Selective Electrochemical Hydrogenation of Phenol with Earth-abundant Ni-MoO2 Heterostructured Catalysts: Effect of Oxygen Vacancy on Product Selectivity.

Herein, we report highly efficient carbon supported Ni-MoO2 heterostructured catalysts for the electrochemical hydrogenation (ECH) of phenol in 0.10 M aqueous sulfuric acid (pH 0.7) at 60 °C. Highest yields for cyclohexanol and cyclohexanone of 95 % and 86 % with faradaic efficiencies of ∼50 % are obtained with catalysts bearing high and low densities of oxygen vacancy (Ov ) sites, respectively. In situ diffuse reflectance infrared spectroscopy and density functional theory calculations reveal that the enhanced phenol adsorption strength is responsible for the superior catalytic efficiency. Furthermore, 1-cyclohexene-1-ol is an important intermediate. Its hydrogenation route and hence the final product are affected by the Ov density. This work opens a promising avenue to the rational design of advanced electrocatalysts for the upgrading of phenolic compounds.

Nondestructive characterization of diseased Chinese chive leaves using X-ray intensity ratios with microbeam synchrotron radiation X-ray fluorescence spectrometry.

The Chinese chive (Allium tuberosum) is a core crop grown in Kochi Prefecture, Japan. However, withering symptoms occur during greenhouse growing, which have a negative impact on crop management Chinese chive leaves with physiological disorders (PD) or necrotic streak disease (ND) present with withering as typical blight symptoms. Excess or deficiency of elements may cause such withering in Chinese chive leaves with PD. Therefore, visualizing the elemental distribution in plant bodies may help clarify the cause of this withering. In this study, using synchrotron radiation X-ray fluorescence (SR-XRF) imaging, we examined the elemental distribution conditions in healthy Chinese chive leaves without withering, those that withered due to PD, and those that withered due to ND. Segmentation analysis of inductively coupled plasma-optical emission spectroscopy (ICP-OES) was performed on the SR-XRF imaged Chinese chive leaves and the data from the two analytical methods were compared. SR-XRF imaging provided more detailed data on elemental distribution compared with segmentation analysis using ICP-OES. Based on the SR-XRF imaging results, the X-ray intensity ratios for Ca/K, Fe/Mn, and Zn/Cu were calculated. These findings support that the Ca/K, Fe/Mn, and Zn/Cu X-ray intensity ratios can be used in the early detection of withered leaves and to predict the factors causing withering.

Nondestructive discrimination of black ceramic prints on automotive glasses by portable X-ray fluorescence spectrometer.

Automotive glasses are important forensic evidence often recovered from crime scenes. Black ceramic prints on automotive glasses contains various elements in high concentrations. A portable X-ray fluorescence spectrometer (pXRF) allows an instant and nondestructive analysis of various elements. In this study, the Bruker Tracer 5 g was used as the pXRF equipment. The NIST SRM612 glass standard was used to determine the limit of detection (LODs) of a pXRF and its optimal conditions. The acceleration voltages of 15, 30, and 50 kV were appropriate for measuring Si Kα (1.740 keV)-Ni Kα (7.473 keV), Cu Kα (8.042 keV)-Pb Lα (10.552 keV), and after Bi Kα (10.839 keV), respectively. The pXRF was used to compare 37 black ceramic prints on automotive glasses from the known source. The samples were divided into two groups: the Pb type and the Bi type. The samples were compared in pairs. The most appropriate and effective indicators for discriminating between the Pb and Bi type of black ceramic prints on automotive glasses were Zr Kα /Pb Lα and Cu Kα /Cr Kα for the Pb type, and Zr Kα /Bi Lα and Cu Kα /Crα for the Bi type, respectively. The samples were compared with other elements detected by pXRF to further discriminate them. 98.9% of all pairs were successfully discriminated. Results showed that black ceramic prints on automotive glasses are able to be discriminated by pXRF.

Depth elemental imaging of forensic samples by confocal micro-XRF method.

Micro-XRF is a significant tool for the analysis of small regions. A micro-X-ray beam can be created in the laboratory by various focusing X-ray optics. Previously, nondestructive 3D-XRF analysis had not been easy because of the high penetration of fluorescent X-rays emitted into the sample. A recently developed confocal micro-XRF technique combined with polycapillary X-ray lenses enables depth-selective analysis. In this paper, we applied a new tabletop confocal micro-XRF system to analyze several forensic samples, that is, multilayered automotive paint fragments and leather samples, for use in the criminaliztics. Elemental depth profiles and mapping images of forensic samples were successfully obtained by the confocal micro-XRF technique. Multilayered structures can be distinguished in forensic samples by their elemental depth profiles. However, it was found that some leather sheets exhibited heterogeneous distribution. To confirm the validity, the result of a conventional micro-XRF of the cross section was compared with that of the confocal micro-XRF. The results obtained by the confocal micro-XRF system were in approximate agreement with those obtained by the conventional micro-XRF. Elemental depth imaging was performed on the paint fragments and leather sheets to confirm the homogeneity of the respective layers of the sample. The depth images of the paint fragment showed homogeneous distribution in each layer expect for Fe and Zn. In contrast, several components in the leather sheets were predominantly localized.

