Subject Number :S-19-JI-0024
Support Type : Technical support (except the training)

Proposal Title (English) : HR-TEM and EDX mapping for Ag/Au core/shell nanoparticles and metal
NP/Grqphene quantum dot nanohybrid
Username (English) : Wei-Hung Chiang
Affiliation (English) : Department of Cehmical Engineering, National Taiwan University of Science and Technology

1. Summary
Graphene quantum dots (GQDs) are zero-dimensional graphene materials with lateral size below 100 nm. Due to their superior properties such as good bio-compatibility, high photostability and tunable optical properties, making them promising for emerging applications. Moreover, the tunable optical and physical properties by adjusting size and designing functional groups on GQDs make it become useful materials in different applications. The main purpose of the research is GQDs structural characterization. from TEM analysis
2. Experimental
HRTEM images were obtained using STEM JEM-ARM200F and HR-TEM H-9000NAR. TEM specimens were prepared by drop casting sample solutions on copper grid (CF300-Cu carbon film 300 mesh copper grid from Electron Microscopy Sciences)
3. Results and Discussion
TEM analysis was taken to understand the morphology and crystalline of the product. In the results, the product was proved to be crystallized nanodot with particle size less than 10 nm. The size distribution analysis of Figure 1a&c provided in Figure 1b&d shown that longer reaction time resulted in bigger particles synthesized. The lattice fringes observed through high resolution TEM (HRTEM) images tell that these particles have crystalline structure. The fast Fourier transform (FFT) image shown in Figure 1f indicates the crystal structure of Figure 1e matched the graphite crystal viewing from [011], while Figure 1h indicates the crystal structure of Figure 1g matched the graphite crystal viewing from [-1-21]. Graphene-like structure was then proved by using the results combining the fast Fourier transform (FFT) images of single particle and the simulation results of graphite crystal from two different viewing.

Figure 1. Characterization of GQDs synthesized by microplasma using TEM. (a-b) images and size distribution of synthesized GQD1 (c-d) images and size distribution of synthesized GQD2 (e-h) graphene-like structural characterizations by HR-images and simulation combining two planes. GQD1 was synthesized by microplasma at 6.5 mA discharge current for 60 minutes while GQD2 was synthesized for 90 minutes.

4. Others
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5. Publication/Presentation
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6. Patent
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