Spectroscopy Measurement Techniques Research Articles

Double-layered nitrocellulose membrane sample holding technique for THz and FIR spectroscopic measurements.

In terahertz (THz) and far-infrared (FIR) spectroscopic measurements, weak absorption spectral features due to small quantities of test sample can be masked by undesirable etalon fringe artifacts caused by multiple reflections within a pellet or a rigid sample holder. A double-layered nitrocellulose (NC) membrane structure is proposed in this paper as an alternative holder for small quantities of either dry or wet pure (no added polyethylene powder) samples with significantly reduced etalon artifacts. Utilizing a THz time-domain spectroscopy system and a synchrotron source, we demonstrate the performance of the NC structure across the THz/FIR spectrum, benchmarking against pellets holding similarly small quantities of α-lactose powder either with or without different grades of polyethylene powder. With only pure samples to consider, scattering can be mitigated effectively in NC-derived spectra to reduce their baselines.

About the development of databases in thermal analysis

Comparing own measurement values with the literature or textbook data is an established procedure for the correct interpretation, and final evaluation of the results obtained. For some spectroscopic measurement techniques such as mass spectrometry or Fourier transform infrared spectroscopy, online libraries have long been established, which allow for library searches within the evaluation software and for comparisons of the measurement data with spectra collections archived in databases. These are either available on the Internet free of charge or can be purchased from instruments suppliers or scientific organizations. For the methods of thermal analysis, such as thermogravimetry, dilatometry, or differential scanning calorimetry, such software-based libraries had not been available thus far. The “Identify” database of the NETZSCH Proteus ® evaluation software now offers—for the first time—the ability to conduct software-based library comparisons in thermal analysis. With the example of two polymer samples, it will be shown that identification of both pure substances and mixtures can be carried out with the help of “Identify.”

TuW-4 Near-Infrared Spectroscopy Measurement Technique of Brain Activity and Its Application to Human-Machine Interfaces

TuW-4 Near-Infrared Spectroscopy Measurement Technique of Brain Activity and Its Application to Human-Machine Interfaces

Determination of absolute quantum yields of luminescing nanomaterials over a broad spectral range: from the integrating sphere theory to the correct methodology

Determination of fluorescence or photo- and electro-luminescence quantum yield (QY) is of increasing importance for standardization of novel light-emitting materials like semiconductor quantum dots. The most straightforward spectroscopic QY measurement technique is based on the exploitation of an integrating sphere (IS). We propose a compact set-up and procedure for reliable measurements of QY over a broad excitation spectral range which uses excitation by light-emitting diodes. Starting from the general IS theory we show that (i) a variable excitation pattern has no fatal influence on the QY determination and (ii) a simple two-configuration experiment is an adequate basis of the correct experimental procedure. Then we give guidelines for the QY experiment and calculations as well as a few practical examples and error analysis. Our comprehensive description of absolute luminescence QY techniques based on the IS theory has a general applicability not restricted to the apparatus described in this paper.

Spectral Signatures Identifying Instrument on Spectroscopic Measurement Technique for Water Quality Monitoring

Spectral measurement is an important technology for measuring algal-chlorophyll in surface water. This paper provides a possibility of spectral signatures in the visible and near infrared, associated with experiments could be conduct to use proposed devise for outdoors in water environments. The overall objective of this study was to use development of micro controller based Spectrometer for finding possible spectral regions in which chlorophyll-a (Chl-a) could be identified so as to assist the assessment and monitoring of water quality spectrometric method. The main target is to develop very low cost effective with mobility and to get current data by accessing remotely. This study based on the application of linear regression analysis between the mean reflectance values (proposed Micro controlled visible Spectrometer-MVSM-C10988MA-01) across the spectrum and the concentrations of chlorophyll-a (μg/L) acquired simultaneously in situ measurement on the same day and time in the Ibaraki University Test Pond in Japan.

Effect of Addition TiO<sub>2</sub> on Bi<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub> Glasses

Bismuth titanium borate glasses in compositions xTiO2 : (30-x)Bi2O3 : 70B2O3 (with x is in mol%, varying from 0% to 10%) were fabricated by the conventional melt quenching technique. The effect of TiO2 on the physical and spectroscopic properties of bismuth borate glasses have been carried out by means of density and UV-Visible spectroscopy measurement techniques. The density and molar volume of all glasses are found to change depend on TiO2 substitution. The fundamental absorption edges for all glasses have been identified using the theory proposed by Davis and Mott. The optical band gap (Eg) is found to decrease with increase in TiO2 content.

