Breakthrough of 2- to 3-μm scale U–Pb zircon dating using Cameca IMS-1280HR SIMS

A zircon U–Pb dating method with a high spatial resolution of 2- to 3-μm was successfully implemented by using Cameca IMS-1280HR SIMS in this study. Homemade cathode and modified intermediate pole were used to improve the intrinsic performance of duoplasmatron ion source. An O⁻ primary beam with intensity of approximately 3 μA and stability of 0.68% over 40 minutes was achieved and could be used continuously for more than 240 hours under high current conditions. Under Gaussian illumination mode, a 2- to 3-μm O⁻ primary beam was obtained with an intensity of approximately 200 pA. Four standard zircons, namely, 91500, Temora, Plešovice, and Qinghu, were dated using the 2- to 3-μm high spatial resolution U–Pb isotopic analysis, yielding U–Pb ages consistent with their recommended values, within errors. Our work shows that zircon U–Pb dating with high accuracy and spatial resolution can be achieved, on the basis of a series of duoplasmatron modification and instrumental optimization.     

Measurement of the polarization of thermal muonium in vacuum

We report the first measurement of the polarization of thermal muonium in vacuum. A 20 MeV/c beam of μ⁺ was stopped in a layer of SiO₂ powder which emitted (17±1)% of the stopped μ⁺ into vacuum as thermal muonium. The muonium Larmor precession was observed in a transverse magnetic field of 1.4 G, and the measured amplitude of the precession signal indicates that the μ⁺ polarization in the muonium is (39±9)%.     

Ultrahigh sensitivity SIMS analysis of oxygen in silicon

We report on the detection of very low oxygen concentration in silicon by a secondary‐ion mass spectrometry (SIMS) method. Using a magnetic IMS 6F Cameca SIMS spectrometer and applying a very high primary Cs⁺ ion flux, prolonged presputtering, extensive vacuum chamber baking, titanium sublimation pump, and an LN trap, we have reached a detection limit of ~2 × 10¹⁵ O atoms/cm³ in chemical vapor deposition epitaxial Si films. This value appears to be at least 10 times lower than in any published or unpublished source known to the authors, including the reference sensitivities listed by the instrument manufacturer. Most likely, the key improvement that has allowed us to drive the detection limit to 10¹⁵ at/cm³ is the use of an ion pump in the analysis chamber. The working pressure in our analysis chamber is ~10⁻¹⁰ Thorr, ie, 1 decade lower than that the commercially equipped with a turbo pump. This paper demonstrates optimized analytical conditions for the oxygen measurements in Si, as a function of depth: (i) Very shallow profiles are practically impossible to measure accurately because of native oxide at the surface. (ii) Shallow‐to‐medium range profiles, up to ~20 μm, are the most amenable to SIMS measurements. (iii) Medium‐to‐deep (~20‐50 μm) range is required to follow interdiffusion and segregation in epitaxial layers when the oxygen‐free layer is grown on a CZ Si substrate. (iv) Extremely deep profiles, up to full thickness of the wafer, definitely necessitate beveling.     

Properties of arylpolyesters with reference to water content

The 4000–2000 cm⁻¹ infrared spectral region from transmission FTIR spectra of films (≈ 220 μm thick) of amorphous poly (ethylene terephthalate) (PET) and poly(ethylene 2, 6-naphthalenedicarboxylate) (PEN) was analyzed. In addition to the strong bands for the stretching vibration modes of H-C bonds, the ester-overtone band at about 3430 cm⁻¹ and a doublet (3630, 3550 cm⁻¹) band, related to absorbed water, appear. The spectra for these materials show significant differences in absorptivity and frequency for the ester overtone band. Real time water sorption/desorption in these films was investigated simultaneously by FTIR spectroscopy and by measurement of weight changes. A linear correlation between the integrated absorbance of the water bands and the relative weight variation of the films was found for these two polymers. Results show that the infrared absorptivity of these bands is identical in both materials and that water molecules are weakly bound to ester groups throughout the films. However, it turns out that the water content is higher in the case of PEN which has a larger specific volume.     

