Plasma-Liquid-Induced Synthesis of Scandium-Metalloporphyrin Frameworks for Boosted Sensing and Photosensitization

Inserting metal ions into the porphyrin ring is one of the primary strategies to enhance the properties of porphyrin-based metal-organic frameworks (MOFs). However, the straightforward, rapid, and energy-efficient synthesis of porphyrin-based MOFs with high metallization for the porphyrin ring remains challenging. Herein, a solution anode glow discharge (SAGD) microplasma is presented for the one-step synthesis of scandium-metalloporphyrin frameworks (ScMPFs). The substantial number of electrons provided by the plasma-liquid interface not only accelerated the rapid nucleation and growth of MOFs but also promoted the incorporation of scandium (Sc3+), which has a small ionic radius and strong coordination ability, into the N atoms in the porphyrin ring, and enhanced the metallization of MOFs. The sufficient Sc3+ in frameworks inhibited the recombination of electron-hole pairs, resulting in boosted reactive oxygen species yield and a low fluorescence background of MOFs. Consequently, the ScMPFs are employed for the sensitive and rapid detection of F- in water with a detection limit of 0.24 µm and for efficient bacteriostasis at low doses (10 µg mL-1, 12 mW cm-2 light irradiation for 10 min).

Nickel single atoms anchored on a bipyridine-based covalent organic framework: boosting active sites for photodegradation of acetaminophen

It remains crucial but challenging to construct single-atom photocatalysts based on covalent organic framework (COF) materials in a simple, fast, and controllable manner and to clarify their structure-efficacy relationship. Here, a single-atom photocatalyst (Ni-TpBpy) featuring atomically dispersed Ni sites with a high loading content and a specific tetra-coordinated N2-Ni-Cl2 environment in a bipyridine-based COF was for the first time rapidly synthesized using dielectric barrier discharge (DBD) plasma and a wet chemical method. Visible light-driven Ni-TpBpy can achieve 97.8% photodegradation efficiency of acetaminophen at 0.177 min-1 in 30 min, outperforming other advanced photocatalysts. Experimental studies and density-functional theory (DFT) calculation clarified the role of well-dispersed Ni active sites in enhanced photodegradation, which not only narrowed the bandgap, facilitating carrier separation and migration, but also promoted the generation of reactive superoxide radicals. This study represents the first use of single-atom Ni-TpBpy in the efficient photocatalytic degradation of emerging pollutants with remarkable stability and universality, bringing new insights into the application of COF-based single-atom materials in environmental remediation.

Chiral Metal-Organic Framework Films with Ordered Macropores for Enantioselective Analysis of Proteins

Chiral film-based sensors show great promise for discriminating between enantiomers due to their miniaturization and low power consumption. However, their practical use is hindered by the trade-off between enantioselectivity and mass transfer capability, especially concerning biomacromolecules such as proteins. In this work, we present an effective and straightforward method for creating highly organized macropores within crystalline chiral metal-organic framework (CMOF) films. This approach harnesses the shaping influence of a polystyrene nanosphere template and the crystallization induced by the liquid dielectric barrier discharge plasma. The resultant highly ordered macro-microporous structures improve mass diffusion and access to chiral active sites in the hierarchical CMOF films. Coupled with their inherent chirality, strong fluorescence emission, high crystallinity, and exceptional stability, these attributes endow these CMOF films with enhanced sensing capabilities for chiral molecules. Particularly, the macro-microporous structure facilitates efficient protein recognition, overcoming a significant challenge encountered by MOFs due to protein dimensions surpassing MOF pore sizes. These films exhibit increased enantioselectivity, better limits of detection, and wider linear ranges compared with purely microporous CMOF films. This study thus provides a powerful synthetic approach for hierarchical CMOF films, addressing the limitations of traditional thin film sensors and opening an avenue for efficient chiral sensing of large biomacromolecules.

