Simple Urea Research Articles

A Simple Urea Approach to N-Doped α-Mo2C with Enhanced Superconductivity

Abstract Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature (T c) of the parent superconducting materials. Here, a new simple urea approach is developed to synthesize the N-doped α-Mo2C. Benefiting from the simple urea method, a broad superconducting dome is found in the Mo2C1−x N x (0 ⩽ x ⩽ 0.49) compositions. X-ray diffraction results show that the structure of α-Mo2C remains unchanged and there is a variation of lattice parameters with nitrogen doping. Resistivity, magnetic susceptibility, and heat capacity measurement results confirm that T c was strongly increased from 2.68 K (x = 0) to 7.05 K (x = 0.49). First-principles calculations and our analysis indicate that increasing nitrogen doping leads to a rise in the density of states at the Fermi level and doping-induced phonon softening, which enhances electron–phonon coupling. This results in an increase in T c and a sharp rise in the upper critical field. Our findings provide a promising strategy for fabricating transition metal carbonitrides and provide a material platform for further study of the superconductivity of transition metal carbides.

Optical urea biosensor based on polyelectrolyte complex (PEC) pectin-chitosan membrane and anthocyanin from Catharanthus roseus L for a salivary simple urea detection

This work aimed to fabricate an optical urea biosensor using anthocyanins extracted from the Catharanthus roseus L as pH-sensitive substances and immobilised on a polyelectrolyte complex (PEC) pectin-chitosan membrane. The PEC pectin-chitosan/anthocyanin system's first layer is an optical pH sensor optimised in previous research. Then, the optimised pH sensor was further modified as an optical urea biosensor by immobilising the urease as the second layer. The biosensor relied on pH changes resulting from the reaction between urease and urea. The best sensitivity was observed at 0.09 mg urease, the optimum response was obtained at 0.03 M phosphate buffer solution of pH 7, and the stability was achieved after 5 min of measurement. The sensitivity reached at the widest dynamic range of urea concentration (1 × 10−10 to 1 × 10−1 M) was 0.0218 with a detection limit of 5.2 × 10−12 M. The optimised urea biosensor has repeatability with a percentage relative standard deviation of 10.2 %. The lifetime was evaluated for 30 days of measurements, where fluctuation in sensor sensitivity was observed.

Growth, Yield, and Agronomic Use Efficiency of Delayed Sown Wheat under Slow-Release Nitrogen Fertilizer and Seeding Rate

Delayed sowing of wheat is a common problem in Punjab that exacerbates serious yield loss. However, individual or combined applications of seed rate and slow-release nitrogen fertilizer significantly impacted their efficacy in improving crop growth and productivity. In this regard, the present study explored the potential of slow-release nitrogen fertilizers (control (CK), simple urea (SU), neem-coated urea (NCU), and sulfur-coated urea (SCU)) to improve the growth, yield, and physiological and biochemical attributes of delayed sown wheat with three seed rate [(100 kg ha−1 (S1), 125 kg ha−1 (S2), and 150 kg ha−1 (S3)]. The study was carried out at the Postgraduate Agricultural Research Station of the University of Agriculture Faisalabad in 2018–19 and 2019–20. The study findings revealed that the sulfur-coated urea performed better under S3 seed rate. Combining SCU with S3 significantly increased leaf area index by 0.99 cm2 and plant height by 8.24% compared to simple urea, maximum spikelets, and spike length by 3.9 and 3.8 cm, respectively. The SCU with S3 treatment also increased the biological yield by 43% and 41% and the grain yield by 46% in 2018–2019 and 2019–2020, respectively, compared to CK. Similarly, higher N contents in straw and grain were recorded in the interaction of SCU with S3 treatment. Likewise, the SCU with S3 treatment enhanced the physiological attributes, i.e., chlorophyll contents and transpiration rate, by 18% and 25%, respectively, and decreased internal CO2 by 25.5%, compared to CK. In conclusion, applying sulfur-coated urea with a seed rate of 150 kg ha−1 could be considered a potential strategy for improving the growth and productivity of delayed sown wheat.

Oxidative (3+3) Cycloaddition/Ring-Opening Reactions of Simple Urea Derivatives and N,N'-Cyclic Azomethine Imines to Construct 1,2,3,5-Tetrazine-4(1H)-one Derivatives.

