Ambient Atmosphere Research Articles

Iterative synthesis of multi-grid topological nanostructures based on a stepwise friedel-crafts reaction

Covalent C–C bonded macrocycle topologies have been attracting increasing attention owing to their structural diversity and various applications. However, the methods for constructing such structures are limited, with most relying on transition metal-catalysis or requiring stringent reaction conditions, highlighting the urgent need to explore innovative synthetic approaches. Hence, we report a stepwise Friedel-Crafts gridization catalyzed by BF3·Et2O under ambient conditions and air atmosphere for the synthesis of the multi-grid topological nanostructures 2G-AG (30% yield) and 3G-AG (8% yield). Furthermore, the non-planar and structurally more complex multi-grid topologies, 2G-AG and 3G-AG, exhibit stronger excimer emission. This study provides a novel method for designing and synthesizing complex macrocyclic topological nanostructures connected by covalent bonds and with optoelectronic functionality.

Diatom Biosilica Functionalised with Metabolically Deposited Cerium Oxide Nanoparticles.

This study introduces a novel approach to synthesising a three-dimensional (3D) micro-nanostructured amorphous biosilica. The biosilica is coated with cerium oxide nanoparticles obtained from laboratory-grown unicellular photosynthetic algae (diatoms) doped metabolically with cerium. This unique method utilises the ability of diatom cells to absorb cerium metabolically and deposit it on their silica exoskeleton as cerium oxide nanoparticles. The resulting composite (Ce-DBioSiO2) combines the unique structural and photonic properties of diatom biosilica (DBioSiO2) with the functionality of immobilised CeO2 nanoparticles. The kinetics of the cerium metabolic insertion by diatom cells and the physicochemical properties of the obtained composites were thoroughly investigated. The resulting Ce-DBioSiO2 composite exhibits intense Stokes fluorescence in the violet-blue region under ultraviolet (UV) irradiation and anti-Stokes intense violet and faint green emissions under the 800 nm near-infrared excitation with a xenon lamp at room temperature in an ambient atmosphere.

Reaction Atmosphere-Controlled Thermal Conversion of Ferrocene to Hematite and Cementite Nanomaterials-Structural and Spectroscopic Investigations.

Recently, we have reported the influence of various reaction atmospheres on the solid-state reaction kinetics of ferrocene, where oxalic acid dihydrate was used as a coprecursor. In this light, present study discusses on the nature of decomposed materials of the solid-state reactions of ferrocene in O2, air, and N2 atmospheres. The ambient and oxidative atmospheres caused the decomposition to yield pure hematite nanomaterials, whereas cementite nanomaterials along with α-Fe were obtained in N2 atmosphere. The obtained materials were mostly agglomerated. Elemental composition of each material was estimated. Using the absorbance data, the energy band gap values were estimated and the related electronic transitions from the observed absorption spectra were explored. Urbach energy was calculated for hematite, which described the role of defects in the decomposed materials. The nanostructures exhibited photoluminescence due to self-trapped states linked to their optical characteristics. Raman spectroscopy of hematite detected seven Raman modes, confirming the rhombohedral structure, whereas the D and G bands were visible in the Raman spectra for cementite. Thus, the reaction atmosphere significantly influenced the thermal decomposition of ferrocene and controls the type of nanomaterials obtained. Plausible reactions of the undergoing solid-state decomposition have been proposed.

Single-Crystal P2-Na0.67Mn0.67Ni0.33O2 Cathode Material with Improved Cycling Stability for Sodium-Ion Batteries.

