Absorption Spectroscopy Techniques Research Articles

Design of an electronic system for laser methane gas detectors using the tunable diode laser absorption spectroscopy method

In this paper, a new electronic system is designed for methane gas laser analyzers using the tunable diode laser absorption spectroscopy (TDLAS) technique. This electronic system is presented in such a way that, based on this technique, optical wavelength and stability confirm the power of the laser light source. The proposed design includes current and temperature control circuits, amplifier circuits, and laser sensor circuits. This system leads to the control of laser light power. Due to the high cost of a laser sensor distributed feedback diode (DFB) and the impossibility of purchasing it for the actual implementation of the proposed electronic system, the design and simulation stage of this system was performed in the proteus simulator environment at normal atmospheric temperature and constant control flow conditions. The simulation results show that the proposed new electronic system based on the TDLAS technique detected the amount of leaking methane gas by generating a wavelength of 1653.72 nm related to the DFB laser sensor and displaying it on display during calculation. The test of optical wavelength stability, optical power, and methane gas wavelength generation by the laser sensor in the proteus simulator environment at different distances is excellent and remarkable. These results show that if we buy a laser sensor and build a gas analyzer device, we can achieve perfect results by using the device with the provided technique.

Characterization of toxic substances present in smoking tobacco using different spectroscopic techniques

Laser-induced breakdown spectroscopy (LIBS), a laser-based atomic spectroscopic technique, has been used to investigate the presence of toxic/heavy elements/compounds in various smoking tobacco samples. Based on the analysis of the LIBS spectra, the presence of toxic elements like Cr, Sb, Sr, Ni, and Ba, including organic elements C, H, N, O and other common elements like Fe, Mg, Na, and K, has been confirmed in the tobacco samples. Electronic bands of diatomic molecules such as CN and C2 are also observed in the LIBS spectra of the samples, which may be due to the presence of nicotine, chlorophyll, anthocyanin, etc., organic compounds. Calibration-free LIBS (CF-LIBS), a mathematical method, is used to determine the concentration of constituents using the intensity of the spectral lines of the species in the tobacco samples. Atomic absorption spectroscopy (AAS) technique is also used to determine the concentration of elements. The result obtained by AAS validates the result obtained using the CF-LIBS method. The presence of the organic compounds/molecules in the tobacco samples has been investigated using photoacoustic spectroscopy (PAS). Based on the analysis of the PAS spectrum, various organic compounds/molecules like nicotine, chlorophyll, pheophytin, β-carotenoid, anthocyanin, pheophytin, chlorophyllide, and bacteriochlorophy II are identified in the tobacco samples. UV-Visible absorption spectroscopy of these samples is used to compare the results obtained by PAS. Principal component analysis, a multivariate method, is applied to LIBS data to classify the various smoking tobacco samples based on their constituents. Our results show that ten smoking tobacco samples of different brands are forming three different clusters based on the similarity of their constituents.

Engineering ordered vacancies and atomic arrangement over the intermetallic PdM/CNT (M = Pb, Sn, In) nanocatalysts for synergistically promoting electrocatalysis N2 fixation

Engineering ordered vacancies and atomic arrangement over the intermetallic PdM/CNT (M = Pb, Sn, In) nanocatalysts for synergistically promoting electrocatalysis N2 fixation

Spatial Distribution of Black Soot and Its Health Effects in Port Harcourt Metropolis, Nigeria

This research presents a novel approach to assessing the health implications of black soot using a MiniVol air sampler. The MiniVol air sampler was used to collect PM from the ambient air at six monitoring sites in Port Harcourt, Nigeria. Sampling was conducted every day for seven days, for 24 hours. PM2.5 concentrations at Uniport Junction, GRA Junction, Slaughter Roundabout, Abuloma Jetty, Rumuomasi Roundabout, and New Road Borokiri were 38.6 g/m3, 28.3 g/m3, 93.7 g/m3, 72.9 g/m3, 30.6 g/m3, and 31.3 g/m3, respectively. PM10 concentrations ranged from 71.2 g/m3 to 60.6 g/m3, with 103.3 g/m3, 85.5 g/m3, 40.1 g/m3, and 35.2 g/m3 being the highest. The level of PM2.5 and PM10 pollution in the ambient air was high across the six sampling sites, with mean PM2.5 and PM10 concentrations exceeding the WHO (2011) guideline. The flame atomic absorption spectrometry (FAAS) technique was used. The presence of heavy metals, such as mean metal concentrations of lead, cadmium, chromium, mercury, and nickel, ranged from 0.009 g/m3 -0.532 g/m3, 0.002 g/m3 - 0.544 g/m3, 0.002 g/m3 -0.338 g/m3, 0.001 g/m3, and 0.001 g/m3 -0.432 g/m3, across the six sampling sites. The GC-MS was used to determine the presence of PAHs in particulate matter. Correlation results revealed a strong positive correlation between PM2.5 and PM10. The findings also revealed a positive relationship between the metals as well as between the metals and PAHs, resulting in asthma, lung cancer, breathing difficulties, and miscarriages among pregnant women, which have affected the health implications of the people living in the environment.

