Science and Technology Development Journal - Natural Sciences 2021-10-13T02:36:31+00:00 Phuc Van Pham Open Journal Systems Shoreline fluctuation of Can Gio district in the period 1998 - 2019 2021-09-03T00:29:25+00:00 Duong Pham Thuy Van Tran Thi <p>Facing the current trend of climate change, bank erosion occurs more often in river bank and coastal areas. This problem not only causes loss of land but also damages houses and human lives. Can Gio is a coastal district on the southeast coast of Ho Chi Minh City, an area that has been severely eroded, affecting people's lives and depleting the local economy This paper presents the results of monitoring the shoreline changes in Can Gio district from remote sensing image analysis techniques. The Landsat satellite image was used in combination with a calculation technique based on the water spectrum index to extract the shoreline for the period 1998 - 2019. The results show that, in the whole area, the erosion process dominates with the area of erosion at different stages always being higher than that of accretion; Specifically, within 21 years, the area of erosion occurred 1.8 times more than that of accretion. The landslide area that has accounted for the highest proportion is Thanh An commune with the rate of 29% compared to the area of the whole district. Meanwhile, Long Hoa commune had the largest accretion area with the rate of about 35% compared to the area of the whole district. The research results aim to assist people in coastal monitoring and management to minimize damage to human and ecosystems.</p> 2021-09-03T00:00:00+00:00 ##submission.copyrightStatement## Preparation of LiFePO4/C nanocompostite and study of the effect of electrolyte on the electrochemical performance for Li-Ion rechargeable batteries 2021-09-13T22:25:41+00:00 Phung LE Liem Pham Nhan Thanh Tran Thu Minh Nguyen Man Van Tran <p>In this study, LiFePO4/carbon (LFP/C) nanocomposite was successfully prepared by hydrothermal method in which sucrose was used as carbon precursor. The obtained composite was characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The results showed that this nanocomposite possessed a high-crystallized LFP with a olevin structure and rod-type particles morphology with the size of 100-500 nm. The LFP/C cathode yields showed good capacity of 110 mAh g-1 at 0.1 C as well as high columbic efficiency of 95% in term of using 1.0 M LiPF6 in EC/DMC (1/1). In the case of using an additional 2% VC in the electrolyte system, the specific capacity was 136 mAh g-1 and columbic efficiency was nearly 100%. The superior electrochemical performances can be attributed to the formation of SEI layers on the electrode surface by VC decompostion, leading to suppressed the additional SEI formation from the other solvent, reduced charge-transferred resistance and improving cell capacity as well as long-term capacity retention.</p> 2021-09-13T22:25:39+00:00 ##submission.copyrightStatement## Diversity and distribution of trophic guilds of nematode assemblages in the Ham Luong estuary, Ben Tre province 2021-09-17T22:44:30+00:00 Yen Nguyen Thi My Thai Tran Thanh Lam Nguyen Le Que Lam Luu Pham Thanh Yen Tran Thi Hoang Quang Xuan Ngo <p>Studying the trophic guild of nematode assemblages contribute to infer their foods, therefor interprete the aquatic foodwebs and assess the environmental quality of ecosystem. Nematode communities play important roles in the aquatic foodweb, as the decomposers break down the detritus or as the intermediate chains in transferring of material and energy from decompsers as bacteria and producers as microalgae to higher consumers. The present study aimed to analyse the diversity and distribution of nematode trophic groups at six subtidal sations of the Ham Luong estuary in Ben Tre province in the dry season 2017. The results found four groups of feeding guild including swallowers, tear &amp; swallowers, chewers, and suction-feeders. Two groups of swallowers and tear &amp; swallowers were dominant, accounting for high proportions in the assemblage. While swallowers higly distributed in the upstream, tear &amp; swallowers was high abundant in the downstream, chewers mostly presented in the middle part of the estuary. Nevertheless, suction-feeders was scarce distribution in the upstream side. The indices of trophic diversity were in average values, and less variation along the course of the estuary. The differences in the distribution of nematode trophic guilds might be resuted by the heterogeneities in the benthic environment, which need to be investigated in the next studies.