SIMPLE FABRICATION OF Al-DOPED ZnO NANORODS FOR PHOTOCATALYTIC METHYLENE BLUE DEGRADATION WITHIN A pH CONTROLLED AQUEOUS MATRIX

Indra Bayumukti Samodra, Prof. Indriana Kartini, S.Si., M.Si., Ph.D; Prof. Drs. Sri Juari Santosa, M.Eng., Ph.D

2026 | Skripsi | KIMIA

Seng oksida (ZnO) berbentuk nanorod telah banyak menarik perhatian sebagai fotokatalis untuk degradasi zat warna organik karena memiliki celah pita (bandgap) yang lebar, stabilitas kimia yang tinggi, serta morfologi satu dimensi yang mendukung transport pembawa muatan secara efisien. Dalam penelitian ini, nanorod ZnO murni dan terdoping aluminium (Al) disintesis melalui metode dekomposisi termal sederhana menggunakan prekursor seng asetat dihidrat, dilanjutkan dengan impregnasi Al dan proses anil sekunder, dengan variasi konsentrasi doping Al sebesar 0,5%, 1%, dan 3%. Material yang disintesis dikarakterisasi secara struktural dan morfologis menggunakan difraksi sinar-X (XRD), mikroskop elektron payaran emisi medan (FE-SEM), mikroskop elektron transmisi (TEM), spektroskopi sinar-X dispersi energi (EDX), dan spektroskopi inframerah transformasi Fourier (FTIR), sedangkan sifat optiknya dievaluasi menggunakan spektroskopi reflektansi difusi UV-Vis.

Kinerja fotokatalitik dievaluasi melalui degradasi zat warna methylene blue (MB) di bawah iradiasi UV pada kondisi pH terkontrol, yaitu pH 8. Hasil penelitian menunjukkan bahwa seluruh sampel tetap mempertahankan struktur wurtzite heksagonal ZnO, dengan doping Al secara progresif mengurangi panjang dan diameter nanorod serta menyebabkan distorsi kisi kristal yang terukur. Celah pita optik menurun dari 3,284 eV (ZnO murni) menjadi minimum 3,247 eV pada doping 1% Al, yang diatribusikan pada penyempitan celah pita akibat pembentukan status donor, sebelum meningkat tajam menjadi 3,393 eV pada 3% Al akibat dominasi efek Burstein-Moss; namun, modifikasi celah pita ini belum cukup untuk memperluas respons fotokatalitik material ke wilayah cahaya tampak.

Pengujian fotokatalitik mengonfirmasi bahwa sampel 1% Al-ZnO menunjukkan efisiensi degradasi tertinggi (k_app = 0,0279 menit?¹, penyisihan MB sebesar 97,08?lam 120 menit) di bawah iradiasi UV, mengikuti kinetika orde-satu semu, sedangkan performa menurun pada 3% Al akibat pembentukan cacat yang melampaui batas doping optimum. Aktivitas fotokatalitik di bawah cahaya tampak tetap minimal pada seluruh sampel, menunjukkan bahwa material yang difabrikasi berfungsi sebagai fotokatalis aktif-UV. Temuan ini menunjukkan bahwa doping Al pada konsentrasi optimum sekitar 1?pat secara signifikan meningkatkan kinerja fotokatalitik nanorod ZnO berbasis UV, untuk degradasi methylene blue dalam sistem akuatik terkontrol pH.

Zinc oxide (ZnO) nanorods have attracted considerable attention as photocatalysts for organic dye degradation due to their wide bandgap, high chemical stability, and one-dimensional morphology that facilitates efficient charge carrier transport. In this study, undoped and aluminum (Al)-doped ZnO nanorods were synthesized via a simple thermal decomposition method using zinc acetate dihydrate as the precursor, followed by Al impregnation and secondary annealing, with Al doping concentrations varied at 0.5%, 1%, and 3%. The synthesized materials were characterized structurally and morphologically using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR), while optical properties were evaluated using UV-Vis diffuse reflectance spectroscopy.

 Photocatalytic performance was assessed through the degradation of methylene blue (MB) dye under UV irradiation at a controlled pH of 8. The results showed that all samples retained the hexagonal wurtzite ZnO structure, with Al doping progressively reducing nanorod length and diameter and inducing measurable lattice distortion. The optical bandgap decreased from 3.284 eV (pure ZnO) to a minimum of 3.247 eV at 1% Al, attributed to donor-state-induced bandgap narrowing, before increasing sharply to 3.393 eV at 3% Al due to the dominant Burstein-Moss effect; however, this bandgap modification was insufficient to extend the material's photo response into the visible-light region.

 Photocatalytic testing confirmed that 1% Al-ZnO exhibited the highest degradation efficiency (k_app = 0.0279 min?¹, 97.08% MB removal within 120 minutes) under UV irradiation, following pseudo-first-order kinetics, while performance declined at 3% Al due to excessive defect formation beyond the optimal doping threshold. Visible-light photocatalytic activity remained minimal across all samples, indicating that the fabricated material functions primarily as a UV-active photocatalyst. These findings demonstrate that Al doping at an optimum concentration of approximately 1?n significantly enhance the UV-driven photocatalytic performance of ZnO nanorods, offering a simple and cost-effective strategy for methylene blue degradation in pH-controlled aqueous systems.

Kata Kunci : ZnO nanorods, Al doping, thermal decomposition, photocatalysis, methylene blue, bandgap engineering, pH-controlled degradation