High Dispersion Research Articles

Fractionation methods of eucalyptus kraft lignin for application in biorefinery

Abstract Kraft lignin has high dispersity and low reactivity. This study aimed to obtain more homogeneous and modified chemical fractions from the application of fractionation methods using organic solvents and acid precipitation. Organic solvents used were ethyl acetate, ethanol, methanol and acetone. The pHs tested were 9, 7, 5, 3 and 1, by adding hydrochloric acid. The fractions were characterized of acid-soluble and insoluble lignin, carbohydrates, ashes, elemental analysis and by Py-GC/MS. All fractions obtained in both fractionation methods showed higher carbon contents, higher purity and lower S/G ratio than the corresponding initial materials, characteristics that are very favorable for the application in biorefinery. Acetone-soluble (sequential) and pH 1 (one-step) precipitated fractions are the most promising for carbon fiber production. Fractions soluble in ethyl acetate (one-step) and insoluble at pH 3 and 1 (sequential) appear to be the most appropriate for applications that require good oxidative properties. The fractions soluble in ethanol (one-step), methanol (one-step), acetone (one-step) and precipitated at pH 9 (one-step) and pH 5 (sequential) are the ones that allow better chemical substitution in obtaining bioproducts. Fractions soluble in ethanol (sequential) and precipitated at pHs 5 and 1 (sequential) are not of commercial interest due to their low yield.

Enhancement of Mechanical and Chloride Binding Properties in Seawater Cement Using a Novel Carbon Nanomaterial

Chloride binding technology can effectively reduce the content of free chloride ions in seawater (used for cementitious materials), thereby extending the service life of seawater concrete structures. Currently, affordable and highly dispersed nanomaterials that can enhance the chloride binding capability of seawater cement are finite. This paper presents the first experimental study on N-doped graphene quantum dots (NGQDs), an innovative carbon nanomaterial with low price and high dispersibility, to strengthen the mechanical and chloride binding capabilities of seawater cement. Concretely, NGQDs are prepared through the hydrothermal process. The morphology and structure of NGQDs are measured by TEM, AFM, FTIR, and XPS. And the strengths and chloride binding performance of different specimens are analyzed by compressive/flexural strength tests and chloride adsorption equilibrium tests. The phase compositions of various specimens are analyzed by XRD, TGA/DTG, and SEM. The consequences indicate that the unique structure of the prepared NGQDs endows them with excellent water solubility and dispersibility. Notably, the introduction of NGQDs enhances the mechanical performance of seawater cement and 0.05 wt.% NGQDs have the greatest improvement effect. The compressive and flexural strengths of seawater cement containing 0.05 wt.% NGQDs increase by 8.21% and 25.77% after 28 d curing, respectively. Additionally, the seawater cement containing 0.2 wt.% NGQDs have the best chloride binding capability and are 41.08% higher than the blank group. More importantly, the chloride binding mechanism is that NGQDs accelerate seawater cement hydration, resulting in an increased formation of hydrated calcium silicate (C–S–H) and Friedel’s salt (Fs), thereby strengthening the physisorption and chemical combination of chloride. This study highlights an inexpensive and highly dispersible nanomaterial to heighten the stability of seawater concrete structures, opening up a new path for the better utilization of seawater resources.

The High Time Resolution Universe Pulsar Survey – XIX. A coherent GPU accelerated reprocessing and the discovery of 71 pulsars in the Southern Galactic plane

Abstract We have conducted a GPU accelerated reprocessing of ∼ 87 % of the archival data from the High Time Resolution Universe South Low Latitude (HTRU-S LowLat) pulsar survey by implementing a pulsar search pipeline that was previously used to reprocess the Parkes Multibeam pulsar survey (PMPS). We coherently searched the full 72-min observations of the survey with an acceleration search range up to $|50|\, \rm m\, s^{-2}$, which is most sensitive to binary pulsars experiencing nearly constant acceleration during 72 minutes of their orbital period. Here we report the discovery of 71 pulsars, including 6 millisecond pulsars (MSPs) of which five are in binary systems, and seven pulsars with very high dispersion measures (DM $>800 \, \rm pc \, cm^{-3}$). These pulsar discoveries largely arose by folding candidates to a much lower spectral signal-to-noise ratio than previous surveys, and exploiting the coherence of folding over the incoherent summing of the Fourier components to discover new pulsars as well as candidate classification techniques. We show that these pulsars could be fainter and on average more distant as compared to both the previously reported 100 HTRU-S LowLat pulsars and background pulsar population in the survey region. We have assessed the effectiveness of our search method and the overall pulsar yield of the survey. We show that through this reprocessing we have achieved the expected survey goals including the predicted number of pulsars in the survey region and discuss the major causes as to why these pulsars were missed in previous processings of the survey.

