FT transmission spectroscopy in the visible and ultraviolet spectral ranges

Fourier transform spectroscopy can be applied as a useful measurement technique in the visible and ultraviolet spectral range. Examples of high resolution measurements in these spectral ranges are shown.     

Infrared and ultraviolet spectral signatures and conformational preferences of jet-cooled serotonin

The ultraviolet and infrared spectroscopy of single conformations of neutral serotonin (5-hydroxytryptamine) have been studied in the gas phase using a combination of methods including laser-induced fluorescence, resonance-enhanced two-photon ionization, UV-UV hole-burning spectroscopy, and resonant ion-dip infrared spectroscopy. By comparison to its close analogue tryptamine, for which firm assignments to seven low-energy conformations have been made, UV and IR transitions due to eight conformations of serotonin are observed and assigned. The ultraviolet spectrum divides into two subsets of transitions separated from one another by approximately 230 cm-1 ascribable to syn and anti conformations of the 5-OH group. These two subsets are also distinguishable via their 5-OH stretch fundamentals, with the anti-OH subset shifted by approximately 4-5 cm-1 to lower frequency than those due to syn-OH conformers. The existing firm assignments for tryptamine play a decisive role in assignments in serotonin, where the alkyl CH stretch infrared spectrum is diagnostic of the conformation of the ethylamine side chain. Conformer A of serotonin (SERO(A)), with S1 <-- S0 origin transition at 32584 cm-1, is assigned to Gpy(out)/anti-OH, SERO(B) at 32548 cm-1 to Gpy(up)/anti, SERO(C) at 32545 cm-1 to Gph(out)/anti, SERO(D) at 32560 cm-1 to Anti(py)/anti, SERO(E) at 32537 cm-1 to Anti(up)/anti, SERO(F) at 32353 cm-1 to Gpy(out)/syn, SERO(G) at 32313 cm-1 to Gpy(up)/syn, and SERO(H) at 32282 cm-1 to Gph(out)/syn. The conformational preferences of serotonin differ from those of tryptamine most notably in the selective stabilization observed for the Gph(out)/anti-OH conformer SERO(C), which makes it the second-most intense transition in the ultraviolet spectrum, surpassed only by the Gpy(out)/anti-OH conformer SERO(A).     

Calorimetric standards for photothermal methods in ultraviolet and visible spectral regions

Utilizing a time-resolved thermal lensing (TRTL) technique coupled with laser flash excitation, we have determined the heat conversion efficiency, a, of photoexcited molecules in solution at room temperature. The efficiencies of pyridazine, dicumarol, and 8-quinolinol are unity in the ultraviolet region. Azulene is demonstrated to be a good calorimetric standard in the visible region. The solvent effect on the thermal lens signal is well explained by thermal properties of solvent molecules, i.e. the cubic expansion coefficient and the specific heat capacity.     

Synthesis,spectral characterisation and thermal studies of zirconyl complexes of biologically active molecules

Zirconyl complexes of hippuric acid (C₉H₉NO₃, hipH) and monophenylbutazone (4-butyl-1-phenyl-3,5-pyrazolidinedione, MPB) were prepared using ZrOCl₂ · 8H₂O and ZrO(NO₃)₃ · xH₂O and characterized by elemental analysis, molar conductance measurement and IR, UV–Vis and NMR spectral methods. Thermal decomposition behaviour was studied by thermogravimetry. The second harmonic generation (SHG) conversion efficiency of hippuric acid complexes was also studied.     

Synthesis and spectral study of biologically active macrocyclic complexes of divalent transition metal ions

The condensation reaction of succinyldihydrazide with glyoxal in the presence of divalent metal ions (1: 1: 1) results in the formation of the complexes of type [M(C₆H₈N₄O₂)X₂], where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl⁻, NO₃⁻, CH₃COO⁻. The complexes have been characterized with the aid of elemental analyses, conductance measurements and electronic, NMR, infrared spectral studies. On the basis of these studies, a six-coordinated distorted octahedral geometry in which two nitrogen and two carbonyl oxygen atoms are suitably placed for coordination toward metal ion, has been proposed for all the complexes. The complexes were tested for their in vitro antibacterial activity. Some of the complexes showed remarkable antibacterial activities against some selected bacterial strains.     

