Foo Kai Loong
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Preferred name
Foo Kai Loong
Official Name
Foo, Kai Loong
Alternative Name
Loong, Foo Kai
Kai Loong, Foo
Foo, K. L.
Foo, Kai Loong
Foo, Kai Long
Main Affiliation
Scopus Author ID
37012449500
Researcher ID
D-2035-2015

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Low temperature annealed zinc oxide nanostructured thin film-based transducers: Characterization for sensing applications

2015 , R. Haarindraprasad , Uda Hashim , Subash Chandra Bose Gopinath , Muhammad Kashif , P. Veeradasan , S. R. Balakrishnan , Foo Kai Loong , Prabakaran A/L Poopalan

The performance of sensing surfaces highly relies on nanostructures to enhance their sensitivity and specificity. Herein, nanostructured zinc oxide (ZnO) thin films of various thicknesses were coated on glass and p-type silicon substrates using a sol-gel spin-coating technique. The deposited films were characterized for morphological, structural, and optoelectronic properties by high-resolution measurements. X-ray diffraction analyses revealed that the deposited films have a c-axis orientation and display peaks that refer to ZnO, which exhibits a hexagonal structure with a preferable plane orientation (002). The thicknesses of ZnO thin films prepared using 1, 3, 5, and 7 cycles were measured to be 40, 60, 100, and 200 nm, respectively. The increment in grain size of the thin film from 21 to 52 nm was noticed, when its thickness was increased from 40 to 200 nm, whereas the band gap value decreased from 3.282 to 3.268 eV. Band gap value of ZnO thin film with thickness of 200 nm at pH ranging from 2 to 10 reduces from 3.263eV to 3.200 eV. Furthermore, to evaluate the transducing capacity of the ZnO nanostructure, the refractive index, optoelectric constant, and bulk modulus were analyzed and correlated. The highest thickness (200 nm) of ZnO film, embedded with an interdigitated electrode that behaves as a pH-sensing electrode, could sense pH variations in the range of 2-10. It showed a highly sensitive response of 444 μAmM-1cm-2 with a linear regression of R2 =0.9304. The measured sensitivity of the developed device for pH per unit is 3.72μA/pH.

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Thermal behaviour and microstructural analysis of Sn-40Pb alloy and Sn-40Pb soldered on electroless nickel/immersion gold

2020 , Ai Ling Teoh , Mohd Arif Anuar Mohd Salleh , Dewi Suriyani Che Halin , Foo Kai Loong

Due to the toxicity of lead solder, the lead-free solder has been developing and improved in order to replace the lead solder. However, the behaviour and properties of lead solder is still better than the lead-free solder, especially in application when soldering on substrate. Hence, a common lead solder, Sn-40Pb is studied in this research by comparing with Sn-40Pb soldering on electroless nickel/immersion gold (ENIG) substrate. The thermal behaviour by differential scanning calorimeter (DSC) and microstructure formation with elemental analysis by scanning electron microscope (SEM) were carried out for Sn-40Pb solder alloy and Sn-40Pb soldered on ENIG substrate in this study. The result showed that the pasty range of Sn-40Pb was lower than Sn-40Pb/ENIG while the undercooling was higher. The diffusion and dissolution of Ni and Cu elements from ENIG substrate into the solder, forming the lead-rich phase with Ni elements and interfacial (Cu,Ni)6Sn5 with Pb elements in Sn-40Pb/ENIG. The diffusion and dissolution of elements from substrate into the solder affects the thermal behaviour and microstructural of solder.

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Hydrothermal Growth Zinc Oxide Nanorods for pH Sensor Application

2023-10-01 , Foo Kai Loong , Tan Soo Jin , Heah Cheng Yong , Subash Chandra Bose Gopinath , Liew Yun Ming , Uda Hashim , Voon Chun Hong

The aim of this work is to apply synthesized zinc oxide (ZnO) Nanorods using hydrothermal (HTL) growth technique for pH sensor application. The highly crystallite of ZnO Nanorods was obtained by anneal the growth ZnO Nanorods in furnace at 200 °C for 2 hours. Besides that, XRD analysis shows the produced ZnO Nanorods belonged to the (002) plane. Furthermore, Scanning Electron Microscope (SEM) images confirm that the ZnO Nanorods with hexagonal-faceted structural were successfully produced by HTL growth technique. In addition, Ultraviolet–visible (UV-Vis) spectrophotometer analysis shows that the synthesized ZnO belongs to the wide band gap semiconductor material. The growing ZnO Nanorods were then subjected to electrical measurement with various pH levels. The outcome demonstrates that the current rises as the solution changes from acidic to alkaline. Overall, our study shows a relationship between the electrical as well as the structural characteristics of ZnO Nanorods at various pH levels.

