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The ammonia spectrum is revisited in the important 1.6 µm atmospheric transparency window between 5650 and 6350 cm $ ^{-1} $ − 1 on the basis of recently recorded high-resolution Fourier transform spectra. These spectra offer an improved frequency sampling and better traceability of the measurement conditions compared to previously studied Kitt Peak spectra (Cacciani et al. J. Quant Spectrosc Radiat Transf 2021; 258:107334. https://doi.org/10.1016/j.jqsrt.2020.107334). Overall, 4812 $ ^{14} $ 14 NH $ _3 $ 3 lines were measured in the 5650–6350 cm $ ^{-1} $ − 1 region corresponding to 4866 transitions including 2066 new ones compared with our previous study, included in the HITRAN2020 database. The energy of 1023 upper state levels (including 107 new ones) was derived from 2608 assigned transitions. Independently, ammonia spectra recorded in a supersonic jet expansion using a tunable extended cavity diode laser allow us to check the absolute transition energies in the 5980–6080 cm $ ^{-1} $ − 1 range. Accurate jet spectra calibration was achieved using CH $ _4 $ 4 reference line positions known with kHz accuracy. The position agreement with the FTS data is within the $ 4\times 10^{-4} $ 4 × 10 − 4 cm $ ^{-1} $ − 1 uncertainty of the positions measured in the jet expansion. A recommended line list of 5620 transitions is provided for $ ^{14} $ 14 NH $ _3 $ 3 in the considered 5650–6350 cm $ ^{-1} $ − 1 region. [ABSTRACT FROM AUTHOR]

The ammonia spectrum is revisited in the important 1.6 µm atmospheric transparency window between 5650 and 6350 cm $ ^{-1} $ − 1 on the basis of recently recorded high-resolution Fourier transform spectra. These spectra offer an improved frequency sampling and better traceability of the measurement conditions compared to previously studied Kitt Peak spectra (Cacciani et al. J. Quant Spectrosc Radiat Transf 2021; 258:107334. https://doi.org/10.1016/j.jqsrt.2020.107334). Overall, 4812 $ ^{14} $ 14 NH $ _3 $ 3 lines were measured in the 5650–6350 cm $ ^{-1} $ − 1 region corresponding to 4866 transitions including 2066 new ones compared with our previous study, included in the HITRAN2020 database. The energy of 1023 upper state levels (including 107 new ones) was derived from 2608 assigned transitions. Independently, ammonia spectra recorded in a supersonic jet expansion using a tunable extended cavity diode laser allow us to check the absolute transition energies in the 5980–6080 cm $ ^{-1} $ − 1 range. Accurate jet spectra calibration was achieved using CH $ _4 $ 4 reference line positions known with kHz accuracy. The position agreement with the FTS data is within the $ 4\times 10^{-4} $ 4 × 10 − 4 cm $ ^{-1} $ − 1 uncertainty of the positions measured in the jet expansion. A recommended line list of 5620 transitions is provided for $ ^{14} $ 14 NH $ _3 $ 3 in the considered 5650–6350 cm $ ^{-1} $ − 1 region. [ABSTRACT FROM AUTHOR]

Optical spectroscopy is a powerful tool for characterizing the properties of two-dimensional (2D) heterostructures. However, extracting the permittivity information of each 2D layer in optically thick heterostructures is challenging because of interference. To accurately measure the optical permittivity of each 2D layer in a heterostructure or on a substrate with a thick insulating spacer, such as oxides, we propose deterministic reflection contrast ellipsometry (DRCE). Our DRCE method has two advantages over conventional techniques. It deterministically measures the optical permittivity of 2D materials using only the measured reflection spectra of the heterostructure, rather than dispersion fitting as in spectroscopic ellipsometry. Additionally, the DRCE is free of excitonic energy errors in reflection-contrast spectroscopy. We believe that DRCE will enable accurate and rapid characterization of 2D materials. [ABSTRACT FROM AUTHOR]

The 1,4‐dithiin motif is known for its reversible redox properties to generate radical cations and diradical dications and thus is interesting for organic electronic applications. However, examples where this motif is embedded into chiral larger fused aromatic compounds are very rare. Here we describe the syntheses of several structurally related pyrene fused dithiins and their spectroscopic investigations with a focus on tuning circular dichroism, with respect to the g values, depending on their connectivity. [ABSTRACT FROM AUTHOR]

Nanosphere lithography, a low‐cost fabrication technique, depends on the self‐assembly of nanoscale features to create nanostructures in a hexagonally close‐packed structure. In this article, the fabrication of 3D nanostructures over a large surface‐area with anisotropy along the growth direction through the combination of chemical and physical plasma etching is reported. The anisotropy stems from etching the nanosphere mask and the substrate at different rates. Due to the dynamic masking effect, a systematic variation of etching time gives rise to intriguing nanostructures with sharp edges that have strong potential for plasmonic applications, with the possibility of manipulating electromagnetic radiation. The structures obtained include nanocylinders, truncated hexagon‐based pyramids, circular pads on a conical base, and nanocones from a single‐layer nanosphere mask. Simulations of the fabrication process offer further insight into the understanding of nanostructure formation. A good agreement between predicted results and experiments confirms the potential of our numerical design. In addition, the optical properties of the nanostructures are investigated by UV–vis and the experimental findings are consistent with simulations based on a finite‐difference time‐domain method. The nanostructures described in this study contribute to the emerging 3D plasmonics and 3D magnonics, with strong potential for a significant impact on biosensor applications. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copper nanoparticles (CuNPs) have drawn considerable interest because of recent evidences on greater Surface Enhanced Raman Spectroscopic (SERS) signal enhancing capability, high antibacterial activity and strong catalytic property with regard to the long existing popular silver and gold particles. The existing chemical synthesis methods usually require extensive purification to remove unreacted inorganic reducing agents, like sodium borohydride used to convert Cu2+ ions to Cu0 and it limits direct use of as-prepared materials in biologic systems. Here, we have endeavored to synthesize starch encapsulated CuNPs through radiation chemical approach which is considered to be one of the cleanest routes and involve in-situ generated hydrated electrons to reduce metal ions directly. Presence of large number of hydroxyl groups within starch molecules facilitates complexation of Cu(II) and thereby stabilizes CuNPs. Transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED) illustrate that particles synthesized at a typical dose of 83.6 kGy are spherical with size of ca. 8 nm having polycrystalline face-centered cubic phase. The observed blue shift of the absorption maximum suggests formation of smaller sized particles with increase in applied radiation dose keeping other parameters same and this is supported by dynamic light scattering (DLS) data. Further, catalytic efficiency of as-synthesized CuNPs was tested by monitoring sodium borohydride mediated catalytic reduction of para-nitrophenol to para-aminophenol and the apparent rate constant (kapp) was estimated as 3 × 10–3 s−1. Thus, as-synthesized CuNPs appears to be better catalyst than the copper nanoparticles synthesized through conventional method for having kapp of about 1.6 × 10–3 s−1. [ABSTRACT FROM AUTHOR]

