VNUHCM Journal of Science and Technology Development

Effect of Applied Voltage on the Electrochemical Copolymerization of Thiophene and Dithenopyrrole Derivatives

Cam H. T. Nguyen — 2023-05-27

The linear sweep voltammetry potentiostatic approach was employed to electrochemically synthesize the conjugated copolymers P(3HT-random-HPDTP) at three distinct applied voltages (1.4, 1.435, 1.6 V). In relation to their synthesis conditions, their chemical structural, optical, and electrical properties were investigated and compared using Fourier transform infrared (FTIR) spectroscopy, UV‒Vis absorption spectroscopy, and cyclic voltammetry (CV). The results indicated that choosing a suitable applied voltage in the electropolymerization process significantly improved the electrochemical stability and lowered the HOMO level of the conjugated copolymer.

Improving Vietnamese Fake News Detection based on Contextual Language Model and Handcrafted Features

Khoa Dang Pham — 2023-05-20

Introduction: In recent years, the rise of social networks in Vietnam has resulted in an abundance of information. However, it has also made it easier for people to spread fake news, which has done a great disservice to society. It is therefore crucial to verify the reliability of news. This paper presents a hybrid approach that uses a pretrained language model called vELECTRA along with handcrafted features to identify reliable information on Vietnamese social network sites.

Methods: The present study employed two primary approaches, namely: 1) fine-tuning the model by utilizing solely textual data, and 2) combining additional meta-data with the text to create an input representation for the model.

Results: Our approach performs slightly better than other refined BERT methods and achieves state-of-the-art results on the ReINTEL dataset published by VLSP in 2020. Our method achieved a 0.9575 AUC score, and we used transfer learning and deep learning approaches to detect fake news in the Vietnamese language using meta features.

Conclusion: With regards to the results and analysis, it can be inferred that the number of reactions a post receives, and the timing of the event described in the post are indicative of the news' credibility. Furthermore, it was discovered that BERT can encode numerical values that have been converted into text.

Synthesis of a unique oligomer by means of the thiol-maleimide reaction of extending 1,1'-(methylenedi-4,1-phenylene) bismaleimide chains for the employment of self-healing polymers

Nguyen Khai Hoang Nguyen — 2023-05-28

Introduction: The Diels-Alder reaction of maleimide and furan groups is being exploited in self-healing materials; hence, it is no wonder that with the ownership of the former, 1,1'-(methylenedi-4,1-phenylene) bismaleimide (BMI) counts as a potential candidate in this area. However, it displays certain discernible demerits arising from its inflexible structure. Furthermore, the maleimide group, in all likelihood, easily takes part in the Michael addition reaction with thiol groups under basic conditions. It is crucial that this element opens the door for this ingredient to be amended with a view to weathering its shortcomings. The goal of this research is to modify the structure of BMI to create a new oligomer with maleimides at the end of its chains. Method: The oligomer was synthesized by means of the reaction of the maleimides of BMI and the thiol groups of 2,2’-(ethylenedioxy) diethanethiol (dithiol) with the support of triethylamine (TEA). In addition, an investigation into the possibility of this reaction happening without the base catalyst was carried out. The application of a wide assortment of modern measurements ranging from 1H-NMR and FT-IR to GPC provided some useful data about the molecular weight and whether the reaction occurred. Result: According to the information, the formation of the oligomer owning the maleimide and thiol terminal functions was observed with the help of TEA over the 24-hour timescale at room temperature, whereas that with a lack of this catalyst is impossible. Conclusion: The research will make a major contribution to the creation of new healable polymers reliant on the Diels-Alder mechanism in the foreseeable future.

Enhancement of the crystalline phase in poly(vinylidene fluoride) by using the electrospinning technique and graphene oxide composition

Thuy Thi Thu Nguyen — 2023-05-27

Introduction: Poly(vinylidene fluoride) (PVDF) possesses some unique characteristics, such as piezoelectric, ferroelectric, and pyroelectric properties. The β crystalline phase of PVDF exhibits the strongest piezoelectric and pyroelectric properties. In this study, the influence of the electrospinning process and graphene oxide (GO) composition on the β-phase formation of PVDF fibers is reported. Methods: The morphology of electrospun PVDF and PVDF/GO fibers was observed using a scanning electron microscope (SEM). Characteristics of the crystal phase of electrospun PVDF and PVDF/GO fibers were analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Results: The PVDF fiber fabricated by the electrospinning technique had a crystallinity degree that increased by more than 117% compared to that of the precursor PVDF powder. The X-ray diffraction results show that the entire α phase of PVDF was converted to the β phase due to elongation deformation under the force of an electrical field during the electrospinning process. The presence of GO also induced the formation of the β phase of PVDF due to the interaction between the atomic groups on the surface of GO sheets and on the PVDF molecular chains. Conclusion: Both the electrospinning process and GO led to an increase in the crystallinity of PVDF. PVDF/GO nanofibers with crystallinity degrees above 60% can be applied in many fields, such as water purification membranes, air filters, energy harvesting materials, biosensors, and catalysts.

Molecular dynamics simulation of pressure effect on silicene nanoribbons

Huy Anh Huynh — 2023-05-05

Introduction: In 2D materials, the boundary of silicene formed as nanoribbons plays an essential role in synthesis and can be controlled to achieve different characteristics. Our study aims to investigate the structural preference depending on the pressure tolerance and boundary dependency. Methods: The main methodology used in our study is molecular dynamics simulation with Stillinger Weber potentials. Our simulation was carried out on 2D models of honeycomb silicene obtained through high and low pressurized cooling from the liquid state and then heat annealing for a decent time. The final configuration of silicene will be investigated in terms of structures and thermodynamic properties. Results: We found that the effect of the cooling process under high pressure formed a 4-fold ring structure, while at low pressure, 2D honeycomb networks were recovered but with different degrees of defects depending on the boundary condition. The main difference between several transitions of 2D silicene is discussed via the evolution of total energy and the change in coordination number and bond-ring distribution. Conclusions: This study provides insights into the dependency of the structure of silicene on the pressure and boundary, represented by the first-order transition at low pressure and a congregation of disordered low-numbered rings into the ordered tetragonal formation at high pressure. Notably, our results have shown that silicene nanoribbon materials can be controlled by pressure to obtain unfamiliar structures such as pentagonal and tetragonal networks.

Viet Nam With Developing A Service Oriented Public Administration To Meet The Requirements Of New Generations Of Free Trade Agreements

Hoàng Thị Lan Phương — 2023-05-27

Free trade agreements not only offer many opportunities but also pose numerous challenges for Vietnamese businesses. Continuing to operate the current governing administrative system will not promote the initiativeness, positivity and creativity of businesses. In contrast, businesses will fail to attract foreign investors due to concerns about Vietnamese regulatory agencies interfering, imposing on production and business activities, and extremely protecting the interests of domestic enterprises. It is necessary to build a service-oriented administration, taking the satisfaction of businesses and people as the goal, promoting the ownership and capacity of businesses and people, and ensuring a healthy and equal investment and business environment in the context that Vietnam increasingly participates in the common playing fields created by new-generation free trade agreements.