Development of a Multiwavelength Thermal Lens Spectrophotometer Based on an Acousto-Optic Tunable Filter as a Polychromator

1994 ◽  
Vol 48 (1) ◽  
pp. 101-106 ◽  
Author(s):  
Chieu D. Tran ◽  
Ricardo J. Furlan ◽  
Jian Lu
Keyword(s):  
Detection Limit ◽  
Thermal Lens ◽  
Laser Light ◽  
Limit Of Detection ◽  
Tunable Filter ◽  
Lanthanide Ions ◽  
Probe Laser ◽  
Excitation Beam ◽  
Thermal Lens Signal ◽  
Rf Signals

Instrumentation development of a novel multiwavelength thermal lens spectrophotometer which has the capability of achieving truly multiwavelength excitation is described. The spectrophotometer is based on a new concept by which the sample is excited by multiwavelength excitation beams simultaneously, not sequentially as in previously reported multiwavelength thermal lens apparatus. This was accomplished by use of the acousto-optic tunable filter (AOTF) as a polychromator. Specifically, four different rf signals were simultaneously applied to the filter to enable it to diffract incident multiline laser light into a beam which contained four different wavelengths. This multiwavelength beam was then used to excite the sample, and the corresponding thermal lens signal was measured by a He-Ne probe laser. Compared with other multiwavelength thermal lens instruments, this all-solid-state thermal lens spectrophotometer has advantages that include its ability to simultaneously analyze multicomponent samples in microsecond times scale, without the need for any prior sample preparation. With this apparatus and with the use of a 12-mW multiwavelength excitation beam, the limit of detection for four-component (lanthanide ions) samples is estimated to be 10−6 cm−1, which is similar to the detection limit obtained for one-component samples with the use of a single-wavelength system.

Enhancement of the thermal lens signal induced by sample matrix absorption of the probe laser beam

2002 ◽  
Vol 41 (27) ◽  
pp. 5814 ◽  
Author(s):  
Victor I. Grishko ◽  
Chieu D. Tran ◽  
Walter W. Duley
Keyword(s):  
Laser Beam ◽  
Thermal Lens ◽  
Probe Laser ◽  
Sample Matrix ◽  
Probe Laser Beam ◽  
Thermal Lens Signal

Dual-Beam Thermal Lens Measurement of Condensed-Phase Sample at CO2 Laser Wavelengths: Detection of Octadecanoic Acid in Carbon Tetrachloride

1994 ◽  
Vol 48 (12) ◽  
pp. 1457-1460 ◽  
Author(s):  
Mladen Franko ◽  
Dane Bicanic ◽  
Zoltán Bozóki ◽  
Henk Jalink
Keyword(s):  
Laser Radiation ◽  
Detection Limit ◽  
Thermal Lens ◽  
Limit Of Detection ◽  
Octadecanoic Acid ◽  
Straight Chain ◽  
Dual Beam ◽  
Phase Sample ◽  
Thermal Lens Effect ◽  
First Time

Detection of monobasic, straight-chain saturated fatty acid (octadecanoic C18:0) in CCl4, based on the thermal lens effect after excitation by CO2 laser radiation at 934.9 cm−1, is described for the first time. The achieved limit of detection (LOD = 0.3%) is comparable to that of the transmission infrared technique. Possibilities for further improvements in sensitivity and detection limit are also discussed.

Linear and Nonlinear Thermal Lens Signal of the (Δν = 6) C–H Vibrational Overtone of Naphthalene in Liquid Solutions of n-Hexane

2018 ◽  
Vol 73 (12) ◽  
pp. 1380-1387
Author(s):  
Parashu R. Nyaupane ◽  
Marlon Diaz ◽  
Ann Barton ◽  
Carlos E. Manzanares
Keyword(s):  
Mole Fraction ◽  
Thermal Lens ◽  
Nonlinear Behavior ◽  
Laser Wavelength ◽  
Probe Laser ◽  
Vibrational Overtone ◽  
Thermal Lens Signal ◽  
Pump And Probe ◽  
Liquid Solutions ◽  
Integrated Intensity

