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Synthesizing Nanosturctures

In recent years, nanostructures have increased in demand for many reasons, such as their vast applications on consumer technology, material sciences, and pharmaceuticals. There is specific interest in the topic of using nanostructures in solar energy systems. This is because of the small scale of nanostructures, which leads to unique interactions with light. For instance, electromagnetic waves oscillate electrons on the surface of these nanostructures more easily, which allows for the generation of electrical energy. For this reason, nanostructures can be used in photovoltaic cells to transform light energy to electrical energy. However, manufacturing these nanostructures can be a harmful and expensive process. In our research, we experimented with using Deep Eutectic Solvents as means to create Gold Nanostructures in a less harmful and more cost-effective manner. Deep Eutectic Solvents are room-temperature-ionic liquids, with partial positive and partial negative charges, which form a lattice shape among molecules. Deep Eutectic Solvents were used as the main medium of the reaction between tetrachloroauric acid. It was concluded that the synthesis using Deep Eutectic Solvents created Gold Structures because of signs indicative of a chemical reaction; however, the characterization of these solutions yielded inconclusive results. Our results show widespread aggregation of nanostructures, and contamination from unexpected chemicals.

 

Introduction

  • •The nano-scale is between the lengths of 1-100 nanometers (nm) in any x, y, or z dimension.

  • •Nanostructures can serve as excellent catalysts in chemical reactions, and have various applications in consumer technology.

  • To create these nanostructures, deep eutectic solvents (DES’s) were used to synthesize nanostructures made of gold (AuNS’s).

  • DES’s are an ionically bonded compound in a liquid state whose molecular structures allows for great polarity and a specific arrangement between molecules.

  • This arrangement of molecules provides a grid-like system for nanostructures to form between, especially between reline and ethaline.

Materials and Methods

  • Previous research shows that it is possible to synthesize various anisotropies of gold nanowire-networks/ gold nanostructures that form in a wire/network system, through the use of reline and ethaline. 

  • Reline and ethaline were prepared by mixing together choline chloride with urea and with ethylene glycol respectively. The mixtures were heated via hot plates under stirring until homogeneous.

  • To perform the syntheses, both tetrachloroauric acid or HAuCl4 and sodium borohydride or NaBH4 were mixed with both reline and ethaline individually and then centrifuged to spin down the particles.

  • In order to characterize the AuNS’s, ultraviolet visible spectroscopy (UV-Vis) was performed, which measured the absorption patterns of the molecules, and a scanning electron microscope  or SEM was utilized to examine the images of the gold nanostructure aggregates and particles

  • Throughout the steps of the synthesis of AuNS’s, it was found that ethaline crystalized at room temperature (to combat this, the ethaline solution was constantly placed on a hot plate).

  • The formation of gold nanostructures was indicated by the color change, but UV Vis lead to no conclusive results because of the ethaline’s rapid crystallization. After centrifugation, these structures formed visible aggregates.

  • Antithetically, the reline acted as a room temperature liquid, which allowed for much better characterization of the AuNS samples.

  • Ethaline was found to be unstable at room temperature and pressure likely due to water altering the integrity of the lattice structure.

  • The UV Vis data did not clearly show a characteristic gold peak at the 500nm wavelength most likely due to the crystallization of ethaline during the measurement. AuNS’s were still synthesized.

  • The UV Vis data from reline proves that AuNS’s were synthesized because of the characteristic gold peak at 500 nm.

  • SEM images (as pictured above) show clear gold aggregates but in order to find individual particles, the centrifugation process must be revised and if possible, excluded.

  • For future projects, to avoid crystallization of ethaline, the water content must significantly be reduced.

  • These structures, though, prove that they can be used for all applications, especially pharmaceuticals and solar renewable energy.

Results and Conclusion

 
 

References

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(6)      International Standards Organization. Nanotechnologies-Vocabulary-Part 2: Nano-objects, ISO/TS 80004-2. https://www.iso.org/obp/ui/#iso:std:iso:ts:80004:-2:ed-1:v1:en (accessed July 1, 2018).

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(8)      Government, A. NICNAS Chemical Gazette October 2010. 2010, No. C, 14.

(9)      Wagle, D. V. Rapid #: -12733515 Deep Eutectic Solvents : Sustainable Media for Nanoscale and Functional Materials. 2018, 47 (8), 2299–2308.

(10)    Chirea, M.; Freitas, A.; Vasile, B. S.; Ghitulica, C.; Pereira, C. M.; Silva, F. Gold Nanowire Networks: Synthesis, Characterization, and Catalytic Activity. Langmuir 2011, 27 (7), 3906–3913.

(11)    Mahyari, F. A.; Tohidi, M.; Safavi, A. Synthesis of Gold Nanoflowers Using Deep Eutectic Solvent with High Surface Enhanced Raman Scattering Properties. Mater. Res. Express 2016,  

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