It was shown earlier that the use of fast protein and metabolites liquid chromatography (FPMLC) and low-cost deep UV–LED-based optical chromatographic sensors with PD-10 desalting columns as a separation element can facilitate the monitoring of patients on chronic peritoneal dialysis (PD). Previously, we established that the first peak in the FPMLC chromatograms of effluent dialysate is mainly responsible for proteins and could be used for the assessment of peritoneal protein loss in patients on PD, while the origin and clinical significance of the other two peaks still remain unclear. Optical absorption and fluorescence spectroscopy in the UV and visible regions of 240…720 nm were used for the analysis of PD effluent chromatographic fractions collected from a drainpipe of the sensor with photometric detection at 280 nm; chromatograms of twenty dialysate samples were processed. The absorption and fluorescence spectra of the first fraction demonstrated peaks at 270 nm and 330 nm, respectively, which is typical for proteins. The absorption spectra of the third fraction revealed the characteristic maxima of creatinine and uric acid, while the fluorescence spectra showed the characteristic peak of indoxyl sulfate 375 nm at 270 nm excitation. The second fraction had a single, extremely wide absorption band, strong fluorescence was observed at 440–450 nm while excited at 370 nm. Such spectral characteristics are typical for advanced glycation end products (AGE). Thus, it was demonstrated that deep UV–LED-based affordable chromatographic sensors could provide significantly more information about the composition of PD effluent dialysate than just the total protein concentration, including the contents of clinically significant metabolites, e.g., indoxyl sulfate and AGE. Moreover, the introduction of optical fluorescence detection could significantly improve the capabilities of such devices.

Hybrid organic–inorganic metal halide perovskites are emerging materials in photovoltaics, whose bandgap is one of the most crucial parameters governing their light‐harvesting performance. This work presents the temperature and photocarrier density dependence of the bandgap in two phase‐stabilized perovskite thin films (MA0.3FA0.7PbI3 and MA0.3FA0.7Pb0.5Sn0.5I3) using photoluminescence and absorption spectroscopy. Contrasting bandgap shifts with temperature are observed between the two perovskites. Using X‐ray diffraction and in situ high‐pressure photoluminescence spectroscopy, it is shown that thermal expansion plays only a minor role in the large bandgap blueshift, which is attributed to the enhanced structural stability of the samples. The first‐principles calculations further demonstrate the significant impact of thermally induced lattice distortions on the bandgap widening. It is proposed that the anomalous trends are caused by the competition between static and dynamic distortions. Additionally, both the bandgap renormalization and band‐filling effects are directly observed for the first time in fluence‐dependent photoluminescence measurements and are employed to estimate the exciton effective mass. The results provide new insights into the basic understanding of thermal and charge‐accumulation effects on the band structure of hybrid perovskite thin films. [ABSTRACT FROM AUTHOR]

Copyright of Romanian Journal of Materials / Revista Romana de Materiale is the property of Foundation for Materials Science & Engineering Serban Solacolu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Exsolution is one of the most successful functionalization techniques to improve the catalytic activity of electrodes in solid oxide fuel and electrolyzer cells (SOFC/SOEC). The objective of this technique is to produce the highest possible number of metallic nanoparticles on the surface of a host-oxide, without significantly altering its structure. In this work, we compare three similar SOFC electrodes: STF (SrTi 0.3 Fe 0.7 O 3), STFN (Sr 0.93 Ti 0.3 Fe 0.63 Ni 0.07 O 3), and STFNC (Sr 0.93 Ti 0.3 Fe 0.56 Ni 0.07 Co 0.07 O 3), revealing that there is a significant difference between Ni–Fe/Ni–Co–Fe nanoparticle formation in STFN/STFNC and pure Fe0 particle formation in STF, which is evidenced by the size and amount of produced nanoparticles, but also by their anchoring to the host-oxide. The terms exsolution and particle segregation will be used, respectively, to distinguish these phenomena. Next, we explore two different reduction methods and observe that the characteristics of exsolution do not only depend on temperature, atmosphere and reduction times, but also on the reduction path taken to reach such conditions. [Display omitted] • Exsolution differs from particle segregation in the NP distribution, density, size and anchorage. • The characteristics of exsolved NPs are influenced by the hydrogen reduction path. • In-situ absorption spectroscopy is used to determine the exsolution temperature threshold. [ABSTRACT FROM AUTHOR]

