Nitrogen Sites Research Articles

Changes in plant architecture in Brazilian peppertree damaged by the biological control agent, Pseudophilothrips ichini (Hood) (Thysanoptera: Phlaeothripidae)

Plants may compensate for herbivory damage by reallocating resources and altering growth patterns, which may be further influenced by environmental variables like nutrient availability. We compared the impacts of fertilizer applications on the growth attributes of Brazilian peppertree before and after releasing Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae), an approved biological control agent. A garden plot containing 96–103 saplings was established at two research sites in Florida: one site with high background soil nitrogen and one with 1/4 the background soil nitrogen. Each plant was randomly assigned a permanent fertilizer supplement (24N-8P-16K) administered bimonthly: no fertilizer n = 69 (0 g/L), medium fertilizer n = 66 (0.8 g/L), or high fertilizer n = 66 (3.6 g/L). Thrips were released after 22 months and releases continued every 1–3 months. Plant growth attributes were collected approximately monthly from October 2017 to April 2021. Crown volume and height steadily increased at both plots, but greater rates of increase were observed for plants with higher supplemental fertilizer at the lower nitrogen site. Thrips had negligible impact on plant attributes at the high nitrogen site. In contrast, the density of stem tips at the low nitrogen site increased dramatically following thrips release and was greatest for plants with high supplemental fertilizer. Additionally, the percentage of dead tips quadrupled during the second year of thrips releases, but tip mortality was greatest for plants with medium supplemental fertilizer. Fertilized plants produced more unseasonal axillary vegetative buds after thrips attack at the low nitrogen site, providing new resources to sustain thrips numbers. Soil nitrogen levels at natural field sites may therefore impact thrips performance.

Catalytic reduction of nitro compounds with nano-silver supported by a microporous covalent-organic framework

Covalent-organic frameworks (COFs) with highly ordered porous structures have been widely applied in the field of catalysis and pollution treatment. In this work, a serial of Ag@TAPP-COF composites was successfully synthesized by using 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) and thieno [(Cao et al., 2019; Misra and Pandey, 2005) 3,23,2-b]thiophene-2,5-dicarboxaldehyde as monomers. The constructed composites were well characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and N2 adsorption-desorption technique. It is found that Ag@TAPP-COF composites showed high specific surface area and ordered micro pores with plenty of nitrogen and sulfur sites. With these structural advantages, Ag@TAPP-COF composites were developed as excellent and stable catalysts for the reduction of 4-NP. Among them, Ag10@TAPP-COF exhibited the highest catalytic activity with a rate constant of 3.44 s−1 g−1 and an activation energy of 16.2 kJ mol−1. Fascinatingly, Ag10@TAPP-COF can also catalyze the reduction of other kinds of nitro compounds. This work provides an effective method and potential materials for the reduction of nitro compounds.

Boosting the Catalytic Activity of Nitrogen Sites by Spin Polarization Engineering for Oxygen Reduction and Wide‐Temperature Ranged Quasi‐Solid Zn–Air Batteries

AbstractThe oxygen reduction reaction (ORR) is a crucial cathode reaction for developing quasi‐solid zinc–air batteries (QZABs) with high energy density. However, the activity and stability of catalysts under extreme conditions have not been fully explore. Herein, a series of systematic experiments and theoretical calculations have been conducted to investigate the potential of introducing FexCoy into nitrogen (N)‐doped porous carbon (NPC) via one‐step pyrolysis to form a core–shell structure that can effectively enhance the activity of the catalysts, particularly at low temperatures. Due to the difference in the work function of 5.12, 5.11, and 5.06 eV, the spin‐polarized charge is transferred to the pyridinic‐N site on the surface under the charge transfer. Consequently, the pyridinic‐N site on the surface exhibits varying degrees of magnetic moment 0.024 µB, which is crucial for forming OOH* and enhances ORR activity. The Fe5Co5@NPC catalyst is evaluated for QZABs at −40 °C and achieved a power density of up to 117.6 mW cm−2, which is only 18.7% lower than normal temperature, and a cycle life of up to 300 h. This study provides a means to realize the design of QZABs catalysts in extreme environments and explore their application potential.

