A Novel Carbon Nitride Nanosheets-based Electrochemical Sensor for Determination of Hydroxychloroquine in Pharmaceutical Formulation and Synthetic Urine Samples

This study introduces modified carbon paste electrodes with carbon nitride nanosheets (CNNS) and outlines their application for the determination of hydroxychloroquine sulfate (HCQ) in tablets and synthetic urine samples. CNNS were synthesized by hydrothermal route (200 °C, 10 h) using melamine and citric acid as their precursors. The carbon nitride nanosheets-based electrode (CNNS/E) presented a linear dynamic range for HCQ (LDR), ranging from 10.0 nmol l⁻¹ to 6.92 μmol l⁻¹, and detection (LOD) and quantification limits (LOQ) of 0.16 nmol l⁻¹ and 0.52 nmol l⁻¹, respectively. LOD and LOQ were calculated by the equations: LOD=3(S_d/b), and LOQ=10(S_d/b). The modified sensor presented excellent relative standard deviations for parameters such as repeatability (2.39 % and 1.87 %) and reproducibility (3.22 % and 2.32 %) in HCQ oxidation peaks (1 and 2). The CNNS/E has not shown significant variations in its anodic signal intensity in the presence of some organic and inorganic substances. It is worth bearing in mind that CNNS/E can be easily manufactured and the sensor has the lowest HCQ detection limits reported so far. The proposed sensor was successfully applied for HCQ determination in tablets and synthetic urine, showing good recovery values and an error of 0.60 % about comparative method in tablet samples, assuring the quality of the method.     

Synthesis of Quinoline/Phenanthroline Impregnated Sugarcane Bagasse for Recovering Uranium(VI) and Thorium(IV) from their Solutions

This present research aims to synthesize and investigate the adsorption potential of sugarcane bagasse (SCB) impregnated with 8 hydroxy quinolone 8-(HQ) and 1,10 phenethroline (phen) to prepare impregnated sugarcane bagasse (ISCB) for removal U^VI and Th^IV. The effects of the operating parameters, including pH of the solution, contact time, initial concentration, temperature, dose and interfering ions on the adsorption efficiency were investigated to identify an optimal condition. The characterization of SEM-EDX and FTIR analyses shows that ISCB has a porous structure and carbon-containing functional groups. The adsorption result revealed that ISCB removed 98 % for both U^VI and Th^IV. The result obtained fitted well for Langmuir isotherms model with 185.19 mg · g^–1 and 250 mg · g^–1 as theoretical capacity for U^VI and Th^IV respectively. The adsorption process followed the pseudo-second-order kinetic model. In conclusion, this study proved that ISCB has the potential to be used as an effective and low-cost adsorbent to remove U^VI and Th^IV. Finally we obtain products from thorium as ThO₂ and uranium as Na₂U₂O₇ from Abu Rushied leach liquor.     

Facile synthesis of magnetic hybrid metal–organic frameworks with high adsorption capacity for methylene blue

A magnetic hybrid material (Fe₃O₄‐COOH/HKUST‐1) was easily synthesized via a two‐step simple solvothermal method. Through adding sodium acrylate directly into the synthesis of Fe₃O₄ spheres, the surface has more carboxyl groups. It is notable that the reactions proceed without use of organic surfactants. The magnetic hybrid material was characterized using various techniques. The magnetic hybrid material has a high specific surface area (430.15 m² g⁻¹) and excellent magnetism (23.65 emu g⁻¹). It is an efficient adsorbent for removing organic dyes like methylene blue (MB) from aqueous solution. It also can be easily recovered from liquid media using an external magnetic field. Adsorption experiment shows the magnetic hybrid material possesses a high adsorption capacity (118.6 mg g⁻¹), and has high adsorption efficiency (94.3%) after five adsorption cycles with ethanol (0.2% HCl) as eluent. The sorption kinetics and isotherm analysis indicate these sorption processes are better fitted to the pseudo‐second‐order and Langmuir equations. Thermodynamic study shows the sorption processes are spontaneous and endothermic.     