Nondestructive discrimination of red silk single fibers using total reflection X-ray fluorescence spectrometry and synchrotron radiation X-ray fluorescence spectrometry.

In a strangulation case, when a necktie is used as a murder weapon, the dyed silk single fiber becomes an important evidence sample to solve the crime. Dyed silk single fibers contain elements, such as Cr and Co, which are obtained from dyeing using metal mordants. Currently, there are no nondestructive and sufficiently sensitive elementary analytical methods for the forensic analysis of single fibers. Therefore, in this study, eight commercially available red silk samples were collected and used for total reflection X-ray fluorescence (TXRF) and synchrotron radiation X-ray fluorescence (SR-XRF) spectrometry. Benchtop TXRF detected both S in the silk protein and Cl and Ca, which are elements absorbed from the environment by silkworms, but also Cr, which is a dyeing derivative for metal mordants. The presence of Cr and Zn, in addition to the Zn/Cr signal intensity ratios, was reported to be particularly useful identifiers. In SR-XRF, the presence of Cr, Co, Zn, and Br and the Zn/Cr signal intensity ratios were reported to be useful discriminating indicators. In this study, the nondestructive discrimination capabilities of TXRF and SR-XRF measurements for the samples were found to be 85.7% and 100%, respectively. Therefore, we propose a combination of TXRF and SR-XRF as a new nondestructive single fiber identification method for forensic science. Moreover, if partial destruction of a single fiber is allowed, the observation of the cross section and micro-Fourier-transform infrared spectroscopy measurements is useful for identifying red silk fibers.

Nondestructive Mineral Imaging of Chinese Chive Leaves Withered by Physiological Damage Using Microbeam Synchrotron Radiation X-Ray Fluorescence Analysis.

A significant problem encountered in Chinese chives (Allium tuberosum) grown in greenhouses is the reduction in the yield and quality due to symptoms of withered leaf tips. Withered leaf tips of three Chinese chive cultivars were nondestructively analyzed by microbeam synchrotron radiation X-ray fluorescence (µ-SR-XRF) imaging. Dead, wilting, and healthy parts of the leaves exhibited significant variations in the mineral composition. The Ca/K X-ray intensity ratios were significantly increased with the degree of withering.

Analysis of Single Synthetic Fibers Using a Portable Total Reflection X-ray Fluorescence Spectrometer.

In this study, single synthetic fibers obtained from several textile products were analyzed by a portable total reflection X-ray fluorescence spectrometer. Characteristic elements, which would originate from such materials as catalysts, delustering agents, and dyes used for manufacturing synthetic fibers, were detected from single synthetic fiber samples, and the difference in the types of characteristic elements among the single synthetic fiber samples was observed.

An Evaluation of Total Reflection X-Ray Fluorescence as a Tool for Forensic Discrimination of Single Polyester Fibers.

Total reflection X-ray fluorescence (TXRF) spectrometry was applied to a forensic discrimination of single polyester fibers. In a non-destructive direct measurement of 5 mm long single fibers used for forensic references, trace metallic elements such as Ti, Sb, Ge, Mn, and Co, found in additives and catalyst residues, were detected using a benchtop TXRF spectrometer. The individual elemental compositions of the fibers were identified, and correlations between the compositions and manufacturers were established using principal component analysis (PCA). Black polyester fibers sampled from the car trunk mats were also analyzed. Several fibers were found to contain both Sb and Ge, elements that characterize different polymerization catalysts; this indicates that the fibers were composed of recycled materials. The TXRF and SR-µXRF spectra showed similar patterns for the fiber samples that were analyzed.

Nondestructive Differentiation of Polyester Single White Fibers Using Synchrotron Radiation Microbeam X-ray Fluorescence Spectrometry with Vertical Focusing.