Constructing copper-organic framework with exceptionally high volumetric working capacity for efficient methane storage

Extensive efforts have been devoted to developing novel porous structures for methane storage with high volumetric uptake and volumetric working capacity. In this study, a NbO-type copper–organic framework (CMOF-1) was designed and synthesized. Notably, the CMOF-1 posses suitable nanocages decorated with carboxylate groups and nitrogen sites, exhibiting a remarkable volumetric uptake of 260 cm3 cm−3 (at 65 bar/298 K) and a volumetric working capacity of 202 cm3 cm−3 (from 5 to 65 bar). These values are comparable to those of the benchmark material HKUST-1 (267 cm3 cm−3 and 190 cm3 cm−3) and exceed those of the structural analogue ZJU-5a (249 cm3 cm−3 and 188 cm3 cm−3) under the same conditions. The grand canonical Monte Carlo simulations and density functional theory calculations reveal that the high methane volumetric uptake might be contributed by the open CuII sites and nanocages with suitable sizes/shapes and functional sites, which can enforce strong gas-framework and gas–gas interactions. The methodology presented in this work should envision potential practical applications in methane storage and could be generalized to design other novel materials for the storage of other gases like hydrogen.

Carbonized eggshell membranes as highly active co-catalyst with Fe3+/persulfate for boosting degradation of carbamazepine by accelerating Fe3+/Fe2+ cycle

The sluggish Fe3+/Fe2+ cycle greatly limits the effectiveness of the Fe3+-induced persulfate (Fe3+/PS) system for degrading refractory organic pollutants. Coupling Fe3+/PS system with a co-catalyst is a promising strategy to solve this issue. Herein, we report a carbonized eggshell membrane (CESM) as a potential co-catalyst to efficiently drive Fe3+/PS oxidation. The promotion effect of the CESM on the Fe3+/Fe2+ cycle resulted in the improvement in the activity of the Fe3+/PS system to degrade carbamazepine (CBZ), with ∼100 % CBZ removal achieved with low doses of Fe3+ (1.0 mg/L) and PS (100 mg/L). Crucially, a pseudo-first-order rate constant of CESM/Fe3+/PS system was 18- and 28-times that of the Fe3+/PS and CESM/PS systems. Experimental and theoretical findings reveal that the phenolic –OH groups and carbon--center persistent free radicals in CESM are electron donors, while the nitrogen sites function as favorable Fe3+-adsorption sites. The electron transfer in CESM/Fe3+/PS system occurred between a CESM and an attached Fe3+, facilitating the generation of Fe2+ and thus contributing to the continuous activation of PS. The quenching and electron paramagnetic resonance results indicate that active oxygen radicals (O2•−,•OH and SO4•−) and Fe(IV) acted together to realize the efficient CBZ degradation. Moreover, this system exhibited good reusability and environmental adaptability in various real water matrices. The co-catalyst effect of CESM is expected to inspire the exploration of utilization of different waste-biomass-derived organic materials as co-catalysts in the Fe3+/PS system for water purification.

Ammonia Synthesis over Fe-Supported Catalysts Mediated by Face-Sharing Nitrogen Sites in BaTiO3-x Ny Oxynitride.

Invited for this Issue's cover is the group of Professor Hideo Hosono at Tokyo Institute of Technology. The Cover image explores the question which activation dominates N2 activation for ammonia synthesis. The Research Article itself is available at 10.1002/cssc.202300551.

Titanium metal–organic framework-derived nanocrystalline TiO2-supported nitrogen-doped carbon nanostructures as highly efficient antibiotic adsorbents

Metal-organic frameworks (MOFs) are explored extensively as a distinctive precursor for producing porous metal oxide-supported nitrogen-doped carbon nanomaterials. MOF-derived materials can offer tailored porosity, structure, and elemental composition so they are gaining prominence as a new-generation adsorbent for emerging antibiotic contaminant removal in aqueous solutions. In this study, we demonstrate the fabrication of nanocrystalline titanium dioxide-supported nitrogen-doped carbon nanostructures (TiO2@NC) obtained from a titanium metal–organic framework (NH2-MIL-125(Ti)) as a starting precursor. When applied as an adsorbent, TiO2@NC nanospheres efficiently removed high concentrations of tetracycline (TC) in aqueous solutions. The TiO2@NC adsorption process obeyed the Langmuir model and pseudo-second-order kinetics. The optimum adsorption capacity of the TiO2@NC nanospheres is estimated to be 1187.08 mg g−1, which is remarkably superior to several previously reported adsorbents for TC removal. The TiO2@NC adsorbent performs efficiently in a broad pH range (3–8) and shows excellent stability. The post-adsorption characterization signifies the crucial role of the adsorbent's nitrogen sites, surface area, and porous sphere morphology in achieving efficient TC removal through hydrogen bonding, π-π interactions, and surface complexation.

