate will adapt to application in flat panel display and architectural coating glass, automotive glass, with diminishing light pollution as well as decreasing eye fatigue and increasing comfort.

Investigation of the Antioxidant and UV Absorption Properties of 2-(2’-hydroxy-5’-methylphenyl)-benzotriazole and Its Ortho-Substituted Derivatives via DFT/TD-DFT

The demand and pursuit of chemical entities with UV filtration and antioxidant properties for enhanced photoprotection have been driven in recent times by acute exposure of humans to solar ultraviolet radiations. The structural, electronic, antioxidant and UV absorption properties of drometrizole (PBT) and designed ortho-substituted derivatives are reported via DFT and TD-DFT in the gas and aqueous phases. DFT and TD-DFT computations were performed at the M062x-D3Zero/6-311++G(d,p)//B97-3c and PBE0-D3(BJ)/def2-TZVP levels of theory respectively. Reaction enthalpies related to hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were computed and compared with those of phenol. Results show that the presence of -NH2 substituent reduces the O-H bond dissociation enthalpy and ionization potential, while that of -CN increases the proton affinity. The HAT and SPLET mechanisms are the most plausible in the gas and aqueous phases respectively. The molecule with the -NH2 substituent (PBT1) was identified to be the compound with the highest antioxidant activity. The UV spectra of the studied compounds are characterized by two bands in the 280 - 400 nm regions. Results from this study provide a better comprehension antioxidant mechanism of drometrizole and present a new perspective for the design of electron-donor antioxidant molecules with enhanced antioxidant-photoprotective efficiencies for applications in commercial sunscreens.

Comparison of Nitric Oxide Concentrations in μs-and ns-Atmospheric Pressure Plasmas by UV Absorption Spectroscopy

In this paper,an absorption spectroscopy measurement method was applied on two atmospheric pressure plasma sources to determine their production of nitric oxide.The concentrations are essential for evaluating the plasma sources based on the principle of the Dielectric Barrier Discharge（DBD）for applications in plasma medicine.The described method is based on a setup with an electrodeless discharge lamp filled with a mixture of oxygen and nitrogen.One of the emitted wavelengths is an important resonance wavelength of nitric oxide（λ = 226.2 nm）.By comparing the absorption behaviour at the minimum and maximum of the spectral absorption cross section of nitric oxide around that wavelength,and measuring the change in intensity by the absorbing plasma,the concentration of nitric oxide inside the plasma can be calculated.The produced nitric oxide concentrations depend on the pulse duration and are in the range of 180 ppm to 1400 ppm,so that a distance of about 10 cm to the respiratory tract is enough to conform to the VDI Guideline 2310.

Synthesis of a Pair of Derivatives of N-Methylpyrrole Polyamide

A pair of derivatives of tetrameric N-methylpyrrole polyamide were synthesized in order to develop a new method for the study of interaction of the polyamide derivatives with DNA. Indole acetic acid and nicotinic acid were introduced to the polyamide in the synthesized compound, which showed an expected red shift in the UV spectrum. These compounds may function as a potential tool in the detection of the polyamide binding to DNA.

Joint fit of Warm Absorbers in COS and HETG spectra of NGC 3783

Warm Absorbers （WAs）, as an important form of AGN outflows, show absorption in both the UV and X-ray bands. Using XSTAR generated photoionization models, for the first time we present a joint fit to the simultaneous observations of HST/COS and Chandra/HETG on NGC 3783. A total of five WAs explain well all absorption features from the AGN outflows, which are spread over a wide range of parameters： ionization parameter log~ from 0.6 to 3.8, column density logNH from 19.5 to 22.3 cm-2, velocity v from 380 to 1060 km s-1, and covering factor from 0.33 to 0.75. Not all the five WAs are consistent in pressure. Two of them are likely different parts of the same absorbing gas, and two of the other WAs may be smaller discrete clouds that are blown out from the inner region of the torus at different periods. The five WAs suggest a total mass outflowing rate within the range of 0.22-4.1 solar mass per year.

Facile Synthesis of Broadleaf-Shaped Titanate Nanosheets with Excellent UV Absorption Behavior

Broadleaf-shaped titanate nanosheets(B-TNSs)were synthesized via one-pot solvothermal method,and characterized by scanning electron microscopy,transmission electron microscopy,and X-ray diffraction etc.It is found that the synthesized B-TNSs consist of broadleaf-shaped nanosheet with a lateral size of ca.100 nm and a thickness of ca.1.2 nm.Owing to the ultrathin thickness,obvious blue shift of the absorption band edge can be observed in the absorption spectrum of B-TNSs resulting from quantum size effect.Besides,the specific surface area of B-TNSs is determined to be 348 m2/g,which is ca.6-fold larger than that of commercial P25 TiO2 nanoparticles.In the optical absorption experiment,B-TNSs exhibit much stronger absorption for ultraviolet light than P25 TiO2.These advantages of B-TNSs in morphological structure and optical absorption may make it a potential application in ultraviolet absorption and photocatalytic field.

Simultaneous Raman and reflection UV/Vis absorption spectroelectrochemistry

In the present work,a new combination of Raman and ultraviolet and visible(UV/Vis)absorption spectroelectrochemistry in reflection mode is proposed.The new experimental setup allows obtaining the two kinds of spectroscopic data without interferences concomitantly with the electrochemical information.To the best of our knowledge,it is the first time to report the simultaneous obtention of electrochemical,electronic,and vibrational information in the same experiment.This new combination provides time-resolved information about the processes that are taking place on the electrode/solution interface which has significant implications in different fields of chemistry,such as modification of electrodes,studies of electrocatalytic reaction mechanisms,development of sensors,among others.Two different systems were used to demonstrate the advantages and capabilities of the brand-new technique,namely,the oxidation of potassium ferrocyanide,an out-sphere system that is usually employed in the validation of SEC techniques,and the electrochemical-surface enhanced Raman spectroscopy(EC-SERS)detection of crystal violet by in-situ formation of the silver SERS substrate,where the UV/Vis spectra were used to follow the formation of the SERS substrate,whereas the Raman response of a probe molecule was used to confirm either the formation of a nanostructured surface and to obtain the fingerprint of the molecule with a high time resolution.The brand-new experimental setup has shown to be useful,versatile,robust,compact,and easy to use for future applications.

Influence of high-temperature oxidation of SiC powders on curing properties of SiC slurry for digital light processing

Fabrication of silicon carbide(SiC)ceramics by digital light processing(DLP)technology is difficult owing to high refractive index and high ultraviolet(UV)absorptivity of SiC powders.The surface of the SiC powders can be coated with silicon oxide(SiO_(2))with low refractive index and low UV absorptivity via high-temperature oxidation,reducing the loss of UV energy in the DLP process and realizing the DLP preparation of the SiC ceramics.However,it is necessary to explore a high-temperature modification process to obtain a better modification effect of the SiC powders.Therefore,the high-temperature modification behavior of the SiC powders is thoroughly investigated in this paper.The results show that nano-scale oxide film is formed on the surface of the SiC powders by short-time high-temperature oxidation,effectively reducing the UV absorptivity and the surface refractive index(nʹ)of the SiC powders.When the oxidation temperature is 1300℃,compared with that of unoxidized SiC powders,the UV absorptivity of oxidized SiC powders decreases from 0.5065 to 0.4654,and a curing depth of SiC slurry increases from 22±4 to 59±4μm.Finally,SiC green bodies are successfully prepared by the DLP with the the oxidized powders,and flexural strength of SiC sintered parts reaches 47.9±2.3 MPa after 3 h of atmospheric sintering at 2000℃without any sintering aid.