In this study, the nondestructive differentiation of individual white polyester clothing fibers was accomplished via synchrotron radiation microbeam X-ray fluorescence (SR-µ-XRF) analysis. SR-µ-XRF with vertical focusing is a useful nondestructive method for the analysis of a single polyester clothing fiber. Kirkpatrick-Baez (KB) mirror was used to vertically focus 20 keV X-rays for the analysis of 22 individual white polyester fibers taken from clothing commonly sold in Japan. SR-µ-XRF with a vertical focused 2 µm (V) × 300 µm (H) beam was approximately 12.8 times more sensitive than SR-XRF with an unfocused 300 µm (V) × 300 µm (H) beam for the detection of elements in single fibers. The minimum detection limits (MDLs) of the SR-µ-XRF method were 8.15 ppm for Cl and 0.06 ppm for Br. In addition to Ti in TiO2 delustering agents, Zr and Nb impurities in the delustering agents were detected in individual fibers. Sb from a polymerization catalyst and Co from a transesterification catalyst were also detected in individual fibers. Comparing the Ti Kß /Sb Lα,ß and Zr Kα /Nb Kα X-ray intensity ratios was a useful way to distinguish individual clothing fibers, and 98% of the fibers were differentiated when additional trace elements were used as discrimination indicators.

New layered perovskite family built from [CeTa2O7]- layers: coloring mechanism from unique multi-transitions.

A Ce3+-based layered perovskite compound, Dion-Jacobson type RbCeTa2O7, has been discovered for the first time by introducing only a trivalent cerium ion to form [CeTa2O7]- layers. The unique green color was experimentally and theoretically ascribed to two charge transfer transitions of ligand-to-metal O2p → Ce4f and metal-to-metal Ce4f → Ta5d.

Forensic Comparison of Automotive Aluminum Wheel Fragments Using Synchrotron Radiation X-ray Fluorescence with 18- and 116-keV Excitation X-rays.

The performance of synchrotron radiation X-ray fluorescence (SR-XRF) spectrometry for nondestructive discrimination of small fragments of automotive aluminum wheels was studied. Fragments (< 500 × 500 µm2 ) of 45 kinds of wheels were first analyzed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and then by SR-XRF. Despite the Mg/Al intensity ratio being a useful identification index, SEM-EDS was not efficient enough because of the absence of other meaningful indicators of comparison. Conversely, pairwise comparison was conducted and a 92.9% identification was achieved via SR-XRF using 18-keV X-rays. Trace heavy elements in the high-energy region were detected by SR-XRF using 116-keV X-rays, and an 82.9% identification was obtained. Combined use of 18- and 116-keV X-rays allowed 98.2% identification. Hence, SR-XRF is a powerful tool for nondestructive discrimination of automotive aluminum wheels with high precision using trace elements in a wide energy region.

Quantitative Determination of the Effective Mn4+ Concentration in a Li2TiO3:Mn4+ Phosphor and Its Effect on the Photoluminescence Efficiency of Deep Red Emission.

Obtaining highly efficient photoluminescence with Mn4+-activated phosphors, which have been extensively studied in diverse lighting devices, requires the precise control of the manganese valence states. However, this control is difficult to achieve because manganese ions can have various valence states ranging from divalent to heptavalent. Additionally, the concentrations of Mn ions in each valence state, especially the effective Mn4+ concentration, have never been quantitatively determined in a phosphor crystal lattice. The relationship between the effective Mn4+ concentration and the luminescence properties of Mn4+-activated phosphors is of current interest for improving the phosphor properties. In the present study, the effective Mn4+ concentration in Li2TiO3:Mn4+ (LTO:Mn) phosphors prepared by the sol-gel method with heating at various temperatures was quantitatively analyzed by X-ray absorption near-edge spectroscopy. Moreover, the effect of the existence of Mn2+, Mn3+, and Mn4+ ions on the photoluminescence efficiency was investigated. The effective Mn4+ concentration was found to be over 60% in all phosphor samples. The quantum efficiencies (QEs) of all LTO:Mn phosphors strongly depend on the effective Mn4+ concentration. In particular, the LTO:Mn phosphor prepared by heating at 800 °C (LTO:Mn@800) contained the highest effective Mn4+ concentration of 98.1% and exhibited the highest internal QE of 31.6%. The results of this work provide new and important insights for the development of Mn4+-activated phosphors with high efficiency.

Application of total reflection X-ray fluorescence spectrometry to small glass fragments.

Total reflection X-ray fluorescence spectrometry (TXRF) has been applied for trace elemental analysis of small glass fragments. A small glass sample (a fragment with weight less than 0.5 mg) was decomposed by 100 microg of HF/HNO3 acid; the material was condensed to 10 microl and was dried on a Si wafer. Since the size of the dried residue on the Si wafer was less than 1 cm in diameter, an incident X-ray beam with about 1 cm in width could effectively excite elemental components in such a small glass fragment. The precision of the present technique was checked by analyzing the glass fragments (<0.5 mg) from NIST SRM612; the relative standard deviations (RSD) of less than 8.1% were achieved for elemental ratios that were normalized by Sr. Fragments (<0.5 mg) obtained from 23 figured sheet glasses were used as samples for estimating the utility of this technique to forensic discrimination. Comparison of five elemental ratios of Ti/Sr, Mn/Sr, Zn/Sr, Rb/Sr, and Pb/Sr calculated from X-ray fluorescence spectra was effective in distinguishing glass fragments that could not be differentiated by their refractive indexes (RI).

