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Publication

A gold nanoparticles coated unclad single mode fiber-optic sensor based on localized surface plasmon resonance

(Nature Research, 2023)

Makram A. Fakhri

;

Evan T. Salim

;

Sara M. Tariq

;

Raed Khalid Ibrahim

;

Forat H. Alsultany

;

Ali. A. Alwahib

;

Sarmad Fawzi Hamza Alhasan

;

Subash Chandra Bose Gopinath

;

Zaid T. Salim

;

Uda Hashim

In the last few decays, the fiber-optic was employed in the field of sensing because of its benefits in contrast to other types of sensors such as small size, easy to fabricate, high response, and flexibility. In this study, unclad single mode fiber-optic sensor is proposed to operate at 650 nm wavelength. COMSOL Multiphysics 5.1 finite element method (FEM) is used to design the sensor and tested it theoretically. The middle portion of the fiber cladding is removed and replaced by gold nanoparticles (Au NPs) of 50 nm thickness. Analytic layer of 3 μm thickness was immersed in different liquids in range of refractive index (RI) from 1.000281 to 1.39. These liquids are NaCl Deionized (DI) water solution, sucrose-Deionized (DI) water solution, and glycerol solution Deionized (DI) water. It was found that the highest obtained sensitivity and resolution are for glycerol-DI water solution with value of 3157.98 (nm/RIU) and 3.16 × 10–5 (RIU), respectively. Furthermore, it is easy to fabricate and of low cost. In experiments, pulsed laser ablation (PLA) was used to prepare Au NPs. X-ray diffraction (XRD) shown that the peak of the intensity grew as the ablated energy increased as well as the structure crystallization. Transmission electron microscopy (TEM) revealed an average diameter of 30 nm at the three ablated energies, while X-ray spectroscopy (EDX) spectrum has indicated the presence of Au NPs in the prepared solution. The photoluminescence (PL) and ultraviolet–visible UV–Vis transmission were used to study the optical properties of the prepared Au NPs. An optical spectrum analyzer was used to obtain the sensor's output results. It has shown that best intensity was obtained for sucrose which confined with theoretical results. © 2023, The Author(s).

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Publication

A novel disposable biosensor based on SiNWs/AuNPs modified-screen printed electrode for dengue virus DNA oligomer detection

( 2015)

Jahwarhar Izuan Abd Rashid

;

Nor Azah Yusof

;

Jaafar Abdullah

;

Uda Hashim

;

Reza Hajian

In this paper, a disposable screen-printed gold electrode (SPGE) utilized of silicon nanowires (SiNWs) and gold nanoparticles as sensing material was fabricated for detection of DNA oligomers related to dengue virus. First, SiNWs/AuNPs-SPGE was developed by the dispersion of SiNWs in 3-aminopropyltriethoxysilane (0.5%) onto bare SPGE. Second, the AuNPs decoration on SiNWs-SPGE surface was functionalized using dithiopropionic acid through a self-assembly monolayer technique. The electrochemical response of methylene blue (MB) as a redox indicator toward synthetic DNA oligomer after hybridization on SiNWs/AuNPs-SPGE was recorded by cyclic voltammetry and differential pulse voltammetry techniques. The results demonstrated that the reduction peak current of MB was significantly decreased after DNA hybridization process. In addition, the developed biosensor showed a good storage stability and could achieve a linear range of 1 × 10−11 − 1 × 10−7 M (R = 0.98) with the detection limit of 1.63 × 10−12 M.

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Publication

A portable automatic endpoint detection system for amplicons of loop mediated isothermal amplification on microfluidic compact disk platform

( 2015)

Shah Uddin

;

Fatimah Ibrahim

;

Abkar Sayad

;

Aung Thiha

;

Koh Pei

;

Mas Mohktar

;

Uda Hashim

;

Jongman Cho

;

Kwai Thong

In recent years, many improvements have been made in foodborne pathogen detection methods to reduce the impact of food contamination. Several rapid methods have been developed with biosensor devices to improve the way of performing pathogen detection. This paper presents an automated endpoint detection system for amplicons generated by loop mediated isothermal amplification (LAMP) on a microfluidic compact disk platform. The developed detection system utilizes a monochromatic ultraviolet (UV) emitter for excitation of fluorescent labeled LAMP amplicons and a color sensor to detect the emitted florescence from target. Then it processes the sensor output and displays the detection results on liquid crystal display (LCD). The sensitivity test has been performed with detection limit up to 2.5 × 10−3 ng/µL with different DNA concentrations of Salmonella bacteria. This system allows a rapid and automatic endpoint detection which could lead to the development of a point-of-care diagnosis device for foodborne pathogens detection in a resource-limited environment.

