VNUHCM Journal of Science and Technology Development

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

2025-09-11T19:19:09+07:00

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

2025-08-20T10:19:29+07:00

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

2025-09-05T18:35:46+07:00

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.

Synergistic Au/Ag-based SERS platform for sensitive detection of malachite green

2025-09-18T09:44:11+07:00

Introduction: Malachite green (MG), a toxic and carcinogenic triphenylmethane dye widely used in aquaculture, has been restricted in many regions due to health and environmental concerns; however, it remains prevalent in some areas because of its low cost and strong eﬃcacy. Although various methods have been employed to detect MG, surface-enhanced Raman scattering (SERS) oﬀers rapid, high-sensitivity analysis by leveraging noble metal nanostructures and their localized surface plasmon resonance.
Methods: The SERS method for detecting MG leverages the localized surface plasmon resonance
(LSPR) of gold (Au) and silver (Ag): these noble metal nanoparticles (NPs) create ``hot spots'' that concentrate electromagnetic energy. When MG molecules are adsorbed onto the Au/Ag surface, their Raman scattering signal is signiﬁcantly ampliﬁed, allowing for detection at low concentrations. By employing a multilayer structure containing Au and Ag, the LSPR eﬀect is optimized, resulting in a higher detection eﬃciency compared to single-layer metal substrates.
Results: Characterization via UV-Vis spectroscopy and XRD conﬁrmed that Au and Ag NPs exhibit distinct plasmon absorption peaks (407 and 526 nm, respectively) and the (111) lattice plane at 2q = 38.2◦. HR-TEM and FE-SEM revealed that the Au NPs are spherical (30.46-nm diameter), and the Ag NPs measure 20 nm in diameter. SERS experiments with MG indicated that the P/Au/Ag substrate provides the highest enhancement, detecting MG down to 10−9 M.
Conclusions: The P/Au/Ag substrate for SERS-based MG detection was successfully fabricated and characterized, achieving a detection limit of 10−9M. The robust multilayer structure, boosted by the synergy between Au and Ag, holds signiﬁcant potential for trace-level detection of various contaminants in environmental monitoring and food safety.

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

2025-09-05T18:55:37+07:00

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.

Development a method to determine Per- and Polyﬂuoroalkyl substances (PFAS) in total suspended particulate matter (TSP) by UPLC-MS/MS

2025-09-18T09:06:01+07:00

Per- and poly-fluoroalkyl substances (PFAS) are persistent organic pollutants in many industrial and consumer products, such as pesticides, textiles, and food packaging. Although PFAS are widely used, knowledge about their occurrence in ambient particulate matter and the associated health risks remains limited. The objective of this study was to develop a sensitive, accurate, and simple method for analysing 24 PFAS compounds in total suspended particulate matter (TSP) by HPLC-MS/MS. The target compounds included 7 perfluoroalkane sulfonic acids, 11 perfluoroalkyl carboxylic acids, and 6 perfluoroalkyl acid precursors. Various instrumental parameters were optimized, including declustering potential (DP) and collision energy (CE). The ultrasound-assisted extraction conditions for dust-bound PFAS were optimized by varying the volume of methanol (MeOH), extraction time, and temperature. The optimal condition was determined to be extraction with 4 mL of MeOH at 40 °C for 10 minutes, repeated three times. Method validation results demonstrated sub-ng/L limits of quantification (LOQs) ranging from 0.01-0.14 ng/mL, with high recoveries near the LOQs (95.5% to 114.40%) and high repeatability with %RSD values ranging from 0.1% to 12.6%. The analytical procedure was subsequently applied to assess the level of PFAS contamination in TSP samples in Ho Chi Minh City. The results showed that 22 of the 24 targeted PFAS compounds were detected in the TSP samples, highlighting the significant presence of these pollutants in the megacity.