General Synthesis of Sulfonate-Based Metal–Organic Framework Derived Composite of MxSy@N/S-Doped Carbon for High-Performance Lithium/Sodium Ion Batteries

A general and simple strategy is realized for the first time for the preparation of metal sulfide (M_xS_y) nanoparticles immobilized into N/S co-doped carbon (NSC) through a one-step pyrolysis method. The organic ligand 1,5-naphthalenedisulfonic acid in the metal–organic framework (MOF) precursor is used as a sulfur source, and metal ions are sulfurized in situ to form M_xS_y nanoparticles, resulting in the formation of M_xS_y/NSC (M=Fe, Co, Cu, Ni, Mn, Zn) composites. Benefiting from the M_xS_y nanoparticles and conductive carbon, a synergistic effect of the composite is achieved. For instance, the composite of Fe₇S₈/NSC as an anode displays excellent long-term cycling stability in lithium/sodium ion batteries. At 5 A g⁻¹, large capacities of 645 mA h g⁻¹ and 426.6 mA h g⁻¹ can be retained after 1500 cycles for the lithium-ion battery and after 1000 cycles for the sodium-ion battery, respectively.     

Chitin-based magnetic composite for the removal of contaminating substances from aqueous media

A method of obtaining multipurpose magnetic chitin, which combines the magnetic properties of magnetite and the adsorption properties of polysaccharide, was proposed. The possibility of using chitin-(CT) and chitosan (CS)-containing magnetic composites for the adsorption of inorganic ions Co^II and Cr^VI and organic substances (2- and 4-nitrophenols) from aqueous media was analyzed. It was shown that the adsorption capacity of magnetic chitin with respect to Co^II and Cr^VI ions reached 41 mg g^?1 and 15 mg g^?1, respectively. The maximum adsorption capacity for 4-nitrophenol (19 mg g^?1 per CT-containing magnetic composite or 56 mg g^?1 per chitin component) was about three times higher than for 2-nitrophenol. The obtained adsorbent Fe₃O₄/CT is environmentally friendly and reusable.

     

Preparation of carbon coated Fe3O4 nanoparticles for magnetic separation of uranium

Uranium(VI) was removed from aqueous solutions using carbon coated Fe₃O₄ nanoparticles (Fe₃O₄@C). Batch experiments were conducted to study the effects of initial pH, shaking time and temperature on uranium sorption efficiency. It was found that the maximum adsorption capacity of the Fe₃O₄@C toward uranium(VI) was ∼120.20 mg g⁻¹ when the initial uranium(VI) concentration was 100 mg L⁻¹, displaying a high efficiency for the removal of uranium(VI) ions. Kinetics of the uranium(VI) removal is found to follow pseudo-second-order rate equation. In addition, the uranium(VI)-loaded Fe₃O₄@C nanoparticles can be recovered easily from aqueous solution by magnetic separation and regenerated by acid treatment. Present study suggested that magnetic Fe₃O₄@C composite particles can be used as an effective and recyclable adsorbent for the removal of uranium(VI) from aqueous solutions.     

The preparation of PZS-OH/CNT composite and its adsorption of U(VI) in aqueous solutions

In this paper, polycyclotriphosphazene coated carbon nanotubes (PZS-OH/CNT) composite material has been synthesized via a facial method. The prepared PZS-OH/CNT was characterized by FTIR, BET, zeta potential and SEM. The material was investigated as an adsorbent for the adsorption towards U(VI) from aqueous solutions. Several parameters like solution pH, contact time and temperature were used to evaluate the sorption efficiency. The results indicated that the adsorption capacity of uranium on PZS-OH/CNT was improved from 41.48 mg g⁻¹ for CNT to 338.98 mg g⁻¹ due to the presence of functional groups on PZS-OH/CNT. The U(VI) sorption on PZS-OH/CNT was well fitted to the Langmuir adsorption isotherm and pseudo-second kinetics models. The thermodynamic parameters (ΔH, ΔS and ΔG) showed the U(VI) adsorption on CNT and PZS-OH/CNT was endothermic and spontaneous in nature.

