Sintesis Karbon Dot Terdoping Nitrogen Dan Sulfur (N,S-CDs) Sebagai Sensor Berbasis Fluoresensi Untuk Deteksi Residu Oksitetrasiklin Pada Produk Susu Sapi

Aida Auliasari, Prof. Suherman, S.Si., M.Sc., Ph.D; Prof. Drs. Mudasir, M.Eng., Ph.D

2026 | Skripsi | KIMIA

Nanosensor karbon dot terdoping atom nitrogen (N) dan sulfur (S) (N,S-CDs) berbasis fluoresensi telah dikembangkan untuk mendeteksi residu senyawa antibiotik oksitetrasiklin pada susu sapi. Metode sintesis N,S-CDs yang digunakan adalah jalur sintesis bottom up dengan metode microwave. Sebelum N,S-CDs disintesis, dilakukan optimasi kondisi sintesisnya meliputi parameter variasi waktu, daya, dan massa prekursor asam sitrat. Variasi waktu iradiasi dilakukan pada rentang waktu 4-7 menit, sedangkan variasi daya optimum dilakukan pada rentang 100-800 W. Massa prekursor asam sitrat divariasikan berdasarkan rasionya dengan dopan thiourea sebagai sumber atom N dan S, kemudian dikarakterisasi dan diuji stabilitasnya. Selain itu, sensitivitas N,S-CDs terhadap oksitetrasiklin juga dievaluasi beserta selektivitas dan pengaruhnya terhadap interferen lainnya. Semua parameter ini dilakukan untuk mendapatkan kondisi optimum untuk mendeteksi oksitetrasiklin pada susu sapi.

Berdasarkan spektra FTIR, ditunjukkan bahwa atom N dan S telah berhasil terpasivasi di permukaan CDs dengan keberadaan vibrasi karakteristik ikatan N-H dan C-N untuk doping atom N serta S-H dan C-S untuk doping atom S. Karakterisasi dengan TEM menunjukkan bahwa N,S-CDs memiliki rata-rata ukuran 5 nm dengan beberapa bagian yang beraglomerasi. Spektra fluoresensi menunjukkan bahwa intensitas optimum diperoleh pada 6 menit; 450W; dan rasio 1:2. Pada penelitian ini mekanisme interaksi antara N,S-CDs dengan OTC dapat dikaitkan dengan proses quenching fluoresensi terutama Inner Filter Effect (IFE) dan dengan membandingkan respon fluoresensinya maka diperoleh batas deteksi (LOD) sebesar 0,026 mg L-1 dan batas kuantitasi (LOQ) sebesar 0,079 mg L-1.

A fluorescence-based nanosensor utilizing nitrogen (N) and sulfur (S) co-doped carbon dots (N,S-CDs) was developed for the detection of oxytetracycline antibiotic residues in cow's milk. The N,S-CDs were synthesized via a bottom-up microwave-assisted method. Prior to synthesis, optimization of synthesis conditions was conducted, encompassing variations in irradiation time, power, and mass of the citric acid precursor. Irradiation time was varied from 4 to 7 minutes, while optimal power was assessed across a range of 100–800 W. The mass of the citric acid precursor was varied relative to the thiourea dopant, serving as the source of N and S atoms. The optimal conditions obtained were employed for N,S-CDs synthesis, followed by characterization and stability evaluation. Furthermore, the sensitivity of N,S-CDs toward oxytetracycline was assessed, along with its selectivity and interference effects from other substances. All parameters were optimized to achieve the best conditions for oxytetracycline detection in cow's milk.

Based on the FTIR spectra, it was shown that N and S atoms had been successfully passivated on the surface of the CDs, as evidenced by the presence of characteristic N-H and C-N bond vibrations for N doping, and S-H and C-S bond vibrations for S doping. Characterization by TEM revealed that the N,S-CDs had an average size of 5 nm, with some agglomerated particles. Fluorescence spectra indicate that the optimal intensity is obtained at 6 minutes; 450 watt; and a 1:2 ratio. In this study, the interaction mechanism between N,S-CDs and OTC can be attributed to fluorescence quenching processes, particularly the Inner Filter Effect (IFE). By comparing the fluorescence responses, a limit of detection (LOD) of 0.026 mg L-1 and a limit of quantification (LOQ) of 0.079 mg L-1 were obtained.

Kata Kunci : fluoresensi, karbon dot, oksitetrasiklin, susu