Modifikasi Molecularly Imprinted Polymer dan Doping untuk Meningkatkan Sensitivitas dan Selektivitas Sensor Terpenoid dan Amoniak berbasis Quartz Crystal Microbalance

Nur Aisyah Humairah, Prof. Dr. Eng. Kuwat Triyana, M.Si; Dr. Ahmad Kusumaatmadja, M.Sc; Prof. Drs. Roto, M.Eng., Ph.D.

2023 | Disertasi | S3 Ilmu Fisika

Sensitivitas dan selektivitas sensor menjadi dua parameter penting yang sangat menarik untuk terus dikaji. Dalam penelitian ini sensor berbasis quartz crystal microbalance (QCM) dimodifikasi chitosan (Cs) untuk mendeteksi terpenoid dan dengan polyvinyl acetate (PVAc) mendeteksi amoniak. Metode molecular imprinted polymer (MIP) diterapkan untuk meningkatkan selektivitas sensor, sementara itu doping boric acid (BA) dan citric acid (CA) digunakan meningkatkan sensitivitas sensor amoniak. Uji scanning electron microscopy (SEM) dan energi dispersive X-Ray spectroscopy (EDAX) digunakan mengkonfirmasi terbentuknya struktur nanofiber, sedangkan fourier transform spectroscopy Infrared (FTIR) digunakan mengkonfirmasi terjadinya pelepasan template (terpenoid atau amoniak). Selain sensitivitas dan selektivitas, karakteristik lain dari sensor yang diamati mencakup linieritas, stabilitas, waktu respons, limit of detection (LoD) dan limit of quantification (LoQ). Pada sensor terpenoid, penerapan MIP meningkatkan sensitivitas sensor tiga kali lipat dibanding tanpa metode MIP, yakni masing-masing adalah (41±4)×10^(-3) Hz/ppm terhadap alpha-pinene dan (412±7)×10^(-2) Hz/ppm terhadap gamma-terpinene. Sama halnya sensor amoniak, penerapan metode MIP meningkatkan sensitivitas sensor tiga kali lipat dibanding tanpa metode MIP dengan penambahan doping BA dan CA, yakni (243±2)×10^(-3) Hz/ppm dan (356±9)×10^(-2) Hz/ppm. Karakteristik lainnya berupa koefisien determinasi, waktu respons, LoD dan LoQ, untuk sensor alpha-pinene adalah (996±5)×10^(-3); 75s; (24±1) ppm; dan (73±3) ppm untuk sensor gamma-terpinene adalah (98±23)×10^(-2); 83 s;  (22±4) ppm; dan (69±11)  ppm, untuk sensor amoniak doping 6BA adalah (999±9)×10^(-3); 37 s; (27±1) ppm; dan (31±1) ppm, dan sensor amoniak doping CA (99±26)×10^(-2); 36 s; (22±0,3) ppm; dan (44±11)  ppm.

The sensitivity and selectivity of sensors are crucial parameters that require continual investigation. This study employed quartz crystal microbalance (QCM)-based sensors, modified with chitosan (Cs) to detect terpenoid and with polyvinyl acetate (PVAc) to detect ammonia. To enhance sensor selectivity, the molecularly imprinted polymer (MIP) method was employed while doping with boric acid (BA) and citric acid (CA) was utilized to increase sensor sensitivity for ammonia sensor. Scanning electron microscopy (SEM) and energy dispersion X-Ray spectroscopy (EDAX) were used to confirm the nanofiber structure formation, while Fourier transforms Infrared spectroscopy (FTIR) was employe to verify template release (terpenoid and ammonia). In addition to sensitivity and selectivity, this study also assessed other sensor characteristics, including linearity, stability, response time, the limit of detection (LoD), and the limit of quantification (LoQ). Result showed that MIP application increased sensor sensitivity three-fold for terpenoid specifically (41±4)×10^(-3)  Hz/ppm for alpha-pinene and (412±7)×10^(-2) Hz/ppm for gamma-terpinene. Meanwhile, for ammonia detection, MIP application increased sensor sensitivity three-fold, specifically (243±2)×10^(-3) Hz/ppm and (356±9)×10^(-2) Hz/ppm when using BA and CA doping, respectively. Other characteristics such as coefficient of determination, response time, LoD and LoQ for alpha-pinene sensor were (996±5)×10^(-3), 75s; (24±1)  ppm; and (73±3)  ppm, while those gamma-terpinene sensors which were (98±23)×10^(-2); 83 s; (22±4) ppm; and (69±11)  ppm, respectively. For the ammonia sensor doping BA, the values were (999±9)×10^(-3);  37 s; (27±1) ppm; and (31±1) ppm, and for ammonia doping CA, the values were (99±26)×10^(-2); 36 s; (22±0,3) ppm; and (44±11)  ppm.

Kata Kunci : Sensor, Quartz Crystal Microbalance, Molecularly Imprinted Polymer, Chitosan, Doping, Terpenoid, Amoniak.