Photoexcited triplet state and singlet oxygen generation of quinine, an antimalarial drug.

Energy transfer from the lowest excited triplet (T1) state of quinine (QN) to ground-state molecular oxygen produces singlet oxygen. In aqueous solutions, a neutral form QN, a singly protonated cation QNH+ and doubly protonated cation QNH22+ are present according to their pKa values. To the best of our knowledge, the pH dependence of QN-photosensitized singlet oxygen generation has not been reported. In the present study, the quantum yields of photosensitized singlet oxygen generation (ΦΔ) by QN, QNH+ and QNH22+ have been determined through the measurements of time-resolved near-IR phosphorescence. ΦΔ decreases in the following order: ΦΔ (QNH+) > ΦΔ (QNH22+) > ΦΔ (QN). The nature of the T1 states of QN, QNH+ and QNH22+ has been studied through the measurements of transient absorption, phosphorescence and EPR by changing the pH of the medium. This is the first report of EPR for the T1 state of QN. The photoexcited T1 state of 6-methoxyquinoline (6-MeOQL), a closely related component, has been studied for comparison. The observed zero-field splitting parameters, phosphorescence spectra and triplet lifetimes suggest that the nature of the T1 state of QN can be regarded as a locally excited 3ππ*state within 6-MeOQL. The two unpaired electrons localize mainly on 6-MeOQL. The nature of the T1 state of QN scarcely changes when the quinuclidine nitrogen site is protonated. Applying the Förster cycle to the T1 states of QN and its protonated cations, it was found that QNH+ becomes more basic when excited to its T1 state.

Therapeutic potential of X12Y12 (X=Al, B, and Y=N, P) nanocages as effective sensors for Ala, Val, Arg, and Asp amino acids

In view of the intensifying research to study the comparative proficiency of innocuous and bioavailable nanomaterials concordance with human systems for drug conveyance, this study was aimed to perusal the comparative efficiency of X12Y12 (X=B, Al, and Y= N, P) nanocages for the adsorption of four amino acids including alanine (Ala), valine (Val), arginine (Arg), and aspartic acid (Asp). Four different nanocages interacted with amino acids at the nitrogen (-NH2), oxygen (-CO), and oxygen (-OH) sites, ensuing in forty eight adsorbate-adsorbent complexes whose sensitivity and reactivity were examined via density functional theory (DFT) calculations at ωB97XD/6-311G+(d,p) level of theory with distinct prominence on the geometry, electronic, and topological scrutiny. The adsorption energy (Eads) for adsorbate-adsorbent complexes found to be highly exothermic and in the range of -15.02 to -58.35 kcal/mol. The consequences of thermodynamic calculations show that adsorption of considered amino acids over the surface of nanocages are thermodynamically favorable. The estimated value of energy gap (Egap) associated with X12Y12 nanocages found to be decreased after forming complex with the amino acid molecules. Therefore, these nanocages act as appropriate sensing material for the development of sensors for the determination of amino acids. To attain the insight into the interactions of amino acids with the nanocages; density of states (DOS), UV–visible spectrum and dipole moment are studied. The QTAIM examination is also accomplished to recognize the interaction in adsorbate-adsorbent complexes. Additionally, ETS-NOCV examination apprise that charge flow from amino acids to the nanocages in all the complexes. Consequently, the study demonstrated that nanocages act as perfect candidates for the adsorption of amino acids.