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Publication

A potentiometric indirect uric acid sensor based on ZnO nanoflakes and immobilized uricase

( 2012)

Syed M. Usman Ali

;

Zafar Hussain Ibupoto

;

Muhammad Kashif

;

Uda Hashim

;

Magnus Willander

In the present work zinc oxide nanoflakes (ZnO-NF) structures with a wall thickness around 50 to 100 nm were synthesized on a gold coated glass substrate using a low temperature hydrothermal method. The enzyme uricase was electrostatically immobilized in conjunction with Nafion membrane on the surface of well oriented ZnO-NFs, resulting in a sensitive, selective, stable and reproducible uric acid sensor. The electrochemical response of the ZnO-NF-based sensor vs. a Ag/AgCl reference electrode was found to be linear over a relatively wide logarithmic concentration range (500 nM to 1.5 mM). In addition, the ZnO-NF structures demonstrate vast surface area that allow high enzyme loading which results provided a higher sensitivity. The proposed ZnO-NF array-based sensor exhibited a high sensitivity of ~66 mV/ decade in test electrolyte solutions of uric acid, with fast response time. The sensor response was unaffected by normal concentrations of common interferents such as ascorbic acid, glucose, and urea

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Publication

Assessing respiratory complications by carbon dioxide sensing platforms: advancements in infrared radiation technology and IoT integration

(Elsevier, 2023-02)

Santheraleka Ramanathan

;

Malarvili Balakrishnan

;

Subash Chandra Bose Gopinath

Respiratory illness demands pragmatic clinical monitoring and diagnosis to curb numerous fatal diseases in all aged groups. Due to the complicated instrumentation, long amplification periods, and restricted number of simultaneous detections, present clinically available multiplex diagnostic technologies are difficult to deploy the onsite diagnostic platforms. The futuristic assessment of medical diagnosis eases the respiratory monitoring using exhaled breath, due to the simple and comfort non-invasive detecting techniques. Carbon dioxide (CO₂) stands as a promising biomarker and has been identified in exhaled breath samples that distinguish different respiratory issues. State-of-the-art CO₂ gas sensing strategies are recognized with the growth of modern telecommunication technologies for real-time respiratory illness monitoring and diagnosis using exhaled breath. The presented article reviews the existing CO₂ gas sensors and their developments towards medical applications. With that, the advancement of infrared (IR) CO₂ gas sensors with distinguished light and sensing properties in detecting respiratory disorders are overviewed. The development of optimal CO₂ gas sensing strategy incorporated with Internet of Things (IoT) technology is over-reviewed. The hurdles encountered in the existing research and future preference with real-time CO₂ monitoring and diagnosing respiratory disorders with the advancement attained in IR sensing technology and IoT networking are highlighted.

Publication

Augmented sensitivity in electrolyte determination for sweat analysis: Rapid amperometric quantification by self-induced gold nanorods aggregation

(Elsevier, 2025-03)

Jia-Chun Lim

;

Subash Chandra Bose Gopinath

;

Sing-Mei Tan

;

Emily M.Y. Chow

;

Yeng Chen

Background: In this research, different strategies for leveraging gold nanorods (GNRs) were proposed to augment the sensitivity of a fabricated aluminum interdigitated electrodes (IDE) biosensor for detecting sodium chloride (NaCl) at millimolar concentrations. Methods: The sensitivity of the electronic biosensor in detecting NaCl was evaluated by examining the linear relationships between current changes and salt concentrations established at specific voltages. Significant Findings: The results presented that current signals were enhanced when incorporating the catalysts into the detection. At 2.0 V, the biosensor whose surface was functionalized with immobilized GNRs generated prominent electrical responses, with a sensitivity value of 0.0596 mA mM−1 cm−2. However, the performance of NaCl quantification recorded a further enhancement of 87.92 % when the mixture consisting of aggregated GNRs induced by the NaCl sample was pipetted onto the bare biosensor. The mechanisms for both application strategies of GNRs were introduced and discussed. This study provides insight into the detection of low concentrations of NaCl and potentially contributes to the ‘sweat test’ for screening health complications, such as cystic fibrosis (CF)