Ionization-induced nucleation above liquid beam of aqueous solution of phenol after IR laser irradiation

A continuous liquid flow of an aqueous solution of phenol (Ph) in a vacuum (a liquid beam) was irradiated with a pulsed IR laser at 3 μm, which was resonant to the OH-stretching vibration of the solvent water molecules. Phenol molecules ejected from the liquid beam were selectively ionized at about 0.5 mm above it by a pulsed UV laser (270–280 nm). The photoions thus produced were extracted in a pulsed electric field with a given residence time after the photoionization for mass analysis. It was shown that photoions, Ph⁺, were solvated into Ph⁺(H₂O)_n in a dense cloud of water vapor ejected from the liquid beam by IR irradiation.     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

Strong-Base-Assisted Synthesis of a Crystalline Covalent Triazine Framework with High Hydrophilicity via Benzylamine Monomer for Photocatalytic Water Splitting

Methods to synthesize crystalline covalent triazine frameworks (CTFs) are limited and little attention has been paid to development of hydrophilic CTFs and photocatalytic overall water splitting. A route to synthesize crystalline and hydrophilic CTF-HUST-A1 with a benzylamine-functionalized monomer is presented. The base reagent used plays an important role in the enhancement of crystallinity and hydrophilicity. CTF-HUST-A1 exhibits good crystallinity, excellent hydrophilicity, and excellent photocatalytic activity in sacrificial photocatalytic hydrogen evolution (hydrogen evolution rate up to 9200 μmol g⁻¹ h⁻¹). Photocatalytic overall water splitting is achieved by depositing dual co-catalysts in CTF-HUST-A1, with H₂ evolution and O₂ evolution rates of 25.4 μmol g⁻¹ h⁻¹ and 12.9 μmol g⁻¹ h⁻¹ in pure water without using sacrificial agent.     

Transparent Nonlinear Optical Polymers for All‐Optical Wavelength Converters in Optical Fiber Communications

After synthesizing two chromophores with imine, we prepared acrylic nonlinear optical (NLO) polymers that contained the chromophores for all‐optical wavelength converters in optical fiber communication. The polymers show high d₃₃, 35 pm · V⁻¹, at 1.55 μm (pumping beam), considering their low losses, −3.0 dB · cm⁻¹, at a wavelength of 0.785 μm (near second harmonic signal beam of the pumping beam). This result means that the polymers are good candidates for wavelength converters of an approximately 1.55 μm signal beam.

UV‐vis spectra of NLO chromophores and polymers.     

Repair of defects created by Ar+ sputtering on graphite surface by annealing as confirmed using ToF‐SIMS and XPS

Defects were created on the surface of highly oriented pyrolytic graphite (HOPG) by sputtering with an Ar⁺ ion beam, then characterized using X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) at 500°C. In the XPS C1s spectrum of the sputtered HOPG, a sp³ carbon peak appeared at 285.3 eV, representing surface defects. In addition, 2 sets of peaks, the C_x⁻ and C_xH⁻ ion series (where x = 1, 2, 3...), were identified in the ToF‐SIMS negative ion spectrum. In the positive ion spectrum, a series of C_xH₂^+• ions indicating defects was observed. Annealing of the sputtered samples under Ar was conducted at different temperatures. The XPS and ToF‐SIMS spectra of the sputtered HOPG after 800°C annealing were observed to be similar to the spectra of the fresh HOPG. The sp³ carbon peak had disappeared from the C1s spectrum, and the normalized intensities of the C_xH⁻ and C_xH₂^+• ions had decreased. These results indicate that defects created by sputtering on the surface of HOPG can be repaired by high‐temperature annealing.     

Isotopic fractionation during secondary ionisation mass spectrometry: Crystallographic orientation effects in magnetite