Synthesis, structural characterization and DFT calculations of a diphenyl-2-pyridylphosphine complex of copper(II)

The reaction of Cu(NO3)2·3H2O with a potentially bidentate P,N-donor ligand, diphenyl-2-pyridylphosphine (PPh2Py), in 1:2 molar ratio resulted in formation of a κ 2N,O-chelated complex, [Cu(κ 2N,O-P(O)Ph2Py)2(NO3)2] (1). A single-crystal X-ray study confirmed the formation of a five-membered κ 2N, O-chelate involving pyridyl nitrogen and phosphine oxide oxygen donor sites. A DFT study was carried out on 1 to understand the chelate ring expansion process upon oxidation with PPh2Py. DFT analysis revealed that 1 contains a relatively strong M-N bond compared to its M-P bond, facilitating the oxidation of the P atom followed by chelate ring expansion.

Synthesis, Characterization, and Environmental Applications of Novel Per-Fluorinated Organic Polymers with Azo- and Azomethine-Based Linkers via Nucleophilic Aromatic Substitution.

This study reports on the synthesis and characterization of novel perfluorinated organic polymers with azo- and azomethine-based linkers using nucleophilic aromatic substitution. The polymers were synthesized via the incorporation of decafluorobiphenyl and hexafluorobenzene linkers with diphenols in the basic medium. The variation in the linkers allowed the synthesis of polymers with different fluorine and nitrogen contents. The rich fluorine polymers were slightly soluble in THF and have shown molecular weights ranging from 4886 to 11,948 g/mol. All polymers exhibit thermal stability in the range of 350-500 °C, which can be attributed to their structural geometry, elemental contents, branching, and cross-linking. For instance, the cross-linked polymers with high nitrogen content, DAB-Z-1h and DAB-Z-1O, are more stable than azomethine-based polymers. The cross-linking was characterized by porosity measurements. The azo-based polymer exhibited the highest surface area of 770 m2/g with a pore volume of 0.35 cm3/g, while the open-chain azomethine-based polymer revealed the lowest surface area of 285 m2/g with a pore volume of 0.0872 cm3/g. Porous structures with varied hydrophobicities were investigated as adsorbents for separating water-benzene and water-phenol mixtures and selectively binding methane/carbon dioxide gases from the air. The most hydrophobic polymers containing the decafluorbiphenyl linker were suitable for benzene separation, while the best methane uptake values were 6.14 and 3.46 mg/g for DAB-Z-1O and DAB-A-1O, respectively. On the other hand, DAB-Z-1h, with the highest surface area and being rich in nitrogen sites, has recorded the highest CO2 uptake at 298 K (17.25 mg/g).

Bifunctional catalysts of modified doped small-sized ZIF and CNTs with entangled structures

For optimizing the lifetime and power of Zn-Air batteries (ZABs), we develop Fe, Co bimetallic doped zeolite imidazolate framework (M@CoFe-ZIF-8) from the perspective of catalytic reaction. After the pyrolysis treatment, the catalyst shows an entangled structure of 100 nm-sized ZIF-8 particles and carbon nanotubes (CNTs). The experimental result shows that the 100 nm-sized CoFe@MNC-CNTs (MNC: metal and nitrogen doped carbon) have better ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) catalytic activities compared with the 1 μm-sized CoFe@BMNC-CNTs structures with the assistance of melamine. On the one hand, it is closely related to the larger specific surface area and mesoporous structure of CoFe@MNC-CNTs. On the other hand, uniformly distributed metal nitrogen (M-Nx) sites and carbon nanotube-wrapped metal nanoparticles may both be effective catalytic active sites for ORR and OER. The CoFe@MNC-CNTs exhibits remarkable catalytic performance, outperforming the commercially available 20 % Pt/C catalyst with a higher half-wave potential (0.865 V vs 0.838 V) in alkaline electrolyte. Meanwhile, the overpotential (Eover) also rivals that of the commercially available RuO2 catalyst. The Zn-air batterry based on CoFe@MNC-CNTs exhibits excellent power density, which is significantly better than Pt/C catalyst (112.1 mW·cm−2 vs 98.2 mW·cm−2). The CoFe@MNC-CNTs also exhibits over 65 h of cycling stability (10 mA·cm−2). In addition, the open circuit voltage (OCV) and cycle time of the flexible battery based on the catalyst of CoFe@MNC-CNTs remain satisfactory (1.525 V, 18 h).