Publication

Automated, high-throughput DNA extraction protocol for disposable label free, microfluidics integrating DNA biosensor for oil palm pathogen, Ganoderma boninense

( 2020-05-01)

Adilah Ayoib

;

Uda Hashim

;

Subash Chandra Bose Gopinath

Basal Stem Rot and Upper Stem Rot diseases caused by pathogenic fungus Ganoderma boninense continue to be a major plight in the palm oil industry. Despite continuous research in combating the problem, resolution remains stagnant. Here, developed an automated, high-throughput DNA extraction protocol on microfluidics device for a quick, disposable, label-free detection, within 2 h of assessment. Microfluidics was designed using AutoCAD software, fabricated on microscopic glass substrate using negative photoresist (SU-8 2015) and molded with a biopolymer silicone, Polydimethylsiloxane. G. boninense and unknown pathogenic fungus isolated from rotten mushroom were grown and fractions of extracted DNA were pooled and analyzed for comparison along with synthetic ssDNA of G. boninense. Results from LPM and HPM show successful fabrication with ≤0.1 mm variance between the dimensions in the design before and after lithography process. The PDMS microfluidics show no leakage when run with DNA samples. Analyses from I-V measurement, UV–vis, FTIR, and PCR show comparable results between extracted and synthetic ssDNA of G. boninense and a contrast with the unknown pathogenic fungus, indicating a successful DNA extraction protocol via microfluidics for label-free identification of G. boninense. Optimization of DNA extraction can be further devised for applicability on lab-on-a-chip devices.

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Publication

Binding dynamics and conformational stability of graphene-based nanomaterials with Mutant LOX-1: Insights from molecular docking and dynamics simulations in atherosclerosis

(Springer, 2024-12)

Farizah Hanim Lat

;

Ahmad Naqib Shuid

;

Mohd Yusmaidie Aziz

;

Muhammad Mahyiddin Ramli

;

Rafeezul Mohamed

Oxidized low-density lipoprotein (oxLDL) is a critical factor in endothelial dysfunction and serves as an important biomarker for oxidative stress. Recent research has focused on lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a receptor for oxLDL that plays a significant role in atherosclerosis progression. Mutant LOX-1 may show changes in its binding affinity for oxLDL, potentially leading to variations in oxLDL uptake and foam cell formation. Our previous investigation into graphene-based nanomaterials and their interactions with atherosclerosis-related proteins, including LOX-1, provided important insights into their binding characteristics. In this study, we delve deeper into the binding dynamics between graphene-based nanomaterials and mutant LOX-1, aiming to clarify their implications for atherosclerotic development. Using molecular docking techniques with AutodockVina and active site predictions from P2Rank, we evaluated the binding affinities of graphene, graphene oxide (GO), and reduced graphene oxide (rGO) to mutant LOX-1. Notably, all docking scores were below -5 kcal/mol, indicating strong interactions with the receptor. To investigate the dynamics of these interactions further, we performed molecular dynamics (MD) simulations using the CHARMM force field. Our simulations revealed significant conformational changes within the first 100 ns, particularly in the mutant LOX-1 and GO complex, which suggested improved binding stability. These results enhance our understanding of how graphene-based nanomaterials interact with mutant forms of LOX-1, offering potential avenues for targeted therapies in atherosclerosis management related to LOX-1 dysregulation.

Publication

Comparative reliability studies and analysis of Au, Pd-Coated Cu and Pd-Doped Cu Wire in microelectronics packaging

( 2013)

Gan Chong Leong

;

Uda Hashim

;

Vipul Bansal

This paper compares and discusses the wearout reliability and analysis of Gold (Au), Palladium (Pd) coated Cu and Pd-doped Cu wires used in fineline Ball Grid Array (BGA) package. Intermetallic compound (IMC) thickness measurement has been carried out to estimate the coefficient of diffusion (D o ) under various aging conditions of different bonding wires. Wire pull and ball bond shear strengths have been analyzed and we found smaller variation in Pd-doped Cu wire compared to Au and Pd-doped Cu wire. Au bonds were identified to have faster IMC formation, compared to slower IMC growth of Cu. The obtained weibull slope, b of three bonding wires are greater than 1.0 and belong to wearout reliability data point. Pd-doped Cu wire exhibits larger time-to-failure and cycles-to-failure in both wearout reliability tests in Highly Accelerated Temperature and Humidity (HAST) and Temperature Cycling (TC) tests. This proves Pd-doped Cu wire has a greater potential and higher reliability margin compared to Au and Pd-coated Cu wires.

