Spectroscopy

Near-field spectroscopy of silicon dioxide thin films

by Zhe Fei

L. M. Zhang1, G. O. Andreev2, Z. Fei2, A. S. McLeod2, G. Dominguez3, M. Thiemens3, A. H. Castro-Neto4, D. N. Basov2, and M. M. Fogler2

We analyze the results of scanning near-field infrared spectroscopy performed on thin films of a-SiO2 on Si substrate.... more We analyze the results of scanning near-field infrared spectroscopy performed on thin films of a-SiO2 on Si substrate. The measured near-field signal exhibits surface-phonon resonances whose strength has a prominent thickness dependence in the range from 2 to 300 nm. These observations are compared with calculations in which the tip of the near-field infrared spectrometer is modeled either as a point dipole or an elongated spheroid. The latter model accounts for the antenna effect of the tip and gives a better agreement with the experiment. Possible applications of the near-field technique for depth profiling of layered nanostructures are discussed.

COMPARATIVE ANALYSIS FOR METAL BINDING CAPACITY OF CYSTEINE BY USING UV-VIS SPECTROPHOTOMETER

by Nandita Dasgupta

Co-authored with - Nandita Dasgupta, Gyanendra Gour, Rashmi Dubey, Kumari Amrita.

Journal Name- International Journal Of Applied Biology And Pharmaceutical Technology

The metal binding capacity of cysteine with three different metals Nickel, Copper and Lead was studied using UV-Vis... more The metal binding capacity of cysteine with three different metals Nickel, Copper and Lead was studied using UV-Vis spectrophotometer for which absorbance values were taken after interaction of cysteine with metal salt solutions (10ppm and 100ppm). Before taking above absorbance dilution factor was set using cysteine stock. The increase in peak intensity was observed when metal salt solution and metal saltcysteine solution were compared. Based on peak shift and peak intensity finally it can be concluded that the binding capacity of cysteine with Nickel is more, followed by lead and copper. The normal chromophore activity in cysteine is due to the sulphur in which the transition takes place from non bonding orbital’s to the excited antibonding orbital in the range of 210-215nm range. The binding of the metals with cysteine may affect the chromophore activity and may also lead to structural damage of the chromophore. This can give the decrease in the peak intensity or the complete shift in the peak. These results suggest that cysteine metal binding ability can be used for the removal of the metals in water purification. Also this property can be used in removal of metals from our body considering the fact that cysteine may not show adverse effect in the system. So we can go for designing a new type of drug containing cysteine which helps to prevent the accumulation of such metals and thus prevent us from adverse effect.

COMPARATIVE ANALYSIS FOR METAL BINDING CAPACITY OF CYSTEINE BY USING UV-VIS SPECTROPHOTOMETER

by Shivendu Ranjan

Co-authored with - Nandita Dasgupta, Gyanendra Gour, Rashmi Dubey, Kumari Amrita.

Journal Name- International Journal Of Applied Biology And Pharmaceutical Technology

The metal binding capacity of cysteine with three different metals Nickel, Copper and Lead was studied using UV-Vis... more The metal binding capacity of cysteine with three different metals Nickel, Copper and Lead was studied using UV-Vis spectrophotometer for which absorbance values were taken after interaction of cysteine with metal salt solutions (10ppm and 100ppm). Before taking above absorbance dilution factor was set using cysteine stock. The increase in peak intensity was observed when metal salt solution and metal saltcysteine solution were compared. Based on peak shift and peak intensity finally it can be concluded that the binding capacity of cysteine with Nickel is more, followed by lead and copper. The normal chromophore activity in cysteine is due to the sulphur in which the transition takes place from non bonding orbital’s to the excited antibonding orbital in the range of 210-215nm range. The binding of the metals with cysteine may affect the chromophore activity and may also lead to structural damage of the chromophore. This can give the decrease in the peak intensity or the complete shift in the peak. These results suggest that cysteine metal binding ability can be used for the removal of the metals in water purification. Also this property can be used in removal of metals from our body considering the fact that cysteine may not show adverse effect in the system. So we can go for designing a new type of drug containing cysteine which helps to prevent the accumulation of such metals and thus prevent us from adverse effect.

