Calibration of the coil constants and nonorthogonal angles of triaxial NMR coils based on in-situ EPR magnetometers.

Triaxial magnetic field coils are one of the most important components of magnetic resonance sensors. Traditional measurement methods for coil constants and non-orthogonal angles using fluxgate magnetometers are no longer suitable for small-volume nuclear magnetic resonance sensors. This study presents a method for measuring the coil constants and nonorthogonal angles of triaxial nuclear magnetic resonance coils using the dynamics of the electron paramagnetic resonance magnetometer without requiring any additional calibration equipment. After constructing the in-situ magnetometer, we measured the coil constants of the z- and the x-axes as 1189 nT/mA and 45.53 nT/mA, respectively. We obtained the nonorthogonal angle of approximately 0.18° between the z-axis and the x-y plane with a standard deviation of about 0.03° by solving the relevant trigonometric function. Additionally, the non-orthogonal angle between the x- and y-axes is approximately 1.70° with a standard deviation of about 0.17°. This study is significant for evaluating and reducing signal crosstalk errors and improving the accuracy of NMR sensors.

Conductive Polymer-Inorganic Polythiophene/Cd0.5Zn0.5S Heterojunction with Apace Charge Separation and Strong Light Absorption for Boosting Photocatalytic Activity.

In order to utilize the synergistic effect between a conductive polymer and an inorganic semiconductor to efficaciously enhance charge transfer and solve the problem of unsatisfactory performance of a single photocatalyst, thiophene (Th) was polymerized on the Cd0.5Zn0.5S nanoparticle surface to prepare a conductive polymer-inorganic polythiophene/Cd0.5Zn0.5S (PTh/CZS) heterostructrue through a simple in situ oxidation polymerization for the first time. The as-prepared PTh/CZS heterostructures significantly improved photocatalytic TCH degradation and hydrogen production activities. Especially, the 15PTh/CZS sample exhibited the optimal hydrogen production rate (18.45 mmol g-1 h-1), which was 2.51 times higher than pure Cd0.5Zn0.5S nanoparticles. In addition, 15PTh/CZS also showed very fast and efficient photodegradation ability for degrading 88% of TCH in 25 min. Moreover, the degradation rate (0.06229 min-1) was five times more than that of Cd0.5Zn0.5S. The π-π* transition characteristics, high optical absorption coefficient, wide absorption wavelength of PTh, the tight contact interface, and synergistic effect of PTh and Cd0.5Zn0.5S efficiently boosted charge transfer rate and increased the light absorption of PTh/CZS photocatalysts, which greatly enhanced the photocatalytic abilities. Besides, the mechanism of improved photocatalytic activities for TCH degradation and H2 production was also carefully proposed. Undoubtedly, this work would provide new insights into coupling conductive polymers to inorganic photocatalysts for achieving multifunctional applications in the field of photocatalysis.

Cr(VI) anion-imprinted polymer synthesized on mesoporous silicon via synergistic action of bifunctional monomers for precise identification and separation of Cr(VI) from aqueous solution by fixed-bed adsorption.

The novel Cr(VI) anion-imprinted polymer (Cr(VI)-IIP) was prepared by a surface imprinting technique with bifunctional monomers pre-assembly system based on mesoporous silicon (SBA-15). The synthesized Cr(VI)-IIP was characterized by Fourier transmission infrared spectra (FT-IR), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffractometer, N2 adsorption-desorption and thermogravimetric analysis (TGA), proving to be with a highly ordered mesoporous structure, as well as favorable thermal stability. The saturated adsorption amount was 96.32 mg/g, which was 2.7 times higher than that of non-imprinted polymer (NIP). Kinetic experiments showed that the adsorption equilibrium state was obtained within 70 min. In addition, in the selectivity experiments, Cr(VI)-IIP exhibited strong specific recognition ability for Cr(VI) and could realize the separation of Cr(VI) and Cr(III) from an aqueous solution. The dynamic adsorption experiments exhibited that the dynamic adsorption efficiency of Cr(VI)-IIP was as high as 71.57%. Meanwhile, the dynamic regeneration experiments showed that the adsorption amount of Cr(VI)-IIP did not decrease significantly after repeating for five times. All of the findings suggested that Cr(VI)-IIP could achieve precise identification as well as efficient separation of Cr(VI) from aqueous solution.