The thermal lens technique is applied to vibrational overtone spectroscopy of solutions of naphthalene (C10H8) in liquid hexane. The C–H fifth vibrational (Δν = 6) overtone spectrum of C10H8 is detected at room temperature for mole fractions from 0.08 to 19 × 10−6 using n-C6H14 as solvent. By detecting the absorption band in a 19 ppm (parts per million) solution, the peak absorption of the signal is approximately (2.2 ± 0.3) × 10−7 cm−1. A plot of normalized integrated intensity as a function of the mole fraction of naphthalene in solution reveals a dependence of the magnitude of the signal with the probe laser wavelength. If the wavelength of the probe laser is 568 nm, the thermal lens signal (TLS) is linear as a function of the mole fraction of the solution. When the wavelength of the probe laser is 488 nm, the TLS is nonlinear as a function of the concentration. Three different models of nonlinear absorption are discussed. A two-color absorption model that includes the simultaneous absorption of the pump and probe lasers could explain the enhanced magnitude and the nonlinear behavior of the TLS for solutions of mole fraction < 0.1%.

Continuous-Wave-Laser versus Pulsed-Laser Excitation for Crossed-Beam Photothermal Detection in Small Volume Applications: Comparative Features

2005 ◽  
Vol 59 (9) ◽  
pp. 1103-1108 ◽  
Author(s):  
Joseph Georges
Keyword(s):  
Thermal Lens ◽  
Small Volume ◽  
Continuous Wave ◽  
Laser Excitation ◽  
Pulsed Laser ◽  
Beam Waist ◽  
Continuous Wave Laser ◽  
Excitation Beam ◽  
Cw Laser ◽  
Thermal Lens Signal

Crossed-beam thermal lens spectrometry can be implemented using continuous-wave- (cw) laser or pulsed-laser excitation. In both cases, the signal depends on the position of the sample with respect to the probe beam waist, the size of the excitation beam, the beam-size ratio into the sample, and the power or energy of the excitation beam. However, due to differences in the rate of formation and relaxation of the thermal lens, both methods exhibit distinct key features. Optimization of the experimental setup and understanding the thermal lens signal are more complicated under cw-laser excitation than with pulsed-laser excitation. Unlike that observed under pulsed excitation, the effect of the excitation beam waist, of the sample size, and of the flow rate are closely related to the effective size of the thermal element and depend on the chopping frequency. Although the intrinsic sensitivities are almost the same, the performance can significantly differ depending on the chopping frequency or pulse repetition rate, which should be high enough to allow fast data collection and efficient signal averaging.

Investigation of Micellar Effects in Thermal Lens Spectrophotometry

1990 ◽  
Vol 44 (1) ◽  
pp. 122-127 ◽  
Author(s):  
Joseph Georges ◽  
Jean-Michel Mermet
Keyword(s):  
Optical Properties ◽  
Thermal Lens ◽  
Formation Rate ◽  
Thermal Lensing ◽  
Micellar Solutions ◽  
Enhanced Fluorescence ◽  
Excitation Beam ◽  
Thermal Lens Signal ◽  
Double Beam ◽  
Aqueous Micellar Solutions

The effect of micellar solutions in thermal lens spectrophotometry was investigated. Several aspects of the thermal lens signal including the formation rate and the relaxation of the thermal lens were compared in various neat solvents and in aqueous micellar solutions. The experiments were performed with a double-beam thermal lens apparatus based upon a pulsed-dye laser as the excitation beam and a He-Ne laser as the probe beam. The results show that, if micellar solutions can be used to solubilize hydrophilic species in solvents having better thermo-optical properties than water, they do not provide sensitive modifications of the thermo-optical properties of water. The absence of micellar effect in thermal lensing, in comparison to the well-known micellar enhanced fluorescence, is discussed with respect to the size of micelles and micellar dynamics, the photophysical processes associated with thermal lensing, and the time dependence of the thermal lens signal.