Adsorption properties of thermally stable and biologically active polyurea: its synthesis and spectral aspects

Novel polymer metal complexes were prepared by the condensation polymerization of a polymeric ligand with transition metal ions of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). The polymeric ligand was prepared by the addition polymerization of urea with toluene 2,4‐diisocyanate in 1:1 molar ratio. The polymeric ligand and its polymer metal complexes were characterized by elemental analysis, Fourier transform infrared spectroscopy, ¹³C‐NMR, and¹H‐NMR (nuclear magnetic resonance). The geometry was determined by electronic spectra and magnetic moment measurement. Thermogravimetric analysis (TGA) was utilized to find out the degradation process of the polyurea ligand and the polymer metal complexes. The TGA data revealed that all the metal‐containing polyureas are much more thermally stable than the corresponding polyurea ligand. The surface morphology of the polyurea ligand and cobalt(II)‐containing polyureas was determined by scanning electron micrographs. The antibacterial and antifungal activities of all the synthesized polymers were investigated against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis (bacteria) and Aspergillus niger, Candida albicans, and Aspergillus flavus (fungi). These compounds show remarkably good biocidal activities, which were enhanced after complexation with the metal. Batch adsorption studies of the ligand were carried out for malachite green dye, and the polyurea ligand was found to be a good adsorbent for this dye. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and spectral studies of the biologically active complexes of tantalum(V) with N-alkylphenothiazines

Dioxo-bridged binuclear tantalum(V) complexes with six N-alkylphenothiazines (NAP) of general formula [TaO(L)(C2O4)]2C2O4, (L=NAP) have been prepared and characterized on the basis of elemental analysis, conductometric, magnetic and thermogravimetric data. The spectra of the complexes indicate that both the phenothiazine ligands and oxalate groups are coordinated to tantalum in a bidentate fashion, suggesting a coordination number of six around metal. The fungitoxicity of the isolated complexes against several fungi has been investigated.     

Modification of spectral ultraviolet doses by different types of overcast cloudiness and atmospheric aerosol

Wavelength-dependent attenuation of ground-level ultraviolet (UV) dose by different cloud and aerosol situations at the Tartu Observatory site (58°15' N, 26°28' E, 70 m a.s.l) is under scrutiny. The spectra at wavelengths ranging below 400 nm have been recorded by the simple Avantes, Inc. array spectrometer AvaSpec-256 in 2004-2009. The spectral information was supported by the conventional broadband solar irradiance and by the necessary meteorological data. The average cloud modification factor (CMF) on overcast days from May to August has been quite low, 0.36 in UVA and 0.35 in UVB. In the UVA range, the reduction of the daily dose with increasing noon solar zenith angle (SZA) from 35-50° to 65-80° in overcast days has been about 20% more than in clear days, while in the UVB range it was 45% larger. No clear difference in the influence of SZA on CMF between low level (St, Ns) and medium level (As, Ac) overcast cloudiness has been found. The aerosol attenuation during large aerosol optical depth (AOD) episode has been comparable with that of medium level clouds with the wavelength dependency in the UVA range different from that of clouds.     

A fuzzy method for component identification and mixture evaluation in the ultraviolet spectral range

A fuzzy theory approach is proposed for interpreting component spectra that takes into account the imprecise character of both reference and sample spectra. The method enables more decisions to be made than is possible in least-squares comparison of spectra. The method can be used to quantify components under overlapping bands as needed in multicomponent spectrophotometry and for component resolution in chromatography with u.v. detection. The method is particularly suitable for problems in the u.v. range because it can deal with continuous spectra where factor and principal components methods fail.     

