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Articles 7891 - 7920 of 33209

Full-Text Articles in Chemistry

Α-Glucosidase Inhibitors From The Stems Of Thunbergia Laurifolia, Khoa Nguyen Anh Jan 2021

Α-Glucosidase Inhibitors From The Stems Of Thunbergia Laurifolia, Khoa Nguyen Anh

Chulalongkorn University Theses and Dissertations (Chula ETD)

Alpha-glucosidase inhibitory assay-guided isolation of Thunbergia laurifolia L. stems yielded a new compound named 5-acetoxyfuranonapthoquinone (1) along with nineteen known compounds (2-20). The structure of the isolated compounds was elucidated by the analysis of multiple spectroscopic data as well as by comparison with the previous reports. The isolated compounds were evaluated for α-glucosidase inhibition. Syringaresinol (6), rosmarinic acid (11), 1,2,8-trihydroxyxanthone (17), and isojacareubin (18) showed the most potent inhibitory activity among isolated compounds. Kinetic study indicated that syringaresinol (6), 1,2,8-trihydroxyxanthone (17), and isojacareubin (18) could inhibit the maltase and sucrase function by non-competitive, and rosmarinic acid (11) was identified as …

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Isolation Of Α-Glucosidase Inhibitors And Cytotoxic Compounds From Heartwood Of Mansonia Gagei Drumm, Le Thi Thu Huong Jan 2021

Isolation Of Α-Glucosidase Inhibitors And Cytotoxic Compounds From Heartwood Of Mansonia Gagei Drumm, Le Thi Thu Huong

Chulalongkorn University Theses and Dissertations (Chula ETD)

Phytochemical and biological investigations were carried out on the heartwoods of M. gagei. Twelve known compounds (1–11, 29), ten new sesquiterpenoids (12–21), seven novel compounds (22–28) and one new neolignan (30) were isolated. Their structures were elucidated by spectroscopic data analysis (UV-Vis, FTIR, 1D, 2D NMR and HRESIMS), and their absolute configurations were established by calculation of ECD data. Isolated compounds were evaluated for antioxidant, cytotoxic activity and enzyme inhibitory activity against α-glucosidase. Interestingly, mansonialactam (21) showed significant inhibitory activity against α-glucosidase from the yeast with the IC50 value of 0.2 ± 0.05 mM which was 468 times lower than …

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Development Of Copper Complexes Containing Quinoline Derivatives As Photoredox Catalysts For Atra Reactions, Pawittra Chaibuth Jan 2021

Development Of Copper Complexes Containing Quinoline Derivatives As Photoredox Catalysts For Atra Reactions, Pawittra Chaibuth

Chulalongkorn University Theses and Dissertations (Chula ETD)

The photocatalytic for C-C and C-S bond formations by ATRA reaction is an attractive topic in green organic synthesis. In the first part of this dissertation, a series of aminoquinoline-methylpyridine conjugates (1Q, 2Q, and 3Q) was synthesized, characterized, and used as a ligand for complexing Cu(II) ion. The ligand containing one aminoquinoline unit and two methylpyridine (1Q), gave the complex with the highest catalytic activity for haloalkylation of alkenes. The reaction proceeds well with high chemo- regio- and stereoselectivity for over 20 examples of alkenes. The mechanistic study is consistent with the visible-light-induced homolysis (VLIH) of Cu(II)-X bond to Cu(I) …

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Colorimetric Sensors For Formaldehyde Detection And Electrochemiluminescent For Pathogens Detection, Uma Pongkitdachoti Jan 2021

Colorimetric Sensors For Formaldehyde Detection And Electrochemiluminescent For Pathogens Detection, Uma Pongkitdachoti

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this work, two methods for the detection of formaldehyde and one assay for detection of Cryptosporidium parvum DNA (C. parvum) in water samples were developed. For the detection of formaldehyde, silver-doped hydroxyapatite (Ag-HAP) was used to extract formaldehyde from high volume samples and the Tollens’ reaction occurred on the solid surface. After the reaction, silver nanoparticles were produced on the material resulting in the material color change from off-white to yellow or brown depending on the concentration of formaldehyde. By using the Ag-HAP, the detection of formaldehyde was achieved by measuring the color intensity. Under the optimized conditions, this …

