Science and Technology Development Journal

Facile synthesis of carbon supported ternary nickel-cobalt-iron nanocatalyst for the hydrodechlorination of 2-chlorophenol

2024-03-31T13:45:01+07:00

Introduction: Chlorophenols (CPs) have become prevalent in the manufacture of herbicides, fungicides, pesticides, insecticides, pharmaceuticals, and dyes, contributing significantly to water pollution. Addressing this challenge, various treatment methods such as incineration, electrochemistry, photochemistry, biotechnology, and catalytic hydrodechlorination have been explored to reduce toxic chlorophenol contaminants. Hydrodechlorination stands out as an efficient technique for the removal of chlorine atoms. The dispersion of metal nanoparticles on supported materials significantly enhances the catalytic activity by increasing the specific surface area. Among these, carbon-supported nickel-cobalt-iron nanoparticles emerge as promising catalysts for the hydrodechlorination of 2-chlorophenol.

Method: This study employs a chemical reduction method at high temperatures under an inert gas atmosphere to synthesize carbon-supported ternary nickel-cobalt-iron nanocatalysts, aiming to detoxify soil and water from pesticide residues. The physicochemical properties of these nanocatalysts were characterized using energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Their catalytic activity was assessed through gas chromatography with a flame ionization detector (FID).

Results: The analysis revealed that metallic nanoparticles are uniformly dispersed on the carbon support, with particle sizes ranging from 10 to 60 nm and an average size of 30 nm. The hydrodechlorination (HDC) of 2-chlorophenol (2-CP) achieved satisfactory conversions under various reaction conditions.

Conclusion: The carbon-supported nickel-cobalt-iron nanoparticles demonstrated effective catalytic activity for the hydrodechlorination of 2-chlorophenol, highlighting their potential for application in the treatment of chloroorganic contaminations in the future.

Polycyclic aromatic hydrocarbons (PAHs) in sediment environments in Vietnam: Analytical methods and contamination status

2024-03-31T13:56:33+07:00

Introduction: Polycyclic aromatic hydrocarbons (PAHs) are prevalent organic pollutants that garner attention due to their toxicity and carcinogenic properties. These hydrophobic compounds tend to accumulate in the organic components of sediments, posing significant ecological risks.

Methods: This study synthesizes analytical methodologies and assesses the contamination status of PAHs in Vietnamese sediments through a review of previous studies complemented by recent findings from our research group. Various extraction techniques, including Soxhlet extraction, pressurized liquid extraction, continuous solid-liquid extraction, and ultrasonic extraction, were employed using organic solvents of low to moderate polarity (e.g., hexane, acetone, toluene, dichloromethane). Purification was achieved via column chromatography using sorbents like silica gel, alumina, and Florisil, followed by gel permeation chromatography. Separation and analysis were primarily conducted through gas chromatography/mass spectrometry (GC/MS).

Results: PAHs were detected in all samples, with concentrations ranging from 33 to 6400 ng/g, indicating widespread contamination. The sources of PAHs in Vietnamese sediments appear to be predominantly urban and informal waste processing areas. The levels of sedimentary PAHs in Vietnam are on par with those reported in other Asian countries, with the majority of PAHs being traced back to pyrogenic sources, as opposed to petroleum products.

Conclusions: Our findings offer a detailed understanding of the distribution, patterns, and potential sources of PAHs in Vietnamese sediments. The notably higher concentrations of PAHs in urban and waste processing sites underscore the urgency of implementing effective management and remediation strategies. The study advocates for further monitoring of PAHs and related pollutants to fully elucidate their contamination scope, origins, and ecological consequences.

A simple method to estimate the pKa values of four fluorescent proteins based on measuring their pH-dependent absorbance spectra

2024-03-31T15:54:16+07:00

Introduction: The Nobel Prize in Chemistry 2014 greatly recognized the application of fluorescent proteins (FPs) in superresolution imaging techniques. Subsequently, there has been a significant surge in FP-related investigations. Reversibly photoswitchable fluorescent proteins (rsFPs) are currently attracting much interest from scientists worldwide because of their unique ability to switch between bright and dark states. The pH-dependent photophysical behavior of rsFPs is mostly controlled by the equilibrium between four distinct states of the chromophores in FPs: trans-protonated, trans-deprotonated, cis-protonated, and trans-deprotonated. Thus, the pKa values of rsFP in general and its chromophore, in particular, are crucial factors in determining the fluorescence output of the settings containing rsFPs in different environments.

Methods: Here, we measured the absorbance spectra of four rsFPs in various buffers with different pH values to estimate their chromophore pKas. The relationship between the absorbance peak values for the anionic chromophore and pH is plotted, resulting in a sigmoid curve. Then, the apparent pKa of the chromophore is obtained by determining the inflection point of this curve.