Integrated computational approaches for spectroscopic studies of molecular systems in the gas phase and in solution: pyrimidine as a test case

by Fabio Trani

Malgorzata Biczysko, Julien Bloino, Giuseppe Brancato, Ivo Cacelli, Chiara Cappelli, Alessandro Ferretti, Alessandro Lami, Susanna Monti, Alfonso Pedone, Giacomo Prampolini, Cristina Puzzarini, Fabrizio Santoro, Fabio Trani and Giovanni Villani
Theor. Chem. Acc. 131, 1201 (2012)
http://dx.doi.org/10.1007/s00214-012-1201-3

Contrasting the excited state reaction pathways of phenol and para-methylthiophenol in the gas and liquid phases

by Tom Oliver

To explore how the solvent influences primary aspects of bond breaking, the gas and solution phase photochemistries of... more To explore how the solvent influences primary aspects of bond breaking, the gas and solution phase photochemistries of phenol and of para-methylthiophenol are directly compared using, respectively, H (Rydberg) atom photofragment translation spectroscopy and femtosecond transient absorption spectroscopy. Approaches are demonstrated that allow explicit comparisons of the nascent product energy disposals and dissociation mechanisms in the two phases. It is found, at least for the case of the weakly perturbing cyclohexane environment, that most aspects of the primary reaction dynamics of the isolated molecule are reproduced in solution. Specifically, in the gas phase, both molecules can undergo fast X–H (X = O, S) bond dissociation upon excitation with short wavelengths (193 < λpump < 216 nm), following population of the dissociative S2 (11πσ*) state.  Product electronic branching, vibrational and translational energy disposals are determined. Photolysis of phenol and para-methylthiophenol in solution at 200 nm results in formation of vibrationally excited radicals on a timescale shorter than 200 fs.  Excitation of para-methylthiophenol at 267 nm reaches close to the S1 (1pipi*)/S2 (11pisigma*) conical intersection (CI): ultrafast dissociation is observed in both the isolated and solution systems – again indicating direct dissociation on the S2 potential.  Comparing results for this precursor at different excitation energies, the extent of geminate recombination and the derived H-atom ejection lengths in the condensed phase photolyses are in qualitative agreement with the translational energy release measured in the gas phase studies. Conversely excitation of phenol at 267 nm prepares the system in its S1 state at an energy well below its S1/S2 CI; the slow O–H bond fission inferred in the gas phase experiments is observed directly in the time-resolved studies in cyclohexane solution via the appearance of phenoxyl radical absorption after ~1 ns, with only S1 excited state absorption discernible at earlier delay times. The slow O–H bond fission in solution provides additional evidence for a tunnelling dissociation mechanism, where the H atom tunnels beneath the lower diabats of the S2/S1 CI. Finally, the photodissociation of phenol clusters in solution is considered, where evidence is presented that the O–H dissociation coordinate is impeded in H-bonded dimers.

Combined in situ electrochemical impedance spectroscopy UV/Vis and AFM studies of Ag nanoparticle stability in perfluorinated films

by Benjamin Wilson

K. Yliniemi, a, b, B. Özkaya, b, N. Alissawi, c, V. Zaporojtchenko, c, T. Strunskus, c, B.P. Wilson, a,b,1, F. Faupel, c, G. Grundmeier, b

a Aalto University, Department of Chemistry, P.O. Box 16100, 00076 AALTO Espoo, Finland
b University of Paderborn, Institute for Polymer Materials and Processes, Faculty of Natural Science, Warburger Str. 100, 33098 Paderborn, Germany
c Institute for Materials Science, Multicomponent Materials, Faculty of Engineering, Christian-Albrechts University at Kiel, Kaiserstr. 2, 24143 Kiel, Germany

1 ASTUTE, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP, UK.

Materials Chemistry and Physics Volume 134, Issue 1, 15 May 2012, Pages 302–308

In situ electrochemical UV/Vis spectroscopic analysis in combination with AFM measurements were performed to study the... more In situ electrochemical UV/Vis spectroscopic analysis in combination with AFM measurements were performed to study the reactivity of Ag nanoparticles sandwiched in between two polytetrafluorethylene (PTFE) films. The electrolyte uptake in the film was correlated with the onset of the changes in the surface plasmon resonance by measuring the film capacitance and the surface plasmon resonance peak simultaneously as a function of the exposure time. AFM studies indicate that both particle ripening and Ag dissolution take place and the dissolution kinetics was shown to decrease with increasing covering film thickness.