The design, synthesis and application of metal-organic framework-based fluorescence sensors

Fluorescence-based chemical sensors have garnered significant attention due to their rapid response, high sensitivity, cost-effectiveness and ease of operation. Recently, metal-organic frameworks (MOFs) have been extensively utilized as platforms for constructing fluorescence sensors, owing to their ultra-high porosity, flexible tunability, and excellent luminescent properties. This feature article summarizes the progress made mainly by our research group in recent years in the construction strategies, principles, and types of MOF sensors, as well as their applications in quantitative sensing, qualitative identification analysis, and multimodal/multifunctional analysis. In addition, the challenges and an outlook on the future progression of MOF-based sensors are discussed, highlighting how these studies can contribute to addressing these issues. Hopefully, this feature article can provide some valuable guidance for the construction and application of MOFs in fluorescence sensing, thereby broadening their practical applications.

Multifunctional bimetallic MOF with oxygen vacancy synthesized by microplasma for rapid total antioxidant capacity assessment in agricultural products

The assessment of total antioxidant capacity (TAC) is crucial for evaluating overall antioxidant potential, predicting the risk of chronic diseases, guiding dietary and nutritional interventions, and studying the effectiveness of antioxidants. However, achieving rapid TAC assessment with high sensitivity and stability remains a challenge. In this study, Ce/Fe-MOF with abundant oxygen vacancies was synthesized using microplasma for TAC determination. The microplasma synthesis method was rapid (30 min) and cost-effective. The presence of oxygen vacancies and the collaboration between iron and cerium in Ce/Fe-MOF not only enhanced the catalyst's efficiency but also conferred multiple enzyme-like properties: peroxidase-like, oxidase-like, and superoxide dismutase mimetic activities. Consequently, a simple colorimetric assay was established for TAC determination in vegetables and fruits, featuring a short analysis time of 15 min, a good linear range of 5-60 μM, a low detection limit of 1.3 μM and a good recovery of 91 %-107 %. This method holds promise for rapid TAC assessment in agricultural products.

Rapid cold plasma synthesis of cobalt metal-organic framework/reduced graphene oxide nanocomposites for use as supercapacitor electrodes

Metal-organic frameworks (MOFs) are recognized as a desirable class of porous materials for energy storage applications, despite their limited conductivity. In the present study, Co-MOF-71 was fabricated as a high-performance supercapacitor electrode at ambient temperature using a fast and straightforward, one-pot cold plasma method. A supercapacitor electrode based on Co-MOF@rGO was also synthesized by adding reduced graphene oxide (rGO) during processing to increase the capacitance retention and stability after 4000 cycles from 80 to 95.4%. The Co-MOF-71 electrode provided a specific capacitance (Cs) of 651.7 Fg-1 at 1 Ag-1, whereas the Co-MOF@rGO electrode produced a Cs value of 967.68 Fg-1 at 1 Ag-1. In addition, we fabricated an asymmetric device (Co-MOF@rGO||AC) using Co-MOF-rGO as a high-rate positive electrode and activated carbon (AC) as a negative electrode. This hybrid device has a remarkable specific energy and power density. The combination of MOFs with reduced graphene oxide (rGO) in a cold plasma environment resulted in the formation of a three-dimensional nanostructure composed of nanosheets. This nanostructure exhibited an increased number of electroactive sites, providing benefits for energy storage applications.

Renaissance of elemental phosphorus materials: properties, synthesis, and applications in sustainable energy and environment

