Abstract
In the development of QCM-based biosensor sensors, the sensor surface is a very important part because it determine how the surface interacting with its environment especially during the immobilization of biomolecules process. In the utilization of QCM as biomolecule detecting biosensor, it is necessary to coat the polymer material on the surface of QCM. A stearic acid layer is used as an immobilization matrix layer because stearic acid has both polar and non polar properties so it can interact with biomolecules. The stearic acid layer is deposited on the polystyrene surface using a vacuum evaporation method. A study of the microstructure of the stearic acid coating was conducted to determine the possibility of the deposited stearic acid layer used as the matrix layer. In this research, microstructural study of layers of the stearic acid by using Scanning Electron Microscope (SEM) was carried out to find out the surface morphology of stearic acid. X-Ray Difraction (XRD) measurements were conducted to identify the crystal structure of stearic acid while Fourier Transform Infrared (FTIR) measurements were used to determine the stearic acid functional group. The Scanning Electron Microscope (SEM) results show the surface of the cavity and pore layers of the polystyrene layer was coated with white fibers homogeneously deposited on the surface of QCM / Polystyrene. Furthermore, the X-Ray Difraction (XRD) results showing a spectrum peak at an angle of 2 q = 26,66 ° indicates the existence of stearic acid crystals. Whereas, the measurement results of the Fourier Transform Infrared (FTIR) indicate the appearance of C-H functional groups at a wavelength value of 3600-2600 cm -1 which indicates the functionality of the stearic acid layer.
Highlights
how the surface interacting with its environment
A stearic acid layer is used as an immobilization matrix layer because stearic acid has both polar
non-polar properties so it can interact with biomolecules
Summary
Deposisi lapisan polistiren dan Asam Stearat (SA). Pada penelitian ini digunakan sensor QCM dengan frekuensi 10 MHz dengan elektroda dari perak produk dari Greatmicro. Sebelum deposisi lapisan asam stearat, lapisan polistiren dideposisi di atas permukaan QCM kedua sisi elektrodanya dengan menggunakan metode spin coating. Selanjutnya larutan polistiren di deposisi pada permukaan QCM sebanyak 50 μl dengan menggunakan metode spin coating. Tahapan selanjutnya yaitu lapisan asam stearat di deposisi di atas permukaan PS/QCM dengan menggunakan metode evaporasi. Bahan padatan yang digunakan adalah asam stearat (kemurnian ≥ 98,5% dari Sigma-Aldrich) ditempatkan pada krusibel dengan jarak antara sampel dan target (QCM) sejauh 3 cm. Karakterisasi morfologi permukaan lapisan asam stearat yang terdeposisi di atas permukaan sensor PS/QCM diobservasi dengan SEM (FEI type Inspect S50), struktur kristal asam stearat di analisis dengan menggunakan XRD (PANAlytical) tipe E’xpert Pro dengan menggunakan sumber CuK di daerah sudut 2θ dengan rentang 15o – 80o dengan waktu scan tiap bagian sebesar satu menit. Sedangkan karakterisasi gugus fungsi asam stearat yang terdeposisi digunakan FTIR (SHIMADZU model: FTIR-8400S)
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