Photothermal Beam Deflection Spectroscopy Research Articles

The Effect of Curing Temperature and Thickness of Polybutyl Methacrylate Siloxane Coatings on the Corrosion Protection of Structural Steel S355

This study aimed to determine the effects of coating thickness and curing temperature on the properties of a polybutyl methacrylate-siloxane coating deposited on structural steel S355. First, the thermal properties of the sol as a function of temperature were investigated using thermogravimetric analysis coupled with mass spectrometry and differential scanning calorimetry. After coating deposition on structural steel S355 using a dip-coating process, the coating composition and porosity were evaluated using Fourier transform infrared spectroscopy and photothermal beam deflection spectroscopy. In the second part, coating thickness, topography, and corrosion properties were studied as functions of withdrawal rate during deposition. The corrosion properties of variously prepared coatings were evaluated using electrochemical impedance measurements in 3.5 wt.% NaCl and salt spray testing according to the ASTM B117 standard. An elevated curing temperature (at 150 °C) of the polybutyl methacrylate siloxane sol-gel coating impairs greater crosslinking and lower porosity, while the optimal thickness of 4 μm is achieved with the appropriate withdrawal rate to obtain a homogeneous, defect-free surface. Under these optimal conditions, the protection of structural steel against corrosion in a chloride environment lasting for more than 6 months can be achieved.

Investigations of the Thermal Parameters of Hybrid Sol–Gel Coatings Using Nondestructive Photothermal Techniques

This article presents the results of comparative investigations of thermal parameters of hybrid sol–gel coatings (named TMZ) prepared from tetraethyl orthosilicate and organically modified 3-methacryloxypropyltrimethoxysilane. The coatings were prepared with the addition of zirconium(IV) tetrapropoxide chelated with methacrylic acid. Two series of samples were investigated: the first series, TMZ-I, TMZ-II and TMZ-III, with different amounts of zirconium, and the second series, TMZ-I/Ce, TMZ-II/Ce and TMZ-III/Ce, with the addition of cerium nitrate. The influence of the amount of zirconium and cerium on the thermal parameters of the sol–gel coatings was next analyzed. Two non-destructive and photothermal techniques were used for this purpose: photothermal radiometry (PTR) and beam deflection spectroscopy (BDS). The thermal diffusivity and conductivity of the coatings were extracted from the frequency experiments and are presented and discussed. The two-layer model was applied to interpret the photothermal spectra. The results obtained using these two techniques are compared and discussed.

Determination of Dissolved Iron Redox Species in Freshwater Sediment using DGT Technique Coupled to BDS

In this work we have developed a novel method for determination of iron redox species by the use of diffusive gradients in thin-film (DGT) technique coupled to photothermal beam deflection spectroscopy (BDS). The combination of both methods achieved low limit of detection (LOD) of 0.14 μM for Fe (II) ions. The total Fe concentration determined in the Vrtojbica river sediment (Slovenia, Rožna Dolina, 5000 Nova Gorica) was 49.3 μgL-1. The Fe (II) and Fe (III) concentration amounted to 12.8 μgL-1 and 39.9 μgL-1, respectively. Such an approach opens new opportunities for monitoring the content of iron species in natural waters and sediments and provides highly sensitive chemical analysis and an accurate qualitative and quantitative characteristic of the materials under study.

Transparent Photocatalytic Thin Films on Flexible Polymer Substrates

Self-cleaning and/or photocatalytic films on polymer substrates have found numerous applications during the past decades. However, the common demand for high-temperature post synthesis treatment limits the application to temperature resistant substrates only. Herein, we prepared self-cleaning photocatalytic films on four thermosensitive polymeric substrates: polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and acryl coated polyester (PES) fabric (D2) with poly(vinylidene fluoride) (PVDF) containing lacquer (D1). TiO2 was prepared via a low-temperature sol-gel process using titanium(IV) isopropoxide and zirconium(IV) butoxide as precursors with various loading levels of Zr; 0, 5, 10, and 20 mol.%, and deposited on the substrates by using a SiO2 binder in form of thin films (ca. 200 nm thick) via dip-coating. The films were characterized by SEM, hardness test, UV-Vis, photothermal beam deflection spectroscopy, and IR spectroscopy, while photocatalytic activity was measured by the fluorescence-based method of the terephthalic acid probe and wetting by contact angle measurements. Films containing 10 mol.% of Zr showed the best compromise regarding photocatalytic activity and mechanical stability while from substrates point of view PVC performed the best, followed by PMMA, D1, and D2. The beneficial role of SiO2 binder was not only guaranteeing excellent mechanical stability, but also to prevent the D1 polymer from deterioration; the latter was found to be labile to long-term solar-light exposure due to degradation of the top PVDF layer.

