UV Vis Spectral Techniques Research Articles

Photocatalytic Degradation of Organic Dyes by a High Efficient TiO2-Based Catalysts Under Solar Light Irradiation

In this work, the Er3+:YAlO3/Fe-doped TiO2 composite, a high efficient TiO2-based photocatalyst, was synthesized by ultrasonic dispersion and liquid boil methods. Among which, the Er3+:YAlO3 is a kind of upconversion luminescence agent, which was prepared by nitrate-citric acid method. It can emit ultraviolet light under visible light excitation. The Er3+:YAlO3/Fe-doped TiO2 composite was characterized by X-ray diffraction and UV–vis spectral techniques. The degradation of Acid Red B dye was used to evaluate the photocatalytic activity of the Er3+:YAlO3/Fe-doped TiO2 composite under solar light irradiation. It was found that the photocatalytic activity of Er3+:YAlO3/Fe-doped TiO2 composite was much higher than that for the similar system with only Fe-doped TiO2. And the influencing factors, such as Er3+:YAlO3 content, irradiation time, initial concentration of Acid Red B, addition amount of Er3+:YAlO3/Fe-doped TiO2 and NaCl, on the photocatalytic degradation were also investigated. The Er3+:YAlO3 as upconversion luminescence agent can elevate the photocatalytic activity of Fe-doped TiO2 powder. Moreover, the Fe2+ ion can restrain the recombination of photogenerated electrons and holes. Thus, this Er3+:YAlO3/Fe-doped TiO2 composite is a useful material for the detoxification of wastewater because it can efficiently utilize solar light by converting visible light into ultraviolet light.

Optochemical sensing of hydrogen chloride gas using meso-tetramesitylporphyrin deposited glass plate

Meso-tetramesitylporphyrin (MTMP) deposited glass plate (solid state sensor) was used to sense hydrogen chloride (HCl) gas based on optochemical method. Exposure of the solid state sensor to HCl vapor results in the formation of protonated meso-tetramesitylporphyrin (PMTMP). UV–vis and fluorescence spectral techniques were used to study the protonation of MTMP in dichloromethane–methanol mixture. The optical spectra of MTMP show an intense Soret band at 418 nm with a 14 nm red shift upon protonation by HCl. Ab-initio calculations were carried out to visualize the effect of protonation on planarity and stability of the porphyrin ring. The solid state sensor was characterized by UV–vis spectral technique. The sensor exhibits characteristic Soret and Q bands for the deposited MTMP with slight red shift when compared to MTMP in dichloromethane. The concentration of gaseous HCl was monitored from the changes in the absorbance of Soret band of PMTMP at 452 nm. The detection limit of the solid state sensor towards gaseous HCl was found to be 0.03 ppm. The present solid state sensor was highly stable for several months.

In Situ Preparation of Functional Heterogeneous Organotin Catalyst Tethered on SBA-15

A stable heterogeneous organotin catalyst has been prepared by in situ tethering organotin compounds on SBA-15. This was verified by XRD, TEM, N2 adsorption/desorption at −196 °C, FTIR and diffuse reflectance UV–vis spectral techniques. This material was much more active than the sample prepared by the grafting method for the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2 despite that its catalytic activity was dependent on the organotin amount. This could be attributed to the formation of organotin clusters with different structures and the larger surface area. After immobilization on the SBA-15 mesoporous material, the six-coordinated organotin clusters showed higher activity, compared to the tetrahedral Sn species. With increasing reaction temperature and CO2 pressure, the catalytic activity considerably increased.

5,7-Diaryl-3,4,6-trihydronaphthalen-2-ones의 One-pot 합성

sodium ethoxide의 존재하에서 3,5-diaryl-cyclohex-2-en-1-one와 methyl vinyl ketone로부터 5,7-Diaryl- 3,4,6-trihydronaphthalen-2-ones가 합성되었다. 이 생성물은 IR, UV-Visible, 1H-NMR, 13C-NMR 그리고 mass spectral techniques로 구조를 규명하였다. 1H과 13C signals의 피크들은 HSQC spectrum을 찍어 정확히 규명하였다. 5,7-Diaryl-3,4,6-trihydronaphthalen-2-ones have been synthesized from 3,5-diaryl-cyclohex-2-en-1- ones and methyl vinyl ketone in the presence of sodium ethoxide. The products were characterized by IR, UV-Visible, 1H-NMR, 13C-NMR and mass spectral techniques. To confirm 1H and 13C signals, HSQC spectrum was recorded and analyzed.

