Science and Technology Development Journal

Silver Nanoparticles Synthesized from Phlogacanthus turgidus Leaf Extract: Catalytic Activity in TMB-H2O2 Redox Reactions and their Application in Hydrogen Peroxide Sensing

Su Van Dang — 2024-12-31

Introduction: Among metal nanoparticles (MNPs), silver nanoparticles (AgNPs) have partical attention due to their excellent electrical and optical properties. Notably, colorimetric sensors incorporating metal nanoparticles have garnered significant attention from scientists in biochemical analysis, offering a simple solution. Here, we report the use of AgNPs applying hydrogen peroxide (H₂O₂) sensor. Methods: The AgNPs were synthesized using Phlogacanthus turgidus leaf extract, H₂O₂ oxidized colorless TMB into blue ox-TMB, the reaction was catalyzed by AgNO₃. Measuring the resulting solution spectrophotometrically helped to determine the concentration of ox-TMB, thereby determining the concentration of H₂O₂ produced. Results: The UV-Vis spectrum of AgNPs synthesized from Phlogacanthus turgidus leaf extract exhibited a prominent absorption peak at 427 nm. The linear range was determined in 100 – 300 µM. The linear regression equation is y = 0.91574 + 3.10484×10^-4 C_H2O2 with a SD value of 0.00438. The result showed that the limit of detection (LOD) of H₂O₂ through the color reaction between the 3,3’,5,5’-tetramethylbenzidine (TMB) and H₂O₂ in AgNPs catalysis was 46.55 µM and the limit of quantification (LOQ) was 141.07 µM. Conclusion: Based on the results of optimal conditions for TMB oxidation in the presence of AgNPs, we can evaluate the applicability as a H₂O₂ sensor.

Applying zooplanktonic biological indices for assessment of water quality in the watersheds of Ray river, Baria-Vung Tau province

Tran Ngoc Diem My — 2024-12-31

The Ray River is an important river system in Ba Ria-Vung Tau Province, Vietnam, supplying water for domestic, agricultural, and industrial purposes, thereby facilitating the province's economic development. The research was executed in 2024 across 9 watersheds, comprising 5 sites on the Ray River and 4 sites on the Ray River reservoir, throughout both the rainy and dry seasons. The findings documented 111 species of zooplankton, categorized into 50 genera, 13 orders, and 5 primary groups: Protozoa, Rotatoria, Cladocera, Copepoda, and Ostracoda. The research noted variations in zooplankton communities throughout the two seasons, suggesting saline intrusion at specific locations along the Ray River during the dry season. The Shannon-Wiener biodiversity score varied between 1.95 and 3.43, whereas the Pielou Evenness index consistently exceeded 0.8. The biological indicators of zooplankton communities indicate that most aquatic systems exhibited generally clean water quality, with only two locations demonstrating moderate pollution levels (α-mesosaprobe) during the dry season. The findings indicate that the aquatic environment in the Ray River system, encompassing both the river and reservoir, satisfies the water supply criteria for supplying domestic water and irrigation water in Ba Ria-Vung Tau Province. The study suggests utilizing zooplankton as an indicator for precise water quality scenarios, owing to their sensitivity to environmental fluctuations and brief life cycles. This would also offer a cost-effective approach for environmental monitoring and management of the river system.

The Atomic Mechanism of the Melting Process of Free-standing Hexagonal Boron Nitride

Dan Lin Lieu — 2024-12-31

The atomic mechanism of the melting process of the free-standing h-BN is studied using Molecular dynamics simulation. The critical value of the Lindemann criterion for the free-standing h-BN is defined at 0.0326 which is used to classify solid-like and liquid-like atoms. The influence of the edge types on the melting process is observed based on the study of the free-standing hexagonal boron nitride (h-BN), armchair h-BN nanoribbon, and zigzag h-BN nanoribbon using molecular dynamics simulation. Due to dangling bonds at the armchair edge, the phase transition from crystalline to liquid in armchair h-BN nanoribbon occurs at a lower temperature (3700 K) than in zigzag h-BN nanoribbon (4200 K), and the free-standing configuration (4550 K). At the melting temperature, most B atoms in the zigzag h-BN nanoribbon exhibit coordination numbers of one or two, whereas most B atoms in the armchair h-BN nanoribbon and the free-standing h-BN have a coordination number of zero.

