Tài liệu Hoá học

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Ảnh hưởng của nồng độ chất hỗ trợ tạo keo đến độ ổn định của dung dịch nano bạc sả

Bài viết này công bố về nghiên cứu xác định chất và nồng độ chất hỗ trợ tạo keo trong quá trình chế tạo dung dịch keo nano bạc sả. Bài viết tiến hành nghiên cứu bổ sung các chất hỗ trợ tạo keo với nồng độ khác nhau: PVP (Polyvinylpyrrolidone) và PVA (Polyvinylalcohol 500) với nồng độ thay đổi: 0,15%, 0,3%, 0,45% và 0,6%; Chitosan với nồng độ thay đổi: 0,05%, 0,1%, 0,15% và 0,3% vào dung dịch nano bạc sả.

5/5/2020 12:48:51 AM +00:00

Khả năng điều khiến dị hướng từ theo phương vuông góc trong màng mỏng đa lớp [Co/Pd]

Bài viết tiến hành khảo sát một cách hệ thống sự phụ thuộc của dị hướng từ vuông góc vào các thông số cấu trúc của màng mỏng đa lớp [Co(tCo)/Pd(tPd)]N như số lớp (N), chiều dày của lớp Co (tCo) và chiều dày của lớp Pd (tPd).

5/5/2020 12:21:48 AM +00:00

Tối ưu hóa quá trình chế tạo hạt nano CoxFe3-xO4 sử dụng ma trận Plackett-Burman và phương pháp đáp ứng bề mặt

Bài viết trình bày việc tối ưu hóa các thông số cho quá trình tổng hợp hạt nano CoxFe3-xO4 bằng phương pháp thủy nhiệt sử dụng thiết kế thí nghiệm Plackett-Burman và phương pháp đáp ứng bề mặt (RSM) theo mô hình BoxBehnken.

5/5/2020 12:21:36 AM +00:00

Ảnh hưởng của chất hoạt động bề mặt đến hiệu quả xử lý bụi than

Nghiên cứu này đánh giá hiệu quả của 03 loại chất hoạt động bề mặt: tritonX-100 (non-ion), sodium lauryl sulfate (anion) và cetyl trimetyl amoni bromua (cation) đối với bụi than ở mỏ than Cẩm Phả - Quảng Ninh.

5/5/2020 12:21:30 AM +00:00

Khảo sát thành phần hóa học và xác định hoạt tính kháng khuẩn của tinh dầu cỏ xạ hương

Thành phần hóa học và hoạt tính kháng vi sinh vật của tinh dầu lá Xạ hương (Thymus vulgaris) được khảo sát. Tinh dầu Xạ hương được ly trích thành công bằng phương pháp chưng cất lôi cuốn hơi nước đạt hiệu suất 1,60%. Bằng phương pháp phân tích sắc ký khí ghép khối phổ(GC-MS), thành phần hóa học chính trong tinh dầu lá Trầu không được xác định là hợp chất Thymol với hàm lượng 50,84%.

5/5/2020 12:21:24 AM +00:00

Chất trám polyuretan trên cơ sở cao su polybutadien có hai nhóm hydroxyl đầu cuối mạch

Trong bài viết này, hệ chất trám đặc biệt trên cơ sở cao su butadien có hai nhóm hydroxyl cuối mạch (HTPB)đã được chế tạo thành công. Trong đó, thành phần A (còn gọi là prepolyme), được tổng hợp bằng phản ứng của HTPB với toluendiisoxyanat (TDI) trong môi trường khí trơ ni tơ.

5/5/2020 12:21:16 AM +00:00

Nghiên cứu thăm dò phát hiện dioxin bằng phương pháp Sandwich ELISA

Dioxin là nhóm chất độc hóa học gồm 210 đồng phân, gây ảnh hưởng nghiêm trọng đến sức khỏe con người với các bệnh như ung thư, các bệnh di truyền, dị tật bẩm sinh,... Trong đó, đồng phân 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) được xác định có hệ số độc cao nhất.