Results: The pKa values for the cis-chromophores of two rsFPs (GMarsQ and Skylan-S) were obtained. Specifically, the pKa values for the trans-state of the chromophore in three rsFPs (Dronpa, GMarsQ, and rsEGFP2) were also estimated; these values have rarely been published.

Conclusions: This approach is quite straightforward but effective, enabling us to quickly estimate the pKa values of FPs generally and rsFPs specifically.

Biofilm biosynthesis of Priestia megaterium M1VB5 strain Muc Son Thanh Hoa paper mill

2024-03-31T16:33:23+07:00

Introduction: Strain M1VB5, isolated from slime in paper machine pipes, is studied for its role in slime formation. This slime, comprised of microorganisms, binds and adheres to pipes, potentially leading to clogs, process inefficiencies, and machinery contamination.

Methods: We investigated the biological characteristics and gene sequencing of M1VB5, focusing on its biofilm biosynthesis capabilities under varying sucrose concentrations, temperatures, pH levels, and time periods.

Results: M1VB5 exhibited adaptability across a broad range of conditions, thriving at temperatures between 15-55°C and pH levels from 5 to 9, with up to 7% salinity tolerance. Capable of utilizing diverse carbon sources, M1VB5 efficiently biosynthesized extracellular enzymes, including CMCase, cellulase, xylanase, amylase, protease, and chitinase. Identified as Priestia megaterium (Gram-positive), it demonstrated significant biofilm formation, producing 36.4 g/L EPS and forming a 53.73 g/100g biofilm on PVC at a sucrose concentration of 100 g/L. Optimal biofilm production was observed at pH 8, with 28.40 g/L EPS and a biofilm mass of 59.61 g/100g PVC, and at 37°C, where EPS and biofilm weights reached 23.60 g/L and 63.78 g/100g PVC, respectively. The strain maintained steady biofilm production from day 4 to 14.

Conclusion: M1VB5's versatile carbon source usage, wide temperature and pH range tolerance, and diverse enzyme production facilitate its growth and development. Its significant biofilm and EPS production capabilities contribute to its dominance in slime formations, offering insights for managing slime in industrial paper mill environments.

Investigate the influence of a CagA-negative Helicobacter pylori strain, GD13, on nonhomologous end joining-mediated repair of proximal DNA double-strand breaks in GCV6 cells

2024-03-31T17:18:51+07:00

Mammalian cells infected with Helicobacter pylori show an accumulation of DNA double-strand breaks (DSBs). Previous studies have shown that the virulence factor CagA of H. pylori induces genomic instability in host cells. Most DSBs in infected cells are repaired by nonhomologous end-joining (NHEJ) pathways. Indeed, impairment of NHEJ-mediated DSB repair may lead to genetic alterations and contribute to the development of gastric cancer. Nonetheless, the impacts of H. pylori and its virulence factor, CagA, on the efficacy of NHEJ are poorly defined. This study aimed to reveal the effect of GD13, a CagA-H. pylori strain isolated in Vietnam, on the NHEJ-mediated repair of DSBs in host cells. For this purpose, we utilized GCV6 cells with an NHEJ-reporter substrate, which has been proven to be an appropriate model for evaluating the repair efficiency of NHEJ in H. pylori-infected cells. The level of interleukin-8 released into the cell culture supernatant was measured by ELISA. Our findings suggest that the reference CagA+ 26695 strain impaired the NHEJ-mediated repair of double-strand breaks (DSBs), whereas the GD13 strain has not exhibited any discernible effect thus far. In addition, H. pylori strain GD13 triggered a lower level of interleukin-8 secretion in GCV6 cells than did the CagA-positive strain 26695.

Impacts of basis sets, solvent models, and NMR methods on the accuracy of 1H and 13C chemical shift calculations for biaryls: a DFT study

2024-03-31T17:32:36+07:00

Introduction: Biaryls are core structures composed of chiral ligands, organocatalysts, biologically active natural products and biopolymer lignins. In this study, the effects of basis sets, solvent models, and NMR methods on the accuracy of ¹H/¹³C NMR chemical shift calculations for biaryl structures were evaluated.

Methods: All calculations were performed using Gaussian09. The GIAO NMR results were observed and extracted using GaussView05. To reduce the systematic error of the calculations, linear regression analysis of the calculated chemical shifts versus the experimental shifts was performed.

Results: The tested basis sets showed good ¹H/¹³C results, with CMAE values as low as 0.0425 ppm and 1.09 ppm for ¹H and ¹³C, respectively. The use of solvent models significantly increased the accuracy of the ¹H chemical shift calculations. The GIAO method produced more accurate results than did the IGAIM and CSGT methods.

