STUDY ON THE OPTIMIZATION OF COLLOID CONCENTRATION IN THE FORMATION OF 2D JANUS ARRAYS OF CITRATE AND 3-MERCAPTOPROPIONIC ACID CAPPER GOLD NANOPARTICLES AS BIOSENSOR PROBES

• Main Author: Reza Fahriyansyah, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/83918
• Institution: Institut Teknologi Bandung

The development of nanotechnology, particularly the utilization of metal nanoparticles such as gold and silver, has now been applied in the fabrication of nano devices like sensors and optoelectronics. Gold nanoparticle (AuNP)-based plasmonic sensors have been found to possess significantly higher sensitivity compared to other conventional sensors. This is attributed to the unique optical properties of AuNPs, known as Loca- lized Surface Plasmon Resonance (LSPR). Further advancements in AuNP technology include the fabrication of biosensors in a 2D array structure. Optimal conditions for the 2D AuNP array structure can be achieved when the prepared AuNP colloid is su- fficiently homogeneous with minimal extra components. High-speed centrifugation purification is one method that can be used to obtain homogeneous AuNP colloids. The objective of this research is to conduct an optimization study of AuNP colloid concentration using centrifugation techniques to achieve a 2D Janus AuNP array stru- cture, which will subsequently be used as a plasmonic sensor probe for biomolecule detection. The synthesis of citrate-coated AuNPs (AuCA) and 3-MPA-coated AuN- Ps (AuMPA) was carried out using a modified chemical reduction method, followed by characterization of their optical, morphological, and chemical properties. Subse- quently, purification was performed using high-speed centrifugation with variations in speed and duration. The synthesis results of AuCA and AuMPA each produced red- wine-colored colloids with plasmonic peak characteristics at wavelengths of 524 nm for AuCA and 526 nm for AuMPA. From the purification process results, optical and morphological characterization showed that AuCA was most stable at a purification variation of 6000 rpm for 30 minutes, and generally, AuCA demonstrated stability with minimal large particles (less than 20%). In contrast, all AuMPA samples experienced aggregation after the purification process. In the fabrication of the 2D Janus AuCA array structure, it was shown that after one purification cycle, the formation of the Ja- nus array was very good, with a visible color change from red-wine to blue, indicating a closely packed and orderly single layer of AuCA. This color change indicates the presence of field enhancement driven by the red shift of the plasmonic peak in the ab- sorption curve of purified AuCA. The addition of biotin to the array causes a red shift in the absorption curve indicating that biotin is ready to be a probe sensor to detect specific biomolecules.