5/5/2020 12:21:10 AM +00:00

Application of lactobacillus and streptococcus from yoghurt for kabachnik - Field synthesis of α-aminophosphonates and evaluation of their catalytic activity using molecular docking

A simple, efficient and environmentally process for one pot three component synthesis of α-aminophosphonates by the condensation reaction of diversity of substituted benzaldehyde, amine and triethyl phosphite in the presence of microorganisms and yoghurt as a catalyst at room temperature under solvent free condition is described. The reaction was carried out using bacterial strains viz. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus.

5/5/2020 12:13:28 AM +00:00

Influence of calpain mediated post-mortem ageing on quality of broiler breeder breast fillets during refrigerated holding at (4 ± 1) °C

The aim of this study was to determine the activity of different calpains (µ and m) and calpastatin in broiler breeder breast fillets to understand their influence on ageing during holding at (4±1) °C. Both of the enzymes were extracted and they were subjected to casein zymography analysis.

5/5/2020 12:12:05 AM +00:00

Improvement of the decolorization of azo dye (Direct Red 81) by immobilized cells of bacillus pumilus and free cells of aspergillus clavatus in textile waste waters

In this study, the effluent wastewater samples collected from dyestuff industrial area have been examined for biological treatment. The rate of decolorization was assessed using spectrophotometer at 508 nm and the percentage of decolorization was ascertained. The metabolites of Direct Red 81 (DR81) obtained after biodegradation were determined by HPLC. In order to improve the decolorization process, the effect of process factors like pH, temperature, agitation and dye wastewater concentration on dye decolorization was studied.

5/5/2020 12:10:47 AM +00:00

Screening of antimicrobial spectrum of Brevibacillus sp. isolated from dairy environment

Bacteriocins and Bacteriocin like Inhibitory Substance (BLIS) are ribosomal products exhibiting antimicrobial activity. The present study aimed to screen for production of antimicrobial agents from soil bacteria of dairy environment. Borer was used to dig soil and collected in sterile plastic bags. Isolation was done on tyrosine agar. To exclude non spore formers the soil suspension, was heated at 80ºC.

5/5/2020 12:08:57 AM +00:00

Soil pollution with lead: Geochemistry, food safety issues and reclamation options - A review

Lead (Pb) exposure is estimated to account for 0.6% of the global burden of disease with the highest burden in developing regions. Lead is considered as general protoplasmic poison, which is slow acting, cumulative and subtle. The use of leaded gasoline, discharges from industrial activities and other sources, and deposition by rainfall or dry fall can greatly influence the availability of Pb in soil, water, and other environments. Most of the Pb in plants and soil surface are anthropogenic origin.

5/4/2020 11:54:51 PM +00:00

Synthesis of octahedron Zn2SnO4 by hydrothermal method for high performance ethanol sensor

The octahedron Zn2SnO4 was prepared through a facile hydrothermal method for ethanol gas-sensing application. The synthesized material was characterized by scanning electron microscopy (SEM) and powder x-ray diffraction (XRD). The gas-sensing characteristics were measured at various concentrations of ethanol at temperature ranging from 350 to 450 ºC. The gas response exhibits good linear relationship with increasing ethanol concentrations in the range of 50 -250 ppm. Gas-sensing measurements demonstrated that the synthesized octahedron Zn2SnO4 showed n-type semiconducting behavior, where the sensor resistance decreased upon exposure to ethanol. The findings pointed out that the sensors showed the highest response value at operating temperature of 400 ºC. The sensor response value was 30 at 250 ppm ethanol. Such outstanding gas sensing property might be attributed to the morphology of the octahedra which provided large contact area between Zn2SnO4 and target gas. The synthesized octahedron Zn2SnO4 is potential for detecting traces of ethanol.

5/4/2020 10:36:56 PM +00:00

Synthesis and blend of bio-based benzoxazines from cardanol and diphenolic acid

In this study, two benzoxazine monomers, m-alkylphenyl-3,4-dihydro-2Hbenzoxazine (CA-Bz) and 4,4 Ꞌ -Bis-[6-(3-phenyl-3,4-dihydro-2H-1, 3-benzoxazine)] pentanoic acid (DPA-Bz) were successfully synthesized from fully bio-based phenols (cardanol and diphenolic acid). Their structures were confirmed by FTIR and NMR spectroscopy. CABz/DPA-Bz blend was prepared at weight ratio of 3:1. Polymerization behavior of the blend was investigated by DSC. The ring-opening polymerization temperature of CA-Bz was found to decrease significantly by incorporation of carboxyl groups in DPA-Bz showing thereby the catalytic effect of acid functionality. The modified polybenzoxazine also showed an enhancement of the thermal properties.

