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2023

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Articles 1531 - 1547 of 1547

Full-Text Articles in Chemistry

Chitosan Blending With Water-Soluble Polymers As Dissolving Microneedles For Controlled Drug Release, Fuad Abdullah Farhan Saleh Jan 2023

Chitosan Blending With Water-Soluble Polymers As Dissolving Microneedles For Controlled Drug Release, Fuad Abdullah Farhan Saleh

Chulalongkorn University Theses and Dissertations (Chula ETD)

Chitosan has gained significant interest due to its ability to film-forming, biodegradability, and biocompatibility, making it suitable for topical and transdermal drug delivery such as fabricating microneedles. In this study, chitosan microneedles were prepared by incorporating polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) in three different ratios (1:1, 2:1, and 3:1 chitosan: polymers) to control drug release. The microneedles were fabricated using a molding method, their mechanical properties were tested using the universal testing machine (UTM), and their skin penetration ability was tested using pig skin (ex vivo). The results indicated that the microneedles exhibited sufficient strength to penetrate the outer …

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Design Of Block Copolymer With Tunable Hydrophobic/Hydrophilic/Fluorophilic Interactions, Tatiane De Fatima Dutra Jan 2023

Design Of Block Copolymer With Tunable Hydrophobic/Hydrophilic/Fluorophilic Interactions, Tatiane De Fatima Dutra

Theses, Dissertations and Culminating Projects

Block copolymers (BCP) with balanced interactions and their resultant bulk-phase self-assembly have become increasingly important in advancing nanotechnology, separation, and energy applications. However, a few reports have addressed the synthesis challenge and bulk-phase self-assembly of such triblock copolymers. This thesis presents a facile route for preparing triblock copolymer via controlled radical and organocatalytic ring-opening polymerization that allows precise control over the incorporation of individual moieties in resultant polymer, responsible for balanced hydrophilic, hydrophobic/lipophilic, and fluorophilic interactions. Synthesized polymer with suggested self-assembled 2D lamellar nanostructure exhibits high-temperature stability. The long-term goal of this work is to selectively use this polymer class …

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A Computational Study Of The Copper-Catalyzed Trifluoromethylation Of Boronic Acids, Kevin Nyhuis Jan 2023

A Computational Study Of The Copper-Catalyzed Trifluoromethylation Of Boronic Acids, Kevin Nyhuis

Theses, Dissertations and Culminating Projects

This work is a computational study of a reaction mechanism for the trifluoromethylation of boronic acids. Three steps of the proposed reaction mechanism are studied, •CF3 addition to a copper catalyst center, base promoted transmetalation between copper and aryl boronic acid, and bond forming reductive elimination in which the CF3 and aryl substituent form a bond. Limited information is known about this mechanism. This study uses computational methods to attempt to elucidate the mechanism and provide the groundwork for potential improvement. Quantum chemical methods in conjunction with tight-binding based conformational sampling methods are used to investigate the possible …

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Investigating The Roles Of Active Site Residues K59, K119 And E168 In M. Tuberculosis Indole-3-Glycerol Phosphate Synthase, Maryum M. Bhatti Jan 2023

Investigating The Roles Of Active Site Residues K59, K119 And E168 In M. Tuberculosis Indole-3-Glycerol Phosphate Synthase, Maryum M. Bhatti

Theses, Dissertations and Culminating Projects

Tuberculosis (TB) is a disease that is caused by a bacteria called Mycobacterium tuberculosis and primarily attacks the lungs but can spread to other areas of the body as well. TB can develop resistance to drugs that may be used to cure the disease. Multidrug resistant TB is especially a growing issue as it does not respond to the two most powerful anti-TB drugs, isoniazid and rifampicin. For this reason, finding new ways to target TB are critically needed. One possible way to do this is to target the enzymes in the tryptophan biosynthetic pathway of M. tuberculosis. Studies have …

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2-Aminopyridyl Functionalized Scaffold As A Tool For Systematic Investigation Of B-Glucan Binding And Dectin-1 Activation, Jasper Alinea Aquino Jan 2023

2-Aminopyridyl Functionalized Scaffold As A Tool For Systematic Investigation Of B-Glucan Binding And Dectin-1 Activation, Jasper Alinea Aquino