A novel oxidative (3 + 3) cycloaddition/ring-opening reaction of N,N'-cyclic azomethine imines with the in situ generated diaza-oxylallyl cations from simple urea derivatives in the presence of base and PhI(OAc)2 has been developed. This transformation performs well over a broad substrate scope, which provides facile and rapid access to 1,2,3,5-tetrazine-4(1H)-one derivatives in good yields.

Synthesis of Complex Ureas with Brominated Heterocyclic Intermediates

AbstractHerein we present an efficient method to synthesize novel complex ureas from simple ureas, with potential pharmacological activity. First, 3‐methylindole ketones are protected via a two‐phase N‐tosylation reaction catalyzed by NBu4HSO4 as the PTC. Second, an NBS bromination of the terminal methyl group is performed with high selectivity and very good yields. Finally, complex novel and promising ureas are synthesized in 46 %–92 % yields using non‐base‐catalyzed substitution reactions with simple monosubstituted and disubstituted ureas. All products were easily purified through column chromatography and/or crystallization. The overall procedure produces very high yields and selectivity for bromination.

Selective modulation of La-site vacancies in La0.9Ca0.1MnO3 perovskites catalysts for toluene Oxidation: The role of oxygen species on the catalytic mechanism

Regulation of A-site vacancies is crucial to the redox reactions on ABO3 perovskites for VOCs catalytic oxidation. Herein, we reported the high toluene removal performance of La-defects and oxygen vacancies based La0.9Ca0.1MnO3 catalyst prepared by pyrolysis with simple urea modification. The 3-La0.9Ca0.1MnO3 had excellent catalytic activity and stability, and had good water resistance under the condition of 3%-10% H2O. Through analysis of various characterization, we found that the modification of urea made the A-site cation of La0.9Ca0.1MnO3 catalyst lack, which could effectively regulate the concentration of adsorbed oxygen and lattice oxygen in the perovskite catalyst, and enhanced the lattice oxygen participation in the catalytic oxidation of toluene. And the catalyst with abundant oxygen vacancies could promote the rapid degradation and complete oxidation of toluene. This study provided a simple method for the effective regulation of the defect site of perovskite catalyst, which was conducive to the promotion of industrial application.

Effective extraction of Pt(IV) as [PtCl6]2− from hydrochloric acid using a simple urea extractant

• 1-Butyl-3-(2-ethylhexyl)urea ( L ) selectively extracts Pt(IV) and Pd(II) over the other metals. • Pt(IV) is extracted as [PtCl 6 ] 2− via the exchange of H 2 O molecules. • [PtCl 6 ] 2− was extracted by L via coulombic interactions and hydrogen bonding. The conveniently prepared N , N ′-dialkylsubstituted urea derivative, 1-butyl-3-(2-ethylhexyl)urea ( L ), was prepared and elucidated with respect to its performance as an extractant for [PtCl 6 ] 2− from HCl solutions. L effectively extracts Pt(IV) and Pd(II) from 0.01 to 10 M HCl solutions with a high selectively over metal ions (Rh(III), Ir(III), Fe(III), Cu(II), Ni(II), Co(II), Zn(II), and Pb(II)) in the concentration range from 0.3 to 1.0 M HCl solutions. According to a slope analysis, the extraction equilibrium reaction of Pt(IV) by L was determined to be [PtCl 6 ] 2− aq. + 2 L org. + 2HCl aq. ↔ (PtCl 6 2− )·(H L + ) 2org. + 2Cl − aq. , which is a typical ion-pair reaction. Ultraviolet–visible measurements proved that Pt(IV) was extracted into the organic phase by L as a [PtCl 6 ] 2− salt. 195 Pt nuclear magnetic resonance (NMR) investigation suggests that the Pt(IV) extracted by L has slightly lower electron density on the Pt(IV) ion compared with the Pt(IV) species extracted by the conventional extractant tri- n -octylamine from HCl solution. Infrared and 1 H NMR spectroscopic measurements revealed a strong hydrogen bonding between the Cl − ligands of [PtCl 6 ] 2− and the N–H protons of L in the organic phase. Analysis of the water content in the organic phase, before and after the [PtCl 6 ] 2− extraction, shows that 0.9–2.6 water molecules are released from the organic phase as the result of [PtCl 6 ] 2− extraction from the aqueous into the organic phase by L .

