Sintesis dan Karakterisasi ZnO QUANTUM DOTS untuk Degradasi Malachite Green dalam Larutan Berair

Abstract

Abstrak

ZnO QDs berhasil disintesis melalui metode kopresipitasi menggunakan prekursor seng asetat dihidrat [Zn(CH₃COO)₂·2H₂O] dan agen pengendap natrium hidroksida (NaOH) 0,4 M. Campuran larutan diaduk hingga homogen selama kurang lebih 2 jam, disentrifugasi, dicuci dengan akuades hingga mencapai pH netral, dan dikeringkan pada suhu 80 °C selama 4 jam. Karakterisasi fasa kristal dan ukuran partikel dianalisis menggunakan X-Ray Diffraction (XRD), sedangkan identifikasi ikatan kimia permukaan menggunakan spektroskopi Fourier Transform Infra Red (FTIR). Hasil analisis XRD mengonfirmasi bahwa ZnO QDs yang terbentuk memiliki fasa hexagonal wurtzite murni sesuai dengan standar JCPDS No. 36-1451 dengan tingkat kristalinitas mencapai 100%. Ukuran rata-rata kristal ZnO QDs yang dihasilkan adalah sebesar 2,377 nm, membuktikan keberhasilan reduksi material hingga skala titik kuantum. Spektrum FTIR menunjukkan puncak serapan tajam yang dominan pada daerah bilangan gelombang di bawah 439,9 cm⁻¹, yang merupakan sidik jari molekuler dari vibrasi regangan ikatan logam-oksigen (Zn–O). Selain itu, terdeteksi pula pita serapan gugus hidroksil (O–H) permukaan pada bilangan gelombang 3421,87 cm⁻¹ dan 1490,77 cm⁻¹ akibat adanya molekul air lingkungan yang teradsorpsi secara fisik. Proses fotokatalis berhasil mendegradasi zat pewarna malachite green hingga 98,6% selama 300 menit. Karakteristik struktural skala kuantum serta eksistensi gugus fungsi permukaan yang melimpah ini memberikan indikasi potensi fungsional ZnO QD untuk dikembangkan lebih lanjut pada aplikasi fotokatalitik.

Kata Kunci: ZnO, quantum dots, malachite green, fotoaktalis, limbah zat warna

Abstract

Zinc oxide quantum dots (ZnO QDs) were successfully synthesized using the coprecipitation method with zinc acetate dihydrate [Zn(CH₃COO)₂·2H₂O] as the precursor and 0.4 M sodium hydroxide (NaOH) as the precipitating agent. The solution mixture was stirred until homogeneous for approximately 2 hours, followed by centrifugation, washing with distilled water until neutral pH was achieved, and drying at 80 °C for 4 hours. The crystal phase and particle size were characterized using X-ray Diffraction (XRD), while the surface chemical bonds were identified using Fourier Transform Infrared (FTIR) spectroscopy. The XRD results confirmed that the synthesized ZnO QDs exhibited a pure hexagonal wurtzite crystal phase in accordance with the JCPDS standard No. 36-1451, with a crystallinity of 100%. The average crystallite size of the synthesized ZnO QDs was 2.377 nm, confirming the successful reduction of the material to the quantum dot scale. The FTIR spectrum revealed a dominant sharp absorption peak below 439.9 cm⁻¹, corresponding to the characteristic stretching vibration of the Zn–O metal–oxygen bond. In addition, absorption bands associated with surface hydroxyl (O–H) groups were observed at 3421.87 cm⁻¹ and 1490.77 cm⁻¹ due to the presence of physically adsorbed environmental water molecules. The photocatalytic process successfully degraded malachite green dye by up to 98.6% within 300 minutes. The quantum-scale structural characteristics and the presence of abundant surface functional groups indicate the promising potential of ZnO QDs for further development in photocatalytic applications.

Keywords: ZnO, quantum dots, malachite green, photocatalysis, dye wastewater