Graduate Student Theses, Dissertations, & Professional Papers

Tuberculosis (TB) – an infectious disease caused by Mycobacterium tuberculosis (Mtb) – remains an epidemic worldwide contributing to millions of deaths each year. Vaccination is possibly the best means of addressing this global threat. In recent years, synergistic Th1 and Th17 immune responses have emerged as the key players for a vaccine-induced protection against TB. There is currently no vaccine approved for humans that elicits a Th17-mediated immune response. C-Type Lectin Receptors (CLR), specifically Dectin-1, a pattern recognition receptor (PRR) of β-1,3-glucans (β-glucans) primarily from fungi cell walls, is known to induce a Th17-mediated response. The Th17 response upon binding …

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Development Of Electrochemical Biosensor For Detection Of Thyroid–Stimulating Hormone, Kittirat Kitticharoenwiwat Jan 2023

Development Of Electrochemical Biosensor For Detection Of Thyroid–Stimulating Hormone, Kittirat Kitticharoenwiwat

Chulalongkorn University Theses and Dissertations (Chula ETD)

This dissertation focused on the development of electrochemical paper-based immunosensor for determining thyroid-stimulating hormone (TSH) using a label-free immunoassay. Thyroid-stimulating hormone is a pituitary hormone that stimulates the thyroid gland to produce thyroid hormones for the body’s metabolism. The current electrochemiluminescence method for determining TSH as a specific biomarker indicating congenital hypothyroidism (CHT) onset is unfortunately restricted to laboratory settings, thereby resulting in limited practical utilization, delayed diagnosis, and severe outcomes. Herein, we proposed a simple, rapid, portable, and sensitive electrochemical biosensor with a label-free format based on bovine serum albumin (BSA)/graphene oxide (GO) nanocomposite for TSH determination. Caboxylated GO …

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Bamboo Biochar For Bar Adsorptive Microextraction Of Parabens In Water, Maytinee Jantorn Jan 2023

Bamboo Biochar For Bar Adsorptive Microextraction Of Parabens In Water, Maytinee Jantorn

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this research, bamboo biochar bar was prepared in the form of small-sized rods using starch as a binder and applied as a sorbent in bar adsorptive microextraction (BAµE) of parabens (methyl paraben, ethyl paraben, propyl paraben and butyl paraben) in water. The mixture of bamboo biochar which has a size of 60-80 mesh, a surface area of 102.6 m²g-1 and a pore size of 0.7 nm and starch in a weight ratio of 1:13 gave the good mechanical stability and high removal efficiency of parabens. When applied the bamboo biochar bar as a sorbent, the optimum conditions for BAµE …

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Selective Photodegradation Of Food Contaminants Using Titania-Silica-Iron Oxide Nanocomposites With Molecularly Imprinted Technology, Mehak Un Nisa Jan 2023

Selective Photodegradation Of Food Contaminants Using Titania-Silica-Iron Oxide Nanocomposites With Molecularly Imprinted Technology, Mehak Un Nisa

Chulalongkorn University Theses and Dissertations (Chula ETD)

In this study, magnetic imprinted photocatalysts (Fe3O4@SiO2@TiO2@MIP and Fe3O4@SiO2@MIP@TiO2) have been synthesized successfully by surface molecular imprinting technique. 5,7-dimethoxy-coumarin was used as a dummy template to give specific recognition ability to AFB1. A range of analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM), and Branauer-Emmett-Teller (BET) were employed to study the crystal structure, morphology, and chemical composition of the nanocomposites. The HPLC-DAD was used to quantify the photodegradation efficiency of imprinted photocatalysts under different factors such as the source of irradiation light, initial concentration of analyte, amount of photocatalyst, and …

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Polyaniline/Cellulose Nanofiber/Polyvinyl Alcohol Hydrogel-Modified Screen-Printed Graphene Electrode For Cd2+ And Ni2+ Detection, Pichapon Boonkrong Jan 2023

Polyaniline/Cellulose Nanofiber/Polyvinyl Alcohol Hydrogel-Modified Screen-Printed Graphene Electrode For Cd2+ And Ni2+ Detection, Pichapon Boonkrong

