551 |
THE INFLUENCE OF CELLULOSE NANOCRYSTALS ON PERFORMANCE AND TRANSPORT PROPERTIES OF CEMENTITIOUS MATERIALS AND GYPSUMAnthony Paul Becerril (9669782) 16 December 2020 (has links)
<p>Concrete is in everyday life such as parking lots, buildings, bridges, and more. To keep concrete and its constituents together, binders such as cement are used. Cement’s production process is responsible for 8% of global carbon dioxide emissions as of 2018. With global warming being a severe global issue, the challenge of reducing cement carbon dioxide emissions can be greatly beneficial with even slight improvements. Various solutions to this challenge have developed over the years in the form of processing efficiency, material substitution, or material additives. Of the additives for cement and concrete that have been ventured, nanomaterials have had a strong development in recent years. Specifically, cellulose nanomaterials in the form of nanocrystals, nanofibrils, and more have demonstrated great improvement in cement’s performance resulting in a reduction in cement produced and reduction in emissions. This study expands on the knowledge of cellulose nanocrystals as an additive for cement using the formation factor methodology. Formation factor is a resistivity ratio of the specimen and pore solution that can be used in correlation to the diffusion of chloride ions through the use of the Nernst-Einstein equation. This study also investigates the effect that cellulose nanomaterials have on the mechanical properties and thermogravimetric analysis of gypsum, a material commonly used in cement production that delays the hardening of cement. </p>
|
552 |
Hydrophob/hydrophil schaltbare Nanoteilchen für die BiomarkierungDubavik, Aliaksei 15 July 2011 (has links)
There is a demand for new straightforward approaches for stabilization and solubilization of various nanoparticulate materials in their colloidal form, that pave way for fabrication of materials possessing compatibility with wide range of dispersing media. Therefore in this thesis a new general method to form stable nanocrystals in water and organics using amphiphilic polymers generated through simple and low cost techniques is presented and discussed. Amphiphilic coating agents are formed using thiolated or carboxylated polyethylene glycol methyl ether (mPEG-SH) as a starting material. These materials are available with a wide variety of chain lengths.
The method of obtaining of amphiphilic NPs is quite general and applicable for semiconductor CdTe nanocrystals as well as nanoscale noble metal (Au) and magnetic (Fe3O4) particles. This approach is based on anchoring PEG segment to the surface of a nanoparticle to form an amphiphilic palisade. Anchoring is realized via interaction of –SH (for CdTe and Au) or –COOH (in the case of magnetite) functional groups with particle’s surface. The resulting amphiphilicity of the nanocrystals is an inherent property of their surface and it is preserved also after careful washing out of solution of any excess of the ligand. The nanocrystals reversibly transfer between different phases spontaneously, i.e. without any adjustment of ionic strength, pH or composition of the phases. Such reversible and spontaneous phase transfer of nanocrystals between solvents of different chemical nature has a great potential for many applications as it constitutes a large degree of control of nanocrystals compatibility with technological processes or with bio-environments such as water, various buffers and cell media as well as their assembly and self-assembly capabilities.
|
553 |
Study of luminescent and energy properties of CsPbBr3 and CsPbI3 nanoplateletsSalique, Taddeo January 2022 (has links)
Halide perovskite semiconductor nanocrystals have been studied a lot recently because they allow a precise control over the entire visible emission spectrum and as a result, the possibility of a variety of light-emitting applications. In this study, cesium lead bromide CsPbBr3 and cesium lead iodide CsPbI3 nanoplatelets of 3, 4 and 5 monolayers (ML) have been synthesized. The absorbance and emission of each solutions and monolayer are measured and analyzed in terms of the change in excitonic nature. The results show that the exciton peak decreases with the number of monolayers with a stronger excitonic behavior in the Bromide system in comparison to the Iodine perovskite with nearly no excitonic feature for the 5 ML system. An analysis of the apparent Stokes-shift show that it increases with the number of monolayer for CsPbBr3 in comparison with the Iodide system where it decreases. The vibrational properties were quantified with Raman spectroscopy and showed that a second signifying peak of the perovskite vibration change upon quantum confinement.
