Herein, the authors produce Co‐based (Co3(PO4)2, Co3O4, and Co9S8) electrocatalysts via pulsed laser ablation in liquid (PLAL) to explore the synergy of anion modulation on phase‐selective active ...sites in the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Co3(PO4)2 displays an ultralow overpotential of 230 mV at 10 mA cm−2 with 48.5 mV dec−1 Tafel slope that outperforms the state‐of‐the‐art Ir/C in OER due to its high intrinsic activity. Meanwhile, Co9S8 exhibits the highest HER performance known to the authors among the synthesized Co‐based catalysts, showing the lowest overpotential of 361 mV at 10 mA cm−2 with 95.8 mV dec−1 Tafel slope in the alkaline medium and producing H2 gas with ≈500 mmol g−1 h−1 yield rate under −0.45 V versus RHE. The identified surface reactive intermediates over in situ electrochemical–Raman spectroscopy reveal that cobalt(hydr)oxides with higher oxidation states of Co‐cation forming under oxidizing potentials on the electrode–electrolyte surface of Co3(PO4)2 facilitate the OER, while Co(OH)2 facilitate the HER. Notably, the fabricated two‐electrode electrolyzers using Co3(PO4)2, Co3O4, and Co9S8 electrocatalysts deliver the cell potentials ≈2.01, 2.11, and 1.89 V, respectively, at 10 mA cm−2. This work not only shows PLAL‐synthesized electrocatalysts as promising candidates for water splitting, but also provides an underlying principle for advanced energy‐conversion catalysts and beyond.
Co‐based electrocatalysts fabricated via the pulsed laser ablation in liquid process for water splitting are presented. The fabricated two‐electrode water electrolyzers using Co3(PO4)2, Co3O4, and Co9S8 can deliver the cell potentials of 2.01, 2.11, and 1.89 V, respectively.
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•rGO/ZnO nanosheets sensitized by Au have been successfully synthesized by pulsed laser ablation and sputtering method.•Au/rGO/ZnO sensor has a high response, long-term stability, and ...selectivity under UV illumination at room temperature.•The enhanced mechanism could be attributed to the high conductivity of rGO, spill-over of Au, and high surface area of ZnO.
Extended surface area in addition to higher conductivity and abundant free electrons/holes generation has been key players for any efficient sensor design. Therefore, contribution from graphene as highest conductive material and plasmonics from gold (Au) were expected to facilitate efficient zinc oxides (ZnO) nanostructures-based Hydrogen gas detection. We have presented herewith a facile route to synthesize ZnO nanosheets from elongated nanoblocks of the same in presence of reduced graphene oxide (rGO) under laser ablation environment. Au decorated such rGO/ZnO heterostructured nanosheets were found to be highly selective and sensitive to H2 detection under ultraviolet radiation at room temperature (RT). A detailed investigation was carried out to confirm topographic evolution through high resolution scanning electron microscopy. Optical band gap and infrared absorption of as-synthesized specimens at different stages were investigated further in addition to structural confirmation using X-ray diffraction analysis. Raman spectroscopy, a complementary technique was utilized to investigate the specimens at different stages too. SEM-aided elemental analysis inferred that gold nanoparticles were homogeneously distributed over the rGO/ZnO heterostructure. A custom-made setup designed at our disposal were utilized to understand the selectivity and sensitivity of as-fabricated heterostructure for H2 detection. The H2 gas sensing properties of Au nanoparticles decorated rGO/ZnO heterostructure were investigated at RT under UV irradiation and compared with those observed using pristine ZnO nanostructure at high working temperature. A plausible mechanism was illustrated with reference to well-known ‘spell-over’ scenario usually observed in plasmonic sensors.
