Graphene-titanium dioxide (TiO2-G) nanocomposite based hypoxanthine sensor for the assessment of meat freshness

Date of Publication


Document Type


Degree Name

Doctor of Philosophy in Physics

Subject Categories



College of Science



Thesis Adviser

Gil Nonato C. Santos

Defense Panel Chair

Romeric F. Pobre

Defense Panel Member

Drexel H. Camacho
Emmanuel T. Rodulfo
Melanie Y. David
Armando Somintac


This dissertation reports on the synthesis of a graphene-titanium dioxide nanocomposite (TiO2-G) and its use as an effective electrode material in an amperometric hypoxanthine (Hx) sensor for meat freshness evaluation. The nanocomposite was synthesized through the hydrothermal route under various conditions and then characterized by Transmission Electron Microscopy (TEM), Xray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Xray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), Brunauer Emmett Teller (BET), and Cyclic Voltammetry (CV) using the redox couples [Fe(CN)6]-3/-4 and [Ru(NH3)6]+3/+2 respectively. FTIR and XPS analysis confirmed the chemical integration of anatase TiO2 nanoparticles to the graphene surface. The nanocomposite synthesized with a mass- volume loading of 20 mg graphene and 100 mL TTIP (1:5 m/v ratio) for the duration of 12 hours at a temperature of 130 0C yields the highest BET surface area at 136.4 m2/g and exhibits the highest apparent heterogeneous electron transfer rate for Fe(CN)6 -3/-4 and [Ru(NH3)6]+3/+2 as compared to nanocomposites that were synthesized using other conditions. TGA revealed that the optimum TiO2-G nanocomposite contains about 61% titania. The TiO2-G nanocomposite offered a favorable microenvironment for direct electrochemistry of xanthine oxidase (XOD). The fabricated Nafion/XOD/TiO2-G/GCE sensor exhibited excellent electro catalytic activity towards Hx with linear range of 20 μM to 512 μM, limit of detection of 9.5 μM, and sensitivity of 4.1 nA/μM. In addition, the biosensor v also demonstrated strong anti-interference properties in the presence of uric acid (UA), ascorbic acid (AA) and glucose. Minimal interference of xanthine (Xn) was observed at ~7%. Moreover, the biosensor showed good repeatability (4.3% RSD) and reproducibility (3.8% RSD). The reported biosensor was tested towards the detection of Hx in pork tenderloins stored at room temperature for seven days. There was a good correlation (r = 0.9795) between biosensor response and measurements obtained by a standard enzymatic colorimetric method. The TiO2-G nanocomposite is therefore an effective electrode material to be used in electrochemical biosensors to assess the freshness of meat.

Abstract Format






Accession Number


Shelf Location

Archives, The Learning Commons, 12F Henry Sy Sr. Hall

Physical Description

1 computer optical disc; 4 3/4 in


Nanocomposites (Materials); Detectors; Meat--Evaluation

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