32 research outputs found
Functional organic thin films under extreme confinement
No full text"Confining materials can produce dramatic changes in their fundamental properties. As evident from graphene and other 2D materials, reducing film thickness of materials to a few layers of even monolayers can alter their optical, electronic and magnetic properties compared to bulk counterparts. One of the tenets of current materials research is to harvest these unique properties of thin film materials at ""extreme confinement"", i.e., at condition when the film thickness reduces below a critical value where one or more structural aspects such as molecular packing, orientation, conformation, as well as properties begin to deviate from bulk. So far, significant advancements have been made in extremely confined materials where individual entities are held together by strong covalent bonds, such as most inorganic materials. However, such studies on organic molecules are lacking. This is partly because of fabrication challenges that arise as the bonds that hold entities in the supramolecular structure of organic molecules are significantly weaker. My thesis aims to crystallize extremely confined thin films of two functional materials, active pharmaceutical ingredients (APIs) and conjugated polymers, and then to explore and elucidate the resulting variations in structure and properties compared to thicker films.
Low aqueous solubility of APIs is one of the most significant impediments in pharmaceutical industry. Nanosizing has been recognized as an effective to address this challenge. My approach to nanosize poorly soluble APIs is to solidify them in to nanothin films by utilizing meniscus-guided solution-coating (MGC) technique. In my first study (Chapter 2), we demonstrated a control in film thickness of APIs in nanometer scale range (1.5 μm to 30 nm) as well as their morphology and molecular packing by varying simple processing parameters. Moreover, we also performed sequential deposition of multiple components in a layer-by-layer manner by utilizing the same approach. Interestingly, we also observed trapping and stabilization of metastable polymorphs of API when coated under highly non-equilibrium conditions. In my following study (Chapter 3), I aimed to elucidate the role of nanoconfinement in the observed phenomenon as well as to investigate its role on dissolution properties of APIs. Here, I observed abrupt order-to-disorder transition and stabilization of semi-crystalline and amorphous forms of three different APIs when the film thickness was decreased below a critical value of ~25-30 nm in all three APIs. I also developed a dissolution model that predicted an enhancement in solubility and intrinsic dissolution rate (IDR) upon decrease in film thickness. The experimental results closely matched this model and we demonstrated a drastic increase in IDR upon decreasing the thickness and increasing disorder in the films.
Next, I explored into two-dimensionalization of conjugated polymers- a novel class of semiconducting materials that have enabled fabrication of inexpensive, transparent, flexible electronics. Monolayer films of conjugated polymers are gaining an increasing attention because of their potential in tuning optoelectronic properties compared to bulk films, application in fabrication of ultrasensitive sensors, and as a near-ideal platform for studying fundamental charge transport mechanisms. However, fabrication of 2D films with high coverage and high degree of order remains challenging, and fundamental questions on how multiscale morphology and electronic properties of these films change when confined to monolayer films remain unanswered. In my work (Chapter 4), I first utilized dynamic-template-directed MGC technique to fabricate highly ordered and aligned 2D monolayer films of conjugated polymers of ~3.5 nm thickness with 100% coverage, which contrasted with disordered monolayers produced on solid substrates. Furthermore, I observed that the polymer chains in monolayers on dynamic template were highly twisted and their backbone planarity increased monotonically until the film thickness was increased to a critical value of ~20-30 nm. This led to a decrease in interfacial trap state density and an increase in hole mobility of the polymer films by almost 3 orders of magnitude when film thickness was increased from monolayer to the critical thickness. In addition, I fabricated OFET-based sensors incorporating ultrathin films of polymers which showed sensitivity of ~83% to ammonia vapors of ~1ppb concentration. Next, I explored into graphene surfaces as a template for monolayer films of polymers (Chapter 5) and observed significant enhancement in multiscale morphology with higher fiber density, coverage, degree of crystallinity, alignment and polymer backbone planarity compared to those on control silicon substrates. This accompanied with p-doping of the polymer by the graphene substrates. OFET devices incorporating graphene nanoflakes in ultrathin films of polymer blends showed enhancement in hole mobility by ~2 orders of magnitude compared to pristine polymer films. We attributed this to a decrease in interfacial trap state density and change in morphology, resulting due to the interaction between graphene and the polymer.