|
554 |
Colloidal Semiconductor Nanoparticles as Functional Materials: Design, Assembly and ApplicationsLesnyak, Vladimir 29 January 2021 (has links)
This work summarizes results of about ten years of the author’s own research activities in the field of colloidal synthesis of semiconductor nanoparticles, their postsynthetic chemical modification, assembly, and applications. I attempted to provide a concise yet comprehensive overview presenting my own results as a part of the knowledge framework created in close collaboration with many colleagues from all over the world. This habilitation thesis consists of an introduction, explaining the motivation of the research accomplished, followed by a main part which briefly presents key achievements of the author with links to appropriate annexes, i.e. original published articles in peer review journals which are attached to this cumulative script, and completed by conclusions.
|
555 |
Dobijanje nanofosfora na bazi fluorapatita dopirani Pr3+ jonima za bio-medicinske primene / Preparation of fluorapatite-based nanophosphorus doped with Pr3+ ions for bio-medical applicationsMilojkov Dušan 08 October 2020 (has links)
<p><!--[if gte mso 9]><xml> <o:OfficeDocumentSettings> <o:AllowPNG/> </o:OfficeDocumentSettings></xml><![endif]--></p><p><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <w:DoNotShowRevisions/> <w:DoNotPrintRevisions/> <w:DoNotShowMarkup/> <w:DoNotShowComments/> <w:DoNotShowInsertionsAndDeletions/> <w:DoNotShowPropertyChanges/> <w:HyphenationZone>21</w:HyphenationZone> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:DoNotPromoteQF/> <w:LidThemeOther>EN-US</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:SplitPgBreakAndParaMark/> <w:EnableOpenTypeKerning/> <w:DontFlipMirrorIndents/> <w:OverrideTableStyleHps/> </w:Compatibility> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument></xml><![endif]--></p><p><span id="cke_bm_202S" style="display: none;"> </span><span id="cke_bm_207S" style="display: none;"> </span><span lang="EN-GB" style="font-size:12.0pt;font-family:"Times New Roman","serif";mso-fareast-font-family:"Droid Sans Fallback";color:black;mso-font-kerning:.5pt;mso-ansi-language:EN-GB;mso-fareast-language:ZH-CN;mso-bidi-language:HI"><span id="cke_bm_207E" style="display: none;"> </span><span id="cke_bm_202E" style="display: none;"> </span></span><!--[if gte mso 10]><style> /* Style Definitions */ table.MsoNormalTable{mso-style-name:"Table Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-parent:"";mso-padding-alt:0cm 5.4pt 0cm 5.4pt;mso-para-margin-top:0cm;mso-para-margin-right:0cm;mso-para-margin-bottom:8.0pt;mso-para-margin-left:0cm;line-height:107%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri","sans-serif";mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;}</style><![endif]--></p><p><!--[if gte mso 9]><xml> <o:OfficeDocumentSettings> <o:AllowPNG/> </o:OfficeDocumentSettings></xml><![endif]--><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <w:DoNotShowRevisions/> <w:DoNotPrintRevisions/> <w:DoNotShowMarkup/> <w:DoNotShowComments/> <w:DoNotShowInsertionsAndDeletions/> <w:DoNotShowPropertyChanges/> <w:HyphenationZone>21</w:HyphenationZone> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:DoNotPromoteQF/> <w:LidThemeOther>EN-US</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:SplitPgBreakAndParaMark/> <w:EnableOpenTypeKerning/> <w:DontFlipMirrorIndents/> <w:OverrideTableStyleHps/> </w:Compatibility> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument></xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" DefUnhideWhenUsed="true" DefSemiHidden="true" DefQFormat="false" DefPriority="99" LatentStyleCount="267"> <w:LsdException Locked="false" Priority="0" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Normal"/> <w:LsdException Locked="false" Priority="9" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="heading 1"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 2"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 3"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 4"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 5"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 6"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 7"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 8"/> <w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 9"/> <w:LsdException Locked="false" Priority="39" Name="toc 1"/> <w:LsdException Locked="false" Priority="39" Name="toc 2"/> <w:LsdException Locked="false" Priority="39" Name="toc 3"/> <w:LsdException Locked="false" Priority="39" Name="toc 4"/> <w:LsdException Locked="false" Priority="39" Name="toc 5"/> <w:LsdException Locked="false" Priority="39" Name="toc 6"/> <w:LsdException Locked="false" Priority="39" Name="toc 7"/> <w:LsdException Locked="false" Priority="39" Name="toc 8"/> <w:LsdException Locked="false" Priority="39" Name="toc 9"/> <w:LsdException Locked="false" Priority="35" QFormat="true" Name="caption"/> <w:LsdException