Main Fluorescence Band Research Articles

Influence of light and Fe(III) ions on tetracycline degradation.

Tetracycline (TC) is an antibiotic produced on the largest scale in the world and used for the treatment of both humans and animals. Its removal from the circulation chain between the natural environment and animals is still a serious problem. Fe(III) ions can be used to break this chain. Fe(III) ions appear in water in spite of irradiation of Fe(III)-Cit complex and oxidation by oxygen present in water. Fe(III)-Cit was a reservoir of Fe(III) ions from which they were continuously released. Therefore, in this paper we studied an interaction between tetracycline (TC) and Fe(III) ions under fluorescent light at 20 °C and 30 °C in the water environment. This interaction leads to TC + Fe(III) coordinating complex formation. Changes caused by this process were monitored within 1860 min by measuring absorption and fluorescence spectra. The absorption spectra showed a charge-transfer stacking band(s) of oxidized and non-oxidized form of TC above 400 nm; in turn the fluorescence spectra revealed decay of initial bands and formation of the new ones. The initial, main fluorescence band at 16,660 cm-1 associated with the intramolecular proton transfer has gradually disappeared after Fe(III) ions binding to oxygen atoms in the BCD system rings of a TC molecule. Gaussian decomposition of all fluorescence spectra allowed extracting new bands, their evolution in time and calculating the rate of the first reaction step. Temperature rise of 10 °C caused more than a ten-fold increase in the first-order reaction rate.

Spectroscopic properties of Sm3+-doped NaGd(MoO4)2 crystal for visible laser application

A NaGd(MoO4)2 crystal doped with 2at.% Sm3+ was grown by the Czochralski method. Polarized absorption and fluorescence spectra of the crystal were measured at room temperature. Spectroscopic parameters, including absorption and emission cross sections, Judd-Ofelt intensity parameters, radiative transition rates, fluorescence branching ratios, and fluorescence lifetime of the 4G5/2 multiplet, were obtained and compared with other Sm3+-doped crystals. The main fluorescence band around 646nm is related to the 4G5/2→6H9/2 transition, which has a branching ratio of 45.4% and peak emission cross sections of 1.73×10–21 and 3.13×10–21cm2 for π and σ polarizations, respectively. The results indicate that the Sm3+:NaGd(MoO4)2 crystal may be a potential gain medium of red visible laser pumped directly by commercially available 405nm laser diode.

Triplet State Phosphorescence in Tris(8-hydroxyquinoline) Aluminum Light Emitting Diode Materials

Time-dependent density functional theory (TD-DFT) with the quadratic response technique is applied to the tris(8-hydroxyquinoline) aluminum complex (Alq3) to calculate spin–orbit coupling (SOC) effects and the main mechanism of the Alq3 phosphorescence. This compound exhibits weak phosphorescence which provides additional emission in organic light emitting diodes (OLEDs) besides the main fluorescence band. The phosphorescence affords to overcome the efficiency limit imposed by the formation of triplet excitons in the emissive layer of OLEDs. The zero-field splitting (ZFS) parameters are also calculated taking into account the spin–spin coupling in the first-order perturbation theory and the SOC in the second order. On the basis of the results obtained, we propose that an efficient spin-polarized injection and transport in long channels of Alq3, which have been recently achieved with new hybrid organic–inorganic interfaces, can proceed with the triplet electronic state admixture to the charge carriers. Our...

Structural and spectroscopy studies of complexes of the uranyl ion with 2,2′-bipyridine-N,N′-dioxide

