Activated carbon has an excellent porous structure and is considered a promising adsorbent and electrode material. In this study, activated carbon fibers (ACFs) with abundant microporous structures, ...derived from natural cotton fibers, were successfully synthesized at a certain temperature in an Ar atmosphere and then activated with KOH. The obtained ACFs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), elemental analysis, nitrogen and carbon dioxide adsorption–desorption analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption measurement. The obtained ACFs showed high porous qualities and had a surface area from 673 to 1597 m2/g and a pore volume from 0.33 to 0.79 cm3/g. The CO2 capture capacities of prepared ACFs were measured and the maximum capture capacity for CO2 up to 6.9 mmol/g or 4.6 mmol/g could be achieved at 0 °C or 25 °C and 1 standard atmospheric pressure (1 atm). Furthermore, the electrochemical capacitive properties of as-prepared ACFs in KOH aqueous electrolyte were also studied. It is important to note that the pore volume of the pores below 0.90 nm plays key roles to determine both the CO2 capture ability and the electrochemical capacitance. This study provides guidance for designing porous carbon materials with high CO2 capture capacity or excellent capacitance performance.
•Nutrient composition of R. amabilis from Qinghai-Tibetan Plateau studied for 1st time.•Amino acid, fatty acid, mineral contents of Rubus amabilis were analyzed.•Results showed that leaves contain ...higher TAA than other plant parts.•High amounts of methionine are present in free and total amino acids.•The leaf contains 36.5% unsaturated fatty acids and linolenic acid.
The amino acid, fatty acid, and mineral content of Rubus amabilis harvested from the Qinghai-Tibetan Plateau were analyzed. Results revealed that the total amino acids in the leaves, fruits, roots, and stems of R. amabilis were 17.1, 7.5, 6.5, and 5.7g, respectively. Further analysis of the amino acids showed that the protein contained nutritionally useful quantities of essential amino acids. The total essential amino acids in the leaves of R. amabilis were 9.3g ETAAs/100g. Total fatty acids varied in different parts of R. amabilis. Stearic acid, linolenic acid, linoleic acid, and palmitic acid in the leaf samples were 41.4%, 13.7%, 11.9%, and 6.7%, respectively. Lauric acid, oleic acid, docosahexoenoic acid, and eicosenoic acid were present only in small quantities. Potassium, magnesium, and calcium were the most abundant minerals in the leaf samples. Among the essential trace mineral elements, Fe exhibited the highest content in different parts of R. amabilis.
Rubus amabilis, Rubus niveus Thunb., and Rubus sachalinensis are three Rubus species that are alternatively found in Manubzhithang, a Tibetan medicine, in different areas of China. The current study ...analyzed HPLC/UV chromatograms and it compared compounds of these three Rubus species in contrast to reference substances such as 2,6-dimethoxy-4-hydroxyphenol-1-O-β-D-glucopyranoside, procyanidin B4, and isovitexin-7-O-glucoside. The three Rubus species produced similar peaks in chromatograms. The antioxidant activity of the three Rubus species was determined using an assay for DPPH free radical scavenging activity. Results indicated that the three Rubus species extracts had almost the same level of free radical scavenging activity. Thus, findings indicated the rationality of substituting these species for one another as an ingredient in Manubzhithang.
•ZnO@In2O3 core@shell nanofibers was synthesized by a coaxial electrospinning method.•A type II heterojunction was created at the interface of ZnO core and In2O3 shell.•The sensor presents enhanced ...gas-sensing performance.•The sensor exhibits excellent selectivity and stability.•A depletion modulating mechanism of shell is proposed.
One-dimensional ZnO@In2O3 core@shell nanofibers (CSNFs) were synthesized via a facile coaxial electrospinning method followed by high-temperature pyrolysis treatment. The obtained nanofibers have a well-defined core@shell structure with ZnO as the core and In2O3 as the shell. Compared with the pure ZnO nanofibers and pure In2O3 nanofibers, the ZnO@In2O3 CSNFs based sensor presents the highest response to ethanol (31.87 at 100ppm) at an operating temperature of 225°C, which can be ascribed to the formation of a completely electron depletion layer in In2O3 shell. Moreover, the ZnO@In2O3 CSNFs based sensor also demonstrates outstanding selectivity, excellent stability and low detection limitation (∼5ppm) to ethanol vapor. The ultraviolet photoelectron spectroscopy confirms a type-II heterojunction formed at the interface of ZnO core and In2O3 shell. The main mechanism for the enhanced performance of ZnO@In2O3 CSNFs gas sensor is the depletion modulating of In2O3 shell layer in electron transfer. These results are valuable for the practical application of ZnO@In2O3 CSNFs in ethanol detection.
