Probing the flat band potential and effective electronic carrier density in vertically aligned nitrogen doped diamond nanorods via electrochemical method

P-N Heterojunction Embedded CuS/TiO2 Bifunctional Photocatalyst for Synchronous Hydrogen Production and Benzylamine Conversion

The coupling of photocatalytic hydrogen production and selective oxidation of benzylamine is a topic of significant research interest. However, enhancing the bifunctional photocatalytic activity in this context is still a major challenge. The construction of Z-scheme heterojunctions is an effective strategy to enhance the activity of bifunctional photocatalysts. Herein, a p-n type direct Z-scheme heterojunction CuS/TiO2 is constructed using metal-organic framework (MOF)-derived TiO2 as a substrate. The carrier density is measured by Mott-Schottky under photoexcitation, which confirms that the Z-scheme electron transfer mode of CuS/TiO2 is driven by the diffusion effect caused by the carrier concentration difference. Benefiting from efficient charge separation and transfer, photogenerated electrons, and holes are directedly transferred to active oxidation and reduction sites. CuS/TiO2 also exhibits excellent bifunctional photocatalytic activity without noble metal cocatalysts. Among them, the H2 evolution activity of the CuS/TiO2 is found to be 17.1 and 29.5 times higher than that of TiO2 and CuS, respectively. Additionally, the yields of N-Benzylidenebenzylamine (NBB) are 14.3 and 47.4 times higher than those of TiO2 and CuS, respectively.

Disposable Paper-Based Biosensors: Optimizing the Electrochemical Properties of Laser-Induced Graphene

Laser-induced graphene (LIG) on paper substrates is a desirable material for single-use point-of-care sensing with its high-quality electrical properties, low fabrication cost, and ease of disposal. While a prior study has shown how the repeated lasing of substrates enables the synthesis of high-quality porous graphitic films, however, the process-property correlation of lasing process on the surface microstructure and electrochemical behavior, including charge-transfer kinetics, is missing. The current study presents a systematic in-depth study on LIG synthesis to elucidate the complex relationship between the surface microstructure and the resulting electroanalytical properties. The observed improvements were then applied to develop high-quality LIG-based electrochemical biosensors for uric acid detection. We show that the optimal paper LIG produced via a dual pass (defocused followed by focused lasing) produces high-quality graphene in terms of crystallinity, sp² content, and electrochemical surface area. The highest quality LIG electrodes achieved a high rate constant k₀ of 1.5 × 10^-2 cm s^-1 and a significant reduction in charge-transfer resistance (818 Ω compared with 1320 Ω for a commercial glassy carbon electrode). By employing square wave anodic stripping voltammetry and chronoamperometry on a disposable two-electrode paper LIG-based device, the improved charge-transfer kinetics led to enhanced performance for sensing of uric acid with a sensitivity of 24.35 ± 1.55 μA μM^-1 and a limit of detection of 41 nM. This study shows how high-quality, sensitive LIG electrodes can be integrated into electrochemical paper analytical devices.

Plasmon-Coupled Photocapacitor Neuromodulators

Efficient transduction of optical energy to bioelectrical stimuli is an important goal for effective communication with biological systems. For that, plasmonics has a significant potential via boosting the light-matter interactions. However, plasmonics has been primarily used for heat-induced cell stimulation due to membrane capacitance change (i.e., optocapacitance). Instead, here, we demonstrate that plasmonic coupling to photocapacitor biointerfaces improves safe and efficacious neuromodulating displacement charges for an average of 185% in the entire visible spectrum while maintaining the faradic currents below 1%. Hot-electron injection dominantly leads the enhancement of displacement current in the blue spectral window, and the nanoantenna effect is mainly responsible for the improvement in the red spectral region. The plasmonic photocapacitor facilitates wireless modulation of single cells at three orders of magnitude below the maximum retinal intensity levels, corresponding to one of the most sensitive optoelectronic neural interfaces. This study introduces a new way of using plasmonics for safe and effective photostimulation of neurons and paves the way toward ultrasensitive plasmon-assisted neurostimulation devices.

High-performance supercabatteries using graphite@diamond nano-needle capacitor electrodes and redox electrolytes

Supercabatteries have the characteristics of supercapacitors and batteries, namely high power and energy densities as well as long cycle life. To construct them, capacitor electrodes with wide potential windows and/or redox electrolytes are required. Herein, graphite@diamond nano-needles and an aqueous solution of Fe(CN)63-/4- are utilized as the capacitor electrode and the electrolyte, respectively. This diamond capacitor electrode has a nitrogen-doped diamond core and a nano-graphitic shell. In 0.05 M Fe(CN)63-/4- + 1.0 M Na2SO4 aqueous solution, the fabricated supercabattery has a capacitance of 66.65 mF cm-2 at a scan rate of 10 mV s-1. It is stable over 10 000 charge/discharge cycles. The symmetric supercabattery device assembled using a two-electrode system possesses energy and power densities of 10.40 W h kg-1 and 6.96 kW kg-1, respectively. These values are comparable to those of other energy storage devices. Therefore, diamond supercabatteries are promising for many industrial applications.

Effective Utilization of Waste Red Mud for High Performance Supercapacitor Electrodes

In recent years, metal oxide-based, inexpensive, stable electrodes are being explored as a potent source of high performance, sustainable supercapacitors. Here, the employment of industrial waste red mud as a pseudocapacitive electrode material is reported. Mechanical milling is used to produce uniform red mud nanoparticles, which are rich in hematite (Fe2O3), and lower amounts of other metal oxides. A comprehensive supercapacitive study of the electrode is presented as a function of ball-milling time up to 15 h. Ten-hour ball-milled samples exhibit the highest pseudocapacitive behavior with a specific capacitance value of ≈317 F g-1, at a scan rate of 10 mV s-1 in 6 m aqueous potassium hydroxide electrolyte solution. The modified electrode shows an extraordinary retention of ≈97% after 5000 cycles. A detailed quantitative electrochemical analysis is carried out to understand the charge storage mechanism at the electrode-electrolyte interface. The formation of uniform nanoparticles and increased electrode stability are correlated with the high performance. This work presents two significant benefits for the environment; in energy storage, it shows the production of a stable and efficient supercapacitor electrode, and in waste management with new applications for the treatment of red mud.

Conductive diamond: synthesis, properties, and electrochemical applications

This review summarizes systematically the growth, properties, and electrochemical applications of conductive diamond.