Locked="false" Priority="10" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Title"/> <w:LsdException Locked="false" Priority="1" Name="Default Paragraph Font"/> <w:LsdException Locked="false" Priority="11" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Subtitle"/> <w:LsdException Locked="false" Priority="22" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Strong"/> <w:LsdException Locked="false" Priority="20" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Emphasis"/> <w:LsdException Locked="false" Priority="59" SemiHidden="false" UnhideWhenUsed="false" Name="Table Grid"/> <w:LsdException Locked="false" UnhideWhenUsed="false" Name="Placeholder Text"/> <w:LsdException Locked="false" Priority="1" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="No Spacing"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2"/> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1"/> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading Accent 1"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List Accent 1"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid Accent 1"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1 Accent 1"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2 Accent 1"/> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1 Accent 1"/> <w:LsdException Locked="false" UnhideWhenUsed="false" Name="Revision"/> <w:LsdException Locked="false" Priority="34" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="List Paragraph"/> <w:LsdException Locked="false" Priority="29" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Quote"/> <w:LsdException Locked="false" Priority="30" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Intense Quote"/> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 1"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 1"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 1"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 1"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 1"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 1"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 1"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 1"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading Accent 2"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List Accent 2"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid Accent 2"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1 Accent 2"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2 Accent 2"/> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1 Accent 2"/> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 2"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 2"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 2"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 2"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 2"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 2"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 2"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 2"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading Accent 3"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List Accent 3"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid Accent 3"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1 Accent 3"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2 Accent 3"/> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1 Accent 3"/> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 3"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 3"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 3"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 3"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 3"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 3"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 3"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 3"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading Accent 4"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List Accent 4"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid Accent 4"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1 Accent 4"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2 Accent 4"/> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1 Accent 4"/> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 4"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 4"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 4"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 4"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 4"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 4"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 4"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 4"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading Accent 5"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List Accent 5"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid Accent 5"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1 Accent 5"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2 