     

Application of vapour phase calibration method for determination of sorption of gases and VOC in polydimethylsiloxane membranes

Equilibrium sorption of oxygen, carbon dioxide, ethylene, dimethyl sulphide, trichloroethylene and toluene in polydimethylsiloxane (PDMS) at 30 °C is reported. Sorption isotherms of all compounds are well described by Henry’s law within the concentration intervals studied (0.008–257 g m⁻³). Vapour phase calibration (VPC), a static headspace method, was applied instead of the usual gravimetric and barometric sorption methods. Simple, rapid and reliable determination of air-PDMS partition coefficients (S) varying between 1 and 900 (g m⁻³/g m⁻³) was achieved by this method. Solubility of toluene in PDMS was the best of all tested compounds, followed by trichloroethylene, dimethyl sulphide, ethylene, carbon dioxide and oxygen. This observed sequence can be explained by the penetrant condensability, expressed by its critical temperature (T_c). Only for ethylene, a higher solubility is measured than expected from the correlation between S and T_c. This is caused by the relative high interaction of ethylene with the polymer. The Flory–Rehner interaction parameter, χ, for ethylene was calculated 0.004 while the χ values of the other compounds varied between 0.37 and 0.80. The solubility coefficients are shown to be independent on relative air humidity. For the compounds and concentration levels studied, the sorption of dimethyl sulphide is unaffected by the simultaneous sorption of other VOC. This non-competitive behaviour is consistent with the linear partition mechanism.     

Co9S8@CN Composites Obtained from Thiacalix[4]arene-Based Coordination Polymers for Supercapacitor Applications

Metal sulfides have been recognized as promising electrodes for electrochemical energy storage owing to their remarkable electrochemical properties. Here, we demonstrate the preparation of Co₉S₈ nanoparticles anchored on a carbon matrix (denoted as Co₉S₈-X@CN (X=1, 2)) from precursor sources, two 1D infinite coordination polymers 1 and 2 . The two polymers were assembled by linking Co₄-TC4A secondary building blocks (SBUs) with ligands L₁ and L₂, respectively (H₄TC4A=p-tert-butylthiacalix[4]arene, L₁=1,4-bis(2H-tetrazol-5-yl)benzene, L₂=1,3-bis(2H-tetrazol-5-yl)benzene). The composites obtained from 1D polymers showed different morphologies, that is, the Co₉S₈ nanoparticles of Co₉S₈-1@CN are octahedral with a size of ca. 140 nm, while the lamellar Co₉S₈ nanoparticles in Co₉S₈-2@CN possess different sizes (50–150 nm). The Co₉S₈-2@CN immobilized on nickel foam (Co₉S₈-2@CN/NF) show better supercapacitive performance than that of Co₉S₈-1@CN. Co₉S₈-2@CN showed exceptionally high activities, combining higher specific capacitances (445.2 F g⁻¹ at 2 A g⁻¹ and 393.9 F g⁻¹ and 5 A g⁻¹), rate capacity (94.5% retention at 2 A g⁻¹), and long-term stability (79.2% retention at 5 A g⁻¹ over 1000 cycles). The smaller size and larger BET surface area of Co₉S₈-2@CN nanoparticles can improve the electrical conductivity and provide facile pathways for charge transport, thus leading to conspicuous electrochemical performance of Co₉S₈-2@CN compared with its Co₉S₈-1@CN counterpart.     

Hollow Carbon Sphere-Modified Graphitic Carbon Nitride for Efficient Photocatalytic H2 Production

A novel hybrid photocatalyst composed of hollow carbon nanospheres (NCS) and graphitic carbon nitride (CN) curly nanosheets has been prepared by the calcination of a NCS precursor and freeze-dried urea. The optimized photocatalyst exhibits an efficient photocatalytic performance under visible light irradiation with a highest H₂ generation rate of 3612.3 μmol g⁻¹ h⁻¹, leading to an apparent quantum yield of 10.04 % at 420 nm, five times higher than the widely reported benchmark photocatalyst CN (2.01 % AQY). The materials characterization shows that NCS-modified CN curly nanosheets can promote photoelectron transfer and suppress charge recombination through their special coupling interface and NCS as an electron acceptor, which significantly improves the photocatalytic efficiency. Thus, this study provides an efficient strategy for the design of highly efficient photocatalyst, particularly suitable for a totally metal-free photocatalytic system.     