Chulalongkorn University Theses and Dissertations (Chula ETD)

Heavy metal contamination in wastewater has been an environmental issue, so the determination of heavy metals by an accurate and simple method is important. In this work, polyaniline/cellulose nanofiber/polyvinyl alcohol hydrogel-modified screen-printed graphene electrode (PANI/CNF/PVA hydrogel-modified SPGE) was fabricated by combining the advantages of graphene and conductive hydrogel to increase the conductivity and preconcentrate the metal ions to fabricate the modified electrode for the simultaneous detection of Cd2+ and Ni2+. First, PANI/CNF nanocomposite was synthesized by in situ chemical polymerization, and CNF was shown to prevented PANI aggregation and provided sufficient porous structure on the modified electrode. The PANI/CNF nanocomposite …

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The Future Of Alternative Energy? Simulating Methyl Stearate Pyrolysis Via Molecular Dynamic Processes, Sarah J. Adeoye Jan 2023

The Future Of Alternative Energy? Simulating Methyl Stearate Pyrolysis Via Molecular Dynamic Processes, Sarah J. Adeoye

Graduate Theses/Dissertations

The process of extracting and refining crude oil is both expensive and environmentally hazardous. The synthesis of biodiesel sourced from vegetable oils is a renewable process and less hazardous to the environment. Therefore, we seek to understand the pyrolysis procedure at an atomic level in hopes of optimizing future fuel viability. Herein, I analyze methyl stearate (a component of biodiesel) using an in-house database of ab initio trajectories, each simulating 1.0 ps (with 1.0 fs resolution). These jobs were observed for significant bond-breaking/forming events, the type of fragments produced, and the exact position and time for each event. Statistical analysis …

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Renewable Fuels: Molecular Dynamics Investigations Into Pyrolysis Of Methyl Linoleate, Elson Osakpolor Eguaosa Jan 2023

Renewable Fuels: Molecular Dynamics Investigations Into Pyrolysis Of Methyl Linoleate, Elson Osakpolor Eguaosa

Graduate Theses/Dissertations

With the rapid depletion of the world’s supply of fossil fuels, especially petroleum products, petroleum prices have risen by approximately 800% between the 1970s and now and are projected to continue rising. It is also expected that the world’s consumption of energy will increase commensurate with its growing population. Although biodiesel is a good renewable alternative, it has its limitations including high production costs and poor low-temperature performance. We seek to improve conventional biodiesel with pyrolysis to produce low molecular-weight compounds with high energy densities. Understanding the pyrolysis path on the atomic scale is key as it will allow us …

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Exploration And Synthesis Of Half-Heusler And Disordered Ternary Intermetallic Single Crystals, Md Fahel Bin Noor Jan 2023

Exploration And Synthesis Of Half-Heusler And Disordered Ternary Intermetallic Single Crystals, Md Fahel Bin Noor

Graduate Theses/Dissertations

Due to their distinct physical and chemical characteristics, half-Heusler compounds are intermetallic materials that have undergone substantial research. The general formula for these compounds is XYZ, where X and Y are transition metals and Z is a p-block element. Thermoelectricity is among the half-Heusler compounds' most exciting potential uses, but additional possible applications include spintronics, magnetic refrigeration, and superconductivity, among others. Recently, half-Heuslers (and Heuslers) have emerged as candidates for catalysts for hydrogenation. The CoNbSn half-Heusler compound, as well as another unique intermetallic ternary compound, the disordered Mn4-xCrxAl11, were successfully grown as single crystals …

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Carbon-Based Polymer Composite For Electrochemical Sensing Of Creatinine Sodium Potassium And Calcium Ions, Kanyapat Teekayupak Jan 2023

Carbon-Based Polymer Composite For Electrochemical Sensing Of Creatinine Sodium Potassium And Calcium Ions, Kanyapat Teekayupak

Chulalongkorn University Theses and Dissertations (Chula ETD)