Microscopic FCA System for Depth-Resolved Carrier Lifetime Measurement in SiC

2018 ◽  
Vol 924 ◽  
pp. 269-272 ◽  
Author(s):  
Shinichi Mae ◽  
Takeshi Tawara ◽  
Hidekazu Tsuchida ◽  
Masashi Kato
Keyword(s):  
Carrier Lifetime ◽  
Laser Light ◽  
Probe Laser ◽  
Free Carrier Absorption ◽  
Cross Sectional ◽  
Lifetime Measurements ◽  
Control Distribution ◽  
System A ◽  
Excitation Laser ◽  
Carrier Absorption

For high voltage SiC bipolar devices, carrier lifetime is an important parameter, and for optimization of device performance, we need to control distribution of the carrier lifetime in a wafer. So far, there have been limited systems for depth-resolved carrier lifetime measurements without cross sectional cut. In this study, we adopted a free carrier absorption technique and made local overlapping of the probe laser light with excitation laser light to develop depth-resolved carrier lifetime measurements. We named the developed system a microscopic FCA system and demonstrated measurement results for samples with and without intentional carrier lifetime distribution.

Two Orders of Magnitude Improvement in the Detection Limit of Droplet-Based Micro-Magnetofluidics with Planar Hall Effect Sensors

2021 ◽  
Vol 6 (1) ◽  
pp. 47
Author(s):  
Julian Schütt ◽  
Rico Illing ◽  
Oleksii Volkov ◽  
Tobias Kosub ◽  
Pablo Nicolás Granell ◽  
...  
Keyword(s):  
Detection Limit ◽  
Hall Effect ◽  
State Of The Art ◽  
Limit Of Detection ◽  
Research Field ◽  
High Throughput Analysis ◽  
Planar Hall Effect ◽  
Biologically Relevant ◽  
Sensing Platform ◽  
Order Of Magnitude

The detection, manipulation, and tracking of magnetic nanoparticles is of major importance in the fields of biology, biotechnology, and biomedical applications as labels as well as in drug delivery, (bio-)detection, and tissue engineering. In this regard, the trend goes towards improvements of existing state-of-the-art methodologies in the spirit of timesaving, high-throughput analysis at ultra-low volumes. Here, microfluidics offers vast advantages to address these requirements, as it deals with the control and manipulation of liquids in confined microchannels. This conjunction of microfluidics and magnetism, namely micro-magnetofluidics, is a dynamic research field, which requires novel sensor solutions to boost the detection limit of tiny quantities of magnetized objects. We present a sensing strategy relying on planar Hall effect (PHE) sensors in droplet-based micro-magnetofluidics for the detection of a multiphase liquid flow, i.e., superparamagnetic aqueous droplets in an oil carrier phase. The high resolution of the sensor allows the detection of nanoliter-sized superparamagnetic droplets with a concentration of 0.58 mg cm−3, even when they are only biased in a geomagnetic field. The limit of detection can be boosted another order of magnitude, reaching 0.04 mg cm−³ (1.4 million particles in a single 100 nL droplet) when a magnetic field of 5 mT is applied to bias the droplets. With this performance, our sensing platform outperforms the state-of-the-art solutions in droplet-based micro-magnetofluidics by a factor of 100. This allows us to detect ferrofluid droplets in clinically and biologically relevant concentrations, and even in lower concentrations, without the need of externally applied magnetic fields.

scholarly journals Investigation into the Potential Migration of Nanoparticles from Laponite-Polymer Nanocomposites

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 723 ◽  
Author(s):  
Johannes Bott ◽  
Roland Franz
Keyword(s):  
Laser Light ◽  
Limit Of Detection ◽  
Surfactant Solution ◽  
Ethylene Vinyl Acetate ◽  
Field Flow Fractionation ◽  
Migration Test ◽  
Asymmetric Flow ◽  
Worst Case ◽  
Test Conditions ◽  
Migration Potential

In this study, the migration potential of laponite, a small synthetic nanoclay, from nanocomposites into foods was investigated. First, a laponite/ethylene vinyl acetate (EVA) masterbatch was compounded several times and then extruded into thin low-density polyethylene (LDPE) based films. This way, intercalation and partial exfoliation of the smallest type of clay was achieved. Migration of laponite was investigated using Asymmetric Flow Field-Flow Fractionation (AF4) with Multi-Angle Laser Light Scattering (MALLS) detection. A surfactant solution in which laponite dispersion remained stable during migration test conditions was used as alternative food simulant. Sample films with different loadings of laponite were stored for 10 days at 60 °C. No migration of laponite was found at a limit of detection of 22 µg laponite per Kg food. It can be concluded that laponite (representing the worst case for any larger structured type of clay) does not migrate into food once it is incorporated into a polymer matrix.

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