Quantitative analysis of tea using ytterbium‐based internal standard near‐infrared spectroscopy coupled with boosting least‐squares support vector regression

The present study demonstrated the possibility of utilizing the ytterbium (Yb)‐based internal standard near‐infrared (NIR) spectroscopic measurement technique coupled with multivariate calibration for quantitative analysis of tea, including total free amino acids and total polyphenols in tea. Yb is a rare earth element aimed to compensate for the spectral variation induced by the alteration of sample quantity during the spectral measurement of the powdered samples. Boosting was invoked to be combined with least‐squares support vector regression (LS‐SVR), forming boosting least‐squares support vector regression (BLS‐SVR) for the multivariate calibration task. The results showed that the tea quality could be accurately and rapidly determined via the Yb‐based internal standard NIR spectroscopy combined with BLS‐SVR method. Moreover, the introduction of boosting drastically enhanced the performance of individual LS‐SVR, and BLS‐SVR compared favorably with partial least‐squares regression. Copyright © 2013 John Wiley & Sons, Ltd.

Optical constants and spatial uniformity of thermally grown oxide layer of custom, induced-junction, silicon photodiodes for a predictable quantum efficient detector

We have investigated the optical properties of self-induced inversion-layer silicon photodiodes using spectroscopic ellipsometric measurement techniques. We report a self-consistent data set and dispersion relation for the optical constants of the thermally grown oxide layer. The oxide layer thickness and spatial uniformity of a series of custom manufactured 22 mm × 11 mm rectangular diodes are evaluated. These photodiodes are used in a light trapping arrangement and exhibit predictable quantum efficiency and thus, predictable spectral responsivity. For comparison, we report measurements of the absolute spatial uniformity of the oxide layer on commercial “S6337” and “S1337” radiometric quality photodiodes.

Measurement of energy barriers to conformational change in poly-l-glutamic acid by temperature-derivative spectroscopy

Energy barriers in kinetics are typically determined by measuring the rate as a function of temperature. We have used an alternative and complementary technique, temperature-derivative spectroscopy, to characterize folding of poly-l-glutamic acid in response to a change in pH. After the solution pH is changed photolytically at low temperature (150K) using a photogenerating acid, the solution is warmed while monitoring the helix–coil transition by its infrared absorption. At high initial pH, the secondary structure change occurs at 180K. If the initial pH is near 6, helix formation occurs near 190K. The results are interpreted in terms of the pre-exponential factor and enthalpy barrier for protein folding. Because the pH change is extrinsic to the system under study, this technique enables temperature-derivative spectroscopy to be used with any phenomenon that is pH dependent and with a wide range of spectroscopic measurement techniques.

Tungsten L transition line shapes and energy shifts resulting from ionization in warm dense matter

Spectra of the W L transitions in the energy range 8–12 keV from warm dense plasmas generated by the Naval Research Laboratory's Gamble II pulsed power machine were recorded by a newly developed high-resolution transmission-crystal X-ray spectrometer with ±2 eV accuracy. The discharges have up to 2 MV voltage, 0.5 MA current, and produce up to 2.4 MJ/cm−3 energy density. The plasma-filled rod pinch (PFRP) diode produces a plasma with Ne ≈ 1022 cm−3 and Te ≈ 50 eV during the time of maximum X-ray emission. By analyzing the line shapes, it was determined that the Lβ2 inner-shell transition from the 4d5/2 level was shifted to higher energy by up to 23 eV relative to nearby Lβ transitions from n = 3 levels. In addition, the Lβ2 transition was significantly broader and asymmetric compared to the n = 3 transitions. The energy shift of the Lβ2 transition results from the ionization of electrons outside the 4d shell that perturbs the transition energies in the ions to higher values. The increased line width and asymmetry result from unresolved transitions from a range of ionization states up to +28. The ionization distribution was determined by comparison of the measured energy shifts and widths to calculated transition energies in W ions, and the ionization was correlated with Gamble discharge parameters such as the anode type and the high voltage delay time. This work demonstrates a new hard X-ray spectroscopic diagnostic technique for the direct measurement of the ionization distribution in warm dense plasmas of the heavy elements W through U that is independent of the other plasma parameters and does not require interpretation by hydrodynamic, atomic kinetics, and radiative simulation codes.

20901 分光計測と筒内可視化を用いた過給SI機関におけるノッキング現象の解析(GS-17【エンジン(1)】)

Against a background of rising CO_2 emissions, there is a need for further improvement in fuel economy of spark ignition (SI) engines. One hurdle to interfere improvement in fuel economy of SI engine is knocking. The knocking of SI engines is auto-ignition at unburned gas in the end of combustion chamber that caused various negative impacts to engine In this study, auto-ignition behavior in an SI engine was investigated by using the in-cylinder visualization and spectroscopic measurement technique. The test fuels used were a 80 RON primary reference fuel (n-heptane + iso-octane). Light absorption spectroscopic technique was applied to investigate the behavior of formaldehyde (HCHO) m the interval from the occurrence of a cool flame to auto-ignition. The results showed the occurrence of cool flame was delayed by supercharging, and auto-ignition timing was advanced.