Photo-fenton refreshable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@HCS adsorbent for the elimination of tetracycline hydrochloride

A yolk–shell-structured sphere composed of a superparamagnetic Fe₃O₄ core and a carbon shell (Fe₃O₄@HCS) was etched from Fe₃O₄@SiO₂@carbon by NaOH, which was synthesized through the layer-by-layer coating of Fe₃O₄. This yolk–shell composite has a shell thickness of ca. 27 nm and a high specific surface area of 213.2 m² g^?1. Its performance for the magnetic removal of tetracycline hydrochloride from water was systematically examined. A high equilibrium adsorption capacity of ca. 49.0 mg g^?1 was determined. Moreover, the adsorbent can be regenerated within 10 min through a photo-Fenton reaction. A stable adsorption capacity of 44.3 mg g^?1 with a fluctuation <10% is preserved after 5 consecutive adsorption–degradation cycles, demonstrating its promising application potential in the decontamination of sewage water polluted by antibiotics.     

Rational Construction of 2D Fe3O4@Carbon Core–Shell Nanosheets as Advanced Anode Materials for High-Performance Lithium-Ion Half/Full Cells

Transition metal oxides have vastly limited practical application as electrode materials for lithium-ion batteries (LIBs) due to their rapid capacity decay. Here, a versatile strategy to mitigate the volume expansion and low conductivity of Fe₃O₄ by coating a thin carbon layer on the surface of Fe₃O₄ nanosheets (NSs) was employed. Owing to the 2D core–shell structure, the Fe₃O₄@C NSs exhibit significantly improved rate performance and cycle capability compared with bare Fe₃O₄ NSs. After 200 cycles, the discharge capacity at 0.5 A g⁻¹ was 963 mA h g⁻¹ (93 % retained). Moreover, the reaction mechanism of lithium storage was studied in detail by ex situ XRD and HRTEM. When coupled with a commercial LiFePO₄ cathode, the resulting full cell retains a capacity of 133 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹, which demonstrates its superior energy storage performance. This work provides guidance for constructing 2D metal oxide/carbon composites with high performance and low cost for the field of energy storage.     

Regenerable Covalent Organic Frameworks for Photo-enhanced Uranium Adsorption from Seawater

Uranium is a key resource for the development of the nuclear industry, and extracting uranium from the natural seawater is one of the most promising ways to address the shortage of uranium resources. Herein, a semiconducting covalent organic framework (named NDA-TN-AO) with excellent photocatalytic and photoelectric activities was synthesized. The excellent photocatalytic effect endowed NDA-TN-AO with a high anti-biofouling activity by generating biotoxic reactive oxygen species and promoting photoelectrons to reduce the adsorbed U^VI to insoluble U^IV, thereby increasing the uranium extraction capacity. Owing to the photoinduced effect, the adsorption capacity of NDA-TN-AO to uranium in seawater reaches 6.07 mg g⁻¹, which is 1.33 times of that in dark. The NDA-TN-AO with enhanced adsorption capacity is a promising material for extracting uranium from the natural seawater.     

