One-step-one-pot hydrothermally derived metal-organic-framework-nanohybrids for integrated point-of-care diagnostics of SARS-CoV-2 viral antigen/pseudovirus utilizing electrochemical biosensor chip

The COVID-19 pandemic has become a global catastrophe, affecting the health and economy of the human community. It is required to mitigate the impact of pandemics by developing rapid molecular diagnostics for SARS-CoV-2 virus detection. In this context, developing a rapid point-of-care (POC) diagnostic test is a holistic approach to the prevention of COVID-19. In this context, this study aims at presenting a real-time, biosensor chip for improved molecular diagnostics including recombinant SARS-CoV-2 spike glycoprotein and SARS-CoV-2 pseudovirus detection based on one-step-one-pot hydrothermally derived CoFeBDCNH₂-CoFe₂O₄ MOF-nanohybrids. This study was tested on a PalmSens-EmStat Go POC device, showing a limit of detection (LOD) for recombinant SARS-CoV-2 spike glycoprotein of 6.68 fg/mL and 6.20 fg/mL in buffer and 10% serum-containing media, respectively. To validate virus detection in the POC platform, an electrochemical instrument (CHI6116E) was used to perform dose dependent studies under similar experimental conditions to the handheld device. The results obtained from these studies were comparable indicating the capability and high detection electrochemical performance of MOF nanocomposite derived from one-step-one-pot hydrothermal synthesis for SARS-CoV-2 detection for the first time. Further, the performance of the sensor was tested in the presence of Omicron BA.2 and wild-type D614G pseudoviruses.

Hydrothermal Synthesis of Binder-Free Metallic NiCo2O4 Nano-Needles Supported on Carbon Cloth as an Advanced Electrode for Supercapacitor Applications

It is of great significance to design electrochemical energy conversion and storage materials with excellent performance to fulfill the growing energy demand. Bimetallic cobalt/nickel-based electrode materials exhibit excellent electrical conductivity compared to mono oxides. However, their potential as electrode materials for high-performance supercapacitors (SCs) is limited because of their poor cycling stability and high-capacity fading. This work demonstrates the synthesis of binder-free bimetallic NiCo₂O₄ nano-needles supported on CC (NCO@CC) via a facile and scalable hydrothermal process. Excellent electrical conductivity and interconnected nanostructure of NCO@CC nano-needles provide the fast transfer of electrons with numerous channels for ion diffusion. Owing to such features, the binder-free NCO@CC electrode for SC discloses excellent specific capacitance (1476 Fg⁻¹ at 1.5 Ag⁻¹) with 94.25% capacitance retention even after 5000 cycles. From these outstanding electrochemical performances, it can be inferred that NCO@CC nano-needle array-structured electrodes may be potential candidates for SC applications.

Fabrication of composite material of RuCo2O4 and graphene on nickel foam for supercapacitor electrodes

Supercapacitors are energy storage devices with the advantage of rapid charging and discharging, which need a higher specific capacitance and superior cycling stability. Hence, a composite material consisting of RuCo₂O₄ and reduced graphene oxide with a nanowire network structure was synthesized on nickel foam using a one-step hydrothermal method and annealing process. The nanowire network structure consists of nanowires with gaps that provide more active sites for electrochemical reactions and shorten the diffusion path of electrolyte ions. The prepared electrodes exhibit outstanding electrochemical performance with 2283 F g⁻¹ at 1 A g⁻¹. When the current density is 10 A g⁻¹, the specific capacitance of the electrodes is 1850 F g⁻¹, which maintains 81% of the initial specific capacitance. In addition, the prepared electrodes have a long-term cycling life with capacitance retention of 92.60% after 3000 cycles under the current density of 10 A g⁻¹. The composite material is a promising electrode material for high-performance supercapacitors.

The RuCo₂O₄/rGO@NF composite electrode has been prepared by a one-step hydrothermal method and annealing process, with high specific capacitance and excellent cycle stability.

Reagent-assisted hydrothermal synthesis of NiCo2O4 nanomaterials as electrodes for high-performance asymmetric supercapacitors

Spinel nickel cobaltate nanoneedle arrays in situ synthesized by a CTAB assisted hydrothermal method show an energy density of 22.5 W h kg⁻¹ at 800 W kg⁻¹.