Background: Radiochromic material such as lithium pentacosa‐10,12‐diynoate (LiPCDA) has been suggested as the radiation‐sensitive material for real‐time in vivo fiber‐optic dosimetry. In this configuration, micron‐thick radiochromic coating would measure the absorbed dose, where a major challenge is the uncertainty in the active material thickness, necessitating calibration. A homogeneously incorporated inert infrared (IR) dye, which must also be stable in ambient conditions and against radiolysis, can be added to the radiochromic film to enable optical calibration. Purpose: This study investigates four commercial cyanine‐based dyes (IR‐783, IR‐806, IR‐868, and IR‐880) for use as an optical calibrant in fiber‐optic radiochromic dosimeters. Methods: All dyes were dissolved in water to confirm solubility. IR‐783 and IR‐806 were dissolved in 10% w/w gelatin solution and coated onto a polyester substrate, which were then sandwiched between two layers of adhesives forming IR‐783 and IR‐806 films. A second batch of IR dyes in gelatin incorporated the LiPCDA, and was coated onto substrate and sandwiched between adhesive to form IR dye + LiPCDA films. The absorbance spectra of the films were measured periodically (176 and 102 days for IR‐dye films, and IR dye + LiPCDA, respectively). The average percentage absorbance, normalized to day 1, was fit to either a single or a double exponential decay model to calculate the spectral stability lifetime (τ1, τ2). Films were irradiated using a 6 MV LINAC beam with a standard setup of 100 source to axis distance (SAD), 10 cm × 10 cm field size and 1.5 cm depth. The change in absorbance of the IR‐dye + LiPCDA films were measured after they were irradiated to 1, 2, 5, 10, and 20 Gy at 3 Gy/min. Results: Only IR‐783 and IR‐806 were sufficiently water soluble. In gelatin matrix, these dyes demonstrated a decrease in absorbance with time for IR‐783 and IR‐806 dyes, with IR‐783 films having an average τ1 = 73 ± 7 days and IR‐806 films τ1 = 7 ± 3 days. When combined with LiPCDA, IR‐806 degraded, losing its original peak at ∼820 nm. Similarly, IR‐783, combined with LiPCDA, showed signs of degradation; however, its original absorbance peak was still observed at ∼800 nm. In the IR‐783 + LiPCDA films, the IR‐783 dye had a τ = 4 ± 1 days, an order of magnitude faster than the IR‐783 with no LiPCDA films. When exposed to x‐ray irradiation, the IR‐783 dye in the IR‐783 + LiPCDA films showed no change in absorbance with increasing absorbed dose. In contrast, the LiPCDA in the films responded as expected, increasing in optical density with increased absorbed dose. Conclusions: IR‐783 and IR‐806 dyes were observed to degrade over time following exponential decay curves. IR‐806 could not be combined with the LiPCDA without degrading. The combination of IR‐783 with LiPCDA demonstrated single exponential decay behavior at a comparatively faster rate than films that did not have LiPCDA. IR‐783 was insensitive to ionizing radiation and thus may be suitable for thickness correction, but an alternative manufacturing procedure may need to be developed. [ABSTRACT FROM AUTHOR]

The Bouguer–Lambert–Beer (BLB) law serves as the fundamental basis for the spectrophotometric determination of pigment content in microalgae. Although it has been observed that the applicability of the BLB law is compromised by the light scattering effect in microalgae suspensions, in-depth research concerning the relationship between the light scattering effect and the accuracy of spectrophotometric pigment determination remains scarce. We hypothesized that (1) the precision of spectrophotometric pigment content determination using the BLB law would diminish with increasing nonlinearity of absorbance, and (2) employing the modified version of the BLB (mBLB) law would yield superior performance. To assess our hypotheses, we cultivated Phaeodactylum tricornutum under varying illumination conditions and nitrogen supplies in controlled indoor experiments, resulting in suspensions with diverse pigment contents. Subsequently, P. tricornutum samples were diluted into subsamples, and spectral measurements were conducted using different combinations of biomass concentrations and path lengths. This was carried out to assess the applicability of the BLB law and the nonlinearity of absorbance. The chlorophyll a and fucoxanthin contents in the samples were analyzed via high-performance liquid chromatography (HPLC) and subsequently used in our modeling. Our findings confirm our hypotheses, showing that the modified BLB law outperforms the original BLB law in terms of the normalized root mean square error (NRMSE): 6.3% for chlorophyll a and 5.8% for fucoxanthin, compared to 8.5% and 7.9%, respectively. [ABSTRACT FROM AUTHOR]

In absorption spectroscopy, it is challenging to detect absorption peaks with significant differences in their intensity in a single measurement. We enable high-dynamic-range measurements by dispersing scatterers within a sample to create a broad distribution of path lengths (PLs). The sample is placed within an integrating sphere (IS) to capture all scattered light of various PLs. To address the complexities of PLs inside the IS and the sample, we performed a ray-tracing simulation using the Monte Carlo (MC) method, which estimates the measured absorbance A and PL distribution from the sample’s absorption coefficient µa and scattering properties at each wavelength λ. This method was validated using dye solutions with two absorption peaks whose intensity ratio is 95:1, employing polystyrene microspheres (PSs) as scatterers. The results confirmed that both peak shapes were delineated in a single measurement without flattening the high absorption peak. Although the measured peak shapes A(λ) did not align with the actual peak shapes µa(λ), MC enabled the reproduction of µa(λ) from A(λ). Furthermore, the analysis of the PL distribution by MC shows that adding scatterers broadens the distribution and shifts it toward shorter PLs as absorption increases, effectively adjusting it to µa.

Mixed cyclization of 5,7‐diphenyl‐6H‐1,4‐diazepine 2,3‐dicarbonitrile and tetrafluorophthalonitrile in the presence of boron trichloride affords along with symmetrical perfluorinated subphthakocyanine, [F12sPc], two novel subporphyrazine‐type products which were isolated by column chromatography and characterized by mass‐sprectometry, NMR, IR, UV‐VIS and fluorescent spectroscopy. It was established that co‐cyclomerization of dinitriles is accompanied by electrophilic chlorination of 1,4‐diazepine ring by evolved Cl2 resulting in formation of dibenzosubporphyrazine [F8sPc1] with fused 6‐chloro‐5,7‐diphenyl‐6H‐1,4‐diazepine fragment. According to DFT modelling and 1H NMR data, a more stable diastereomer with an axial Cl atom is formed and no inversion of the 1,4‐diazepine ring is observed. Hydrolytic cleavage of the 1,4‐diazepine fragment in [F8sPc1] is observed upon chromatography or in the presence of a strong acid (CF3COOH) and leads to 2‐amino‐3‐benzamide substituted dibenzo subporphyrazine [F8sPc2]. Fluorescence of [F8sPc1] (ΦF=0.03) is ca 10 times lower than for [F12sPc] (ΦF=0.28) due to the combined effect of intramolecular charge transfer (ICT) from the donor diazepine ring to the acceptor sPc macrocycle and heavy atom effect of chlorine. Fluorescence of [F8sPc2] is almost completely quenched by ICT from −NH2 group to the electron‐deficient subporphyrazine core (ΦF<0.001), but addition of acid leads to protonation of the amino group and switch‐ON the fluorescence. Therefore, aminobenzamide substituted subporphyrazines can be considered as perspective pH‐sensitive fluorophores. [ABSTRACT FROM AUTHOR]