Filtering-free complex-valued DSB-16QAM generation for a 100 G direct detection optical interconnection.

In this Letter, a complex-valued double-sideband 16QAM (CV-DSB-16QAM) signaling scheme is proposed and experimentally demonstrated in a 100-Gb/s intensity modulation/direct detection (IM/DD) interconnection system. Unlike the conventional real-valued double-sideband (DSB) quadrature amplitude modulation (QAM) of relatively lower spectral efficiency (SE) and single-sideband (SSB) QAM relying on sharp-edged optical filtering, the CV-DSB-16QAM signal is generated by combining two independent sideband modulated QPSK signals using a single intensity modulator with an optical filtering-free profile, which also saves one photodiode and one analog-to-digital-converter compared with the twin-SSB scheme. Compared to typical pulse amplitude modulation or SSB schemes, the proposed approach offers a compelling alternative for complex-valued DD systems' evolution, particularly in scenarios with high SE demands and controllable chromatic dispersion. The experimental demonstration evaluates a 25-GBaud CV-DSB-16QAM signal over a 2-km standard single-mode fiber (SSMF), achieving a net bit rate of 100 Gb/s and occupying only a 25.1-GHz electrical bandwidth with a 4% guard band.

Trophic Structure and Isotopic Niche of Invaded Benthic Communities on Tropical Rocky Shores

When a species is introduced in a new location, it is common for it to establish itself when it finds favorable conditions in the receptor community with regard to interspecific interactions with native species. The azooxanthellate corals Tubastraea coccinea and Tubastraea tagusensis are invasive species introduced in the Caribbean Sea, the Gulf of Mexico, and the Brazilian Southwest Atlantic. They are successful competitors for space, have multiple reproductive modes, and have high larval dispersion and recruitment, but studies on food and trophic relationships of the genus Tubastraea are still scarce. In the present study, we used isotopic values of δ13C and δ15N to investigate trophic relationships in rocky shore communities invaded by T. tagusensis and T. coccinea corals under different oceanographic and anthropogenic contexts. Using metrics derived from the isotopic values, we show that invaded communities have a lower degree of trophic diversity, with species characterized by similar trophic ecologies while abiotic factors seem to contribute to the biotic resistance of communities exposed to invasion events. Tubastraea spp. occupy a niche space similar to that occupied by the native community of suspension feeders, sharing resources already consumed by the receptor community, which makes invading corals successful competitors for food.

Impact of replacing dune sand with ground date palm on the performance of cement mortar: dispersion analysis

This study investigates the effects of substituting dune sand with ground date palm at varying proportions of 0.5% to 2% on the mechanical and thermal properties of cement mortar. The findings indicate that this substitution enhances both the thermal and mechanical performance of the mortar, thereby improving its insulation capabilities. Notably, significant variations in compressive strength are observed, particularly at an early age of 7 days, with a reduction in variability as the mortar matures. Additionally, a high dispersion in measurement results is recorded. The application of the Weibull model facilitates the quantification of this variability and the assessment of material reliability, emphasizing the necessity of considering these fluctuations in the evaluation of sustainable construction materials. This approach not only underscores the potential of utilizing ecological resources but also paves the way for innovative practices in the construction sector. Overall, the study highlights the promising implications of incorporating alternative materials for enhancing the performance and sustainability of cement-based composites.