A hybrid NiCo2O4@NiMoO4 structure for overall water splitting and excellent hybrid energy storage

In this study, a two-step hydrothermal method is used to prepare NiCo2O4@NiMoO4 nanoscale materials for periodic stability supercapacitors. The synthesized product can be directly used as the electrode material of the supercapacitor, and its specific capacitance is 685.7 C g-1. The composite electrode NiCo2O4@NiMoO4 is used as the positive electrode and the hybrid capacitor is assembled. Meanwhile, at the power density of 4050 W kg-1, the energy density is 96.3 W h kg-1, and the capacitance retention is 100% after 10 000 cycles. At the same time, when the composite is used as a catalyst, it exhibits OER overvoltage (300 mV), HER overvoltage (170 mV) and a low battery voltage of 1.65 V at 10 mA cm-2. After 14 hours of long-term use, NiCo2O4@NiMoO4 maintained good stability, indicating that its structure further improved the electrochemical performance, providing a great advantage for the study of low-cost electrode materials for overall water splitting.

Fabrication of hierarchical core/shell MgCo2O4@MnO2 nanowall arrays on Ni-foam as high-rate electrodes for asymmetric supercapacitors

Design and fabrication of a hierarchical core/shell MgCo₂O₄@MnO₂ nanowall arrays on Ni-foam by a facile two-step hydrothermal method. The electrochemical measurements prove these composites with MnO₂ definitely offer better supercapacitive performance of the MgCo₂O₄ electrode material. The nanowall structure provides more active sites and charge transfer during the Faradic reaction. The MgCo₂O₄@MnO₂ nanowall shows an excellent electrochemical performance (852.5 F g^-1 at 1 A g^-1). The asymmetric supercapacitor is composed of the MgCo₂O₄@MnO₂ nanowall and the activated carbon (AC). The energy densities of the asymmetric supercapacitor device can keep up 67.2 Wh·kg^-1 at 5760.0 W·kg^-1. The MgCo₂O₄@MnO₂ nanowall shows excellent supercapacitive performance and has a great potential for more research and application in the asymmetric supercapacitor devices field.

Mesoporous NiCo2O4 nanoneedle arrays as supercapacitor electrode materials with excellent cycling stabilities

An assembled supercapacitor using a mesoporous NiCo₂O₄ electrode as the positive electrode achieves 140.6% capacity retention which is attained after 8000 cycles at 10 mA cm⁻².

Nitrogen, sulfur and phosphorus-codoped carbon with a tunable nanostructure as an efficient electrocatalyst for the oxygen reduction reaction

The N/S/P-codoped carbon catalysts with varied nanostructures were facilely prepared. The mesoporous carbon nanosheets exhibit the optimal catalytic activity for ORR.

Tuning band gaps and optical absorption of BiOCl through doping and strain: insight form DFT calculations

Doping and strain were used to tune the electronic structures and optical properties of BiOCl using first principle calculations.

Mesoporous NiCo2O4 Nanoplates on Three-Dimensional Graphene Foam as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

Catalysts for the oxygen reduction reaction (ORR) are highly important in fuel cells and metal-air batteries. Cheap ORR catalysts with ultrahigh electrochemical activity, selectivity, and stability are extremely desirable but still remain challenging. Herein, mesoporous NiCo₂O₄ nanoplate (NP) arrays on three-dimensional (3D) graphene foam are shown to be a highly economical ORR catalyst. This mesoporous mixed-valence oxide can provide more electrocatalytic active sites with increased accessible surface area. In addition, graphene-foam-supported NiCo₂O₄ NP arrays have a 3D hierarchical porous structure, which is of great benefit to ion diffusion and electron transfer. As a result, the mesoporous NiCo₂O₄ NP arrays/graphene foam catalyst exhibits outstanding ORR performance with the four-electron reduction of O₂ to H₂O in alkaline media. Furthermore, the mesoporous catalyst shows enhanced electrocatalytic activity with a half-wave potential of 0.86 V vs RHE and better stability compared with a commercial Pt/C catalyst.

Three-dimensional NiCo2O4/NiCo2S4hybrid nanostructure on Ni-foam as a high-performance supercapacitor electrode

The high performance electrode for supercapacitor based on NiCo₂O₄/NiCo₂S₄hybrid nanostructures on Ni-foam were successfully fabricated by a facile pH-controlled ammonia evaporation technique.

Facile synthesis of three-dimensional NiCo2O4 with different morphology for supercapacitors

The morphology of NiCo₂O₄ can be controlled by changing the kinds of alkali source and the addition of NH₄F, influencing its electrochemical properties.