Fluorine containing chalcones as anticancer agents: Solvent-free synthesis and cytotoxicity against HepG2 cancer cells

Phuong Ho — 2024-12-31

Introduction: Chalcone analogs are commonly synthesized by the base-catalyzed Claisen-Schmidt condensation reaction of acetophenones and aromatic benzaldehydes. The shortcomings of the traditional protocols are side-products. Grinding and microwave-assisted methods under solvent-free conditions are green approaches for the preparation of chalcones. Herein, we focused on the synthesis of chalcone-based analogs bearing –F/-OCH₃/-OH groups on both A and B rings using grinding and microwave irradiation procedures. In our efforts to search for anticancer agents, fluoro-containing chalcones were subsequently assayed for cytotoxic activities against HepG2 cells.

Method: The fluorinated chalcones were synthesized using cross-aldol reactions between fluoro acetophenones and benzaldehyde analogs. Fluorinated chalcones bearing –OCH₃ at positions of the ring B were prepared by grinding reagents with solid NaOH under solvent-free condition, while fluoro-containing chalcones bearing –OH substituents in the B ring were obtained from the clay-catalyzed microwave irradiation in the absence of solvent. Chemical structures of fluorinated chalcones were elucidated by NMR and MS spectra. The inhibitory activity against HepG2 cells was evaluated through the half-maximal inhibitory concentration (IC₅₀, µM).

Results: Twelve fluorinated chalcones (1a-1c, 2a-2c, 3a-3c, 4a-4c) were successfully synthesized in 33-49% yields. Compounds 3a, 3b, 3c and 4c are novel fluoro-containing chalcones. Except for compounds 1a-1c, fluorinated chalconoids exhibited cytotoxic activities against HepG2 cancer cells with IC₅₀ values in the range 67.51-108.20 µM. Chalconoid 2a showed a highest inhibitory activity with an IC₅₀ value of 67.51±2.26 µM.

Conclusions: The grinding of reagents together prior to adding solid NaOH resulted in desired products. The clay-catalyzed microwave irradiation in the absence of solvent is effective to prepare hydroxy chalcones. Among synthesized structures by eco-friendly approaches, four fluorinated chalcones 3a-3c and 4c are novel compounds. The scaffold of 4¢-F-3-OCH₃ might contribute to the cytotoxicity against HepG2 cells.

Spray-dried Encapsulation of Roselle (Hibiscus Sabdariffa) and Evaluation of Their Potential as Rich-antioxidant Compound

Vo Minh Quan — 2024-12-31

There is a growing demand using rich-antioxidant compounds from plant extract to develop functional food products or biomedical products. In this work, we studied the impact of producing encapsulated roselle extracts with 1% w/v microencapsulated carrier as a powder rich in antioxidant properties. In particular, the roselle extract was subjected to spray drying using an acidified solution as a solvent. Combinations between maltodextrin and xanthan gum as wall materials were first tried for the roselle. Characterization of the spray-drying powder was confirmed by scanning electron microscopy (SEM), titratable acidity, anthocyanin content, and antibacterial and antioxidant activities. The results showed the addition of xanthan gum directly affects the morphology and antioxidant activities of the encapsulated materials. The particles presented a spherical shape with diameters ranging from 3 – 5 µm. The reduction of antioxidant activities and solubility were observed following the increasing concentration of xanthan gum. Thus, findings in this study have demonstrated that the obtained roselle spray drying powders can possibly be used as rich-antioxidant supplements for food, biomedical, and cosmetic industries.

Evaluation of Micro-Encapsulated Roselle Extract as a Food Colorant in Red Nata de Coco Dessert Model System

My-Duyen Ngo — 2024-12-31

Incorporating natural extracts into food products offers significant health benefits and promotes sustainable production methods. This study evaluates the incorporation of microencapsulated roselle (Hibiscus sabdariffa) extract into nata de coco, a traditional Vietnamese dessert. Anthocyanins in roselle, a subgroup of polyphenols, are notable for their vibrant colors and health benefits. By transforming extract solutions into powder form with maltodextrin and xanthan gum through spray-drying, their colors are retained, and bioavailability is improved, making them effective natural food colorants. The study demonstrated that the roselle-enhanced nata de coco exhibited high antioxidant activity and maintained anthocyanin stability. The optimal dyeing method produced samples with a pH of 2.6 to 3.2, titratable acidity of 0.45% to 0.49%, and total anthocyanin content varying from 11 to 19 mg/L. Antioxidant inhibition was approximately 49.26 ± 3.0. Stability studies of Roselle Nata de Coco (RDC) over four weeks showed consistent pH, titratable acidity, and antioxidant properties with minimal anthocyanin degradation. The encapsulated roselle powder enhances the color, nutritional value, and health benefits of nata de coco, demonstrating its potential as a stable natural food colorant. These findings suggest that RDC is a stable functional food ingredient with significant potential, highlighting the stability and bioactive properties of the encapsulated extract in high-water activity products.