High-pressure carbon dioxide uptake for porous organic cages: comparison of spectroscopic and manometric measurement techniques

A chemoselective spectroscopic method for measuring CO2 sorption isotherms at pressures up to 14 MPa (140 bar) is validated against manometric measurements and molecular simulations, giving insights into the preferred sorption sites in various crystalline porous organic cages.

Quantitative near infrared spectroscopic analysis of Q‐Switched Nd:YAG treatment of generalized argyria

Generalized argyria is a blue-gray hyperpigmentation of the skin resulting from ingestion or application of silver compounds, such as silver colloid. Case reports have noted improvement after Q-Switched Neodymium-Yttrium Aluminum Garnet laser (1,064 nm QS Nd:YAG) laser treatment to small surface areas. No reports have objectively monitored laser treatment of generalized argyria over large areas of skin, nor have long-term outcomes been evaluated. An incremental treatment plan was developed for a subject suffering from argyria. A quantitative near infrared spectroscopic measurement technique was employed to non-invasively analyze tissue-pigment characteristics pre- and post-laser treatment. Post-treatment measurements were collected at weeks 1, 2, 3, and 4, and again at 1 year. Immediate apparent removal of pigment was observed with 1 Q-switched 1,064 nm Nd:YAG laser treatment (3-6 mm spot; 0.8-2 J/cm(2) ) per area. Entire face, neck, upper chest, and arms were treated over multiple sessions. Treatments were very painful and general anesthesia was utilized in order to treat large areas. Near-infrared spectroscopy was used to characterize and quantify the concentration of silver particles in the dermis based on the absorption features of the silver particles as well as the optical scattering effects they impart. We were able to estimate that there was, on average, 0.042 mg/ml concentration of silver prior to treatment and that these levels went below the minimum detectable limit of the instrument post-treatment. There was no recurrence of discoloration over the 1-year study period. QS 1,064 nm laser treatment of argyria is a viable method to restore normal skin pigmentation with no evidence of recurrence over study period. Quantitative spectroscopic measurements: (1) confirmed dyspigmentation was due to silver, (2) validated our clinical assessment of no recurrence up to 1-year post-treatment, and (3) indicated no collateral tissue damage with treatments.

Broadband mid-infrared frequency upconversion and spectroscopy with an aperiodically poled LiNbO_3 waveguide

We convert a mid-infrared frequency comb to near-infrared wavelengths through sum-frequency generation with a 1.064 μm CW laser in an aperiodically poled ZnO:LiNbO(3) waveguide. Upconversion of light in the range of 2.5-4.5 μm to 0.76-0.86 μm is demonstrated in a single device, and the efficiency of the conversion is measured across this bandwidth. We additionally characterize the spatial mode of the upconverted light. We then use this upconversion technique to detect and resolve individual lines from a methane gas sample with a common near-infrared optical spectrum analyzer. The stability of the spectrum of the upconverted light is analyzed with the goal of evaluating this technique for precise spectroscopic measurements.

Exploiting few mode-fibers for optical time-stretch confocal microscopy in the short near-infrared window

Dispersive fiber is well-regarded as the most viable candidate for realizing efficient optical time-stretch process--an ultrafast spectroscopic measurement technique based on the wavelength-to-time mapping via group velocity dispersion (GVD). Despite optical time-stretch has been anticipated to benefit a wide range of high-throughput biomedical diagnoses, the lack of commercially-available dispersive fibers which can operate in the "biomedically-favorable" short near-infrared (~800 nm - 1100 nm) range hinders practical time-stretch-based biomedical spectroscopy and microscopy. We here explore and demonstrate the feasibility of using the standard telecommunication single-mode fibers (e.g. SMF28 and dispersion compensation fiber (DCF)) as few-mode fibers (FMFs) for optical time-stretch confocal microscopy in the 1 μm range. By evaluating GVD of different FMF modes and thus the corresponding time-stretch performances, we show that the fundamental modes (LP(01)) of SMF28 and DCF, having sufficiently high dispersion-to-loss ratios, are particularly useful for practical time-stretch spectroscopy and microscopy at 1 μm, without the need for the specialty 1 μm SMF. More intriguingly, we also show that the higher-order FMF modes (e.g. LP(11)) could be excited and utilized for time-stretch imaging. Such additional degree of freedom creates a new avenue for optimizing and designing the time-stretch operations, such as by tailored engineering of the modal-dispersion as well as the GVD of the individual FMF modes.