Charge Density Modulation of Pyrene-Related Small Molecules by Nitrogen Heteroatoms Precisely Regulates Photocatalytic Generation of Hydrogen.

Organic semiconductor materials hold promising applications in photocatalytic hydrogen evolution due to their high modifiability and wide range of light absorption capability. In this study, we present an effective strategy for promoting the separation of photoexcited electrons from organic conjugated centers to active sites by modifying different nitrogen-containing groups on pyrene molecules. Building on this foundation, the well-designed catalyst Py-m-2N has demonstrated good performance by achieving a photocatalytic hydrogen evolution rate of 48.86 mmol g-1 h-1, even in the absence of the precious metal platinum cocatalyst. This achievement places the pyrene-based photocatalyst ahead of the majority of its organic counterparts. Our comprehensive characterization and density functional theory calculations reveal that the nitrogen atom not only serves as an active site for hydrogen production but also plays a pivotal role in efficiently accumulating bulk-phase electrons. This electron enrichment process enhances the transport of photoexcited electrons from the light-absorbing pyrene units to the active nitrogen sites. This work provides inspiration for the future design of effective nitrogen-atom-modified organic semiconductor photocatalysts at the molecular level.

Nitrogen sites prevail over textural properties in N-doped carbons for the oxygen reduction reaction

Nitrogen-doped carbon-based electrodes are among the most promising alternatives to platinum-based electrodes in the cathode of fuel cells and metal-air batteries, where the oxygen reduction reaction (ORR) takes place. Among the approaches for improving ORR activity, nitrogen functionalities and well-developed textural properties have proved very effective. Nonetheless, the question of which between nitrogen active sites or textural properties are more crucial in N-doped carbon materials remains unanswered. This work proposes a comparative and critical approach through the selective functionalization of four commercial activated carbons with different textural properties. This study highlights the greater importance of N-doping in relation to the textural properties of carbon materials, and provides fundamental insights for conclusively addressing the ongoing debate within the carbon community about the significance of these two factors in the context of ORR.

Light-stimulated low-power artificial synapse based on a single GaN nanowire for neuromorphic computing

The fast development of the brain-inspired neuromorphic computing system has ignited an urgent demand for artificial synapses with low power consumption. In this work, it is the first time a light-stimulated low-power synaptic device based on a single GaN nanowire has been demonstrated successfully. In such an artificial synaptic device, the incident light, the electrodes, and the light-generated carriers play the roles of action potential, presynaptic/postsynaptic membrane, and neurotransmitter in a biological synapse, respectively. Compared to those of other synaptic devices based on GaN materials, the energy consumption of the single-GaN-nanowire synaptic device can be reduced by more than 92%, reaching only 2.72×10−12 J. It is proposed that the oxygen element can contribute to the synaptic characteristics by taking the place of the nitrogen site. Moreover, it is found that the dynamic “learning−forgetting” performance of the artificial synapse can resemble the behavior of the human brain, where less time is required to relearn the missing information previously memorized and the memories can be strengthened after relearning. Based on the experimental conductance for long-term potentiation (LTP) and long-term depression (LTD), the simulated network can achieve a high recognition rate up to 90% after only three training epochs. Such few training times can reduce the energy consumption in the supervised learning processes substantially. Therefore, this work paves an effective way for developing single-nanowire-based synapses in the fields of artificial intelligence systems and neuromorphic computing technology requiring low-power consumption.

Conjugated Microporous Polymers Based on Octet and Tetratopic Linkers for Efficient Iodine Capture.

Radioactive iodine from nuclear waste poses a huge threat to public safety and raises concerns about environmental pollution. There is thus a growing demand for developing novel adsorbents for highly effective iodine capture. In this work, we design and synthesize three novel conjugated microporous polymers, namely, TPE-PyTTA-CMP, TPE-TAPP-CMP, and TPE-TPDA-CMP, which are constructed by an imidization reaction based on octet and tetratopic linkers. The iodine vapor adsorption experiments show that the three CMPs have an excellent iodine adsorption capacity as high as 3.10, 3.67, and 4.68 g·g-1 under 348 K and ambient pressure conditions, respectively. The adsorbed iodine in the CMPs can be released into methanol in a dramatically rapid manner, and their excellent iodine adsorption performance can still be maintained after multiple cycles. In addition, the CMPs demonstrate good adsorption performance in an n-hexane solution of iodine, and the kinetic experimental data follow the pseudo-second-order model. The hierarchical porosity, extended π-conjugated skeleton, and rich electron-donor nitrogen sites of the CMPs could contribute to their excellent iodine adsorption performance. The knowledge information obtained in this work could open up new possibilities for designing novel CMPs targeting a wide range of environment-related applications.