The polymorphism of phosphorus-based materials has garnered much research interest, and the variable chemical bonding structures give rise to a variety of micro and nanostructures. Among the different types of materials containing phosphorus, elemental phosphorus materials (EPMs) constitute the foundation for the synthesis of related compounds. EPMs are experiencing a renaissance in the post-graphene era, thanks to recent advancements in the scaling-down of black phosphorus, amorphous red phosphorus, violet phosphorus, and fibrous phosphorus and consequently, diverse classes of low-dimensional sheets, ribbons, and dots of EPMs with intriguing properties have been produced. The nanostructured EPMs featuring tunable bandgaps, moderate carrier mobility, and excellent optical absorption have shown great potential in energy conversion, energy storage, and environmental remediation. It is thus important to have a good understanding of the differences and interrelationships among diverse EPMs, their intrinsic physical and chemical properties, the synthesis of specific structures, and the selection of suitable nanostructures of EPMs for particular applications. In this comprehensive review, we aim to provide an in-depth analysis and discussion of the fundamental physicochemical properties, synthesis, and applications of EPMs in the areas of energy conversion, energy storage, and environmental remediation. Our evaluations are based on recent literature on well-established phosphorus allotropes and theoretical predictions of new EPMs. The objective of this review is to enhance our comprehension of the characteristics of EPMs, keep abreast of recent advances, and provide guidance for future research of EPMs in the fields of chemistry and materials science.

Synthesis and real-time monitoring of the morphological evolution of luminescent Eu(TCPP) MOFs

Real-time acquisition of the morphological information of nanomaterials is crucial to achieving morphological controllable synthesis, albeit being challenging. A novel device was designed, which integrated dielectric barrier discharge (DBD) plasma synthesis and simultaneous in situ spectral monitoring of the formation of metal-organic frameworks (MOFs). Important dynamic luminescence behaviors such as coordination induced emission (CIE), antenna effect (AE), and red-blue shift were continuously captured to reveal the spectral emission mechanism and energy transfer progress and verify the correlation with the morphological evolution of the MOFs. The prediction and control of morphology were successfully achieved with Eu(TCPP) as a model MOF. The proposed method will shed new light on exploring the spectral emission mechanism, energy conversion and in situ morphology monitoring of other luminescent materials.

Wavelength-shift-based visual fluorescence sensing of aspartic acids using Eu/Gd-MOF through pH triggering

With the increasing demand for on-site detection, the current approach of building dual-emission or multi-emission luminescence sensors based on metal-organic frameworks (MOFs) which possess the capacity of self-reference for numerous non-analyte factors falls short of meeting sensing requirements. Therefore, we have designed a novel strategy for constructing wavelength shift-based luminescence sensor named Eu/Gd(TCPP), which exhibits dual-emitting from metal ions Eu³⁺ and flexible rotating aggregation-induced emission (AIE) ligands H₄TCPP (2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine). This sensor was prepared by a simple, green and fast plasma synthesis method. It's worth noting that the fluorescence emission of Eu/Gd(TCPP) shows a specific wavelength shift from ligand peak, and a visual color change from red to blue within a pH range of 4 to 3. Moreover, various characterization data verified that the luminescence switching mechanism of Eu/Gd(TCPP) was attributed to the H⁺-induced collapse of the Eu/Gd(TCPP) crystal structure, followed by untwisting of free ligands that lose rigid MOFs confinement. This hindered the antenna effect from H₄TCPP to Ln³⁺ ions and restricted the rotation emission of ligand, resulting in the red-shifting of the ligand emission and corresponding luminescence switching. By tactfully utilizing the short-range pH response property of Eu/Gd(TCPP), highly sensitive and selective on-site visual detection of acidic aspartic acid can be achieved.

One-step rapid synthesis of Ni0.5Co0.5-CPO-27 nanorod array with oxygen vacancies based on DBD microplasma: As an effective non-enzymatic glucose sensor for beverage and human serum