Optimizing 129Xe and 131Xe relaxation in an NMR gyroscope using buffer gas pressure and wall coating.

The accuracy of inertial measurement performed by the nuclear magnetic resonance gyroscope (NMRG) with two isotopes depends on the duration of transverse relaxation. Extending the relaxation of the xenon isotopes at the same time plays a very important role in the accuracy of gyro. The relaxation time of 129Xe and 131Xe can be increased to about 15-20 s by optimizing the buffer gas pressure of N2 at about 0.57 amg and coating RbH, respectively. According to the results of theoretical analysis and experimentation, the gyro stability reaches 0.6°/h, and the active measurement volume is 3 × 3 × 3 âˆ¼ mm3.

Significantly Enhanced Photocatalytic Performance of the g-C3N4/Sulfur-Vacancy-Containing Zn3In2S6 Heterostructure for Photocatalytic H2 and H2O2 Generation by Coupling Defects with Heterojunction Engineering.

Light-driven splitting of water to produce H2 and reduction of molecular oxygen to synthesize H2O2 from water are the emerging environmentally friendly methods for converting solar energy into green energy and chemicals. In this paper, vacancy defect and heterojunction engineering effectively adjusted the conduction band position of Zn3In2S6, enriched the electron density, broadened the optical absorption range, increased the specific surface area, and accelerated the charge carrier transfer and separation of g-C3N4/sulfur-vacancy-containing Zn3In2S6 (CN/Vs-ZIS) heterostructures. As a result, all of the CN/Vs-ZIS heterostructures possessed greatly enhanced photocatalytic activities and the optimized sample 2CN/Vs-ZIS exhibited the highest visible-light photocatalytic performance. The rate of generation of H2 of 2CN/Vs-ZIS under visible light (λ > 420 nm) was 6.55 mmol g-1 h-1, which was 1.76 and 6.06 times higher than those of Vs-Zn3In2S6 and g-C3N4, respectively, and the apparent quantum yield (AQY) was 18.6% at 420 nm. Meanwhile, the 2 h yield of H2O2 of 2CN/Vs-ZIS was 792.02 µM, ∼4.72 and ∼6.04 times higher than those of pure Vs-Zn3In2S6 and g-C3N4, respectively. The enhanced reaction mechanisms for the production of photocatalytic H2 and H2O2 were also investigated. This work undoubtedly demonstrates that the synergistic effects of defect and heterojunction engineering will be the great promise for improving the photocatalytic efficiency of Zn3In2S6-based materials.

Hierarchical Sb2S3/ZnIn2S4 core-shell heterostructure for highly efficient photocatalytic hydrogen production and pollutant degradation.

In this work, a novel hierarchical 1D/2D core/shell Sb2S3-ZnIn2S4 (SB-ZIS) heterostructure with highly efficient photocatalytic activities for both hydrogen production from water and organic pollutant degradation was designed and fabricated via a simple one-step hydrothermal method. The as-prepared SB-ZIS heterostructure, where ZnIn2S4 nanosheets uniformly grew onto Sb2S3 nanorod to form a tight and large intimate contacted interface, was conducive to improve the absorption capacity of light, increase the surface area, shorten the distance of electronic transmission channels and accelerate the separation and migration of photogenerated carriers. As a result, the presented SB-ZIS composites demonstrated significantly enhanced photocatalytic performances for H2 generation and Tetracycline Hydrochloride (TCH) photodegradation. The photocatalytic H2 production rate of optimal SB-ZIS-2 sample (1685.14 µmol·g-1·h-1) was about 12.24 times as large as that of pure ZnIn2S4 (137.63 µmol·g-1·h-1). The apparent quantum efficiency (AQE) at 420 nm was up to 3.8%. In addition, the highest rate constant for TCH removal (0.514 h-1) was 20.3 and 2.89 times larger than those of pure Sb2S3 and Znln2S4, respectively. The possible reaction routes of TCH and the photocatalytic reaction mechanism of SB-ZIS sample were also discussed in detail. This work will provide some useful information for the development of dual-functional Sb2S3-based type I core-shell heterostructure with an efficient photocatalytic activity for solving environmental pollution and producing clean hydrogen energy.

Large-aperture single-mode 795 nm VCSEL for chip-scale nuclear magnetic resonance gyroscope with an output power of 4.1 mW at 80 °C.