Overall, my thesis has demonstrated strategies to overcome the challenges associated with fabricating extremely confined thin films of organic materials and reported deviations in structure and properties of such films with respect to the bulk. The insights gained from these studies will be helpful in harvesting enhanced properties of extremely confined thin films of pharmaceuticals and organic electronics, and will hopefully inspire exploration into confinement effects of other organic materials."Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2023-08-01The student, Prapti Kafle, accepted the attached license on 2021-06-23 at 16:14.The student, Prapti Kafle, submitted this Dissertation for approval on 2021-06-23 at 16:43.This Dissertation was approved for publication on 2021-06-25 at 15:41.DSpace SAF Submission Ingestion Package generated from Vireo submission #16710 on 2022-01-12 at 13:03:33Made available in DSpace on 2022-01-12T22:51:40Z (GMT). No. of bitstreams: 7
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Previous issue date: 2021-06-25Embargo set by: Seth Robbins for item 121183
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Fireflies of the rainforest: Illuminating the mysterious world of crystal polymorphism
No full textPolymorphism or the ability of molecules to pack in multiple crystal structures, is one of the most important parameters in pharmaceutical industries as it highly influences the physicochemical properties of drugs such as solubility. In my research, I study polymorphism of poorly soluble drugs to develop novel formulation methods for enhancing their solubility. Presented is a cross-polarized microscopy image of a nanothinfilm of an anti-inflammatory drug-aspirin, produced by solution printing the drug solution on an edible polymer called pullulan. Printed at highly non-equilibrium conditions, the spheruliticmorphology of the thin film evokes glowing fireflies in the rainforest at night. Interestingly enough, studying the phenomenon of crystal self-assembly, to me, is much like exploring a rainforest at night filled with astonishing mysteries. Just like a nocturnal creature of the rainforest that would follow the specks of light emitted by fireflies to get a clue of its vicinity, I too chase the hints given by my experiments to unravel the puzzles of crystal polymorphism.Open Restriction set for Item 105841 on 2018-04-30T17:03:37Z with date null by [email protected] by Emilie Staubs ([email protected]) on 2018-04-30T17:05:24Z
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Previous issue date: 2018-04Ope
Penerapan Data Mining untuk Memprediksi Jumlah Produk Terlaris Menggunakan Algoritma Naive Bayes Studi Kasus (Toko Prapti)
No full textToko Prapti is a small privately owned company that sells basic necessities,. So far, the prapti shop produces sales data every day, but the results obtained show that the prapti shop has not maximized the data so that it becomes a data accumulation. Therefore, the researcher conducted a study on product sales data by utilizing and applying data mining using the nave Bayes classifier algorithm to determine the interest in purchasing goods at the prapti shop. data. In this study, the author uses the waterfall system development method. The author implements this research using a web programming language, namely PHP, using the CodeIgniter framework with MySQl database. The system built with the nave Bayes algorithm includes product sales data, nave calculations of each attribute and reporting. This system produces 4 attributes that greatly affect the results of the classification. The attributes used in this research are the attributes are quarter 1, quarter 2, quarter 3 and quarter 4. Prediction results obtained using the nave Bayes algorithm produce information that can be used by stores to identify the best-selling products purchased by consumers so that it can help prapti shops to find and determine the target market more accurately. Sources of data taken from the previous 1 year with system accuracy using a confusion matrix resulted in 83.3% accuracy, 84.2% precision and 88.9% recall. Â Â Â Keywords : Data mining, Nave bayes Classifier, Code Igniter, Confusion Matri
The Saharan Landscape
