Studies of Dopamine Oxidation Process by Atmospheric Pressure Glow Discharge Mass Spectrometry.

An atmospheric pressure glow discharge ionisation source was constructed and utilized to study the dopamine (DA) oxidation process coupling with mass spectrometry. During the DA oxidation process catalysed by polyphenol oxidase (PPO), six cationic intermediates were directly detected by the atmospheric pressure glow discharge mass spectrometry (APGD-MS). Combined with tandem mass spectrometry, the structures of the dopamine o-semiquinone radical (DASQ) and leukodopaminochrome radical (LDAC●) intermediates and structures of the isomers of dopaminochrome (DAC) and 5,6-dihydroxyindole (DHI) were further characterised with the introduction of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and deuterium oxide (D2O) to APGD-MS. Meanwhile, UV-Vis studies confirmed the important role of PPO in catalyzing the DA oxidation reaction. Based on APGD-MS studies, a possible mechanism could be proposed for DA oxidation catalysed by PPO. Furthermore, APGD-MS could provide possibilities for the effective detection and characterisation of short-lived intermediates, even in complicated systems.

Efficient identification of raw and ripe tung oil using headspace GC-MS.

To differentiate between the raw type and ripe type of tung oil, it is important to distinguish between the types of tung oil before its application. In the present work, an efficient headspace gas chromatography-mass spectrometry (HS-GC-MS) method was developed for identifying eight samples T1-T8, including the raw tung oil and ripe tung oil. The HS-GC-MS experiments results showed that octanoic acid existed only in ripe tung oil of T2, T4, T6, T8, not in raw tung oil of T1, T3, T5, T7. Combined with structural characterization by tandem mass spectrometry, octanoic acid was screened as an effective marker for distinguishing between raw tung oil and ripe tung oil. Then, the HS-GC-MS method was applied into the putty samples of X1 (raw tung oil with lime) and X2 (ripe tung oil with lime) and successfully identified the samples X1 mixed with raw tung oil and X2 mixed with ripe tung oil. The further validations results suggested that the detection limit of our HS-GC-MS method could reach 1.05 mg/L for octanoic acid, whereas the detection limit of derivative gas chromatography-mass spectrometry (DR-GC-MS) method was 2.74 mg/L for methyl octanoate. The investigation results can also provide the useful information and technical support for the selection of restoration materials and technology in ancient buildings.

Larmor Precession: Observation and Utilization for Boosting the Signal Intensity of Radio Frequency Glow Discharge Mass Spectrometry.

A novel magnet array system was constructed to use Larmor precession for boosting the signal intensity of rf-GD-MS. The enhancement mechanism with four magnet array devices of a single-block magnet and 2 × 2, 3 × 2, and 3 × 4 magnet arrays was simulated and studied by COMSOL Multiphysics Software 5.4.0 (COMSOL) to determine if the electrons in the discharge plasma could perform Larmor precession along the direction perpendicular to the magnetic field. Induced by Larmor precession, inelastic collisions between the primary electrons and the sample produced numerous secondary electrons and further improved the ionization efficiency. Moreover, the fuzzy synthetic evaluation result predicted that the device with a 3× 2 magnet array would display the greatest enhancement effect among the four devices. On the basis of these theoretical studies, a magnet array system with four magnet array devices was fabricated and utilized for studies of two scintillation crystals BGO and PWO. The observations indicated that the signal intensities obtained for 209Bi and 208Pb with the magnet array system were 630-3600 times of that obtained without a magnet and were enhanced by a factor of 1.5-2.8 compared with a previously reported stacked magnetic device. Two NIST samples were used to validate the method, and the results suggested that relative errors were less than 10%, and the lowest detection limit for the 3 × 2 magnet array could reach 0.0032 µg·g-1. Furthermore, the magnet array enhancement system with Larmor precession offers an efficient and sensitive approach for direct analysis of nonconducting materials.