Biochar and slow-releasing nitrogen fertilizers improved growth, nitrogen use, yield, and fiber quality of cotton under arid climatic conditions

The efficiency of nitrogenous fertilizers in South Asia is on a declining trajectory due to increased losses. Biochar (BC) and slow-releasing nitrogen fertilizers (SRNF) have been found to improve nitrogen use efficiency (NUE) in certain cases. However, field-scale studies to explore the potential of BC and SRNF in south Asian arid climate are lacking. Here we conducted a field experiment in the arid environment to demonstrate the response of BC and SRNF on cotton growth and yield quality. The treatments were comprised of two factors, (A) nitrogen sources, (i) simple urea, (ii)neem-coated urea, (iii)sulfur-coated urea, (iv) bacterial coated urea, and cotton stalks biochar impregnated with simple urea, and (B) nitrogen application rates, N1=160 kg ha-1, N2 = 120 kg ha-1, and N3 = 80 kg ha-1. Different SRNF differentially affected cotton growth, morphological and physiological attributes, and seed cotton yield (SCY). The bacterial coated urea at the highest rate of N application (160 kg ha-1) resulted in a higher net leaf photosynthetic rate (32.8 μmol m-2 s-1), leaf transpiration rate (8.10 mmol s-1), and stomatal conductance (0.502 mol m-2 s-1), while leaf area index (LAI), crop growth rate (CGR), and seed cotton yield (4513 kg ha-1) were increased by bacterial coated urea at 120 kg ha-1 than simple urea. However, low rate N application (80 kg ha-1) of bacterial coated urea showed higher nitrogen use efficiency (39.6 kg SCY kg-1 N). The fiber quality (fiber length, fiber strength, ginning outturn, fiber index, and seed index) was also increased with the high N application rates than N2 and N3 application. To summarize, the bacterial coated urea with recommended N (160 kg ha-1) and 75% of recommended N application (120 kg ha-1) may be recommended for farmers in the arid climatic conditions of Punjab to enhance the seed cotton yield, thereby reducing nitrogen losses.

The controllable magnetic properties of Fe3N nanoparticles synthesized by a simple urea route

The ε-Fe3N nanoparticles/C composite materials have been synthesized by ethylenediamine nitrided urea complexing precursors. The prepared ε-Fe3N NPs have regular spherical shape and small particle size. And the prepared ε-Fe3N NPs/C magnetic materials have significantly higher coercivity (604.4 Oe) and relatively lower saturation magnetization (21.1 emu/g) compared with the reported experimental and theoretical studies of ε-Fe3N. We consider that the surface properties and particle size of the prepared materials will result in the changes in magnetic properties.

Regioselective bromination of aryl ureas with Phenyliodine(III) diacetate and potassium bromide

An efficient regioselective and operationally simple urea bromination method utilizing PIDA and potassium bromide is reported. This protocol proved to be effective on a broad range of substituted ureas in acetone at room temperature, forming the p-brominated compounds in 44–86% yields.

A study of synergistic effect on oxygen reduction activity and capacitive performance of NiCo2O4/rGO hybrid catalyst for rechargeable metal-air batteries and supercapacitor applications

An effective non-precious bare NiCo2O4 (NCO) micro-shrubs and graphene (rGO) supported hybrid catalysts (NCO/rGO) were prepared by a simple urea assisted one-pot hydrothermal route. The authors were motivated to investigate an influence of synergistic effect between NCO nanoparticles and rGO sheets of freshly prepared hybrid catalysts (NCO/rGO) by adjusting the starting metal (nickel & cobalt nitrate hexahydrate) precursors, which has been denoted as 50 NCO/rGO, 100 NCO/rGO & 150 NCO/rGO in the present work. All the freshly prepared rGO, NCO and rGO supported hybrid catalysts with three different NCO mass loading samples were characterized through different characterization techniques such as XRD, FT-Raman, HR-SEM, HR-TEM, LSV, CV and galvanostatic charge/discharge studies, respectively. Among them, the rGO supported hybrid catalyst with lower amount of NCO mass loading (50 NCO/rGO) exhibits an outstanding oxygen reduction reaction (ORR) activity with lower onset potential, high limiting current density via. four-electron mechanism in an O2-saturated 0.1 M KOH electrolyte solution at room temperature. In addition, the specific capacitance of hybrid electrode is found to be 1305 F g-1 at a scan rate of 5 mV s−1 with 89% retention of cyclic stability even after 3000 cycles. The observed electrocatalytic activity and capacitive performances of an optimized hybrid sample (50 NCO/rGO) is strongly indicates an influence of better synergistic effect between NCO nanoparticles and rGO nanosheets. Hence, an optimized rGO supported hybrid catalyst (50 NCO/rGO) could be a promising electrocatalyst as well as hybrid electrode for metal-air batteries and supercapacitor applications, respectively.