</p> 2021-09-17T22:44:28+00:00 ##submission.copyrightStatement## The Friedel-Crafts sulfonylation catalyzed by chloroaluminate ionic liquids 2021-09-18T07:55:40+00:00 Xuan Thi Thi Luu Huynh Nhung Thi Ngo Ngoc Lan Thi Nguyen <p>Friedel-Crafts sulfonylation is one of the most common methods to prepare sulfone. With the development of Green Chemistry, chemical processes have been improved towards being environmentally friendly by using of organic solvents in the limit, using recoverable catalysts, reducing energy ... are getting more attention. Therefore, in this study, several types of ionic liquids such as [Bmim]BF4, [Bmim]PF6, [Bpy]Cl2AlCl3, [Pyrro]I2AlCl3, [Mth]I2AlCl3, [Bmim]Cl2AlCl3 which catalysed for the Friedel-Crafts sulfonylation of toluene and benzenesulfonyl chloride have been investigated. Besides, most factors which have influenced on the reaction yield such as the temperature, the reaction time, the amount of catalyst have been studied. The reaction was carried out under solvent-free and mild conditions; moreover, the catalyst was able to be recovered and reused without significant loss of its activity. The main product phenyl p-tolyl sulfone was easily isolated after the reaction and obtained in high yield 97% after four-hour heating at 100 oC by using Nbutylpyridinium chloroaluminate, [Bpy]Cl2AlCl3, as catalyst. Microwave irradiation has been used to improve many organic syntheses as a green and efficient activation method in order to reduce reaction times and save energy. Compared to the conventional heating, phenyl p-tolyl sulfone was synthesized with the excellent yield in the short reaction time under the microwave assistance.</p> 2021-09-18T07:53:13+00:00 ##submission.copyrightStatement## Chemical constituents of Ngoc Linh ginseng leaves (Panax vietnamensis Ha et Grushv.) 2021-09-18T08:05:02+00:00 Khang Hoang Le Duyen Thi Chu Khang Thanh Mai Huy Quoc Nguyen Tung Thanh Phan Long Hoang Ngo Chung Thanh Nguyen Luan Cong Tran Quang Ton That <p>Ngoc Linh ginseng or Vietnamese ginseng (Panax vietnamensis Ha et Grushv.) of the Araliaceae family, a endemic plant in Ngoc Linh mountain, is the 20th type of ginseng found in the world (1985). The content of saponin of Ngoc Linh ginseng is much higher than that of other ginsengs in the world such as Panax ginseng (Korean ginseng), anax quinquefolium(American ginseng) and anax notoginseng (Chinese ginseng). Until now, from roots, rhizomes and leaves of Ngoc Linh ginseng, there are 63 saponin which were isolated and determined structures. In addition, polyacetylenes, polyphenols, fatty alcohols and amino acids were also reported. Some of them showed diverse biological activities. In this research, from Ngoc Linh ginseng leaves, six compounds were isolated and structural elucidated by 1D and 2D NMR, MS spectroscopic methods and comparison of the spectral data with those in literature. They were one triterpene, squalene (<strong>1</strong>), one quinone terpenoid, a-tocopherolquinone (<strong>2</strong>), two fatty alcohols, tetradecanol (<strong>3</strong>), docosanol (<strong>4</strong>) from the -hexane extract and a steroid glycoside, daucosterol (<strong>5</strong>) and one flavonoid, kaempferol (<strong>6</strong>) from the methanol extract. All six compounds were reported for the first time from Ngoc Linh ginseng leaves.