Photothermal Beam Deflection Spectroscopy for the Determination of Thermal Diffusivity of Soils and Soil Aggregates

Photothermal beam deflection spectroscopy (BDS) with a red He–Ne laser (632.8 nm, 35 mW) as an excitation beam source and a green He–Ne laser (543.1 nm, 2 mW) as a probe was used for estimating thermal diffusivity of several types of soil samples and individual soil aggregates with small surfaces (2 × 2 mm). It is shown that BDS can be used on demand for studies of changes in properties of soil entities of different hierarchical levels under the action of agrogenesis. It is presented that BDS clearly distinguishes between thermal diffusivities of different soil types: Sod-podzolic [Umbric Albeluvisols, Abruptic], 29 ± 3; Chernozem typical [Voronic Chernozems, Pachic], 9.9 ± 0.9; and Light Chestnut [Haplic Kastanozems, Chromic], 9.7 ± 0.9 cm2·h−1. Aggregates of chernozem soil show a significantly higher thermal diffusivity compared to the bulk soil. Thermal diffusivities of aggregates of Chernozem for virgin and bare fallow samples differ, 53 ± 4 cm2·h−1 and 45 ± 4 cm2·h−1, respectively. Micromonoliths of different Sod-podzolic soil horizons within the same profile (topsoil, depth 10–14 cm, and a parent rock with Fe illuviation, depth 180–185 cm) also show a significant difference, thermal diffusivities are 9.5 ± 0.8 cm2·h−1 and 27 ± 2 cm2·h−1, respectively. For soil micromonoliths, BDS is capable to distinguish the difference in thermal diffusivity resulting from the changes in the structure of aggregates.

A combination of interdisciplinary analytical tools for evaluation of multi-layered coatings on medical grade stainless steel for biomedical applications

In this comprehensive study several analytical techniques were used in order to evaluate multi-layered biomedical surface coatings composed of a drug (diclofenac) and a polymer (chitosan). Such a thorough examination is of paramount importance in order to assure safety and prove efficiency of potential biomedical materials already at the in vitro level, hence leading to their potentially faster introduction to clinical trials.For the first time a novel technique based on thermal diffusivity and conductivity measurements (photothermal beam deflection spectroscopy – BDS) was employed in order to analyse in a non-destructive way the thickness of respective layers, together with their thermal diffusivity and conductivity. In addition to attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), BDS confirmed successive surface layers of the prepared coatings. Scanning electron microscopy and atomic force microscopy were used to examine structural information on the macro- and micro/nano-scale, respectively. Surface hydrophobicity was measured with the contact angle analysis, which clearly showed differences in hydrophobicity between coated and non-coated samples. Considering the targeted application of the prepared coatings (as implant in orthopaedic treatments), the in vitro drug release was analysed spectrophotometrically to examine the coatings potential for a controlled drug release. Furthermore, the material was also tested by electrochemical impedance spectroscopy and cyclic polarisation techniques, which were able to detect even minor differences between the performance of the coated and non-coated materials. As the final test, the biocompatibility of the coatings with human osteoblasts was determined.

The Effect of Cerium Ions on the Structure, Porosity and Electrochemical Properties of Si/Zr-Based Hybrid Sol-Gel Coatings Deposited on Aluminum

This study was focused on the synthesis and characterization of Si/Zr-based hybrid sol-gel coatings with and without the addition of cerium(III) ions. The coatings were deposited on aluminum aiming to act as an effective and ecologically harmless alternative to toxic chromate coatings. The chemical composition, structure, thermal properties and porosity of the non-doped and Ce-doped coatings containing various Zr contents were examined by Raman spectroscopy and photothermal beam deflection spectroscopy. The corrosion properties of the coated aluminum substrates were studied using AC and DC electrochemical methods in 0.1 M NaCl electrolyte solution. Barrier and protecting properties of the coatings were monitored upon long-term immersion in chloride solution using electrochemical impedance spectroscopy. The effect of cerium ions was two-fold: on the formation of a more condensed Si−O−Zr network structure and on the formation of Ce-based deposits, which diminish the rate of cathodic reaction at the coating/metal interface. These effects acted synergistically and resulted in the creation of the coatings with effective barrier and active corrosion protection.