Exploring Partial Structural Disorder in Anhydrous Paraxanthine through Combined Experiment, Solid-State Computational Modelling, and Molecular Docking

Paraxanthine (PX), a major metabolite of caffeine, a protective agent against Alzheimer’s and Parkinson’s disease, and a promising drug for the treatment of post-COVID 2019 anosmia and ageusia, has been studied in the solid state and protein–ligand complex. Partial disorder in PX, caused by the methyl group at the N(7) position, has been modelled and discussed. The relationship between the unusual structural disorder and the propensity to form a specific system of non-covalent bonds was analyzed. Three 1H-14N NMR-NQR (nuclear magnetic resonance–nuclear quadrupole resonance) experimental techniques were used, namely multiple frequency sweeps, Larmor frequency scanning, and the two-frequency irradiation, followed by solid-state computational modelling (density functional theory, supplemented by quantum theory of atoms in molecules, 3D Hirshfeld surfaces, and reduced density gradient), and molecular docking approaches. New quantitative methods for estimating changes in the global pattern of interactions under the influence of rotation of the methyl group in N(7) based on the Pompeiu–Hausdorff and Bhattacharayya metrics and the Wasserstein distance have been proposed and applied. A spectrum consisting of 12 lines, indicating the presence of 4 chemically inequivalent nitrogen sites in the PX molecule, was recorded, and the lines’ assignment to particular sites was made. The influence of the methyl rotation on the eigenvalues and eigenvectors of the electric field gradient tensor, NQR parameters, and resonance line positions was modelled in the solid (GGA/RPBE, m-GGA/RSCAN) and cluster (Minnesota M062X hybrid). Three factors have been found to determine structural disorder in PX: larger crystal voids near the methyl at N(7) than at N(1) (opening the path for the disorder), hyperconjugation strongly affecting the density distribution in the five-membered ring, and the involvement of the methyl group at N(7) in many non-covalent bonds that intercept (capture) subsequent jumping protons. The Pompeiu–Hausdorff and Bhattacharayya metrics and the Wasserstein distance confirmed the changes in the distribution and strength of non-covalent interactions throughout the molecule as a result of methyl rotation. This effect is clearly visible regardless of the type of metric, and its order of magnitude is consistent with the modulation effect of the NQR spectra (experimental and calculated). Through molecular docking, it was discovered that the PX moiety in protein–ligand complexes adopt the same methyl group conformation at N(7) as in the solid state. It was found that the cooperation–competition between the C-H⋯O hydrogen bonds and C-H⋯H-C dispersion interactions is the crucial factor that impedes methyl rotation and induces structural disorder, as well as being an important factor in the formation of the protein–ligand complexes.

Interfacial Modulation of a Self-Sacrificial Synthesized SnO2@Sn Core-Shell Heterostructure Anode toward High-Capacity Reversible Li+ Storage.

Sn-based anodes are promising high-capacity anode materials for low-cost lithium ion batteries. Unfortunately, their development is generally restricted by rapid capacity fading resulting from large volume expansion and the corresponding structural failure of the solid electrolyte interphase (SEI) during the lithiation/delithiation process. Herein, heterostructural core-shell SnO2-layer-wrapped Sn nanoparticles embedded in a porous conductive nitrogen-doped carbon (SOWSH@PCNC) are proposed. In this design, the self-sacrificial Zn template from the precursors is used as the pore former, and the LiF-Li3N-rich SEI modulation layer is motivated to average uniform Li+ flux against local excessive lithiation. Meanwhile, both the chemically active nitrogen sites and the heterojunction interfaces within SnO2@Sn are implanted as electronic/ionic promoters to facilitate fast reaction kinetics. Consequently, the as-converted SOWSH@PCNC electrodes demonstrate a significantly boosted Li+ capacity of 961 mA h g-1 at 200 mA g-1 and excellent cycling stability with a low capacity decaying rate of 0.071% after 400 cycles at 500 mA g-1, suggesting their great promise as an anode material in high-performance lithium ion batteries.