5/4/2020 10:36:50 PM +00:00

Study on fluorination and hydrogenation in transparent conducting zinc oxide thin films

Fluorination and hydrogenation are known as two methods for enhancing crystalline structural and electrical properties of ZnO material. The ZnO thin films normally require a low resistivity and a high transmittance for using as high-performance transparent electrodes in optoelectronic applications. In this study, we report successful preparation of fluorinated and hydrogenated ZnO thin films (FZO and HFZO) by using d.c. magnetron sputtering technique. The hydrogenation was carried out by depositing the films in hydrogen plasma atmosphere, while a highly-sintered body of ZnO and ZnF2 compound was employed as a sputtering target for the fluorination.

5/4/2020 10:36:44 PM +00:00

Some characteristics and allopurinol release of carrageenan/ allopurinol films using polyethylene oxide as a dispersion aid agent

This paper presents the effect of carrageenan (CG) on some characteristics and drug release of allopurinol in the presence of polyethylene oxide (PEO) as a dispersion aid agent. The samples were prepared in film shape by solution method, in which, the content of PEO was changed from 1 wt.% to 5 wt.% and the content of allopurinol was fixed at 10 wt.% in comparison with carrageenan weight. Fourier transforms infrared (FTIR) spectroscopy and Field emission scanning electron microscopy (FESEM) methods were used to evaluate interactions and morphology of CG/PEO/allopurinol films. Ultraviolet-visible spectroscopy (UV-Vis) analysis was used to determine drug loading capacity and drug release of CG/PEO/allopurinol films.

5/4/2020 10:36:32 PM +00:00

NO2 gas sensor based on QCM coated with iron oxide nanorods

Iron oxide nanorods were synthesized by chemical co-precipitation method. The structural and morphological characteristics of the as-synthesized nanorods were analyzed by Xray diffraction (XRD) and scanning electron microscopy. The results show that the iron oxide nanorods include the mixture of Fe3O4, γ-Fe2O3 and FeOOH with the diameter and the length of iron oxide nanorods to be 30 and 100 nm, respectively. The iron oxide nanorods were then dispersed and deposited on the gold electrode of quartz crystal microbalance (QCM) for the gas sensor. The iron oxide nanorods based QCM sensor was tested with various concentrations of numerous toxic gases at room temperature, including nitrogen dioxide (NO2), sulfur dioxide (SO2), ammonia (NH3), and carbon monoxide (CO). The testing results indicate that the fabricated sensor exhibits high sensing performance to NO2 gas in the concentration range from 5 to 20 ppm.

5/4/2020 10:36:20 PM +00:00

Mechanical, thermal properties and morphology of composite coating based on acrylic emulsion polymer and graphene oxide

Effects of graphene oxide content on mechanical, thermal properties and morphology of composite coating based on acrylic emulsion R4152 and graphene oxide (GO) have been investigated. Obtained results showed that GO particles had insignificant effect on adhesion of composite coating but GO improved abrasion resistance of composite coatings. The abrasion durability of coatings increased with GO ratio rising to 0.5 % and then abrasion resistance of coatings decreased with GO ratio continuously growing up. SEM images presented that GO particles dispersed homogenously into polymer matrix if the GO ratio is of 0.5 % wt. While the ratio increased to 1 % wt., the agglomeration of GO particles in composite coating could be seen clearly in SEM images. It is assumed that the abrasion resistance decreased if using the GO ratio more than 0.5 % wt. TGA results also demonstrated the thermal property of GO composite coating was improved than that of neat coating.

5/4/2020 10:36:13 PM +00:00

Gas sensor array based on tin oxide nano structure for volatile organic compounds detection

The detection of volatile organic compounds (VOCs) is essential in practical application in breath analysis. Thus, gas sensors based on metal oxide have been fabricated, but they lacked selectivity. One approach to resolve this task is to use an array of highly sensitive and selective sensors as an electronic nose. Here a gas sensor array based on Tin oxide nanostructure with temperature modulation techniques was presented. A Platinum micro-heater is accompanied with the array gas sensor.

