New Journal of Chemistry最新文献

A facile eco-friendly, simple and cost-effective two-step approach for synthesizing rGO–TiO₂ nanocomposite was explored for the potential switched nonenzymatic detection of hydrogen peroxide (H₂O₂) and 4-nitrophenol. Morphological studies of the nanocomposite revealed the formation of uniform nanoflakes. Electrochemical measurements showed enhanced electrocatalytic performance with low barrier electron transfer between the redox centers of each analyte and the electrode surface. The sensor demonstrated a wide linear detection range from 2.7 nM to 27 nM (R² = 0.99) for H₂O₂ and 22 nM to 224 nM for 4-NP using cyclic voltammetry (CV). The detection limits were determined to be 2.7 nM for H₂O₂ and 20 nM for 4-NP. The rGO–TiO₂ nanocomposite electrode shows an increased sensitivity of 3.3632 A L mol⁻¹ cm⁻² and 21.97 A L mol⁻¹ cm⁻² for H₂O₂ and 4-NP, respectively. The rGO–TiO₂ hybrid electrode utilized different operational potentials for each analyte, which may lead to a voltage-switchable dual-analyte sensor with higher selectivity. rGO–TiO₂ also demonstrated good reproducibility, linear response range and limit of detection for both analytes. In addition, the clinical significance of the nanocomposite was tested for H₂O₂ in milk samples and 4-NP in water samples, which showed a percentage recovery close to 100. These results indicate that rGO–TiO₂-based hybrid nanocomposite is a promising choice for a nonenzymatic biosensor due to its enhanced electrocatalytic activities.

The development of new reusable and efficient heterogeneous catalysts for the construction of bioactive heterocyclic compounds is of great interest in the present era. Two-dimensional (2D) materials, especially 2D vanadium carbide (V₂CT_x MXene), are widely used in energy storage and conversion because of their good electronic properties and broad surface area, but 2D V₂CT_x MXene has not been explored as a catalyst support for organic transformation. Herein, we demonstrate a smooth cyclization reaction between aldehydes and hydrazides to construct 2,5-disubstituted-1,3,4-oxadiazoles catalyzed by 2D V₂CT_x MXenes. We were able to attach a wide range of substituents on the 2nd and 5th positions of the 1,3,4-oxadiazole ring. The present protocol showed broad functional group tolerance with product yields ranging from 84% to 93% in a shorter reaction time (30–45 min). The 2D V₂CT_x MXene catalyst was able to produce good yields of product even after five catalytic cycles.

The influence of Cr³⁺ on the down-conversion luminescence (DCL) of β-PbF₂:Er³⁺/Yb³⁺/Cr³⁺ glass–ceramic composites was studied. Under the excitation of a 378 nm xenon lamp, β-PbF₂:Er³⁺/Yb³⁺/Cr³⁺ glass–ceramic composites exhibit bright DCL with a spectral width ranging from 480 nm to 720 nm, which is reported for the first time. As the doping concentration of Cr³⁺ ions increases, emission intensity with a spectral width ranging from 480 nm to 620 nm also continues to increase, resulting in CIE chromaticity coordinates of β-PbF₂:Er³⁺/Yb³⁺/Cr³⁺ glass–ceramic composites changing from near single red to yellow-green. The broad spectrum from 480 nm to 620 nm originating from radiative transition from ⁴T₁, ²T₁, and ²E to ⁴A₂ energy states of Cr³⁺ ions has been reported for the first time. Cr³⁺ ions enter the F⁻ ions sublattice via interstitial doping and soccupy an extremely weak octahedral crystal field, and the energy state of Cr³⁺ in β-PbF₂ is determined. By combining the energy state structures and DCL spectra of Cr³⁺ and Er³⁺, the DCL process of β-PbF₂:Er³⁺/Yb³⁺/Cr³⁺ glass–ceramic composites and the energy transfer process between Cr³⁺ and Er³⁺ ions are also clarified. The β-PbF₂:Er³⁺/Yb³⁺/Cr³⁺ glass–ceramic composites with a wide range of adjustable colors of DCL presents potential applications in the fields of full spectrum lighting and display.

