Effective photocatalysts and their surface engineering are essential for the efficient conversion of solar energy into chemical energy in photocatalyzed organic transformations. Herein, we report an ...effective approach for structuring Pd nanoparticles (NPs) on exfoliated 2H-WS2 nanosheets (WS2/PdNPs), resulting in hybrids with extraordinary photocatalytic activity in Suzuki reactions under visible light. Pd NPs of different sizes and densities, which can modulate the photocatalytic activity of the as-prepared WS2/PdNPs, were effectively structured on the basal plane of 2H-WS2 nanosheets via a sonic wave-assisted nucleation method without any reductants at room temperature. As the size of Pd NPs on WS2/PdNPs increased, their photocatalytic activity in Suzuki reactions at room temperature increased substantially. In addition, it was found that protic organic solvents play a crucial role in activating WS2/PdNPs catalysts in photocatalyzed Suzuki reactions, although these solvents are generally considered much less effective than polar aprotic ones in the conventional Suzuki reactions promoted by heterogeneous Pd catalysts. A mechanistic investigation suggested that photogenerated holes are transferred to protic organic solvents, whereas photogenerated electrons are transferred to Pd NPs. This transfer makes the Pd NPs electron-rich and accelerates the rate-determining step, i.e., the oxidative addition of aryl halides under visible light. WS2/PdNPs showed the highest turnover frequency (1244 h–1) for photocatalyzed Suzuki reactions among previously reported photocatalysts.
Visible-light-driven photocatalysis has been emerging as an efficient and sustainable approach for chemical transformation in organic reactions, in which photostable and cost-effective ...photosensitizers are required to trigger and promote it. Monolayer WS2 nanosheets smaller than 120 nm were prepared by means of a modified liquid exfoliation method, and they showed strong photoluminescence in the visible range of the electromagnetic spectrum from 450 to 650 nm. These photoactive WS2 nanosheets were exploited as photocatalysts in the oxidative coupling reactions of various amines under visible-light irradiation. They showed excellent photocatalytic activity and reusability without the loss of their catalytic activity in the visible-light-driven oxidative coupling reactions of various amines. In addition, the mechanism responsible for WS2 nanosheet catalyzed imine production under visible-light irradiation was fully investigated.
Li-air batteries attract abundant attention in recent years with superior performance, and have largely replaced traditional methods of energy storage. The main objective of Li–air battery is to ...provide long-range electric-vehicles, while functioning as an environmentally friendly and compact energy storage solution. They offer the highest theoretical energy density (3500 Wh/kg), almost 20% higher than the ordinary Li-ion batteries. Nonetheless, Li-air batteries still face numerous issues, the most serious of which are high overpotential and parasitic reactions. Several redox mediators (RM) have been studied in order to reduce the high overpotential and the influence of side reactions. RM function in the electrolyte as soluble catalysts, limiting the formation of singlet oxygen while promoting the formation of discharge product Li2O2. This research primarily focuses on the optimization of Li-air cells with different redox mediators in conjunction with appropriate electrolyte, as a result reducing overpotential, parasitic byproducts and increasing efficiency. Under standard electrolytic conditions, ruthenocene exhibits high stability by completing 83 cycles, thus outperforming the other mediators being investigated. Further, di-tert-butyl-1,4-benzoquinone is more commonly used for discharge reaction and has been shown to increase the capacity of Li–O2 batteries by 80 times. This study reconfirms lithium bis(trifluoromethylsulfonyl) imide in tetraethyleneglycol dimethylether as the most stable electrolyte.
Display omitted
•LABs offer high energy density but pose overpotential and parasitic reactions.•Redox mediators or soluble catalysts are studied to reduce overpotential issues.•Ruthenocene is highly stable and outperforms all other mediators.•DBBQ is commonly used for discharge and increases the capacity of LABs 80 times.
We study the Fano interference from different phase transitions of Eu3+:YPO4 and Pr3+:YPO4 crystals through simultaneous detection of bright and dark states. For this study, we employed tetragonal ...(T), hexahedral (H), and (H + T)-phases of YPO4 crystals. The Fano interfering bright and dark states are classified based on dressed spontaneous parametric four-wave mixing, dressed multi-order fluorescence, and hybrid signal regimes. Further, the Fano interference between conti-nuous and discrete states can be controlled from partly-(constructive-destructive)-interference through a phase transition, nonlinear phase, and dressing. The (H + T)-phase Pr3+:YPO4 suggests more obvious Fano interference in contrast to T- or H-phase Pr3+:YPO4. We report that the Pr3+:YPO4 and Eu3+:YPO4 demonstrates the dressed multi-level- and dressed single-level Fano interference, respectively, with further three types of Fano interference that can be distinguished at different time delays. The experimental measurement agrees with theoretical simulations. Such results may be used for the design of new types of quantum electronic or spintronic devices such as Fano-transistors.
