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Investigations on the reactions of uranium oxide molecules with CO offer new inspiration for the design of promising high-efficiency catalysts for CO activation using actinide materials. Herein, we contribute a combined matrix-isolation infrared spectroscopic and theoretical study of CO oxidation to CO2on uranium dioxide (UO2) molecules in solid argon. The reaction intermediate O2U(η1-CO) is generated spontaneously at the bands of 1893.0, 870.6, and 801.3 cm–1during codeposition and annealing. Upon the following irradiation, CO2is substantially produced by the consumption of O2U(η1-CO), indicating the catalytic conversion of CO to CO2through the intermediate O2U(η1-CO). In C18O isotopic substitution experiments, the yields of 16OC18O convincingly confirm that one of the oxygen atoms in CO2derives from UO2. The reaction pathways are discussed based on the theoretical and experimental results.

•Raman imaging in tandem with PCA-LDA applied to detect aflatoxins in corn kernels.•Mean spectra extracted from endosperm side and germ side (embryo area) separately.•Raman peaks of aflatoxin-negative and -positive classes of corn kernels identified.•Different types of models established, compared and the optimal models identified.

Investigations on the structures and bonding properties of metal carbonyl compounds provide fundamental understandings on the origin of small-molecule activations. Herein, the geometry and bonding trends of a series of isovalent metal oxocarbonyl complexes O2M(η1-CO) (M = Cr, Mo, W, Nd, and U) were studied by combined matrix-isolation infrared spectroscopy and advanced quantum chemical calculations. The title complexes present red shift of C–O stretching bands in the range from 122 to 244 cm–1, indicating the difference of CO activation ability for the series of isovalent metal dioxides. Density functional theory calculations predict T-shaped structures with a C2vsymmetry for all the title molecules. O2Nd(η1-CO) bears little resemblance to the other complexes in bonding characters because of the weak interactions between the NdO2and CO moiety. For the other complexes, natural localized molecular orbital analysis reveals a gradual increase of covalent character in M–CO bonds along the metal series Cr → Mo → W→ U. Energy decomposition analysis with natural orbitals for chemical valence calculations demonstrates that the M–CO bonding patterns conform to the conventional Dewar–Chatt–Duncanson motif. The contributions from orbital interactions in total attractions increase from Cr (41.7%) to U (52.7%). The breakdown of the orbital term into pairwise interactions shows that contributions of the M ← CO σ donation decrease from Cr (59.2%) to U (28.4%), while the M → CO π* backdonation increases significantly from Cr (23.8%) to U (67.3%). The more effective overlap and the better energy matching of U 5f and U 6d valence orbitals with CO π* orbitals result in much stronger U → CO π backdonation than the other metal elements.

Fipronil, an insecticide commonly used to rid livestock of fleas, lice and ticks, is banned from use in the food industry in the U.S. and European Union. The incident of poultry eggs tainted with fipronil in 2017 caused recall of millions of eggs affecting more than 40 countries. Since commercial application of fipronil is as a spray, its most immediate and most rapid detection is on surfaces. A partial least squares regression (PLSR) model was developed with infrared (IR) data (750–2000 cm−1). The relationship between the peak intensity and the fipronil concentration is linear. The method finds a correlation coefficient R2= 0.98 in the calibration set and R2= 0.96 in the validation set. The IR spectral assignments were made for 18 vibrational modes (750–2500 cm−1). Eighteen Raman vibrational modes in the pure fipronil have also been found (500–2500 cm−1). The molecular sites in vibrational modes for C–C and C–N stretching in both IR and Raman spectra (1250–1750 cm−1) are similar, yet the pattern of their relative intensities in both are different. Differences in the relative spectral intensity at wavenumbers 1319, 1423, 1506, and 1634 cm−1could also be less affected by potential interferences from matrix and background signals. The dual modality IR and Raman measurements can provide a unique and highly specific fingerprint of fipronil identity.