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Morphological, structural, and electrical characterization of sol-gel-synthesized ZnO nanorods

2013-02-03 , M. Kashif , Uda Hashim , M. E. Ali , Foo Kai Loong , Syed M. Usman Ali

ZnO nanorods were grown on thermally oxidized p-type silicon substrate using sol-gel method. The SEM image revealed high-density, well-aligned, and perpendicular ZnO nanorods on the oxidized silicon substrate. The XRD profile confirmed thec-axis orientation of the nanorods. PL measurements showed the synthesized ZnO nanorods have strong ultraviolet (UV) emission. The electrical characterization was performed using interdigitated silver electrodes to investigate the stability in the current flow of the fabricated device under different ultraviolet (UV) exposure times. It was notified that a stable current flow was observed after 60 min of UV exposure. The determination of stable current flow after UV exposure is necessary for UV-based gas sensing and optoelectronic devices.

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Improvement synthesis of graphene oxide yield in two steps of intercalation and oxidation of flexible graphite foil by electrochemical exfoliation

2024-04 , M. O. Ariffa , Liu Wei Wen , Foo Kai Loong

Synthesis of high quality and quantity of graphene by cost-effective methods are highly desirable for various application. In electrochemical exfoliation, graphite foil has been used as carbon source for the synthesis of high yield of graphene flakes. Electrochemical exfoliation is one of the faster and cheaper method to synthesize graphene sheets. In this work, five different types of concentration of sulphuric acid were used for electrochemical exfoliation. The electrochemical cell design where graphite foil as anode and copper foil as cathode which were connected to DC power supply of 5V. To examine the morphology scanning electron microscope (SEM) was employed in which the sheet structures with large lateral dimension and thin graphene flakes. Furthermore, X-ray diffraction (XRD) revealed that exfoliated graphene samples showed a significant peak at about 2θ = 26º corresponded to graphite.

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Functionalized Carbon Nanotube-Modified ELISA for Early Detection of Heart Attack

2023-12-01 , Chow E.M.Y. , Foo Kai Loong , Subash Chandra Bose Gopinath , Tan Soo Jin , Kashif M. , Heah Cheng Yong , Liew Yun Ming

A warning issue of heart attacks in young adults needs immediate attention lately. Enzyme-linked immunosorbent assay (ELISA) is an easy and commonly used method for detecting early stages of heart attack. Cardiac troponin I (cTnI) is a responsible biomarker for acute myocardial infarction. However, the conventional ELISA system was only able to detect at 100 pM of cTnI. To improve the system, enhancements were introduced through the integration of functionalized carbon nanotube (fCNT) to amplify cTnI detection signals. By utilizing the advantage of fCNT, a noticeable improvement in results can be obtained. The detection limit was lowered down to an impressive 10 pM. Furthermore, the change of absorbance increased from 31.90% for conventional ELISA surge to 98.61 for modified ELISA system. This three-fold increase in sensitivity shows remarkable improvement through the introduction of fCNT in modified ELISA technique.

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Towards greener one-part geopolymers through solid sodium activators modification

2022-12-10 , Ooi Wan En , Liew Yun Ming , Heah Cheng Yong , Ho Li Ngee , Mohd. Mustafa Al Bakri Abdullah , Bin Khalid M.S. , Foo Kai Loong , Ong Shee Ween , Pei Seng T. , Hang Yong Jie , Khairunnisa Zulkifly

This paper investigates the influence of various solid activators and their mixing parameters on the physical, mechanical and microstructural characteristics of greener one-part geopolymers (OPG) based on high calcium fly ash. The high calcium fly ash that has rarely been explored was utilised to develop OPG in this study. The anhydrous sodium metasilicate (Na2SiO3) with negative environmental impact propelled the partial replacement of Na2SiO3 with sodium hydroxide (NaOH) and sodium carbonate (Na2CO3). Two sets of high calcium fly ash OPGs were developed: (1) the MH-OPG comprised Na2SiO3 and NaOH; (2) the MC-OPG comprised Na2SiO3 and Na2CO3. The optimal MH-OPG (73 MPa) and MC-OPG (75 MPa) exhibited superior compressive strength, higher than the minimal requirement (>28 MPa) of ASTM C150/C150M-18 for construction binder material. Various solid alkali activators triggered different reaction mechanisms, yielding distinctive reaction products that contributed to strength growth. The sodium calcium aluminosilicate hydrate ((N,C)-A-S-H) gel was developed in MH-OPG, whereas the sodium carbonate hydrate, sodium aluminosilicate hydrate (N-A-S-H) and calcium aluminosilicate hydrate (C-A-S-H) binding phases were developed in the MC-OPG. Although Na2CO3 reduced the water demand, improved the fluidity and setting time, the MC-OPG was more sensitive to the alteration of mixing compositions, suggesting a tougher performance control during field application than the MH-OPG. The total embodied carbon (EC) of MC-OPG was lowered by 15.4% compared to that of MH-OPG. The embodied carbon index (ECI) of MH-OPG and MC-OPG were 81.3% and 84.7% less than that of OPC products. This work suggests that substituting Na2SiO3 with NaOH or Na2CO3 effectively produced a greener construction material without compromising mechanical strength.