Signal Enhancement with Stacked Magnets for High-Resolution Radio Frequency Glow Discharge Mass Spectrometry.

A method for signal enhancement utilizing stacked magnets was introduced into high-resolution radio frequency glow discharge-mass spectrometry (rf-GD-MS) for significantly improved analysis of inorganic materials. Compared to the block magnet, the stacked magnets method was able to achieve 50-59% signal enhancement for typical elements in Y2O3, BSO, and BTN samples. The results indicated that signal was enhanced as the increase of discharge pressure from 1.3 to 8.0 mPa, the increase of rf-power from 10 to 50 W with a frequency of 13.56 MHz, the decrease of sample thickness, and the increase of number of stacked magnets. The possible mechanism for the signal enhancement was further probed using the software "Mechanical APDL (ANSYS) 14.0". It was found that the distinct oscillated magnetic field distribution from the stacked magnets was responsible for signal enhancement, which could extend the movement trajectories of electrons and increase the collisions between the electrons and neutral particles to increase the ionization efficiency. Two NIST samples were used for the validation of the method, and the results suggested that relative errors were within 13% and detection limit for six transverse stacked magnets could reach as low as 0.0082 µg g-1. Additionally, the stability of the method was also studied. RSD within 15% of the elements in three nonconducting samples could be obtained during the sputtering process. Together, the results showed that the signal enhancement method with stacked magnets could offer great promises in providing a sensitive, stable, and facile solution for analyzing the nonconducting materials.

Suppressing the dissolution of polysulfides with cosolvent fluorinated diether towards high-performance lithium sulfur batteries.

The dissolution and shuttle of polysulfides in electrolytes cause severe anode corrosion, low coulombic efficiency, and a rapid fading of the capacity of lithium-sulfur batteries. Fluorinated diether (FDE) was selected as a cosolvent in traditional ether electrolytes to suppress the dissolution of polysulfides. The modified electrolytes lead to a negligible solubility of polysulfides, as well as decreased corrosion of the lithium anode. In an optimal system, the cells show improved cycling performance with an average coulombic efficiency of above 99% and a highly stable reversible discharge capacity of 701 mA h g-1 after 200 cycles at a 0.5C rate. A combination of electrochemical studies and X-ray photoelectron spectroscopy demonstrates the sulfur reduction mechanism with three voltage plateaus.

[Review on Analytical Methods of Doping Elements in Synthetic Crystals].

During the synthesis of crystal material, specific dopant can enhance the qualities and performance of crystals, while the types, concentrations and distributions of doping elements also have significant influence on the structures and properties of artificial crystals. Hence, it is very important to determine the concentrations of doping elements for further improving the crystal material formulas, crystal growth process, andits quality control. Currently, the analysis techniques for doping elements' characterization include atomic spectrometry, X-ray fluorescence spectrometry, inorganic mass spectrometry, electron probe microanalysis, etc. The principles, advantages and disadvantages of these techniques are discussed in this paper. Considering the specialties and scope of application, it is necessary to choose the suitable methods to improve the efficiency and accuracy. Meanwhile, the developing trends of analysis methods for doping elements are also prospected.

Confocal micro-X-ray fluorescence analysis for difference identification of ceramic samples.

A nondestructive analytical method for difference identification is required in the research fields such as forensic science or archeology. An X-ray fluorescence (XRF) analysis is one of feasible techniques for this purpose. Micro-XRF using an X-ray micro-beam gives elemental distributions by scanning the samples. A confocal micro-XRF (CM-XRF) technique is a unique analytical technique to analyze limited volume. CM-XRF enables elemental depth imaging and elemental profiling in depth nondestructively. Therefore, CM-XRF has been applied for various samples such as industrial samples, paintings, forensic samples, food materials, and human hairs. CM-XRF technique would be a suitable method for difference identification because the CM-XRF gives detailed information on elemental distribution not only on the surface of the sample but also in depth. We developed CM-XRF instrument in the laboratory and applied to two very similar ceramics samples. It showed differences in the intensity profiles of Fe and Mn for blue paintings on the ceramics. In addition, depth elemental analysis revealed different depth profiles especially of Co and Zn for both samples. These results suggest that CM-XRF provides useful information for the identification of ceramic samples.