</p> 2021-09-18T08:05:02+00:00 ##submission.copyrightStatement## Study on the morphological and physiological changes of the peltate glandular trichome development in holy basil (Ocimum sanctum L.) leaf 2021-09-24T06:39:32+00:00 Anh Xuan Phan Huong Thanh Tran Viet Trang Bui <p>The essential oil is a main product of Holy basil (Ocimum sanctum L.). It present mainly in the peltate glandular trichomes. Therefore, the morphological and physiological changes during the development of peltate glandular trichomes are of great interest. In this paper, the morphological changes of glandular trichomes, the relationship between glandular trichomes and leaf development, and the physiological changes during leaf development of Holy basil were analyzed. The Holy basil peltate glandular trichomes were formed at the early stage of leaf development (leaf primordia) and continuously renewed during leaf development. The development of peltate glandular trichomes of Holy basil included four main stages: initiation, shaping, secretory cavity formation and essential oils accumulation. The formation of peltate glandular trichomes started at the beginning of leaf rapid growth while the accumulation of essential oils occurred at the slow mature growth and strongly increased at the stationary growth phase. The intensity of photosynthesis and respiration of leaves increased strongly during the period of rapid growth. The activities of auxins and cytokinins in leaf were very high at the beginning of the rapid growth stage while gibberellin activity was high only at the end of the rapid growth stage. Treatment with 1 mg/L gibberellic acid increased the length of branch, area of leaf, and the content of the essential oil.</p> 2021-09-24T06:39:31+00:00 ##submission.copyrightStatement## Magnetic recoverable CuFe2O4/cellulose nanocrystal composite as an efficient catalyst for 4-nitrophenol reduction 2021-09-24T06:49:33+00:00 An Nang Vu Ngoc Hoa Thi Le Ngoc Han Nguyen Bao Tran Huynh Hieu Van Le <p>CuFe2O4/cellulose nanocrystal (CuFe2O4/CNC) composite featured high magnetic activity was prepared by a facile and one-pot solvothermal method. Based on the solvothermal condition, nanometer-sized magnetic CuFe2O4 ferrite particles (CuFe2O4 NPs) were directly synthesized and CNC was coated on the surfaces of CuFe2O4 NPs. The composition, structure, morphology, and magnetic property of prepared CuFe2O4/CNC material were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible spectroscopy (UV-Vis), and vibrating-sample magnetometer (VSM). FESEM and EDX mapping results showed that CuFe2O4 NPs had a uniform size of 88 nm and were immobilized on the CNC. The catalytic activity of CuFe2O4/CNC was tested in the catalytic reduction of 4-nitrophenol in aqueous solution. After immersion treatment by NaBH4, the CuFe2O4/CNC composite exhibited high catalytic efficiency in reducing 4-nitrophenol to 4-aminophenol. The 4-nitrophenol could be fully reduced in less than 5 minutes. The high catalytic activity was attributed to the easy accessibility of the 4-NP ions by CNC and CuFe2O4 active sites. Owing to its environmental sustainability and being recoverable by magnetic force, CuFe2O4/CNC is suggested to be a promising catalyst with potential applications in wastewater treatment.</p> 2021-09-24T06:49:32+00:00 ##submission.copyrightStatement## Evaluating the impact of additives and lithium salts on the performance of spinel cathode material LiMn2O4 2021-10-10T22:01:18+00:00 Bảo Ngọc Thị Nguyễn Thanh Tuyền Thị Trương Nhật Ni Trương Nguyễn Hoang Van Nguyen Mẫn Văn Trần Phụng Mỹ Loan Lê <p>LiMn2O4 spinel structure was considered as the cathode material to replace LiCoO2 for high voltage lithium-ion batteries, however, its main drawback was poor cycling due to dissolution of manganese and structural instability. One of the effective solutions is to find out a suitable electrolyte composition and additive to reduce the manganese dissolution and to prevent the side reaction between the electrode material and the electrolyte. In this study, we investigated the impact of using fluoroethylene carbonate (FEC), vinyl carbonate (VC), lithium bis(oxalato)borate (LiBOB) as additives for