Cobalt nanoparticles intercalation coupled with tellurium-doping MXene for efficient electrocatalytic water splitting.

Nowadays, the inherent re-stacking nature and weak d-p hybridization orbital interactions within MXene remains significant challenges in the field of electrocatalytic water splitting, leading to unsatisfactory electrocatalytic activity and cycling stability. Herein, this work aims to address these challenges and improve electrocatalytic performance by utilizing cobalt nanoparticles intercalation coupled with enhanced π-donation effect. Specifically, cobalt nanoparticles are integrated into V2C MXene nanosheets to mitigate the re-stacking issue. Meanwhile, a notable charge redistribution from cobalt to vanadium elevates orbital levels, reduces π*-antibonding orbital occupancy and alleviates Jahn-Teller distortion. Doping with tellurium induces localized electric field rearrangement resulting from the changes in electron cloud density. As a result, Co-V2C MXene-Te acquires desirable activity for hydrogen evolution reaction and oxygen evolution reaction with the overpotential of 80.8 mV and 287.7 mV, respectively, at the current density of -10 mA cm-2 and 10 mA cm-2. The overall water splitting device achieves an impressive low cell voltage requirement of 1.51 V to obtain 10 mA cm-2. Overall, this work could offer a promising solution when facing the re-stacking issue and weak d-p hybridization orbital interactions of MXene, furnishing a high-performance electrocatalyst with favorable electrocatalytic activity and cycling stability.

Nickel/Cobalt Molybdate Hollow Rods Induced by Structure and Defect Engineering as Exceptional Electrode Materials for Hybrid Supercapacitor.

Oxygen defects and hollow structures positively impact pseudocapacitive properties of diffusion/surface-controlled processes, a component of critical importance when building high-performance supercapacitors. Hence, we fabricated hollow nickel/cobalt molybdate rods with O-defects (D-H-NiMoO4 @CoMoO4 ) through a soft-template and partial reduction method, enhancing D-H-NiMoO4 @CoMoO4 's electrochemical performance, yielding a specific capacitance of 1329 F g-1 , and demonstrating excellent durability with 95.8 % capacity retention after 3000 cycles. D-H-NiMoO4 @CoMoO4 was used as the positive electrode to construct an asymmetric supercapacitor, displaying an energy density of up to 34.13 Wh kg-1 and demonstrating good predisposition towards practical applications. This work presents an effective approach to fabricate and use hollow nickel/cobalt molybdate rods with O-defects as pseudocapacitor material for high-performance capacitive energy storage devices.

3D Hollow Flower-like CoWO4 Derived from ZIF-67 Grown on Ni-foam for High-Performance Asymmetrical Supercapacitors.

A three-dimensional (3D) hollow CoWO4 composite grown on Ni-foam (3D-H CoWO4 /NF) based on a flower-like metal-organic framework (MOF) is designed by utilizing a facile dipping and hydrothermal approach. The 3D-H CoWO4 /NF not only possesses large specific areas and rich active sites, but also accommodates volume expansion/contraction during charge/discharge processes. In addition, the unique structure facilitates fast electron/ion transport of 3D-H CoWO4 /NF. Meanwhile, a series of characterization measurements demonstrate the appropriate morphology and excellent electrochemical performance of the material. The 3D-H CoWO4 /NF possesses a high specific capacitance of 1395 F g-1 , an excellent cycle stability with 89% retention after 3000 cycles and superior rate property. Furthermore, the 3D-H CoWO4 /NF can be used as a cathode to configurate an asymmetric supercapacitor (ASC), and 3D-H CoWO4 /NF//AC shows a good energy density (29.0 W h kg-1 ). This work provides a facile method for the preparation of 3D-hollow electrode materials with high electrochemical capability for advanced energy storage devices.

A novel dual-tasking hollow cube NiFe2O4-NiCo-LDH@rGO hierarchical material for high preformance supercapacitor and glucose sensor.

Binary transition metal oxides as electroactive materials have continuously aroused grumous attention due to their high theoretical specific capacitance, high valtage window, and multiple oxidation states. However, the tiny specific surface area, poor conductivity and unsatisfactory cycle stability limit their practical application. Hence, a synthetic strategy is designed to fabricate a dual-tasking hollow cube nickel ferrite (NiFe2O4) - based composite (NiFe2O4-NiCo-LDH@rGO) with hierarchical structure. The composite is constructed by firstly preparing hollow NiFe2O4 from cube-like Ni - Fe bimetallic organic framework (NiFe-MOF), and then integrating nickel cobalt layered double hydroxide (NiCo-LDH) nanowires, together with reduced graphene oxide (rGO) via pyrolysis in conjuction with hydrothermal method. The NiFe2O4 possessing cubic hollow structure contributes to a huge accessible surface area, meanwhile alleviates large volume expansion/contraction effect, which facilitates suffcient permeation of the electrolyte and rapid ion/charge transport, and results in high cycling stability. The introduction of layered NiCo-LDH results in hierarchical structure and thus offers maximum contact areas with electrolyte, which heightens the specific capacitance of obtained composite and enhances the electro-catlytic activity towards oxidation of glucose. Furthermore, rGO layer greatly improves the electrical conductivity and ion diffusion/transport capability of composite. Benefiting from the unique structure and individual components of NiFe2O4-NiCo-LDH@rGO composite, the electrode delivers a high specific capacitance (750 C g-1) and superb durability. Simultaneously, the asymmetrical device based on NiFe2O4-NiCo-LDH@rGO as positive electrode delivers remarkable energy density (50 Wh kg-1). Moreover, NiFe2O4-NiCo-LDH@rGO exhibits good sensing performance with a sensitivity of 111.86 µA/µM cm-2, the wide linear range of 3.500 × 10-5 - 4.525 × 10-3 M, and the detection limit of 12.94 × 10-6 M with a signal to noise ratio of 3. Consequently, the NiFe2O4-NiCo-LDH@rGO could provide a prospective notion constructing bifunctional materials with hollow-cube hierarchical structure in the field of supercapacitors and electrochemical sensors.