Electrochemical sensors have emerged as indispensable tools for various applications including environmental monitoring, food safety, and biomedical diagnostics owing to their simplicity, sensitivity, and fast response. However, traditional methods for electrode fabrication are often associated with drawbacks such as cleanroom requirements, multi-step processes involving toxic materials, high waste consumption, and high costs. To address the limitations, this dissertation evaluates the utilization of 3D printing, laser engraving, and inkjet printing technologies for the fabrication of electrochemical sensors based on carbon-based polymer composites. In the first part, a 3D-printed electrochemical sensor based on a copper oxide nanoparticle-ionic liquid/reduced graphene oxide (CuO-IL/rGO) modified …

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Methyl Isobutyrate Production Via Hydrogenation Of Methyl Methacrylate Derived From Pyrolysis Of Acrylic Plastic Waste, Ramzi Nasser Ahmed Saif Jan 2023

Methyl Isobutyrate Production Via Hydrogenation Of Methyl Methacrylate Derived From Pyrolysis Of Acrylic Plastic Waste, Ramzi Nasser Ahmed Saif

Chulalongkorn University Theses and Dissertations (Chula ETD)

According to zero waste and upcycling policy, this work aims to utilize waste polymethyl methacrylate (PMMA) to methyl isobutyrate (MIB) via hydrogenation over nickel (Ni) based catalysts supported on commercial zeolites: HY, H-Beta-27 (SiO2/Al2O3 = 27 by mole), H-Beta-40 (SiO2/Al2O3 = 40 by mole) and H-ZSM-5. The appropriate catalyst support was first screen by using MMA monomer as the substrate for hydrogenation. Under 30 bar initial H2 pressure (PH2) at 250 °C for 3 h, Ni/H-Beta-27 catalyst effectively promoted hydrogenation to achieve 85% MMA conversion with 56.2 wt% MIB yield because of its larger external surface area and pore size. …

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The Design And Characterization Of Gold Nanoclusters As Elementary Building Blocks, Heather Gaebler Jan 2023

The Design And Characterization Of Gold Nanoclusters As Elementary Building Blocks, Heather Gaebler

Theses and Dissertations (Comprehensive)

Gold nanoclusters with diameters in the quantum size regime (< ~2 nm) are promising building blocks for the design of novel nanomaterials as they exhibit unique size-dependent properties that can be altered and fine-tuned. The research outlined in this PhD thesis employs density functional theory to construct and analyze small ligand-protected cage and rod-shaped nanoclusters. Chapter 2 reports stable halide-protected gold nanocages that were engineered to have a closed-shell valence electron count of 18. This study finds that nanocages comprised of 19 and 20 gold atoms can be converted into stable magic number species containing 18 valence electrons by modifying their charged states via adsorption of halide ligands to the cage’s surface. Chapter 3 reports stable ligand-protected gold nanoclusters with a tetrahedral Au4 core that were engineered to have a closed-shell valence electron count of 2. This study investigates the structural and electronic effects of halide and alkoxy ligands on the tetrahedral nanocluster and concludes that the results support the broader conclusion that it’s possible to fine-tune the stability and electronic properties of small gold nanoclusters using appropriate ligands. Chapter 4 reports stable gold nanorods that have diameters in the quantum regime that were constructed from elementary building blocks that contain “halide-staples”. This study presents different orientations of the “halide-staple” motifs on …

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การขจัดสีย้อมอินทรีย์ด้วยการดูดซับบนเมโซพอรัสซิลิกาโหลดด้วยโลหะ, อภิญญา ศิริพร Jan 2023

การขจัดสีย้อมอินทรีย์ด้วยการดูดซับบนเมโซพอรัสซิลิกาโหลดด้วยโลหะ, อภิญญา ศิริพร

Chulalongkorn University Theses and Dissertations (Chula ETD)