Conclusion: This study recommends 6-31G(d,p) and DGDZVP basis sets, IEMPCM and CPCM solvent models, and GIAO NMR methods for the accurate prediction of ¹H and ¹³C chemical shifts for biaryls, assisting in their full structural assignments.

Measuring the efficiency of the Republic of Korea’s cultural diplomacy in Vietnam under Moon Jae-in’s presidency (2017-2022) and its potentialities

2024-03-31T13:36:19+07:00

As soon as the new president of the Republic of Korea was elected in 2017, Moon Jae-in anchored the New Southern Policy (NSP), which targeted southern Asian countries and expanded South Korea’s strategic presence in the Asia-Pacific Ocean. As such, the ROK continued to adopt a public diplomacy policy and empowered Korean culture in Southeast Asian countries, including Vietnam. This article aims to generalize Moon Jae-in’s policy on cultural diplomacy and his application in Vietnam as a case study. I employed Joseph Nye’s soft power and cultural diplomacy concept while adopting a qualitative method to collect official information from the ROK’s homepages and assess diplomatic results. The central argument of this article is that Moon Jae-in considers cultural diplomacy a key element of the NSP for promoting Korean culture and bolstering a strategic presence in Vietnam and Southeast Asia. The ROK attempted to graft K-pop, movies, Korean customs, Korean languages, and Korean cuisine onto the Vietnamese concept and seek an upgrade of Vietnamese Korean cultural exchanges and the frequent organization of cultural events. Hence, an upgrade between the ROK and the Socialist Republic of Vietnam (SRV) to a Comprehensive Strategic Partnership in December 2022 marked an achievement of cultural diplomacy. I also argued that this attempt has a tonic effect on continuing the ROK cultural diplomacy under Yoon Suk Yeol’s presidency and on the foreseeable chance of both the SRV and the ROK in cultural diplomacy.

Investigating the effect of synthesis parameters on the structure and upconversion luminescent properties of NaYF4:Tm,Yb for anticounterfeiting printing ink

2024-03-31T15:08:23+07:00

Introduction: In this study, NaYF4:Tm,Yb upconversion microparticles were prepared by a hydrothermal method.

Methods: The effects of fabrication parameters such as rare earth concentration, reaction temperature and reaction time on the structure and luminescence properties of the materials were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). Depending on the reaction temperature and time, the morphology of NaYF4:Tm,Yb is either a nanoparticle or a branched structure.

Results: The crystallite size is approximately 70 nm and remains almost unchanged with increasing reaction temperature and time. These NaYF4:Tm,Yb powders strongly emit at 450 nm and 798 nm. In addition, the surface of the UCMPs was also modified with maleic anhydride to improve their dispersibility in solvents and binding to biological molecules.

Conclusion: Printing ink based on UCMPs modified with maleic anhydride and polyamide for screen printing was prepared. The printed patterns on paper and polymer substrates glow blue light under LED excitation at 980 nm, and they are completely transparent in daylight.

Synthesis of Co3O4 electrodes by electrochemical deposition for water splitting reaction

2024-03-31T16:20:42+07:00

Introduction: The use of Ni foam substrates for the growth of catalysts is a common practice in electrochemical water splitting reactions, although their stability in some electrolytes can be problematic, hindering the scalability of synthesis. This study aims to explore alternative substrates for catalyst growth, focusing on cobalt oxide (Co3O4) due to its potential in enhancing electrochemical water splitting efficiency.

Methods: Cobalt oxide (Co₃O₄) was synthesized on various conductive substrates including fluorine-doped tin oxide (FTO), indium-doped tin oxide (ITO), and carbon cloth (CC), employing electrochemical deposition techniques. The morphological and crystalline properties of the Co₃O₄ coatings on these substrates were characterized and analyzed to understand their influence on the catalyst's performance in water splitting reactions.

Results: The electrochemical deposition resulted in a more condensed coverage of Co₃O₄ on the CC substrate, attributed to the crystal's oriented aggregation. The crystallization and lattice development of Co3O4 varied significantly across different substrates, exhibiting high crystallization on FTO and ITO substrates but poorer crystallization on the CC substrate. Notably, the Co₃O₄/CC electrode demonstrated superior performance in hydrogen evolution reaction, achieving the lowest overpotential of -382 mV at a current density of 10 mA cm^-2.

Conclusion: The findings suggest that carbon cloth (CC) presents a promising alternative to Ni foam substrates for the growth of Co₃O₄ catalysts in electrochemical water splitting applications. The enhanced performance of Co₃O₄/CC electrodes, particularly in terms of overpotential and crystallization behavior, highlights the potential of using CC substrates to improve the efficiency and scalability of water splitting reactions for sustainable hydrogen production.