Transverse optical confinement in oxide-confined vertical-cavity surface-emitting lasers (VCSELs) crucially depends on thickness of oxide layer and its position relative to a standing wave. Modifying the structure reduces the overlap between the oxide layer and the standing wave as well as effective refractive index difference between core and cladding of the VCSEL that subsequently decreases of the number of transverse modes and increases the mode extension beyond oxide aperture. A 795 nm VCSEL is designed and fabricated with this concept. The proposed device achieves high single-mode operation of 4.1 mW at 80 °C, SMSR of 41.68 dB, and OPSR of 27.4 dB. VCSEL is applied in a nuclear magnetic resonance gyroscope (NMRG) system as pump source due to its excellent device performance and satisfactory test results are obtained.

Ta3N5 nanoparticles/TiO2 hollow sphere (0D/3D) heterojunction: facile synthesis and enhanced photocatalytic activities of levofloxacin degradation and H2 evolution.

Active removal of recalcitrant antibiotic contaminants for wastewater purification and hydrogen evolution from water splitting using hollow-structured photocatalysts has attracted considerable interest in the field of environmental governance and energy conversion. Herein, 0D Ta3N5 nanoparticles anchored on 3D TiO2 hollow nanosphere composites (0D/3D Ta/Ti) were designed and fabricated via a feasible surface self-assembly process for the first time. Various techniques were employed to characterize the structure and optical properties of the as-prepared samples. The photocatalytic activities of Ta3N5/TiO2 hybrids were systematically evaluated via both photodegradation of levofloxacin (LEV) and water splitting for hydrogen evolution under solar light irradiation. The degradation results showed that the x-Ta/Ti composites exhibit remarkably better performances for LEV degradation than pristine TiO2. The 3 wt% Ta3N5 nanoparticle-loaded hollow TiO2 composite material exhibited optimal photocatalytic activity (92.79%), and its degradation rate constant was 3.04 times that of TiO2. Simultaneously, the 3-Ta/Ti composite also possessed high ability to degrade other antibiotics such as ciprofloxacin (CIP) and tetracycline hydrochloride (TCH) and colored organic dyes such as Rhodamine B (RhB). Besides, x-Ta/Ti composites exhibited higher photocatalytic hydrogen evolution activities compared with TiO2 hollow spheres. The efficient charge transfer and separation between the close heterogeneous interfaces, broadened spectral response range and improved specific surface area were mainly responsible for the superior photocatalytic performance of the x-Ta/Ti nanocomposite. Our study provides an effective strategy for the design of hollow structure composite photocatalysts with excellent photocatalytic performances not only for pollutant removal, but also for efficient solar-to-fuel conversion.

A novel 3D/2D CdIn2S4 nano-octahedron/ZnO nanosheet heterostructure: facile synthesis, synergistic effect and enhanced tetracycline hydrochloride photodegradation mechanism.

In this work, 3D CdIn2S4 nano-octahedron/2D ZnO nanosheet heterojunctions (CIS/ZO-x) were fabricated for the first time via a facile and green impregnation-hydrothermal method, where three-dimensional (3D) CdIn2S4 nano-octahedra densely anchor onto both sides of 2D ZnO nanosheets to form an embedded nanostructure with intimate interfacial contacts. Various characterization techniques were adopted to measure the morphologies, structures and optical properties of the as-prepared CIS/ZO-x heterojunctions in detail. The photocatalytic performance of the as-prepared CIS/ZO-x was evaluated via the photodegradation of tetracycline hydrochloride (TCH) under visible light irradiation, and the result shows that the hybridization of ZnO nanosheets with CdIn2S4 nano-octahedra significantly enhances the photocatalytic activity of heterojunctions. The highly stable and reusable sample CIS/ZO-2 possesses the highest photocatalytic activity (94.04%), and its rate constant (k = 0.06357 min-1) is about 4.96 and 22.31 times as high as those of pure CdIn2S4 and ZnO. Interestingly, the removal efficiency of TCH and the rate constant are also much higher than those of numerous previously reported composite photocatalysts. The synergistic effect and the unique 3D/2D hybrid structure with intimate interfacial contacts are primarily responsible for the enhanced photocatalytic activity. A possible photocatalytic mechanism for the TCH photodegradation over the CIS/ZO sample is also proposed. This work provides a novel 3D/2D composite photocatalyst for the efficient removal of antibiotic pollutants and will be helpful for designing other 3D/2D heterojunctions.