Contamination status of surface water from urban rivers and lakes in Hanoi, Vietnam: Pollution parameters and concentrations of selected elements

Anh Quoc Hoang — 2024-12-31

Introduction: Surface water contamination is a concern in urban areas of emerging and developing countries. However, comprehensive and updated studies on the pollution status of urban rivers and lakes in Vietnam are still relatively scarce. Methods: In this study, surface water samples were collected from 5 rivers and 5 lakes in Hanoi, the capital city of Vietnam, to determine some basic pollution parameters (i.e., pH, electrical conductivity–EC, total dissolved solids–TDS, and total suspended solids–TSS) and concentrations of 15 elements. Concentrations of elements were measured by using the inductively coupled plasma-mass spectrometry (ICP-MS) method. Statistical analysis was performed to elucidate potential relationships between pollutants and samples. Results: The pH values in lake water were higher than in river water. The differences in EC, TDS, TSS, and total element concentrations between the lake and river samples were not statistically significant. Concentrations of many elements like Fe, Zn, Pb, Cu, Ni, Cr, and Sb were lower than threshold values specified by the National Technical Regulation on Surface Water Quality. However, concentrations of As and Hg can approach or even exceed the acceptable limits in some locations. Significant correlations were found between some elements and basic parameters. Conclusions: The surface water of rivers and lakes in Hanoi urban areas has been contaminated at low to moderate levels in terms of pH, TSS, and some toxic elements. Further comprehensive monitoring studies should be conducted to characterize the pollution status and ecological impacts of inorganic and organic toxicants in the Vietnamese aquatic environment.

Surface features of graft-type polymer electrolyte membranes using tapping mode atomic force microscopy analysis

Nguyen Nhat Kim Ngan — 2024-12-31

Introduction: Polymer electrolyte membrane fuel cell (PEMFC) is a promising renewable energy technology, which is increasing commercial use in transportation, stationaries, and portable devices. In the PEMFC, the surface nature of PEMs plays a key role in interfacial degradation of membrane-electrolyte assembly and proton conductance and thus, highly impacting on the performance and stability of PEMFC. Consequently, the objective of this work is to investigate the surface features of graft-type poly(styrenesulfonic acid) (PSSA)-grafted poly(ethylene-co-tetrafluoroethylene) polymer electrolyte membranes (ETFE-PEMs) using tapping mode atomic force microscopy (TM-AFM). Methods: The ETFE-PEMs are prepared using the pre-irradiation-induced grafting of styrene onto the ETFE film and subsequent sulfonation. All the ETFE-PEMs and their precursor films (original ETFE and polystyrene (PS) grafted-ETFE films) are characterized by the TM-AFM. Results: Upon the grafting and sulfonation process, partially grafted PS and PSSA chains are found to be accumulated on the sample surface at a low grafting degree (GD) of 21% and more graft chains are diffused into the bulk of membranes at higher GDs of 36 and 57%. The polystyrene grafts are immiscible mostly with the amorphous phase of the pristine ETFE film, leading to the formation of new amorphous phase containing of only PS grafts. The sulfonation resulted in the microphase separation between the backbone of ETFE and side chain of PSSA but the final surface morphology of membranes can be determined at the grafting step. Conclusions: The surface morphology characteristics are more or less ascertained at the grafting process but not the sulfonation one. The PSSA grafts of ETFE-PEMs are dispersed on the membrane surface, favoring for the connection of ionic domains, leading to the increase in proton conductance on the membrane surface. It is suggested that the ETFE-PEMs exhibit the advantages in the membrane-electrode interfacial properties for PEMFC application due to its low accumulated surface in the low GD.