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Publication

Conductometric immunosensor for specific Escherichia coli O157:H7 detection on chemically funcationalizaed interdigitated aptasensor

( 2024)

Muhammad Nur Afnan Uda

;

Alaa Kamal Yousif Dafhalla

;

Thikra S. Dhahi

;

Tijjani Adam

;

Subash Chandra Bose Gopinath

;

Asral Bahari ambek

;

Muhammad Nur Aiman Uda

;

Nor Azizah Parmin

;

Nur Hulwani Ibrahim

;

Uda Hashim

Escherichia coli O157:H7 is a strain of Escherichia coli known for causing foodborne illness through the consumption of contaminated or raw food. To detect this pathogen, a conductometric immunosensor was developed using a conductometric sensing approach. The sensor was con-structed on an interdigitated electrode and modified with a monoclonal anti-Escherichia coli O157: H7 aptamer. A total of 200 electrode pairs were fabricated and modified to bind to the target molecule replica. The binding replica, acting as the bio-recognizer, was linked to the electrode surface using 3-Aminopropyl triethoxysilane. The sensor exhibited excellent performance, detecting Escherichia coli O157:H7 in a short time frame and demonstrating a wide detection range of 1 fM to 1 nM. Concentrations of Escherichia coli O157:H7 were detected within this range, with a minimum detection limit of 1 fM. This innovative sensor offers simplicity, speed, high sensitivity, selectivity, and the potential for rapid sample processing. The potential of this pro-posed biosensor is particularly beneficial in applications such as drug screening, environmental monitoring, and disease diagnosis, where real-time information on biomolecular interactions is crucial for timely decision-making and where cross-reactivity or interference may compromise the accuracy of the analysis.

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Publication

Detection of SARS-CoV-2 in environment: current surveillance and effective data management of COVID-19

(Taylor & Francis, 2023)

Sh. Nadzirah

;

Noraziah Mohamad Zin

;

Arif Khalid

;

Nur Faizah Abu Bakar

;

Siti Syafiqah Kamarudin

;

Siti Shahara Zulfakar

;

Ken Wong Kon

;

Nor Azila Muhammad Azami

;

Teck Yew Low

;

Roharsyafinaz Roslan

;

M. Nizar Hadi M Nassir

;

Anis Amirah Alim

;

P. Susthitha Menon

;

Norhayati Soin

;

Subash Chandra Bose Gopinath

;

Huda Abdullah

;

Jahariah Sampe

;

Hafzaliza Erny Zainal Abidin

;

Siti Nurfadhlina Mohd Noor

;

Ahmad Ghadafi Ismail

;

Chang Fu Dee

;

Azrul Azlan Hamzah

Since diagnostic laboratories handle large COVID-19 samples, researchers have established laboratory-based assays and developed biosensor prototypes. Both share the same purpose; to ascertain the occurrence of air and surface contaminations by the SARS-CoV-2 virus. However, the biosensors further utilize internet-of-things (IoT) technology to monitor COVID-19 virus contamination, specifically in the diagnostic laboratory setting. The IoT-capable biosensors have great potential to monitor for possible virus contamination. Numerous studies have been done on COVID-19 virus air and surface contamination in the hospital setting. Through reviews, there are abundant reports on the viral transmission of SARS-CoV-2 through droplet infections, person-to-person close contact and fecal-oral transmission. However, studies on environmental conditions need to be better reported. Therefore, this review covers the detection of SARS-CoV-2 in airborne and wastewater samples using biosensors with comprehensive studies in methods and techniques of sampling and sensing (2020 until 2023). Furthermore, the review exposes sensing cases in public health settings. Then, the integration of data management together with biosensors is well explained. Last, the review ended with challenges to having a practical COVID-19 biosensor applied for environmental surveillance samples.

