2 Nanocrystals Using a Dryfreezing Process Lucas Splingaire 1 Holly Korte 1 Udo Schnupf 2 Kazuhiro Manseki 3 Takashi Sugiura 3 Saeid Vafaei 1 1 Mechanical Engineering Department Bradley University Peoria IL USA ID: 1021158
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1. Production of Anatase TiO2 Nanocrystals Using a Dry-freezing ProcessLucas Splingaire1, Holly Korte1, Udo Schnupf2, Kazuhiro Manseki3, Takashi Sugiura3, Saeid Vafaei1* 1Mechanical Engineering Department, Bradley University, Peoria, IL, USA2Mund-Lagowski Department of Chemistry and Biochemistry, Bradley University, Peoria, IL, USA
2. IntroductionNeed for clean energy has been increasing.Dye-sensitized solar cells (DSSC) have received much attention.DSSCs utilize a mesoporous nanostructure layer to load dye molecules.Much research has been done to improve their efficiency.Can improve overall efficiency by increasing electron transport efficiency and surface area of nanostructure.
3. Anatase TiO2 Anatase titanium dioxide (TiO2) shows promise as a nanoparticle for the mesoporous layer.Small size will increase the surface area, increasing dye absorption.Will act as a semiconductor, increasing electron transport efficiency.
4. Producing TiO2Hydrothermal Process: high-temperature reaction where an aqueous mixture is heated above 100oC.Solvothermal Process: similar to hydrothermal process, but the mixture is non-aqueous.Sol-gel Method: involves creation of a precursor solution that will become a gel network.These methods all involve a high-temperature reaction, which can be unsafe and expensive.
5. Our ProcessSodium Hydroxide (NaOH) is dissolved in ultra-pure water using a sonic bath.This is mixed with Methanol (CH3OH), dimethylformamide (DMF) and titanium chloride (TiCl4)This mixture is stirred in a water bath at 40 oC for 5 days.Figure 1: The solution is created (left) and placed in a water bath (right).
6. Our ProcessThe mixture becomes white and gelatinous.The mixture is centrifuged at 4000 rpm for 15 minutes.This results in the separation of the particles from the liquid.Figure 2: The gelatinous mixture (left) is placed in a centrifuge (center). The liquid is separated from the nanoparticles (right).
7. Our ProcessThe liquid is discarded, and the gel is placed in tubes.The tubes are placed in liquid nitrogen to freeze the particles and prevent more crystals from growing.Figure 3: The gel is placed in tubes (left) that are then placed in liquid nitrogen (right).
8. Our ProcessThe caps are removed, and the tubes are covered with a filter and placed in a jar.The jar is attached to a dry-freeze apparatus, and the frozen gel is subjected to 200 mTorr for 24 hours.This produces the powdered TiO2 nanoparticles.Figure 4: The tubes are covered with a filter (left) and placed in a dry-freeze device (center). The resulting nanoparticles are a powder (right).
9. Our ProcessThe characteristics of the TiO2 samples were observed with X-ray diffraction (XRD) and transmission electron microscopy (TEM).
10. ResultsBased on XRD patterns, the nanoparticles were identified as anatase.Figure 5: XRD pattern of the nanoparticles.
11. Nanoparticle SizeThe nanoparticles had sizes of less than 5 nm.Figure 6: TEM image of the nanoparticles.
12. ConclusionsOur research has shown anatase TiO2 semiconductor nanoparticles can be synthesized using a low-temperature hydrothermal reaction involving a dry-freeze process.