Large-scale first principles configuration interaction calculations of optical absorption in boron clusters

by Ravindra Shinde

Formation of Ag nanoparticles and enhancement of Tb 3 luminescence in Tb and Ag co-doped lithium-lanthanum-aluminosilicate glass

by Patryk Piasecki

Local changes in the catalytic site of mammalian histidine decarboxylase can affect its global conformation and stability

by Carlos Rodriguez-Caso

In search of space: Fourier spectroscopy, 1950-1970

by Sean Johnston

In the large grey area between science and technology, specialisms emerge with associated specialists. But some... more In the large grey area between science and technology, specialisms emerge with associated specialists. But some specialisms remain ‘peripheral sciences’, never attaining the status of ‘disciplines’ ensconced in universities, and their specialists do not become recognised professionals. A major social component of such side-lined sciences – one important grouping of technoscientific workers – is the ‘research-technology community’. An important question concerning research-technology is to explain how the grouping survives without specialised disciplinary and professional affiliations. The case discussed illustrates the dynamics of one such community.

Paper 1

by Mrittunjoy Guha Majumdar

Raman Spectroscopy: A Comprehensive Review

by Edmir Silva

Anne Crawford, Edmir Silva, Karen York, Chenxiang Li

In this comprehensive review, a general introduction, an explanation of the technique physics, several specific... more In this comprehensive review, a general introduction, an explanation of the technique physics, several specific examples of applications on polymers and sample preparation requirements of Raman spectroscopy are included.  In addition, the local availability of Raman facilities at N.C. State as well as availability in the current market was investigated.
Raman spectroscopy is a structural characterization technique that relies on inelastic scattering of monochromatic light, which is known as Raman scattering.  The wave number position indicates the vibrational states in the material while the width describes the molecular structure.  Also, the intensities can be compared in the polarized and perpendicular directions to determine the orientation and symmetry of a material.  In order to understand how Raman spectroscopy works, the physics of technique are discussed.  Analysis methods were discussed with examples in the corresponding sections.  A commercial analysis of Raman instrument features and price, as well as operating costs at local and regional labs were also discussed.      Finally, a comparison of Raman spectroscopy to infrared spectroscopy and x-ray fluorescence spectroscopy are discussed.

Bisectors of the HARPS cross-correlation function. The dependence on stellar atmospheric parameters

by Ozgur Basturk

Co-authors: Dall, T. H.; Collet, R.; Lo Curto, G.; Selam, S. O. published in Astronomy & Astrophysics, V535, A17.

Context. Bisectors of the HARPS cross-correlation function (CCF) can discern between planetary radial-velocity (RV)... more Context. Bisectors of the HARPS cross-correlation function (CCF) can discern between planetary radial-velocity (RV) signals and spurious RV signals from stellar magnetic activity variations. However, little is known about the effects of the stellar atmosphere on CCF bisectors or how these effects vary with spectral type and luminosity class.
Aims: Here we investigate the variations in the shapes of HARPS CCF bisectors across the HR diagram in order to relate these to the basic stellar parameters, surface gravity and temperature.
Methods: We use archive spectra of 67 well studied stars observed with HARPS and extract mean CCF bisectors. We derive previously defined bisector measures (BIS, vbot, cb) and we define and derive a new measure called the CCF bisector span (CBS) from the minimum radius of curvature on direct fits to the CCF bisector.
Results: We show that the bisector measures correlate differently, and non-linearly with log g and Teff. The resulting correlations allow for the estimation of log g and Teff from the bisector measures. We compare our results with 3D stellar atmosphere models and show that we can reproduce the shape of the CCF bisector for the Sun.

Time-resolved spectroscopy of the electrode region in a fluorescent lamp

by Thomas Lennartsson

Co-authored with Sven Huldt. Published in Canadian Journal of Physics, 2011, 89:(5) 627-631

In this paper, the ongoing spectroscopic investigations of the plasma inside a fluorescent lamp at Lund Observatory is... more In this paper, the ongoing spectroscopic investigations of the plasma inside a fluorescent lamp at Lund Observatory is presented. The intensity of the spectral lines of neutral and singly ionized mercury and krypton in the electrode region in a fluorescent lamp are investigated, both as a function of current through the tube and time resolved during an AC cycle. The results show different dynamics for different spectral lines, which may be due to different population mechanisms and transport phenomena in the discharge. To correctly interpret the data, a model for the electrode region is necessary; however, for this purpose information on processes like electron collision cross-sections, Penning ionization rates, and recombination rates are needed