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Publication

Easy extraction of Ganoderma boninense liquid sample using portable on‐chip device

( 2024)

Adella Josephin

;

Yudan Whulanza

;

Siti Fauziyah Rahman

;

Kenny Lischer

;

Muhammad Imam Surya

;

Irfan Martiansyah

;

Wiguna Rahman

;

Uda Hashim

Detecting Ganoderma boninense in Indonesia is crucial for effectively controlling and mitigating the spread of basal stem disease in oil palm fields. While there is ongoing development of tolerant plants, no such plant has been successfully created yet. Consequently, researchers are actively studying detection methods for Ganoderma boninense. One established and highly accurate approach is the use of polymerase chain reaction (PCR) techniques for molecular detection. However, this method requires time‐consuming sample preparation, which can pose challenges in plantation settings. To address this problem, a portable lab‐on‐chip device has been introduced. This technology enables easy and automatic DNA retrieval from liquid samples by absorbing lysed DNA using magnetic beads. An efficient mechanism for manipulating the magnetic bead within the semiconductor has been successfully implemented. The extraction process typically takes around 15 minutes using a modified methodology on the chip device approach. The chip facilitates the retrieval of two samples with a capacity of 120 µL for each sample. The PCR method was utilized to validate the equivalence of the lab‐on‐chip device extraction to the standard extraction method. This represents a promising alternative for expedited and simplified detection of Ganoderma boninense in field conditions.

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Publication

Effect of manganese content on the fabrication of porous anodic alumina

( 2012)

Voon Chun Hong

;

M. N. Derman

;

Uda Hashim

The influence of manganese content on the formation of well-ordered porous anodic alumina was studied. Porous anodic alumina has been produced on aluminium substrate of different manganese content by single-step anodizing at 50 V in 0.3 M oxalic acid at 15°C for 60 minutes. The well-ordered pore and cell structure was revealed by subjecting the porous anodic alumina to oxide dissolution treatment in a mixture of chromic acid and phosphoric acid. It was found that the manganese content above 1 wt% impaired the regularity of the cell and pore structure significantly, which can be attributed to the presence of secondary phases in the starting material with manganese content above 1 wt%. The pore diameter and interpore distance decreased with the addition of manganese into the substrates. The time variation of current density and the thickness of porous anodic alumina also decreased as a function of the manganese content in the substrates.

5 14

Publication

Effect of temperature of oxalic acid on the fabrication of porous anodic alumina from A1-Mn alloys

( 2013-04-12)

Voon Chun Hong

;

Mohd Nazree Derman

;

Uda Hashim

;

K. R. Ahmad

;

Foo Kai Loong

The influence of temperature of oxalic acid on the formation of well-ordered porous anodic alumina on Al-0.5 wt% Mn alloys was studied. Porous anodic alumina has been produced on Al-0.5 wt% Mn substrate by single-step anodising at 50 V in 0.5 M oxalic acid at temperature ranged from 5°C to 25°C for 60 minutes. The steady-state current density increased accordingly with the temperature of oxalic acid. Hexagonal pore arrangement was formed on porous anodic alumina that was formed in oxalic acid of 5, 10 and 15°C while disordered porous anodic alumina was formed in oxalic acid of 20 and 25°C. The temperature of oxalic acid did not affect the pore diameter and interpore distance of porous anodic alumina. Both rate of increase of thickness and oxide mass increased steadily with increasing temperature of oxalic acid, but the current efficiency decreased as the temperature of oxalic acid increased due to enhanced oxide dissolution from pore wall.

5 20

Publication

Effective synthesis of silicon carbide nanotubes by microwave heating of blended silicon dioxide and multi-walled carbon nanotube

( 2017)

Voo Chung Sung Tony

;

Voon Chun Hong

;

Lee Chang Chuan

;

Lim Bee Ying

;

Subash Chandra Bose Gopinath

;

Foo Kai Loong

;

Mohd Khairuddin Md Arshad

;

Ruslinda A. Rahim

;

Uda Hashim

;

Nashaain Mohd Nordin

;

Yarub Al-Douri

Silicon carbide nanotube (SiCNTs) has been proven as a suitable material for wide applications in high power, elevated temperature and harsh environment. For the first time, we reported in this article an effective synthesis of SiCNTs by microwave heating of SiO2 and MWCNTs in molar ratio of 1:1, 1:3, 1:5 and 1:7. Blend of SiO2 and MWCNTs in the molar ratio of 1:3 was proven to be the most suitable for the high yield synthesis of β-SiCNTs as confirmed by X-ray diffraction pattern. Only SiCNTs were observed from the blend of MWCNTs and SiO2 in the molar ratio of 1:3 from field emission scanning electron microscopy imaging. High magnification transmission electron microscopy showed that tubular structure of MWCNT was preserved with the inter-planar spacing of 0.25 nm. Absorption bands of Si-C bond were detected at 803 cm-1 in Fourier transform infrared spectrum. Thermal gravimetric analysis revealed that SiCNTs from ratio of 1:3 showed the lowest weight loss. Thus, our synthetic process indicates high yield conversion of SiO2 and MWCNTs to SiCNTs was achieved for blend of SiO2 and MWCNTs in molar ratio of 1:3.