Accent 5"/> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1 Accent 5"/> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 5"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 5"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 5"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 5"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 5"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 5"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 5"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 5"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading Accent 6"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List Accent 6"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid Accent 6"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1 Accent 6"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2 Accent 6"/> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1 Accent 6"/> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 6"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 6"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 6"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 6"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 6"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 6"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 6"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 6"/> <w:LsdException Locked="false" Priority="19" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Subtle Emphasis"/> <w:LsdException Locked="false" Priority="21" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Intense Emphasis"/> <w:LsdException Locked="false" Priority="31" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Subtle Reference"/> <w:LsdException Locked="false" Priority="32" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Intense Reference"/> <w:LsdException Locked="false" Priority="33" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Book Title"/> <w:LsdException Locked="false" Priority="37" Name="Bibliography"/> <w:LsdException Locked="false" Priority="39" QFormat="true" Name="TOC Heading"/> </w:LatentStyles></xml><![endif]--><!--[if gte mso 10]><style> /* Style Definitions */ table.MsoNormalTable{mso-style-name:"Table Normal";mso-tstyle-rowband-size:0;mso-tstyle-colband-size:0;mso-style-noshow:yes;mso-style-priority:99;mso-style-parent:"";mso-padding-alt:0cm 5.4pt 0cm 5.4pt;mso-para-margin-top:0cm;mso-para-margin-right:0cm;mso-para-margin-bottom:8.0pt;mso-para-margin-left:0cm;line-height:107%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri","sans-serif";mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;}</style><![endif]--></p><p>Luminescentni nanokristali (nanofosfori) na bazi fluorapatita (FAP-a) dopirani elementima retkih zemalja idealni su kontrastni agenti za bio-medicinske primene, kao što su detekcije, snimanja, praćenja i terapije ćelija kancera. Kancer je jedna od najčešćih bolesti modernog doba čiji uspeh lečenja zavisi od rane dijagnostike i neinvazivnog tretmana. Luminescentne nanočestice mogu uneti inovativnu paradigmu u lečenje kancera kombinovanjem biosnimanja, dijagnostike i tretmana. Za studije fluorescentnih biosnimanja nanokristali fluorapatita dopirani retkim zemljama kao kontrastni agenti pružaju značajne prednosti u vidu velikih kontrasta i dugotrajnosti luminescencije, i što je još važnije visoke biokompatibilnosti, netoksičnosti i bioaktivnosti. Glavni ciljevi ove doktorske disertacije su sinteza novih luminescentnih multifotonskih bionanomaterijala na bazi fluorapatita dopiranih jonima prazeodimijuma (Pr<sup>3+</sup>), njihova karakterizacija i evaluacija primene za fluorescentna biosnimanja kancera. Sintezom nanoprahova u umerenim uslovima metodom ko-precipitacije, a potom sušenjem na 110 <sup>o</sup>C i kalcinacijom na temperaturama od 700 i 1000 <sup>o</sup>C očekuje se pronalaženje najboljih uslova za dobijanje novih nanofosfora koji bi našli i različite bio-medicinske primene u oblasti fluorescentnih biosnimanja. Proučavane su tri vrste PrFAP nanokristala, sa 0,1%, 0,5% i 1% atomskih procenta Pr<sup>3+</sup>, zajedno sa nedopiranim FAP kontrolnim uzorkom. Nivoi energije aktivator jona Pr<sup>3+</sup> sadrže metastabilna multipletna stanja koja nude mogućnosti efikasnih emisionih linija u više boja u FAP nanokristalima, kao i u infracrvenoj i ultravioletnoj oblasti spektra. Metodom ko-precipitacije na sobnoj temperaturi (25 <sup>o</sup>C), a potom sušenjem na 110 <sup>o</sup>C, sintetisani su monofazni heksagonalni nanokristali PrFAPs nepravilnog sfernog oblika. Termičkom analizom sintetisanih uzoraka, na osnovu detektovanih temperaturnih opsega procesa dekarbonacije i dehidroksilacije, utvrđene su temperature kalcinacije od 700 i 1000 oC. Termička analiza i karakterizacija uzoraka su pokazale da Pr<sup>3+</sup> joni dovode do stabilizacije FAP strukture na višim temperaturama, što je pripisano unosu lantanoidnih jona sa specifičnim magnetnim osobinama u sistem i stvaranju jačih privlačnih