Synergistic catalysis and detection of hydrogen peroxide based on a 3D-dimensional molybdenum disulfide interspersed carbon nanotubes nanonetwork immobilized chloroperoxidase biosensor

Enzyme-based electrochemical biosensors are promising for a wide range of applications due to their unique specificity and high sensitivity. In this work, we present a novel enzyme bioelectrode for the sensing of hydrogen peroxide (H2O2). The molybdenum disulfide nanoflowers (MoS2) is self-assembled on carboxylated carbon nanotubes (CNT) to form a three-dimensional conductive network (3D-CNT@MoS2), which is modified with 1-ethyl-3-methylimidazolium bromide (ILEMB), and followed by anchoring chloroperoxidase (CPO) onto the nanocomposite (3D-CNT@MoS2/ILEMB) through covalent binding to form a bioconjugate (3D-CNT@MoS2/ILEMB/CPO). The ILEMB modified 3D-CNT@MoS2/ILEMB has good hydrophilicity and conductivity, which not only provides a suitable microenvironment for the immobilization of CPO but also facilitates the direct electron transfer (DET) of CPO at the electrode. The 3D-CNT@MoS2/ILEMB/CPO bioconjugate modified electrode has a high catalytic efficiency for H2O2. Through electroenzymatic synergistic catalysis for H2O2 detection by 3D-CNT@MoS2/ILEMB/CPO-GCE, a wide detection range of 0.2 μmol·L-1 to 997 μmol·L-1 and a low detection limit of 0.097 μmol･L-1 with high sensitivity of 1050 µA·mmol·L-1·cm-2 were achieved. Additionally, the 3D-CNT@MoS2/ILEMB/CPO-GCE displayed exceptional stability, selectivity, and reproducibility. Furthermore, 3D-CNT@MoS2/ILEMB/CPO-GCE is suitable for sensing of H2O2 in human urine s with good recovery, suggesting its potential application for the detection of H2O2 in biomedical field.

Interfacial engineering of transition metal dichalcogenide/carbon heterostructures for electrochemical energy applications

To support the global goal of carbon neutrality, numerous efforts have been devoted to the advancement of electrochemical energy conversion (EEC) and electrochemical energy storage (EES) technologies. For these technologies, transition metal dichalcogenide/carbon (TMDC/C) heterostructures have emerged as promising candidates for both electrode materials and electrocatalysts over the past decade, due to their complementary advantages. It is worth noting that interfacial properties play a crucial role in establishing the overall electrochemical characteristics of TMDC/C heterostructures. However, despite the significant scientific contribution in this area, a systematic understanding of TMDC/C heterostructures' interfacial engineering is currently lacking. This literature review aims to focus on three types of interfacial engineering, namely interfacial orientation engineering, interfacial stacking engineering, and interfacial doping engineering, of TMDC/C heterostructures for their potential applications in EES and EEC devices. To accomplish this goal, a combination of experimental and theoretical approaches was used to allow the analysis and summary of the fundamental electrochemical properties and preparation strategies of TMDC/C heterostructures. Moreover, this review highlights the design and utilization of the interfacial engineering of TMDC/C heterostructures for specific EES and EEC devices. Finally, the challenges and opportunities of using interfacial engineering of TMDC/C heterostructures in practical EES and EEC devices are outlined. We expect that this review will effectively guide readers in their understanding, design, and application of interfacial engineering of TMDC/C heterostructures.

Nanocomposites of Nitrogen-Doped Graphene Oxide and Manganese Oxide for Photodynamic Therapy and Magnetic Resonance Imaging

Cancer is a leading cause of death worldwide. Conventional methods of cancer treatment, including chemotherapy and radiotherapy, are associated with multiple side effects. Recently, photodynamic therapy (PDT) has emerged as an effective therapeutic modality for cancer treatment without adversely affecting normal tissue. In this study, we synthesized nitrogen doped graphene (NDG) and conjugated it with Mn₃O₄ nanoparticles to produce NDG-Mn₃O₄ nanocomposite with the aim of testing its bimodal performance including PDT and magnetic resonance imaging (MRI). We did not use any linker or binder for conjugation between NDG and Mn₃O₄, rather they were anchored by a milling process. The results of cell viability analysis showed that NDG-Mn₃O₄ nanocomposites caused significant cell death under laser irradiation, while control and Mn₃O₄ nanoparticles showed negligible cell death. We observed increased generation of singlet oxygen after exposure of NDG-Mn₃O₄ nanocomposites, which was directly proportional to the duration of laser irradiation. The results of MRI showed concentration dependent enhancement of signal intensity with an increasing concentration of NDG-Mn₃O₄ nanocomposites. In conclusion, NDG-Mn₃O₄ nanocomposites did not cause any cytotoxicity under physiological conditions. However, they produced significant and dose-dependent cytotoxicity in cancer cells after laser irradiation. NDG-Mn₃O₄ nanocomposites also exhibited concentration-dependent MRI contrast property, suggesting their possible application for cancer imaging. Further studies are warranted to test the theranostic potential of NDG-Mn₃O₄ nanocomposites using animal models of cancer.