ความนิยมที่มากขึ้นในการใช้งานสีย้อมอินทรีย์ในอุตสาหกรรมสิ่งทอ จึงทำให้เกิดความกังวลเป็นอย่างมากเนื่องจากสีย้อมอินทรีย์เป็นอันตรายและก่อให้เกิดมลพิษทางน้ำ ความเป็นพิษของสีย้อมเหล่านี้ส่งผลเสียต่อระบบนิเวศ สีย้อมเหล่านี้มีความเสถียรมากเนื่องจากสีย้อมเหล่านี้ได้จากการสังเคราะห์และมีโครงสร้างโมเลกุลที่ซับซ้อน ดังนั้นงานวิจัยนี้จึงศึกษาการกำจัดสีย้อมที่ปนเปื้อนในน้ำโดยการดูดซับด้วยตัวดูดซับเมโซพอรัสซิลิกาและตัวดูดซับเมโซพอรัสซิลิกาที่โหลดด้วยโลหะ ตัวดูดซับเมโซพอรัสซิลิกาจะเตรียมโดยใช้วิธีแม่แบบชนิดอ่อน สีย้อมอินทรีย์ที่เลือกใช้ ได้แก่ สีย้อมเอซิดบลูซึ่งเป็นสีย้อมที่มีประจุลบ และสีย้อมเมทิลีนบลูซึ่งเป็นสีย้อมที่มีประจุบวก โดยมีการศึกษาผลของปัจจัยต่าง ๆ ที่มีต่อการดูดซับซึ่งจะรายงานผลในเทอมของร้อยละการกำจัดสีย้อม ลักษณะเฉพาะของตัวดูดซับสังเคราะห์จะวิเคราะห์ด้วยด้วยเทคนิคการเลี้ยวเบนของรังสีเอกซ์ การดูดซับการคายซับด้วยก๊าซไนโตรเจน เทคนิคฟูเรียร์ทรานส์ฟอร์มอินฟราเรดสเปกโตรสโคปี และ ผลรวมของประจุบนพื้นผิวตัวดูดซับเท่ากับศูนย์ จากผลการทดลองพบว่า ตัวดูดซับ 15Zn/MS600nc สามารถกำจัดสีย้อมเอซิดบลูได้ร้อยละ 100 เมื่อใช้ความเข้มข้นเริ่มต้นของสีย้อมเอซิดบลู 300 มิลลิกรัมต่อลิตร ความเป็นกรดด่างเท่ากับ 7 และปริมาณตัวดูดซับ 0.1 กรัม ภายในเวลา 15 นาที ตัวดูดซับ 15Zn/MS600c แสดงร้อยละการกำจัดสีย้อมสีเมทิลีนบลูที่ร้อยละ 94 เมื่อใช้ความเข้มข้นเริ่มต้นของสีย้อมเมทิลีนบลู 100 มิลลิกรัมต่อลิตร ความเป็นกรดด่างเท่ากับ 11 และปริมาณตัวดูดซับ 0.1 กรัม ภายในเวลา 15 นาที จากการศึกษาแบบจำลองจลนพลศาสตร์การดูดซับ พบว่า การดูดซับบนตัวดูดซับ 15Zn/MS600nc มีความสอดคล้องกับแบบจำลองของอาฟ์รามี โดยมีค่าสัมประสิทธิ์สหสัมพัทธ์เท่ากับ 0.9995 ในขณะที่ตัวดูดซับ 15Zn/MS600c เมื่อพิจารณาจากค่าสัมประสิทธิ์สหสัมพัทธ์ซึ่งมีค่าเท่ากับ 0.9695 จะมีความสอดคล้องกับแบบจำลองปฏิกิริยาอันดับสองเทียม

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Optical Phase Transition Characteristics In Germanium-Antimony-Selenium-Tellurium And Graphene Oxide Thin Film For Application In Photonics Memory., Gan Soon Xin Jan 2023

Optical Phase Transition Characteristics In Germanium-Antimony-Selenium-Tellurium And Graphene Oxide Thin Film For Application In Photonics Memory., Gan Soon Xin

Student Works (2020-2029)

This thesis aims to study the phase change characteristic of Ge2Sb2Se4Te1 (GSST) using 1550 nm pulsed laser as excitation source, and to explore its potential in multilevel nonvolatile photonic memory application. Firstly, the amorphous to crystalline state phase transition of GSST using 1550 nm pulsed laser as optical excitation source is investigated. The threshold laser pulse duration to achieve crystallization are 190 ns, 140 ns, 100 ns and 70 ns for laser intensities of 0.46 GW/cm2, 0.61 GW/cm2, 0.76 GW/cm2 and 0.85 GW/cm2, respectively. However, it is found that the phase change tolerance of GSST is very stringent (phase transition …

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