Preparation of nickel foam modified by multiwalled hollow spheres of NiCo2O4 as a promising non-enzymatic glucose sensor.

Nickel foam modified by hollow sphere NiCo2O4 particles was successfully prepared via a hydrothermal method using nanosphere SiO2 particles as the hard template for the hollow structure. Characterisation using SEM-EDX and TEM confirmed the structure as multiwalled hollow spheres with an average size of 270 nm, while characterisation using SEM, XRD, and XPS confirmed that the NiCo2O4 particles were attached on the surface of the nickel foam. BET analysis showed that the surface area of the synthesized NiCo2O4@Ni foam was nearly three times higher compared to that of the unmodified Ni foam. Investigation of the NiCo2O4-modified nickel foam as an electrode for the detection of glucose in sodium hydroxide solution showed high linearity of the anodic currents (R2 = 0.99) in the concentration range of 0-2.5 µM with sensitivity of 0.060 mA µM-1 and an estimated limit of detection of 0.060 µM. Excellent stability of the current response was also obtained with a relative standard deviation of 1.51% (n = 10). Furthermore, the developed sensor demonstrates strong applicability for glucose detection in real samples of human blood plasma, making it highly suitable for practical use. The results indicate that the material is promising for the further development of nickel-based sensors.

An Electrochemical Sensor of Theophylline on a Boron-Doped Diamond Electrode Modified with Nickel Nanoparticles.

Theophylline is a drug with a narrow therapeutic range. Electrochemical sensors are a potentially effective method for detecting theophylline concentration to prevent toxicity. In this work, a simple modification of a boron-doped diamond electrode using nickel nanoparticles was successfully performed for a theophylline electrochemical sensor. The modified electrode was characterized using a scanning electron microscope and X-ray photoelectron spectroscopy. Square wave voltammetry and cyclic voltammetry methods were used to study the electrochemical behavior of theophylline. The modified nickel nanoparticles on the boron-doped diamond electrode exhibited an electrochemically active surface area of 0.0081 cm2, which is larger than the unmodified boron-doped diamond's area of 0.0011 cm2. This modified electrode demonstrated a low limit of detection of 2.79 µM within the linear concentration range from 30 to 100 µM. Moreover, the modified boron-doped diamond electrode also showed selective properties against D-glucose, ammonium sulfate, and urea. In the real sample analysis using artificial urine, the boron-doped diamond electrode with nickel nanoparticle modifications achieved a %recovery of 105.10%, with a good precision of less than 5%. The results of this work indicate that the developed method using nickel nanoparticles on a boron-doped diamond electrode is promising for the determination of theophylline.

Electrochemical reduction of carbon dioxide to acetic acid on a Cu-Au modified boron-doped diamond electrode with a flow-cell system.

Boron-doped diamond (BDD) was modified with copper and gold particles by using an electrodeposition technique to improve its catalytic effect on CO2 reduction in a flow system. The system was optimized based on the production of formic acid by the electroreduction process. At the optimum applied potential of -1.0 V (vs. Ag/AgCl) and flow rate of 50 mL min-1, the copper-gold-modified BDD produced formic acid at the highest rate of 4.88 mol m-2 s-1 and a concentration of 15.93 ppm, while acetic acid was produced with a rate of 0.11 mol m-2 s-1 and a concentration of 0.47 ppm. An advantage of the flow system using the modified BDD was that it was found to accelerate the production rate of acetic acid as well as to decrease the reduction potential of CO2. Furthermore, better stability of the metal particles was observed when using mixed copper-gold modification on the BDD surface than single modification by either metal. The results indicated that a flow system is suitable to be employed for electroreduction of CO2 using the bimetal-modified BDD electrodes, especially with copper and gold as the modifying particles.