Continuous-wave diode lasers (DLs) with tunable emission wavelengths have become extensively used in various fields of analytical spectroscopy and diagnostics. Working in the near and mid-IR spectral region, tunable diode lasers are particularly effective in detecting simple molecules, making them invaluable for environmental monitoring, industrial process control, and diagnostics of subsonic and supersonic gas flows. However, the lack of commercial diode lasers operating in the spectral region shorter than 400 nm has restricted their applicability to elemental analysis, as many resonance lines of free atoms of elements lie in the region 250–400 nm. This review aims to highlight various applications of continuous diode lasers, which are lesser-known to analytical chemists. We briefly overview their main characteristics and discuss their advantages, enabling their successful implementation in traditional analytical spectroscopy tasks, as well as for diagnosing parameters of remote gas objects, including combustion processes in mixing gas flows. [ABSTRACT FROM AUTHOR]

We demonstrate the successful implementation of an artificial neural network (ANN) to eliminate detrimental spectral shifts imposed in the measurement of laser absorption spectrometers (LASs). Since LASs rely on the analysis of the spectral characteristics of biological and chemical molecules, their accuracy and precision is especially prone to the presence of unwanted spectral shift in the measured molecular absorption spectrum over the reference spectrum. In this paper, an ANN was applied to a scanning grating-based mid-infrared trace gas sensing system, which suffers from temperature-induced spectral shifts. Using the HITRAN database, we generated synthetic gas absorbance spectra with random spectral shifts for training and validation. The ANN was trained with these synthetic spectra to identify the occurrence of spectral shifts. Our experimental verification unambiguously proves that such an ANN can be an excellent tool to accurately retrieve the gas concentration from imprecise or distorted spectra of gas absorption. Due to the global shift of the measured gas absorption spectrum, the accuracy of the retrieved gas concentration using a typical least-mean-squares fitting algorithm was considerably degraded by 40.3%. However, when the gas concentration of the same measurement dataset was predicted by the proposed multilayer perceptron network, the sensing accuracy significantly improved by reducing the error to less than ±1% while preserving the sensing sensitivity. [ABSTRACT FROM AUTHOR]

In this study, the development and characterization of a plant-derived biopolymer, gum acacia, chemically modified by an herbal dye, red beetroot (Latin Beta vulgaris) has been presented. Red beetroot, a flowering plant with abundant phytochemicals, prevents diseases and produces colorful chromophores. Chromophores interact with incident intense electromagnetic field and thereby absorb radiation in ultraviolet and/or visible region of the spectrum, promoting low to high-level electron excitation between different energy states. Such transition influences variation in optical and electrical properties of the system. Optical properties of both biopolymer unmodified gum acacia specimen and after modification with red beet induced chromophore are investigated by UV–visible absorption spectroscopy. Pronounced light absorption is observed in the visible range of the spectrum compared to the unmodified specimen in which absorption is found to be observed in the deep ultraviolet range. Electrical characterization of the modified biopolymer with red beetroot extract suggests eviation from ideal dielectric relaxation obeying Debye mechanism. Electrical conductivity is found to be enhanced over pure specimen. These properties are eligible for application in energy storage devices, especially as a sensitizer in photovoltaic material which are ongoing extensive research area. [ABSTRACT FROM AUTHOR]

A series of nickel complexes in varying oxidation states were evaluated as precatalysts for the stereospecific cross-coupling of benzylic ethers. These results demonstrate rapid redox reactions of precatalysts, such that the oxidative state of the precatalyst does not dictate the oxidation state of the active catalyst in solution. These data provide the first experimental evidence for a Ni0 -NiII catalytic cycle for a stereospecific alkyl-alkyl cross-coupling reaction, including spectroscopic analysis of the catalyst resting state.

A contactless laser hygrometer based on light absorption by H2O molecules at 1392.5 nm is described. However, measurement results can be affected by optical noise when applied to an atmospheric tunnel or glass cuvette. The noises (occurring in the form of periodic fringes in the recorded spectrum) come from unexpected interference of the light beams reflected from surfaces of the windows or other optical elements. The method of their suppression is described in this article. It is based on wavelength modulation and signal averaging over the fringes period. Also, an experiment confirming the usefulness of this method is described here.

This work communicates cavity ring-down spectroscopy (CRDS) of methylidyne (CH) in a chemiluminescent plasma that is produced in a microwave cavity. Of interest are the rotational lines of the 0-0 vibrational transition for the A–X band and the 1-0 vibrational transition for the B–X band. The reported investigations originate from research on the CH radical in 1996, which constituted the first case of applying CRDS to the CH radical. The report also includes a recent analysis that shows excellent agreement of the measured and computed data, and it communicates CH line strength data. The CH radical is an important diatomic molecule in hydrocarbon combustion diagnosis and the analysis of stellar plasma emissions, to name just two examples of analytical plasma chemistry.