Recent developments propose renewed use of surface-modified nanoparticles (NPs) for enhanced oil recovery (EOR) due to improved stability and reduced porous media retention. The enhanced surface ...properties render the nanoparticles more suitable compared to bare nanoparticles, for increasing the displacement efficiency of waterflooding. However, the EOR mechanisms using NPs are still not well established. This work investigates the effect of in-situ surface-modified silica nanoparticles (SiO2 NPs) on interfacial tension (IFT) and wettability behavior as a prevailing oil recovery mechanism. For this purpose, the nanoparticles have been synthesized via a one-step sol-gel method using surface-modification agents, including Triton X-100 (non-ionic surfactant) and polyethylene glycol (polymer), and characterized using various techniques. These results exhibit the well-defined spherical particles, particularly in the presence of Triton X-100 (TX-100), with particle diameter between 13 to 27 nm. To this end, SiO2 nanofluids were formed by dispersing nanoparticles (0.05 wt.%, 0.075 wt.%, 0.1 wt.%, and 0.2 wt.%) in 3 wt.% NaCl to study the impact of surface functionalization on the stability of the nanoparticle suspension. The optimal stability conditions were obtained at 0.1 wt.% SiO2 NPs at a basic pH of 10 and 9.5 for TX-100/ SiO2 and PEG/SiO nanofluids, respectively. Finally, the surface-treated SiO2 nanoparticles were found to change the wettability of treated (oil-wet) surface into water-wet by altering the contact angle from 130° to 78° (in case of TX-100/SiO2) measured against glass surface representing carbonate reservoir rock. IFT results also reveal that the surfactant treatment greatly reduced the oil-water IFT by 30%, compared to other applied NPs. These experimental results suggest that the use of surface-modified SiO2 nanoparticles could facilitate the displacement efficiency by reducing IFT and altering the wettability of carbonate reservoir towards water-wet, which is attributed to more homogeneity and better dispersion of surface-treated silica NPs compared to bare-silica NPs.
Pseudo-successive ionic layer adsorption and reaction (p-SILAR) process is performed on TiO
2
nanoparticles for enhancing their visible light activity. Since p-SILAR is a facile process based on wet ...chemistry, it involves underutilization of ionic precursors which becomes even more adverse during the deposition of quantum dots having multi-cationic species in it. For example, copper zinc tin sulfide (CZTS) is deposited wet chemically by involving cationic precursors of Cu, Zn and Sn, respectively. At the end of the process, the left-over solutions are wasted owing to the decrease in purity and lowering of ionic concentrations those are hard to be traced. In this work, we have increased the photocatalytic response of TiO
2
under visible irradiation by depositing CZTS quantum dots (QDs) on it, while on the other hand we recovered SnO
2
and CZTS products (named as SnO
2
@p-SILAR and CZTS@p-SILAR, respectively) from the underutilized ionic precursors making process efficiency better. The SnO
2
particles were separated from Sn-precursor owing to their precipitation during p-SILAR, while CZTS was separately produced via simple physico-chemical control. All the materials, whether synthesized or salvaged, were applied as photocatalysts for degrading toxic Rhodamine B (RhB) dye under ultraviolet or visible light. Compared with negligible performance of TiO
2
(
k
C
~ 0.0011 min
−1
), p-SILAR synthesized TiO
2
–CZTS (
k
C
~ 0.01 min
−1
) and CZTS (
k
C
~ 0.0085 min
−1
) exhibited much higher pace in reaction that was credited to their higher absorbance of visible light.
In past decade, electrochemical energy storage gained undivided attention with the increase in electrical energy demand for the usage of new technology such as moveable electronics. Li-ion batteries ...(LIB) have been the most successful energy storage system with their long-life cycle and efficiency, lower energy density, and notable cost effectiveness with small-scale energy storage. However, with large-scale energy storage and for long duration, work still needs done to make LIB efficient on such a scale as well. Recently Li–air batteries have been suggested as potential energy storage systems that can provide the solution for large- and long-term electrical energy storage. The Li–air battery utilizes the catalyst-based redox reaction, and still, it is not applicable commercially due to low current density, poor life cycle, and energy efficiency. Generally, such problems are associated with the materials used as an electrocatalyst and on the selection of the electrolyte. Herein, we briefly review the current advancements in the field of electrocatalysts for Li–air batteries which hinders their improvement toward commercial applications, and this review also provides an outlook for future Li–air battery systems.
We reported the second- and third-order temporal interference of two non-degenerate pseudo-thermal sources in a nitrogen-vacancy center (NV
). The relationship between the indistinguishability of ...source and path alternatives is analyzed at low temperature. In this article, we demonstrate the switching between three-mode bunching and frequency beating effect controlled by the time offset and the frequency difference to realize optical demultiplexer. Our experimental results suggest the advanced technique achieves channel spacing and speed of the demultiplexer of about 96% and 17 ns, respectively. The proposed demultiplexer model will have potential applications in quantum computing and communication.
Rechargeable batteries have gained a lot of interests due to rising trend of electric vehicles to control greenhouse gases emissions. Among all type of rechargeable batteries, lithium air battery ...(LAB) provides an optimal solution, owing to its high specific energy of 11,140 Wh/kg comparable to that of gasoline 12,700 Wh/kg. However, LABs are not widely commercialized yet due to the reactivity of the lithium anode with the components of ambient air such as moisture and carbon dioxide. To address this challenge, it is important to understand the effects of moisture on the electrochemical performance of LAB. In this review, the effects of ambient air on the electrochemical performance of LAB have been discussed. The literature on the deterioration in the battery capacity and cyclability due to operation in ambient environment and degradation of lithium anode due to exothermic reaction between lithium and water is reviewed and explained. The effects of using oxygen-selective membrane (OSM) to block moisture and
CO
2
contamination has also been discussed, along with suitable materials that can act as OSM. It is concluded that the utilization of OSM can not only make the safer operation of LAB in ambient air but could also enhance the electrochemical performance of LAB. Future direction of the research work required to address the associated challenges is also provided.
PDF