Highly Sensitive Room-Temperature Detection of Ammonia in the Breath of Kidney Disease Patients Using Fe2Mo3O8/MoO2@MoS2 Nanocomposite Gas Sensor.

A novel Fe2Mo3O8/MoO2@MoS2 nanocomposite is synthesized for extremely sensitive detection of NH3 in the breath of kidney disease patients at room temperature. Compared to MoS2, α-Fe2O3/MoS2, and MoO2@MoS2, it shows the optimal gas-sensing performance by optimizing the formation of Fe2Mo3O8 at 900 °C. The annealed Fe2Mo3O8/MoO2@MoS2 nanocomposite (Fe2Mo3O8/MoO2@MoS2-900 °C) sensor demonstrates a remarkably high selectivity of NH3 with a response of 875% to 30 ppm NH3 and an ultralow detection limit of 3.7 ppb. This sensor demonstrates excellent linearity, repeatability, and long-term stability. Furthermore, it effectively differentiates between patients at varying stages of kidney disease through quantitative NH3 measurements. The sensing mechanism is elucidated through the analysis of alterations in X-ray photoelectron spectroscopy (XPS) signals, which is supported by density functional theory (DFT) calculations illustrating the NH3 adsorption and oxidation pathways and their effects on charge transfer, resulting in the conductivity change as the sensing signal. The excellent performance is mainly attributed to the heterojunction among MoS2, MoO2, and Fe2Mo3O8 and the exceptional adsorption and catalytic activity of Fe2Mo3O8/MoO2@MoS2-900 °C for NH3. This research presents a promising new material optimized for detecting NH3 in exhaled breath and a new strategy for the early diagnosis and management of kidney disease.

[Quantitative surface analysis of Pt-Co, Cu-Au and Cu-Ag alloy films by XPS and AES].

In order to improve the quantitative analysis accuracy of AES, We associated XPS with AES and studied the method to reduce the error of AES quantitative analysis, selected Pt-Co, Cu-Au and Cu-Ag binary alloy thin-films as the samples, used XPS to correct AES quantitative analysis results by changing the auger sensitivity factors to make their quantitative analysis results more similar. Then we verified the accuracy of the quantitative analysis of AES when using the revised sensitivity factors by other samples with different composition ratio, and the results showed that the corrected relative sensitivity factors can reduce the error in quantitative analysis of AES to less than 10%. Peak defining is difficult in the form of the integral spectrum of AES analysis since choosing the starting point and ending point when determining the characteristic auger peak intensity area with great uncertainty, and to make analysis easier, we also processed data in the form of the differential spectrum, made quantitative analysis on the basis of peak to peak height instead of peak area, corrected the relative sensitivity factors, and verified the accuracy of quantitative analysis by the other samples with different composition ratio. The result showed that the analytical error in quantitative analysis of AES reduced to less than 9%. It showed that the accuracy of AES quantitative analysis can be highly improved by the way of associating XPS with AES to correct the auger sensitivity factors since the matrix effects are taken into account. Good consistency was presented, proving the feasibility of this method.

Growth of highly oriented hydroxyapatite arrays tuned by quercetin.

Crystal calls: the remarkable crystal modulation ability of quercetin (QUE) in highly oriented hydroxyapatite (HAp) array crystallization is reported. Organized HAp crystals were obtained by hydrothermal exchange of α-tricalcium phosphate (α-TCP) precursor in solution with a progressive increase in QUE concentration. Experimental results revealed that QUE would be a potentially effective crystal modulation assistant.

[Analytical figures of merit of Hildebrand grid and ultrasonic nebulizations in inductively coupled plasma atomic emission].