Pure and 4 wt% Ag-doped ZnSn(OH)6 were fabricated via one-step hydrothermal treatment, respectively, and the two samples were characterized by XRD, XPS, SEM and TEM technologies. Test results reveal ...that the Ag-doped ZnSn(OH)6 is a hollow microspheres with porous structure. What’s more, the Ag-doped ZnSn(OH)6 based on sensor exhibited a relatively high sensing response (49.12) and fast response/recovery capability (16/10 s) to 100 ppm formaldehyde than those to pure ZnSn(OH)6 (24.78) at 200 °C. The reason for enhancement was contributed to hollow spherical structure, which provided higher specific surface area, more active sites. In addition, the Ag doping was conducive to gas molecules dissociation, which stimulated the reactions happening between the sensing material and gas molecules. Thus, the Ag-doped ZnSn(OH)6 is more suitable and promising candidate material to prepare gas sensor for detecting formaldehyde.
•The Ag-ZnSn(OH)6 hollow porous microspheres were firstly synthesized.•The response of Ag-ZnSn(OH)6 samples is 49.12–100 ppm formaldehyde at 200 °C.•The gas sensing mechanism of Ag-ZnSn(OH)6 hollow porous microspheres was analyzed.•The Ag-doping can effectively optimize gas-sensing properties of ZnSn(OH)6.
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•Indium tin oxide nanotubes with different Sn doping concentrations were synthesized by electrospinning.•A specific response has been proposed to better characterize the sensing ...performances of gas sensors.•Facilitated transport channel for electrons can benefit the decrease in working temperatures.•Oxygen vacancies can mainly affect the sensitivity of gas sensor.
It’s demonstrated that the defects induced by doping can greatly influence the sensing properties of oxide-based gas sensors. In this work, the authors have designed indium tin oxide nanotubes (ITO NTs) with different Sn doping concentrations. Results showed that the walls of ITO NTs are comprised of the formed ITO and redundant In2O3 nanoparticles (NPs) at low doping concentration, and the doping-induced oxygen vacancies (Vo··S) can be tuned by Sn concentrations. Series of sensing tests to formaldehyde gas indicated that the ITO-7 NTs show the lowest working temperature (160 °C) and the highest specific response. Here, It is noted that to eliminate the influence of the coating amount of sensing performances, a concept of specific response was proposed i.e., Rair/(m–Rgas), where Rair and Rgas respectively stand for the resistances of gas sensors in the reference gas (in air this case) and in the test gas ambience, and m stands for the mass of the coated sensing materials. The decreased working temperature could be attributed to the formed In2O3 NPs/ITO tubular structure, and the enhanced specific response might be mainly associated with the Vo··S. Furthermore, a possible gas sensing enhancing mechanism via Vo··S for ITO-based gas sensors was proposed based on our results and analysis. This research would give some instructive advice to design high-performances oxide-based gas sensors via tuning the Vo··S.
The radiative and Auger decay of K-shell hole states of argon ions with configuration 1s2sm2pn3 s23p6 (m=0–2; n = 0–6) are studied theoretically using the flexible atomic code. The effect of L-shell ...spectator vacancies on the competition of filling the K, L1, and L23 vacancies is discussed for the first time. We find the K or L1 vacancy is preferred to be filled first when there is 0 or 1 vacancy in the L23 shell, but the L23 vacancy becomes the priority when the number of the L23 vacancies is larger than 2, and the total branching ratio of the L23 vacancy is as high as 66.98%, 74.66%, and 80.95% when the L23 shell has 4 vacancies and there are 2, 1 and 0 vacancies in the L1 shell, respectively. In addition, the natural widths of the K, L1, and L23 vacancies with different L-shell vacancy distributions are also calculated. The results show that they all first increase and then decrease with the number of L23 vacancies. It is expected that the present study will be useful for the qualitative analysis of the decay processes of multiple hole states, the understanding of ion yields and the production of satellites in x-ray and Auger spectra.
•Competition to fill the vacancies in the K, L1, and L23 shells.•K or L1 vacancy is preferred to be filled first.•L23 vacancy becomes the priority.•Natural widths of the K, L1 and L23 vacancies first increase and then decrease.•Useful for the qualitative analysis of the decay processes of multiple hole states.