Fundamental Thermodynamic Aspects for the Effective Dispersion of Carbon Nanotubes and Improve Performance Grade of Bitumen

The application of carbon nanotubes to enhance bitumen properties is relevant due to the need to increase the durability of asphalt concrete pavements and reduce maintenance costs. Key areas requiring further study include the processes during ultrasonic dispersion, the selection of the optimal medium, and the stability of the resulting dispersions. This study examines dispersions containing multi-walled carbon nanotubes (MWCNTs) Taunit M (from 5·10−4 to 5·10−2%) and various hydrocarbon plasticizers. For the first time, the change in Gibbs free energy, enthalpy (interaction energy), and mixing and disordering entropy was calculated based on experimental data (surface tension, average cubic diameter of MWCNTs, molecular mass, etc.). The data were compared with the storage stability of polymer-modified binders (PMBs). It was found that mixing entropy plays a key role in forming thermodynamically stable dispersions, while the contribution of disordering entropy is minimal. High dispersion enthalpy of MWCNTs can reduce dispersion stability at high concentrations despite entropy growth. Systems with selective purification extracts showed the best PMB stability despite thermodynamic instability. The property changes after 3 days at 180 °C were no more than 5%. This suggests structural changes from component interactions are critical, highlighting the need for an integrated approach considering both thermodynamic and macroscopic properties.

On the catalytic nature of nitrided NiMo/γ-Al2O3 catalysts for dry reforming of methane

Nitrogen and phosphorus are one of the most common Group 15 elements. The chemistry of nitrogen and phosphorus is very important in the field of catalysis. Three types of nitride containing NiMo/γ-Al2O3 catalysts were synthesized using different loading-nitriding sequences and oxide precursor types for dry reforming of methane (DRM). The active components (Ni2Mo3N and Ni/Mo2N) firstly reacted with CO2, transforming into NiO and MoO2. They were then carburized with CH4 to produce Ni/Mo2C during the DRM process. From that point on, a redox cycle, viz. NiO/MoO2 ⇆ Ni/Mo2C, occurred during the DRM reaction. The low activity of nitriding-first NiMo nitride catalyst can be attributed to bulk oxidation. The observed gradual decline in performance of loading-first Ni/Mo nitride catalyst was due to coking. Noticeably, the loading-first NiMo nitride catalyst can demonstrate superiority in both activity and resistance to coking, which was due to its strong metal–Al2O3 interaction and high metal dispersion.

Polyol-Intermediated Facile Synthesis of B5-Site-Rich Ru-Based Nanocatalysts for COx-Free Hydrogen Production via Ammonia Decomposition.

Herein, a B5-site-rich Ru/MgAl2O4 nanocatalyst for the production of COx-free hydrogen from ammonia (NH3) is synthesized using the polyol method. The polyol method enables size-sensitive Ru-nanoparticle growth and controlled B5-site formation on the catalyst by tuning the carbon-chain length of the polyol solvent used, obviating the use of a separate stabilizer and enhancing electron donation from Ru (with a high surface electron density) and π-back bonding. The Ru/MgAl2O4 (BG) catalyst synthesized using butylene glycol (a long-carbon-chain solvent) contains 2.5nm Ru particles uniformly dispersed on its surface and abundant B5 sites at (0 0 2)/(0 1 1). Moreover, the Ru/MgAl2O4 (BG) catalyst exhibits lower activation energy (48.9kJmol-1) and higher H2 formation rate (565-1,236mmol gcat -1 h-1 at 350-450°C and a weight hourly space velocity of 30,000mL gcat -1 h-1) during the NH3 decomposition reaction than catalysts with a similar Ru particle size and high metal dispersion synthesized by the impregnation and deposition-precipitation methods. This high performance is possibly because the abundant electron-donating B5 sites on the catalyst surface accelerate the recombination-desorption of N2, which is the rate-determining step of the NH3 decomposition reaction at low temperatures. Thus, this study facilitates clean hydrogen production.