Comprehensive structural {single crystal X-raydiffraction, spectroscopic & DFT computational simulation} and biological {in vitro DNA binding & antibacterial} studies of polymeric copper(Ⅱ)-based imidazole drug entity

Comprehensive structural {single crystal X-raydiffraction, spectroscopic & DFT computational simulation} and biological {in vitro DNA binding & antibacterial} studies of polymeric copper(Ⅱ)-based imidazole drug entity

Retention of immobile Se(0) in flow-through aquifer column systems during bioreduction and oxic-remobilization

Selenium (Se) is a toxic contaminant with multiple anthropogenic sources, including 79Se from nuclear fission. Se mobility in the geosphere is generally governed by its oxidation state, therefore understanding Se speciation under variable redox conditions is important for the safe management of Se contaminated sites. Here, we investigate Se behavior in sediment groundwater column systems. Experiments were conducted with environmentally relevant Se concentrations, using a range of groundwater compositions, and the impact of electron-donor (i.e., biostimulation) and groundwater sulfate addition was examined over a period of 170 days. X-Ray Absorption Spectroscopy and standard geochemical techniques were used to track changes in sediment associated Se concentration and speciation. Electron-donor amended systems with and without added sulfate retained up to 90% of added Se(VI)(aq), with sediment associated Se speciation dominated by trigonal Se(0) and possibly trace Se(-II); no Se colloid formation was observed. The remobilization potential of the sediment associated Se species was then tested in reoxidation and seawater intrusion perturbation experiments. In all treatments, sediment associated Se (i.e., trigonal Se(0)) was largely resistant to remobilization over the timescale of the experiments (170 days). However, in the perturbation experiments, less Se was remobilized from sulfidic sediments, suggesting that previous sulfate-reducing conditions may buffer Se against remobilization and migration.

Source identification and ambient trace element concentrations of PM10 using receptor modeling in an urban area of Chhattisgarh, India

This study investigated seasonal variation in PM10 aerosols and associated trace metal concentrations in an urban city Raipur, India. PM10 aerosols were monitored at Raipur for the year 2015 to 2019. Eighteen trace elements (Al, Ba, Ca, Cr, As, Mn, Sb, Se, Sr, Cu, Fe, Ga, Mg, Ni, Ti, V, Pb, Zn) and (EC and OC) were analyzed using atomic absorption spectroscopy and thermal optical transmittance technique. A receptor-based positive matrix factorization (PMF) model was used to identify the possible sources with qualitative analysis of crustal enrichment factor, back-trajectory analysis using concentration weighted trajectory (CWT) to predict potential locations of distant sources, and correlation between different species. The average PM10 aerosol mass concentration during the study period was found to be 184.91 ± 114 µg/m³. Seasonally, the average winter–time PM10 concentration (193.49 ± 129.18 µg/m³) was found higher as compared to summer time (176.32 ± 65.80 µg/m³) during the study period. Five sources were identified including the iron and steel industry (30%), biomass and waste combustion (28.7%), vehicular emissions (21%), heavy oil combustion (17.4%), and crustal dust (2.9%). The study provides information on major sources affecting air quality.

Synthesis, characterization and biological properties of Ruthenium(II) polypyridyl complexes containing 2(1H)-quinolinone-3(1H-imidazo[4,5f][1,10]phenanthrolin-2-yl

Synthesis, characterization and biological properties of Ruthenium(II) polypyridyl complexes containing 2(1H)-quinolinone-3(1H-imidazo[4,5f][1,10]phenanthrolin-2-yl

Efficiency improvement of CIGS solar cells using RF sputtered TCO/Ag/TCO thin-film as prospective buffer layer

Efficiency improvement of CIGS solar cells using RF sputtered TCO/Ag/TCO thin-film as prospective buffer layer

Synthesis, structure characterization, spectral properties, DFT calculations, hirshfeld surface analysis, thermal stability and bioactivity of a new sulfamethoxazole zinc(II) complex