Controlling the absorption region of multi-shaped silver nanoparticles for SERS applications

2024-03-31T16:41:34+07:00

Introduction: Silver nanoparticles (Ag NPs) are pivotal in advancing surface-enhanced Raman scattering (SERS) due to their exceptional plasmonic properties. Yet, conventional synthesis methods often fail to precisely control their shape and size, impacting SERS efficiency. This study introduces a novel synthesis approach using hydrogen peroxide (H2O2) to tailor Ag NP morphologies, aiming to optimize their plasmonic resonance for improved SERS detection of hazardous substances.

Methods: We utilized a chemical reduction process with H2O2 to etch and shape Ag NPs, adjusting H2O2 concentrations to control nanoparticle morphology. The characterization of the nanoparticles involved SEM, TEM, and XRD for morphology and structure, with UV-Vis spectroscopy determining their absorption spectra.

Results: The approach yielded Ag NPs with variable shapes and absorption wavelengths (330 nm to 740 nm), directly correlating H2O2 concentration with morphological changes. SEM and TEM showed diverse nanoparticle shapes, and XRD confirmed their crystalline structure. Notably, nanoparticles tuned to specific absorption wavelengths significantly enhanced SERS detection of Rhodamine B.

Conclusion: Our method effectively produces multi-shaped Ag NPs with tunable optical properties, enhancing SERS application in detecting trace organic compounds. This streamlined synthesis process offers new possibilities for environmental monitoring and safety assessments.

Biosynthesis of Staphylococcus aureus OS-silver nanoparticles and their antimicrobial and protective effects on coated paper money

2024-04-03T03:58:50+07:00

Introduction: Currency notes harbor and transmit infectious microorganisms if handled without proper care. Hence, in this study, silver nanoparticles biosynthesized from autochthonous S. aureus OS (S-AgNPs) isolated from Nigeria currency notes (Naira) were used to assess the antimicrobial activity of S-AgNPs against the pathogenic money microbiome and to determine their protective effect on coated currency notes.

Methods: Naira notes (15) each, were randomly collected from poultry product sellers, food vendors, fish, sellers, and shopkeepers in Ondo City, Nigeria. A molecular tool was used for the identification of bacterial isolates using 16S ribosomal RNA gene sequences. Staphylococcus aureus-silver nanoparticles (S-AgNps) were characterized by UV‒visible spectroscopy. The antibacterial and antifungal activities of the biosynthesized S-AgNPs against isolated microorganisms were determined using the agar well diffusion method.

Results: A total of one hundred and twenty (120) S-AgNP-coated and non-coated papers were improvised as currency notes and randomly distributed among preinformed business owners. The highest bacterial count of 7.90 cfu/mL was recovered from Naira notes collected from food vendors. The highest fungal count of 4.70 cfu/mL on the Naira note was collected from poultry product sellers. S. aureus had the highest frequency of 29.60%. At 5.0 µg/mL, the S-AgNPs had the greatest inhibitory effects (17.30 mm) on Streptococcus pyogenes and Rhizopus stolonifer. The provided currency notes coated with the biosynthesized S-AgNPs showed no growth of microorganisms. Biosynthesized S-AgNPs showed pronounced antimicrobial potential against pathogenic microorganisms isolated from currency (Naira notes).

Conclusion: AgNPs can be used as coating agents during currency production to minimize the spread of disease-causing pathogenic microorganisms.

The impact of service quality on student retention: The mediating roles of student satisfaction and switching barriers in private universities

2024-03-31T17:00:55+07:00

This research investigated the influence of university service quality, student satisfaction, and switching barriers on student retention within private higher educational institutions situated in Ho Chi Minh City, Vietnam. A total of 410 valid questionnaires were collected for analysis, with hypothesis testing conducted using partial least squares structural equation modeling (PLS-SEM). The findings indicate a positive relationship between service quality within Vietnamese higher education institutions and student satisfaction. Additionally, student satisfaction has a positive association with student retention and switching barriers. Furthermore, switching barriers exhibit a positive relationship with student retention. Mediation analyses revealed that student satisfaction mediates the link between service quality and student retention, while switching barriers mediate the relationship between student satisfaction and retention. These findings contribute to the extant literature by elucidating the dynamics of service quality, student satisfaction, switching barriers, and student retention within higher educational contexts, particularly in the realm of private universities. Notably, this study establishes empirical correlations among service quality, student satisfaction, and student retention. Noteworthy outcomes include revealing the positive impact of service quality on switching barriers and identifying the robust moderating effect of switching barriers on the relationship between student satisfaction and student retention. From a managerial perspective, the constructs and insights derived from this study offer valuable guidance to the management teams of private universities, facilitating a deeper understanding of the pivotal role played by service quality in influencing student satisfaction and retention. Consequently, these insights can inform the strategic direction of private educational institutions in Vietnam.