Facile and continuous synthesis of highly dispersed α-MoC1-x nanoparticles via thermal plasma method for higher alcohols synthesis from syngas

The metastable phase molybdenum carbide-based (α-MoC1-x) catalysts stand out as a class of the most promising representatives among the non-sulfide catalysts for the synthesis of higher alcohols (HAS) from syngas (CO/H2) due to their noble metal-like characteristics, resistance to coking, sulfur tolerance and weak C–O bond dissociation. However, the synthesis of α-MoC1-x commonly involves temperature-programmed ammonification and carburization (TPAC) or the consumption of noble metals. The α-MoC1-x prepared by TPAC usually exhibited large particle size, low dispersion and poor catalytic performance. Herein, we developed a facile and continuous thermal plasma method for synthesizing nanosized α-MoC1-x, which was highly dispersed on amorphous carbon (α-MoC1-x/C-Pla). Compared with the α-MoC1-x prepared by TPAC method (α-MoC1-x-TPAC), the α-MoC1-x/C-Pla catalyst exhibited higher CO conversion and excellent stability. The high dispersion and reactant adsorption/desorption capacity of α-MoC1-x/C-Pla contributed to its high catalytic activity, while the anti-aggregation property of the nanosized α-MoC1-x in α-MoC1-x/C-Pla conferred the high stability for the α-MoC1-x/C-Pla catalyst.

Salt template-assisted polymer tethering strategy to achieve high dispersed cobalt single atoms/clusters on porous carbon catalysts for effective Fenton-like reactions

The exploration of the synthesis of porous carbon-supported metal nanocatalysts with high metal loading and dispersion for the development of heterogenous catalysts is important. However, this remains a challenging subject. In this paper, a salt template-assisted polymer tethering strategy was proposed to prepare Co single atom and ultrafine cluster anchored on porous carbon (Co-NPC) with a high-loading of 16.9wt%, thereby exposing high density of reaction sites. The obtained Co-NPC catalyst exhibited excellent catalytic performance for almost 100% degradation of bisphenol A (BPA) within 20min, which is much faster than the CoSA-NPC catalyst with only single atom sites and Co-NC without salt template added. Radical quenching experiments and electron paramagnetic resonance tests verified that both the nonradical oxidation pathway by 1O2, the electron transfer and radical oxidation pathway by •OH, SO4•- appeared during the degradation process. After 3 cycles, the removal rate of BPA did not decrease significantly. The fixed bed experiment revealed that Co-NPC could realize the continuous degradation of methylene blue (MB) with almost 100% degradation efficiency. This research indicated that the strategy by pyrolyzing metal coordinated polymer is a potential method for the synthesis of high metal loading catalyst at gram scale, meeting the requirement of practical applications.

Rapid on-site colorimetric detection of Arsenic(V) by NH2-MIL-88(Fe) nanozymes-based Ultraviolet-visible spectroscopic and smartphone-assisted sensing platforms

BackgroundBecause arsenate (As(V)) is a highly toxic pollutant, timely on-site monitoring of its concentration is crucial for mitigating potential environmental and health hazards. Traditional on-site detection methods for As(V) often face limitations of long response time and low sensitivity. Nanozymes are nanomaterials that exhibit enzyme-like catalytic activity. Nanozyme-based colorimetric detection can amplify signals and improve detection sensitivity by catalytically converting a minimal substrate quantity into a substantial amount. However, current nanozymes-based As(V) detection methods still suffer from prolonged response time and the lack of convenient detection tools. ResultsWe develop a rapid and sensitive strategy for on-site colorimetric As(V) detection using a metal-organic framework (MOF) nanozyme, NH2-MIL-88(Fe). NH2-MIL-88(Fe) featured abundant Fe unsaturated metal centers (UMCs) and ordered porous structure, exhibiting excellent peroxidase-like activity, rapid As(V) adsorption, and high water dispersity. Fe UMCs efficiently catalyzed the oxidization of colorless tetramethylbenzidine (TMB) to blue oxTMB in the presence of H2O2. As(V) selectively inhibited this activity, reducing Ultraviolet-visible (UV-vis) absorption at 650 nm and fading the solution color. Mechanistically, As(V) interacted with Fe UMCs through As-O-Fe bonds, impeding Fe3+ reduction and Fe2+ catalytic ability, reducing •OH production. Under optimized conditions, As(V) was detected within 15 minutes, with detection limits of 2.78 μg•L-1 via UV-vis and 13.56 μg•L-1 via smartphone-assisted platform, covering a linear range of 5.00 - 600.00 μg•L-1. Additionally, NH2-MIL-88(Fe) was incorporated into an agarose hydrogel to create a portable composite for smartphone-based colorimetric analysis As(V). Significance and noveltyThis study addresses the existing issues of nanozyme-based As(V) sensors, elucidates the molecular mechanism by which As(V) affects NH2-MIL-88(Fe) nanozymes activity, and confirms the precision and accuracy of the established method in spiked river samples. Our rapid, sensitive, and facile approach offers a practical and efficient solution for on-site As(V) detection, facilitating swift intelligent risk identification and effective pollution prevention and remediation.

