SINTESIS KARBON DOT TERDOPING NITROGEN DAN SULFUR (N,S-CDs) BERBANTUAN MICROWAVE UNTUK DETEKSI H2O2 PADA SUSU SAPI

Melly Wulantika Rahman, Prof. Suherman, S.Si., M.Sc., Ph.D; Prof. Dr. Endang Tri Wahyuni, M.S.

2026 | Tesis | S2 Ilmu Kimia

Sintesis karbon dot  yang terdoping nitrogen dan sulfur (N,S-CDs) telah dilakukan untuk mendeteksi hidrogen peroksida (H2O2) pada susu sapi. N,S-CDs disintesis menggunakan microwave dengan prekursor asam sitrat, tiourea, dan formamida. Kondisi sintesis dioptimalkan dengan variasi daya dan waktu iradiasi microwave serta rasio dopan dan pelarut untuk memperoleh karakteristik optik yang optimum. Karakterisasi N,S-CDs dianalisis menggunakan spektrofluorometri, spektrofotometer UV-Vis, ATR-FTIR, spektroskopi Raman, dan HR-TEM. Kinerja sensor dievaluasi melalui pengujian stabilitas terhadap pH, ionic strength, paparan sinar UV, dan waktu penyimpanan. Selain itu, pengujian juga dilakukan terhadap sensitivitas, selektivitas, dan aplikasi pada sampel susu.

Hasil penelitian menunjukkan bahwa kondisi optimum sintesis pada daya microwave 450 W selama 90 detik dengan penambahan dopan nitrogen dan sulfur sebesar 25% serta pelarut formamida 50%. N,S-CDs yang dihasilkan memiliki  karakteristik optik yang baik dengan emisi fluoresensi biru pada panjang gelombang eksitasi 348 nm dan panjang gelombang emisi 430 nm. Probe sensor memiliki stabilitas yang baik pada rentang pH 5–9, ionic strength NaCl 0–2 M, paparan sinar UV hingga 180 menit, dan penyimpanan selama 56 hari. Penambahan H2O2 menyebabkan penurunan intensitas fluoresensi akibat mekanisme fluorescence quenching yang menghasilkan hubungan linier yang baik terhadap peningkatan konsentrasi H2O2 dengan nilai batas deteksi (LoD) sebesar 2,6103 mM dan batas kuantifikasi (LoQ) sebesar 8,7001 mM. Aplikasi sensor H2O2 pada sampel susu menunjukkan hasil %recovery yang sebanding dengan metode referensi titanium salt colorimetry sehingga mengonfirmasi potensi N,S-CDs sebagai nanosensor fluoresensi yang sederhana, cepat, dan andal untuk analisis H2O2 pada susu.

Synthesis of a nitrogen and sulfur doped carbon dots (N,S-CDs)-based fluorescent sensor for the detection of hydrogen peroxide (H2O2) in bovine milk has been carried out. N,S-CDs were synthesized using a microwave-assisted method with citric acid, thiourea, and solvent composition. The synthesis conditions were optimized by varying the microwave irradiation power, irradiation time, dopant ratio, and formamide content to obtain the optimum optical properties. The synthesized N,S-CDs were characterized using fluorescence spectroscopy, UV-Vis spectroscopy, ATR-FTIR spectroscopy, Raman spectroscopy, and HR-TEM. The sensing performance was evaluated in terms of stability under different pH conditions, ionic strength, UV irradiation, and storage time. In addition, the sensor was assessed for its sensitivity, selectivity, and applicability to milk samples.

The results showed that the optimum synthesis conditions were achieved using a microwave power of 450 W for 90 s, using 25% thiourea as the nitrogen and sulfur dopant source and 50% formamide. The synthesized N,S-CDs exhibited favorable optical properties with blue fluorescence emission at an excitation wavelength of 348 nm and an emission wavelength of 430 nm. The sensor probe showed excellent stability over a pH range of 5–9, in NaCl ionic strength of 0–2 M, under UV irradiation for up to 180 min, and during storage for 56 days. The addition of H2O2 resulted in fluorescence quenching, producing a good linear relationship with increasing H2O2 concentration, with a limit of detection (LoD) of 2.6103 mM and a limit of quantification (LoQ) of 8.7001 mM. Application of the sensor to milk samples yielded recovery values comparable to those obtained using the standard titanium salt colorimetric method, confirming the potential of N,S-CDs as a simple, rapid, and reliable fluorescent nanosensor for H2O2 determination in milk.

Kata Kunci : Karbon dot, microwave, H2O2, sensor fluoresensi, susu.