Synthesis, structure characterization, spectral properties, DFT calculations, hirshfeld surface analysis, thermal stability and bioactivity of a new sulfamethoxazole zinc(II) complex

Risk Assessment of Total Mercury (T-Hg) in Commercial Seafood Marketed in Bangkok, Thailand

Seafood is recognized as the high protein source of human consumption. However, it is hampered by mercury contamination. The objectives of this study are to determine total mercury (T-Hg) levels in edible portions of commercial seafood available in Bangkok’s supermarkets, and to evaluate the potential risks from mercury through seafood consumption. Total 32 species, including 22 fish, 4 cephalopod and 6 shellfish, were purchased from super-markets. Fish samples were dissected in 3 parts comprised of flesh, gill and viscera. While, cephalopod and shellfish were separated for edible tissues. The samples were digested in hot acid and were determined using cold-vapor atomic absorption spectrometry technique. The results revealed that T-Hg contained in the fish flesh > cephalopod > shellfish. In addition, T-Hg was accumulated in flesh > viscera > gill. Statistical analysis suggested that T-Hg accumulated in flesh was related positively with species, feeding habit, and habitat (p < 0.05). For risk analysis, estimated daily intake (EDI) of flesh ranged from 0.01 to 0.42 µg kg-1 bodyweight d-1, the lowest and highest EDI values were in salmon and yellowfin tuna, res-pectively. Yellowfin tuna, narrow-barred Spanish mackerel, fourfinger threadfin, and silver sillago were the 4 species that having the EDI values of T-Hg higher than the FAO/WHO recommended provisional tolerable daily intake (PTDI) of 0.23 µg kg-1 bodyweight d-1. Thus, the frequent consumption of these seafood are not recommended. In addition, the daily consumption of seafood should not exceed the maximum safe daily intake (MSDC). The MSDC of seafood in this study ranged from 15.5 (yellowfin tuna) to 474 (salmon) g d-1.

Infrared cavity ring-down spectroscopy for detecting non-small cell lung cancer in exhaled breath

Early diagnosis of lung cancer greatly improves the likelihood of survival and remission, but limitations in existing technologies like low-dose computed tomography have prevented the implementation of widespread screening programs. Breath-based solutions that seek disease biomarkers in exhaled volatile organic compound (VOC) profiles show promise as affordable, accessible and non-invasive alternatives to traditional imaging. In this pilot work, we present a lung cancer detection framework using cavity ring-down spectroscopy (CRDS), an effective and practical laser absorption spectroscopy technique that has the ability to advance breath screening into clinical reality. The main aims of this work were to (1) test the utility of infrared CRDS breath profiles for discriminating non-small cell lung cancer (NSCLC) patients from controls, (2) compare models with VOCs as predictors to those with patterns from the CRDS spectra (breathprints) as predictors, and (3) present a robust approach for identifying relevant disease biomarkers. First, based on a proposed learning curve technique that estimated the limits of a model’s performance at multiple sample sizes (10–158), the CRDS-based models developed in this work were found to achieve classification performance comparable or superior to like mass spectroscopy and sensor-based systems. Second, using 158 collected samples (62 NSCLC subjects and 96 controls), the accuracy range for the VOC-based model was 65.19%–85.44% (51.61%–66.13% sensitivity and 73.96%–97.92% specificity), depending on the employed cross-validation technique. The model based on breathprint predictors generally performed better, with accuracy ranging from 71.52%–86.08% (58.06%–82.26% sensitivity and 80.21%–88.54% specificity). Lastly, using a protocol based on consensus feature selection, three VOCs (isopropanol, dimethyl sulfide, and butyric acid) and two breathprint features (from a local binary pattern transformation of the spectra) were identified as possible NSCLC biomarkers. This research demonstrates the potential of infrared CRDS breath profiles and the developed early-stage classification techniques for lung cancer biomarker detection and screening.