Xenon chloride ultraviolet B laser is more effective in treating psoriasis and in inducing T cell apoptosis than narrow-band ultraviolet B

Earlier we reported that a 308-nm xenon chloride (XeCl) UVB laser is highly effective for treating psoriasis. As ultraviolet B light seems to cause T cell apoptosis, in the present study we studied the ability of the XeCl laser to induce T-cell apoptosis in vitro, and then compared the apoptosis-inducing capacities of narrow-band UVB (NB-UVB) light and the XeCl laser. The role of laser impulse frequency and intensity in the therapeutical and apoptosis-inducing efficacy of XeCl laser was also investigated. Both XeCl laser and NB-UVB induced T cell apoptosis, but quantitative induction was greater with XeCl laser. Changes in the frequency and intensity of impulses of XeCl laser did not influence its therapeutic and T cell apoptosis-inducing efficacy. These results suggest that the more effective induction of T cell apoptosis can be responsible for the greater clinical efficacy of XeCl laser compared to NB-UVB. Additionally, the optical properties of the XeCl laser (a monochromatic, coherent, pulse-mode laser; easier precise dosimetry, there are no 'contaminating' wavelengths) can make this laser light an ideal tool for studies of the mode of action of UVB light.     

Synthesis, spectral, thermal and antimicrobial studies of some new tri metallic biologically active ceftriaxone complexes

Iron, cobalt, nickel and copper complexes of ceftriaxone were prepared in 1:3 ligand:metal ratio to examine the ligating properties of the different moieties of the drug. The complexes were found to have high percentages of coordinated water molecules. The modes of bonding were discussed depending on the infrared spectral absorption peaks of the different allowed vibrations. The Nujol mull electronic absorption spectra and the magnetic moment values indicated the Oh geometry of the metal ions in the complexes. The ESR spectra of the iron, cobalt, and copper complexes were determined and discussed. The thermal behaviors of the complexes were studied by TG and DTA techniques. The antimicrobial activities of the complexes were examined and compared to that of the ceftriaxone itself.     

Use of the vacuum ultraviolet spectral region for laser-induced breakdown spectroscopy-based Martian geology and exploration

Several elements important to planetary geology (e.g. Br, C, Cl, P, S) and the human exploration of Mars (e.g. toxic elements such as As) have strong emission lines in the purge and vacuum ultraviolet (VUV) spectral region (100–200 nm). This spectral region has not been extensively studied for space applications using geological samples. We studied emissions from the laser-induced breakdown spectroscopy (LIBS) plasma in this region using a sample chamber filled with 7 torr (930 Pa) of CO₂ to simulate the Martian atmosphere. Pressures down to 0.02 torr were also used to evaluate the effect of the residual CO₂ on the spectra and to begin investigating the use of VUV-LIBS for airless bodies such as asteroids and the Moon. Spectra were recorded using a 0.3-m vacuum spectrometer with an intensified CCD (ICCD) camera. The effects of time delay and laser energy on LIBS detection at reduced pressure were examined. The effect of ambient CO₂ on the detection of C in soil was also evaluated. Lines useful for the spectrochemical analysis of As, Br, C, Cl, P, and S were determined and calibration curves were prepared for these elements. Although LIBS is being developed for stand-off analysis at many meters distance, the experiments reported here were aimed at in-situ (close-up) analysis.     

On the importance of spectral responsivity of Robertson-Berger-type ultraviolet radiometers for long-term observations

A system to determine the spectral responsivity of ultraviolet (UV) radiometers has been developed and is routinely operated at the Central Ultraviolet Calibration Facility, at the National Oceanic and Atmospheric Administration. The instrument and the measurement methodologies are described. Results of measurements from thermally controlled broadband UV radiometers of the Robertson-Berger (R-B)-type are described. Systematic differences in the spectral response curves for these instruments have been detected. The effect of these differences on the field operation of UV-B radiometers has been studied by calculating the instrumental response from modeled UV spectra. The differences of the weighted spectral UV irradiances, measured by two radiometers with different spectral response functions, caused by the daily variation in the position of the sun were estimated for fixed values of total ozone, altitude and albedo, and for cloud-free conditions. These differences increase with the solar zenith angle and are as large as 8%. Larger differences in the instrumental response may be produced by ozone variations. Thus, care must be taken when analyzing data from R-B radiometers and comparing results from different instruments. Routine cycling of UV-B radiometers in operative networks without a careful determination of the spectral responsivity, or small drifts of the spectral responsivity, may strongly affect the accuracy of UV radiation measurements and produce an erroneous trend. Because of the possible differences among radiometers, it would not be practical to derive the long-term behavior of UV radiation without routine and thorough characterization of the spectral responsivities of the instruments.     