Layered oxides constitute one of the most promising cathode materials classes for large-scale sodium-ion batteries because of their high specific capacity, scalable synthesis, and low cost. However, their practical use is limited by their low energy density, physicochemical instability, and poor cycling stability. Aiming to mitigate these shortcomings, in this work, we synthesized polycrystalline (PC) and single-crystal (SC) P2-type Na0.67-δMn0.67Ni0.33O2 (NMNO) cathode materials through a solid-state route and evaluated their physicochemical and electrochemical performance. The SC-NMNO cathode with a large mean primary particle size (D50) of 12.7 μm was found to exhibit high cycling stability leading to 47% higher capacity retention than PC-NMNO after 175 cycles at 1C rate in the potential window 4.2-1.5 V. This could be attributed to the effective mitigation of parasitic side reactions at the electrode-electrolyte interface and suppressed intergranular cracking induced by anisotropic volume changes. This is confirmed by the lower volume variation of SC-NMNO (ΔV ∼ 1.0%) compared to PC-NMNO (ΔV ∼ 1.4%) upon charging to 4.2 V. Additionally, the SC-NMNO cathode displayed slightly higher thermal stability compared to PC-NMNO. Both cathodes exhibited good chemical stability against air and water exposure, thus enabling material storage/handling in the ambient atmosphere as well as making them suitable for aqueous processing. In this regard, PC-NMNO was investigated with two low-cost aqueous binders, carboxymethyl cellulose, and sodium trimetaphosphate, which exhibited higher binding strength and displayed excellent electrochemical performance compared to PVDF, which could potentially lead to significant cost reduction in electrode manufacturing.

Laser-induced graphene formation on different wood species: Dependence of electronic performance on intrinsic features of certain types of wood

Conductive, 3D, porous graphene can be produced with a CO2 laser from a large variety of materials, including wood, at room temperature, and under inert atmosphere or after treatment for fire protection. Here, we investigated the suitability for direct conversion of 46 typical European and Asian woods into laser-induced graphene (LIG), without pre-treatment. The LIG was characterized by resistance measurements to determine if a conductive layer had formed, and via Raman spectroscopy. Here, we show, for the first time, that it is possible to produce LIG on certain woods under atmospheric conditions without additional fire protection treatment. We determined that the ability to produce LIG on untreated, natural wood under ambient atmosphere is favoured overall by a high density and a diffuse-porous xylem structure, as well as a high soluble lignin content. Some of these characteristics are similar to those required for high yields in char production. Problematic for the production of LIG-based electronics is the presence of pronounced growth rings, or other geometric wood features, with density variations, which can be reduced using specific cuts with minimized growth rings and absence of rays. This is the first time that untreated wood has been directly converted into LIG using a conventional CO2 laser and ambient atmosphere. Our results represent a further step towards the development of a new generation of sustainable electronics relying on natural materials.

The construction of Cs3MoxSbyBr9/BiVO4 S-scheme heterojunction photocatalyst for efficient photocatalytic N2 fixation

Synergistic nitrogen (N2) reduction with water (H2O) oxidation is meaningful but challenging owing to the inertness of the N2 molecule and the sluggish kinetics of H2O oxidation. Herein, a simutaneous-promotion strategy of redox capacities is presented for constructing a lead-free Cs3Sb2Br9-based S-scheme heterojunction, by decorating Mo-functionalized Cs3Sb2Br9 nanocrystals (Cs3MoxSbyBr9) on BiVO4 nanosheet through an in-situ plane-to-point growth manner. The Mo-functionalization for Cs3Sb2Br9 enables the regulation of the d-band center position, greatly improving surface reaction kinetics for N2 reduction. Furthermore, the construction of the S-scheme heterojunction enhances the driving force for H2O oxidation and spatial charge separation of photocatalysts. As anticipated, the resultant Cs3MoxSbyBr9/BiVO4 exhibits an excellent photocatalytic N2 reduction activity under ambient atmosphere, achieving ammonia (NH3) production at a rate of 300 ± 5 μmol g−1 h−1 under simulated sunlight illumination (100 mW cm−2), which is nearly 20-fold higher than that of pristine Cs3Sb2Br9.

Synthesis study of size-controlled rhenium nanoparticle systems using reverse micelle-based methodologies