Hildebrand grid nebulizer is a kind of improved Babington nebulizer, which can nebulize solutions with high total dissolved solids. And the ultrasonic nebulizer (USN) possesses advantage of high nebulization efficiency and fine droplets. In the present paper, the detection limits, matrix effects, ICP robustness and memory effects of Hildebrand grid and ultrasonic nebulizers for ICP-AES were studied. The results show that the detection limits using USN are improved by a factor of 6-23 in comparison to Hildebrand grid nebulizer for Cu, Pb, Zn, Cr, Cd and Ni. With the USN the matrix effects were heavier, and the degree of intensity enhancement and lowering depends on the element line, the composition and concentrations of matrices. Moreover, matrix effects induced by Ca and Mg are more significant than those caused by Na and Mg, and intensities of ionic lines are affected more easily than those of atomic lines. At the same time, with the USN ICP has less robustness. In addition, memory effect of the USN is also heavier than that of Hildebrand grid nebulizer.

CTAB Enhanced Room-Temperature Detection of NO2 Based on MoS2-Reduced Graphene Oxide Nanohybrid.

A new NO2 nanohybrid of a gas sensor (CTAB-MoS2/rGO) was constructed for sensitive room-temperature detection of NO2 by 3D molybdenum disulfide (MoS2) and reduced graphene oxide (rGO), assisted with hexadecyl trimethyl ammonium bromide (CTAB). In comparison with MoS2 and MoS2/rGO, the BET and SEM characterization results depicted the three-dimensional structure of the CTAB-MoS2/rGO nanohybrid, which possessed a larger specific surface area to provide more active reaction sites to boost its gas-sensing performance. Observations of the gas-sensing properties indicated that the CTAB-MoS2/rGO sensor performed a high response of 45.5% for 17.5 ppm NO2, a remarkable selectivity of NO2, an ultra-low detection limit of 26.55 ppb and long-term stability for a 30-day measurement. In addition, the response obtained for the CTAB-MoS2/rGO sensor was about two to four times that obtained for the MoS2/rGO sensor and the MoS2 sensor toward 8 ppm NO2, which correlated with the heterojunction between MoS2 and rGO, and the improvement in surface area and conductivity correlated with the introduction of CTAB and rGO. The excellent performance of the CTAB-MoS2/rGO sensor further suggested the advantage of CTAB in assisting a reliable detection of trace NO2 and an alternative method for highly efficiently detecting NO2 in the environment.

[Mineralogical effect correction for pressed iron ore samples in wavelength dispersive X-ray fluorescence analysis].

The possibility of correcting mineralogical effect for pressed powder pellets of iron ore samples was studied in wavelength dispersive X-ray fluorescence analysis of major and minor elements with 10 Chinese iron ore CRMs. Two methods were applied to reduce the influence of mineralogical effect. The first one is to check 20 angles for every sample before measurement to correct peak shift; another method is replacing peak intensity with peak area of the analytical line to correct the shape distortion of the spectrum. The K factors of the two methods for each element were compared to those from regular measurements. The results show that the calibration for most of the elements was improved, although to different degrees. The improvement in the calibration for sulfur is evident. The calibration for other elements can meet the general requirements except for total iron.

3D-printed scaffolds with bioactive elements-induced photothermal effect for bone tumor therapy.