The applicability of UV—Vis spectrophotometry for evaluating the efficiency of complexation of β-cyclodextrin (βCD) or hydroxypropyl-β-cyclodextrin (HPβCD) with colorless and colored active substances and for controlling the fixation strength of the complexes on a cellulose-containing material was studied using the lysochrome diazo dye Sudan III (1-{[4-(phenyldiazenyl)phenyl]diazenyl}naphthalen-2-ol) as the model compound. Based on the results obtained, the fixation strength of the inclusion complexes with HPβCD is higher than that of the complexes with βCD. [ABSTRACT FROM AUTHOR]

The pH dependences of the photoluminescence of carbon dots synthesized by the hydrothermal method with polyfunctional and monofunctional (carboxylated and hydroxylated) surfaces have been studied. As a result of the analysis of the obtained photoluminescence and absorption spectra of aqueous suspensions of all studied types of carbon dots at different pH values, a significant effect of the acidity of the environment of nanoparticles on their optical properties was found. It has been found that the greatest changes in the spectral characteristics of absorption and photoluminescence of carbon dots with COOH, OH, and NH2 surface groups appear in the pH ranges of 2–5 and 8–12. The obtained results are explained are explained by the processes of protonation/deprotonation of the surface groups of carbon dots. [ABSTRACT FROM AUTHOR]

New version of diode laser (DL) absorption spectroscopy (DLAS) for determining the hot zone temperature is developed. The method is based on the combination of slow scanning of the radiation frequency of a probe DL around the absorption line of a test molecule of the medium and fast radiation frequency modulation with an amplitude on the order of the absorption line width. The developed version of the wavelength-modulation (WM-DLAS) is based on the two-beam differential scheme, the logarithmic signal conversion, and the registration of absorption at the first harmonic of the modulation frequency. The two-beam differential registration scheme and the logarithmic conversion of absorption signals have made it possible to reduce substantially the nonselective absorption of probe radiation and registration noise determined by excessive noise of lasers. The application of the first harmonic has ensured a higher sensitivity of the proposed version of WM-DLAS. Using the technique developed in this study, we have measured the temperature of water vapor in atmospheric air in the range 700–1100 K. The results are compared with the data obtained using commercial thermocouples. The difference in temperatures measured by a standard thermocouple and its mean value determined using the technique developed here is 40 K for a temperature of 1000 K and 30 K for 800 K. [ABSTRACT FROM AUTHOR]

In this study, copper oxide (CuO) nanoparticles (NPs) are synthesized by the sol–gel method and characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM) and tunneling electron microscopy (TEM) that all confirmed monoclinic crystalline structure with the particle size of ~ 24 nm. Then, different amounts of doxepin were loaded on the prepared NPs and loading efficacy was evaluated by the linear absorption spectroscopy and nonlinear optical measurements. In the DLS analysis, it is found that enhancing drug loading increases the hydrodynamic radius due to aggregation of NPs and formation of the drug corona around NPs, leading to the increase of light absorption. Moreover, increment of the particle absorption leads to enhancing population of the electrons in the upper level (conduction band) compared to the lower one (valence band) and promotes saturation of the absorption, as confirmed by the open-aperture Z-scan experiment. Finally, to describe the in vitro cellular cytotoxicity of the prepared CuO NPs, this nanomaterial was treated with PC3 human prostate cancer cells and the average growth of cells was monitored by a preliminary MTT assay. This investigation proved a noticeable decrease in the MTT signal compared to the untreated cells; therefore, CuO affects the metabolic activity of the performed cell line. This study shows that CuO can be used as a suitable carrier for a range of drugs, treating PC3 human prostate cancer cells. [ABSTRACT FROM AUTHOR]

Acenaphtho[1,2-k]fluoranthene (1) is synthesized via tandem cyclization during the dehydrofluorination of 1,4-di(1-naphthyl)-2,5-difluorobenzene (2) on activated γ-Al2O3. Presence of residual hydroxyl groups in alumina reduce the yield of target product 1 because of the side hydrolysis of fluoroarenes with the formation a product of partial cyclization, 9-(1-naphthyl)fluoranthen-8-ol (1b). The formation of negative ions (NI) of compounds 1 and 2 in the gas phase is studied by means of dissociative electron attachment (DEA) spectroscopy. Long-lived molecular NIs 1 and 2 are registered at the thermal energies of electrons, and patterns of their fragmentation are established. The adiabatic electron affinities of compounds 1 and 2 are estimated in the Arrhenius approximation and equal 1.17 ± 0.12 and 0.71 ± 0.07 eV, respectively, which agree with data from quantum chemical modeling at the level of the density functional theory (DFT). Electronic transitions for compounds 1 and 2 are studied via optical absorption and fluorescence spectroscopy. Fluorescence quantum yields are measured, and the resulting data are interpreted according to the time dependent DFT. The electrochemical properties of compounds 1, 1b, and 2 are studied via cyclic voltamperometry, and the levels of boundary molecular orbitals are estimated on the basis of their formal potentials of reduction and oxidation. [ABSTRACT FROM AUTHOR]

It is important to avoid the overestimation of absorption due to scattering when using absorption spectroscopy to measure scattering samples. We approached this issue by placing the sample inside an integrating sphere (IS) to collect the scattered light in all solid angles but encountered difficulty when determining the absorption coefficient from the absorbance because the light took various paths inside the IS and the sample. Therefore, by ray tracing inside the IS and the sample using Monte Carlo simulations (MC), we estimated the relationship between the absorption, scattering, anisotropy coefficients, and the measured absorbance. Scattering sample M, prepared by mixing polystyrene microspheres with trypan blue solution, and pure trypan blue solution for comparison were used as samples at various concentrations. MC reproduced the measurement results for the absorbance spectrum and its concentration dependence at 591 nm up to the measurement limit value. In addition, the saturated absorbance of sample M was lower than that of the trypan blue solution. This is because, from the distribution of distance d , light passed through the sample estimated by the MC, and more light with smaller d was detected due to scattering for higher concentration, resulting in a smaller increase in absorbance with the absorption coefficient. [ABSTRACT FROM AUTHOR]

We implemented a Microbubble Resonator (MBRs) as an opto-thermal transducer to reconstruct the absorption spectrum of a nanoparticle suspension through its temperature increase. The experimental configuration features the MBR as both the vial containing the suspension and the optical transducer, allowing for a sensitive ultra-compact system with a straightforward microfluidic integration. With respect to a previous publication, the active lock of the MBR resonance produced an order-of-magnitude improvement in the system performance and a smooth absorption reconstruction. Additionally, since the detection process is temperature-based, the measurement is intrinsically insensitive towards scattering spectrum, both of the particles and of the host liquid. These features make the MBR system an interesting candidate for the characterisation of extremely small samples in the context of medical diagnosis from whole biological samples, quality controls for food safety or chemical production processes, and, in general, for the measurement of absorption in opaque mediums.