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Nanocellulose-Chitosan-Metal Organic Framework Composites For Arsenic Removal, Yatika Paisart Jan 2021

Nanocellulose-Chitosan-Metal Organic Framework Composites For Arsenic Removal, Yatika Paisart

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this work, a new composite sponge of chitosan, nanocellulose, and MIL-53(Fe) metal-organic-framework were synthesized and applied for As(III) and As(V) removal. Nanocellulose with an average size of 433.5 ± 41.0 nm were prepared and used. The octahedron crystalline MIL-53(Fe) was successfully synthesized. The nanocellulose was mixed with chitosan and MIL-53(Fe) before crosslinking and freeze-drying. The obtained materials were characterized by Fourier transform infrared spectroscopy, nitrogen adsorption, scanning electron microscope, and energy dispersive x-ray spectroscopy. The results showed that the composite sponge was successfully fabricated with a suitable weight ratio of 2CS: 1NC: 1.5MIL-53(Fe). The CS-NC-MIL-53(Fe) composite exhibited a highly …

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การประกอบตัวด้วยตนเองและการตอบสนองโดยการเปลี่ยนสีของวัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/โลหะออกไซด์ โดยวิธีการผสมในรูปแบบสารละลาย, จิดาภา แสงวารินทร์ Jan 2021

การประกอบตัวด้วยตนเองและการตอบสนองโดยการเปลี่ยนสีของวัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/โลหะออกไซด์ โดยวิธีการผสมในรูปแบบสารละลาย, จิดาภา แสงวารินทร์

Chulalongkorn University Theses and Dissertations (Chula ETD)

งานวิจัยนี้ศึกษาการประกอบตัวของวัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/โลหะออกไซด์ และพฤติกรรมการตอบสนองโดยการเปลี่ยนสีต่อสิ่งกระตุ้นภายนอก โดยทำการสังเคราะห์โลหะออกไซด์ได้แก่ ซิลิกาจากวิธีโซล-เจล และซิงก์ออกไซด์จากวิธีโซลโวเทอร์มอล และนำมาเตรียมเป็นวัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/โลหะออกไซด์ โดยใช้ 10,12 pentacosadiynoic acid (PCDA) เป็นมอนอเมอร์ ด้วยวิธีการผสมในรูปแบบสารละลาย จากนั้นทดสอบสมบัติการตอบสนองโดยการเปลี่ยนสีต่ออุณหภูมิ และกรด-เบสของวัสดุเชิงประกอบที่เตรียมได้ เนื่องจากโซล-เจลซิลิกา มีลักษณะเป็นทรงกลม ขนาดเล็ก และมีขนาดสม่ำเสมอ ทำให้วัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/ซิงก์ไอออน/โซล-เจลซิลิกา มีปริมาณผลิตภัณฑ์ที่สูงกว่าการเตรียมโดยใช้ผงซิลิกาที่ได้มีการศึกษามาก่อน และมีความไวในการตอบสนองโดยการเปลี่ยนสีต่อกรด-เบสที่สูงกว่า นอกจากนี้พบว่า วัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/ซิงก์ไอออน/โซล-เจลซิลิกา สามารถเกิดการเปลี่ยนสีแบบผันกลับได้เมื่อทำการเพิ่ม-ลดอุณหภูมิ สำหรับวัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/ซิงก์ไอออน/ซิงก์ออกไซด์ เตรียมจากซิงก์ออกไซด์ที่สังเคราะห์ให้มีขนาดและรูปร่างของซิงก์ออกไซด์ที่แตกต่างกัน ได้แก่ ทรงกลม รูปแท่ง และรูปร่างไม่สม่ำเสมอ โดยขนาดและรูปร่างของอนุภาคซิงก์ออกไซด์ส่งผลต่อการประกอบและจัดเรียงตัวของสายโซ่พอลิเมอร์ วัสดุเชิงประกอบระดับนาโนเมตรที่เตรียมจากซิงก์ออกไซด์ทรงกลมและรูปแท่งที่มีขนาดระดับนาโนเมตร เกิดการประกอบตัวได้เหมาะสม สามารถเกิดพอลิเมอไรเซชันได้ดี จึงได้ปริมาณผลิตภัณฑ์ที่สูงกว่าการใช้ซิงก์ออกไซด์รูปร่างไม่สม่ำเสมอและมีขนาดใหญ่ระดับไมโครเมตร วัสดุเชิงประกอบระดับนาโนเมตรพอลิไดแอเซทิลีน/ซิงก์ไอออน/ซิงก์ออกไซด์ ทั้งหมดเกิดการเปลี่ยนสีแบบผันกลับได้ต่ออุณหภูมิ และแสดงการตอบสนองโดยการเปลี่ยนสีต่อกรดและเบส