ZnO nanoparticles were generated by laser ablation process in liquid media to decorate carbon nanotubes (CNTs) with different amounts of ZnO nanoparticles on their tubular surface in just one step ...for catalytic degradation against methylene blue dye. The amount of decorated ZnO nanoparticles was controlled by optimizing the laser ablation time. Several techniques were used to investigate the nanocomposite structure as optical, structural, and morphological studies showing that the absorbance characteristic peak showed a difference due to the effect of ZnO/carbon nanotubes interaction. Besides, from X-ray diffraction, it was seen that the diffraction patterns were very closely matched to the crystalline peaks of graphite skeleton and ZnO structure. Moreover, the amount of active sites was increased after decoration to confirm the presence of their interaction. Additionally, it was noted that the amount of coating on CNTs with ZnO was increases as the ablation time increases. This research proved that the existence of CNTs playing a vital role in the composite for the enhancement of the catalytic efficiency compared with pristine ZnO.
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•ZnO-MWCNTs nanocomposite was synthesized by ablation of Zn target in f-MWCNTs.•The as-prepared nanocomposite has a good catalytic activity against MB.•The produced nanocomposite has high distribution without using any surfactant.•The nanocomposites were synthesized via simple one-pot green method.•The nanocomposites were characterized by XRD, Raman, XPS, SEM, UV–vis, FT-IR and PL.
Sedum alfredii is one of a few species known to hyperaccumulate zinc (Zn) and cadmium (Cd). Xylem transport and phloem remobilization of Zn in hyperaccumulating (HP) and nonhyperaccumulating (NHP) ...populations of S. alfredii were compared.
Micro-X-ray fluorescence (μ-XRF) images of Zn in the roots of the two S. alfredii populations suggested an efficient xylem loading of Zn in HP S. alfredii, confirmed by the seven-fold higher Zn concentrations detected in the xylem sap collected from HP, when compared with NHP, populations. Zn was predominantly transported as aqueous Zn (> 55.9%), with the remaining proportion (36.7–42.3%) associated with the predominant organic acid, citric acid, in the xylem sap of HP S. alfredii.
The stable isotope 68Zn was used to trace Zn remobilization from mature leaves to new growing leaves for both populations. Remobilization of 68Zn was seven-fold higher in HP than in NHP S. alfredii. Subsequent analysis by μ-XRF, combined with LA-ICPMS (laser ablation-inductively coupled plasma mass spectrometry), confirmed the enhanced ability of HP S. alfredii to remobilize Zn and to preferentially distribute the metal to mesophyll cells surrounding phloem in the new leaves.
The results suggest that Zn hyperaccumulation by HP S. alfredii is largely associated with enhanced xylem transport and phloem remobilization of the metal. To our knowledge, this report is the first to reveal enhanced remobilization of metal by phloem transport in hyperaccumulators.
The Dora‐Maira massif is an archetypal nappe stack of subducted and exhumed upper crust. Slices of continental crust experienced metamorphism at upper blueschist to ultrahigh‐pressure (UHP) ...eclogite‐facies conditions. While the timing of peak metamorphism in the UHP unit has been extensively studied, little is known about the other units. In order to constrain the timing and conditions of high‐pressure metamorphism, U‐Pb‐trace element analyses of rutile and titanite were carried out across the nappe stack. The data reveal Alpine peak metamorphic ages younging downwards in the stack, from ∼40 to ∼33 Ma. Greenschist‐facies retrogression of the whole massif occurred at ∼32–31 Ma, after high‐pressure metamorphism of the lowermost unit (Sanfront‐Pinerolo Unit). Tectonic implications include (a) continuous and fast exhumation of subducted continental crust, (b) long‐lived subduction from ∼60 to ∼33 Ma of the distal European margin, reconstructed to be a hyperextended margin spread over ∼130 km for the Dora‐Maira massif alone, and (c) the initiation of continental collision synchronous with the end of high‐pressure metamorphism.