High drug-loaded amorphous solid dispersions of a poor glass forming drug: The impact of polymer type and cooling rate on amorphous drug behaviour.

Enhancing the aqueous solubility via amorphization of crystalline poor glass-forming drugs represents a challenge, particularly when drug dosing is high. In such scenarios, there is often a need for high polymer loadings leading to an increase in the dosage form mass and less patient acceptability. This work investigated the role that polymer type and after-melt cooling rate had upon the amorphicity of solid dispersions (SDs) containing high levels of naproxen and three commonly used polymeric excipients: Eudragit® EPO, Kollidon® VA64, and Soluplus®. Using a combination of thermogravimetry, conventional and fast-scan DSC, oscillatory rheology, in silico Hansen solubility parameter computation, FTIR, and PXRD, we have shown that amorphicity could be affected by the cooling rate with the specific polymer type and amount playing a significant role in the degree of this impact. The amorphous drug content, evident at higher cooling rates, was found to be dependent on drug-polymer interaction and polymer melt viscosity. Higher polymer concentration and faster cooling produced less melt crystallization upon cooling, which was attributed to a shift in nucleation to lower temperatures where it could be inhibited by polymer matrix viscosity. Amorphous drug content, which contained drug nuclei, was evidenced by cold crystallization upon reheating. After 4 weeks of 'gentle' storage, cold crystallization increased if nucleation was the dominant process, whereas cold crystallization decreased if crystal growth prevailed. Storage at elevated temperature and humidity resulted in the absence of cold crystallization, and increased melt crystallisation. Thus, faster cooling could serve as an additional tool to improve amorphous yield and stability of high drug-loaded SDs, however, intermolecular polymer-drug interaction, melt viscosity of the drug-polymer matrix, and storage conditions are of critical importance to achieve this goal.

High-performance bio-based foam from agricultural waste luffa seed oil polyols

The present study aimed to develop eco-friendly polyurethane viscoelastic foam (PVF) with enhanced tear strength while preserving softness, comfort, and safety by utilizing bio-based polyols derived from luffa seed oil (LSO). Two types of bio-based polyols (PLSO-D and PLSO-M) were synthesized through the epoxidation process using diethylene glycol (DEG) and methanol (MeOH), respectively, for the production of LSO-based polyurethane viscoelastic foams (LSO-PVFs). The analyses revealed that these polyols exhibited high dispersion, appropriate hydroxyl values, and contained by-products such as oligomeric esters of fatty acids that facilitated physical and chemical crosslinking. LSO-PVFs demonstrated a uniform and fine cell structure with abundant open-cells, thick cell walls (55.5–76.6µm), and high apparent density (48.7–50.7kg/m3). Moreover, they exhibited enhanced tensile and tear strength (increasing up to 200% compared to petroleum-based PVFs), lower water absorption, excellent mildew resistance at 10% PLSO substitution. Additionally, these factors endowed LSO-PVFs with low indentation hardness and good bottom support performance, characterized by a compressive deflection coefficient of 2.30–3.54. This approach presents a sustainable alternative for foam production that offers comfort, durability while promoting the value-added utilization of agricultural waste.