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Carbon Dioxide Hydrogenation To Methane Over Silica Supported Nickel Catalysts In A Differential Reactor And Kinetic Model Development, Angkana Khuenpetch Jan 2021

Carbon Dioxide Hydrogenation To Methane Over Silica Supported Nickel Catalysts In A Differential Reactor And Kinetic Model Development, Angkana Khuenpetch

Chulalongkorn University Theses and Dissertations (Chula ETD)

Development of a kinetic model for CO2 methanation over a commercial nickel catalyst was performed to consider pathways of CO2 conversion via Sabatier and RWGS reactions. H2/CO2 ratio in the feed gas composition was varied at the stoichiometry of the Sabatier reaction assuming a fictitious CO2 conversion of 0 to 0.7. Non-stochiometric gas feeding and the addition of product gases, i.e., methane and steam, were also considered to examine reaction orders and inhibition effects. The kinetic tests were carried out at 300–350 °C and 0.1–0.9 MPa. GHSV corresponded to 37,494 h-1. The stable activity was achieved by forcibly stressing the …

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Mesoporous Carbon/Silica Nanocomposites With Acid And Base Properties For Glucose Conversion Into Value Added Chemicals, Satit Yousatit Jan 2021

Mesoporous Carbon/Silica Nanocomposites With Acid And Base Properties For Glucose Conversion Into Value Added Chemicals, Satit Yousatit

Chulalongkorn University Theses and Dissertations (Chula ETD)

The purpose of this study is to prepare mesoporous carbon/silica (MCS) nanocomposites using natural rubber (NR) as a renewable carbon source. A series of mesoporous nanocomposites based on NR and hexagonal mesoporous silica (HMS), prepared via an in situ sol-gel process, were used as precursors, which were then converted into the MCS materials by carbonization. The sulfonic acid-functionalized mesoporous carbon/silica (MCS-SO3H) was prepared by direct sulfonation with H2SO4 solution. The silica surface of MCS-SO3H were then grafted by 3-aminopropyltrimethoxysilane to produce the acid–base catalysts (MCS-SO3H-NH2) and used as the solid catalysts in glucose conversion. The MCS nanocomposites exhibited enhanced structural, …

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Synthesis And Catalytic Activity Of Layered Double Hydroxide And Metal Sulfide Nanoparticle Composites, Ajirawadee Suwanchan Jan 2021

Synthesis And Catalytic Activity Of Layered Double Hydroxide And Metal Sulfide Nanoparticle Composites, Ajirawadee Suwanchan

Chulalongkorn University Theses and Dissertations (Chula ETD)

Degradation of methylene blue dye was investigated over heterogenous catalytic process using layered double hydroxide and metal sulfide nanoparticle composites. CuCo2S4/NiFe LDH nanocomposites were synthesized using hydrothermal method, and the composites were characterized by SEM and XRD techniques. CuCo2S4 and NiFe LDH were formed with an average particle in the range of 350-450 nm and 2200-3500 nm, respectively. The composites were loaded at 1.8, 3.4, 5.2 and 9.9 wt% of CuCo2S4. CuCo2S4, NiFe LDH and CuCo2S4/NiFe LDH composites were tested at the same condition for methylene blue degradation. The 18CuCo2S4/NiFe LDH composites provided higher catalytic degradation of methylene blue compared …

