VNUHCM Journal of Science and Technology Development

Enhanced Absorption Capacity of Carboxymethyl Cellulose-Derived Superabsorbent Polymers: The Role of Acrylic Acid and Acrylamide Ratios

Thi Huyen Ngo — 2025-09-11

Biodegradable superabsorbent polymer (BioSAP) synthesized from natural polymers has potential for agricultural use because of its three-dimensional hydrophilic network, which can absorb, swell, and retain a huge amount of water and salt solution. In this study, BioSAP was prepared by graft copolymerization of acrylic acid (AA) and acrylamide (AM) to the pineapple-leaf-derived car- boxymethyl cellulose using the inverse suspension method with diﬀerent AA and AM ratios. The absorbent capacity and release performance of BioSAP for water and salt solution depend strongly on the AA/AM ratio. Among these samples, BioSAP with an AA/AM molar ratio of 6 exhibited the most stable gel structure and the maximum absorbencies for distilled water and salt solutions. This may be because AA can enhance the absorption and release ability of BioSAP, while AM can improve its gel stability. In addition, the presence of AA/AM in BioSAP enhances the water retention ability of the soil, leading to an increase in the storage time of water in the soil and improving the moisture content of the soil. These ﬁndings indicate that BioSAP synthesized with this AA/AM molar ratio is suitable for agricultural ﬁelds, improving soil moisture and helping plants grow better.

RESEARCH AND SYNTHESIS OF POPCORN-LIKE Ag@CZZ NANOMATERIAL FOR DETECTING TEBUCONAZOLE

Nhu Hoa Thi Tran — 2025-08-20

Abstract

Introduction: Pesticide residues in food remain one of the unresolved concerns in recent years. Porous materials such as metal organic frameworks (MOFs), when combined with the localized surface plasmon resonance (LSPR) effect of silver nanoparticles (Ag NPs), enable label-free detection of analyte concentrations with high sensitivity. This approach is particularly effective in the detection of tebuconazole (TB) residues, a fungicide known for its persistence and potential health risks contributing to environmental protection and food safety.

Methods: Ag NPs were synthesized in a pre-prepared Zeolitic imidazolate framework (ZIF) solution, using a chemical reduction method, achieving relatively high uniformity. For surface-enhanced Raman scattering (SERS) applications, a self-assembled monolayer coating was fabricated on filter paper (FP) substrates by taking advantage of the strong absortion of Ag@Co-Zn-ZIF (Ag@CZZ) nanocomposites to cellulose fibers.

Results: UV–vis spectroscopy revealed that the LSPR wavelength of the Ag NPs is 419 nm, while XRD analysis confirmed the (111) plane of the face-centered cubic (FCC) crystalline structure of Ag. Morphologically, the synthesized nanoparticles exhibit a unique “popcorn-like” structure with an average size of approximately 408 nm, as demonstrated by field-emission scanning electron microscopy (FESEM). Energy-dispersive X-ray spectroscopy (EDS) shows the presence of elements constituting the popcorn-like Ag@CZZ. Moreover, characteristic vibrations from the ZIF structure were identified in the Raman spectra. The FP/Ag@CZZ SERS substrate for monitoring TB concentration was successfully established, with a limit of detection (LOD) calculated to be 3.08 × 10^-8 M.

Conclusion: Leveraging the LSPR effect of Ag NPs and the structural properties of ZIF, a simple and rapid fabrication method was used to develop a flexible and effective FP/Ag@CZZ SERS substrate. This platform exhibited high sensitivity in detecting and monitoring changes in TB concentration, opening promising opportunities for improving the detection limits of pesticide residues in agricultural and environmental monitoring.

Keywords: Co-Zn-ZIF, Ag@CZZ, Popcorn-like, Tebuconazole

Effect of electrospinning parameters on the morphology of polyurethane nanofibers and their shape memory behaviors

Thuy Thi Thu Nguyen — 2025-09-05

Introduction: We investigated the effect of various electrospinning parameters on the morphology and average diameter of shape memory polyurethane (PU) nanofibers. The shape memory performance of an electrospun PU nanofiber mat was also studied.

Methods: The examined parameters included solution concentration (16–22 wt%), applied voltage (8–10 kV), feed rate (0.8–1.2 mL/h), needle-to-collector distance (18–20 cm), and solvent mixture (N,N-dimethylformamide (DMF), DMF/chloroform, and DMF/ethyl acetate). The morphology of electrospun PU nanofibers was observed using a scanning electron microscope. The shape memory properties of the electrospun PU nanofiber mat obtained at the optimal parameters were investigated using a thermomechanical cyclic testing program.

Results: Bead-free nanofibers with an average diameter of 600 nm were obtained using a 20 wt% PU solution in DMF, an applied voltage of 10 kV, a feed rate of 1.0 mL/h, and a needle-to-collector distance of 20 cm. Using DMF/chloroform and DMF/ethyl acetate as solvents, uniform PU nanofibers were obtained at a PU concentration of 16 wt%. The electrospun PU nanofiber mat exhibited excellent shape memory properties, achieving shape recovery ratios and shape fixity ratios exceeding 90%.

Conclusions: A PU nanofiber mat was successfully fabricated by electrospinning and is considered a potential material for shape memory applications.

Valuation of provisioning ecosystem services from tram chim national park, Dong Thap province, Vietnam

Ngan Truong Nguyen — 2025-09-05

The final report of the project on the rational use of wetland natural resources in Tram Chim National Park (TCNP) with community participation during the 2012-2016 period has provided many interesting statistical data on the total number of households exploiting resources, average income, total products obtained, types of products, estimated total revenue, etc. However, since the end of the project until now, TCNP has not updated any additional data. This article uses a survey method of farmers combined with a market-based valuation method to determine the types of resources being exploited belonging to 4 groups of provisioning service: food, fuel, medicinal plants, and decorative materials. To assess the value, the article estimates the proportion of households and the average amount of resources exploited from 70 survey questionnaires. Results achieved: (i) Type of resources: there are 11 types of resources being exploited; (ii) Exploitation rate: food - 90% of surveyed households, medicinal plants 5.5%, fuel 3.5%, and decorative materials 1.0%; (iii) Annual exploitation volume: 284.3 tons of food, 2.0 tons of fuel, 1.4 tons of medicinal plants, and 1.2 ton of decorative materials; (iv) The estimated total value is 17.94 billion VND per year, with an average of 18,1 (±2,3) million VND/household/month. The results from the article demonstrate that TCNP is still providing a significant value of resource supply to society.