The photocatalytic self-Fenton system along with the surface plasmon resonance (SPR) effect of nanometals can significantly enhance the catalytic efficiency of semiconductor photocatalysts. In this work, a novel photocatalyst (Ag/Fe–g-C₃N₄) composed of Fe³⁺ doped protonated g-C₃N₄ (Fe–g-C₃N₄) and silver nanoparticles (Ag NPs) modified on its surface was successfully prepared. Furthermore, the morphology, chemical composition, and photoelectrochemical properties of the Ag/Fe–g-C₃N₄ composite photocatalyst were extensively characterized. It was found that the coordination of Fe³⁺ with the amino groups at the edge of g-C₃N₄ changed the electronic structure of the catalyst and improved the photocatalytic activity. The SPR effect of Ag NPs enhanced the light absorption efficiency and charge separation ability of the Fe–g-C₃N₄ hybrid system. The degradation efficiency of the azo dye amaranth by 3% Ag/Fe–g-C₃N₄ was as high as 98.7% under simulated sunlight irradiation for 40 min. It was 1.8 times higher than that of unmodified g-C₃N₄ (54.7%). After 5 cycles of experiments, 3% Ag/Fe–g-C₃N₄ still maintained more than 80% degradation efficiency, which has good photocatalytic activity and stability. Using sacrificial agents, we found that ˙O₂⁻ is the main active substance in degradation, followed by ˙OH and h⁺. This research provides valuable insights into the development of effective photocatalysts and has the potential to bring new perspectives to the remediation of groundwater and deep water.

Neodymium ions are of increasing interest in today's market due to their unique magnetic properties. Therefore, adsorption separation of neodymium is extremely valuable both economically and environmentally. In this work, imprinting cellulose aerogels (IHN-HPMC-NIPAM) with temperature responsiveness were prepared using hydroxypropyl methylcellulose (HPMC) and graphene oxide in combination with ion imprinting technology for selective adsorption of rare earth neodymium ions. The microstructure and physicochemical properties of the aerogels were investigated by means of Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Moreover, adsorption experiments were also carried out to study the adsorption performance of aerogels. Based on experimental results, IHN-HPMC-NIPAM exhibits a high adsorption capacity and certain adsorption selectivity for Nd³⁺ ions. Adsorption experiments demonstrated that IHN-HPMC-NIPAM has a selective adsorption effect on neodymium ions in aqueous solutions, with a maximum adsorption capacity of 68.58 mg g⁻¹. Compared with the non-imprinted aerogel, its maximum adsorption capacity for neodymium ions was significantly enhanced, confirming that the introduced ion-imprinting technology played a crucial role in the adsorption process. The cycling experiments indicated that after four adsorption and desorption cycles, the adsorption capacity of IHN-HPMC-NIPAM could still maintain 86% of its initial capacity. The aerogel can be regenerated by temperature, especially due to the introduction of temperature-responsive monomers. The prepared imprinting adsorbent aerogels were highly efficient, green adsorbent materials with great application prospects due to their abundant source of raw materials, simple preparation process, and pollution-free temperature desorption process.

Photocatalyzed organic transformations driven by visible light using metal–organic frameworks (MOFs) under mild conditions offer an effective strategy to tackle the challenges of energy depletion and environmental pollution. However, achieving effective photocatalytic oxidation of benzylamine under sunlight in mild air conditions remains a significant challenge. Herein, we synthesized three structurally similar Cd-MOFs by incorporating thiazolothiazole derivatives into the frame materials. The photocatalytic performance of the three MOFs was examined, revealing that Cd-3 demonstrated the highest photocatalytic activity. The broad light absorption range and suitable energy levels for photo-oxidation enable Cd-3 to exhibit excellent photocatalytic activity for the oxidative coupling of amines to imines. Additionally, Cd-3 shows remarkable photocatalytic degradation of cationic dyes. This exceptional photocatalytic ability is attributed to the effective separation of electron–hole pairs in the catalyst upon sunlight irradiation, facilitating redox reactions that generate active species. Ultimately, this work expands the potential applications of MOFs based on thiazolothiazole derivatives for photocatalytic organic transformations and offers new insights into the versatile applications of MOFs.