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Synthesis Of Baicalein Derivatives As Anti-Dengue Agents, Apinya Patigo Jan 2021

Synthesis Of Baicalein Derivatives As Anti-Dengue Agents, Apinya Patigo

Chulalongkorn University Theses and Dissertations (Chula ETD)

Dengue, a mosquito-borne viral disease, is now considered a major international health concern, and hence the development of a new anti-dengue drug is highly desirable. Baicalein is a flavone isolated from the roots of Scutellaria baicalensis and Scutellaria lateriflora. Baicalein derivatives have been shown previously to exhibit a promising anti-dengue activity. In this study, five novel and thirteen known baicalein derivatives were synthesized via semi synthesis from baicalein with modifications at C-5, -6, -7, and -8 positions on ring A and a six-step total synthesis with modifications at the para position on the ring B with a range of electron-withdrawing …

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Cellulose-Supported Fluorophore As Metal Ion Sensors, Apiwat Promchat Jan 2021

Cellulose-Supported Fluorophore As Metal Ion Sensors, Apiwat Promchat

Chulalongkorn University Theses and Dissertations (Chula ETD)

Organic fluorescent ligands are attractive for qualitative and quantitative analysis of metal ions. Cellulose substrates, especially for filter paper, have been demonstrated as one of the most economical and easy to use platform for fluorescent sensors applied in on-site analysis with naked-eye observation. In this work, new series of amidoquinoline derivatives were synthesized and investigated as the fluorescent ligands for developing paper-based sensors. The sensors are used for convenient analysis either by simple naked-eye observation or an image processing software. In the first part of this dissertation, parallel solid-state synthesis on filter paper macroarray was used for rapid discovery and …

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Use Of Modified Nay Zeolite As Ionophore For Perchlorate Selective Electrode, Boonyakorn Srisassawatkul Jan 2021

Use Of Modified Nay Zeolite As Ionophore For Perchlorate Selective Electrode, Boonyakorn Srisassawatkul

Chulalongkorn University Theses and Dissertations (Chula ETD)

NaY zeolite is well deserved for being employed as a catalyst, adsorbent, and ion exchanger. Therefore, its ion exchange property is used in ion selective electrodes (ISEs). Commercial NaY zeolite was modified with cetyltrimethylammonium bromide (CTAB) in various concentrations (100, 150, and 200 mM), denoted them as 100, 150 and 200 SMZ, respectively. XRD, FT-IR, SEM and TGA/DTG showed good agreement of CTAB adsorption on zeolite surface. Then SMZ is used to fabricate polymeric membrane with polyvinyl chloride (PVC) plasticized with o-nitrophenyl octyl ether (o-NPOE). The best performance of ISE was exhibited at the membrane composition of 200 SMZ: PVC: …

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Chemical Constituents Of Fan-Si Abutilon Indicum Stems, Arum Restu Widyasti Jan 2021

Chemical Constituents Of Fan-Si Abutilon Indicum Stems, Arum Restu Widyasti

Chulalongkorn University Theses and Dissertations (Chula ETD)

This study aimed to isolate secondary metabolites from the stems of Abutilon indicum and to evaluate their α-glucosidase, pancreatic lipase, α-chymotrypsin inhibitory activity. Chromatographic fractionation of the n-hexane crude extracts led to the isolation of three known metabolite (1-3). The crude extract from all parts of the plant were evaluated for inhibitory activity on the alpha-glucosidase enzyme. The DCM-soluble roots were active with 10.2% at 25 μg/mL. The hexane and MeOH-soluble stems were active with 11.0% at 25 μg/mL and 8.0% at 0.25 μg/mL. The hexane, DCM, and MeOH-soluble leaves are active with 20.2% at 0.025 μg/mL; 20.0% at 0.025 …

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Modification Of Screen-Printed Carbon Electrode For Detection Of Pesticides, Kansuda Langor Jan 2021

Modification Of Screen-Printed Carbon Electrode For Detection Of Pesticides, Kansuda Langor

Chulalongkorn University Theses and Dissertations (Chula ETD)