Preparation of NiCoFe-hydroxide/polyaniline composite for enhanced-performance supercapacitors

Ternary NiCoFe layer hydroxides with different Ni/Co/Fe molar ratios were prepared using simple urea method. By finely tuning Ni/Co/Fe molar ratio, the optimized hydroxide (LDH2.0), a Ni/Co/Fe molar ratio of 2.0/1.0/1.0, provided high specific capacitance (408 F g−1 at 2.0 A g−1) and good stability (90.9% retention over 1000 cycles) due to maximum crystallinity (91.35% crystallinity) and specific surface area (160 m2 g−1). In order to further improve the electrochemical performances, the LDH2.0 was made into a composite (LDH/PANI) with polyaniline (PANI) via in situ polymerization of aniline monomer. The LDH/PANI composite had a much higher specific capacitance (717 F g−1 at 2.0 A g−1) compared with the LDH2.0, and a significant improvement of cycleability (84.7% retention over 1000 cycles). The results indicated that the LDH/PANI had a synergistic effect of both components due to the complementary properties, which guaranteed a good electric contact and consequently increased the specific capacitance. These provided a new approach for designing organic-inorganic composite materials with potential application in supercapacitors.

CO2 Capture via Crystalline Hydrogen-Bonded Bicarbonate Dimers

Summary Limiting global temperature rises is increasingly dependent on the development of energy-efficient carbon-capture methods. Here, we report a simple CO2-separation cycle using an aqueous bis(iminoguanidine) (BIG) sorbent that reacts with CO2 and crystallizes into an insoluble bicarbonate salt. X-ray diffraction analysis of the bicarbonate crystals revealed “anti-electrostatic” hydrogen-bonded (HCO3−)2 dimers, stabilized by guanidinium cations and water. Mild heating of the crystals releases the CO2 and regenerates the BIG sorbent quantitatively, thereby closing the CO2-separation cycle. Experimental and computational investigations support a CO2-release mechanism consisting of surface-initiated low-barrier proton transfer from guanidinium groups to bicarbonate anions with the formation of carbonic acid dimers, followed by CO2 and H2O release in the rate-limiting step, with a measured activation energy of 102 ± 12 kJ/mol. The minimum energy required for sorbent regeneration is 151.5 kJ/mol CO2, which is 24% lower than the regeneration energy of monoethanolamine, a benchmark industrial sorbent.

Synthesis of Hollow Spherical Zinc-Aluminum Hydrotalcite and Its Application as Zinc Anode Material

A simple urea hydrothermal method was used to synthesize hollow spherical zinc-aluminum hydrotalcites (ZAL-H) with the particle size of about 6.7–9.8 μm. The studies on different synthetic conditions have shown that the amount of urea and the type of solution system play important roles on the morphology and particle size of ZAL-H. X-ray diffraction (XRD) patterns indicate that the material has characteristic diffraction peaks of zinc-aluminum hydrotalcite. The specific surface area and pore size analysis (BET) indicate that the material has a uniform and narrow distribution of pore diameter of 3.682 nm and a specific surface area of 49.09 m2 g−1. As negative electrode material for zinc-nickel battery, the ZAL-H electrode exhibits a significantly enhanced discharge specific capacity compared to most previously reported electrodes based on zinc-aluminum hydroxides. The average discharge special capacity is 393.342 mAh g−1 during the whole charge/discharge process (1050 cycles), the discharge efficiency is up to 97.34%, and the capacity retention rate is as high as 95.37%. Therefore, the ZAL-H is an excellent electrode active material and can be potentially applied to the energy storage/conversion devices.

Simple Urea Immersion Enhanced Removal of Tetracycline from Water by Polystyrene Microspheres.