Lithium is one of the most widely used industrial reagents for energy storage, battery production and electronic materials production. Among various agro-wastes, dragon fruit peel is one of the most promising substitutes for metal recovery. The present study aims to synthesize a novel low-cost and sustainable biosorbent, dragon fruit (Hylocereus undatus) peel impregnated with dibenzoyl methane (DBM), for lithium recovery from the aqueous phase. The biosorbent is characterized using SEM, FTIR, XRD, BET, XPS and DFT calculation techniques to understand the composition, structure and surface complexation. The kinetics study suggested that adsorption followed pseudo-second order kinetics with a correlation coefficient (R²) value of 0.99 and a rate constant of 29.28 × 10⁻⁴ g mg⁻¹ min⁻¹. The isotherm studies evaluated the reaction to be heterogeneous with effective binding energies as depicted by Freundlich and Temkin isotherm models. The mechanistic forces include weak van der Waals forces, metal–surface complexation and valence forces. The thermodynamics study revealed the process to be exothermic (ΔH° = −18.28 kJ mol⁻¹) and spontaneous with negative Gibbs free energy values. The maximum lithium uptake capacity was found to be 13.6 mg g⁻¹. Acidic media favoured the recovery of the metal ion up to three cycles. The long term stability study using a fixed bed column showed 84% lithium extraction efficiency for the CMB. The lab scale study is validated using the CMB for lithium extraction from the real geothermal water sample of the Dholera region, Gujarat.

The demand for sustainable and environmentally friendly chemical processes has led to the development of innovative catalytic systems and solvent designs. Herein, we report a novel approach utilizing ruthenium catalysis in deep eutectic solvents (DESs) for the selective alkynylation of C–H bonds. Ruthenium, known for its low toxicity and cost-effectiveness, serves as an excellent alternative to other transition metals in eutectic liquids. Moreover, the utilization of supramolecular β-cyclodextrin-based deep eutectic liquids enhances the eco-friendliness and recoverability of the solvent system. The late-stage functionalization of drugs exemplifies the practical applicability and versatility of this method in organic synthesis, offering a sustainable pathway towards the synthesis of valuable compounds.

Recovery of critical metals such as cobalt from secondary sources is an effective way to reduce the supply risk of metals that are necessary in clean energy technologies, but such recovery processes need to be more benign. Hence, this study presents new insights into leaching cobalt using deep eutectic solvents under mild conditions. The role of ethylene glycol (EG) and water as additives in cobalt leaching was investigated using a mixture containing citric acid (CA):choline chloride (ChCl) in 1 : 1 molar ratio. While the water concentration and Co leaching efficiency were directly related, that was not the case for the EG content. A larger amount of EG in the mixture (CA : ChCl : EG from 1 : 1 : 0.3 to 1 : 1 : 4 molar ratio) decreased the cobalt leaching efficiency, which was attributed to the presence of EG in different coordination forms, as suggested by FTIR spectroscopy. The optimal solvent mixture CA : ChCl : EG (1 : 1 : 1.1) led to leaching efficiencies of 43% cobalt and 65% lithium from lithium cobalt oxide (LiCoO₂) at 60 °C for 48 h. Although lithium(I) was the key to increasing the leaching efficiency, we also observed that the presence of lithium(I) in the leachate could negatively impact the electrochemical reduction process. This may be due to the different speciation of cobalt(II) in the presence and absence of lithium(I), as indicated by NMR spectroscopy.

Metal–organic frameworks (MOFs) with dual metal sites are considered promising electrode materials for electrochemical energy storage applications owing to their unique structural and compositional advantages. Using a simple one-step solvothermal technique, nickel ions were incorporated into MIL-53(Fe) framework to design a nickel-doped iron-based MOF (MIL-53(Fe)-Ni), which was eventually used as an efficient electrode to improve supercapacitor performance. Owing to its distinct hexagonal pyramid-like structure and the synergistic effect of bimetallic ions, the MIL-53(Fe)-Ni-2 electrode material demonstrates a high specific capacity of 408.1 C g⁻¹ at 1 A g⁻¹ and remarkable cycling stability (80.9% capacity retention over 5000 cycles at 10 A g⁻¹) in a half-cell system configuration. For practical applications, a full cell comprising a capacitive-type AC and a battery-type MIL-53(Fe)-Ni-2 was assembled to form an asymmetric supercapacitor device (ASC). The MIL-53(Fe)-Ni-2//AC ASC device resulted in a specific energy of 32.63 W h kg⁻¹ at 1142 W kg⁻¹ and capacity retention and coulombic efficiency of 72.5 and 99.3% respectively, which further led credence to the good stability of MIL-53(Fe)-Ni-2. This work provides insight into the effect of metal doping on modifying the properties of MOFs and demonstrating their great potential in supercapacitor research.