A molecularly imprinted polymer placed on the surface of graphene oxide and doped with Mn(II)-doped ZnS quantum dots for selective fluorometric determination of acrylamide.

A polymer imprinted with acrylamide (AM-MIP) was synthesized on the surface of graphene oxide by surface polymerization of propionamide (serving as a dummy template), methacrylic acid (as the functional monomer) and ethylene glycol dimethacrylate (the cross-linker). ZnS quantum dots (QDs) doped with Mn(II) ions were added to the AM-MIP to act as fluorescence source. The AM-MIP was characterized by infrared spectroscopy, scanning electron microscopy and X-ray powder diffraction, suggesting that the imprinted layer was successfully grafted onto graphene oxide. The fluorescence of the doped QDs is quenched when loading the AM-MIP with acrylamide (AM), and the quenching effect is much stronger than the non-imprinted polymer (AM-NIP). Quenching follows Stern-Volmer kinetics. The combination of imprinting and fluorometric detection offer AM-IIP capability to accumulate trace AM before direct determination, omitting desorption and separation or other methods. The excitation and emission spectra of AM-MIP peak at 325 nm and 601 nm, respectively. Under optimal conditions, fluorescence drops linearly in the 0.5-60 µmol·L-1 acrylamide concentration range, and the detection limit is 0.17 µmol·L-1. The method has been applied to the determination of AM in spiked water samples and gave recoveries in the range from 100.2 to 104.5%, with relative standard deviations in the 1.9 to 3.9% range. In our perception, the AM-MIP presented here is a promising fluorescent probe for the detection of trace acrylamide in food. Graphical abstract Schematic of the preparation of graphene oxide coated with a molecularly imprinted polymer doped with Mn(II)-doped ZnS quantum dots. Propionamide serves as a dummy template. Acrylamide acts as a quencher of fluorescence, and this effect is used for its selective fluorometric determination.

Tailor-made ion-imprinted polymer based on functionalized graphene oxide for the preconcentration and determination of trace copper in food samples.

A tailor-made Cu(II) ion-imprinted polymer based on large-surface-area graphene oxide sheets has been synthesized for the preconcentration and determination of trace copper from food samples by solid-phase extraction. Attributed to the ultrahigh surface area and hydrophilicity of graphene oxide, the Cu(II) ion-imprinted polymer prepared by the surface ion-imprinting technique exhibited a high binding capacity and a fast adsorption rate under the optimized experimental conditions. In the static adsorption experiments, the maximum adsorption capacity of Cu(II) ion-imprinted polymer is 109.38 mg/g at 25°C, which is much higher than that of the nonimprinted polymer (32.12 mg/g). Meanwhile, the adsorption is very rapid and equilibrium is reached after approximately 30 min. The adsorption mechanism is found to follow Langmuir adsorption model and the pseudo-second-order adsorption process. The Cu(II) ion-imprinted polymer was used for extracting and detecting Cu(II) in food samples combined with graphite flame atomic adsorption spectrometry with high recoveries in the range of 97.6-103.3%. The relative standard deviation and limit of detection of the method were evaluated as 1.2% and 0.37 µg/L, respectively. The results showed that the novel absorbent can be utilized as an effective material for the selective enrichment and determination of Cu(II) from food samples.

Preparation of a Two-Dimensional Ion-Imprinted Polymer Based on a Graphene Oxide/SiO2 Composite for the Selective Adsorption of Nickel Ions.