Modification in structural and optical properties of ZnO, CeO2 doped Al2O3–PbO–B2O3 glasses

The structural and optical analysis of glasses is carried out by XRD, FTIR, density and UV visible spectroscopic measurement techniques. XRD results have confirmed the glassy nature of the samples. The FTIR spectral analysis reveals that with the combined presence of ZnO and CeO2 contents in Al2O3–PbO–B2O3 glasses, more BO3 groups are transformed into BO4. The optical analysis reveals that optical band gap energy decreases more for CeO2–ZnO–Al2O3–PbO–B2O3 glasses (from 2.28 to 1.84eV). The presence of CeO2 and ZnO in the glass samples causes more compaction of the borate network due to the formation of more BO4 groups and the presence of ZnO4 groups, which results an increase in density, refractive index and decrease of molar volume.

Photonic sensing of the atmosphere by absorption spectroscopy

Chemically reactive atmospheric species play a crucial role in tropospheric processes which affect regional air quality and global climate change. Contrary to long-lived species such as greenhouse gases, interference-free accurate and precise concentration assessments of strongly reactive short-lived species represent a real challenge. In this paper, we report on the recent progress in spectroscopic instrumental developments for monitoring of OH, NO3, HONO and NO2 by using modern photonic sources (Quantum Cascade Laser, distributed feedback diode laser, light emitting diode) in conjunction with high-sensitivity spectroscopic measurement techniques such as multi-pass cell based long optical path length absorption spectroscopy, wavelength-modulation enhanced off-axis integrated cavity output spectroscopy, Faraday rotation spectroscopy, incoherent broadband cavity enhanced absorption spectroscopy. The main techniques available for routine atmospheric measurements of OH, NO3 and HONO are overviewed, in comparison with the emerging modern photonic spectroscopy techniques.

Effect of WO3 on structural and optical properties of PbO-B2O3 glasses

Glass samples of compositions xWO3-(30-x) PbO-70B2O3 with x varying from 0 to 10 mol percent are prepared using the melt–quench technique. The structural and optical analysis of glasses is carried out by using X-ray diffraction, Fourier transform infrared (FTIR), density, and ultraviolet-visible spectroscopic measurement techniques. FTIR analysis indicates the transformation of structural units of BO3 into BO4 and formation of WO4 units with W–O–W vibration are observed with WO3 doping. Decrease of band gap from 2.89 to 2.22 eV has been observed and discussed. This decrease in band gap causes an approach to semiconducting behavior with WO3 doping. It shows that WO3 causes more compaction of the borate network by breaking the bonds between trigonal elements, which results in the decrease of optical band gap energy and increase of density.

PH-responsive flocculation and dispersion behavior of Janus particles in water

Gold was vacuum-deposited on one side of 6-μm-diameter SiO2 particles to prepare Janus particles (JPs). A thiol-terminated pH-responsive polymer (pAaH-SH), prepared via reversible addition–fragmentation chain transfer (RAFT) -controlled radical polymerization, was immobilized on the gold surface of the JPs as confirmed by attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy measurement techniques. A fluorescein-labeled polymer (p(AaH/Flu)-SH) was also prepared via RAFT, and immobilization of p(AaH/Flu)-SH only on the gold surface of the JPs was confirmed by fluorescence microscopy observations. The flocculation and dispersion behavior of pAaH-SH-grafted JPs was observed with an optical microscope and was found to be varied with the solution pH.

Spectroscopic study of ZnO doped CeO 2–PbO–B 2O 3 glasses

Glass samples of compositions xZnO– xCeO 2–(30− x)PbO–(70− x)B 2O 3 with x varying from 2% to 10% mole fraction are prepared by the melt quench technique. The structural and optical analysis of glasses is carried out by XRD, FTIR, density and UV–visible spectroscopic measurement techniques. The FTIR spectral analysis indicates that with the addition of ZnO contents in glass network, structural units of BO 3 are transformed into BO 4. It has been observed in our previous work that band gap decreases from 2.89 to 2.30 eV for CeO 2–PbO–B 2O 3 glasses with cerium content varying from 0% to 10% [Gurinder Pal Singh, Davinder Paul Singh, Physica B 406(3) (2011) 640–644]. With the incorporation of zinc in CeO 2–PbO–B 2O 3 glasses, the optical band gap energy decreases further from 2.38 to 2.03 eV. This causes more compaction of the borate network, which results in an increase of density (3.39–4.02 g/cm 3). Transmittance shows that ZnO in glass samples acts as a reducing agent thathelps to convert Ce 4+→Ce 3+ ions.