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Abstrak :
Zinc Oxide (ZnO) is an important semiconductor material due to its broad applications, such as in the fields of electronics, optoelectronics, photocatalysts, and solar cells. The main purpose of this work was to investigate the effect of pressure in post-hydrothermal treatment on crystallinity enhancement, crystallite growth, and band gap reduction of ZnO nanoparticles, which could be expected to improve their performance as the semiconductor oxide layer in the dye-sensitized solar cell application. For this purpose, ZnO nanoparticles have been successfully synthesized through the precipitation method, followed by a sequence of thermal treatments including drying, calcination, and Post-hydrothermal Treatment (PHT). For increasing the crystallinity of ZnO nanoparticles, PHT was carried out with a pressure variation of 1 and 3 bar. The resulting nanoparticles were further characterized with X-Ray Diffraction (XRD), Ultra-Violet Visible (UV-Vis) spectroscopy and a Scanning Electron Microscope (SEM). The study showed that by increasing the PHT pressure from 1 to 3 bar caused an adverse effect on the crystallinity, i.e. the crystallite size of ZnO nanoparticles slightly decreased from 27.42 to 26.88 nm. This was expected to be due to the increase of the boiling point of water causing less effective of vapor generated to improve the crystallinity by a cleavage mechanism on the inorganic framework. The band gap energy (Eg), however, was found to increase slightly from 3.25 to 3.26 eV, respectively. Considering the obtained properties, ZnO nanoparticles in this study have the potential to be used as the semiconductor oxide layer in the dye-sensitized solar cells.

Abstrak :
Pada penelitian ini, telah dilakukan sintesis nanopartikel TiO2 melalu proses sol─gel dengan variasi rasio air terhadap prekursor (Rw) yaitu 0.85, 2.00 dan 3.50 selama proses formulasi yang kemudian diikuti perlakukan termal lanjut berupa pengeringan, anil dan pasca-hidrotermal. Karakterisasi XRD dilakukan untuk mengukur besar ukuran kristalit nanopartikel yang dihasilkan. Dari hasil perhitungan, metode pasca-hidrotermal menghasilkan produk dengan ukuran kristalit paling tinggi dibandingkan perlakukan anil dan pengeringan. Ukuran kristalit tertinggi dimiliki sampel Rw = 3.50 cair dengan besar ukuran kristalit 8,566 nm, diikuti Rw = 3.50 gel sebesar 7,614 nm, Rw = 2.00 sebesar 6,853 nm dan Rw = 0.85 sebesar 6,527 nm. Lebih jauh lagi, nanotube TiO2 difabrikasi melalui teknik hidrotermal dengan melarutkan nanopartikel TiO2 hasil perlakuan anil dan serbuk P-25 Degussa ke dalam larutan alkalin sodium hidroksida berkonsentrasi tinggi di dalam otoklaf tersegel. Detil struktur dan morfologi sampel diuji dengan SEM. Hasil investigasi menunjukkan bahwa nanopartikel dengan Rw = 2.00 berhasil dibuat menjadi nanotube dengan diameter 115─269 nm.

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In this study, TiO2 nanoparticles was synthesized via sol−gel process with various water to inorganic precursor ratio (Rw) of 0.85, 2.00 and 3.50 upon sol preparation, followed with subsequent drying, conventional annealing and posthydrothermal treatments. The resulting nanoparticles were characterized using XRD to measure the crystallite size. On the basis of results obtained, the posthydrothermal resulted TiO2 samples with largest crystallite size in comparison to drying and annealing. The largest crystallite size of hydrothermally treated samples is Rw = 3.50 cair with 8,566 nm, followed by Rw = 3.50 gel with 7,614 nm, Rw = 2.00 with 6,853 nm and Rw = 0.85 with 6,527 nm. Furthermore, nanotube TiO2 have been fabricated through a hydrothermal technique where anneal treated nanopartikel TiO2 sol-gel and P-25 Degussa nanopowder was dissolved in highly concentrated alkaline solution of sodium hydroxide (NaOH) in a sealed autoclave. The detail of the structure and morphology of the resulting nanotubes were characterized using SEM. The result of investigation showed that nanoparticle with Rw = 2.00 can be fabricated became nanotubes with its diameter 155─269 nm.