In this study, rhenium nanoparticles were successfully synthesized with precise size control using a water-in-oil microemulsion method under an ambient atmosphere. Spectroscopic characterization using UV-Vis and ESI-MS techniques was used to study the stability of the rhenium(IV) precursor and verify its reduction into rhenium-based nanoparticles. The morphology and size of the rhenium nanoparticles were examined using HR-TEM. The results indicate formation of amorphous rhenium nanoparticles with an average size of 2.2 nm at a water-to-surfactant concentration ratio (W factor) of 10. These rhenium nanoparticles also have good size-stability compared to rhenium colloids generated in water alone. After one week, the particle diameter increased by only 0.6 nm with no evidence of aggregation. An investigation into the effect of various factors on the size and size distribution of the rhenium nanoparticles indicate that the W factor is the most influential parameter (among the considered factors) for size tuning, given that increases in W led to bigger and more polydisperse particles. Additionally, the microemulsion surfactant (AOT) protects the rhenium nanoparticles from their natural tendency to oxidize to perrhenate ion under an air atmosphere. However, a significant consideration in the use of AOT is the previously unreported presence of a chemical impurity which is able to reduce the rhenium(IV) precursor salt and generate rhenium nanoparticles within these microemulsion systems. Our investigation found that this impurity is the sulfite ion which is most likely introduced during manufacturing.

Efficient Copper‐Free Sonogashira Coupling in Water and under Ambient Atmosphere

AbstractSonogashira coupling is one of the cornerstone Palladium mediated cross coupling reactions, giving a direct and high yield access to symmetric and non‐symmetric alkynes with high tolerance of substituents. The method generally requires the use of CuI as a cocatalyst, an inert atmosphere to protect palladium catalyst, somewhat harsh conditions like prolonged heating and the use of organic solvents due to the hydrophobicity of reagents and products. Leveraging on the opportunities offered by micellar catalysis, we here present a general methodology to perform Sonogashira coupling in water, with moderate or no heating, under air, without copper co‐catalysts and at very low catalyst loading. The method offers the same generality and scope of organic solvents based couplings, but strongly improves sustainability while offering excellent yields.

Effective Carrier Lifetime in Ultrashort Pulse Laser Hyperdoped Silicon: Sulfur Concentration Dependence and Practical Limitations

Charge carrier lifetime is a crucial material parameter in optoelectronic devices and knowing the dominant recombination channels points the way for improvements. The effective carrier lifetime τeff of surface‐passivated hyperdoped (hSi) and nonhyperdoped “black” (bSi) silicon by quasi‐steady‐state photoconductance decay (QSSPC) measurements and its evolution upon controlled wet‐chemical etching are studied. Sample preparation involves the irradiation of Si by numerous ultrashort laser pulses either in SF6 for hSi or ambient atmosphere for bSi. Findings suggest that the hSi is composed of a double layer: 1) an amorphous resolidified top layer with about 92% of the total incorporated sulfur that accounts for the sub‐bandgap absorptance and 2) a crystalline layer underneath in which sulfur concentration tails off toward the Si substrate. The effective lifetime is deconstructed by a 1D simulation to quantify the impact of the local lifetime of the defect‐rich top layer, τtop. It is found that by the QSSPC method, a maximum τtop for 1) can be estimated. For 2), τtop between 2 and 8 ns is estimated. The bSi sample shows a faster lifetime recovery upon etching which suggests that in hSi samples purely laser‐induced defects are not limiting the carrier lifetime compared to sulfur‐related defects.

The growth and characterization of Au-catalyzed gallium oxide nanowires

Gallium oxide is a powerful and versatile wide band gap semiconductor, which has been gaining scientific interest in recent years due to its applications in power electronics. In this work, the growth of β-gallium oxide (Ga2O3) nanowires has been achieved by the vapor–solid–liquid method on silicon wafer, fused quartz, and gallium oxide thin-film substrates. In a chamber purged of ambient atmosphere, pure gallium was heated to produce gallium vapor, which was then oxidized by minute oxygen impurities in the backing gas to form gallium oxide nanowires on a substrate, inside a vertical tube furnace. On the silicon wafer substrates, β-Ga2O3 nanowires were observed to grow in a specific crystallographic direction via transmission electron microscopy. The resulting nanowires were highly faceted and had a unique polyhedral structure on the gold catalyst ‘cap’ of the nanowire. Time of growth and oxygen-level studies were conducted on nanowires grown on various substrates.Graphical abstract

Electrocatalytic properties of Ni–Cu structures fabricated by electrodeposition of Cu on Ni cones

Ni–Cu alloys are a suitable candidate as a catalyst in Hydrogen Evolution Reaction due to their catalytic performance and good stability. To enhance this activity more, the active surface area of the material should be enhanced. It is commonly achieved by the synthesis of metals and alloys in the form of nanostructures. In this work, Ni cones fabricated by the one-step method were applied as a substrate for the deposition of thin Cu layers. Then, these materials were annealed in an ambient atmosphere to obtain Ni–Cu structures. The investigation of changes in morphology and chemical composition, as well as roughness and wettability before and after the annealing process was performed. Moreover, the measurements of catalytic properties were carried out in 1 M NaOH. The values of the Tafel slope and the electrochemical active surface area were studied. The proposed method can be successfully applied to fabricate structures of other alloys for the desired properties.