The homoleptic cationic complex formed by reacting suitable manganese(II) salts with 2,2′-bipyridine-1,1′-dioxide (bipyO2) has been subjected to several studies in the past because of its peculiar absorption and electrochemical features. Here, the first single-crystal X-ray structure determination of a [Mn(bipyO2)3]2+ salt is reported, where the charge of the cation is balanced by perchlorate anions. The hydrated salt [Mn(bipyO2)3](ClO4)2 crystallizes in the monoclinic system (P21/n space group) and the asymmetric unit contains three cationic complexes and six perchlorate anions. The environment of the manganese(II) ions is best described as octahedral, with scarce variations among the three cations in the asymmetric unit. The bipyO2 ligands exhibit κ2 coordination mode, forming seven-membered metallacycles. The X-ray outcomes have been used as the starting point for DFT and TDDFT calculations, aimed to elucidate the charge transfer origin of the noticeable absorption in the visible range. The MLCT nature is confirmed by the hole and electron distributions associated with the spin-allowed transitions. DFT calculations on the related manganese(III) complex indicate that the geometry of [Mn(bipyO2)3]2+ changes only slightly upon oxidation, in agreement with the reversible electrochemical behaviour experimentally observed.

The electron configuration of flavin cofactors, FMN and FAD, is a critical factor governing the reactivity of NADPH-cytochrome P450 reductase (CPR). The current view of electron transfer by the mammalian CPR, based on equilibrium redox potentials of the flavin cofactors, is that the two electron-reduced FMN hydroquinone (FMNH2), rather than one electron-reduced FMN semiquinone, serves as electron donor to the terminal protein acceptors. However, kinetic and thermodynamic studies on the CPR species originated from different organisms have shown that redox potentials measured at distinct electron transfer steps differ from redox potentials determined by equilibrium titration. Collectively, previous observations suggest that the short-lived transient semiquinone species may carry electrons in diflavin reductases. In this work, we have investigated spectroscopic properties of the CPR-bound FAD and FMN reduced at 77 K by radiolytically-generated thermalized electrons. Using UV-vis spectroscopy, we demonstrated that upon cryo-reduction of oxidized yeast CPR (yCPR) containing an equimolar ratio of both FAD and FMN, or FAD alone, neutral semiquinones were trapped at 77 K. During annealing at the elevated temperatures, unstable short-lived neutral semiquinones relaxed to spectroscopically distinct air-stable neutral semiquinones. This transition was independent of pH within the 6.0-10.7 range. Our data on yeast CPR are in line with the previous observations of others that the flavin short-lived transient semiquinone intermediates may have a role in the electron transfer by CPR at physiological conditions.

Absorption spectroscopy has been widely used in gemstone societies as it enables the identification of the origin and post-treatment of gemstones in a non-destructive way. The infrared (IR) range is critical for studies of gemstones such as corundum, emerald, and diamond. Regarding the corundum sample, absorption peaks related to the -OH bond could be used as an index for heat-treatment detection, and different types of inclusions could be identified by analyzing the IR absorption spectrum. The most widely used method for measuring IR absorptions is Fourier-transform infrared spectroscopy (FTIR), which was designed based on the working of the Michelson interferometer. However, FTIR has a few limitations, such as a long measurement time and difficulty in sample placement, which limits its full automation capability. In this study, a mid-infrared (MIR) spectrometer relying on the upconversion phenomenon of non-linear crystals was used to measure the absorption spectra. Corundum with heat treatment features and/or with different common types of inclusions were measured by both transmission and reflection modes. After comparison with the FTIR spectra captured on the same sample set, the same target peaks could be captured with a shorter measurement time and easier operation. The developed MIR spectrometer could directly measure the absorption spectrum in the 2–4.5 µm (2200–5000 cm−1) range within a few seconds. Meanwhile, as both transmission and reflection modes were available, both loose and mounted gemstones could be measured, supporting the widespread use of this device in large-scale production and its ability to achieve full automation. [ABSTRACT FROM AUTHOR]

An experimental investigation of the dissociation of CO2 in a symmetric pin-to-pin dielectric barrier discharge (DBD) is presented. The reactor geometry allows for an accurate control of the number of filaments (microdischarges) and is used to study the impact of one single filament on the CO2 dissociation. We show the number of filaments per half cycle follows a power-law as a function of the injected power and does not depend on pressure, flow or other process parameters. It is shown that for pressures between 200 and 700 mbar approximately 0.5 W per filament is required and the charge transferred per filament remains constant at 0.5 nC. Furthermore, the dependence of CO2 conversion on only specific energy input (SEI) is shown to be valid down to a single filament. Additionally, by using quantum cascade laser absorption spectroscopy the absolute number of CO molecules produced per filament is measured and is found to be in the range from 5.1011 to 2.1012. The conversion degree of CO2 into CO is estimated to be lower than 0.1% within a single filament and increases with SEI. In the presence of a couple of filaments, the maximum energy efficiency obtained is 25%. A comparison of the conversion degrees in pin-to-pin DBD and plane-to-plane DBD configuration shows that these two reactor geometries follow the same power law. This means the geometry is not the most important parameter in CO2 dissociation in DBDs, but the SEI and thus the number of filaments ignited per unit of time. This result means that the dependence of conversion degree on the SEI can be extended to a single filament. This observation leads to the conclusion that the SEI appears to be valid as a universal scaling parameter down to very low values. [ABSTRACT FROM AUTHOR]

An optical sensor system based on wavelength modulation spectroscopy (WMS) was developed for atmospheric oxygen (O2) detection. A distributed feedback (DFB) laser with butterfly packaging was used to target the O2 absorption line at 760.89 nm. A compact multi-pass gas cell was employed to increase the effective absorption length to 3.3 m. To ensure the stability and anti-interference capability of the sensor in field measurements, the optical module was fabricated with isolation of ambient light and vibration design. A 1f normalized 2f WMS (WMS-2f/1f) technique was adopted to reduce the effect of laser power drift. In addition, a LabVIEW-based dual-channel lock-in amplifier was developed for harmonic detection, which significantly reduced the sensor volume and cost. The detailed detection principle was described, and a theoretical model was established to verify the effectiveness of the technique. Experiments were carried out to obtain the device's sensing performances. An Allan deviation analysis yielded a minimum detection limit of 0.054% for 1 s integration time that can be further improved to 0.009% at ~60 s. Finally, the reliability and anti-interference capability of the sensor system were verified by the atmospheric O2 monitoring. [ABSTRACT FROM AUTHOR]