Sulfur-acetylacetone based solutions for precipitation of quasi-core–shell microparticles or hybrid structures

Sulfur-acetylacetone based solutions for precipitation of quasi-core–shell microparticles or hybrid structures

Performance and Wear Debris Characteristics of Karanja Biodiesel and Biolubricant as a Substitute in a Compression Ignition Engine

Performance and Wear Debris Characteristics of Karanja Biodiesel and Biolubricant as a Substitute in a Compression Ignition Engine

Synthesis, characterization, and investigation of nonlinear property of fly ash-red mud-Ag: A low-cost sustainable nanocomposite

Synthesis, characterization, and investigation of nonlinear property of fly ash-red mud-Ag: A low-cost sustainable nanocomposite

Clustering Analysis on Drivers of O3 Diurnal Pattern and Interactions with Nighttime NO3 and HONO

The long-path differential optical absorption spectroscopy (LP-DOAS) technique was deployed in Shanghai to continuously monitor ozone (O3), formaldehyde (HCHO), nitrogen dioxide (NO2), nitrous acid (HONO), and nitrate radical (NO3) mixing ratios from September 2019 to August 2020. Through a clustering method, four typical clusters of the O3 diurnal pattern were identified: high during both the daytime and nighttime (cluster 1), high during the nighttime but low during the daytime (cluster 2), low during both the daytime and nighttime (cluster 3), and low during the nighttime but high during the daytime (cluster 4). The drivers of O3 variation for the four clusters were investigated for the day- and nighttime. Ambient NO caused the O3 gap after midnight between clusters 1 and 2 and clusters 3 and 4. During the daytime, vigorous O3 generation (clusters 1 and 4) was found to accompany higher temperature, lower humidity, lower wind speed, and higher radiation. Moreover, O3 concentration correlated with HCHO for all clusters except for the low O3 cluster 3, while O3 correlated with HCHO/NOx, but anti-correlated with NOx for all clusters. The lower boundary layer height before midnight hindered O3 diffusion and accordingly determined the final O3 accumulation over the daily cycle for clusters 1 and 4. The interactions between the O3 diel profile and other atmospheric reactive components established that higher HONO before sunrise significantly promoted daytime O3 generation, while higher daytime O3 led to a higher nighttime NO3 level. This paper summarizes the interplays between day- and nighttime oxidants and oxidation products, particularly the cause and effect for daytime O3 generation from the perspective of nighttime atmospheric components.

Improving power conversion efficiency by Light-Assisted annealing of triple cation perovskite layer in solar cell applications

Improving power conversion efficiency by Light-Assisted annealing of triple cation perovskite layer in solar cell applications

Vibronic States and Edge-On Oriented π-Stacking in Poly(3-alkylthiophene) Thin Films

The influence of alkyl side-chain length [CnH2n+1 (A), where n = 6 (hexyl), 8 (octyl), 12 (dodecyl)] and thermal annealing (TA) and the definite roles of these in the quantity and quality of π-stacked crystallinity and edge-on orientated (EO) ordering of spin-coated poly(3-alkylthiophene) [P3AT] thin films, which are of massive significance in their optoelectronic properties, were investigated using complementary optical absorption spectroscopy and X-ray reflectivity (XR) techniques. The energy-band diagram, corresponding to the vibronic levels, obtained from the optical absorption spectrum provides information about the percentage, planarity, local order, and average conjugation length of the crystalline aggregates, while the electron density profile obtained from the XR provides unique information about the EO ordering and its variation along the depth. A prominent EO ordering near the substrate with a gradually decreased ordering toward the top surface is observed in each film. An as-cast P3HT film of shorter side-chain (having a natural nucleation tendency and rigidity) shows a slightly higher crystallinity and weaker excitonic coupling, while as-cast P3DDT film (having longer side-chain flexibility) shows a slightly better EO ordering. After the TA, the planarity of the unfolded backbone improves in each film; however, the effect is maximum in the P3DDT film. The EO ordering also improves throughout the film (by a thermal energy-induced reorientation of crystallites) but more toward the top surface (by increasing the decay length), preserving the exponential decay nature. The P3HT film (with the better initial crystallinity and planarity) shows an appreciable improvement, while the P3DDT film (where the crystallinity increases and crystallites have a better reorientational ability) shows the maximum improvement in the EO ordering. The improvement of the crystallinity (in quantity and quality) and the EO ordering of P3AT in thin films (as active layers), especially near the film–substrate interfaces, are of immense importance for their better in-plane charge carrier mobility in a thin-film transistor.

Unraveling the nature of sulfur-bearing silicate-phosphate glasses: Insights from multi-spectroscopic (Raman, MIR, 29Si, 31P MAS-NMR, XAS, XANES) investigation

Unraveling the nature of sulfur-bearing silicate-phosphate glasses: Insights from multi-spectroscopic (Raman, MIR, 29Si, 31P MAS-NMR, XAS, XANES) investigation

Pulsed-cavity ring down spectroscopic study of NO2 in 501–506 nm spectral region

Pulsed-cavity ring down spectroscopic study of NO2 in 501–506 nm spectral region