Phenolic compounds from the bark of Aglaia lawii and their cytotoxic activity against HepG2

Quan Hoang Pham — 2024-12-31

Introduction: Aglaia lawii is a large tree belonging to the Meliaceae family. In traditional medicine, the stem bark is used as a vermicide while the leaves are used for the treatment of headache. Studies on the chemical constituents of this species in Vietnam and its biological activity, especially its ability to treat liver cancer, are still limited. This work describes the isolation and structure elucidation of six phenolic compounds from an ethyl acetate extract of the bark of A. lawii as well as the evaluation of cytotoxic activity against HepG2.

Methods: The extracts were prepared by extracting the dried ground bark using Soxhlet extraction. Isolation was performed using column chromatography over silica gel, RP-18 and using gel permeation chromatography over Sephadex LH-20. Chemical structures were elucidated using spectroscopic methods (1D- and 2D-NMR, HR-ESI-MS and IR) and comparison of spectral data with those in literature. Cytotoxic activity against HepG2 human liver cancer cells was evaluated in vitro using the MTT assay.

Results: Six phenolic compounds, palmarumycin JC2 (1), 5-hydroxy-4',7-dimethoxyflavone (2), coniferaldehyde (3), 3-hydoxy-1-(4¢-hydroxy-3¢-methoxyphenyl)propan-1-one (4), p-hydroxybenzaldehyde (5), and vanillin (6), were isolated from an ethyl acetate extract of the bark of A. lawii collected in Dong Nai Province. Compounds 1-3 were evaluated for their cytotoxicity against HepG2 cells and the result showed that the compounds exhibited weak effects or no activity.

Conclusion: All the isolated compounds have been reported from this species for the first time. It is also the first report on the cytotoxicity of 1-2 against HepG2 cells although the compounds displayed weak effects.

Keywords: Aglaia lawii; phenolic compounds, cytotoxicity, HepG2

Synthesis of Ag/CuO/rGO hybrid structure towards the applications in visible light photodetectors

Duc Anh Ngo — 2024-12-31

Introduction: 2D reduced graphene oxide (rGO) has become a key material in optoelectronic devices due to its outstanding electrical properties and stability. However, the application potential of rGO in such devices is still limited due to its low light absorption ability (especially in the visible region). Hence, this study aims to overcome this problem by synthesizing an Ag/CuO/rGO hybrid structure. Methods: Herein, while rGO was formed via a hydrazine vapor reduction, Ag and CuO were synthesized through simple, low-cost chemical techniques. Results: Our results revealed that compared to bare rGO and CuO/rGO samples, the hybrid Ag/CuO/rGO has remarkably higher absorption in the visible region. Besides, the fabricated Ag/CuO/rGO also demonstrated sensitivity toward blue light excitation, with good performance and stability. Conclusion: We hope that our study can further enable research on the application of rGO in the optoelectronic sector.

Detecting Mental Health Issues in Students Using Limited ECG Data from Portable Devices.

Nhat Tan Le — 2024-12-31

Introduction: Mental health issues are a growing concern among university students, significantly affecting their academic performance and quality of life. Recognizing stress in students under academic pressure is crucial for improving their well-being. This study aims to identify stress patterns through heart activity, which is closely correlated with mental health issues.

Methods: An experiment was designed involving 49 participants during exam time, using low-cost portable devices based on ECG sensors. The high quality of recorded data was confirmed by good average QRS correlation metrics. To enhance the dataset and address the problem of imbalanced data, a Generative Adversarial Network (GAN) was employed to generate synthetic ECG data in two scenarios: GAN 1, which synthesized the minority class only, and GAN 2, which synthesized both classes. A comprehensive set of Heart rate variability (HRV) indices from time, frequency, and non-linear domains were extracted for analysis. Finally, two 2 ensemble learning models were utilized to perform the stress recognition based on the HRV features set.

Results: Through cross-validation and random-split validation, our findings demonstrated significant improvements in model performance with the addition of synthetic data. Specifically, GAN 1 data improved recall, effectively capturing more stress instances, while GAN 2 data enhanced precision, ensuring accurate stress identification. The Random Forest model showed exceptional capability in managing class imbalance, further validating the effectiveness of our approach. Additionally, the use of a natural stressor, such as exam time, confirmed the practical applicability of our models.

Conclusion: These results underscore the potential of dataset enrichment in machine learning, particularly in health-related applications, and provide a robust foundation for future research and real-world validation of synthetic data's benefits in stress recognition tasks.