Identifying reaction intermediates in gas-phase investigations will provide understanding for the related catalysts in fundamental aspects including bonding interactions of the reaction species, oxidation states (OSs) of the anchored atoms, and reaction mechanisms. Herein, carbon monoxide (CO) oxidation by praseodymium monoxide (PrO) molecules has been investigated as a model reaction in solid argon using matrix-isolation IR spectroscopy and quantum-chemical calculations. Two reaction intermediates, OPr(η1-CO) and OPr(η2-CO), have been trapped and characterized in argon matrixes. The intermediate OPr(η2-CO) shows an extremely low C–O stretching band at 1624.5 cm–1. Quantum-chemistry studies indicate that the bonding in OPr(η1-CO) is described as “donor–acceptor” interactions conforming to the Dewar–Chatt–Duncanson motif. However, the bonding in OPr(η2-CO) results evidently from a combination of dominant ionic forces and normal Lewis “acid–base” interactions. The electron density of the singly occupied bonding orbital is strongly polarized to the CO fragment in OPr(η2-CO). Electronic structure analysis suggests that the two captured species exhibit Pr(III) OSs. Besides, the pathways of CO oxidation have been discussed.

Despite continuing and burgeoning interest in americium (Am) coordination chemistry in recent years, investigations of the electronic structures and bonding chemistry of high oxidation state americium complexes and their implications for minor actinide separation remain relatively less explored to date. Here, we used density functional theory (DFT) to create high oxidation states of americium but experimentally feasible models of Am(V) and Am(VI) complexes of phenanthroline ligand (DAPhen) as [AmO2(L)]1+/2+and [AmO3(L)]1+(L = 2,9-bis[(N,N-dimethyl)-carbonyl]-1,10-phenanthroline (oxo-DAPhen, LO) and 2,9-bis[(N,N-dimethyl)-thio-carbonyl]-1,10-phenanthroline (thio-DAPhen, LS)), meanwhile comparing these with [UO2(L)]2+. On the basis of the calculations, the Am(V) and Am(VI) oxidation state are thermodynamically feasible and can be stabilized by DAPhen ligands. From a comparative study, the strength of thio-DAPhen in the separation of high oxidation state Am emerges better than does oxo-DAPhen, which relates to the nature, energy level, and spatial arrangement of their frontier orbitals. This study provides fundamental knowledge toward understanding the transuranic separations processes, which has implications in designing new, more selective extraction processes for the separation of Am from curium (Cm) as well as lanthanide.

Elucidating molecular-level interactions between dihydrogen (H2) and uranium oxides reveals fundamental insights into the intrinsic H2activation mechanisms underlying processes such as heterogeneous catalysis over uranium oxides and corrosion of uranium induced by H2. Herein, the reactions of H2with uranium monoxide (UO) molecules have been investigated via a combination of matrix-isolation infrared spectroscopy and quantum chemical calculations. A side-on bonded H2complex, OU(η2-H2), is identified at 3733.7 and 800.3 cm–1. This species is regarded as a crucial intermediate along H2activation pathways. Bonding analysis reveals cooperative U(π5f/6d) → H2(σ*) π//backdonation and U ← H2(σ) σ donation in OU(η2-H2) that facilitate the activation of the H2moiety. Upon λ > 550 nm photoirradiation, OU(η2-H2) isomerizes into H2UO, indicating the homolytic H2cleavage on UO. Mechanistic details of H2adsorption and dissociation on UO molecules have been further elucidated.

We designed new mini‐LED backlight structure using a transflective film which can control the amounts of light transmitted directly and reflected to the substrate. The optical distance is reduced by 1.2mm in this structure. In addition, the luminous efficiency is enhanced by 20% with the high‐reflection layer design on the substrate.

The laser induced breakdown spectroscopy (LIBS) technique is an effective method to detect material composition by obtaining the plasma emission spectrum. The overlapping peaks in the spectrum are a fundamental problem in the qualitative and quantitative analysis of LIBS. Based on a curve fitting method, this paper studies an error compensation method to achieve the decomposition and correction of overlapping peaks. The vital step is that the fitting residual is fed back to the overlapping peaks and performs multiple curve fitting processes to obtain a lower residual result. For the quantitative experiments of Cu, the Cu–Fe overlapping peaks in the range of 321–327 nm obtained from the LIBS spectrum of five different concentrations of CuSO_4·5H_2O solution were decomposed and corrected using curve fitting and error compensation methods. Compared with the curve fitting method, the error compensation reduced the fitting residual about 18.12–32.64% and improved the correlation about 0.86–1.82%. Then, the calibration curve between the intensity and concentration of the Cu was established. It can be seen that the error compensation method exhibits a higher linear correlation between the intensity and concentration of Cu, which can be applied to the decomposition and correction of overlapping peaks in the LIBS spectrum.

We designed new mini‐LED backlight structure using a transflective film which can control the amounts of light transmitted directly and reflected to the substrate. The optical distance is reduced by 1.2mm in this structure. In addition, the luminous efficiency is enhanced by 20% with the high‐reflection layer design on the substrate.