Warming climate is helping human beings run faster, jump higher and throw farther through less dense air

Understanding both positive and negative impacts of climate change is essential for comprehensively assessing and well adapting to the impacts of changing climate. Conventionally, climate warming is revealed to negatively impact human activities. Here, we reveal that human beings’ performance in anaerobic sports may benefit from climate warming. Using global weather observation and athletes’ performance datasets, we show that world-top athletes’ performances in nearly all athletics anaerobic events (i.e., sprints, jumps and throws) substantially improve as ambient temperature rises. For example, 100 m performance monotonically improves by 0.26 s as ambient temperature rises from 11.8° to 36.4 °C. Using Coupled Model Intercomparison Project Phase 6 datasets, we further show that global warming can substantially improve world-top athletes’ performance in eleven of the thirteen Olympics athletics anaerobic events by 0.27%–0.88% and 0.14–0.48% under high-emission and medium-emission scenarios, respectively, during 1979–2100. Among them, the improvements for 100 m are 0.59% (0.063 s) and 0.32% (0.034 s), respectively. Mechanism analysis shows that the warmed ambient atmosphere can improve competitors’ performance through expanding the air and thus reducing the air resistance to the competitors and throwing implements for hummer throw and all the sprints, hurdling and jumps. Quantitative analysis estimates that this thermodynamic process is essential for the impacts of warmed ambient atmosphere on the performances in these events as physiological processes are.

Impact of liming and maize residues on N2O and N2 fluxes in agricultural soils: an incubation study

AbstractSince it is known that nitrous oxide (N2O) production and consumption pathways are affected by soil pH, optimising the pH of agricultural soils can be an important approach to reduce N2O emissions. Because liming effects on N2O reduction had not been studied under ambient atmosphere and typical bulk density of arable soils, we conducted mesoscale incubation experiments with soils from two liming trials to investigate the impact of long-term pH management and fresh liming on N transformations and N2O production. Soils differed in texture and covered a range of pH levels (3.8–6.7), consisting of non-limed controls, long-term field-limed calcite and dolomite treatments, and freshly limed soils. Both soils were amended with 15N-labelled potassium nitrate (KNO3) and incubated with and without incorporated maize litter. Packed soil mesocosms were cycled through four phases of alternating temperatures and soil moistures for at least 40 days. Emissions of N2O and dinitrogen (N2) as well as the product ratio of denitrification N2O/(N2O + N2), referred to as N2Oi were measured with the 15N gas flux method in N2-reduced atmosphere. Emissions of N2O increased in response to typical denitrifying conditions (high moisture and presence of litter). Increased temperature and soil moisture stimulated microbial activity and triggered denitrification as judged from 15NO3− pool derived N2O + N2 emissions. Fresh liming increased denitrification in the sandy soil up to 3-fold but reduced denitrification in the loamy soil by 80%. N2Oi decreased throughout the incubation in response to fresh liming from 0.5–0.8 to 0.3–0.4, while field-limed soils had smaller N2Oi (0.1–0.3) than unlimed controls (0.9) irrespective of incubation conditions. Our study shows that the denitrification response (i.e., N2O + N2 production) to liming is soil dependent, whereas liming effects on N2Oi are consistent for both long- and short-term pH management. This extends previous results from anoxic slurry incubation studies by showing that soil pH management by liming has a good mitigation potential for agricultural N2O emissions from denitrification under wet conditions outside of cropping season.

Boosting the Carrier Lifetime and Optical Activity of CsPbX3 Nanocrystals through Aromatic Ligand Passivation.