No full textAlthough this image resembles footprints in the Sahara Desert during the majestic sunset, it is actually an optical microscopic image of thin film of a conjugated polymer organic semiconductor. The presented film consists of a polymer solution in chloroform which undergoes solution coating on plasma treated silicon. Organic semiconductors are organic materials that consist of systems of a pi-conjugated core of delocalized electrons. Unlike traditional inorganic semiconductors based on silicon, these materials are compatible with low-energy solution processing and enable fabrication of flexible, low cost, bio-compatible electronics. The research devoted to organic semiconductors ultimately strives to create sensors of out the materials in hopes to detect biomolecules like DNA. Just as the sun seems to set in the image, a new day for bio-compatible sensors is rising.Open Restriction set for Item 110873 on 2019-05-10T17:41:13Z with date null by [email protected] by Emilie Staubs ([email protected]) on 2019-05-10T17:43:10Z
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Previous issue date: 2019Ope
Fireflies of the rainforest: Illuminating the mysterious world of crystal polymorphism
No full textPolymorphism or the ability of molecules to pack in multiple crystal structures, is one of the most important parameters in pharmaceutical industries as it highly influences the physicochemical properties of drugs such as solubility. In my research, I study polymorphism of poorly soluble drugs to develop novel formulation methods for enhancing their solubility. Presented is a cross-polarized microscopy image of a nanothinfilm of an anti-inflammatory drug-aspirin, produced by solution printing the drug solution on an edible polymer called pullulan. Printed at highly non-equilibrium conditions, the spheruliticmorphology of the thin film evokes glowing fireflies in the rainforest at night. Interestingly enough, studying the phenomenon of crystal self-assembly, to me, is much like exploring a rainforest at night filled with astonishing mysteries. Just like a nocturnal creature of the rainforest that would follow the specks of light emitted by fireflies to get a clue of its vicinity, I too chase the hints given by my experiments to unravel the puzzles of crystal polymorphism.Ope
When Assembly Meets Processing: Tuning Multiscale Morphology of Printed Conjugated Polymers for Controlled Charge Transport
No full textProblematika Opsi Pembayaran Kembali Pinjaman Extended Fund Facilities-IMF: Suatu Analisis Ekono-Politik tentang Sebab Akibat dan Skenario Solusinya
No full textThe author of article below declares that the main problem in Indonesia economy is not only exit strategy of IMF, but also because of EFF-IMF will end on December 31, 2003., and MPR decided to stop it based on Tap MPR No.VI year 2002. In this respect; it needs to think way how to repay debt from EFF-IMF. The following criteria that Indonesia still needs the trust of international market, Indonesia should grow self confident, and Indonesia can be an expectation in national and integrity of Indonesia. According to writer that Indonesia should consider to choose option cash payment be tween 5,4-8,4 billion US. Dollars to propose toward reforming IMF
Praanggapan pada dialog mengenai kejujuran: kajian Pragmatik dalam novel Asal Kau Bahagia karya Bernard Batubara
No full textThe aims of this analysis is to examine presuppositions on dialogue about honesty through pragmatic studies. This is a qualitative study with content analysis method because this research prioritizes the content approach of dialogue in the novel. The data source of this analysis is a dialogues that contain presuppositions and imply honesty in the novel Asal Kau Bahagia by Bernard Batubara. Data provision of this analysis is done by using simak method that is applied through note-taking techniques. The results of this study indicate that 26 data containing presuppositions consisting of 9 data included in factive presuppositions, 3 lexical presuppositions data, 7 data as existantial presuppositions, 5 data as non-factual presuppositions, and 2 data are counterfactual presuppositions. In addition, the research also revealed that through several presupposition there was a message in each speech, the action would always be related to the value of honesty, but sometime it is really to be said. If it happens there is only prejudice and revenge exists. In addition, through this pragmatic, presupposition, and about honesty, the author also hopes that the results of this paper will be able to contribute ideas to the reading community about the importance of the value of honesty in friendship, romance, and in a society that has recently faded