2,2′-Bipyridine-N,N′-dioxide (bypO 2 = L) complexes of the composition [UO 2(bypO 2) 2(NO 3) 2]·2H 2O (UO 2–L 2–NO 3), [UO 2(bypO 2) 2H 2O](ClO 4) 2 (UO 2–L 2–ClO 4) and [UO 2bypO 2(H 2O) 2SO 4] (UO 2–L–SO 4) have been prepared by the reactions of the respective hydrated uranyl salts with the bypO 2 ligand in water. The structures of the complexes were elucidated using elemental and thermal analyses, IR and luminescence spectroscopy as well as luminescence lifetime measurements. The IR spectra show that the bonding between uranium and bypO 2, as well as uranium and water or a counter ion (NO 3 − and SO 4 2−) is formed. The nitrate or sulfate groups coordinate to the central metal ions in a monodentate manner. From TG–DTA curves, the nature of the water molecules present in the complexes and the decomposition temperature of the dehydrated uranyl complexes were determined. The thermal stability of the anhydrous uranyl complexes increases in the series: (UO 2–L 2–NO 3) < (UO 2–L 2–ClO 4) < (UO 2–L–SO 4). All the compounds show green-yellow intense luminescence. The main fluorescence bands and the emission lifetimes in these complexes were determined. The luminescence spectra of all the prepared complexes differ from each other with respect to their peak maxima positions. The luminescence lifetimes also vary. The structure of the (UO 2–L–SO 4) complex was determined by X-ray single-crystal analysis.

Influence of erbium doping on phase transition and optical properties of strontium barium niobate

The optical properties of erbium impurities in strontium barium niobate are investigated measuring optical absorption and emission in the visible and near infrared spectral region. For the main fluorescence band at 1.55 μm, an anomalous dependence of the fluorescence decay time on dopant concentration is found which, however, can be consistently explained by reabsorption effects. A Judd–Ofelt analysis of the absorption spectra together with an appropriate analysis of the reabsorption yields a radiative quantum efficiency of approximately 60%. In addition, erbium dopants are shown to efficiently influence the phase transition temperature of strontium barium niobate.

High pressure and high temperature induced polymeric C 60 nanocrystal

In this paper, C 60 nanosheets with polymeric phases have been obtained under various high pressures and high temperatures, including orthorhombic and tetragonal polymeric phases. The structures have been identified and compared with those of nanorods by photoluminescence and Raman spectroscopies. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The difference of photoluminescence and Raman spectra between nanosheets and nanorods samples treated under the same conditions is probably caused by different polymerization degree in these samples because of different shapes.

Photoluminescence properties of high-pressure-polymerized C60 nanorods in the orthorhombic and tetragonal phases

C 60 nanorods in two polymeric phases have been synthesized under different high pressure and high temperature conditions. Orthorhombic and tetragonal phases have been identified from Raman spectra. The rod shape can be kept under quasihydrostatic pressure. The photoluminescence intensity of the polymeric C60 nanorods has been greatly enhanced compared with that of pristine C60 nanorods. The main fluorescence band shifted from 730nm in the unpolymeric phase to 748nm and near infrared 780nm in the orthorhombic and tetragonal phases, respectively. The enhanced photoluminescence with tunable frequency for different polymeric C60 nanorods suggests potential applications in luminescent nanomaterials.

Effect of Crystallization of Li 2O-Al 2O 3-SiO 2 Glasses on Luminescence Properties of Nd 3+ Ions

Generally the preparation of lithium aluminosilicate (LAS) glasses is difficult on account of their high melting temperature. This research managed to prepare LAS glasses doped with Nd 3+ ions by the conventional melting and quenching technique, at a relatively low melting temperature and by the use of some additives. Lithium aluminosilicate glasses were transformed to glass-ceramics by controlled nucleation and the crystallization process. The characterizations were performed by differential thermal analysis, X-ray diffraction, UV-Vis-NIR scanning spectrophotometry, and fluorescence spectrometry. The research focused on the photoluminescence spectra of the initial glass and the glass-ceramics under different heat-treatment schedules. Three main fluorescence bands centering at about 890, 1065, and 1330 nm were observed, which corresponded to the transitions of 4F 3/2→ 4I 9/2, and 4F 3/2→ 4I 11/2, and 4F 3/2→ 4I 13/2, respectively. Phase compositions of glass-ceramics were found to affect their fluorescent characteristics considerably. The fluorescent intensity increased markedly when Nd 3+ ions entered the Li x Al x Si 1- x O 2 β-eucryptite solid solution (SS). Quenching occurred when Nd 3+ ions located at Li x Al x Si 3- x O 6 β-eucryptite SS. Quenching disappeared after Li x Al x Si 3- x O 6 β-eucryptite SS recrystallized into β-spodumene SS. The effectively induced cross section σ in of Nd 3+ ions located at the Li x Al x Si 1- x O 2 β-eucryptite SS was 1.931 × 10 −21 cm 2 at 1065 nm.