Ligand engineering is crucial for tuning the structural and optoelectronic properties of perovskite nanocrystals (NCs), which also improves their stability. In contrast to the typically used long-chain alkylamine ligands, we successfully introduced an aromatic 1-(p-tolyl)ethylamine (PTEA) ligand to synthesize the CsPbX3 (X = Br or I) NCs. The CsPbI3 and CsPbBr3 NCs demonstrated long carrier lifetimes of ∼877 and 49 ns, respectively, as well as high photoluminescence quantum yields (PLQYs) of ∼99% and 95%, respectively. Furthermore, such NCs realized excellent long-term stability in an ambient atmosphere without obvious degradation over one month. All of these properties were better than the properties of NCs coated with the conventional alkylamine ligands. The high performance of these NCs was discussed with the effective surface passivation by PTEA. Our finding suggests a facile and effective ligand (PTEA) for modulating perovskites, achieving enhancement of both the carrier lifetime and the PLQY.

Decoding the oxidation mechanism of Zircaloy-4 via in situ synchrotron X-ray diffraction and computational elucidation

Comprehensive understanding of the oxidation behavior of Zr alloys, a vital cladding material in nuclear power plants, is essential for developing improved materials and enhancing the safety and performance of nuclear systems. Herein, the bulk oxidation behavior in ambient air atmosphere of Zircaloy-4 were revisited through in situ synchrotron X-ray diffraction and DFT computation. The results reveal the phase transition sequences at a representative 900 °C oxidation temperature: hcp Zr recrystallizes rapidly and then transforms into bcc Zr while reaching the α+β transus, followed by speedy appearance of textured tetragonal (t-)ZrO2, monoclinic (m-)ZrO2 and ZrN that consume oxygen and nitrogen. Continuous air ingress favors t-ZrO2 and m-ZrO2 dominance, accompanied by re-oxidation of ZrN into t-ZrO2 due to its low thermodynamic stability revealed by experiment-informed DFT calculation and low oxygen activity at the oxide-metal interface. Ensemble-averaged lattice volume expansions during phase transitions have been quantified. This expansion-induced compressive stress promotes the presence of a significant fraction of t-ZrO2 at elevated temperature that eventually transforms into m-ZrO2 during cooling.

Perylene-Based columnar liquid Crystal: Revealing resistive switching for nonvolatile memory devices

Perylene-based columnar liquid crystal (LC) devices exhibit resistive switching (RS), clearly identified on cyclic J-V curve hysteresis, stable for several cycles. Trap-controlled SCLC conduction is responsible for the charge transport in the active layer, where the “set” and “reset” processes occur. The incorporation of ZnO@SiO2 quantum dots significantly enhances the RS response. The distinguishing result presented here is the ability to write-read-erase-read, controlling the “on” and “off” states by applying an external electric field, which allows to store and read information multiple times. An endurance of nearly one order of magnitude between the low and high RS states was determined over 50 consecutive cycles. The device proved to be resilient, preserving the resistive switching effect and memory capacity even after one year maintained at room temperature and ambient atmosphere. DFT calculations indicate a conduction mechanism based on reversible reductions of the perylene LC molecules. This article highlights the ability of LCs to store and process information via their resistivity, with potential for low-cost production and large-area nonvolatile printed organic memories.

Bright cyan emission from Eu-Doped borosilicate glasses by optimizing reduction of Eu3+ to Eu2+ in ambient atmosphere

Although substantial strides have been made in exploring the blue and red emissions of amorphous glass under near-ultraviolet excitation for LEDs purpose, the lack of the cyan emission heavily hinders the full spectra LED towards high-quality application. Addressing this cyan gap in white-light LED technology calls for the doping of Eu2+ as the doping center for its highly efficient luminescence. However, Eu3+ as an oxidation state of europium ions poses a critical challenge in effectively reducing to its reduction state. A popular method for reduction involves using mixed gases such as N2/H2 or CO gases in a reaction container, yet this approach brings about environmental pollution and increases production costs. In this work, we proposed a novel strategy that bright cyan emission can be achieved in Eu-doped borosilicate glasses by optimizing reduction of Eu3+ to Eu2+ in ambient atmosphere. It is observed a gradual increase in the band emission intensity associated with the reduced Eu2+, accompanied with a concurrent decrease in the sharp peak intensity linked with Eu3+ with the growing Si3N4 content. The effect of both melting temperature and synthesis time on reduction effect on the reduction of Eu3+ to Eu2+ ions were also investigated. It is revealed that either longer synthesis times or higher melting temperatures diminished the efficient reduction of Eu3+ to Eu2+ ions during the first-melting. Expanding on the Si3N4 reduction method, we employed an external bamboo charcoal approach to produce Eu-doped borosilicate glass under various synthesis times during the secondary melting. The results show that longer synthesis times attributed to the reduction effect. Finally, the optimized cyan-emitting glass sample is featured with emission wavelength of 486 nm, a transmittance of 84 %, and a quantum yield of 37.97 %. All the significant results are paving the solid way to prepare cyan-emitting glasses in the future.