Nondestructive analysis of silver in gold foil using synchrotron radiation X-ray fluorescence spectrometry.

Small particles of gold foil detached from an indoor decoration might be important evidence to associate a suspect with a crime scene. We have investigated the application of elemental analysis using synchrotron radiation X-ray fluorescence spectrometry to discriminate small particles of gold foil. Eight kinds of gold foil samples collected in Japan were used in the experiments. As a result of synchrotron radiation X-ray fluorescence spectrometry, only two elements, gold and silver, were detected from all gold foil samples. The intensity ratios of AgKalpha/AuLalpha showed good correlation with the content ratios of Ag/Au. The variation of intensity ratio within a same sample was sufficiently small compared with those of different samples. Therefore the comparison of this intensity ratio can be an effective method to discriminate small particles originating from different types of gold foil.

Forensic discrimination of sheet glass by a refractive-index measurement and elemental analysis with synchrotron radiation X-ray fluorescence spectrometry.

Measurements of the refractive index (RI) and elemental analysis using synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) were applied to the forensic discrimination of sheet-glass samples from different origins. The refractive index was calculated from the matching temperature at which the glass fragments became invisible in silicone oil. Fragments smaller than 1 mm in maximum diameter were taken from each of 11 sheet glasses and subjected to analysis by SR-XRF. The XRF spectrum of these samples indicated that a comparison of 6 elements (Ca, Fe, Sr, Zr, Ba and Ce) was useful for the discrimination of sheet glasses. Cluster analysis was performed using 33 sets of SR-XRF data obtained by triplicate measurements for the 11 glasses. Comparing 528 pairs among 33 samples, 515 pairs could be correctly discriminated. The number of indistinguishable pairs could be reduced from 36 to 4 by comparing the SR-XRF data. Elemental analysis by SR-XRF could provide small glass fragments with a more evidential value than the solely measurement of only RI, through a significant improvement of the discrimination capability.

Trace elemental analysis of titanium dioxide pigments and automotive white paint fragments for forensic examination using high-energy synchrotron radiation x-ray fluorescence spectrometry.

High-energy synchrotron radiation x-ray fluorescence spectrometry (SR-XRF) utilizing 116 keV x-rays was used to characterize titanium dioxide pigments (rutile) and automotive white paint fragments for forensic examination. The technique allowed analysis of K lines of 9 trace elements in 18 titanium dioxide pigments (rutile), and 10 trace elements in finish coat layers of seven automotive white paint fragments. High-field strength elements (HFSE) were found to strongly reflect the origin of the titanium dioxide (TiO(2)) pigments, and could be used as effective parameters for discrimination and classification of the pigments and paint fragments. A pairwise comparison of the finish coat layers of seven automotive white paint fragments was performed. The trace elements in the finish coat layers detected by the high-energy SR-XRF were especially effective for identification. By introducing the trace element information of primer and electrocoat layers, all the automotive white paint fragments could be discriminated by this technique.

Lower limits of detection of synchrotron radiation high-energy X-ray fluorescence spectrometry and its possibility for the forensic application for discrimination of glass fragments.

Synchrotron radiation high-energy X-ray fluorescence (SR-XRF) analysis utilizing 75.5keV X-ray radiation from beam-line BL37XU at Super Photon Ring 8GeV (SPring-8), a third-generation synchrotron facility, was found to have advantages for forensic discrimination of glass samples. The lower limits of detection (LLD) for calibration curves were at the picogram level for Ba, Ce, and Sm and at the 10pg level for Sr, Zr, Sn, and Hf. The spectrum of NIST SRM 612 glass reference material demonstrated K-line peaks of 31 elements including rare-earth elements, and the relative standard deviations (R.S.D.) of all the measured elements except Ca were less than 9.7%. Fragments of collected sheet glass were used as samples for investigating the application of this technique to forensic analysis. Several trace elements such as Pb, Rb, Sr, Zr, La, Ce, and Hf were detected in the spectra of the samples, and these elements could be used as indexes to characterize the glass samples. But the "lower limits of detection (LLD)" of each element were not examined enough. In this report, these limits by synchrotron radiation X-ray spectrometry were clarified. By these results, this technique should provide an effective approach to the nondestructive discrimination of small glass fragments in the field of forensic science.