For treatment of bone tumor and regeneration of bone defects, the biomaterials should possess the ability to kill tumor cells and regenerate bone defect simultaneously. To date, there are a few biomaterials possessing such dual functions, the disadvantages, however, such as long-term toxicity and degradation, restrict their application. Although bioactive elements have been incorporated into biomaterials to improve their osteogenic activity, there is no report about elements-induced functional scaffolds for photothermal tumor therapy. Herein, the elements (Cu, Fe, Mn, Co)-doped bioactive glass-ceramic (BGC) scaffolds with photothermal effect and osteogenic differentiation ability were prepared via 3D-printing method. Moreover, the photothermal anti-tumor effect and osteogenic activity of these scaffolds were systematically investigated. The prepared elements-doped scaffolds possessed excellent photothermal performance, which displayed a trend, 5Cu-BGC > 5Fe-BGC > 5Mn-BGC > 5Co-BGC, in this study. The final temperature of elements-doped scaffolds can be well controlled by altering the doping element categories, contents and laser power density. Additionally, the hyperthermia induced by 5Cu-BGC, 5Fe-BGC and 5Mn-BGC effectively killed tumor cells in vitro and inhibited tumor growth in vivo. More importantly, 5Fe-BGC and 5Mn-BGC scaffolds could promote rabbit bone mesenchymal stem cells (rBMSCs) adhesion, and the ionic products released from elements-doped scaffolds significantly stimulated the osteogenic differentiation of bone-forming cells. These results suggested that 5Fe-BGC and 5Mn-BGC scaffolds possessed promising potential for photothermal treatment of bone tumor and at the same time for stimulating bone regeneration, representing a smart strategy for the treatment of bone tumors by combining dual functional bioactive ions with tissue engineering scaffolds. STATEMENT OF SIGNIFICANCE: The major innovation of this study is that we fabricated the elements (Cu, Fe, Mn, Co)-doped bioactive scaffolds via 3D printing technique and found that they possess distinct photothermal performance and osteogenic differentiation ability. To the best of our knowledge, there is no report about elements-doped scaffolds for photothermal therapy of bone tumor. This is an important research advance by combining the photothermal effect and osteogenic differentiation activity of bioactive elements in the scaffold system for potential bone tumor therapy and bone reconstruction. We optimized the elements-doped scaffolds and found the photothermal effect of elements-doped scaffolds (5Cu-BGC, 5Fe-BGC, 5Mn-BGC) could effectively kill tumor cells in vivo. The photothermal performance of elements-doped scaffolds follows a trend: 5Cu-BGC > 5Fe-BGC > 5Mn-BGC > 5Co-BGC > BGC. Compared to traditional nano-sized photothermal agents, bioactive elements-induced functional scaffolds have better biosecurity and bioactivity. Furthermore, 5Fe-BGC and 5Mn-BGC scaffolds displayed excellent bone-forming activity by stimulating the osteogenic differentiation of bone-forming cells. The major significance of the study is that the elements-doped bioactive glass-ceramics (5Fe-BGC, 5Mn-BGC) have great potential to be used as bifunctional scaffolds for photothermal tumor therapy and bone regeneration, representing a smart strategy for the treatment of bone tumors by combining dual functional bioactive ions with tissue engineering scaffolds.

[Calculation of the contributions of scattering effects to the X-ray fluorescence intensities].

The contribution of scattering effects to the X-ray fluorescence intensity was studied for pure element samples, BaB binary samples and fused disk samples by theoretic calculation and experiment. Three scattering effects were considered in the present study, i. e. coherent scattering effect, incoherent scattering effect, and primary fluorescence that was scattered into the direction of detector. The study shows that the contribution of scattering effects to the intensity of fluorescence is related to the energy of the atomic absorption edge, and the sample's matrix. The higher the energy of the atomic absorption edge, the more the contribution of scattering effects to the intensity of fluorescence. The contribution of scattering effects to the fluorescence intensity is larger for light matrix samples than heavy matrix samples. The results of experiment show that the accuracy of theoretic calculation was evidently improved when the scattering effects were considered in the theoretic calculation for the intensity of fluorescence.

[Study on the influence of excitation voltage and anode on the contribution of scattering effects to the intensity of X-ray fluorescence].