Testing the relation between UV–vis color and TiO 2 content of the lunar maria

Reflectance spectroscopy is important for placing lunar samples into a regional and global geologic context. To this end, the ultraviolet–visible (UV–vis) color ratio, used to estimate the TiO 2 composition of mature mare basalts, has been one of the most widely used spectral parameters in lunar exploration. We examine the correlation between UV–vis color and TiO 2 content using a combination of Clementine, Lunar Prospector, and sample data to document the extent to which color is dependent upon TiO 2. Examination of the remotely sensed data reveals that the correlation between UV–vis ratio and TiO 2 composition is best represented by a sigmoidal trend rather than the canonical linear or curvilinear correlation. With this information, we are then able to evaluate between two models that propose different explanations for the relationship between UV–vis color and TiO 2. The first model attributes the correlation between TiO 2 and UV–vis color to spectrally neutral opaques (i.e., ilmenite), while the other emphasizes the effect of Fe–Ti charge-transfer in lunar glasses and dual scattering mechanisms between high- and low-Ti basalts. We do not find evidence in the spectral data to support the occurrence of Fe–Ti charge-transfer in lunar glass as the principal cause for color in high-Ti basalts. The data also do not substantiate the existence of different scattering mechanisms (e.g., volume v. surface scattering) between high- and low-TiO 2 basalts. Instead, our analyses substantiate that the spectral effects of ilmenite exhibit a major influence over the UV–vis ratio. By including sample data we find that in addition to ilemenite/TiO 2 content, factors such as FeO content, ilmenite grain size, modal abundance of plagioclase, and the olivine-to-pyroxene ratio in a mare soils can influence the UV–vis continuum. These findings point to promising avenues of research that future UV–vis spectral techniques can exploit in order to yield more accurate TiO 2 estimates and potentially additional petrologic information.

Kinetics of the substitution of dehydroacetic acid in tris (dehydroacetato) Fe(III) complex by 8-hydroxyquinoline, di- and tetra-hydroxyquinone

The ligand substitution reactions of dehydroacetic acid (Hdha) in [Fe(dha) 3] with second ligand such as 8-hydroxyquinoline (Hquin), 1,4-dihydroxyanthraquinone (H 2dhaq) and 1,4,5,8-tetra-hydroxyanthraquinone (H 4thaq) were investigated spectrophotometrically by in low polarity solvents like benzene, chloroform and dichloromethane. It is deduced that the substitution reaction takes place through one successive step. The reaction was performed at four different temperatures (5–25) °C, and it exhibits a first order dependence on the concentration of the starting complex. The observed rate constant depends on the concentration of both leaving and entering ligands. The evaluation of the kinetic data gives activation parameters which support an associative mechanism in the transition states and the higher rate of substitution of the dha in Fe(dha) 3 complex is due to entropy effect. The solid complexes were synthesized and characterized by elemental analysis, IR and UV–vis spectral techniques.

Evidence for the role of 2-hydroxychromene-2-carboxylate isomerase in the degradation of anthracene by Sphingomonas yanoikuyae B1.

Sphingomonas yanoikuyae B1 is extremely versatile in its catabolic ability. An insertional mutant strain, S. yamoikuyae EK504, which is unable to grow on naphthalene due to the loss of 2-hydroxychromene-2-carboxylate isomerase activity, was utilized to investigate the role of this enzyme in the degradation of anthracene by S. yanoikuyae B1. Although EK504 is unable to grow on anthracene, this strain could transform anthracene to some extent. A metabolite in the degradation of anthracene by EK504 was isolated by high-pressure liquid chromatography (HPLC) and was identified as 6,7-benzocoumarin by UV-visible, gas-chromatographic, HPLC/mass-spectrometric, and 1H nuclear magnetic resonance spectral techniques. The identification of 6,7-benzocoumarin provides direct chemical and genetic evidence for the involvement of nahD in the degradation of anthracene by S. yanoikuyae B1.