Antibiotics pose potential ecological risks in the water environment, necessitating their effective removal by reliable technologies. Adsorption is a conventional process to remove such chemicals from water without byproducts. However, finding cheap adsorbents with satisfactory performance is still a challenge. In this study, polystyrene microspheres (PSM) were enhanced to adsorb tetracycline by surface modification. Simple urea immersion was used to prepare urea-immersed PSM (UPSM), of which surface groups were characterized by instruments to confirm the effect of immersion. Tetracycline hydrochloride (TC) and doxycycline (DC) were used as typical adsorbates. The adsorptive isotherms were interpreted by Langmuir, Freundlich, and Tempkin models. After urea immersion, the maximum adsorption capacity of UPSM at 293 K and pH 6.8 increased about 30% and 60%, achieving 460 mg/g for TC and 430 mg/g for DC. The kinetic data were fitted by first-order and second-order kinetics and Weber–Morris models. The first-order rate constant for TC adsorption on UPSM was 0.41 /h, and for DC was 0.33 /h. The cyclic urea immersion enabled multilayer adsorption, which increased the adsorption capacities of TC on UPSM by two to three times. The adsorption mechanism was possibly determined by the molecular interaction including π–π forces, cation-π bonding, and hydrogen bonding. The simple surface modification was helpful in enhancing the removal of antibiotics from wastewater with similar structures.

A Fluorescent Ditopic Rotaxane Ion‐Pair Host

AbstractWe report a rotaxane based on a simple urea motif that binds Cl− selectively as a separated ion pair with H+ and reports the anion binding event through a fluorescence switch‐on response. The host selectively binds Cl− over more basic anions, which deprotonate the framework, and less basic anions, which bind more weakly. The mechanical bond also imparts size selectivity to the ditopic host.

A Fluorescent Ditopic Rotaxane Ion-Pair Host.

We report a rotaxane based on a simple urea motif that binds Cl− selectively as a separated ion pair with H+ and reports the anion binding event through a fluorescence switch‐on response. The host selectively binds Cl− over more basic anions, which deprotonate the framework, and less basic anions, which bind more weakly. The mechanical bond also imparts size selectivity to the ditopic host.

Covalent-bonding to irreducible SiO2 leads to high-loading and atomically dispersed metal catalysts

Being a suitable way for achieving the maximum efficiency of atoms, the atomically dispersed metals are playing an ever-increasingly important role in bridging heterogeneous and homogeneous catalysis. It is extremely challenging for dispersing metals in atomic-scales as the applicable high-loading catalysts for industry. The reducible and defective supports or metal surfaces are commonly chosen for anchoring the metals. We here report that atomically-dispersed but high-loading (15wt%) metals were achieved by covalent-bonding to irreducible SiO2 (though silanol groups) which is realized by a simple urea hydrolysis assistant hydrothermal-deposition method. The CuOSi bonding tailors the structural and electronic states of catalyst by maximum of atom efficiency and tuning electronic effects. The intrinsic performance of CO hydrogenation was thus boosted by one- to two- orders-of-magnitude in comparison with impregnated and precipitated catalysts. The choices of metals include Cu, Zn, Ni, Co and Mn, showing potentials for a category of applied materials.

Synthesis, characterization and electrical properties of mesoporous nanocrystalline CoFe2O4 as a negative electrode material for lithium battery applications

Mesoporous nanocrystalline cobalt ferrite (CoFe2O4) as a negative electrode material for lithium battery was prepared by using simple urea assisted modified citrate combustion process. Formation of pure crystalline phase and nanocrystallite size were respectively identified and calculated from the analysis of the observed X-ray diffractometer pattern of the CoFe2O4 sample. The formation of uniform mesoporous nanocrystalline architecture was confirmed from the observed FE-SEM images of the CoFe2O4 sample. Specific surface area obtained from BET analysis of the sample is found to be 38.369 m2 g−1. The delivered discharge capacity of the lithium ion battery, fabricated using prepared mesoporous nanocrystalline CoFe2O4, is found to be 484 mAh g−1 after 30 cycles at 0.1 C rate. The observed high discharge capacity may be due to the unique mesoporous nanocrystalline structure of the CoFe2O4 sample. Hence, the electrochemical results reveal that the mesoporous nanocrystalline CoFe2O4 could be a promising high capacity, negative electrode material for lithium ion batteries.

Anion binding consistency by influence of aromatic meta-disubstitution of a simple urea receptor: regular entrapment of hydrated halide and oxyanion clusters

Consistent recognition of asymmetric divalent sulphate, hydrated chloride and acetate along with fluoride induced bicarbonate within self-assembly of bis-urea receptor is observed.