Hydrotalcite-derived well-dispersed and thermally stable cobalt nanoparticle catalyst for ammonia decomposition

Ammonia is a carbon-free hydrogen carrier, and development of non-noble metal catalyst to decompose ammonia into hydrogen is desirable for practical applications. However, the metal catalyst is challenged by the sintering of metal particles under high-temperature reaction conditions. In this study, a series of Li-, Al-, and Co-containing hydrotalcite-like compounds (HTlc) were synthesized by co-precipitation and used as precursors to prepare well-dispersed and thermally stable Co nanoparticle catalysts for ammonia decomposition. The obtained precursors and catalysts were characterized by means of X-ray powder diffraction (XRD), temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and so on. All of the precursors formed hydrotalcite-like phase, which consisted of Li–Al–(Co) HTlc and/or Co–Al HTlc dependent on the Co content. Upon calcination at 500 °C, HTlc decomposed into an Al-substituted Co3O4 spinel oxide, as confirmed by two distinctly separated reduction steps in H2-TPR. Following reduction at 700 °C, well-dispersed Co metal nanoparticles with an average particle size of ∼9.2–12.4 nm were obtained. It was suggested that the incorporation of Al3+ into Co3O4 led to a strong interaction between cobalt and aluminum, which suppressed the crystal growth of Co3O4 and the sintering of Co metal during the thermal treatments, resulting in good Co dispersion. The optimal LiAlCo(1.5) catalyst showed superior activity than that prepared by impregnation method, giving almost complete conversion of ammonia at 575 °C under a space velocity of 5,000 mL gcat–1 h–1. More importantly, this catalyst maintained stable activity at 625 °C for 100 h, exhibiting high stability and sintering resistance. The good catalytic performance was attributed to the high Co metal dispersion and strong metal–support interaction benefiting from the uniform distribution of cobalt in the HTlc precursor. These results demonstrate the applicability of HTlc to the preparation of metal catalysts with improved dispersion and thermal stability.

Collagen Hydrogel Loaded With 9-cisRA-Lip Is an Option for Treatment of Secondary Lymphedema after Surgery.

Background: Secondary upper limb lymphedema is easy to occur after breast cancer surgery, for which treatment is limited. 9-cis-retinoic acid (9-cisRA) has been demonstrated to increase lymphangiogenesis without enhancing tumor metastasis but has the disadvantages of poor water solubility, easy decomposition in light, unstable to heat, and short half-life. Methods: Based on this, 9-cisRA-Lip with a particle size of roughly 143 nm and high dispersibility was prepared by thin-film dispersion method and verified by Malvern Laser Particle Size Analyzer and electron microscopy. Results: In vitro, 9-cisRA-Lip demonstrated good biosafety and tumor safety, promoting the proliferation of L929 cells while having no effect on 4T1 and Human Umbilical Vein Endothelial (HUVEC) cells. Compared with 9-cisRA, 9-cisRA-Lip was more effective at encouraging mouse lymphatic endothelial cell (SVEC4-10) migration, proliferation, and tube formation. In vivo, 9-cisRA-Lip-Gel showed good slow-release effect, mice treated with 9-cisRA-Lip-Gel one-time local injection had considerably less tail edema than the control group from day 9 to day 39 postsurgery (p < 0.05). This may be attributed to the greater capacity of 9-cisRA-Lip to enhance the phosphorylation of FGFR3 (Fibroblast Growth Factor Receptor 3) at Tyr 724. Conclusions: 9-cisRA-Lip-Gel presents a potential treatment option for lymphedema following surgery.

Transition metal ions-chelated COFs derived bifunctional oxygen catalysts for rechargeable Zn-air batteries

Improving energy conversion efficiency and battery cycle stability is an essential goal in energy conversion and storage, while a critical factor in achieving this goal is the design of effective bifunctional catalysts. The covalent organic framework is a new type of high molecular material that can be employed as an ideal template for quantitative chelate metal ions to synthesize highly efficient bifunctional catalysts with high dispersion metal active sites. In this work, the Fe2Ni1/NiFe2O4@NCG bifunctional catalysts are constructed by employing metal-chelated COFs and MA/GO mixture as primary precursors combined with a high-temperature pyrolysis strategy. COFs and MA serve as chelators and spacers to improve the dispersion of metal nanoparticles. The Fe2Ni1/NiFe2O4@NCG composite exhibits a large BET surface area and hierarchical structure with plentiful nanoparticles on the carbon layers. HRTEM proves the coexistence of FeNi and NiFe2O4. The optimal Fe2Ni1/NiFe2O4@NCG-800 composite shows satisfactory catalytic O2 performance, providing a half-wave potential of 0.857 V for ORR and an overpotential of 244 mV for OER. Meanwhile, DFT calculations prove that electron redistribution occurs at the interface between FeNi and NiFe2O4 after combination. The Fe2Ni1/NiFe2O4@NCG-based liquid and solid-state ZABs perform very well, exhibiting large specific capacities (796 mAh·g−1 for aqueous ZAB; 742 mAh·g−1 for solid-state ZAB) and stable charge-discharge cycle performance (300 h for aqueous ZAB; 180 h for solid-state ZAB).