The rational design of high-efficiency catalysts for non-enzymatic glucose sensing is extremely important for the timely and effective monitoring of glucose content in beverages and human blood. A 3D bimetallic organic framework (Coordination Polymer of Oslo, CPO) nanorod array with oxygen vacancies was green fabricated on carbon cloth (Ni_0.5Co_0.5-CPO-27 NRA/CC) using dielectric barrier discharge (DBD) microplasma for the first time. Density functional theory (DFT) calculations demonstrated that the oxygen vacancy of Ni_0.5Co_0.5-CPO-27 can be effectively induced under DBD microplasma conditions. Based on the 3D nanorod arrays with rich oxygen vacancies and bimetallic synergistic effects, as a non-enzyme glucose sensor, the Ni_0.5Co_0.5-CPO-27 electrode exhibited a sensitivity of 8499.5 μA L/mmol cm^-2 and 3239.2 μA L/mmol cm^-2 and a limit of detection (LOD) of 0.16 μmol/L (S/N = 3). It has been successfully applied to the determination of glucose levels in real samples such as cola, green tea and human serum.

Plasma Meets MOFs: Synthesis, Modifications, and Functionalities

As a porous and network materials consisting of metals and organic ligands, metal-organic frameworks (MOFs) have become one of excellent crystalline porous materials and play an important role in the era about materials science. Plasma, as a useful tool for stimulating efficient reactions under many conditions, and the plasma-assisted technology gets more attractions and endows MOFs more properties. Based on its feature, the research about the modifications and functionalities of MOFs have been developing a certain extent. This review contains a description of the methods for plasma-assisted modification and synthesis of MOFs, with specifically focusing on the plasma-assisted potential for modifications and functionalities of MOFs. The different applications of plasma-assisted MOFs were also presented.

Fast preparation of Eu(BTB) MOFs in dielectric barrier discharge liquid plasma for luminescent sensing of trace iron

Lanthanide metal-organic frameworks Eu(BTB) MOFs was synthesized in low-temperature plasma produced by dielectric barrier discharge (DBD). This DBD synthesis possesses the characteristics of rapid reaction (within 20 min), mild condition (low temperature and atmospheric pressure) and simple operation compared with many traditional synthesis methods. The prepared Eu(BTB) MOF material exhibits typical red light emitting of europium (Eu³⁺ ) at 617 nm, which can selectively and sensitively be quenched in the presence of trace iron(III) ion (Fe³⁺ ). A simple, fast and sensitive fluorescence sensing strategy of Fe³⁺ was thus constructed, with a limit of detection (LOD) of 0.5 μM. Compared with reported fluorescence probes, Eu(BTB) MOFs have also demonstrated the advantages of low cost, easy and fast preparation, great stability, and excellent optical properties, thus making them a promising fluorescence candidate for trace Fe³⁺ sensing for the potential application in biological systems in the future.

Dielectric barrier discharge-accelerated one-pot synthesis of sulfur quantum dots for fluorescent sensing of lead ions and L-cysteine

Here, we report a novel method for the one-pot facile synthesis of sulfur quantum dots (SQDs) based on a dielectric barrier discharge (DBD)-accelerated H₂O₂ etching strategy within merely 20 min. The formation mechanism of SQDs was investigated, with which an "ON-OFF-ON" fluorescence sensor was developed for the detection of Pb²⁺ ions and L-cysteine.

In situ optical spectroscopy for monitoring plasma-assisted formation of lanthanide metal-organic frameworks

A novel system was designed, which integrated in situ spectral monitoring with facile synthesis of lanthanide metal-organic frameworks in dielectric barrier discharge (DBD) plasma. It features miniaturization, cost-effectiveness and universality, for in situ spectral information of scattering and luminescence to gain insight into the reactive processes.

Monitoring nucleic acid amplification process by UiO-66-NH2-based fluorescence sensor

Herein, we developed a nucleic acid amplification process monitoring scheme by use of UiO-66-NH2, in which pyrophosphate ion (PPi) released from the amplification can competitively coordinate with Zr to weaken...

Reusable citric acid modified V/AC catalyst prepared by dielectric barrier discharge for hydroxylation of benzene to phenol

A reusable and efficient citric acid modified V/AC catalyst for benzene hydroxylation was prepared using an environmentally benign DBD method.