Optimized frequency dependent photothermal beam deflection spectroscopy

In the letter the optimization of the experimental setup for photothermal beam deflection spectroscopy is performed by analyzing the influence of its geometrical parameters (detector and sample position, probe beam radius and its waist position etc) on the detected signal. Furthermore, the effects of the fluid’s thermo-optical properties, for optimized geometrical configuration, on the measurement sensitivity and uncertainty determination of sample thermal properties is also studied. The examined sample is a recently developed CuFeInTe3 material. It is seen from the obtained results, that it is a complex problem to choose the proper geometrical configuration as well as sensing fluid to enhance the sensitivity of the method. A signal enhancement is observed at low modulation frequencies by placing the sample in acetonitrile (ACN), while at high modulation frequencies the sensitivity is higher for measurements made in air. For both, detection in air and acetonitrile the determination of CuFeInTe3 thermal properties is performed. The determined values of thermal diffusivity and thermal conductivity are (0.048 ± 0.002) × 10−4 m2 s−1 and 4.6 ± 0.2 W m−1 K−1 and (0.056 ± 0.005) × 10−4 m2 s−1 and 4.8 ± 0.4 W m−1 K−1 for ACN and air, respectively. It is seen, that the determined values agree well within the range of their measurement uncertainties for both cases, although the measurement uncertainty is two times lower for the measurements in ACN providing more accurate results. The analysis is performed by the use of recently developed theoretical description based on the complex geometrical optics. It is also shown, how the presented work fits into the current status of photothermal beam deflection spectroscopy.

Thermal Properties of Surface-Modified $$\upalpha $$ α - and $$\upvarepsilon $$ ε -Fe $$_{2}\hbox {O}_{3}$$ 2 O 3 Photocatalysts Determined by Beam Deflection Spectroscopy

In this work, a photothermal beam deflection spectroscopy setup is developed and applied for determination of the thermal parameters (thermal diffusivity and thermal conductivity) of $$\upalpha $$ - and $$\upvarepsilon $$ -Fe $$_{2}\hbox {O}_{3}$$ nanodeposits on Si(100) substrates, specifically designed and tested as photocatalysts. It was observed that thermal parameters of the material strongly depend on the sample composition and morphology, which affect also the photocatalytic activity. The correlation between the thermal and photocatalytic properties are critically discussed based on the characteristics of the materials.

Thermodynamic profile for urea photo-release from a N-(2-nitrobenzyl) caged urea compound

Photoactivable bioactive molecules, often termed "caged" compounds, have attracted significant attention as useful tools for photo-regulating enzymatic activity. Here we examine the mechanism associated with photo-release of urea from a caged urea compound, N-(2-nitrobenzyl)urea, using photothermal beam deflection and time-resolved absorption spectroscopy. Photodissociation of the caged urea results in the prompt formation of an aci-nitro intermediate that decays to nitrosobenzaldehyde by releasing urea with the rate constant of 4.5x10(3) s(-1). Appearance of the aci-nitro intermediate is associated with a volume contraction of -13+/-1 mL mol(-1) and a negligible change in enthalpy (DeltaH=6+/-4 kcal mol(-1)). On the microsecond time-scale, the conversion of the aci-nitro intermediate and concomitant release of urea result in a volume expansion of 6+/-2 mL mol(-1) and a negative enthalpy change of -25+/-5 kcal mol(-1). No additional processes were observed on the timescale up to 100 ms suggesting that the breakdown of the aci-nitro intermediate is the rate-limiting step for urea photo-release. These results suggest a similar mechanism for caged urea photo release as determined previously for the caged ATP compound.

Photothermal imaging in 3D surface analysis of membrane drug delivery

Various methods exist for research into the penetration process in the human nail plate and for investigation of dermal drug delivery. Application of spectroscopic methods in this scientific field is gaining importance. However, no method meets all demands of the large variety of applications. An alternative optical technique for the characterisation of samples is the photothermal spectroscopy. Photoacoustic techniques, photothermal radiometry, and photothermal beam deflection spectroscopy (PDS) are non-destructive analytical techniques that take advantage of the so-called photoacoustic and photothermal phenomena. PDS, in conjunction with an appropriate scanner, allows for depth profiling and is a promising technique for studies of three-dimensional drug diffusion into artificial and biological membranes. The objective of this article is to demonstrate the use of PDS imaging for pharmaceutical applications and drug delivery studies, with two experiments being used as examples: the follow-up of lateral dithranol penetration into an artificial membrane and depth-resolved measurement of the distribution of a model drug within a keratin membrane from bovine hoof.