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Towards greener one-part geopolymers through solid sodium activators modification

2022-12-10 , Wan-En O. , Yun-Ming L. , Cheng-Yong H. , Ho Li Ngee , Mohd. Mustafa Al Bakri Abdullah , Bin Khalid M.S. , Foo Kai Loong , Shee-Ween O. , Pei Seng T. , Yong Jie H. , Zulkifly K.

This paper investigates the influence of various solid activators and their mixing parameters on the physical, mechanical and microstructural characteristics of greener one-part geopolymers (OPG) based on high calcium fly ash. The high calcium fly ash that has rarely been explored was utilised to develop OPG in this study. The anhydrous sodium metasilicate (Na2SiO3) with negative environmental impact propelled the partial replacement of Na2SiO3 with sodium hydroxide (NaOH) and sodium carbonate (Na2CO3). Two sets of high calcium fly ash OPGs were developed: (1) the MH-OPG comprised Na2SiO3 and NaOH; (2) the MC-OPG comprised Na2SiO3 and Na2CO3. The optimal MH-OPG (73 MPa) and MC-OPG (75 MPa) exhibited superior compressive strength, higher than the minimal requirement (>28 MPa) of ASTM C150/C150M-18 for construction binder material. Various solid alkali activators triggered different reaction mechanisms, yielding distinctive reaction products that contributed to strength growth. The sodium calcium aluminosilicate hydrate ((N,C)-A-S-H) gel was developed in MH-OPG, whereas the sodium carbonate hydrate, sodium aluminosilicate hydrate (N-A-S-H) and calcium aluminosilicate hydrate (C-A-S-H) binding phases were developed in the MC-OPG. Although Na2CO3 reduced the water demand, improved the fluidity and setting time, the MC-OPG was more sensitive to the alteration of mixing compositions, suggesting a tougher performance control during field application than the MH-OPG. The total embodied carbon (EC) of MC-OPG was lowered by 15.4% compared to that of MH-OPG. The embodied carbon index (ECI) of MH-OPG and MC-OPG were 81.3% and 84.7% less than that of OPC products. This work suggests that substituting Na2SiO3 with NaOH or Na2CO3 effectively produced a greener construction material without compromising mechanical strength.

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Properties of polyaniline/graphene oxide (PANI/GO) composites: effect of GO loading

2021-09-01 , Mutalib T.N.A.B.T.A. , Tan Soo Jin , Foo Kai Loong , Liew Yun Ming , Heah Cheng Yong , Mohd. Mustafa Al Bakri Abdullah

Polyaniline/graphene oxide (PANI/GO) composites at different wt% of GO were prepared via solution method. PANI was mixed with the GO synthesized from the improved Hummer’s method. The formation of GO was confirmed via Raman and C/O ratio. Based on the FT-IR, XRD and SEM results, it confirmed the presence of both PANI and GO characteristics at 10.9°, 25.8° and 27.8° and interactions between PANI and GO particles in PANI/GO composites at different GO loading. SEM micrographs showed a folding and wrinkled surface of GO due to the defect upon oxidation process. This means that the weak π–π interactions or the agglomeration of GO have caused PANI unable to attach on the large conjugated basal planes of GO sheets. The defective domains made GO as an insulator as it contained distortions and oxygen-containing functional groups and their local decoration. Low-conductivity domain had conquered most of the GO region which later reduced the pathway of the current flow; therefore, conductivity is affected. The wrinkled structure also resulted in the low conductivity as it weakens the interfacial interaction between PANI and GO and thus disrupted the electron movement in the composites. Due to this, the electrical conductivity reached up to 1.83 × 10−10 S/cm as the GO loading increased to 50 wt%.

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From nanostructure to nano biosensor: Institute of Nano Electronic Engineering (INEE), UniMAP experience

2011 , Uda Hashim , Foo Kai Loong

Nanostructure is defined as something that has a physical dimension smaller than 100 nanometers, ranging from clusters and/or to dimensional layers of atoms. There are three most important nanostructures that are extensively studied and researched in various organizations including Institute of Nano Electronic Engineering (INEE) in UniMAP. These include quantum dot, nanowire, and nanogap, which have been successfully designed and fabricated using in-house facilities available. These are subsequently used as a main sensing component in nanostructures based biosensor. This fabrication, characterization and testing job were done within four main interlinked laboratories namely microfabrication cleanroom, nanofabrication cleanroom, failure analysis laboratory and nano biochip laboratory. Currently, development of Nano Biosensor is the main research focus in INEE. In principle, biosensor is an analytical device which converts a biological response into an electrical signal.

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