1. Full name:     Sai Cong Doanh                                                2. Sex: Male

3. Date of birth: 18/8/1985                                                          4. Place of birth: Hanoi

5. Admission decision number: 3713/QĐ-ĐHKHTN dated on 09/09/2014, by Rector of VNU University of Science;

6. Changes in academic process:

- Extended time by decision No 596/QD-DHKHTN dated on 06/3/2018 and 4728/QĐ ĐHKHTN dated on 28/12/2018, by Rector of VNU University of Science;

- Decision No. 3994/QD-DHKHTN dated on 25/12/2020 by Rector of VNU University of Science that sending PhD. student back to local/office.

7. Official thesis title: Synthesis, characteristic and potential application of core shell nanostructure base on metal (Au, Ag) – semiconductor (Cu₂O, CuO).

8. Major: Solid state of Physics                                      9. Code: 9440130.02

10. Supervisors:

            Prof. Dr. Ngac An Bang

            Dr. Pham Nguyen Hai

11. Summary of the new findings of the thesis

Cuprous oxide (Cu₂O) and gold (Au) nanoparticles have been successfully fabricated by chemical reduction method with narrow size distribution and uniformity.

The effect of some technological parameters on the fabrication process of the Au/Cu₂O core/shell structure (such as concentration of Au nanoparticles, surfactants, and reducing agents, etc) has been systematically studied to actively fabricate them. The thickness of Au-Cu₂O core/shell structures ranges from 9 nm to 200 nm.

The effect of the shell thickness on the plasmon resonance of the gold nano-core as well as the effect of the quantum size effect on the band gap of the shell has been studied.

CuO nanorods were synthesized by thermal oxidation method. Annealing at 500 ^oC in 2h offers nanorods of high density and uniformity.

The fabricated materials have been examized for applications in several fields such as photocatalysis and surface enhanced Raman scattering. Initial results show that the MB decomposition rate of Au/Cu₂O is twice as fast as that of bare Cu₂O crystals of the same size. The CuO/Ag core/shell structure was used as the SERS substrate to detect MB at low concentrations. The detection limit of the fabricated SERS substrate is as low as 10^-10 M.

The experimental data was fitted with several theoretical models to enlighten the physics insight of the phenomena in the as prepared nanomaterials.

12. Practical applicability, if any:

The fabricated samples are potential sensor probes to detect toxic substances at low concentrations based on surface-enhanced Raman scattering effect.

Applications in environmental remediation.

13. Further research directions, if any

In the future, we continue our research to improve the ability to detect methylene blue at lower concentrations by thermal annealing or composite structures with composite metal nanostructures. Expanding research objects, toward detection of antibiotic residues in water environment.

Systematic study on the methylene blue degradation by different allotropes of Cu₂O, metal-semiconductor composite structures. Expanding the research topic to other semiconductor materials for decomposition of antibiotic residues in the aquatic environment.

14. Thesis-related publications:

Sái Công Doanh, Ngạc An Bang (2015), “chế tạo và nghiên cứu tính chất vật liệu Au/Cu₂O”, Hội nghị Vật lý Chất rắn và Khoa học Vật liệu Toàn quốc.

Sai Cong Doanh and Ngac An Bang (2016), “Synthesis and Characterization of Au-Cu₂O Core-Shell Nanoparticles”, International Symposium on Frontiers in Materials Science.

Sai Cong Doanh, Pham Nguyen Hai, Ngac An Bang (2017), “Synthesis and Optical Properties of Cu₂O and Au-Cu₂O Core-shell Particles”, VNU Journal of Science: Mathematics – Physics 33(4), pp. 73-79.

Cong Doanh Sai, An Bang Ngac (2018), “Effect of core-shell structure on optical properties of Au-Cu₂O nanoparticles”, Physica B: Condensed Matter 532, pp. 216-220.

Thi Ha Tran, Manh Hong Nguyen, Thi Huyen Trang Nguyen, Vu Phuong Thao Dao, Phuong Mai Nguyen, Viet Tuyen Nguyen, Nguyen Hai Pham, Van Vu Le, Cong Doanh Sai, Quang Hoa Nguyen, Trong Tam Nguyen, Khac Hieu Ho, Quoc Khoa Doan (2019), “Effect of annealing temperature on morphology and structure of CuO nanowires grown by thermal oxidation method”, Journal of Crystal Growth Volume 505, pp. 33-37.

Cong Doanh Sai, Vu Phuong Thao Dao, Viet Tuyen Nguyen, An Bang Ngac, and Nguyen Hai Pham (2019), Gold nanoparticles decorated CuO nanorods: a novel, ultra-sensitive and uniform surface-enhanced Raman scattering substrate, Joint 5th International Symposium on Frontiers in Materials Science and 3rd International Symposium on Nanomaterials, Technology and Applications.

Thi Ha Tran, Manh Hong Nguyen, Thi Huyen Trang Nguyen, Vu Phuong Thao Dao, Quang Hoa Nguyen, Cong Doanh Sai, Nguyen Hai Pham, Thanh Cong Bach, An Bang Ngac, Trong Tam Nguyen, Khac Hieu Ho, Hyeonsik Cheong, Viet Tuyen Nguyen (2020), “Facile fabrication of sensitive surface enhanced Raman scattering substrate based on CuO/Ag core/shell nanowires”, Applied Surface Science, 509, pp. 145325.