In the present work, a novel two-dimensional (2D) nickel ion-imprinted polymer (RAFT-IIP) has been successfully synthesized based on the graphene oxide/SiO2 composite by reversible addition-fragmentation chain-transfer (RAFT) polymerization. The imprinted materials obtained are characterized by Fourier transmission infrared spectrometry (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results show that the thermal stability of the graphene oxide/SiO2 composite is obviously higher than that of graphene oxide. RAFT-IIP possesses an excellent 2D homogeneous imprinted polymer layer, which is a well-preserved unique structure of graphene oxide/SiO2. Owing to the intrinsic advantages of RAFT polymerization and 2D imprinted material, RAFT-IIP demonstrate a superior specific adsorption capacity (81.73 mg/g) and faster adsorption kinetics (30 min) for Ni(II) in comparison to the ion-imprinted polymer prepared by traditional radical polymerization and based on the common carbon material. Furthermore, the adsorption isotherm and selectivity toward Ni(II) onto RAFT-IIP and nonimprinted polymer (NIP) are investigated, indicating that RAFT-IIP has splendid recognizing ability and a nearly 3 times larger adsorption capacity than that of NIP (30.94 mg/g). Moreover, a three-level Box-Behnken experimental design with three factors combining the response surface method is utilized to optimize the desorption process. The optimal conditions for the desorption of Ni(II) from RAFT-IIP are as follows: an HCl-type eluent, an eluent concentration of 2.0 mol/L, and an eluent volume of 10 mL.

An ion-imprinted functionalized SBA-15 adsorbent synthesized by surface imprinting technique via reversible addition-fragmentation chain transfer polymerization for selective removal of Ce(III) from aqueous solution.

A novel Ce(III) ion-imprinted polymer (Ce(III)-IIP) has been prepared by surface imprinting technique with reversible addition-fragmentation chain transfer (RAFT) polymerization based on support matrix of SBA-15. The prepared adsorbent is characterized by FT-IR, XRD, SEM, TEM, nitrogen adsorption-desorption, GPC, and TGA. The results suggest that the surface imprinted polymer synthesized by RAFT is a thin layer. For adsorption experiments, Ce(III)-IIP is investigated to remove Ce(III) by column study at different flow rates, initial metal ion concentrations, and adsorption temperature. The dynamic kinetics analyses reveal that the overall adsorption process is successfully fitted with the pseudo-first-order kinetic model and the equilibrium time was 60 min. Meanwhile, the experimental data is in good agreement with Thomas model. Ce(III)-IIP has the excellent selectivity and regenerate property. Meanwhile, the proposed method has been successfully applied in the removal of Ce(III) in natural water samples with satisfactory results. All the results suggest that Ce(III)-IIP could be used as an excellent adsorbent for efficient removal of Ce(III) from aqueous solution.

Speciation, adsorption and determination of chromium(III) and chromium(VI) on a mesoporous surface imprinted polymer adsorbent by combining inductively coupled plasma atomic emission spectrometry and UV spectrophotometry.

In the present study, a Cr(III)-imprinted polymer (Cr(III)-IIP) was prepared by an easy one-step sol-gel reaction with a surface imprinting technique on the support of silica mesoporous material. A new SPE method for the speciation, separation, preconcentration, and determination of Cr(III) and Cr(VI) by inductively coupled plasma atomic emission spectrometry and UV on the mesoporous-imprinted polymer adsorbent was developed. The structure of the imprinted polymer was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The adsorption kinetics, thermodynamics behavior, and recognition ability toward Cr(III) on Cr(III)-IIP and nonimprinted polymer were compared. The results showed that Cr(III)-IIP had higher selectivity and nearly a two times larger Langmuir adsorption capacity (38.50 mg/g) than that of NIP. The proposed method has been successfully applied in the determination and speciation of chromium in natural water samples with satisfactory results.

Selective adsorption behavior of Pb(II) by mesoporous silica SBA-15-supported Pb(II)-imprinted polymer based on surface molecularly imprinting technique.

In this study, a new Pb(II) ion-imprinted polymer (Pb(II)-IIP), which can be used for selective adsorption of Pb(II) from aqueous solutions, was successfully prepared based on the supported material of ordered mesoporous silica SBA-15 with the help of surface molecular imprinting technology. The prepared polymer was characterized by Fourier transmission infrared spectrometry, X-ray diffraction, transmission electron microscope and nitrogen adsorption-desorption isotherm. The results showed that the synthesized polymer possessed high ordered mesoporous structure. The adsorption behavior of the adsorbents for Pb(II) was investigated using batch experiments. The Pb(II)-IIP showed fast kinetics, high selectivity and satisfied adsorption capacity for adsorption of Pb(II). Under the optimum experimental condition, Pb(II) adsorption process over Pb(II)-IIP follows pseudo-second-order reaction kinetics and follows the Langmuir adsorption isotherm. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of Pb(II) onto Pb(II)-IIP was a spontaneous and exothermic nature of the process.