Facile Dual-Ligand Modulation Tactic toward Nickel-Cobalt Sulfides/Phosphides/Selenides as Supercapacitor Electrodes with Long-Term Durability and Electrochemical Activity.

The use of high electrochemical active binary nickel-cobalt sulfides/phosphides/selenides (Ni-Co-X, X = S, P, Se) as electrochemical energy storage materials still has a space for improvement because they become electrochemically unstable during long-term use. Herein, a facile and cost-effective dual-ligand synergistic modulation tactic is described to substantially improve the durability of Ni-Co-X (X = S, P, Se) at the atomic level by partially substituting S, P, and Se ligands into the nickel-cobalt hydroxide precursor, respectively. Remarkably, the dual-ligand electrodes on Ni-foam achieve superior durability and high electrochemical activity when used as positive electrodes in supercapacitors. Impressively, the density functional theory calculations demonstrate that the OH ligand in NiCo2(MOH)x (M = S, P, Se) could attract electrons from metal-S/metal-P/metal-Se bonds to the metal-O bond, enhancing the binding energy of metal-S/metal-P/metal-Se bonds and improving the long-term durability of Ni-Co-X (X = S, P, Se) in alkaline electrolytes. Moreover, OH and S/P/Se ligands could effectively alter the electron structure and result in favorable electrochemical activity. Overall, this tactic could offer an exciting avenue to achieve long-term durability and electrochemical activity of supercapacitor electrodes simultaneously.

An image-processing strategy to extract important information suitable for a low-size stimulus pattern in a retinal prosthesis.

BACKGROUND: A retinal prosthesis is designed to help the blind to obtain some sight. It consists of an external part and an internal part. The external part is made up of a camera, an image processor and an RF transmitter. The internal part is made up of an RF receiver, implant chip and microelectrode. METHODS: Currently, the number of microelectrodes is in the hundreds, and we do not know the mechanism for using an electrode to stimulate the optic nerve. A simple hypothesis is that the pixels in an image correspond to the electrode. The images captured by the camera should be processed by suitable strategies to correspond to stimulation from the electrode. Thus, it is a question of how to obtain the important information from the image captured in the picture. Here, we use the region of interest (ROI), a useful algorithm for extracting the ROI, to retain the important information, and to remove the redundant information. RESULTS: This paper explains the details of the principles and functions of the ROI. Because we are investigating a real-time system, we need a fast processing ROI as a useful algorithm to extract the ROI. Thus, we simplified the ROI algorithm and used it in an outside image-processing digital signal processing (DSP) system of the retinal prosthesis. CONCLUSION: The results show that our image-processing strategies are suitable for a real-time retinal prosthesis and can eliminate redundant information and provide useful information for expression in a low-size image.

SFRP1 and SFRP2 suppress the transformation and invasion abilities of cervical cancer cells through Wnt signal pathway.

OBJECTIVES: Aberrant activation of the Wnt/beta-catenin signaling pathway is common in human cancers, including cervical cancer. The secreted frizzled-related proteins (SFRPs) function as Wnt antagonists and play important implications in carcinogenesis. Recently, we have shown that SFRP1 and SFRP2 are frequently downregulated through promoter hypermethylation. However, the function of SFRP1 and SFRP2 in cervical cancer remains unclear. METHODS: To improve our understanding of the role of SFRP1 and SFRP2 in cervical cancer cells, we use overexpression or shRNA approach in cervical cancer cell lines. RESULTS: Restoration of the expression of SFRP1 and SFRP2 attenuated Wnt signaling in CaSki cells, decreased abnormal accumulation of free beta-catenin in the nucleus, and suppressed cancer cell growth. In addition, different statuses of beta-catenin accumulation in the cytoplasm of CaSki or HeLa3rd cells were observed, suggesting that different Wnt pathways are executed. Furthermore, we demonstrated that SFRP1 and SFRP2 enhance the expression of the epithelial marker E-cadherin, through inhibition of the expression of SLUG, TWIST and SNAIL, three transcription factors involved in the epithelial mesenchymal transition (EMT) program. Finally, in a xenograft animal model, we showed that SFRP1 suppresses tumorigenicity of cancer cells in vivo. CONCLUSIONS: Taken together, these data strongly suggest that epigenetic silencing of SFRP genes leads to oncogenic activation of the Wnt pathway and contributes to cervical cancer progression through the EMT program.