Energetics and kinetics of photosynthetic water oxidation studied by photothermal beam deflection (PBD) experiments

Determination of thermodynamic parameters of water oxidation at the photosystem II (PSII) manganese complex is a major challenge. Photothermal beam deflection (PBD) spectroscopy determines enthalpy changes (ΔH) and apparent volume changes which are coupled with electron transfer in the S-state cycle (Krivanek R, Dau H, Haumann M (2008) Biophys J 94: 1890–1903). Recent PBD results on formation of the Q⁻(A)/Y(•+)(Z) radical pair suggest a value of ΔH similar to the free energy change, ΔG, of -540±40 meV previously determined by the analysis of recombination fluorescence, but presently the uncertainty range of ΔH values determined by PBD is still high (±250 meV). In the oxygen-evolving transition, S₃−−>S₀, the enthalpy change may be close to zero. A prominent non-thermal signal is associated with both Q⁻(A)/Y(•+)(Z) formation (<1 μs) and the S₃−−>S₀ transition (~1 ms). The observed (apparent) volume expansion (ΔV of about +40 ų per PSII unit) in the S₃−−>S₀ transition seems to revert, at least partially, the contractions on lower S-transitions and may also comprise contributions from O₂ and proton release. The observed volume changes show that the S₃−−>S₀ transition is accompanied by significant nuclear movements, which likely are of importance with respect to energetics and mechanism of photosynthetic water oxidation. Detailed PBD studies on all S-transitions will contribute to the progress in PSII research by providing insights not accessible by other spectroscopic methods.

Investigation on chalcogenide glasses for its threshold phenomena using photothermal methods

Photoacoustic spectroscopy (PAS) and Photothermal beam deflection spectroscopy (PBS) was used to study the bulk Ge7.5As x Te92.5 − x alloy glasses in the composition range, 17.5 ≤ x ≤ 60 [co-ordination number (⟨r⟩), 2.35–2.75] for its thermal diffusivity (α). α was found to be maximum for ⟨r⟩ = 2.4 (0.85 × 10− 2 cm2/s), with increase in ⟨r⟩ there was a steep decrease except for a small hump observed at ⟨r⟩ = 2.67 (0.44 × 10− 2 cm2/s). This observed behaviour is explained on the basis of two transitions points at ⟨r⟩ = 2.4 and ⟨r⟩ = 2.67, that correspond to mechanical and chemical thresholds respectively. The advantage of PAS and PBS is highlighted in comparison with the conventional absorption spectrophotometric technique. These methods are independent of sample thickness and are not affected by light scattering which is ideally suited for studying chalcogenide glassy systems. The experimental data was curve-fitted using the one-dimensional heat diffusion equation to evaluate the accuracy of the thermal diffusivity values obtained.

Identification of actinide molecule complexes: A new vibrational spectroscopic approach at the free-electron laser facility FELBE

Photothermal beam deflection (PTBD) spectroscopy using a free-electron laser (FEL) as a coherent pulsed pump source was applied for recording infrared spectra of actinide molecule complexes. We demonstrate that reliable spectra of samples containing uranyl and neptunyl compounds can be obtained in the mid-infrared region which was verified by conventional FT-IR spectroscopy. Since photothermal techniques are generally capable of detecting very low absorptions we tried to evaluate the minimum content of actinide ions which can still be detected by our setup of the PTBD experiment. It was found that the limit is obviously given by the background absorption of the hygroscopic KBr matrix of the samples which is originated by residual water. Furthermore, we present an overview about the technical equipment of the FEL-laboratory which is suitable for spectroscopic investigations in actinide research.

Direct Measurement of the Triplet Quantum Yield of Poly(3-dodecylthiophene) in Solution

The photophysics, including radiative and nonradiative quantum yields and decay rates, of regioregular poly(3-dodecylthiophene) (P3DT) in benzene were studied by means of UV−visible spectroscopy, photoluminescence spectroscopy, photothermal beam deflection (PBD), photoacoustic calorimetry (PAC), and time-resolved photoluminescence spectroscopy. We observe the fluorescence quantum efficiency to be 0.30 ± 0.01 and the internal conversion (from S1 to S0) quantum yield of 0.59 ± 0.02 as well as the intersystem crossing (from S1 to T1) quantum yield of 0.11 ± 0.01. By measuring the fluorescence lifetime of ca. 490 ps, we estimate a radiative lifetime of 1.64 ns for the singlet excitons and nonradiative decay rate constants of kic = 1.21 ns-1 and kisc = 0.22 ns-1 for internal conversion and intersystem crossing, respectively. The nature and photophysics of triplet states in poly(3-dodecylthiophene) are well characterized using PBD and PAC, and the result suggests that internal conversion plays a major role in energy depletion.