Search for new iron single-molecule magnets

The synthesis, X-ray structure, and magnetic properties of a trinuclear iron complex with the formulation [Fe₃O₂Cl₂(4,7-Me-phen)₆](BF₄)₃ (complex 1) are reported. DC magnetic susceptibility measurements show the Fe atoms are antiferromagnetically coupled, yielding an S=5/2 ground state. An investigation as to whether complex 1 exhibits the properties associated with single-molecule magnetism was undertaken. Detailed high frequency EPR experiments were carried out to determine the spin Hamiltonian parameters associated with the S=5/2 spin ground state. Analysis of the temperature dependence of the transitions seen with the magnetic field oriented along the easy axis (z axis) of the Fe₃ complex confirm that the molecule has a positive D value. A fit of the frequency dependence of the resonances afforded the following spin Hamiltonian parameters: S=5/2, g_z=1.95, g_x=g_y=2.00, D=0.844 cm⁻¹, E=±0.117 cm⁻¹, and B₄ ⁰=−2.7×10⁻⁴ cm⁻¹. Low temperature magnetization versus magnetic field data confirm that complex 1 has no barrier towards magnetization reversal. Thus, it is concluded that, due to the positive D-value, complex 1 is not a single-molecule magnet.     

Highly Dispersible Hexagonal Carbon–MoS2–Carbon Nanoplates with Hollow Sandwich Structures for Supercapacitors

MoS₂, a typical layered transition-metal dichalcogenide, is promising as an electrode material in supercapacitors. However, its low electrical conductivity could lead to limited capacitance if applied in electrochemical devices. Herein, a new nanostructure composed of hollow carbon–MoS₂–carbon was successfully synthesized through an l -cysteine-assisted hydrothermal method by using gibbsite as a template and polydopamine as a carbon precursor. After calcination and etching of the gibbsite template, uniform hollow platelets, which were made of a sandwich-like assembly of partial graphitic carbon and two-dimensional layered MoS₂ flakes, were obtained. The platelets showed excellent dispersibility and stability in water, and good electrical conductivity due to carbon provided by the calcination of polydopamine coatings. The hollow nanoplate morphology of the material provided a high specific surface area of 543 m² g⁻¹, a total pore volume of 0.677 cm³ g⁻¹, and fairly small mesopores (≈5.3 nm). The material was applied in a symmetric supercapacitor and exhibited a specific capacitance of 248 F g⁻¹ (0.12 F cm⁻²) at a constant current density of 0.1 A g⁻¹; thus suggesting that hollow carbon–MoS₂–carbon nanoplates are promising candidate materials for supercapacitors.     

Fe3O4@C Nanotubes Grown on Carbon Fabric as a Free-Standing Anode for High-Performance Li-Ion Batteries

Recently, Li-ion batteries (LIBs) have attracted extensive attention owing to their wide applications in portable and flexible electronic devices. Such a huge market for LIBs has caused an ever-increasing demand for excellent mechanical flexibility, outstanding cycling life, and electrodes with superior rate capability. Herein, an anode of self-supported Fe₃O₄@C nanotubes grown on carbon fabric cloth (CFC) is designed rationally and fabricated through an in situ etching and deposition route combined with an annealing process. These carbon-coated nanotube structured Fe₃O₄ arrays with large surface area and enough void space can not only moderate the volume variation during repeated Li⁺ insertion/extraction, but also facilitate Li⁺/electrons transportation and electrolyte penetration. This novel structure endows the Fe₃O₄@C nanotube arrays stable cycle performance (a large reversible capacity of 900 mA h g⁻¹ up to 100 cycles at 0.5 A g⁻¹) and outstanding rate capability (reversible capacities of 1030, 985, 908, and 755 mA h g⁻¹ at 0.15, 0.3, 0.75, and 1.5 A g⁻¹, respectively). Fe₃O₄@C nanotube arrays still achieve a capacity of 665 mA h g⁻¹ after 50 cycles at 0.1 A g⁻¹ in Fe₃O₄@C//LiCoO₂ full cells.     

Facile Preparation of CuCo2S4/Cu7.2S4 Nanocomposites as High-Performance Cathode Materials for Rechargeable Magnesium Batteries**

Rechargeable magnesium batteries (RMBs) have been considered a promising energy-storage device due to their high energy density and high safety, but they still suffer from a lack of high-rate performance and cycle performance of the cathode. Nanosized CuCo₂S₄/Cu_7.2S₄ composites have been synthesized for the first time by a facile solvothermal method. Herein, the magnesium ion storage behavior when applied in the cathode for RMBs is discussed. Electrochemical results demonstrated that the CuCo₂S₄/Cu_7.2S₄ composites exhibit a high initial discharge capacity of 256 mAh g⁻¹ at 10 mA g⁻¹ and 123 mAh g⁻¹ at 300 mA g⁻¹ at room temperature and an outstanding long-term cyclic stability over 300 cycles at 300 mA g⁻¹. Furthermore, the electrochemical storage mechanism demonstrated that the storage process of magnesium ion in the CuCo₂S₄/Cu_7.2S₄ cathode is mainly driven by strong pseudocapacitive effects.     