Isotopic and elemental fractionation occurs as an inevitable and often frustrating factor in SIMS although the potential and demonstrated capabilities of ion probes make the solution of such problems well worth attaining. This paper describes a source of isotopic fractionation which may arise from the crystallographic structure of the sample. This effect, observed in magnetite, is potentially a source of error in acquiring reproducible isotopic ratios during SIMS of magnetite although no similar effect has been observed during several years of measurements on quartz, olivine or carbonates. The measurements were acquired using an Isolab 54 ion probe by rotating the sample about an axis normal to the surface and measuring ¹⁸O/¹⁶O ratios as a function of angle. The primary ion beam impacts the sample at an angle of 45° so that rotation of the sample should bring lattice planes approximately into and out of coincidence with the primary beam. Repeated ¹⁸O/¹⁶O measurements from magnetite crystals as a function of orientation show maxima in measured ¹⁸O/¹⁶O values which can be correlated with channelling along lattice planes. The measured ratio has been observed to increase by approximately 7‰ as a function of angle, variations which are very significant compared with isotopic fractionations produced by geological processes. The maxima correlate well with the [1 1 0], [1 0 1] and [0 1 1] lattice vectors of magnetite and are interpreted as channelling of the primary ions along the lattice vectors. Since it is extremely difficult, if not impossible, to determine the crystallographic orientation of magnetite in thin section, we believe that it is therefore necessary to measure magnetite samples in at least two orientations (separated by an angle that is not equal to the difference between two channelling orientations) against a standard in a known orientation.     

Determination of coenzyme Q10 by in situ EPR spectroelectrochemistry

A rapid and sensitive method is developed for the determination of coenzyme Q₁₀ (CoQ₁₀) on the basis of the measurement of the radical intermediate (ubisemiquinone) formed during the reduction reaction of CoQ₁₀ at a silver electrode by in situ EPR spectroelectrochemical techniques. At the potential of −0.55 V (versus SCE), the ubisemiquinone is formed and is stable in ethanol+water. Under optimal conditions, it was found that the proposed method provided a linear response over the CoQ₁₀ concentration range 5–100 μmol l⁻¹ with a detection limit of 3 μmol l⁻¹. The relative standard deviation of the results was 7.5% for six successive determinations at 10 μmol l⁻¹ CoQ₁₀. This method is a useful tool for improving the selectivity when other chemicals present in the sample do not interfere in the assay.     

Measurements of rubidium in standard reference samples by wavelength-modulation diode laser absorption spectrometry in a graphite furnace

An investigation of the capabilities of the WM-LDAS-GF (wavelength-modulation laser diode absorption spectrometry in graphite furnaces) technique for detection of Rb at low pg ml⁻¹ concentrations in samples with complex matrices has been performed. Five reference materials were investigated with respect to their Rb content by the WM-LDAS-GF technique: corn bran (NIST 8433); NIST water; (1643d) riverine water (SLRS-2); estuarine water (SLEW-1); and sea water (NASS-3). Freeze-dried corn bran was found to have a Rb concentration of 440 ± 70 ng g⁻¹. This compares well with the certified concentration of 500 ± 300 ng g⁻¹. The Rb content of the NIST water was assessed to 12.7 ± 1.7 ng ml⁻¹. This compares excellently with the specified (although not certified) level of 13 ng ml⁻¹. None of the three other reference materials has any certified Rb level. The Rb content of riverine water was found to be 3.4 ± 0.8 ng ml⁻¹. Chemical interferences were encountered when estuarine water and sea water were analyzed (loss of Rb as RbCl). Addition of NH₄NO₃ as the matrix modifier increased the Rb recovery values considerably (although not fully to unity). Estuarine water and sea water were found to have Rb contents of 30 ± 10 ng ml⁻¹ and 140 ± 50 ng ml⁻¹, respectively. A detection limit for Rb in deionized water of 10 fg (corresponding to a concentration of 1 pg ml⁻¹ using a 10 μL aliquot) was obtained. This is identical to (and thus verifies) the previously published result by the group of K. Niemax. These results show that the WM-LDAS-GF technique is capable of detecting traces of Rb in samples also with complex matrices.     

PoPD Modified ITO Based Capacitive Immunosensor for Sulphathiazole

A capacitive immunosensor for determination of sulphathaizole (STZ) has been developed on polymer coated indium tin oxide glass chip (ITO). The immunosensor chip was fabricated by polymerizing, ortho‐ phenylenediamine (o PD) on ITO followed by surface modification with anti‐sulphathiazole antibody. The developed immunosensor chip was characterized by using Atomic force microscopy (AFM), Cyclicvoltammetry (CV) and Electrochemical impedance spectroscopy (EIS). The capacitive measurement of the developed immunosensor was performed by using EIS in spiked drinking water and milk. The developed sensor showed liner detection range 0.1‐100 μgL⁻¹for STZ with a limit of detection 0.01 μgL⁻¹ in water with recovery between 95–106 %. The biosensor showed excellent selectivity and storage stability upto 4 weeks when preserved at 4 °C.     