5/4/2020 10:36:07 PM +00:00

Far-red emission of CaYAlO4: Mn4+ synthesized by co-precipitation method

Light absorption of the most plants is in range of blue (440 nm), deep-red (660 nm) and far-red around 700-740 nm. The deep-red and far-red light play important roles in reactions of photomorphogenesis of plants. Although red emission phosphors have been researched extensively for white light-emitting diodes, deep-red and far-red emission phosphors for plant growth have been reported inadequately. Thus, in this work, far-red emitting CaYAlO4:Mn4+ phosphor was synthesized by co-precipitation method coupled with various annealing temperature from 800 oC to 1300 oC for 5 h. The crystal structure, morphology, and photoluminescence properties of CaYAlO4:Mn4+ phosphors were investigated in detail. The crystallinity of the phosphor belongs to tetragonal system with space group I4/mmm. Y3+ and Ca2+ ions are coordinated by nine oxygen atoms to form [YO9] and [CaO9] polyhedrons, and the Al3+ ions are coordinated by six oxygen atoms forming [AlO6] octahedrons that provided suitable sites for Mn4+ ions. The obtained sample showed an irregular surface morphology with micro size particles.

5/4/2020 10:36:01 PM +00:00

Effect of 0.5 at.% indium addition on thermoelectric properties of gallium doped-zinc oxide bulk

Thermoelectrics (TE) is well-known as a non-smoke technology for electricity production from waste heat and for greenhouse effect reduction. Enhancing power factor (PF = S 2 , where S is Seebeck coefficient and  is electrical conductivity) and figure of merit of TE materials to achieve high-performance TE devices has attracted much scientific attention. Doping foreign elements into host bulk structure is a basic and traditional solution to modify the thermoelectric properties of materials. In this work, we use small amount of 0.5 at.% In as dopant which is incorporated into Ga-doped ZnO (GZO) bulk by using solid-state reaction method. The effects of In addition on electrical and thermoelectric characteristics of the GZO bulk are discussed in detail.

5/4/2020 10:35:49 PM +00:00

Improvement of colloidal and temperature stability of hsCRP latex reagents with stabilizers

The role of high sensitivity C-reactive protein (hsCRP) level elevation in low-grade systemic inflammation was proved with the confirmation of cardiovascular risk assessment. Hence the measurement of hsCRP has got importance to predict the cardiovascular risk among the suspected population. The current market is still looking for a latex based reagent assay which requires minimum instrument setting and technical expertise to perform the test. Hence we have tried to develop a latex based test for hsCRP. The present study was conducted to test the colloidal and temperature stability of prepared hs-CRP latex reagents with different stabilizers.

5/4/2020 9:20:06 PM +00:00

Comparative efficiency of different organic acids spraying in groundnut on available nutrient status of calcareous soils

A pot culture experiment was conducted in Agricultural College, Bapatla, Andhra Pradesh to study the “comparative efficiency of different organic acids spraying in groundnut on available nutrient status of calcareous soils during kharif season of 2015-16. The experimental soil was Calcareous (collected from Vertisol profile), low in available nitrogen, medium in available phosphorus and high in available potassium.

5/4/2020 9:14:46 PM +00:00

Screening of epiphytic isolates from different crops for plant growth promoting traits

The role of Zn as micronutrient in healthy growth of plants is very important. The microorganisms present in phyllospheric environment have capability to increase micronutrient availability to plants. Total forty eight isolates were obtained from five different crops (wheat, mustard, cotton, pearl millet and moong). All isolates were characterized for different plant growth promoting attributes i.e., production of ammonia, IAA, and solubilization of Zinc, Phosphate. Among all isolates total 87.5 % showed IAA and Ammonia production in different range. Total 72.91 % Zn solubalization and 60.41 % P solubalization showed by isolates respectively. These plant growth promoting attributes are helpful in enhancing crop productivity. So these can be used as bioinoculant or as spray in crops.

5/4/2020 6:34:02 PM +00:00

Inhibitory activity of lactobacillus strains against food-borne pathogens

Since ages various physical and chemical food preservation methods have been to prevent microbial decomposition of food and thus preventing the food-borne illness. Most pathogens have become resistant to conventional methods of preservation and also the chemicals used are detrimental to human health. There is a need for nourishing, fresh and safe foods which can improve the health of consumer. The present research throws light to develop a probiotic based bio-preservative so that the food spoilage can be prevented by not causing various health hazards to the consumers.