Carbon-Based Electron Buffer Layer on ZnOx−Fe5C2−Fe3O4 Boosts Ethanol Synthesis from CO2 Hydrogenation

The conversion of CO₂ into ethanol with renewable H₂ has attracted tremendous attention due to its integrated functions of carbon elimination and chemical synthesis, but remains challenging. The electronic properties of a catalyst are essential to determine the adsorption strength and configuration of the key intermediates, therefore altering the reaction network for targeted synthesis. Herein, we describe a catalytic system in which a carbon buffer layer is employed to tailor the electronic properties of the ternary ZnO_x−Fe₅C₂−Fe₃O₄, in which the electron-transfer pathway (ZnO_x→Fe species or carbon layer) ensures the appropriate adsorption strength of −CO* on the catalytic interface, facilitating C−C coupling between −CH_x* and −CO* for ethanol synthesis. Benefiting from this unique electron-transfer buffering effect, an extremely high ethanol yield of 366.6 g_EtOH kg_cat⁻¹ h⁻¹ (with CO of 10 vol % co-feeding) is achieved from CO₂ hydrogenation. This work provides a powerful electronic modulation strategy for catalyst design in terms of highly oriented synthesis.     

Hierarchical FeCo2S4@FeNi2S4 Core/Shell Nanostructures on Ni Foam for High-Performance Supercapacitors

The design of electrode materials with rational core/shell structures is promising for improving the electrochemical properties of supercapacitors. Hence, hierarchical FeCo₂S₄@FeNi₂S₄ core/shell nanostructures on Ni foam were fabricated by a simple hydrothermal method. Owing to their structure and synergistic effect, they deliver an excellent specific capacitance of 2393 F g⁻¹ at 1 A g⁻¹ and long cycle lifespan as positive electrode materials. An asymmetric supercapacitor device with FeCo₂S₄@FeNi₂S₄ as positive electrode and graphene as negative electrode exhibited a specific capacitance of 133.2 F g⁻¹ at 1 A g⁻¹ and a high energy density of 47.37 W h kg⁻¹ at a power density of 800 W kg⁻¹. Moreover, the device showed remarkable cycling stability with 87.0 % specific-capacitance retention after 5000 cycles at 2 A g⁻¹. These results demonstrate that the hierarchical FeCo₂S₄@FeNi₂S₄ core/shell structures have great potential in the field of electrochemical energy storage.     

Multi-stage Ordered Mesoporous Carbon-graphene Aerogel-Ni3S2/Co4S3 for Supercapacitor Electrode

Transition metal sulfides have emerged as promising materials in supercapacitor. In this work, we firstly developed an interface-induced superassembly approach to fabricate NiS_x and CoS_x nanoparticles, which based on ordered mesoporous carbon-graphene aerogel composites for supercapacitor electrodes. The obtained multi-component superassembled nanoparticles-carbon matrix composites have controllable 3D porous structure of multi-stage composite. The two-dimensional graphene interlaced to form a 3D framework with large sponge-like pores, and then the graphene surface was loaded with mesoporous carbon with mesoporous pore size and vertical orientation. The composites display high specific capacitance of 958.1 F g⁻¹ at 0.1 A g⁻¹. The capacitance retains about 97.3 % after 3000 charging-discharging cycles at 2 A g⁻¹. These results indicate that the obtained OMC−GA−Ni₃S₂/Co₄S₃ is a promising material for electrochemical capacitors, which providing new technical methods and ideas for the research of new energy and analytical sensor materials in the fields of energy storage, photocatalysis, point-of-care testing devices and other fields.