Methyl parathion (MP) is an organophosphate pesticide broadly used in agriculture to protect crops and fruits from the damages caused by insects and pests. However, when it is used in large quantities, it can be potentially toxic to humans and animals, causing many poisoning effects. Moreover, its residues can also penetrate the food chain (via agriculture food products) as well as contaminating the environment, leading to air, water and soil pollution. Therefore, rapid determination and reliable quantification of trace level of MP are crucially needed for food safety and environmental monitoring. In this work, a low-cost and portable electrochemical sensor …

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Colorimetric And Fluorescent Detection Of Nucleic Acid By Styryl Dyes, Kotchakorn Supabowornsathit Jan 2021

Colorimetric And Fluorescent Detection Of Nucleic Acid By Styryl Dyes, Kotchakorn Supabowornsathit

Chulalongkorn University Theses and Dissertations (Chula ETD)

Nucleic acid staining dyes are essential tools for the analysis and visualizing of DNA/RNA in vitro and in cellular applications. Although there are several commercially available dyes developed during the past few decades, the selection is still relatively limited, and they are often very costly and associated with undesirable characteristics such as toxicity. Consequently, the discovery of nontoxic, readily available dyes, with desirable and controllable optical characteristics remains important. Styryl dyes have recently gained popularity as potential biological staining agents with many desirable properties including a straightforward synthesis procedure, excellent photostability, tunable optical properties, and high responsiveness towards nucleic acid …

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Hydrogen Gas Sensing And Storage Properties Of Doped And Non-Doped Beryllium Oxide Nanotubes, Kritsanaphas Sawing Jan 2021

Hydrogen Gas Sensing And Storage Properties Of Doped And Non-Doped Beryllium Oxide Nanotubes, Kritsanaphas Sawing

Chulalongkorn University Theses and Dissertations (Chula ETD)

The electronic properties of armchair (5,5) beryllium oxide nanotube (BeONT), zigzag (10,0) BeONT, and their surfaces doped by the selected elements of periods 2 (B, C and N), 3 (Mg, Al, Si, P and S) and 4 (Ca, Ga, Ge, As and Se), and their hydrogen molecule adsorptions were studied using periodic DFT‒D method. The C(O)‒ and Ge(O)‒(5,5) BeONTs, C(O)‒, Si(O)‒ and Ge(O)‒(10,0) BeONTs were suggested to be new hydrogen molecule sensing materials based on the electrical resistivity measurement. The C(O)‒, Si(O)‒ and Ge(O)‒doped (5,5) BeONTs, and C(O)‒ and Si(O)‒doped (10,0) BeONTs were suggested to be utilized as hydrogen storage …

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Synthesis Of Quantum Dot-Based Fluorescent Sensors For Detection Of Anionic Metabolites And Copper (Ii) Ion, Nattakarn Phromsiri Jan 2021

Synthesis Of Quantum Dot-Based Fluorescent Sensors For Detection Of Anionic Metabolites And Copper (Ii) Ion, Nattakarn Phromsiri

Chulalongkorn University Theses and Dissertations (Chula ETD)

Oxalate, citrate, and urate are the anionic metabolites that are the products of the metabolism pathway of living organisms. The high level of these anionic metabolites is related to the diseases. For example, the excess amount of oxalate ions in urine indicates the risk of kidney stones, while the level of citrate can suggest the risk of cancer. The level of urate in urine is related to the risk of gout. The detection of these anionic metabolites is significant and still remains a challenge. Thus, this work aims to develop the more sensitive and selective fluorescence sensing of oxalate in …

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Boron Nanomaterials And Small Molecules Adsorption, Nontawat Ploysongsri Jan 2021

Boron Nanomaterials And Small Molecules Adsorption, Nontawat Ploysongsri

Chulalongkorn University Theses and Dissertations (Chula ETD)

The adsorption abilities of hydrogen boride nanotubes and nanosheet were studied. The adsorption of H2, H2O, NH3 and CH4 on the most stable armchair and zigzag hydrogen boride nanotubes and their C, N and O decorated nanotubes were investigated by using density functional tight binding (DFTB) method. The results show that C-decorated armchair and zigzag HBNTs could be the NH3 storage materials and N-decorated armchair and zigzag HBNTs could be water vapor sensing materials. The adsorption of Li, Na and K atoms on armchair like (5,5) and zigzag like (10,0) HBNTs and hydrogen adsorption on Li, Na and K decorated …