Key Points
Rutile U‐Pb geochronology contrains peak metamorphism of Dora‐Maira units younging downward in the nappe stack from ∼40 to ∼33 Ma
Continuous and fast exhumation of subducted continental crust
Approximately 200 km hyperextended European margin prior to subduction
Minor and trace elements can substitute into the crystal lattice of galena at various concentrations. In situ LA-ICP-MS analysis and trace element mapping of a range of galena specimens from ...different deposit types are used to obtain minor/trace element data, aimed at achieving insight into factors that control minor/trace element partitioning. The previously recognized coupled substitution Ag++(Bi,Sb)3+ ⇌ 2Pb2+ is confirmed. However, the poorer correlation between Ag and (Bi+Sb) when the latter elements are present at high concentrations (∼>2000 ppm), suggests that site vacancies may come into play: 2(Bi,Sb)3++∎ ⇌ 3Pb2+. Galena is the primary host of Tl in all mapped mineral assemblages. Along with Cu, Tl is likely incorporated into galena via the coupled substitution: (Ag,Cu,Tl)++(Bi,Sb)3+ ⇌ 2Pb2+. Tin can reach significant concentrations in galena (>500 ppm). Cd and minor Hg can be incorporated into galena; the simple isovalent substitution (Cd,Hg)2+ ⇌ Pb2+ is inferred. This paper shows for the first time, oscillatory and sector compositional zoning of minor/trace elements (Ag, Sb, Bi, Se, Te, Tl) in galena from two epithermal ores. Zoning is attributed to slow crystal growth into open spaces within the vein at relatively low temperatures.The present data show that galena can host a broader range of elements than previously recognized. For many measured elements, the data sets generated display predictable partitioning patterns between galena and coexisting minerals, which may be dependent on temperature or other factors. Trace element concentrations in galena and their grain-scale distributions may also have potential in the identification of spatial and/or temporal trends within individual metallogenic belts, and as markers of ore formation processes in deposits that have undergone superimposed metamorphism and deformation. Galena trace element geochemistry may also display potential to be used as a trace/minor element vector approach in mineral exploration, notably for recognition of proximal-to-distal trends within a given ore system.
Abstract
Q-switch Nd: YAG laser of wavelengths 235nm and 1,460nm with energy in the range 0.2 J to 1J and 1Hz repetition rate was employed to synthesis Ag/Au (core/shell) nanoparticles (NPs) using ...pulse laser ablation in water. In this synthesis, initially the silver nano-colloid prepared via ablation target, this ablation related to Au target at various energies to creat Ag/Au NPs. Surface Plasmon Resonance (SPR), surface morphology and average particle size identified employing: UV-visible spectrophotometer, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorbance spectra of Ag NPs and Ag/Au NPs showed sharp and single peaks around 400nm and 410nm, respectively. The average diameter achieved for Ag/Au NPs were as 30nm and 25nm corresponding to 532nm and 1064nm, respectively. The TEM images showed that Ag/Au NPs possess a spherical shape, while the samples average size were in range from 20 to 30nm. There was an obvious increase in size during the use of 532nm laser. As for the effects of toxicity, results on human blood components showed that these nanoparticles have no effect on RBCs, WBCs and HB Therefore; these particles considered promising in the biological and medical applications.
Double-pulsed laser ablation with two targets and lasers in a background gas is a method to form nanoparticle complex. Effects of pulse delay between two lasers on plume expansion dynamics are ...discussed. The germanium and silicon targets were set parallel to each other and irradiated by two YAG lasers. The germanium target was irradiated followed by irradiation of the silicon target with delay time,
t
d
. We found that the expansion distance of delayed silicon plume is enhanced for 2 µs ≤
t
d
≤ 50 µs, compared to that when only the silicon target is irradiated. For
t
d
= 200 µs, the expansion distance of delayed silicon plume is similar to that when only the silicon target is irradiated. We discuss the expansion dynamics of the delayed silicon plume based on the effect of the density distribution induced by the primary germanium plume. Our results indicate that the effect of primary germanium plume remains up to about
t
d
= 50 µs, and it disappears by
t
d
= 200 µs.
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