5/4/2020 6:27:46 PM +00:00

Isolation, characterization and identification of probiotic lactic acid bacteria (LAB) from honey bees

Laboratory experiments were conducted to explore the diversity of naturally-occurring probiotic lactic acid bacteria (LAB) associated with honey bees and to understand whether they can be used as probiotics to manage honey bee stressors. Honey stomach, honey, bee bread, bee pollen and royal jelly from different species of honey bees (Apis ceranaindica Fabricius, Apis melliefra Linnaeus, Apis florea Fabricius, Apis dorsata Fabricius, Tetragonula iridipennis Smith) were examined for the presence of LAB.

5/4/2020 6:25:04 PM +00:00

Chemical constituent of Cinnamom umtamala: An important tree spices

Cinnamomum tamala (Buch.-Ham.) Nees and Eberm, commonly known as Tejpatta, is a most important tree spices found in Himalayan region. Its leaves used as spices throughout the world since ancient times. The major component of cinnamon oil is eugenol (4-hydroxy-3-methoxyallylbenzene), (β caryophyllene (6.6%), sabinene (4.8%), germacrene D (4.6%) and curcumenol (2.3%).

5/4/2020 6:17:59 PM +00:00

Phân tích dư lượng imidacloprid và azoxystrobin bằng phương pháp sắc ký lỏng: trường hợp nghiên cứu trên cây đinh lăng (Polyscias fruticosa (L.) Harms)

Bài viết nghiên cứu quy trình định lượng bằng phương pháp sắc ký lỏng hiệu năng cao (HPLC) đầu dò UV được thực hiện trên lá Đinh Lăng. Kết quả đạt các yêu cầu về tính phù hợp hệ thống, tính tuyến tính, độ đặc hiệu, độ đúng, giới hạn định lượng và giới hạn phát hiện. Kết quả phân tích cũng cho thấy không còn tồn dư thuốc thử nghiệm trên lá Đinh lăng sau bảy ngày phun thuốc.

5/4/2020 5:09:53 PM +00:00

Nghiên cứu thành phần hóa học của lá cây đinh lăng (Polyscias fruticosa (L.) Harms) trồng tại An Giang

Cây Đinh lăng có tên khoa học là Polyscias fruticosa (L.) Harms, thuộc họ Nhân sâm (Araliaceae), là một cây thuốc quý được sử dụng nhiều để làm thuốc ở Việt Nam và đã được đưa vào Dược điển Việt Nam như là một vị thuốc bổ, tăng lực và sinh thích nghi. Các huyện miền núi thuộc tỉnh An Giang được xem là vùng dược liệu nổi tiếng ở Đồng bằng sông Cửu Long với nhiều loài dược liệu quý trong đó có cây Đinh lăng nhưng chưa có nhiều nghiên cứu sâu về thành phần hóa học trồng tại khu vực này. Vì thế vấn đề này cần thiết được nghiên cứu nhằm phát triển và bảo tồn nguồn dược liệu quý của tỉnh An Giang. Lá cây Đinh lăng trồng tại An Giang được thu mẫu, chiết và tách phân đoạn bằng kỹ thuật chiết ngấm kiệt và chiết lỏng - lỏng, thu được các cao phân đoạn. Các cao phân đoạn được phân lập tiếp tục bằng kỹ thuật sắc ký và được xác định cấu trúc hóa học bằng phổ cộng hưởng từ hạt nhân.

5/4/2020 5:09:41 PM +00:00

Nghiên cứu sản xuất cồn tuyệt đối bằng phương pháp hồi lưu nhiều bậc

Mục tiêu nghiên cứu của đề tài nhằm sản xuất cồn tuyệt đối trong quy mô phòng thí nghiệm, dựa vào tính chất của các cấu tử trong hỗn hợp. Trong nghiên cứu này, việc lựa chọn cấu tử phân ly là CaO đã được thực hiện. Quá trình chưng cất sử dụng một cấu tử phân ly là CaO có hồi lưu nhiều bậc giúp thu nồng độ cồn tuyệt đối đến 99,9% và với hiệu suất 80%.

5/4/2020 5:03:35 PM +00:00