Sensitive Electrochemical Determination of Trifluralin at a Disposable Pencil Graphite Electrode

A sensitive differential pulse (DP) voltammetric method has been proposed for the determination of trifluralin (TFA) based on both its reduction and oxidation at a disposable pencil graphite electrode (PGE). DP voltammograms recorded under optimized conditions show that oxidation and reduction peak currents increased linearly in the range from 1.0 to 75.0 μM and from 0.50 to 100.0 μM TFA, respectively. LOD and sensitivity values have been determined as 0.39 μM and 11170 μA mM⁻¹ cm⁻² for oxidation and as 0.20 μM and 22167 μA mM⁻¹ cm⁻² for reduction. The acceptable recovery values (95.2–104.8 %) were obtained from real water samples.     

Efficient Conversion of Biomass to Formic Acid Coupled with Low Energy Consumption Hydrogen Production from Water Electrolysis

The development of a new electrolytic water hydrogen production coupling system is the key to realize efficient and low-cost hydrogen production and promote its practical application. Herein, a green and efficient electrocatalytic biomass to formic acid (FA) coupled hydrogen production system has been developed. In such a system, carbohydrates such as glucose are oxidized to FA using polyoxometalates (POMs) as the redox anolyte, while H₂ is evolved continuously at the cathode. Among them, the yield of glucose to FA is as high as 62.5 %, and FA is the only liquid product. Furthermore, the system requires only 1.22 V to drive a current density of 50 mA cm⁻², and the Faraday efficiency of hydrogen production is close to 100 %. Its electrical consumption is only 2.9 kWh Nm⁻³ (H₂), which is only 69 % of that of traditional electrolytic water. This work opens up a promising direction for low-cost hydrogen production coupled with efficient biomass conversion.     

Dissipation of chlortetracycline in the aquatic environment: Characterization in terms of a generalized multiphase pseudo–zero-order rate law

The kinetics of the dissipation of chlortetracycline in the aquatic environment was studied over a period of 90 days using microcosm experiments and distilled water controls. The distilled water control experiments, carried out under dark conditions as well as exposed to natural sunlight, exhibited biphasic linear rates of dissipation. The microcosm experiments exhibited triphasic linear rates of degradation both in the water phase (2.7 × 10⁻², 7 × 10⁻³, 1.3 × 10⁻³ μg g⁻¹ day^–1) and the sediment phase (3.4 × 10⁻², 6 × 10⁻³, 1 × 10⁻³ μg g⁻¹ day^–1). The initial slow rate of dissipation in the dark control (3 × 10⁻³ μg g⁻¹ day^–1) was attributed to a combination of evaporation and hydrolysis, whereas the subsequent fast rate (1.8 × 10⁻³ μg g⁻¹ day^–1) was attributed to a combination of evaporation, hydrolysis, and microbial degradation. For the sunlight-exposed control, the initial slow rate of dissipation (1.5 × 10⁻³ μg g⁻¹ day^–1) was attributed to a combination of evaporation, hydrolysis, and photolysis, whereas the subsequent fast rate was attributed to a combination of evaporation, hydrolysis, photolysis, and microbial degradation (5.1 × 10⁻³ μg g⁻¹ day^–1). The initial fast rate of dissipation in the water phase of the microcosm experiment is attributed to a combination of evaporation, hydrolysis, photolysis, and microbial degradation, whereas all subsequent slow rates in the water phase and all rates of degradation in the sediment phase are attributed to microbial degradation of the colloidal and sediment particle adsorbed antibiotic. A multiphase zero-order kinetic model is presented that takes into account (a) dissipation of the antibiotic via evaporation, hydrolysis, photolysis, microbial degradation, and adsorption by colloidal and sediment particles and (b) the dependence of the dissipation rate on the concentration of the antibiotic, type and count of microorganisms, and type and concentration of colloidal particles and sediment particle adsorption sites within a given aquatic environment.     