Surface-enhanced Raman scattering in the ultraviolet spectral region: UV-SERS on rhodium and ruthenium electrodes

We report the first observation of surface-enhanced Raman scattering (SERS) excited with ultraviolet (UV) light from transition metal electrodes. Adsorbed pyridine and SCN- on rough rhodium (Rh) and ruthenium (Ru) electrodes, respectively, have been studied using 325 nm laser excitation. In contrast, the best enhancers in the visible and near infrared, silver and gold, do not produce UV-SERS. The experimental data of UV-SERS are in agreement with our preliminary theoretical calculation based on the electromagnetic enhancement mechanism. The enhancement factor is about 2 orders of magnitude for the Rh and Ru electrodes when they are excited at 325 nm.     

Solar UVB and plant damage irradiances for different Argentinean regions

We calculated the integrated UVB and plant damage irradiances for Argentina, a country in the Southern Hemisphere spread over a large latitudinal range. The irradiances were calculated for clear sky days using the Madronich code for the average conditions of the months corresponding to the summer and winter solstices and the fall and spring equinoxes. Ozone, aerosol and ground albedo typical for each region and for each period of the year have been considered. A comparison was made of the behavior of these irradiances at the different locations. A more pronounced time dependence of the plant damage irradiance was obtained because of the fact that the corresponding spectrum is largely concentrated at a small wavelength of the UVB interval. We established a correlation between both irradiances, which can be approximated by a quadratic function. Because the plant damage irradiance is a quantity that is not directly measured by instruments, we showed the utility of the correlation by determining this biological effectiveness from the integrated UVB irradiance measured at the Astronomical Observatory of Rosario, Argentina, on clear sky days of the year 2001, as a characteristic example of the midlatitude near-sea level location of a highly productive agricultural region, which can be extended to other regions of the world. The plant damage results are relative ones (as is the case for the erythemal irradiance). So, they can be used to determine the maximum/minimum and asymmetry ratios, to study the influence of atmospheric variables and to make comparisons with other geographical locations.     

Chlorine detection in cement with laser-induced breakdown spectroscopy in the infrared and ultraviolet spectral range

A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis are time- and cost-intensive so an alternative method is developed using laser-induced breakdown spectroscopy (LIBS). The idea is to deploy LIBS to analyze drill cores by scanning the sample surface with laser pulses. Chlorine spectral lines in the infrared (IR) and ultraviolet (UV)-range were studied for chlorine detection in hydrated cement samples. The excitation energies of these spectral lines are above 9.2 eV. Hence high plasma temperatures and pulse energies in the range of some hundred millijoules are needed to induce sufficient line intensity levels at the required working distance. To further increase the line intensity and to lower the detection limit (LOD) of chlorine a measuring chamber is used where different ambient pressures and gases can be chosen for the measurements. The influences on the line intensity for pressures between 5 mbar and 400 mbar using helium as process gas and the influence of different laser burst modi like single and collinear double pulses are investigated. For the first time a LOD according to DIN 32 645 of 0.1 mass% was achieved for chlorine in hydrated cement using the UV line 134.72 nm.     

A method for determining the position of tautomeric equilibrium solely from infrared and ultraviolet spectral data

Conclusions A method was described for determining the position of equilibrium in tautomeric systems, using only data from IR and UV spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1887–1888, August, 1968     

Quantitative use of ultraviolet spectroscopy to calculate the effective irradiation dosage during weathering

The ultraviolet absorbance of a urethane coating showed typical yellowing that increased with exposure period. An effective dosage was calculated from the solar spectrum, the quantum yield for the degradation process and the ultraviolet absorption. Assuming a constant quantum yield, there is a clear acceleration of the absorption of damaging radiation because the ultraviolet absorption increases with exposure. This non-linear relationship offers possibilities on how to estimate a service lifetime. In addition, the yellowing can be analyzed as an “Urbach” tail which is usually attributed to structural disorder that introduces energy levels between the ground and excited electronic states.