Synthesis of nanocomposites based on Fe3O4 nanoparticles and nitrogen-doped reduced graphene oxide aerogel by ex-situ approach and their magnetic properties

In this study, were synthesised hybrid nanocomposites (Fe3O4@NrGO) using magnetite nanoparticles (Fe3O4-NPs) and nitrogen-doped reduced graphene oxide (NrGO) aerogel through ex-situ approach, which is simple and easily scalable. The NrGO exhibited 7.96 at% N, demonstrated efficient doping and a high content of active nitrogen sites within the composite matrix. Structural, morphological, and elemental analyses of the obtained nanocomposites confirmed the successful incorporation of Fe3O4-NPs into both doped and undoped aerogel matrices (rGO). The presence of nitrogen sites greatly influenced the interaction and incorporation of nanostructures, as evident from the well-distributed and denser nanoparticle arrangement in Fe3O4@NrGO. The impact of matrix doping was also highlighted through porosity analyses, revealing increases in both; pore volume and surface area. Porosity analysis emphasised the efficacy of the ex-situ strategy and the use of aerogel as the matrix, enabling the achievement of a surface area of 1456 m2 g−1 for Fe3O4@NrGO, owing to the particular swelling mechanism of the “spongy” structure. Vibrating-sample magnetometry and electron paramagnetic resonance spectroscopy techniques were employed to investigate the influence of nitrogenous sites on magnetic properties. The higher nanoparticle density in Fe3O4@NrGO resulted in a saturation magnetisation of 0.7219 emu g−1, more than double that of Fe3O4 @rGO. Resonant peaks at low magnetic fields, characterised by a g-factor of 4.4219, were attributed to paramagnetic nitrogen centres that facilitated the efficient anchoring of Fe3O4-NPs in NrGO

Development of new cobalt, copper, and zinc complexes of Schiff-base ligands as prospective chemotherapeutic agents

Fluorobenzaldehyde was converted into new, bidentate Schiff-base ligands with nitrogen and sulphur donor sites in two steps. The first step proceeds via Knoevenagel condensation; the product obtained was treated with thiosemicarbazide to yield the ligand L1. The Schiff-base ligand, L2, was synthesized by treating L1 with 4-chlorobenzylchloride in a basic medium. Co (II), Cu (II), and Zn (II) complexes were synthesized with the ligands L1 and L2. All these complexes were characterized by FTIR, UV–Vis, NMR spectroscopy, ESI-mass spectral analysis, magnetic moment, molar conductance, thermal, powder XRD, and electrochemical studies. From these studies, the molecular formulae of the complexes were found to be [M(L)2Cl2], where M = Co (II), Cu (II) and Zn (II) and L = L1 or L2 based on the ligand used in the synthesis. The synthesized complexes were observed to have a high spin and distorted octahedral geometry and were non-electrolytic. The UV absorption titrimetric analysis confirmed that these complexes would bind strongly to CT-DNA through the intercalative mode. The electrophorograms supported the statement that Cu (II) complexes could effectively catalyze the hydrolytic cleavage of CT-DNA and can be considered potent metallonuclease agents. The DPPH assay determined the antioxidant properties of these complexes, and the cupric complexes were observed to possess better antioxidant properties than the standard used ascorbic acid. The cell viability analysis of these complexes showed an elevated control of proliferation against a human breast adenocarcinoma (MCF-7) cancer cell line compared to a human cervical carcinoma (HeLa) cell line. The results exhibited by these compounds were compared with the standard drug, cisplatin. The binding affinity of the Cu (II) metal ion complex towards CT-DNA was high when compared to Co (II) and Zn (II) metal ions. These results are in line with the cytotoxicity studies. Molecular docking studies also hold up the experimental data. Cu (II) complexes using ligand L2 show higher efficiency than those with ligand L1 in all biological assays and can be considered a potent DNA-targeting drug.