sila sa O<sup>2- </sup>anjonima. Nanokristali sušeni na 100 <sup>o</sup>C i kalcinisani na 1000 <sup>o</sup>C, zbog prisustva defekata kristalne rešetke koji zadržavaju emisiju Pr<sup>3+</sup> jona, nisu pokazali luminescentne karakteristike od značaja za primene u medicinskim fluorescentnim biosnimanjima. Kalcinacijom uzoraka na 700 <sup>o</sup>C izrađen je novi tip aktiviranih fluorapatitnih nanokristala dopira / <p>Luminescent nanocrystals (nanophosphorus) based on fluorapatite (FAP) doped with rare earth elements are ideal contrast agents for biomedical applications such as cancer cell detection, imaging, tracking and therapy. Cancer is one of the most common diseases of the modern times whose success of the cure depends on early diagnosis and non-invasive treatment. Luminescent nanoparticles can bring an innovative paradigm into the treatment of cancer by combining bioimaging, diagnostics and treatment. Rare earth doped fluorapatite nanocrystals as contrast agents for studies of fluorescence bioimaging, offer significant advantages in terms of high contrasts and long-term luminescence, and more importantly high biocompatibility, non-toxicity and bioactivity. The main objectives of this doctoral dissertation are the synthesis of novel luminescent multiphoton bionanomaterials based on fluorapatites doped with praseodymium ions (Pr<sup>3+</sup>), their characterization and evaluation of their application for cancer fluorescence bioimaging. Synthesis of nanopowders under moderate conditions by the co-precipitation method, followed by dried at 110 °C and calcination at 700 and 1000 °C, is expected to find the best conditions for obtaining new nanophosphors that would find different bio-<br />medical applications in the field of fluorescence bioimaging. Three types of PrFAP nanocrystals were studied, with 0,1%, 0,5%, and 1% atomic percentages of Pr<sup>3+</sup>, together with an undoped FAP control sample. Energy levels of the Pr<sup>3+</sup> ion activator contain metastable multiplet states that offer the possibility of efficient multi-color emission lines in FAP nanocrystals as well as in the infrared and ultraviolet regions of the spectrum. Single-phase hexagonal nanocrystals PrFAPs of irregular spherical shape were synthesized by the method of co-precipitation at room temperature (25 <sup>o</sup>C) and then drying at 110 <sup>o</sup>C. Thermal analysis of the synthesized samples, based on the detected temperature ranges of the decarbonation and dehydroxylation processes, determined calcination temperatures of 700 and 1000 <sup>o</sup>C. Thermal analysis with characterization showed that Pr<sup>3+</sup> ions lead to stabilization of the FAP structure at higher temperatures, which was attributed to the entry of lanthanoid ions with specific magnetic properties into the system and the creation of stronger attractive forces with O<sup>2-</sup> anions. Nanocrystals dried at 100 <sup>o</sup>C and calcined at 1000 <sup>o</sup>C, due to the presence of crystal lattice defects that quench the emission of Pr<sup>3+</sup> ions, did not show luminescent characteristics of significance for applications in medical fluorescence imaging. Calcination of the samples at 700 <sup>o</sup>C produced a new type of activated praseodymium doped fluorapatite nanocrystals (PrFAPa) with excitation-emission profiles in the visible part of the spectrum. Physicochemical characterization confirmed spherical crystals of hexagonal structure up to a nanometer size of about 20 nm. Quantum-chemical calculations predicted that Pr<sup>3+</sup> ions would be embedded in the crystal lattice of FAP nanocrystals at the Ca2 position (6h), which was followed by deformations of the F<sup>-</sup> ion position. The assumed substitution mechanism is one Pr3+ ion for one Ca<sup>2+</sup>, with partial substitution of F<sup>– </sup>anions with O<sup>2–</sup> and OH<sup>–</sup> and creation of vacancies due to achieving system neutrality. The results of in vitro biocompatibility and hemocompatibility showed that PrFAP nanocrystals were not toxic to living cells. In addition, the internalization of PrFAPa nanocrystals by skin (A431) and lung (A549) cancer cells was studied using fluorescence-based confocal microscopy and wide-field microscopy. The nanocrystals show characteristic green emission at 545 nm (<sup>3</sup>P<sub>0</sub>→<sup>3</sup>H<sub>5</sub> transition of Pr<sup>3+</sup> ion) and orange emission at 600 nm (<sup>1</sup>D<sub>2</sub>→<sup>3</sup>H<sub>4</sub>), which we use to discriminate from cell autofluorescence. Studies of the images obtained by confocal microscopy in the blue, green, and red channels revealed that nanocrystals could recognize the cell surface and adhere to it, but they did not confirm the entry of nanocrystals into the cells. The wide-field microscopy detected emission transitions in green and orange color, and confirmed that the luminescent signal was coming from inside the cells. Using resonant excitation of PrFAP nanocrystals at 488 nm and emission of 600 nm, confocal microscopy extracted the fluorescence signal from inside the cancer cells. Orthogonal projections across 3D confocal stacks show that the nanocrystals are able to enter the cells positioning themselves within the cytoplasm. Overall, the obtained PrFAPa nanocrystals are biocompatible and of the tested types, the 0,5% Pr<sup>3+</sup> doped nanocrystals show the highest promise as a tracking nanoparticle probe for bioimaging applications.</p>