Dynamical structures of optical solitons for highly dispersive perturbed NLSE with $$\beta $$-fractional derivatives and a sextic power-law refractive index using a novel approach

Dynamical structures of optical solitons for highly dispersive perturbed NLSE with $$\beta $$-fractional derivatives and a sextic power-law refractive index using a novel approach

Nanostructured Ceria‐Niobia Catalyst for Selective Synthesis of N‐benzylideneanilines

The shape and structure engineering of metal oxide nanomaterials are the potential strategies to optimize surface‐active sites with tunable selectivity for heterogeneous catalysis. This work reports the synthesis of two types of nanostructured CeO2‐Nb2O5 catalysts: (i) one‐pot hydrothermal synthesis of CeO2‐Nb2O5 (CeNb2O5‐HTS) and (ii) CeO2 impregnation on hydrothermally synthesized Nb2O5 nanorods (CeNb2O5‐WI) to elucidate the role of particle shape and CeO2 addition in the structure‐activity efficacy of Nb2O5 nanocatalyst for the selective oxidative C‐N coupling of benzyl alcohol with aniline to produce N‐benzylideneaniline (NBA). The characterization studies showed nanorod morphology of Nb2O5 and high dispersion of CeO2 on Nb2O5 nanorods in the CeNb2O5‐WI catalyst with strong acidic sites and more oxygen vacancies. Consequently, a significantly enhanced catalytic activity was achieved with CeNb2O5‐WI nanocatalyst in the coupling of benzyl alcohol and aniline with 96% yield to NBA, whereas 62% conversion of aniline with 92% selectivity to NBA was obtained with pure Nb2O5 nanorods. In contrast, the CeNb2O5‐HTS catalyst gave 37% conversion of aniline only. The versatile efficiency of the CeNb2O5‐WI nanocatalyst is showcased by synthesizing various functional NBA products. The CeNb2O5‐WI catalyst can be recycled 5 times without much variation in NBA selectivity by achieving reasonably good conversion of aniline.

Formation of monodispersed anatase TiO2 spheres from TiOSO4 for enhanced hydrogen evolution of TiO2/g-C3N4 photocatalysts

Monodispersed anatase TiO2 spheres were synthesized from TiOSO4 solution made from Ti-bearing blast furnace slags (TBFS) via the hydrothermal hydrolysis-calcination route. By simply increasing the solution acidity before the hydrolysis, 2–4 μm TiO2 aggregates formed by 30–50 nm primary particles convert to 200–400 nm monodispersed spheres. The key to dispersion is investigated: As the acidity rises, SO42- in solution is converted to HSO4-, which changes the SO42-/HSO4- species adsorbed on the primary particle surface. DFT calculations show that Ti-SO4-Ti bridges between the primary particles are more easily broken than Ti-HSO4-Ti, allowing for the dispersion of the primary particles. The reasons for the narrow size distribution were investigated: The high acidity and hydrothermal treatment enhance the dissolution-deposition of TiO2. The small primary particles dissolve quickly and increase the monomer concentration, which promotes the growth of monodispersed TiO2 spheres following the "size focusing" mode, leading to a narrow size distribution. Finally, TiO2/g-C3N4 photocatalysts were prepared based on the aggregated TiO2 and monodispersed TiO2 spheres. Due to the more surface oxygen vacancies and higher dispersion, the photocatalyst made from the monodispersed TiO2 spheres shows enhanced hydrogen evolution than the aggregated TiO2. The present results may provide insights into TiO2 sphere synthesis and TBFS recycling.