ZnO-NPs/rGO/SPCE-modified electrode for early detection of Ganoderma boninense in oil palm trees
Ganoderma boninense is a major disease that infects oil palm trees. This problem has caught researchers’ attention all around the world, especially those from Asian countries as Ganoderma boninense is difficult to trace in its early stage. Undoubtedly, many researchers...
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| Format: | Thesis |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/85240/1/ITMA%202019%2010%20-%20ir.pdf |
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| Summary: | Ganoderma boninense is a major disease that infects oil palm trees. This problem has
caught researchers’ attention all around the world, especially those from Asian countries as
Ganoderma boninense is difficult to trace in its early stage. Undoubtedly, many researchers
have lent a hand by suggesting ways to diagnose the disease through the introduction
of many methods to detect symptoms related to the Ganoderma disease, including
tomography, selective media, Indirect Enzyme-linked Immunosorbent Assay (ELISA) and
polymerase chain reaction (PCR). However, these diagnostic techniques are less accurate,
time-consuming and lead to cost increments. Therefore, another method to detect Ganoderma
boninense at a faster, lower cost and higher accuracy was introduced which is through the
use of electrochemical sensors. Initially, electrode modification was done by reducing graphene
oxide (GO) to reduced graphene oxide (rGO). Subsequently, the addition of zinc oxide
nanoparticle (ZnO-NPs) was electrodeposited on top of it using the
electrodeposition method. Both modifiers were chosen as they have been acknowledged to
have large surface areas to interact with analytes, and have great electroconductivity. In this
study, this disposable modified SPCE was used as a sensing material in order to detect
secondary metabolites acting as possible biomarkers for the Ganoderma boninense disease in
healthy and infected leaves at the 14 and 30 day periods. It is because secondary
metabolites are produced once oil palm trees are infected by Ganoderma boninense. The
combination of physical and electrochemical characterisation of graphene oxide (GO) before and
after reduction together with the deposition of zinc oxide nanoparticles (ZnO-NPs) were
observed using field emission scanning electron microscopy (FESEM), energy dispersive x-ray
(EDX), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and cyclic
voltammetry (CV) to reveal the successful modification of ZnO-NPs/rGO/SPCE.
As a consequence, the electrochemical analysis presented a current increment in each modification
higher than the bare SPCE due to electrocatalytic activity. Afterwards, the electrochemical
signals from secondary metabolites were indicated from differential pulse voltammetry
techniques (DPV) under optimum conditions. ZnO-NPs/rGO/SPCE established a good correlation
coefficient (R²) of both healthy and infected oil palm after 14 days and 30 days (R² = 0.9691, R² =
0.9652, R² = 0.9905 and R² = 0.9710) with detection limits of 1.52 ppm,
1.58 ppm, 3.20 ppm and 3.02 ppm respectively. Consequently, the outstanding sensing performance
of ZnO-NPs/rGO/SPCE in the detection of secondary metabolites can be applied to control the Ganoderms boninensense disease at the
earlier stage before spreading out. |
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