The goal of the project is to fabricate SERS substrates in the form of silver (Ag) and gold (Au) nanostructures with enhanced Raman scattering effect to detect traces of plant protection drugs ( Plant protection) glyphosate, dithiocarbamates and carbendazim with thresholds of detection less than 40 ppm (for glyphosate), 30 ppm (for dithiocarbamates) and 20 ppm (for carbendazim) (meet the requirements of the circular regulating maximum limits residues of plant protection drugs in food 50/2016 / TT-BYT issued by the Minister of Health on December 30, 2016).

- Theoretical results:

• We have successfully fabricated SERS substrates in the form of AgNPs/Si by electrochemical deposition method using ethanol-based solution and investigated the effects of fabrication conditions on the morphological structure of AgNPs and found fabrication conditions to obtain AgNPs with optimal structure for SERS applications.
• We fabricated SERS substrates in the form of AuNFs/Si by electrochemical deposition method combined with silver seed and investigated the effect of fabrication conditions on the morphological structure of AuNFs and found fabrication conditions to obtain AuNFs with optimal structure for SERS applications.

- Applied results:

• We used two types of SERS substrates of AgNPs/Si and AuNFs/Si to analyze and detect traces of three pesticides: thiram, glyphosate and carbendazim, and found that both SERS substrates are responding very well to the analysis of the above pesticides with the detection limit lower than the maximum residue level allowed by the Ministry of Health regulations. Of which, AgNPs/Si SERS gave better analytical efficiency AuNFs/Si substrates.

- The thesis has built a new fabrication process to create an orderly arrangement of silver nanoparticles on the same layer on the Si surface with very good uniformity, density and distance between particles. Nano silver is very narrow. Silver nanoparticles on Si fabricated by this procedure give very good analytical efficiency when used as SERS substrate to analyze pesticides such as glyphosate, dithiocarbamates and carbendazim at very low concentrations (ppb size).

- The thesis has also built the fabrication process of gold nanoparticles on Si by electrochemical deposition method combined with the use of silver germs. The silver nanoparticles fabricated have good uniformity, small nano flower size and thick flower density. The Si yellow nanoparticles fabricated by this procedure also allow the analysis of the pesticides dithiocarbamates, glyphosate and carbendazim at low concentrations when used as SERS substrates. However, the analytical efficiency of gold nanoparticle SERS substrates on Si was much less than that of SERS substrates in the form of silver nanoparticles on Si.

- Scientific papers in referred journals (list):

1. Tran Cao Dao and Truc Quynh Ngan Luong, Fabrication of uniform arrays of silver nanoparticles on silicon by electrodeposition in ethanol solution and their use in SERS detection of difenoconazole pesticide, RSC Adv., 2020, 10, 40940 (IF = 3,07)
2. Tran Cao Dao, Truc Quynh Ngan Luong, Tuan Anh Cao and Ngoc Minh Kieu, High-sensitive SERS detection of thiram with silver nanodendrites substrate, Adv. Nat. Sci.: Nanosci. Nanotechnol. 10, 2019, 025012 (4pp).
3. Đào Trần Cao, Lương Trúc Quỳnh Ngân, Vũ Thị Thư, Ứng dụng phương pháp tán xạ raman tăng cường bề mặt để phát hiện malachite green trong chè, Kỷ yếu Hội nghị Khoa học kỹ thuật đo lường toàn quốc 2020, 646 - 650.

- Patents (list): No

- Technological products (describe in details: technical characteristics, place): 10 SERS substrates with sizes of 0.6x0.6 cm2 include: 05 SERS substrates in the form of silver nanoparticles on Si that were fabricated by electrochemical deposition method and 05 SERS substrates in gold nanoparticles on Si that were made electrochemical deposition method combined with silver seed. These substrate are stored in sealed boxes with the size of 1.5x1.5 cm2, at room temperature and are now located in the laboratory of the project group (room 312B - building A2 - Institute of Materials Science, 18 Hoang Quoc Viet, Cau Giay, Hanoi).

- Other products (if applicable):
+ Process: 02 processes include:

• 01 Fabrication process of silver nanostructured arrays (Ag) used as SERS substrates to detect GPS, DTC and CBZ pesticides, together with SEM, and XRD images. The details of the procedure can be found in the report's appendix.
• 01 Fabrication process of gold nanostructured (Au) arrays used as SERS substrates for detection of pesticides GPS, DTC and CBZ, together with SEM, and XRD images. The details of the procedure can be found in the report's appendix.

+ Results of training: The results of the project are part of the content in the doctoral thesis of PhD student Kieu Ngoc Minh (Doctor thesis has been successfully defended).

With the very positive results that the project has achieved, we look forward to working on an Academy level or higher SERS project to continue to implement our research results in Products that are practical or can be analyzed more than others.