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Pna-Immobilized Paper For Detection Of Pcr Amplicons, Nuttapon Jirakittiwut Jan 2021

Pna-Immobilized Paper For Detection Of Pcr Amplicons, Nuttapon Jirakittiwut

Chulalongkorn University Theses and Dissertations (Chula ETD)

DNA detection is very important in diverse fields leading to a continuous increase in the research and development of various DNA sensors. This study focuses on the development of a paper-based DNA sensor by using pyrrolidinyl PNA as a recognition probe. The PNA-immobilized DNA sensor was designed to contain several PNA probes in the same device as a self-check system to increase the accuracy and facilitate the data collection and interpretation. The PNA-immobilized paper was then utilized for the detection of the DNA target, followed by the visualization of the captured target DNA via an enzyme-catalyzed colorimetric reaction. In this …

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Development Of Retention Index Based Simulation For Validation Of Compound Identification In Gc×Gc, Palathip Kakanopas Jan 2021

Development Of Retention Index Based Simulation For Validation Of Compound Identification In Gc×Gc, Palathip Kakanopas

Chulalongkorn University Theses and Dissertations (Chula ETD)

Comprehensive two-dimensional gas chromatography (GC×GC) is a high-performance technique for separation, identification and quantification of volatiles and semi-volatiles in complex multi-component samples such as biomolecular molecules, essential oil, foods, and petroleum. One of the most popular detectors used for peak identification with GC×GC is mass spectrometer (MS) allowing identification of separated peaks based on comparison with mass spectral library. However, only MS library comparison shows low confidence in compound identifications due to the fact that compounds with similar structures (especially for isomers) often have similar mass spectra. Apart from sample preparation, a great challenge is to effectively select types of …

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Synthesis And Application Of Polymeric Micelles Assembled From Pentafluorophenyl Ester-Containing Amphiphilic Block Copolymers, Panittha Damsongsang Jan 2021

Synthesis And Application Of Polymeric Micelles Assembled From Pentafluorophenyl Ester-Containing Amphiphilic Block Copolymers, Panittha Damsongsang

Chulalongkorn University Theses and Dissertations (Chula ETD)

Functionalizable pentafluorophenyl ester (PFP)-based polymer precursors, namely poly(pentafluorophenyl acrylate) (PPFPA) and poly(pentafluorophenyl metharylate) (PPFPMA), and zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) are the two polymers having extremely different solubility. It is therefore almost impossible to synthesize their block copolymers in a controlled manner by the conventional approach. Herein, we demonstrated, for the first time, that the synthesis and in situ formation of nanoassemblies of their diblock copolymer can be done via polymerization-induced self-assembly (PISA) using reversible addition-fragmentation chain-transfer (RAFT) dispersion polymerization. PMPC was synthesized as the first block and further employed as a macro chain transfer agent (PMPC Macro-CTA) for the synthesis …

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Thin-Layer Chromatography For Determination Of Phenolic Compound Profile And Antioxidant Activity Of Thai Honey, Pattraporn Chobpradit Jan 2021

Thin-Layer Chromatography For Determination Of Phenolic Compound Profile And Antioxidant Activity Of Thai Honey, Pattraporn Chobpradit

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this study, a small-scale method using thin-layer chromatography (TLC) was developed to determine profile and antioxidant activity value of Thai honey samples obtained from different flora sources. Prior to TLC analysis, the samples were prepared by solvent extraction with dichloromethane. Using 2, 2-diphenyl-1-picrylhydrazy radical (DPPH•) reacted with the samples extract prior to TLC spot and color detection with imageJ, half-maximal inhibitory concentration (IC50) values of seven honey samples was obtained in a range of 9 to 22 mg/mL in comparison with IC50 values of 0.13 mg/mL for L-ascorbic acid (LA), along with limit of detection (LOD) and limit of …

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Theoretical Study Of Ethylene Polymerization By Phenoxy-Imine Catalyst, Pavee Apilardmongkol Jan 2021