Simultaneous determination of cadmium and lead in wine by electrothermal atomic absorption spectrometry

A method has been developed for the direct simultaneous determination of Cd and Pb in white and red wine by electrothermal atomic absorption spectrometry (ET-AAS) using a transversely heated graphite tube atomizer (THGA) with longitudinal Zeeman-effect background correction. The thermal behavior of both analytes during pyrolysis and atomization stages were investigated in 0.028 mol l⁻¹ HNO₃ and in 1+1 v/v diluted wine using mixtures of Pd(NO₃)₂+Mg(NO₃)₂ and NH₄H₂PO₄+Mg(NO₃)₂ as chemical modifiers. With 5 μg Pd+3 μg Mg as the modifiers and a two-step pyrolysis (10 s at 400°C and 10 s at 600°C), the formation of carbonaceous residues inside the atomizer was avoided. For 20 μl of sample (wine+0.056 mol l⁻¹ HNO₃, 1+1, v/v) dispensed into the graphite tube, analytical curves in the 0.10–1.0 μg l⁻¹ Cd and 5.0–50 μg l⁻¹ Pb ranges were established. The characteristic mass was approximately 0.6 pg for Cd and 33 pg for Pb, and the lifetime of the tube was approximately 400 firings. The limits of detection (LOD) based on integrated absorbance (0.03 μg l⁻¹ for Cd, 0.8 μg l⁻¹ for Pb) exceeded the requirements of Brazilian Food Regulations (decree #55871 from Health Department), which establish the maximum permissible level for Cd at 200 μg l⁻¹ and for Pb at 500 μg l⁻¹. The relative standard deviations (n=12) were typically <8% for Cd and <6% for Pb. The recoveries of Cd and Pb added to wine samples varied from 88 to 107% and 93 to 103%, respectively. The accuracy of the direct determination of Cd and Pb was checked for 10 table wines by comparing the results with those obtained for digested wine using single-element ET-AAS, which were in agreement at the 95% confidence level.     

Constant Electricity Generation in Nanostructured Silicon by Evaporation-Driven Water Flow

Recently, hydrovoltaic technology emerged as a novel renewable energy harvesting method, which dramatically extends the capability to harvest water energy. However, the urgent issue restricting its device performance is poor carrier transport properties of the solid surface if large charged interface is considered simultaneously. Herein, a hydrovoltaic device based on silicon nanowire arrays (SiNWs), which provide large charged surface/volume ratio and excellent carrier transport properties, yields sustained electricity by a carrier concentration gradient induced by evaporation-induced water flow inside nanochannels. The device can yield direct current with a short-circuit current density of over 55 μA cm⁻², which is three orders larger than a previously reported analogous device (approximately 40 nA cm⁻²). Moreover, it exhibits a constant output power density of over 6 μW cm⁻² and an open-circuit voltage of up to 400 mV. Our finding may pave a way for developing energy-harvesting devices from ubiquitous evaporation-driven internal water flow in nature with semiconductor material of silicon.     

Improved Sensing Performance of Amperometric Urea Biosensor by Using Platinum Nanoparticles

A novel Platinum nanoparticle (PtNPs) modified Poly(pyrrole-co-1-(2-Aminophenyl)pyrrole)/Urease film coated Au electrode was designed for amperometric detection of urea. PtNPs quantity, film density and pH were optimized and interference effect of some substances readily found in municipal wastewater and blood was investigated. The biosensor responded to urea with a measurement concentration range of 0.1 to 30 mM, a sensitivity of 31.8 μA mM⁻¹ cm⁻², a LOD of 7.58 μM, an accuracy of 104 % and a RSD% of only 0.82. It sensed the concentration of urea in the municipal sewage water with recovery of 97.6 % (n=3) and remained 78 % of its initial response at 28^th day. Results confirmed that PtNPs with strong conductivity improved the electron transfer ability of the working electrode.     

The determination of chromium(VI) in natural waters by differential pulse polarography.

A method utilizing differential pulse polarography for the determination of chromium(VI) in natural water is described. Additions of 0.62 μg Cu(II) ml^-1 and 0.55 μg Fe(III) ml^-1 did not interfere with the determination of 0.050 μg Cr(VI) ml^-1. The natural water samples containing chromium(VI) were buffered to approximately pH 7 with 0.1 M ammonium acetate and 0.005 M ethylene diamine and analyzed. Natural water samples of chromium content from 0.035 μg ml^-1 to 2.0 μg ml^-1 may be analyzed directly without further preparation. The detection limit is 0.010 μg ml^-1.