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Evaluating Noise Reduction Methods for Raman Spectroscopy in Transmission and Reflection Configurations
(2024-05-01)
Sassuvun, Wasunun
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Buranasiri, Prathan
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Wicharn, Surawut
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Puttharugsa, Chokchai
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Limnonthakul, Puenisara
This work involved comparing Raman signals obtained from two different Raman spectroscopy configurations, using two distinct noise reduction methods. The excitation light source was a laser diode with a wavelength of 532 nm. A long-pass filter and focusing lens were utilized to block the excited light from the source and concentrate the Raman signals due to their weaker nature compared to the excited light signals. Light of 532 nm wavelength was blocked during green laser diode illumination using a long-pass filter. Two configurations were studied: transmission Raman spectroscopy (TRS) and reflection Raman spectroscopy (RRS). Raman signals from both configurations were compared, and the boxcar averaging and Vancouver Raman algorithm (VRA) noise reduction methods were investigated and compared. The results showed that Raman signals from the transmission configuration were higher than those from the reflection configuration, and noise signals were effectively reduced using both the boxcar averaging and VRA methods.
1
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Rapid smartphone-based assays for pesticides inspection in foods: current status, limitations, and future directions
(2024-01-01)
Yun, Pheakdey
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Jinorose, Maturada
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Devahastin, Sakamon
Smartphone-based assays to inspect pesticides in foods have attracted much attention as such assays can transform tedious laboratory-based assays into real-time, on-site, or even home-based assay and hence overcoming the limitations of conventional assays. Although an array of smartphone-based assays is available, information on the use of these assays for pesticides inspection is scattered. The purposes of this review are therefore to compile, summarize and discuss state-of-the-art as well as advantages and limitations of the relevant technologies. Suggestions are provided for further development of smartphone-based assays for rapid inspection of pesticides in foods. Smartphone-based assays relying on enzyme inhibitions are noted to be nonselective qualitative, capable of reporting results in a quantitative manner only when a sample contains an individual pesticide. Smartphone-based assays relying on chemical reactions also target only individual pesticides. Smartphone-based visible spectroscopy can, on the other hand, inspect individual and multiple pesticides with the aid of appropriate colorimetry-, luminescence-, or fluorescence-based assay. Smartphone-based visible-near infrared and Raman spectroscopies are suitable for simultaneous multiple pesticides inspection. Raman spectroscopy is of particular interest as it can detect pesticides even at lower concentrations. This spectroscopic technique can also serve as a real-time assay with the aid of cloud network computations.
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RF-sputtered V2O5 thin films on two different glass substrates
(2021-01-01)
Khlayboonme, S. Tipawan
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Thowladda, Warawoot
Thin V<inf>2</inf>O<inf>5</inf> films were deposited on two different commercial soda-lime glass substrates (A and B) by O<inf>2</inf> reactive radio frequency magnetron sputtering using a vanadium target. The influences of the surface energy and roughness of the substrates on the structure and atomic bonding of the films were examined. The film on substrate A was polycrystalline, with eight crystal orientations, whereas the film on substrate B yielded an intense (001) diffraction peak of α-V<inf>2</inf>O<inf>5</inf> and a weak (200) peak of β-V<inf>2</inf>O<inf>5</inf>, indicating preferred orientation along these planes. Structural analyses indicated that substrate B with lower surface energy and higher roughness enhanced the formation of a layered a-V<inf>2</inf>O<inf>5</inf> structure.
1
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Synchrotron-based NEXAFS analysis of thermal-treated diamond-like carbon films
(2020-10-01)
Chunjaemsri, Thanun
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Chanlek, Narong
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Sukkha, Usa
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Nakajima, Hideki
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Rujirawat, Saroj
Diamond-like carbon (DLC) film properties are known to vary with important factors such as the ratio of sp3 to sp2 hybridization, film thickness, and contaminations. In this work, the carbon bonding contents in DLC thin films, thermal-treated with various temperatures between room temperature to 250 °C, were studies by near-edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. From NEXAFS measurements, the sp3/sp2 ratios of DLC films were found to be unaffected by the thermal treatments. The results indicate that thermal treatment below 250 °C does not affect the carbon bonding contents in DLC thin film.
2
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Characterisation of thermal oxide scales on stainless steels
(2020-01-01)
Srisrual, Anusara
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Thublaor, Thammaporn
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Wongpromrat, Patthranit
This chapter aims at reviewing the characterisation techniques that are commonly used for high temperature oxidation study, especially on stainless steels. In addition, the experimental studies about the high temperature oxidation i.e. thermogravimetric method and chromium volatilisation measurement are explained. The various kinds of characterisation techniques for physico-chemical and electronic properties of thermal oxide scales are reviewed, starting from optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), focused ion beam coupled with scanning electron microscope (FIB/SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RS), and photoelectrochemical characterisation (PEC). The review focuses on the basic concepts and shows how the characterising tools can be applied to thermal oxide characterisation.
1
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Plasma impedance tuning effect on nanostructure of diamond films
(2013-10-25)
Thowladda, Warawoot
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Khlayboonme, S. T.
The morphology and structure of nanocrystalline diamond films as well as the plasma chemistry were studied by altering the plasma impedance. These impedances related to electron density were altered via the matching system. Two films were grown by the microwave plasma under different values of the plasma impedance, resulting in low and high electron densities in the plasma. By the use of measurements of plasma impedance and optical emission, the lowering of an inductive component of the impedance, indicating an increasing electron density, encouraged H-radical concentration present in the plasma. As the plasma was changed to the high electron density, Raman spectra of the films showed the sp3 Raman peak shifted from 1325 to 1328.5 cm-1 with narrower broadening. This behavior arose from an increase in grain size, corresponding to images from a field emission scanning electron microscope. Raman spectra of G-peak position and white light reflectometry showed a reduction in sp2 carbon content of the film. The G-peak shifted from 1564 to 1541 cm-1 and refractive index increased from 1.84 to 2.16. The formation of the films related to the concentrations of H and CH3 radicals. The plasma impedance affected the radical concentrations. © (2013) Trans Tech Publications, Switzerland.
1
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Effect of two-step deposition process on morphology and optical properties of nanostructured diamond films
(2013-02-19)
Tipawan Khlayboonme, S.
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Techitdheera, W.
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Thowladda, Warawoot
The morphology and optical properties of nanostructured diamond films affected by the two-step deposition process with changing CH4 concentration were investigated. The CH4 concentration was 1% for the first step and 2% for the second step. The films were prepared by chemical vapor deposition in a microwave plasma reactor with a CH4/H2 gas mixture. Nanocrystalline columnar-structured diamond film with lowering of sp2-bonded carbon content was achieved by the two-step deposition process. Unlike that of the single-step process with 1%CH4, the two-step process promoted the morphology to more uniform and smoother film. The two-step process increased the higher grain boundary as well as decreased the sp2-bonded carbon content in the film, as compared with the single-step process with 2%CH<inf>4</inf>. © (2013) Trans Tech Publications, Switzerland.
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