High Pressure and High Temperature Induced Polymeric C60 Nanorods and Their Photoluminescence Properties

AbstractWe report that C60 nanorods of three polymeric phases have been synthesized under high pressure and high temperature and that the photoluminescence properties of these polymeric nanorods also have been studied. C60 nanorods were fabricated by a facile solution evaporation method. Raman spectra indicate that this material transformed into orthorhombic, tetragonal and rhombohedral polymeric phases under various high pressure and high temperature conditions. SEM measurements show that the shape of the nanorods can be kept under quasi-hydrostatic pressure condition. The photoluminescence intensity of the polymeric C60 nanorods has been enhanced compared with that of the pristine C60 nanorods. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The enhanced fluorescence with adjustable frequency for different polymeric C60 nanorods makes possible potential application in luminescent nanomaterials.

Orientation and conformation of octadecyl rhodamine B in hybrid Langmuir–Blodgett monolayers containing clay minerals

To control the molecular organization of octadecyl rhodamine B (RhB18), hybrid Langmuir–Blodgett monolayers containing clay minerals were prepared. The orientation and conformation of the RhB18 molecule were analyzed by polarized attenuated total reflection Fourier transform infrared (ATR–FTIR) spectroscopy and fluorescence spectroscopy. Monomers and dimers of RhB18 were observed by UV-Vis absorption spectroscopy. Infrared bands of RhB18 exhibited dichroism and shifted to higher or lower wavenumbers in films as a function of clay content. The main fluorescence band of RhB18 was more intense and shifted to lower wavelengths in films with higher clay content. In films without clay, the phenyl group of RhB18 is tilted relative to the xanthene group and both groups are tilted relative to the substrate. In films with clay, both the phenyl group and xanthene group are oriented parallel to the clay surface which is parallel to the substrate. The clay mineral surface induces a change in the conformation and orientation of the RhB18 chromophore.

The differentiation of biodegradable and non‐biodegradable dissolved organic matter in wastewaters using fluorescence spectroscopy

AbstractThe chemical and biochemical oxygen demand values of a number of synthetic and wastewater samples were determined using fluorescence spectroscopy. Treated and untreated sewage samples were obtained from a local sewage treatment works while synthetic samples were analysed before, during, and after treatment via a rotating biodisc contactor. Fluorescence intensities were normalised using the water Raman signal as an internal standard and corrections applied to take into account the attenuation effects caused by the sample matrix. The fluorescence emission spectra (λexc = 280 nm) of synthetic and sewage samples were very similar in that two main fluorescence bands centred around 350 nm and 440 nm were observed in all samples. Normalised fluorescence data, centred at 350 nm, correlate well with corresponding BOD, COD and TOC values (R2 values ranging between 0.93 and 0.98). Using BOD, COD and TOC data the fluorescence at 350 nm and 440 nm can be apportioned to biodegradable and non‐biodegradable dissolved organic matter respectively. The findings of this research show that fluorescence data can be used to quantify oxygen demand values (chemical and biochemical) and total organic carbon values. Furthermore, the fluorescence spectral response can be apportioned to biodegradable (BOD) and non‐biodegradable (COD − BOD) dissolved organic matter. The potential of using fluorescence spectroscopy as a possible tool for real‐time monitoring of sewage wastes is discussed.© 2002 Society of Chemical Industry

Study of uranyl(VI) malonate complexation by time resolved laser-induced fluorescence spectroscopy (TRLFS)