Structural characteristics and second harmonic generation in l-threonine crystals

l-threonine, an organic material with interesting non-linear optical properties, has been grown in solution and characterized by X-ray diffraction, FT infrared spectral, Raman spectral, UV VIS spectral and thermal techniques. The structural and spectral characteristics show that strong hydrogen bonds appearing in l-threonine have an influence on the stabilization of the crystal structure. The main contributions to the second harmonic generation in threonine results from the hydrogen bond and also from the vibrational part due to very intense IR bands of the hydrogen bond vibrations. The OH and NH involved in strong hydrogen bonds are responsible for the higher thermal stability of l-threonine compared to other organic non-linear optical materials. l-threonine is thermally stable up to 270 °C.

Al-MCM-41 supported phosphotungstic acid: Application to symmetrical and unsymmetrical ring opening of succinic anhydride

Mesoporous Al-MCM-41 (Si/Al = 20) molecular sieve was synthesized hydrothermally and characterized by X-ray diffraction (XRD), nitrogen-sorption studies and 27Al and 29Si MAS-NMR spectroscopies. 10, 20 and 40 wt% phosphotungstic acid (PW) (H 3PW 12O 40) were supported on Al-MCM-41 and the resulting catalysts were characterized by XRD, FT-IR, nitrogen-sorption, DRIFT, 1H and 31P MAS-NMR and DRS UV–vis spectral techniques. 1H MAS-NMR spectra of PW/Al-MCM-41 revealed leveling of the acidity of PW protons to Al-MCM-41. Their catalytic activities were evaluated in the esterification of succinic anhydride with ethanol in the temperature between 60 and 120 °C. Monoethyl succinate (MES) and diethyl succinate (DES) were obtained as products. The effects of alcohol/anhydride molar ratio and temperature were studied. Unsymmetrical alcoholysis of succinic anhydride with methanol and 1-butanol was also carried out successfully.

Total luminescence spectral characteristics of natural organic matter (NOM) size fractions as defined by ultrafiltration and high performance size exclusion chromatography (HPSEC)

Natural organic matter (NOM) was isolated by reverse osmosis from two surface waters of differing climatic regimes and organic source material, in Norway and Georgia, USA. The NOM was separated into methodologically defined size fractions by ultrafiltration and high performance size exclusion chromatographic (HPSEC) techniques and the fractions were analyzed with UV-visible and total luminescence spectral techniques. While some systematic variation was observed, NOM from both systems had similar UV specific absorbance values and both had higher 254 nm specific absorbances in the larger molecular size fractions. Similarly, NOM from both systems had fluorescence spectral peaks in the regions of approximately λ ex/ λ em=225/425 nm and λ ex/ λ em=335/445 nm, consistent with spectra of humic substances in freshwater environments. Agreement of these measurements in two significantly different environments and with previously published literature indicates that freshwater NOM is very consistent relative to its absorbance and fluorescence chromophores, despite differences in the origin of the material and the early diagenetic processes to which plant material may be exposed.

Acidity and m-Xylene Isomerization Activity of Large Pore, Zirconium-Containing Alumino-silicate with BEA Structure

A large pore, zirconium-containing alumino-silicate with BEA structure, Zr–Al-β (SiO2/ZrO2=100 and 50; SiO2/Al2O3=25), has been synthesized hydrothermally using TEAOH as template and characterized by XRD, FTIR, and diffuse reflectance UV–visible spectral techniques to show that Zr4+ ions are isolated and are probably linked to the framework of the aluminosilicate of BEA structure. The FTIR studies of adsorbed pyridine, evacuated at different temperatures show an increase in Lewis as well as Brønsted acidity of Zr–Al-β samples in comparison to Zr-free Al-β and Zr-impregnated Al-β, having similar Al contents. The enhancement is probably the result of incorporation of Zr4+ ions into the β structure as Si–Oδ−⋖Zrδ+ linkages. The catalytic activity of Zr–Al-β samples is demonstrated in the isomerization of m-xylene at atmospheric pressure in a fixed bed reactor. The additional acidity of Zr–Al-β catalyst has been correlated with a marginal increase in the isomerization activity as well as selectivity to the isomerization products rather than the disproportionation products, particularly at temperatures below 500 K.

