Functionalization Of Zinc Oxide Nanorods For Glucose Biosensor Application

Electrochemical based glucose biosensors are of interest owing to its simplicity, portable, low cost and does not require specialize personnel. However, this type of biosensors suffers from low sensitivity owing to indirect electron transfer and decrease in long term stability due to enzyme denaturation. Therefore, modification of electrode for electrochemical based glucose biosensors could overcome these problems. Nanostructure electrodes could enhance the performance of glucose biosensors owing to high surface area and biocompatibility with glucose oxidase (GOx) enzyme. In this work, zinc oxide nanorods (ZnO NRs) was successfully synthesized by hydrothermal method on indium tin oxide (ITO) seeded substrates which was further used as electrodes for glucose biosensor. Field emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD) were used to analyze the morphology and structural properties of synthesized ZnO NRs. Homogeneous density and well-aligned of ZnO NRs was obtained when seed films were annealed at 500 °C and hydrothermally grown for 4 hours. The electrochemical properties of modified electrodes were studied by cyclic voltammetry (CV) and amperometric analysis. The parameters influencing the enzyme activity and modified electrodes performance were studied: electrolyte pH, electrolyte temperature, Nafion concentration and GOx enzyme concentration. The modified electrode was designated as Nafion/GOx/ZnONRs/ZnO/ITO. 5 mg/mL of GOx concentration was chosen as the optimum concentration for immobilization on ZnO NRs electrode with high sensitivity of 23.772 μA/mM.cm2. The performance of the prepared electrode when two different immobilization techniques (physical adsorption and cross linking) was employed and compared. ZnO NRs surface was functionalized with glutaraldehyde (cross linking reagent) first before GOx was immobilized and was designated as Nafion/GOx-glutaraldehyde/ZnONRs/ZnO/ITO electrode. Cross-linked GOx electrode showed the best performance with the sensitivity of 32.24 compared to only 23.77 μA/mM.cm2 for physical adsorption GOx electrode. The produced ZnONRs/ITO electrode was also decorated with gold nanoparticles (AuNPs) and platinum nanodendrites (PtNDs). An average diameter of ~40 nm and ~42 nm of AuNPs and PtNDs, respectively, were successfully decorated on ZnO NRs via drop casting method. The sensitivity of Nafion/GOx/ZnONRs/ZnO/ITO, Nafion/GOx/AuNPs/ZnONRs/ZnO/ITO and Nafion/GOx/PtNDs/ZnONRs/ZnO/ITO electrodes was 32.24, 54.51 and 98.34 μA/mM.cm2, respectively. High sensitivity of Nafion/GOx/PtNDs/ZnONRs/ZnO/ITO electrode was due to properties of catalytic properties metallic nanoparticle. With high sensitivity of 98.34 μA/mM.cm2 and low LOD of 0.03 mM Nafion/GOx/PtNDs/ZnONRs/ZnO/ITO electrode was chosen as the best electrode for glucose biosensor. The produced modified electrodes showed excellent performance in human blood samples

Feasibility Study Of Zno Nanorods For Sensor Application

A field study was conducted to evaluate the effects of three insecticides (abamectin, malathion and diafenthiuron) on the interactions between Bemisia tabaci (Homoptera: Aleyrodidae) the brinjal pest, and the parasitoid Encarsia hitam (Hymenoptera: Aphelinidae), as well as on plant performances and fruit production. All insecticides were applied weekly at recommended doses over two brinjal cropping periods. Overall results showed high total numbers of whitefly on untreated plants in the first (14.08 ± 1.44 per leaf) and second (17.50 ± 4.65 per leaf) cropping periods compared to plants that were treated with abamectin (13.88 ± 3.32), malathion (9.80 ± 2.19 per leaf) and diafenthiuron (10.40 ± 2.41 per leaf) in the first crop and in second crop with 15.65 ± 5.42, 8.35 ± 2.79 and 9.48 ± 2.3 per leaf respectively. Malathion and diafenthiuron were the most effective insecticides that reduced whitefly populations below economic threshold level (ETL). Percentages of parasitism was high on whitefly nymphs in untreated control plants in the first and second cropping periods (3.17% - 12.82%) and (0.52% - 10.00%) respectively compared with insecticide-treated plants (0.62% - 12.50%) and (1.01% - 8.00%) respectively. All insecticides affected the parasitization of whitefly although no significance difference was observed among treatments

Formation of ZnO nanorods via low temperature hydrothermal method for enzymatic glucose sensor

In this study, zinc oxide (ZnO) nanorod arrays were synthesized using a simple hydrothermal reaction on a ZnO seeds/ITO substrate and applied for the fabrication of enzymatic glucose sensor. ZnO nanorod matrix provided a favourable environment for the immobilization of glucose oxidase (GOx) and introduced a shuttling way for electronic communication between GOx and electrode. The performance of different aspect ratio of ZnO nanorods that was produced by varying hydrothermal reaction time was studied. The aspect ratio of ZnO influenced the GOx enzyme immobilization. The morphology and structure of prepared ZnO nanorods were characterized by employing scanning electron microscopy (SEM), and X-ray powder diffraction (XRD). Electrochemical measurements of the sensor showed a reproducible sensitivity of 2.06 μA/cm2mM for ZnO matrix grown for 4 h with the aspect ratio of 8.0

I–V curves for the ZnO film and ZnO nanorod sensors under UV illumination (λ = 375 nm).

<p>I–V curves for the ZnO film and ZnO nanorod sensors under UV illumination (λ = 375 nm).</p

Synthesis parameters of ZnO nanorods using hydrothermal method.

<p>+ is denoted as constant parameters.</p

FESEM images of ZnO nanorods formed at different zinc nitrate concentrations: A) 0.05, B) 0.1, C) 0.2, D) 0.3, and E) 0.4 M.

<p>The samples were hydrothermally grown for 4 h at 80°C.</p

I–V curves of ZnO nanorods grown on seeds heat treated at different temperatures under UV illumination (λ = 375 nm).

<p>I–V curves of ZnO nanorods grown on seeds heat treated at different temperatures under UV illumination (λ = 375 nm).</p

FESEM images of ZnO nanorods grown on seeds heat treated at different temperatures: A) 250, B) 300, C) 350, D) 400, and E) 450°C.

<p>The samples were hydrothermally grown for 4 h at 80°C.</p