A promising phosphors Ca2Al2SiO7:Tm3+,Dy3+ were synthesized by conventional high temperature sintering. Phase identification, crystal structure refinement, luminescence properties, energy transfer ...mechanism of Tm3+ → Dy3+, and CIE color coordinates were investigated systematically. The phase structure of prepared phosphors were confirmed by XRD analysis and structure refinement. From the results of photoluminescence, the CASO: Tm3+ phosphors showed intense blue light emission peaks at 454 nm (the transition from 1D2 to 3F4), while CASO:Dy3+ phosphors exhibited predominant yellow light emission peaks at 581 nm (the transition from 4F9/2 to 6H13/2), implying that the Dy3+ were located in the non-inverted symmetric site of the CASO host lattice. Meanwhile, the results exhibited that the optimal doping content of Dy3+ was 0.01, and the mechanism of concentration quenching was the nearest-neighbor ions interaction. The overlapped emission (Tm3+)/excitation (Dy3+) spectra, decay curves and the energy level scheme about CASO:Tm3+,Dy3+ confirmed the energy transfer of Tm3+ → Dy3+. Moreover, by adjusting Tm3+/Dy3+ ions concentration, the intensities of yellow emission for Dy3+ and blue emission for Tm3+ could be adjusted to tune the emitting color of CASO:Tm3+, Dy3+. Excited by the most effective excitation wavelength at 355 nm, the CIE coordinates (0.3422, 0.3262) of phosphor CASO:0.01Tm3+, 0.01Dy3+ was closest to the coordinates of white chromaticity (0.33, 0.33). Results indicate that the potential value of phosphors Ca2Al2SiO7:Tm3+,Dy3+ are used as a single-phase color-adjustable phosphors for NUV pumped white-LEDs.
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•Novel multicolor tunable Ca2Al2SiO7:Tm3+, Dy3+ phosphors were developed.•Crystal structure refinement of Ca2Al2SiO7:Tm3+, Dy3+ phosphors were investigated systematically.•The energy transfer mechanism of Tm3+ → Dy3+ was discussed.
Air humidity is a major factor that degrades the performance and long-term stability of metal-oxide-semiconductor (MOS) based gas sensors. In this work, we propose an encapsulation strategy by ...coating a mesoporous silica molecular sieve (SBA-15) on rare earth doped tin oxide (RE-SnO2) nanofibers for humidity-resistant hydrogen detection. In this design, the hydrophobic SBA-15 sieve layer effectively blocks the water molecules without affecting hydrogen diffusion, while the RE dopant greatly improves the responsivity and lowers down the operating temperature of the sensors, As a result, the Er-SnO2/SBA-15 and Tb-SnO2/SBA-15 sensors respectively show the maximum response values of 27.71 and 33.68 (to 10 ppm hydrogen at 280 °C, 4.67 and 5.67 times that of the bare SnO2 ones, respectively), short response/recovery time (< 1.0 s / < 1.0 s), as well as a low limit of detection for hydrogen (200 ppb) and a good gas selectivity. Under the protection of the SBA-15 sieve layer, the response retention of the sensors is significantly improved when the humidity increases from 25% to 85% RH (Er-doping, from 38.8% to 60.0%; Tb-doping, form 25.6–57.8%). Besides, further analysis on enhancement mechanism of response indicates that the SBA-15 coating contribute about 1/3 of the response enhancements via its own hydrogen physical adsorption capacity and the induced oxygen vacancies during the calcination processes.
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•Humidity-resistant hydrogen sensor was designed using the electrospun RE-SnO2 nanofibers and the mesoporous silica coating.•Both RE doping and SBA-15 coating benefit the sensing response of SnO2-based sensor towards hydrogen.•The increased response of the SBA-15 encapsulated sensors was due to the decreased Rg.•The SBA-15 coating also increases the response value via increasing the OVs and the hydrogen adsorbed on its surface.
One-dimensional ZnO@In2O3 core@shell nanofibers (CSNFs) were synthesized via a facile coaxial electrospinning method followed by high-temperature pyrolysis treatment. The obtained nanofibers have a ...well-defined core@shell structure with ZnO as the core and In2O3 as the shell. Compared with the pure ZnO nanofibers and pure In2O3 nanofibers, the ZnO@In2O3 CSNFs based sensor presents the highest response to ethanol (31.87 at 100 ppm) at an operating temperature of 225 °C, which can be ascribed to the formation of a completely electron depletion layer in In2O3 shell. Moreover, the ZnO@In2O3 CSNFs based sensor also demonstrates outstanding selectivity, excellent stability and low detection limitation (∼5 ppm) to ethanol vapor. The ultraviolet photoelectron spectroscopy confirms a type-II heterojunction formed at the interface of ZnO core and In2O3 shell. The main mechanism for the enhanced performance of ZnO@In2O3 CSNFs gas sensor is the depletion modulating of In2O3 shell layer in electron transfer. These results are valuable for the practical application of ZnO@In2O3 CSNFs in ethanol detection.
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