Branching fractions in singly ionized tungsten

by Thomas Lennartsson

Co-authored with H Nilsson, R Blackwell-Whitehead, L Engström and S Huldt, published in Journal of Physics B: Atomic, Molecular and Optical Physics 44 245001

The intensity-calibrated spectra of W II have been recorded in the spectral interval 23 000–51 300 cm−1 (1950–4350 Å),... more The intensity-calibrated spectra of W II have been recorded in the spectral interval 23 000–51 300 cm−1 (1950–4350 Å), using the FT500 UV Fourier Transform Spectrometer at Lund Observatory. Combining the intensity data in this work with lifetimes previously measured using the time-resolved laser-induced-fluorescence (TR-LIF) technique resulted in transition probabilities and log gf values for 95 transitions in W II, originating from nine different upper levels with energies between 47 179 and 55 392 cm−1. Of these transitions, 85 have never been measured before. The new data are compared with theoretical calculations and with previously measured values when available.

Compressive Echelle spectroscopy

by Mark Davenport

Co-authored with L. Xu, M.A. Turner, T. Sun, and K.F. Kelly (Proc. Unconventional Imaging and Wavefront Sensing VII at SPIE Optics & Photonics, San Diego, California, August 2011.)

Building on the mathematical breakthroughs of compressive sensing (CS), we developed a 2D spectrometer system that... more Building on the mathematical breakthroughs of compressive sensing (CS), we developed a 2D spectrometer system that incorporates a spatial light modulator and a single detector. For some wavelengths outside the visible spectrum, when it is too expensive to produce the large detector arrays, this scheme gives us a better solution by using only one pixel. Combining this system with the “smashed filter” technique, we hope to create an efficient IR gas sensor. We performed Matlab simulations to evaluate the effectiveness of the smashed filter for gas tracing.

Fluorescence EEM Spectroscopy for Rapid Identification and Quality Evaluation of Cell Culture Media Components.

by Alan Ryder

B. Li, P.W. Ryan, M. Shanahan, K.J. Leister, and A.G. Ryder. Applied Spectroscopy, 65(11), 1240-1249, (2011).

The application of fluorescence excitation-emission matrix (EEM) spectroscopy to the quantitative analysis of complex,... more The application of fluorescence excitation-emission matrix (EEM) spectroscopy to the quantitative analysis of complex, aqueous solutions of cell culture media components was investigated. These components, yeastolate, phytone, recombinant human insulin, eRDF basal medium, and four different chemically defined (CD) media, are used for the formulation of basal and feed media employed in the production of recombinant proteins using a Chinese Hamster Ovary (CHO) cell based process. The comprehensive analysis (either identification or quality assessment) of these materials using chromatographic methods is time consuming and expensive, and not suitable for high throughput quality control. The use of EEM in conjunction with multi-way chemometric methods provided a rapid, non-destructive analytical method suitable for the screening of large numbers of samples. Here we used multiway robust principal component analysis (MROBPCA) in conjunction with n-way partial least-squares-discriminant analysis (NPLS-DA) to develop a robust routine for both the identification and quality evaluation of these important cell culture materials. These methods are applicable to a wide range of complex mixtures since they do not rely on any predetermined compositional or property information, thus making them potentially very useful for sample handling, tracking, and quality assessment in biopharmaceutical industries.

Determination of the Concentration of Single-Walled Carbon Nanotubes in Aqueous Dispersions Using UV Visible Absorption Spectroscopy

by Abdur Rehman Jalil

"S. Attal", "R. Thiruvengadathan", "O. Regev"

Stable, homogeneous, aqueous dispersions of single walled carbon nanotubes (SWNTs) are prepared by non specific... more Stable, homogeneous, aqueous dispersions of single walled carbon nanotubes (SWNTs) are prepared by non specific physical adsorption of surfactants enhanced by sonication. Upon centrifugation, supernatant and precipitate phases are obtained. The initial weights of the SWNTs and the surfactant are divided between these two phases, and the respective SWNT concentration in each phase is unknown. The focus of this work is on the determination of the true concentration of raw, exfoliated HiPCO SWNTs in the supernatant phase. A UV visible absorption-based approach is suggested for a direct measurement of the SWNT and the surfactant concentration in the supernatant. UV visible absorbance spectra of SWNTs surfactant dispersions and surfactants alone reveal that the intensity of a certain peak, attributed to the ð-plasmon resonance
absorption, is unaffected by the presence of most surfactants. A calibration plot is then made by monitoring the intensity of the peak as a function of the true concentration of the exfoliated SWNTs. Thus, we are able to determine the unknown concentration of surfactant-dispersed HiPCO SWNTs in the supernatant solution, simply by measuring its optical absorbance. Moreover, we can now calculate the surfactant efficiency in dispersing SWNTs. Cryogenic-transmission electron microscopy and thermogravimetric analysis techniques are used for the characterization of these dispersions and to complement the UV visible measurements.

