A group of researchers has successfully developed a distinctive near-spherical ZnO nanostructure using solvents composed of polyethylene glycol-400 (PEG-400), according to a recent study published in the journal Colloids and Surfaces B: Biointerfaces.
Study: Non-enzymatic nitrite amperometric sensor fabricated with near-spherical ZnO nanomaterial. Image Credit: LALS STOCK/Shutterstock.com
The researchers reported that the near-spherical ZnO nanomaterial might be an exceptional option to make a nitrite amperometric sensor, which could have a lot of applications in the food industry and environmental control.
Limitations of Nitrite (NO2) Compound
Overuse of the nitrite (NO2) chemical, a major component of food antiseptics and a generator of economic nitrogen fertilizer, may harm human health and the environment. The maximum limit of NO2 set by the World Health Organization (WHO) is 8.72-8.3 M; hence there is a compelling need to create a reliable technology to detect NO2.
Effective NO2 Detection Technique
Several analytical techniques for determining NO2 have been developed in recent decades, including luminescence, colorimetric testing, Raman spectroscopy, chromatography approaches, gel filtration, and electrochemical methods.
The electrochemical method has attracted a lot of attention because of its benefits of ease of use, cheap cost, and quick reaction time. However, determining NO2 through bare GCE has significant drawbacks, including insensitivity, limited selectivity, slow kinetics, and a considerable overpotential.
Worse, the sensor's limited selectivity and sensitivity made reliable nitrite detection more difficult and demanding, particularly in real applications involving complex matrices containing large amounts of interfering chemicals.
Some appropriate electrode modifiers must be produced to address the foregoing drawbacks to acquire desired sensing properties. Unfortunately, owing to the difficulties in immobilizing enzymes and establishing good electrical connections between enzyme and electrode, detectors dependent on nitrite-reduced electrodes are severely restricted for practical use.
Synthesis of Non-Enzymatic Electrochemical Sensors
Manufacturing of non-enzymatic detectors has been viewed as a promising strategy in recent years, and nanostructures made of metal oxides, such as ZnO, TiO2, Fe2O3, Co3O4, and Cu2O, have received a lot of attention because of their phenomenal thermal conductivity, low toxicity, processability, and desirable reliability.
Because of its board band gap of 3.33-3.41 eV, ZnO is described as the best nanostructure. It may display extraordinary electrochemical features, such as increased ions transport capacity and huge surface area.
Several intriguing ZnO-based nanomaterials have been created and successfully employed to build nitrite electrochemical sensors throughout the previous decade, confirming the prospective application of ZnO nanoparticles. These nitrite sensors, on the other hand, have several flaws, such as a restricted accuracy limit, a high limit of detection, and low precision. As a result, there is still much room to improve the nitrite detecting capabilities of ZnO-based nanomaterials.
Strategies to Enhance the Nitrite Sensing Property of ZnO Electrode
The researchers started to consider how they may increase the nitrite sensing capabilities of the ZnO electrode without resorting to complex organic manufacturing techniques or precious-metallic nanomaterials. It is well established that the shape of nanomaterials has a significant impact on their electrochemical sensing capabilities. As it supplies more active groups for the enzymes, the increased surface area of nanomaterials is particularly conducive to speeding electron transport during electrochemical sensing.
Following these results, the authors hypothesized that constructing the nitrite sensor with a distinct ZnO nanostructure described by more homogeneity, improved scattering, and narrow size distribution would be preferable.
Obtaining the desired ZnO nanostructure, on the other hand, proved to be a significant issue. It was observed that the shape of ZnO materials may be effectively controlled by using various polarity solvents, such as alcohol, ethanol, water, and their combined solvents.
As a result, the researchers conducted further research using several other more unique solvents with suitable neutrality and viscosity. Utilizing the optimal mixed solutions (volume ratio of PEG-400 to the water of 12:1) in the solvothermal technique, they effectively created the desired nanostructured ZnO, i.e. the near-spherical ZnO.
Unlike other oxide materials or precious metal nanoparticles previously described, such nanostructured ZnO had superior homogeneity.
Research Findings and Conclusion
A near-spherical ZnO was effectively synthesized in optimal mixed solvents (volume proportion of PEG-400 to the water of 12:1) using the solvothermal technique, and an electrochemical nitrite detection method based on near-spherical ZnO/GCE was subsequently achieved. Because of the peculiar morphology of ZnO, the sensor had a wide linearity range, reduced Latency, better responsiveness, and good anti-interference capabilities.
For the measurement of nitrite in the authentic food industry, the near-spherical ZnO/GCE demonstrates a good recovery. The nitrite sensor may have a bright future in the area of water environmental monitoring and food analysis.
Continue reading: How are Nanocatalysts Used for Environmental Applications?
Reference
Cheng, Z. et al. (2021). Non-enzymatic nitrite amperometric sensor fabricated with near-spherical ZnO nanomaterial. Colloids and Surfaces B: Biointerfaces. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0927776521007591
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