Theoretical Study Of Ethylene Polymerization By Phenoxy-Imine Catalyst, Pavee Apilardmongkol

Chulalongkorn University Theses and Dissertations (Chula ETD)

Reaction mechanisms of ethylene polymerization catalyzed by the phenoxy-imine (FI) and the nickel phenoxyphosphine polyethylene glycol (Ni-PEG) with alkali metals were explored using DFT calculations. For FI catalysts, the effect of group IVB transition metals substitutions was investigated. The trend of calculated activation energies (Ea) at the rate-determining step is Zr < Hf < Ti and is in good agreement with experiments. The effect of ligands of the Ti-FI-based catalysts when changing the parent nitrogen (O, N) to oxygen (O, O), phosphorus (O, P), and sulfur (O, S) ligands on activity was also monitored. The results indicated that the sulfur (O, S) ligand gives the lowest activation energy. Additionally, the reactivity of Ni-phenoxy-imine (Ni-FI)-based catalysts for polyethylene polymerization was studied. Our calculations suggested that the square planar complex of Ni-FI is more reactive than its C2 symmetric octahedral complex. For Ni-PEG(M) catalysts, the trend for activation energies of four Ni-PEG(M) systems is Li < Na < K < Cs, which corresponds to experimentally observed activities. Moreover, the roles of secondary metals in Ni-PEG catalysts in terms of steric, electronic, and electrostatic effects were elucidated. The DFT results suggested that the active catalyst should have strong cooperative metal-metal/metal-ligand interactions and less positive charge on the secondary metal. Finally, to gain insight into the design of the novel Ni-PEG catalysts with alkali-earth metals, the effect of catalyst structure on experimental activity was investigated. This work provides fundamental understandings of the reaction mechanisms for the FI and Ni-PEG(M) catalysts, which could be used for the design and development of catalysts for ethylene polymerization.

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Discrimination Of Weedy Rice By Using Near-Infrared Spectroscopy Combined With Chemometrics, Sureerat Makmuang Jan 2021

Discrimination Of Weedy Rice By Using Near-Infrared Spectroscopy Combined With Chemometrics, Sureerat Makmuang

Chulalongkorn University Theses and Dissertations (Chula ETD)

Weedy rice is one of the most notorious weeds occurring in rice-growing areas, especially in South-East Asia. Weedy rice especially in form of paddy seed is difficult to manage and separate as they provide common features (morphological resemblance) to cultivated rice. This work presents a modification of self-organizing map (SOMs) for the classification of weedy rice from cultivated rice via in situ direct sample analysis from paddy seed using near-infrared (NIR) spectroscopy and hyperspectral NIR camera. The sample pretreatment was carried out by a cyclone vacuum machine to remove the contaminated particles and other impurities. The physical characteristics and the …

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Lamellar Inorganic Solids And Biochar Nanocomposites For Sorptive Removal Of Metal Ions And Nitrophenol, Sutasinee Sutthiklub Jan 2021

Lamellar Inorganic Solids And Biochar Nanocomposites For Sorptive Removal Of Metal Ions And Nitrophenol, Sutasinee Sutthiklub

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this research, the adsorbents of ternary-component composites were developed to remove various types of toxic chemicals. The selected three components are clay, MgAl-layered double hydroxide (MgAl-LDH) and biochar because they are nontoxic and low cost and also possess high adsorption capacity and high surface area. The composites were synthesized by the combination of post-pyrolysis and co-precipitation methods, and characterized by XRD and SEM-EDS. The result shows that clay and LDH particles distributed and deposited on the biochar matrix, confirming the coexistence of three phases in micrometer and nanometer scales. Ni2+, CrO42- and 4-Nitrophenol were chosen as the representatives of …

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Program Development For Synthesis Plan Design Of Organic Compounds By Using Artificial Intelligence, Tawatchai Jitporn Jan 2021

Program Development For Synthesis Plan Design Of Organic Compounds By Using Artificial Intelligence, Tawatchai Jitporn

Chulalongkorn University Theses and Dissertations (Chula ETD)