Low temperature Fluorescence Study of Crude Petroleum Oils.

by Alan Ryder

P. Owens and A.G. Ryder, Energy & Fuels, 25(11), 5022-5032, (2011).

We have studied the low-temperature (133−298 K) fluorescence emission of crude petroleum oils using a combination of... more We have studied the low-temperature (133−298 K) fluorescence emission of crude petroleum oils using a combination of steady-state and time-resolved measurements. This was done to first see if we could generate linear correlations between oil composition information and the fluorescence measurements, and second to better understand how static and dynamic quenching affect fluorescence emission. It was observed that the fluorescence intensity and lifetime of the crude oils increased rapidly with decreasing temperature down to the freezing point and then either remained constant or surprisingly began to decrease slightly. These changes could not be correlated accurately with the compositional data available. However, despite the very large variations in sample composition, it was found that these lifetime-temperature changes followed simple Arrhenius and Eyring behavior. For the cold liquid phase, an Arrhenius model enabled the calculation of an intrinsic lifetime, the magnitude of which was inversely related to the degree of static quenching. The low values of the calculated activation energies (4.6 to 19.2 kJmol−1) implied that in the liquid phase, non-radiative decay was primarily diffusion based quenching. At the lowest temperatures, when all samples have solidified, the lifetime data followed Eyring like behavior, giving typical enthalpy and entropy values of −1 kJmol−1 and from −67 to −93 JK−1mol−1 respectively. The Eyring model was used to describe the non-radiative decay mechanism arising from vibrational coupling from the fluorophores to the surrounding matrix. This modeling of the temperature dependence of fluorescence lifetime has provided a clearer, quantitative picture of the fluorescence quenching processes in crude petroleum oils.

Measuring the micro-polarity and hydrogen-bond donor/acceptor ability of thermoresponsive N-isopropylacrylamide/N-tert-butylacrylamide copolymer films using solvatochromic indicators.

by Alan Ryder

B. Szczupak, A.G. Ryder, D.M. Togashi, Y.A. Rotchev, A. Gorelov, and T.J. Glynn, Applied Spectroscopy, 63(4), 442-449, (2009).

Thin polymer films are important in many areas of biomaterials research, biomedical devices, and biological... more Thin polymer films are important in many areas of biomaterials research, biomedical devices, and biological sensors.  The accurate, in-situ, measurement of multiple physicochemical properties of thin polymer films is critical in understanding biocompatibility, polymer function, and performance.  In this work we demonstrate a facile, spectroscopic methodology for accurately measuring the micro-polarity and hydrogen-bond donor/acceptor ability for a series of relatively hydrophilic thermoresponsive copolymers.  The micro-polarity of the N-isopropylacrylamide (NIPAM) and N-tert-butylacrylamide (NtBA) co-polymers was evaluated by means of the ET(30), alpha, beta, and pi* empirical solvatochromic polarity parameters.  The data shows that increasing the NtBA fraction in the dry copolymer film reduces polarity and hydrogen-bonding ability.  Within the Kamlet-Taft polarity framework, the NIPAM/NtBA copolymer films are strong hydrogen-bond acceptors, strongly dipolar/polarisable, and rather moderate hydrogen-bond donors.  This characterization provides a more comprehensive physicochemical description of polymers, which aids the interpretation of film performance.  Comparison of the measured ET(30) values with literature data for other water-soluble polymers show that dry NIPAM/NtBA copolymers are slightly more polar than poly(ethylene oxide), less polar than polyvinylalcohol, and approximately the same polarity as poly(N-vinyl-2-pyrrolidone).  These findings indicate that this spectroscopic method is a facile, rapid, and non-destructive methodology for measuring polymer properties in-situ, suitable for most biomaterials research laboratories.