1. Full name: Nguyen Long Tuyen                                  2. Sex: Male

3. Date of birth: 13/02/1980                                            4. Place of birth: Phu Tho

5. Admission decision number: No. 3972/QĐ-ĐHKHTN dated 24/11/2016, by Rector of VNU University of Science.

6. Changes in academic process: Extension decisions number 567/QĐ-ĐHKHTN dated 14/2/2020 and 318/QĐ-ĐHKHTN dated 01/2/2021 by Rector of VNU University of Science.

7. Official thesis title: Fabrication and investigation of some properties of iron and manganese metal oxides/graphene composite nanomaterials

8. Major: Solid State Physics                                                     9. Code: 9440130.02

10. Supervisors:            Supervisors 1: Assoc. Prof. Dr. Pham Quoc Trieu

                                    Supervisors 2: Dr. Nguyen Ngoc Dinh

11. Summary of the new findings of the thesis

- Fabrication of FexOy/graphene and MnOx/graphene multicomponent composite materials using plasma electrochemical method, applied in photocatalysts for environmental treatment and as supercapacitor electrodes.

- The iron oxide, manganese oxide/graphene composites materials have been shown to enhance the MB decomposition efficiency and the electrochemical properties compared with the non-graphene materials.

- Simultaneous combination of many components such as graphene, photocatalyst and Fe3O4 to form a multi-functional composite material with both high photocatalytic absorption efficiency and good magnetic recovery, applications in environmental treatment.

12. Practical applicability, if any:

The research's aims is to fabricate multi-component composite materials using plasma electrochemical method. The plasma electrochemical method combines the co-precipitation of oxide nanoparticles in an alkaline environment with the chemical exfoliate graphene through the interstitial filling of ions. The plasma energy helps "bind" the oxide nanoparticles to the graphene film through oxygen-containing functional groups to form a graphene-based multicomponent composite material. This approach corresponds the requirements for easy operation, happening in normal conditions, quick reaction, simple equipment, and little secondary pollution. On the other hand, this approach may be used to create a wide range of graphene-based composites with varying oxide components.

Multi-component composite materials to take advantage of the superior properties of each component have been applied in many different fields. With graphene-based multicomponent composites, the graphene film serves as a "substrate" containing the oxide nanoparticles. Graphene-based multicomponent composites are considered to be an effective method for reducing nanoparticle aggregation in solution and increasing the range of contact between the electrode and the electrolyte. Due to the large carrier mobility, the graphene film also plays a role in increasing the charge transfer capacity. The combination of many oxide materials creates heterogeneous bonds that are favorable for the photocatalytic degradation of pollutants. On the other hand, compared to non-graphene materials, it has been demonstrated that the combination of graphene improves the material's degrading performance and electrochemical properties.

Typically, the photocatalytic material is recovered through centrifugation or filtration processes. Recovery by these methods is often time-consuming and wastes material during the recovery process. The presence of Fe3O4 in the multicomponent composite provides simple recovery by magnets, resulting in no secondary contamination. In particular, the combination of many components such as graphene, photocatalyst and Fe3O4 at the same time to form a multifunctional composite material with both good photocatalytic ability and magnet recovery ability, applied in environmental treatment and is still a new problem in the country. The quantity of investigations on this material family is very limited. The effect of plasma discharge time, amount of catalyst material was also evaluated. Further electrochemical studies were also performed to evaluate applicability.

The graphene/metal oxide composite material system is oriented for application in photocatalysts for environmental treatment and as supercapacitor electrodes. The obtained results are the first step in the research to fabricate multi-component materials by plasma electrochemical method. Materials systems with varied oxide components are being developed to improve the photocatalytic or electrochemical degradation performance of the materials.

13. Further research directions, if any

The research of the thesis is the first step in the research and fabrication of graphene/metal oxide composites by plasma electrochemical method, which is applied in photocatalysts for environmental treatment and as supercapacitor electrodes. These results will be further developed with other well-characterized oxide components incorporating graphene to enhance the material's performance.

The combination of graphene and nanomaterials can be investigated for high-sensitivity sensing applications.

14. Thesis-related publications:

[1]. Nguyễn Long Tuyên, Phạm Quốc Triệu, Nguyễn Ngọc Đỉnh, Hà Xuân Linh, Phan Ngọc Hồng, Phan Ngọc Minh, Đặng Văn Thành (2020), "Chế tạo vật liệu tổ hợp graphen/Mn3O4 bằng phương pháp hóa siêu âm kết hợp plasma ứng dụng cho quang xúc tác phân hủy thuốc nhuộm da cam trong nước", Vietnam J. Chem.  58 (6E12), 196-200.

[2]. Nguyễn Long Tuyên, Phạm Quốc Triệu, Nguyễn Ngọc Đỉnh, Nguyễn Quốc Dũng, Lê Trọng Lư, Phan Ngọc Minh, Nguyễn Đình Dũng, Nguyễn Tuấn Hồng, Phan Ngọc Hồng (2020), "Nghiên cứu chế tạo vật liệu tổ hợp Mn3O4/graphen bằng phương pháp điện hóa plasma dưới sự hỗ trợ của siêu âm định hướng ứng dụng làm điện cực cho siêu tụ", Vietnam J. Chem.  58 (5E12), 265-269.

[3]. Nguyễn Long Tuyên, Phạm Quốc Triệu, Nguyễn Ngọc Đỉnh, Nguyễn Thành Trung (2021), “Chế tạo vật liệu composite graphene/MnO2 bằng phương pháp điện hóa có sự hỗ trợ của plasma ứng dụng trong quang xúc tác phân hủy thuốc nhuộm cam trong nước”,  Proceeding of Advances in Optics, Photonics, Spectroscopy & Applications XI.

[4]. Nguyen L.T., Pham Q.T., Nguyen N.D., Nguyen T.T., Dang V.T. (2022), "Synthesis of MnO2/Graphene Nanocomposites using Plasma Electrolysis Method for Photocatalytic Degradation of Methyl Orange Dye in Water", VNU Journal of Science: Mathematics-Physics  Vol. 38 (2). https://doi.org/10.25073/2588-1124/vnumap.4679

[5]. Tuyen N.L., Toan T.Q., Hung N.B., Trieu P.Q., Dinh N.N., Do D.B., Van Thanh D., Nguyen V.-T. (2023), "Simultaneous precipitation and discharge plasma processing for one-step synthesis of α-Fe2O3-Fe3O4/graphene visible light magnetically separable photocatalysts", RSC advances  Vol. 13 (11), pp. 7372-7379. Doi: 10.1039/D2RA06844C.