(Radio)Fluoro-iodination of Alkenes Enabled by a Hydrogen Bonding Donor Solvent.

We have developed a widely applicable (radio)fluoro-iodination of alkenes using readily available and easily handled KF (18F). The reactions exhibited high functional group tolerance and needed only an ambient atmosphere. Furthermore, the resulting product could be further functionalized with various nucleophiles.

Physicochemical Properties of 20 Ionic Liquids Prepared by the Carbonate-Based IL (CBILS) Process.

Ionic liquids (ILs) are an emerging materials' class with applications in areas such as energy storage, catalysis, and biomass dissolution and processing. Their physicochemical properties including surface tension, viscosity, density and their interplay between cation and anion chemistry are decisive in these applications. For many commercially available ILs, a full set of physicochemical data is not available. Here, we extend the knowledge base by providing physicochemical properties such as density (20 and 25 °C), refractive index (20 and 25 °C), surface tension (23 °C, including polar and dispersive components), and shear viscosity (ambient atmosphere, shear rate 1-200 s-1), for 20 commercial ILs. A correlation between the crystal volume, dispersive surface tension, and shear viscosity is introduced as a predictive tool, allowing for viscosity estimation. Systematic exploration of cation/anion alkyl side chain lengths reveals the impact on the IL's physicochemical attributes. Increasing the anion's headgroup decreases surface tension up to 35.7% and consequently shear viscosity. We further demonstrate that the dispersive part of the surface tension linearly correlates with the refractive index of the ionic liquid. While we provide additional physicochemical data, the screening and modeling efforts will contribute to better structure property predictions enabling faster progress in design and applications of ILs.

Role of coating techniques and low surface energy materials on long-term performance of superhydrophobic titanium

This study, for the first time, compares the performance of robust superhydrophobic (SHP) titanium (CP-Ti) surfaces developed by two different coating methods, (i) dip / immersion coating and (ii) spin coating, using two different low surface energy materials, (i) stearic acid and (ii) polydimethylsiloxane (PDMS). A facile two-step method for the fabrication of SHP Ti surface is followed, wherein the CP-Ti was first anodized and followed by the coating. The anodization of CP-Ti increased its surface roughness by developing a homogeneous coverage of randomly distributed micro-clusters, whose chemical composition was TiO2-xCly. Subsequent low surface energy organic coatings did not alter the surface morphology. The XPS analysis of stearic acid coated SHP Ti showed that the molecular structure of stearic acid is retained intact whereas the PDMS coated sample showed a partial modification of PDMS molecular structure with the presence of additional -[Si(O)2-O]- bonds apart from the inherent -[Si(CH3)2-O]- bonds. The water contact angle (WCA) and sliding angle (SA) values of SHP Ti were 170±5° and 6±2°, respectively. The SHP Ti showed excellent self-cleaning properties for both hydrophobic and hydrophilic contaminants. The adhesion test of the coatings showed the detachment of coating was within 5%. The coatings prepared by dip / immersion method retained their superhydrophobicity for an abrasion distance of about twice the length, (75±25 cm), due to a higher coating thickness, as compared to those obtained by the spin coating technique (40±20 cm). Further, the stearic acid-coated CP-Ti showed a better abrasion resistance while the stability of the PDMS-coated samples in different pH and Cl- environments was better. Nevertheless, both the stearic acid and PDMS-coated SHP CP-Ti samples showed excellent long-term stability against ambient atmosphere and UV exposure.