Recent progress of hierarchical MoS2 nanostructures for electrochemical energy storage

Hierarchical MoS2 nanostructures are of increasing importance in energy storage via batteries or supercapacitors. Herein, the various hierarchical MoS2 materials as electrochemical electrode are reviewed in detail by classifying the...

All-pH-Tolerant In-Plane Heterostructures for Efficient Hydrogen Evolution Reaction

Generally, electrocatalytic hydrogen evolution reaction (HER) by water splitting is a pH-dependent reaction, which limits the widespread harvesting of hydrogen energy. Herein, we present a simple way for chemical bonding of MoS₂ (002) planes and α-MoC {111} planes to form in-plane heterostructures capable of efficient pH-universal HER. Due to the lattice strain from mismatched lattice parameters between α-MoC and MoS₂, this catalyst changes the electronic configuration of the MoS₂ and thus acquires the favorable proton adsorption and desorption activity, suggested by the platinum (Pt)-like free Gibbs energy. Consequently, only a low 78 mV overpotential is needed to achieve the current density of 10 mA cm^-2 in acidic solution along with a favorable Tafel kinetic process with a Tafel slope of 38.7 mV dec^-1. Owing to the synergistic interaction between MoS₂ (002) planes and α-MoC {111} planes with strong water dissociation activities, this catalyst also exhibits high HER performances beyond that of Pt in neutral and alkaline. This work proves the advances of in-plane heterostructures and illustrates the production of low-cost but highly efficient pH-universal HER catalytic materials, promising for future sustainable hydrogen energy.

Two-Dimensional Transition Metal Chalcogenides for Alkali Metal Ions Storage

On the heels of exacerbating environmental concerns and ever-growing global energy demand, development of high-performance renewable energy-storage and -conversion devices has aroused great interest. The electrode materials, which are the critical components in electrochemical energy storage (EES) devices, largely determine the energy-storage properties, and the development of suitable active electrode materials is crucial to achieve efficient and environmentally friendly EES technologies albeit the challenges. Two-dimensional transition-metal chalcogenides (2D TMDs) are promising electrode materials in alkali metal ion batteries and supercapacitors because of ample interlayer space, large specific surface areas, fast ion-transfer kinetics, and large theoretical capacities achieved through intercalation and conversion reactions. However, they generally suffer from low electronic conductivities as well as substantial volume change and irreversible side reactions during the charge/discharge process, which result in poor cycling stability, poor rate performance, and low round-trip efficiency. In this Review, recent advances of 2D TMDs-based electrode materials for alkali metal-ion energy-storage devices with the focus on lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), potassium-ion batteries (PIBs), high-energy lithium-sulfur (Li-S), and lithium-air (Li-O₂ ) batteries are described. The challenges and future directions of 2D TMDs-based electrode materials for high-performance LIBs, SIBs, PIBs, Li-S, and Li-O₂ batteries as well as emerging alkali metal-ion capacitors are also discussed.

Flexible freestanding MoS2-based composite paper for energy conversion and storage

The construction of flexible electrochemical devices for energy storage and generation is of utmost importance in modern society. In this article, we report on the synthesis of flexible MoS2-based composite paper by high-energy shear force milling and simple vacuum filtration. This composite material combines high flexibility, mechanical strength and good chemical stability. Chronopotentiometric charge-discharge measurements were used to determine the capacitance of our paper material. The highest capacitance achieved was 33 mF·cm-2 at a current density of 1 mA·cm-2, demonstrating potential application in supercapacitors. We further used the material as a cathode for the hydrogen evolution reaction (HER) with an onset potential of approximately -0.2 V vs RHE. The onset potential was even lower (approximately -0.1 V vs RHE) after treatment with n-butyllithium, suggesting the introduction of new active sites. Finally, a potential use in lithium ion batteries (LIB) was examined. Our material can be used directly without any binder, additive carbon or copper current collector and delivers specific capacity of 740 mA·h·g-1 at a current density of 0.1 A·g-1. After 40 cycles at this current density the material still reached a capacity retention of 91%. Our findings show that this composite material could find application in electrochemical energy storage and generation devices where high flexibility and mechanical strength are desired.