Zinc oxide Archives – Institute of Nano Electronic Engineering

The ZnO-FET Biosensor for Cardiac Troponin I

July 23, 2018 By Editor

Abstract – This paper investigates the influence of substrate-gate coupling on the ZnO-FET biosensor’s sensitivity for detection of cardiac troponin I (cTnI), a ‘gold standard’ biomarker for acute myocardial infarction (AMI). The FET-based device with introduction of substrate-gate coupling on p-type silicon-on-insulator (SOI) substrate is fabricated using conventional lithography processes. An n-type zinc oxide (ZnO) thin film deposited via electron-beam evaporator is used as transducer for bridging the source and drain regions. Surface modifications via functionalization with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) as chemical linkers, followed by immobilization of cTnI monoclonal antibody (MAb-cTnI) as bio-receptor on the ZnO thin film allow different concentration of cTnI detection with high selectivity. The device’s sensitivity increases up to 9 %•(g/ml)-1 with the increase of the substrate-gate voltage (VSG) up to -10 V at very low limit of detection (LOD) down to 1.6 fg/ml.

Corresponding Author: Mohamad Faris Mohamad Fathil
Corresponding Author’s Email: mohamadfaris@unimap.edu.my

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A new nano-worm structure from gold-nanoparticle mediated random curving of zinc oxide nanorods

December 17, 2015 By Editor

Abstract – Creating novel nanostructures is a primary step for high-performance analytical sensing. Herein, a new worm like nanostructure with Zinc Oxide-gold (ZnO/Au) hybrid was fabricated through an aqueous hydrothermal method, by doping Au-nanoparticle (AuNP) on the growing ZnO lattice. During ZnO growth, fine tuning the solution temperature expedites random curving of ZnO nanorods and forms nano-worms. The nano-worms which were evidenced by morphological, physical and structural analyses, revealed elongated structures protruding from the surface (length: 1. μm; diameter: ~100. nm). The appropriate peaks for the face centred cubic gold were (111) and (200), as seen from X-ray diffractogram. The strong interrelation between Au and ZnO was manifested by X-ray photoelectron spectroscopy. The combined surface area increment from the nanoparticle radii and ZnO nanorod random curving gives raise an enhancement in detection sensitivity by increasing bio-loading. ‘Au-decorated hybrid nano-worm’ was immobilized with a probe DNA from Vibrio Cholera and duplexed with a target which was revealed by Fourier Transform Infrared Spectroscopy. Our novel Au-decorated hybrid nano-worm is suitable for high-performance bio-sensing, as evidenced by impedance spectroscopy, having higher-specificity and attained femtomolar (10. fM) sensitivity. Further, higher stability, reproducibility and regeneration on this sensing surface were demonstrated.

Keywords – Cholera, DNA, Gold nanoparticle, Nano-worm, Nanorod, Zinc Oxide

Corresponding Author: Uda Hashim
Corresponding Author’s Email: uda@unimap.edu.my

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‘Spotted Nanoflowers’: Gold-seeded Zinc Oxide Nanohybrid for Selective Bio-capture

September 8, 2015 By Editor

Abstract – Hybrid gold nanostructures seeded into nanotextured zinc oxide (ZnO) nanoflowers (NFs) were created for novel biosensing applications. The selected ‘spotted NFs’ had a 30-nm-thick gold nanoparticle (AuNP) layer, chosen from a range of AuNP thicknesses, sputtered onto the surface. The generated nanohybrids, characterized by morphological, physical and structural analyses, were uniformly AuNP-seeded onto the ZnO NFs with an average length of 2–3 μm. Selective capture of molecular probes onto the seeded AuNPs was evidence for the specific interaction with DNA from pathogenic Leptospirosis-causing strains via hybridization and mis-match analyses. The attained detection limit was 100 fM as determined via impedance spectroscopy. High levels of stability, reproducibility and regeneration of the sensor were obtained. Selective DNA immobilization and hybridization were confirmed by nitrogen and phosphorus peaks in an X-ray photoelectron spectroscopy analysis. The created nanostructure hybrids illuminate the mechanism of generating multiple-target, high-performance detection on a single NF platform, which opens a new avenue for array-based medical diagnostics.

Corresponding Author: Uda Hashim
Corresponding Author’s Email: uda@unimap.edu.my

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Effect of different solvents on the structural and optical properties of zinc oxide thin films for optoelectronic applications

January 2, 2015 By Editor

Abstract – Zinc oxide (ZnO) seed solutions were prepared using 4 different solvents, namely, methanol (MeOH), ethanol (EtOH), isopropyl alcohol (IPA) and 2-methoxyethanol (2-ME). The prepared seed solutions were used to synthesize ZnO thin films using a low-cost sol–gel spin-coating method. The effect of different solvents on the structural and optical properties of ZnO thin films was investigated by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and an ultraviolet–visible–near infrared spectrophotometer (UV–vis–NIR). The images obtained in the FESEM and AFM showed that the thin film prepared using 2-ME has the smallest grain size. Moreover, the X-ray diffraction (XRD) results showed that the synthesized ZnO films are polycrystalline with preferred orientation along the (002) plane, whereas the IPA- derived films have a preferred orientation on (101) plane. The ZnO thin film synthesized with 2-ME has the highest transmittance (>90%), lowest surface roughness of 3.131 nm and highest band gap energy of 3.28 eV. The experimental data are in agreement with the calculated results by specific models of refractive index.

Keywords – Zinc oxide, Solvents, Optical, Structural, Sol–gel

Corresponding Author: Foo Kai Loong
Corresponding Author’s Email: klfoo@unimap.edu.my

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