OPTIMISATION OF PARAMETERS FOR PHOTOTHERMAL/MIRAGE SENSOR DESIGN IN VIEW OF IN SITU ENVIRONMENTAL AND INDUSTRIAL AGRICULTURAL APPLICATIONS

We define recommendations for compact set-up design for real time in situ trace gas detection based on both theoretical analysis of certain optical parameters (parallelism and collimation) and practical considerations in environmental and industrial agriculture applications. Criteria are proposed for the selection of parallel photothermal beam deflection (PTBD or mirage effect) spectroscopy, based on advantages discussed in this analysis. Furthermore, this analysis allows sensitivity optimisation and highlights local (non-remote) continuous detection applications of systems based on this principle. We illustrate these applications with recent gas phase measurements for coffee process control.

Photothermal beam deflection spectroscopy in the near IR on poly[3-alkylthiophene

Photothermal beam deflection spectra of non-oxidized polythiophenes with different lengths of alkyl side chains have been taken in the near IR, which is the interesting spectral regime for nonlinear optical waveguide applications. Two kinds of films could be fabricated for all polythiophene derivatives which differ in the optical density and the strength of vibrational bands. For films of low absorption the intensity of the symmetric and antisymmetric CH 2/CH 3-stretching vibrations increase more than linearly with increasing side chain length. In a partly fluorinated polythiophene these modes disappear. An electronic absorption band in the shoulder of the main absorption of the conjugated main chain was found in derivatives which have regio regular substituted side chains and impurities of iron trichloride.

Applications of a compact photothermal-deflection-based setup for trace-gas detection in real-time in situ environmental monitoring and chemical analysis

We present the application of a compact setup for real-time in situ trace-gas detection based on photothermal beam deflection (mirage-effect) spectroscopy to environmental monitoring and chemical analysis. The setup provides many advantages for local (nonremote) detection applications, such as rapid response and high sensitivity under true in situ conditions. The detection limit of C(2)H(4) in open air is estimated to be 0.25 parts in 10(9), based on concentration calibration with the dominant noise that is due to atmospheric turbulence on a time scale of 1 s. Detection limits are extrapolated for other species, and applications are explored by real-time measurements of gas emissions from a variety of solid and semisolid samples.

Homogeneous Immunoassay Using Photothermal Beam Deflection Spectroscopy

We developed a novel homogeneous immunoassay using photothermal beam deflection (PBD) spectroscopy. Antibody-coated glass beads having a particle size of 50 μm and antibody-coated colloidal gold ultrafine particles 20 nm in size were used, and an immune complex containing colloidal gold particles on antibody-coated glass beads was formed by immunological reaction in solution. An excitation beam was affected from below the sample, and a PBD signal was thus generated was measured. The PBD signal was not affected by nonreached antibody-floated colloidal gold particles which were suspended in the solution up to the colloidal gold concentration of 0.008%. This result indicates that homogeneous immunoassay is possible. Human α-fetoprotein was assayed to examine the sensitivity of this method, and a detection limit of 0.25 ng/mL was obtained. This was more sensitive by 1 order of magnitide that the latex agglutination method, the conventional homogeneous rapid assay. Some improvements of reagents and techniques can be expected to enhance the sensitivity further

Photothermal measurement of bulk and surface absorption of transparent infrared optical elements

Photothermal probe beam deflection spectroscopy is used to separately measure bulk and surface absorption of transparent IR optical elements. Different approaches of this technique are considered. One approach consists in variation of the laser beam heat modulation frequency in the condition that the heating beam component is transverse to the path of the probe beam. Another approach consists in varying the heat and probe cross section measuring point position within the tested optical sample. It is theoretically and experimentally shown that in the second case, the spatial resolution and measurement locality are determined by the size of laser beam spots and the thermal diffusion length in a sample. The relative contribution of surface and bulk absorption to summary absorption can be derived from the ratio of the probe beam deflection signal, measured both near the surface and within the sample volume far from the surface, to thermal wavelength. Absolute calibration of absorption measurements can be carried out using laser calorimetry. A comparison between deflection and calorimetry data on volume absorption in a number of ZnSe laser optical elements is made and shows a good correlation.