An oxygen sensor system was developed based on Faraday modulation spectroscopy (FAMOS). In the system, a distributed feedback laser near 760.9 nm was used as the light source and a 30‐cm long gas cell was employed for gas absorption. The first harmonic was extracted by a commercial lock in amplifier for the derivation of concentration. Oxygen measurement experiments were conducted the performance of the sensor system was obtained. In addition, oxygen sensor system with wavelength modulation spectroscopy (WMS) scheme was developed with the same light source and gas cell for a direct comparison. Based on Allan deviation analysis, a detection limit of 0.186% for the WMS scheme and a detection limit of 0.108% for the FAMOS scheme were acquired at an averaging time of 1 s. The precisions can be further improved to 0.032% and 0.03% at an averaging time of 15 s, respectively. [ABSTRACT FROM AUTHOR]

A robust hierarchical model has been demonstrated for monitoring a wide range of neptunium concentrations (0.75–890 mM) and varying temperatures (10–80 °C) using chemometrics and feature selection. The visible–near infrared electronic absorption spectrum (400–1700 nm) of monocharged neptunyl dioxocation (Np(V) = NpO2+) includes many bands, which have molar absorption coefficients that differ by nearly 2 orders of magnitude. The shape, position, and intensity of these bands differ with chemical interactions and changing temperature. These challenges make traditional quantification by univariate methods unfeasible. Measuring Np(V) concentration over several orders of magnitude would typically necessitate cells with varying path length, optical switches, and/or multiple spectrophotometers. Alternatively, the differences in the molar extinction coefficients for multiple absorption bands can be used to quantify Np(V) concentration over 3 orders of magnitude with a single optical path length (1 mm) and a hierarchical multivariate model. In this work, principal component analysis was used to distinguish the concentration regime of the sample, directing it to the relevant partial least squares regression submodels. Each submodel was optimized with unique feature selection filters that were selected by a genetic algorithm to enhance predictions. Through this approach, the percent root mean square error of prediction values were ≤1.05% for Np(V) concentrations and ≤4% for temperatures. This approach may be applied to other nuclear fuel cycle and environmental applications requiring real-time spectroscopic measurements over a wide range of conditions. [ABSTRACT FROM AUTHOR]

This paper describes the design, development and spectroscopic studies of chip-scale Rb atomic vapour cell developed in the authors' laboratory. A compact magneto-optic package for the chip-scale Rb cell comprising of TEC integrated VCSEL source, silicon p-i-n photo detector and a hemispherical lens for light collimation is reported. The package is manufactured using commercial 3D printing technology. A PC based data acquisition system has been developed to provide real time analysis of the captured spectral data of the Rb chip by laser interrogation of the D1 hyperfine transition. Doppler broadened absorption resonance lines of technological importance have been recorded for transitions 85Rb(²S1/2 F=2→²P1/2 F′ =2,3) having absorption amplitude 1.24 V and FWHM 850 MHz and 87Rb(²S1/2 F=1 →²P1/2 F′ =1,2) has absorption amplitude 0.47 V and FWHM 567 MHz at cell temperature of 70 oC. Further, the chip-scale Rb atomic cell in the magneto-optical package will be explored to develop atomic sensors for space applications. [ABSTRACT FROM AUTHOR]

Passive radiative daytime cooling is an emerging technology contributing to carbon‐neutral heat management. Optically engineered materials with distinct absorption and emission properties in the solar and mid‐infrared range are at the heart of this technology. Owing to their low emissive power of about 100 W m−2 during daytime, substantial areas need to be covered with passive cooling materials or coatings to achieve a sizeable effect on global warming. Consequently, biocompatible materials are urgently needed to develop suitable coatings with no adverse environmental impact. It is shown how chitosan films with different thicknesses can be produced from slightly acidic aqueous solutions. The conversion to their insoluble form chitin in the solid state is demonstrated and the conversion is monitored with infrared (IR) and NMR spectroscopy. In combination with a reflective backing material, the films show below‐ambient temperature cooling capabilities with a suitable emissivity in the mid‐IR region and low solar absorption of 3.1–6.9%, depending on the film thickness. This work highlights the potential of chitosan and chitin as widely available biocompatible polymers for passive radiative cooling applications. [ABSTRACT FROM AUTHOR]

We report on measurements of rotational and vibrational temperature, velocity, and concentrations of nitric oxide (NO) in freestream flows at the T5 reflected shock tunnel at California Instistute of Technology. Quantities were measured at 50 kHz by tunable diode laser absorption spectroscopy using five lasers simultaneously to sample 27 quantum state-specific transitions. To isolate core flow measurements from the shear flow surrounding it, optical flow-cutter arms were designed. Two sets of arms with differing optical path lengths were used to assess freestream spatial uniformity. This study consists of nine total experiments ("shots") spanning four nominal conditions with reservoir enthalpy 8-21 MJ/kg and flow velocity 3.5-5.5 km/s. Freestream measurements generally imply thermal equilibrium of the rotational and vibrational temperatures except at lower-enthalpy conditions. We compare temperature measurements with predictions from five species air simulations and find reasonable agreement at lower-enthalpy conditions but underprediction of NO concentrations. At higher-enthalpy conditions, we observed transitory agreement in temperature but overprediction of NO concentrations. Measured and simulated velocity generally agree well across all conditions. Carbon monoxide, water, and potassium were also detected in the T5 flow, and their concentrations are reported where relevant. [ABSTRACT FROM AUTHOR]

