Studi Komposisi dan Ketebalan Polyvinyl Alcohol-Graphene Oxide (Pva-Go) Sebagai Sensor Aroma Kopi Robusta

Abstract

Development gas sensor is currently focused on composite materials and in recent years GO has been widely used as reinforcement and polyvinyl alcohol (PVA) as matrix. Intended to improve performance of gas sensor which previously used MOS materials. Study GO was prepared using Hummers-Offeman method from graphite which was then blended with PVA to produce PVA-GO composite. Composite was characterized by UV-Vis and FTIR, and then it was coated onto surface of electrode by dripping and its thickness was measured. Performance of PVA-GO gas sensor was studied by measuring water and coffee vapors (samples coffee used were from Sidomulyo, Gumitir and Garahan plantations). PVA-GO composite was successfully synthesized, showing UV-Vis absorption in reference wavelength range 260 and 300 nm. Meanwhile, IR spectra PVA and GO also appear on composite, with vibrations by group O-H, C=O, C=C, C-O-C, and C-H stretching which were observed on 3290,67, 1721,64, 1650,12, 1086,96, and 2943,03 cm-1. Sensor optimization was carried out by varying composition, and best composition was obtained at ratio of 0.75 g PVA:0.25 g GO, as indicated by conductance value of 0.3566 x 10-7 S. Sensor with thickness of 0.132 mm has highest conductance value of 0.6025 x 10-7 S, in standard measurements of coffee vapor containing 3 g of coffee/45 mL of water. Consistency of sensor preparations were carried out was successful indicated by RSD values of 3,14%-4,94% from three preparations. Sensor is also sensitive enough to detect coffee aroma as indicated by slope value of 0.0738 S.mL/g for Sidomulyo coffee. Finally, sensor is also able to distinguish aroma of coffee from 3 different plantations as indicated by conductance response, where response is 0.6265x10-7 S, 0.1723x10-7 S, and 0.08616x10-7 S for Sidomulyo, Gumitir and Garahan coffee. Lifetime is quite good with RSD values in range 3,13%-3,56% of sample measurements for 6 weeks.