4 31

Publication

Fabrication of silicon nanowire sensors for highly sensitive pH and DNA hybridization detection

( 2022)

Siti Fatimah Abd Rahman

;

Nor Azah Yusof

;

Mohd Khairuddin Md Arshad

;

Uda Hashim

;

Mohammad Nuzaihan Md Nor

;

Mohd Nizar Hamidon

A highly sensitive silicon nanowire (SiNW)-based sensor device was developed using electron beam lithography integrated with complementary metal oxide semiconductor (CMOS) technology. The top-down fabrication approach enables the rapid fabrication of device miniaturization with uniform and strictly controlled geometric and surface properties. This study demonstrates that SiNW devices are well-aligned with different widths and numbers for pH sensing. The device consists of a single nanowire with 60 nm width, exhibiting an ideal pH responsivity (18.26 × 106 Ω/pH), with a good linear relation between the electrical response and a pH level range of 4–10. The optimized SiNW device is employed to detect specific single-stranded deoxyribonucleic acid (ssDNA) molecules. To use the sensing area, the sensor surface was chemically modified using (3-aminopropyl) triethoxysilane and glutaraldehyde, yielding covalently linked nanowire ssDNA adducts. Detection of hybridized DNA works by detecting the changes in the electrical current of the ssDNA-functionalized SiNW sensor, interacting with the targeted ssDNA in a label-free way. The developed biosensor shows selectivity for the complementary target ssDNA with linear detection ranging from 1.0 × 10−12 M to 1.0 × 10−7 M and an attained detection limit of 4.131 × 10−13 M. This indicates that the use of SiNW devices is a promising approach for the applications of ion detection and biomolecules sensing and could serve as a novel biosensor for future biomedical diagnosis.

5 17

Publication

Fabrication of silicon nitride ion sensitive field-effect transistor for pH measurement and DNA Immobilization/Hybridization

( 2013)

Uda Hashim

;

Soon Weng Chong

;

Liu Wei Wen

The fabrication of ion sensitive field-effect transistor (ISFET) using silicon nitride (Si3N4) as the sensing membrane for pH measurement and DNA is reported. For the pH measurement, the Ag/AgCl electrode was used as the reference electrode, and different pH values of buffer solution were used in the ISFET analysis. The ISFET device was tested with pH buffer solutions of pH2, pH3, pH7, pH8, and pH9. The results show that the IV characteristic of ISFET devices is directly proportional and the device’s sensitivity was 43.13 mV/pH. The ISFET is modified chemically to allow the integration with biological element to form a biologically active field-effect transistor (BIOFET). It was found that the DNA immobilization activities which occurred on the sensing membrane caused the drain current to drop due to the negatively charged backbones of the DNA probes repelled electrons from accumulating at the conducting channel. The drain current was further decreased when the DNA hybridization took place.

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Publication

Facile synthesis of MoS₂ nanoflower-Ag NPs grown on lignin-derived graphene for Troponin I aptasensing

(Elsevier, 2023)

Mugashini Vasudevan

;

Sathaniswarman Remesh

;

Veeradasan Perumal

;

Pandian Bothi Raja

;

Mohammad Nasir Mohammad Ibrahim

;

Subash Chandra Bose Gopinath

;

Saravanan Karuppanan

;