Computer-Assisted Synthesis Planning (CASP) is a computational tool for facilitating organic chemists to design and synthesis organic compounds by calculating the best possible synthesis pathways. Most CASP tools are commercial or closed-source software and thus, they cannot be modified to improve performance or update database. Therefore, it is our aim to develop an open-source CASP tool. Library of reaction rules that was created from the US patent database was taken from literature and was then reclassified to improve its applicability. This modified library was then used for training neural network and 2 important models were obtained for the search engine. …

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Flow-Through Reactor For Photomediated Synthesis Of Silver Nanoprisms, Thanasit Laisanguanngam Jan 2021

Flow-Through Reactor For Photomediated Synthesis Of Silver Nanoprisms, Thanasit Laisanguanngam

Chulalongkorn University Theses and Dissertations (Chula ETD)

Silver nanoprisms (AgNPrs) have been widely used due to their outstanding optical properties which is one of an important phenomenon that depends on their size, shape, and compositions with characteristic localized surface plasmon resonance (LSPR). The changes in LSPR of AgNPrs can be simply observed by the color changes of the AgNPrs colloidal solution, therefore, the AgNPrs have been mostly used as chemical sensors as they provide high sensitivity and capable to be functionalized to improve the detection selectivity. In this study, we report a photochemical technique to induce the shape conversion of the spherical silver nanoparticle to AgNPrs by …

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Development Of Colorimetric Paper-Based Analytical Device For Cortisol Detection, Thanathip Kosawatphat Jan 2021

Development Of Colorimetric Paper-Based Analytical Device For Cortisol Detection, Thanathip Kosawatphat

Chulalongkorn University Theses and Dissertations (Chula ETD)

Nowadays, the detection of cortisol can play a key role in understanding stress-related diseases. Several competitive immunoassay formats have been reported for the detection of this small hormone molecule. Lateral flow immunoassay (LFIA) is one of the most widely used platforms that offer its simplicity and rapidity for such analysis. Unlike previous sensors for cortisol sensing that require complicated readers, specialized reagents, or even post-treatment methods to amplify the obtained signal, in this work, we employed a concave test zone constructed on the LFIA device (cLFIA) which can directly enhance the signal response as the flowing sample was substantially concentrated …

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Application Of Oxygen Scavenger In Gel Electromembrane Extraction For Determination Of Nitrite And Nitrate, Thidarat Samkumpim Jan 2021

Application Of Oxygen Scavenger In Gel Electromembrane Extraction For Determination Of Nitrite And Nitrate, Thidarat Samkumpim

Chulalongkorn University Theses and Dissertations (Chula ETD)

Gel electromembrane microextraction (G-EME) have been proven as a promising extraction method due to its effectiveness for extraction and preconcentration of charged analytes and its compliance with the principle of green chemistry. G-EME consists of two phases (donor and acceptor phases), separated by a gel membrane made of agarose. The driving force is the electrical potential applied across the membrane. Despite of all the advantages, the common problem was the oxygen generated in the acceptor solution due to the electrolysis of water that could affect the analysis of easily oxidized analyte species such as nitrite/nitrate species. In this work, application …

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Production Of Bio-Olefins From Oleic Acidvia Oxidative Dehydrogenation Using Vanadium Oxides/Sba-15 Catalysts, Nattaporn Chaidherasuwet Jan 2021

Production Of Bio-Olefins From Oleic Acidvia Oxidative Dehydrogenation Using Vanadium Oxides/Sba-15 Catalysts, Nattaporn Chaidherasuwet

Chulalongkorn University Theses and Dissertations (Chula ETD)

Long-chain olefins (≥C10) are important commodity chemicals, which are primarily used to manufacture everyday products such as plastic packaging, surfactants and detergents in cleaning products, and lubricant oil additives. However, the long-chain olefins are currently synthesized from the petroleum refining process via ethylene oligomerization or thermal cracking of long-chain paraffins. To support the Bio-Circular-Green Economy (BCG) model, the direct synthesis of olefins from renewable feedstocks has become an attractive route to promote overall sustainability. The objective of this research was to study the possibility to transform oleic acid (OA), one of the unsaturated fatty acids in palm oil, to produce …

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