The influence of X-ray tube spectral distribution related to the X-ray tube voltage and target anode on the contribution of scattering effects to the intensity of fluorescence was studied by using some fused disk samples. Three scattering effects were considered. They are coherent scattering effect, incoherent scattering effect and primary fluorescence scattered into the direction of detector respectively. For the fused beads under investigation, the results show that the contributions of coherent scattering effect and the primary fluorescence scattered into the direction of detector decreased with increasing the tube voltage, and the contribution was larger when excited by the X-ray from Cr target than that from Rh target. On the contrary, the contribution of incoherent scattering effect to the intensity of fluorescence increased with increasing the voltage, and was larger when excited by the X-ray from Rh target than that from Cr target. The sum of the contribution of scattering effects to the intensity of fluorescence increased with increasing the voltage, and was larger when excited by the X-ray from Rh target than that from Cr target.

The Formation of Defect-Pairs for Highly Efficient Visible-Light Catalysts.

Highly efficient visible-light catalysts are achieved through forming defect-pairs in TiO2 nanocrystals. This study therefore proposes that fine-tuning the chemical scheme consisting of charge-compensated defect-pairs in balanced concentrations is a key missing step for realizing outstanding photocatalytic performance. This research benefits photocatalytic applications and also provides new insight into the significance of defect chemistry for functionalizing materials.

[Analysis of films by X-ray fluorescence spectrometry].

As a quantitative method of film sample, the X-ray fluorescence (XRF) technique has been used extensively because it is non-destructive, fast and accurate. Moreover it could determine the concentration and thickness of film sample simultaneously. A review was given of the study on the quantitative method of films by X-ray fluorescence spectrometry, in which the theoretical calculation of fluorescence intensity, the matrix effects and the methods for their correction, the sources of errors, the software for quantitative analysis, and the application of the method were summarized and discussed. New development and application of films characterization by X-ray fluorescence spectrometry were also expected. Because the similar calibration specimen for film sample is difficult to prepare and the fundamental parameter method could quantitatively analyze film samples even if only the pure element specimen is employed, the fundamental parameter method is studied extensively. The fundamental parameter method was introduced mainly in the present article, including the fundamental parameter equations to calculate the theoretical intensity of fluorescence, the source of error in calculation, and the software for analysis.

[Study of enhancement effects in X-ray fluorescence analysis for multi-layer samples].

The enhancement effects in X-ray fluorescence analysis for multi-layer samples were studied. A computer program was developed based on the theoretical equations for X-ray fluorescence intensity calculation and used to calculate the intensities of primary fluorescence and secondary fluorescence, the ratios of intensities of secondary fluorescence to primary fluorescence, and the portions of intensities of secondary fluorescence in total fluorescence for Fe Kalpha line in Zn/Fe and Fe/Zn film samples. It was found that the intensities of a characteristic line of an element in primary fluorescence and secondary fluorescence, the ratios of intensities of secondary fluorescence to primary fluorescence, and the portions of intensities of secondary fluorescence in total fluorescence were dependent not only on the thickness of the films but also on the position of the films in case of constant excitation conditions when multi-layer samples were tested by X-ray fluorescence analysis. When the thickness of Zn layer is the same as that of Fe layer, the calculated ratio of intensity of secondary fluorescence to total fluorescence of Fe Kalpha varies with the thickness, and reaches up to 9% for Fe/Zn sample while up to 35% for Zn/Fe sample.

Carbon Disulfide Cosolvent Electrolytes for High-Performance Lithium Sulfur Batteries.

Development of lithium sulfur (Li-S) batteries with high Coulombic efficiency and long cycle stability remains challenging due to the dissolution and shuttle of polysulfides in electrolyte. Here, a novel additive, carbon disulfide (CS2), to the organic electrolyte is reported to improve the cycling performance of Li-S batteries. The cells with the CS2-additive electrolyte exhibit high Coulombic efficiency and long cycle stability, showing average Coulombic efficiency >99% and a capacity retention of 88% over the entire 300 cycles. The function of the CS2 additive is 2-fold: (1) it inhibits the migration of long-chain polysulfides to the anode by forming complexes with polysulfides and (2) it passivates electrode surfaces by inducing the protective coatings on both the anode and the cathode.