SummaryThe uranyl(VI) malonate complex formation was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at pH 4 and an ionic strength of 0.1 M NaClO4. The uranium concentration was 5 × 10−6M at ligand concentrations from 1 × 10−5to 1 ×−2M.The measured fluorescence lifetimes of the 1:1 and 1:2 uranyl(VI) malonate complexes are 1.24 ± 0.02 µs and 6.48 ± 0.02 µs, respectively. The fluorescence lifetime of the uranyl(VI) ion is 1.57 ± 0.06 µs in 0.1 M perchloric media. The main fluorescence bands of the malonate complexes show a bathochromic shift compared to the uranyl(VI) ion and are centered at 494 nm, 515 nm and 540 nm for the 1:1 complexes and at 496 nm, 517 nm and 542 nm for the 1:2 complex. The spectra of the individual uranyl(VI) malonate complexes were calculated using a multi exponential fluorescence decay function for each intensity value at each wavelength, covering the entire wavelength range. Stability constants were determined for the complexes UO2C3H2O4°(aq)and UO2(C3H2O4)22−from results of spectra deconvolution using a least square fit algorithm (logβ1° = 4.48 ± 0.06, logβ2° = 7.42 ± 0.06 or logK2° = 2.94 ± 0.04). The results are compared with literature values obtained by potentiometric measurements.

Interaction of uranium(VI) with silicic acid in aqueous solutions studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS)

We investigated for the first time the complex formation in the uranyl–silicate system by fluorescence spectroscopy. The interaction between soluble species of uranium(VI) with silicic acid was studied in 0.3 M NaClO 4 solution using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Tetramethylorthosilicate (TMOS) was used as source of silicic acid in order to minimize the formation of polymeric silicon species. Fluorescence lifetimes were obtained for (a) the free uranyl cation of 1.7±0.3 μs, and (b) the 1:1 silicato–uranyl complex of 19.0±4 μs. The main fluorescence bands of the complex UO 2OSi(OH) 3 + are centered at 500, 521, 544 and 570 nm. The stability constant of the complex UO 2OSi(OH) 3 + was determined at pH 3.9, as log β°=−(1.67±0.20) using an uranyl concentration of 2.3×10 −5 M, and a monosilicic acid concentration up to 5.4×10 −3 M.

Fluorescence Spectroscopy on Single CdS Nanocrystals

By use of low-temperature (20 K) confocal microscopy, fluorescence spectra of isolated single CdS nanocrystals have been recorded. The narrowest measured line width of the main fluorescence band has been determined to be about 5 meV at the lowest excitation intensities. At higher intensities at least three additional observations are made: the main fluorescence band broadens, a line to the blue of the main peak evolves, and a peak due to the coupling to a longitudinal optical phonon appears.

Fluorescence properties of the dye-intercalated smectite

The fluorescence properties of the dye Rhodamine 590 and Rhodamine 640 intercalated into montmorillonite were studied. All of the intercalation reactions were accomplished in an ethanol solution which contained the corresponding quality of Rhodamine. The TG-DTA and the X-ray diffraction data showed that the immobilization of Rhodamine depended on the amount of ethanol incorporated in the interlayer space of montmorillonite. The 14.8 Å basal spacing of products indicated a conformation of Rhodamine with the xanthene nucleus and the phenyl group positioned parallel and perpendicular to the silicate layer, respectively. Also, the infrared pleochromism, which supported the proposed orientation of the phenyl group, was observed at 1250 and 712 cm −1. The main fluorescence bands of both products were observed near 600 nm when excited by the 514.5 nm line of an argon ion laser. The results indicated that the mesomeric structure determined the fluorescence behavior, which was little different for the two products owing to the environment of the interlayer. These data are briefly discussed relative to the reaction conditions utilized for the synthesis of products. Also, the results support the idea that the products have a high potential for use as a host for a tunable laser.

Age and fluorescence characteristics in some species of Athiorhodaceae.

Nonsulfur photosynthetic bacteria (Athiorhodaceae) exhibit a time-variable fluorescence in addition to a constant fluorescence. All species examined show upon aging a remarkable gain in the variable component at the expense of the constant component while the total fluorescence remains essentially invariant. This result can be rationalized by supposing a change in distribution of bacteriochlorophyll in photosynthetic units as cells age. Alternatively, one may assume operation of two photochemical systems-one cyclic and predominant in young cells, the other noncyclic and predominant in old cells. It is also noted that a hitherto unreported minor fluorescence with maximum emission at approximately 860 nm exists in addition to the well-known main fluorescence band at approximately 890 nm. The rise in variable fluorescence is associated with the main band, a result in accord with the notion that the bacteriochlorophyll component responsible and absorbing at 870 nm is directly in contact with the energy trap.