A versatile portable tunable diode laser based measurement system for measuring elevated concentrations of hydrogen cyanide (HCN) in a time-resolved manner is developed for application in the fire environment. The direct absorption tunable diode laser spectroscopy (DA-TDLAS) technique is employed using the R11 absorption line centered at 3345.3 cm−1 (2989.27 nm) in the fundamental C–H stretching band (ν1) of the HCN absorption spectrum. The measurement system is validated using calibration gas of known HCN concentration and the relative uncertainty in measurement of HCN concentration is 4.1% at 1500 ppm. HCN concentration is measured with a sampling frequency of 1 Hz, in gas sampled from 1.5 m, 0.9 m, and 0.3 m heights in the Fireground Exposure Simulator (FES) prop at the University of Illinois Fire Service Institute, Champaign, Illinois. The immediately dangerous to life and health (IDLH) concentration of 50 parts per million (ppm) is exceeded at all the three sampling heights. A maximum concentration of 295 ppm is measured at the 1.5 m height. The HCN measurement system, expanded to measure HCN simultaneously from two sampling locations, is then deployed in two full-scale experiments designed to simulate a realistic residential fire environment at the Delaware County Emergency Services Training Center, Sharon Hill, Pennsylvania. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

Interactional study of triphenylmethane-based cationic dye i.e., basic violet-4 dye (BV) in the mixed-micellar system of two anionic surfactants viz. sodium dodecyl sulfate (NaDS) and sodium stearate (NaS) is encompassed in this manuscript. The composite micelles of nonionic surfactant triton X-100 (TX) served as better colloidal carriers to facilitate aggregation, deep penetration, and stability of dye molecules than single surfactants. The thermodynamics of the micellization was assessed conductometrically, whereas the extent of dye-surfactant interaction was quantified spectroscopically. The nonionic/anionic mixture favored micellization and lowered critical micellar concentration (CMC). Furthermore, it is observed that dye partitioning, binding, and micellization were spontaneous processes. The thermodynamic parameters including entropy, enthalpy, and Gibb's free energy of micellization along with the determination of the CMC, degree of ionization are also explained. The parameters in terms of partition constant, partition coefficient, binding constant, Gibb's free energy of partition, and binding were calculated from differential absorption spectroscopy. The comparative study revealed that NaDS/TX showed superior performance in dye penetration as compared to NaS/TX system. [ABSTRACT FROM AUTHOR]

Creating a supersonic jet in the laboratory is both a challenging and an expensive task. The supersonic flow is sensitive to the shape of the wall bounding it because a shock could be developed at the sharp edges. Moreover, the growth of boundary layer, within and outside the nozzle, makes the design of a convergent-divergent nozzle a sophisticated work. The present work proposes an optimization algorithm that is believed to be efficient in constructing a nozzle contour to deliver a shock-free radially uniform flow at the exit plane. The steepest descent optimization technique is employed to obtain the shape with minimum radial velocity at the outlet, along with restriction on the inlet angle, i.e., the angle of divergence immediately downstream the throat. Three different ways of implementing the constraints are discussed and compared with the experimental results after fabricating the nozzle. The optimized nozzle shows a potential core of 7 throat diameters height at the nozzle exit and an axial extent of 28 throat diameters downstream the exit plane. Further, the nozzle appears to operate efficiently even after increasing the nominal total temperature by 25% or decreasing it by 50%. [ABSTRACT FROM AUTHOR]

This paper reports on a compact and lightweight sensor for analysis of gases/vapors by means of a MEMS-based pre-concentrator coupled to a miniaturized infrared absorption spectroscopy (IRAS) module. The pre-concentrator was utilized to sample and trap vapors in a MEMS cartridge filled with sorbent material and to release them once concentrated by fast thermal desorption. It was also equipped with a photoionization detector for in-line detection and monitoring of the sampled concentration. The vapors released by the MEMS pre-concentrator are injected into a hollow fiber, which acts as the analysis cell of the IRAS module. The miniaturized internal volume of the hollow fiber of about 20 microliters keeps the vapors concentrated for analysis, thus allowing measurement of their infrared absorption spectrum with a signal to noise ratio high enough to identify the molecule, despite the short optical path, starting from sampled concentration in air down to parts per million. Results obtained for ammonia, sulfur hexafluoride, ethanol and isopropanol are reported to illustrate the sensor detection and identification capability. A limit of identification (LoI) of about 10 parts per million was validated in the lab for ammonia. The lightweight and low power consumption design of the sensor allowed operation onboard unmanned aerial vehicles (UAVs). The first prototype was developed within the EU Horizon 2020 project ROCSAFE for the remote assessment and forensic examination of a scene in the aftermath of industrial or terroristic accidents. [ABSTRACT FROM AUTHOR]

In many watersheds, runoff occurring with snowmelt brings the largest pulse of dissolved organic matter (DOM) from soils to streams. Yet, exactly how soil and stream DOM fractions are altered as snowmelt timing changes is not well understood. We studied the optical character of DOM as it moved through a first‐order northern hardwood watershed through the snowmelt period. While stream dissolved organic carbon (DOC; mean = 4.6 mg C L−1) concentrations were not correlated with snowmelt flushing, stream DOM appeared humic‐like throughout the study period (humification index, HIX; mean = 10.9). Within the stream, we measured seasonal increases in an inverse index of DOM molecular weight and processing (spectral slope, S275–295; range = 0.0102–0.0214) and in an index of recently derived DOM (Biological Index, BIX; range = 0.2–1.1). We measured a decrease in an inverse index of DOM oxidation (ratio of Peak C to Peak A, or C/A; range = 0.59–2.01) through the snowmelt period. Stream BIX and C/A tracked those measured in the north aspect soils throughout the study. C/A was unique as it decreased from source to stream, likely reflecting the diagenesis of DOM through soils. These data suggest that changes in the timing of snowmelt and hydrologic connectedness within a watershed affect seasonal changes in stream DOM character. We suggest that watersheds with deep glacial till parent materials have stream connectivity limited by subsurface flow paths, with stream DOM character being determined largely by slow melt and a longer period of infiltration. Key Points: Differences in snowpack duration influenced the source of dissolved organic matter (DOM) and its character in the stream of the same watershedThe character of stream DOM was correlated with that of DOM in soil water from north facing aspects within the watershedFluorescence index peak ratio C/A was able to distinguish DOM from different sources along a leaf leachate‐soil‐stream continuum [ABSTRACT FROM AUTHOR]