This study uses a point-scan Raman spectral imaging system for quantitative detection of melamine in milk powder. A sample depth of 2 mm and corresponding laser intensity of 200 mW were selected after evaluating the penetration of a 785 nm laser through milk powder. Horizontal and vertical spatial resolutions of 0.25 and 0.5 mm were selected for effective detection of melamine particles mixed with milk powder. The selected imaging parameters were used to quantitatively detect melamine concentration in milk powder. Ten different concentrations of melamine in milk (0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, and 1 %- w/w) were prepared by mixing each mixture of melamine and milk powder in an acoustic mixer for 15 min, and seven sub-samples of each concentration were imaged. Each sub-sample image was acquired over a 45 mm × 45 mm surface area. Background-corrected Raman spectral images were converted into binary images and an intensity threshold value of 400 was applied to convert melamine pixels into black pixels and milk pixels into white pixels (background). At least one melamine pixel was detected in every sub-sample across all ten concentration levels except for one sub-sample at the 0.005 % concentration. It was found that the method developed in this study can detect melamine particles present at concentrations as low as 0.005 %. A linear relation was established between the detected melamine concentrations and the actual concentrations of the mixtures, with correlation coefficient of 0.99. The results show that the method developed in this study can be used for non-destructive quantitative prediction of melamine in milk powder to minimum concentration level of 0.005 %.

This research developed a Raman chemical imaging method for detecting multiple adulterants in skim milk powder. Ammonium sulfate, dicyandiamide, melamine, and urea were mixed into the milk powder as chemical adulterants in the concentration range of 0.1–5.0 %. A Raman imaging system with a 785-nm laser was used to acquire hyperspectral images in the wavenumber range of 102–2,538 cm−1for a 25 × 25 mm2area of each mixture. A polynomial curve-fitting method was used to correct for the fluorescence background in the Raman images. An image classification method was developed based on single-band fluorescence-free images at unique Raman peaks of the adulterants. Raman chemical images were created to visualize identification and distribution of the multiple adulterant particles in the milk powder. A linear relationship was found between adulterant pixel number and adulterant concentration, demonstrating the potential of this Raman chemical imaging method for quantitative analysis of adulterants in the milk powder.

In this research, four chemicals, urea, ammonium sulfate, dicyandiamide, and melamine, were mixed into liquid nonfat milk at concentrations starting from 0.1% to a maximum concentration determined for each chemical according to its maximum solubility, and two Raman spectrometers-a commercial Nicolet Raman system and an in-house Raman Chemical Imaging (RCI) system-were used to acquire Raman shift spectra for these mixture samples. These chemicals are potential adulterants that could be used to artificially elevate protein measurements of milk products evaluated by the Kjeldahl method. Baseline subtraction was employed to eliminate milk intensity, and the normalized Raman intensity was calculated from the specific Raman shift from the spectrum of solid chemical. Linear relationships were found to exist between the normalized Raman intensity and chemical concentrations. The linear regression coefficients (R2) ranged from 0.9111 to 0.998. Although slightly higher R2values were calculated for regressions using spectral intensities measured by the Nicolet system compared to those using measurements from the RCI system, the results from the two systems were similar and comparable. A very low concentration of melamine (400 ppm) in milk was also found to be detectable by both systems. Raman sensitivity of Nicolet Raman system was estimated from normalized Raman intensity and slope of regression line in this study. Chemicals (0.2%) were dissolved in milk and detected the normalized Raman intensity. Melamine was found to have the highest Raman sensitivity, with the highest values for normalized Raman intensity (0.09) and regression line slope (57.04).

This study investigated the potential of Raman chemical imaging for simultaneously detecting multiple adulterants in milk powder. Potential chemical adulterants, including ammonium sulfate, dicyandiamide, melamine, and urea, were together mixed into nonfat dry milk in the concentration range of 0.1%-5.0% for each adulterant. A benchtop point-scan Raman imaging system using a 785-nm laser was assembled to acquire hyperspectral images in the wavenumber range of 102-2538 cm-1. Each mixture was imaged in an area of 25×25 mm2with a spatial resolution of 0.25 mm. Selfmodeling mixture analysis (SMA) was used to extract pure component spectra, by which the four types of the adulterants were identified at all concentration levels based on their spectral information divergence values to the reference spectra. Raman chemical images were created using the contribution images from SMA, and their use to effectively visualize identification and spatial distribution of the multiple adulterant particles in the dry milk was demonstrated.