Biotransformation of 1-nitrobenzo[ e ]pyrene by the fungus Cunninghamella elegans

Biotransformation of 1-nitrobenzo[e]pyrene (1-nitro-BeP), an environmental pollutant derived from the nitration of a non-carcinogen, benzo[e]pyrene, was studied using the fungus Cunninghamella elegans ATCC 36112. After 72 h incubation, 89% of 1-nitro-[3H]BeP added had been metabolized to two major metabolites. These metabolites were separated by reversed-phase high performance liquid chromatography and identified by 1H NMR, UV-visible, and mass spectral techniques as 1-nitro-6-benzo[e]pyrenylsulfate and 1-nitrobenzo[e]pyrene 6-O-β-glucopyranoside. Comparison of the fungal metabolism patterns of 1-nitro-BeP and BeP indicates that the nitro group at the C-1 position of BeP altered the regioselectivity of metabolism.

Evidence for the role of 2-hydroxychromene-2-carboxylate isomerase in the degradation of anthracene by Sphingomonas yanoikuyae B1

Sphingomonas yanoikuyae B1 is extremely versatile in its catabolic ability. An insertional mutant strain, S. yanoikuyae EK504, which is unable to grow on naphthalene due to the loss of 2-hydroxychromene-2-carboxylate isomerase activity, was utilized to investigate the role of this enzyme in the degradation of anthracene by S. yanoikuyae B1. Although EK504 is unable to grow on anthracene, this strain could transform anthracene to some extent. A metabolite in the degradation of anthracene by EK504 was isolated by high-pressure liquid chromatography (HPLC) and was identified as 6,7-benzocoumarin by UV-visible, gas-chromatographic, HPLC/mass-spectrometric, and 1H nuclear magnetic resonance spectral techniques. The identification of 6,7-benzocoumarin provides direct chemical and genetic evidence for the involvement of nahD in the degradation of anthracene by S. yanoikuyae B1.

Stereoselective fungal metabolism of methylated anthracenes

The metabolism of 9-methylanthracene (9-MA), 9-hydroxymethylanthracene (9-OHMA), and 9,10-dimethylanthracene (9,10-DMA) by the fungus Cunninghamella elegans ATCC 36112 is described. The metabolites were isolated by high-performance liquid chromatography and characterized by UV-visible, mass, and 1H nuclear magnetic resonance spectral techniques. The compounds 9-MA and 9,10-DMA were metabolized by two pathways, one involving initial hydroxylation of the methyl group(s) and the other involving epoxidation of the 1,2- and 3,4- aromatic double bond positions, followed by enzymatic hydration to form hydroxymethyl trans-dihydrodiols. For 9-MA metabolism, the major metabolites identified were trans-1,2-dihydro-1,2-dihydroxy and trans-3,4-dihydro-3,4-dihydroxy derivatives of 9-MA and 9-OHMA. 9-OHMA was also metabolized to trans-1,2- and 3,4-dihydrodiol derivatives. The absolute configuration and optical purity were determined for each of the trans-dihydrodiols formed by fungal metabolism and compared with previously published circular dichroism spectral data obtained from rat liver microsomal metabolism of 9-MA, 9-OHMA, and 9,10-DMA. Circular dichroism spectral analysis revealed that the major enantiomer for each dihydrodiol was predominantly in the S,S configuration, in contrast to the predominantly R,R configuration of the trans-dihydrodiol formed by mammalian enzyme systems. These results indicate that C. elegans metabolizes methylated anthracenes in a highly stereoselective manner that is different from that reported for rat liver microsomes.

Synthesis and spectroscopic studies of platinum(II) complexes of N,N′-dicyclohexylethylenediamine

The platinum(II) complexes of the formula [Pt(DCHEDA)X 2], where DCHEDA is N,N′-dicyclohexylethylenediamine and X − is CL −, Br −, I −, 0.5C 2O 4 2− (oxalate), 0.5C 3H 2O 4 2− (malonate), 0.5C 9H 4O 6 2− (4-carboxyphthalate), 0.5S 2O 3 2− or 0.5SO 4 2−, have been synthesized and characterized by UVVis, IR, and 1H NMR spectral techniques. All the above complexes are non-electrolytes in DMF/H 2O, except the sulphate complex which becomes a 1:1 electrolyte after incubation for 24 h at 28 °C. The halide complexes were also studied by X-ray photoelectron spectroscopy and these data suggest that there is π-bonding from platinum to halide in these complexes. The oxalate, malonate and sulphate bind in their complexes as bidentate ligands to platinum through two oxygen atoms whereas the thiosulphate in its complex binds as a bidentate ligand to platinum through one oxygen atom and one sulphur atom.