Suppressing Defect Formation in Metal-Organic Framework Membranes via Plasma-Assisted Synthesis for Gas Separations

Metal-organic frameworks (MOFs) are considered as promising materials for membrane gas separations. Structural defects within a pure MOF membrane can considerably reduce its selectivity and possibly result in a nonselective separation. This work proposes a solution-phase synthesis with dielectric barrier discharge (DBD) plasma to suppress the formation of defects in the pure MOF membrane of CPO-8-BPY. Through comprehensive solid-state characterization with XRD, SEM, XPS, solid-state NMR, and XAFS, DBD plasma is demonstrated to facilitate deprotonation in the H₂aip linker, which leads to a smaller and more uniform particle size of CPO-8-BPY. The narrow grain size distribution effectively reduces the pinhole-type defects in the pure CPO-8-BPY membrane and endows it with good ideal selectivity for H₂/CH₄ (α_H2/CH4 = 28.2) and N₂/CH₄ (α_N2/CH4 = 5.4). The selectivity for H₂/CH₄ of this membrane from a mixed-gas permeation test is found to be 15.4. Molecular simulations are also performed to gain insights into the gas transport properties of this MOF. The results suggest that ligand rotation plays an important role in CPO-8-BPY when being applied to the membrane separation of N₂/CH₄.

Miniaturized TOC analyzer using dielectric barrier discharge for catalytic oxidation vapor generation and point discharge optical emission spectrometry

Total organic carbon (TOC) is an important parameter describing organic pollution degree of waters. Due to the increasing need of field analysis and drawbacks of conventional TOC analytical instruments, miniaturized TOC analyzers are still demanding. In this work, a dielectric barrier discharge (DBD) microplasma was utilized for catalytic oxidation vapor generation (COVG) of organic compounds into CO₂, and a point discharge (PD) microplasma was employed to excite the carbon atomic emission spectra for quantification. Sample solution with phosphoric acid and persulfate solution was injected into the DBD-COVG reactor by a syringe to convert organic compounds into CO₂ efficiently and quickly, which was subsequently transported into the point discharge optical emission spectrometer (PD-OES) for detecting carbon at 193.09 nm. Under optimal experimental conditions, high oxidation efficiencies for several organic compounds were achieved, i.e., 96.4%, 95.1% and 94.3% for 50 mg L^-1 potassium hydrogen phthalate (KHP), sodium laurylsulfonate and phenol, respectively. A limit of detection (LOD) of 0.02 mg L^-1 (as C) was obtained, with a precision of 3.9% (relative standard deviation, RSD) at 15 mg L^-1 TOC standard (as C). The possible catalytic oxidation mechanism was proposed with the characteristic results of electron paramagnetic resonance (EPR). Its potential environmental application was demonstrated by successfully analyzing TOC in underground water, surface river water and surface sedimentary water samples from oil fields, with analytical results agreed well with those obtained by the commercial high-temperature combustion coupled nondispersive infrared absorption (HTC-NDIR) technique.

Synthesis of Cu(OH)F microspheres using atmospheric dielectric barrier discharge microplasma: a high-performance non-enzymatic electrochemical sensor

Cu(OH)F microspheres were in situ synthetized using microplasma and were employed as an electrochemical sensor for glucose, hydrogen peroxide and formaldehyde.

Rapid and scalable production of high-quality phosphorene by plasma-liquid technology

Scalable synthesis of few-layered phosphorene typically relies on liquid ultrasonic/shear exfoliation but this technique suffers from drawbacks such as the long processing time, small sheet size, and poor quality. Herein, a simple and efficient plasma-liquid technique for rapid (∼5 minutes) and scalable production of few-layered high-quality phosphorene has been described. The plasma-exfoliated phosphorene has a tunable thickness less than 10 nanometers and a large size over a micrometer, enabling the fabrication of a macroscopic photodetection device with good photo-response. This plasma-exfoliation method has large potential in the development of phosphorene-related technologies as well as mass production of two-dimensional materials.