Mark Ovinis

This article presents the development and application of a green lignin-derived graphene biosensor for Troponin I, a biomarker for Acute Myocardial Infarction (AMI). The graphene was synthesized from oil palm lignin through an optimized laser scribing process. While the three-dimensional nature of the laser-scribed lignin-derived graphene (3D LSG) is advantageous, it suffers from poor electrical conductivity due to the amorphous nature of lignin. Therefore, semi-conductive molybdenum disulphide (MoS2) precursor with conductive green silver nanoparticles (Ag NPs) was added to 0.5, 1.0, 1.5, and 2.0 g of 3D LSG to synthesize 3D LSG_MoS2_Ag NPs hybrids via an aqueous hydrothermal process. Morphological, physical, and structural analyses showed the presence of petal-like MoS2 nanoflower with Ag NPs on the 3D LSG surface. The strong interrelation between 3D LSG, MoS2, and Ag NPs was confirmed by X-ray spectroscopy, Raman spectroscopy and energy dispersive spectroscopy (EDS). Specifically, X-ray spectroscopy revealed the formation of O1s, Ag 3d, C1s, Mo 3d, and S2p in the 3D LSG_MoS2_Ag NPs-2.0 hybrid. Raman spectroscopy revealed an enhancement in the surface area of the 3D LSG_MoS2_Ag NPs-2.0 hybrid, which enhances the detection sensitivity. The 3D LSG_MoS2_Ag NPs hybrid was subsequently chemically modified and immobilised with an aptamer to interact with Troponin I on an impedimetric sensor. The 3D LSG_MoS2_Ag NPs hybrid showed high analytical performance, high specificity, and a ∼ 4-fold increment in selectivity, with a detection limit of 100 attomolar. This biosensor has a sensitivity of 31.45 µA mM−1 cm−2, stability of 87%, with a relative standard deviation for reproducibility of 3.8%.

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Publication

Faradaic and non-faradaic depletions by anodic electrode corrosion with strong electrolytes on tautochrone curve interdigitated electrodes

(Elsevier Ltd, 2025)

Jia-Chun Lim

;

Subash Chandra Bose Gopinath

;

Hemavathi Krishnan

;

Sing-Mei Tan

By integrating conventional parallel electrodes with two semi-circular curves, a new tautochrone curve interdigitated electrodes (TCIDE) biosensor was fabricated to be compatible for Faradaic and non-Faradaic measurements. Scanning electron microscopy affirmed the immaculate fabrication, as multiple scans showed that both the width and gap of electrodes were 50.0 μm, with a maximum percentage error of ∼8.0 %. A maximum current of 29.54 μA was generated with a strong electrolyte (pH 2), signifying the weak adaptability of the device to a highly acidic medium. The stability of the biosensor was further evaluated by prolonging the exposure duration to different pH levels for 5 min. Substantial increases in current were recorded under extreme pH environments (pH 2, 3, and 12) over the duration at 2.0 V, while others maintained excellent stability. A high-power microscope revealed that the anodic aluminium transducers experienced surface corrosion, elucidating the unusual current fluctuations. The mechanisms of anodic corrosion caused by the strong electrolytes were additionally proposed and discussed. As validated by electrochemical impedance spectroscopy, this study provides valuable insights into the declined biosensing performances of corroded anodes.

Publication

Food assimilated by two sympatric populations of the brown planthopper Nilaparvata lugens (Delphacidae) feeding on different host plants contaminates insect DNA detected by RAPD-PCR analysis

( 2012)

M.A. Latif

;

M.Y. Omar

;

S.G. Tan

;

S.S. Siraj

;

Ali, Mohamad Eaqub

;

M.Y. Rafii

Contamination of insect DNA for RAPD-PCR analysis can be a problem because many primers are non-specific and DNA from parasites or gut contents may be simultaneously extracted along with that of the insect. We measured the quantity of food ingested and assimilated by two sympatric populations of brown planthopper (BPH), Nilaparvata lugens, one from rice and the other from Leersia hexandra (Poaceae), a wetland forage grass, and we also investigated whether host plant DNA contaminates that of herbivore insects in extractions of whole insects. Ingestion and assimilation of food were reduced significantly when individuals derived from one host plant were caged on the other species. The bands, OPA3 (1.25), OPD3 (1.10), OPD3 (0.80), OPD3 (0.60), pUC/M13F (0.35), pUC/M13F (0.20), BOXAIR (0.50), peh#3 (0.50), and peh#3 (0.17) were found in both rice-infesting populations of brown planthopper and its host plant (rice). Similarly, the bands, OPA4 (1.00), OPB10 (0.70), OPD3 (0.90), OPD3 (0.80), OPD3 (0.60), pUC/ M13F (0.35), pUC/M13F (0.20), and BOXAIR (0.50) were found in both Leersia-infesting populations of brown planthopper and the host plant. So, it is clear that the DNA bands amplified in the host plants were also found in the extracts from the insects feeding on them.

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