NiO Nanoflowers for Non-Enzymatic Amperometric Detection of Glucose

The objective of this research is to demonstrate the effective processes enrolled in non enzymatic electrochemical glucose detection. Transition metal oxide nanoparticles have been an upcoming trend in the modern glucose sensors, thus giving rise to an era of non enzymatic glucose sensing. To begin, prepare a six millimolar solution of nickel chloride dihydrate in 10 milliliters of ethanol.

In a separate beaker, prepare 10 milliliters of a 3%polyvinylpyrrolidone or PVP solution in deionized water. Ultrasonicate the solution for five minutes at 40 kilohertz and 50 watts. Then mechanically stir it for an additional five minutes.

Repeat the ultrasonication and stirring cycle twice. Then mechanically stir it for an additional five minutes. Once the PVP is completely dissolved, use a pipette to add 10 milliliters of the PVP solution dropwise into 10 milliliters of the nickel precursor solution under vigorous stirring.

Continue stirring the mixture for 30 minutes after the PVP addition. Next, add 10 milliliters of an 18 millimolar urea solution prepared in a one-to-one mixture of deionized water and ethanol dropwise to the stirred mixture. Ensure that the total volume of the resulting solution is 30 milliliters.

Stir the complete solution for 10 minutes. Then transfer it into a polytetrafluoroethylene vessel and seal the vessel inside a stainless steel autoclave. Place the sealed autoclave in an electric oven, set at 160 degrees Celsius and maintain it for six to eight hours.

After completion, allow the autoclave to cool naturally to room temperature. Now, centrifuge the resultant product at 26.88 G to collect the green colored gelatinous nickel hydroxide precipitate. Decant the clear supernatant solvent and wash the precipitate with ethanol or deionized water at least three times.

Dry the washed precipitate at 70 degrees Celsius for 10 hours in an electric oven. Then place the dried powder in a box furnace set at 450 degrees Celsius for four hours to anneal and obtain the pure phase nickel oxide nanoflakes, which appear gray in color. Polish the glassy carbon electrode with 0.05 micrometer alumina nanoparticle slurry on a clean electrode polishing pad by moving it repeatedly in the shape of the numeral eight.

Rinse the electrode immediately with deionized water and ultrasonic it using a bath sonicator in isopropyl alcohol and deionized water for two minutes each at 40 kilohertz and 50 watts. Next, add a known mass of nickel oxide nanostructured flower powder, ranging from three to 15 milligrams to three milliliters of deionized water to prepare a nanoparticle suspension. Adjust the amount of powder so that the nanoparticle concentration ranges between one and five milligrams per milliliter.

Place the mixture in a bath ultrasonicator for 10 to 20 minutes to achieve a uniform dispersion and ensure that no precipitates or settled particles remain. Cast 10 microliters of the aliquot by dropping it onto the clean surface of the glassy carbon electrodes. Label the electrodes as NiO NFI to NiO NF5 depending upon the concentration of the loading solution, and allow the modified electrodes to dry at room temperature overnight for 10 to 12 hours.

Prepare a 0.5 weight percent binder solution in ethanol to compactly bind the nanoparticles onto the surface of the electrodes. Carefully drop cast six microliters of the binder solution onto each modified electrode and let them dry in air at room temperature for 30 minutes. Keep the prepared electrodes in a desiccator until further use.

Take 20 milliliters of 0.1 molar sodium hydroxide solution in the electrochemical cell to prepare the electro analytical solution. Use a three electrode setup to analyze the glucose concentration. Insert the silver or silver chloride electrode with three molar potassium chloride as the reference electrode and the platinum wire as the counter electrode.

Activate the nickel oxide nanostructured flower modified glassy carbon electrode by stabilizing it with 15 cycles of cyclic allometry. Set the potential window between 0 and 0.8 volts at a scan rate of 200 millivolts per second. Observe that the nickel three to two reduction peak potential typically appears around 0.4 to 0.6 volts.

After stabilization, run chronoamperometry for realtime glucose detection using the glassy carbon electrode. Firstly, establish the baseline by running chronoamperometry at the nickel reduction potential or glucose oxidation potential for 100 seconds. Once the base current is established, pause the chronoamperometric experiment by selecting the pause button in the software.

Next, prepare a two molar glucose stock solution for analysis. Lift the electrode stand and add 10 microliters of the glucose stock solution to the electro analytical solution to achieve a final glucose concentration of one millimolar with negligible change in the total volume. Stir the solution for 30 seconds to achieve uniform mixing.

Place the electrodes back into their previous positions and resume the chronoamperometric measurement after five seconds by pressing the resume button in the software. Choose a 32nd analysis window for the chronoamperometric detection of different glucose concentrations. Repeat the process of glucose addition and measurement to gradually increase the glucose concentration up to 15 millimolar and record the corresponding chronoamperometric responses.

Using a low loading concentration of the nanomaterial, optimize the potential window where the Faradaic reaction occurs. Perform an initial broad scan from negative one volt to positive one volt using cyclic voltammetry. Identify a smaller potential range where the Faradaic reaction occurs by locating the reduction and oxidation peaks in the cyclic voltammogram.

Collect the cyclic voltammograms for the electrochemical process within the selected potential range. Now, add a small amount of glucose, typically one millimolar to the electrochemical solution to generate distinct redox peaks. Observe that the glucose addition enhances the peak, corresponding to glucose oxidation, helping to resolve multiple peaks in the voltammogram.

Identify the antic peak potential corresponding to glucose oxidation, which changes with glucose concentration. Measure chrono am parametric responses slightly above this potential for accurate detection. Finally, once the potential window and glucose oxidation potential are determined, optimize the loading concentration by varying the nanomaterial suspension concentration drop cast onto the electrode.

The x-ray diffraction pattern of the nickel oxide nanoflowers showed distinct peaks corresponding to the 111, 200, 220, 311, and 222 planes of nickel oxide, confirming phase pure formation. The Raman spectrum of nickel oxide nanoflowers displayed characteristic peaks at 512, 692, 1073 and 1460 centimeter inverse, confirming the nickel oxide phase. The low magnification micrograph showed uniformly distributed flower-shaped nick oxide particles and the high magnification micrograph revealed marigold flower like spherical particles with an average diameter of approximately 0.91 micrometer.

The cyclic voltammograms for different loading concentrations of nickel oxide nano flowers showed increasing peak currents up to four milligrams per milliliter, after which they saturated. Chronoamperometric responses obtained for different nanomaterial loadings demonstrated that electrodes with four milligrams per milliliter loading showed the highest current response to glucose. The current response plotted against glucose concentration confirmed a higher slope for the four milligram per milliliter nickel oxide nanoflower electrode, indicating greater sensitivity.

The cyclic voltammogram of nickel oxide nanoflower coated electrodes recorded with and without two millimolar glucose revealed an enhancement of the nickel redox peak upon glucose addition. The chronoamperometric selectivity response indicated excellent discrimination against ascorbic acid, sucrose, fructose, and sodium chloride at 0.1 millimolar concentration. The chronoamperometric curves recorded across multiple cycles showed reproducible current responses, confirming electrode repeatability.

Almost all current glucometers in the market rely on enzymes for glucose sensing, NiO nanoflower catalyst is among the best materials for replacement of enzymes in glucose sensing. This video article paves the way for better understanding of procedures, especially for researchers starting afresh in the field of biosensors.