the electrolyte of 1 M LiPF6/EC:DMC (1:1) and different salt such as: LiBF4, LiClO4 and LiTFSI for commercial carbonate solvent of EC:DMC (1:1) on the improvement of the cyclic stability and electrochemical performance of LiMn2O4 electrodes. The results showed that the addition of FEC did not affect the initial capacity but increased significantly the cycle stability of the material. In particular, the discharge capacity maintained 91% of initial value after 20 cycles in the electrolytes containing 2 %wt and 3 %wt FEC, respectively. However, further increase of FEC content induced the polarization of the charge discharge curves as well as the increase of the electrode - electrolyte interface resistance which were responsible for the cycling performance decline. Among tested salts, LiClO4 was the best electrolytic one for EC:DMC (1:1) based-electrolyte that enhanced the initial discharge capacity roughly 20 mAh/g. In addition, preliminary results on the full-cell of graphite||LMO achieved the discharge capacity of 87.09 mAh/g (at C/5) and 73.52 mAh/g (at C/2) which is about 66.99 % the initial discharge capacity obtained at C/5 of the half-cell LMO|Li).</p> 2021-10-10T22:01:14+00:00 ##submission.copyrightStatement## Hydrothermal preparation of Ag/Fe3O4/Cellulose nanocrystals nanocomposite and its application in methylene blue removal 2021-10-10T22:23:10+00:00 An Nang Vu Tan Huy Le Nguyen Kim Phung Thi Tu Ngoc Uyen Thai Nguyen Thanh Van Thi Tran Van Hieu Le <p>The preparation of reusable and eco-friendly materials from renewable biomass resources such as cellulose is an inevitable choice for the sustainable development. In this paper, Ag/Fe3O4/cellulose nanocrystals (CNC) nanocomposite was prepared and investigated its application in methylene blue (MB) removal. In the procedure, CNC was isolated from Vietnamese coconut husk fibers (CCH) biomass via a formic/peroxyformic acid process treatment and hydrochloric acid hydrolysis. The obtained CNC was used as a starting material to prepare Ag/Fe3O4 nanostructure by facile and green hydrothermal method. The nanocomposite was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and magnetic properties via vibrating sample magnetometer (VSM) analysis. The results showed that Ag/Fe3O4 was formed with a particle structure and dispersed on the CNC surface. All samples exhibited magnetic properties and the saturation magnetization (Ms) of Ag/Fe3O4 composite was reduced from 48 to 12 emu/g with adding CNC. Ag/Fe3O4/CNC magnetic nanocomposite demonstrated good adsorption of MB solution and exhibited a fast catalytic reduction of MB after immersion treatment by NaBH4, which showed potential applications in water treatment.</p> 2021-10-10T22:23:10+00:00 ##submission.copyrightStatement## Tổng hợp vật liệu Fe3O4@SnO2 và NaxFeFe(CN)6 ứng dụng làm điện cực anode và cathode trong pin Na-ion hoàn chỉnh 2021-10-13T02:36:31+00:00 Nguyen Tuan Loi Phung Viet Duc Thieu Quang Quoc Viet Nguyen Anh Tien <p>Trong nghiên cứu này, vật liệu anode chứa các hạt nano Fe<sub>3</sub>O<sub>4</sub> và SnO<sub>2</sub> được tổng hợp bằng phương pháp thay thế điện hóa. Vật liệu cathode Na<sub>x</sub>FeFe(CN)<sub>6</sub> chứa các khối lập phương ở kích thước micromet được tạo thành bằng phương pháp axit hóa. Khi được ứng dụng làm điện cực anode và cathode trong các bán pin Na-ion, cả hai vật liệu đều thể hiện sự ổn định cao của dung lượng phóng/sạc với hiệu suất Coulombic gần 100%. Hơn thế nữa, pin Na-ion hoàn chỉnh được tạo thành bởi sự kết hợp của anode Fe<sub>3</sub>O<sub>4</sub>@SnO<sub>2</sub> và cathode Na<sub>x</sub>FeFe(CN)<sub>6 </sub>đã cho thấy những đặc tính điện hóa tuyệt vời như: hiệu điện thế làm việc đạt 2.4 V, hiệu suất Coulombic cao, dung lượng phóng/sạc ổn định, và mật độ năng lượng đạt 120 Wh/kg. Những kết quả nghiên cứu cho thấy rằng, pin Na-ion hoàn chỉnh (Fe<sub>3</sub>O<sub>4</sub>@SnO<sub>2</sub> || Na<sub>x</sub>FeFe(CN)<sub>6</sub>) có nhiều tiềm năng cho các ứng dụng trong thực tế.</p> 2021-10-13T02:36:31+00:00 ##submission.copyrightStatement##