|
556 |
Fibres optiques vitrocéramiques pour application laser / Glass ceramic optical fibers for laser applicationPomarede, Damien 23 March 2018 (has links)
Cette thèse porte sur le développement de fibres optiques de type cœur/gaine, dont le cœur est composé de vitrocéramiques transparentes. Le système étudié est composé d’une matrice de silice stabilisant la phase ZnGa2O4 sous la forme de nano cristaux, pouvant être dopés par des ions de métaux de transition tels que le chrome (III) et le nickel (II). Les verres précurseurs de vitrocéramiques ont été synthétisés par fusion trempe, étirés sous forme de fibres optiques par la méthode poudre puis recuits thermiquement afin d’obtenir des fibres optiques à cœur vitrocéramiques optiquement actives. L’optimisation conjointe de la composition des verres précurseurs, des paramètres de fibrage, de la composition finale des fibres et du protocole de recuit thermique de cristallisation, ont permis de maximiser leurs propriétés de luminescence autour de 700 nm et 1350 nm pour les fibres dopées par du chrome (III) et du nickel (II) respectivement. Ces types de fibres peuvent trouver des applications dans les domaines de la thermométrie optique, des sources optiques, des amplificateurs et des lasers fibrés. En particulier, nous avons démontré que le spectre d’émission autour de 1350 nm des fibres dopées par du nickel (II) présente une largeur à mi-hauteur supérieure à 270 nm, meilleure que celle des sources commerciales centrées autour de 1300 nm. Le niveau de puissance émise, de l’ordre d’une trentaine de microwatts, est quasiment compatible avec les applications de source optique pour l’OCT. Des développements ultérieurs visant à réduire le niveau de pertes dans ces fibres et de maximiser l’efficacité du dopant permettrons d’amener cette technologie à un niveau de performance compatible avec ces applications. Ces résultats encourageants ont motivés le dépôt d’une demande de protection des fibres et de leur procédé d’élaboration par un brevet. / This thesis focuses on the development of core/clad type optical fibers where the core is composed of transparent glass ceramics. The system considered was composed of a silica matrix where ZnGa2O4 nanocrystals can be stabilized. Those crystals can interestingly be doped with transition metal ions such as chromium (III) or nickel (II) ions. The precursor glass were synthetized by melt quenching method, drawn into fibers through the powder in tube process, and subsequently annealed to produce optically active glass ceramic optical fibers. The starting glass composition together with the drawing parameters, the fiber core composition and the annealing protocol were optimized in order to maximize the luminescence properties around 700 nm and 1350 nm in chromium (III) and nickel (II) doped fibers respectively. Such type of fibers are interesting for the domains of optical thermometry, fibered sources, amplifiers and lasers. In particular, we demonstrated that the emission spectrum around 1350 nm of nickel (II) doped glass ceramic fibers exhibited a full width at half maximum above 270 nm, wider than that of 1300 nm centered commercial sources. The overall power outcome is about thirty micro watts, which is almost suitable for OCT applications. Further developments aiming at reducing the optical losses in the fibers and in maximizing the dopant efficiency will allow to reach the applications requirements. Those promising results led to a patent application on the fibers composition and their fabrication process.
|
557 |
Micro- and Nano-Raman Characterization of Organic and Inorganic MaterialsSheremet, Evgeniya 07 October 2015 (has links)
Die Raman-Spektroskopie ist eine der nützlichsten optischen Methoden zur Untersuchung der Phononen organischer und anorganischer Materialien. Mit der fortschreitenden Miniaturisierung von elektronischen Bauelementen und der damit einhergehenden Verkleinerung der Strukturen von der Mikrometer- zur Nanometerskala nehmen das Streuvolumen und somit auch das Raman-Signal drastisch ab. Daher werden neue Herangehensweisen benötigt um sie mit optischer Spektroskopie zu untersuchen. Ein häufig genutzter Ansatz um die Signalintensität zu erhöhen ist die Verwendung von Resonanz-Raman-Streuung, das heißt dass die Anregungsenergie an die Energie eines optischen Überganges in der Struktur angepasst wird. In dieser Arbeit wurden InAs/Al(Ga)As-basierte Multilagen mit einer Periodizität unterhalb des Beugungslimits mittels Resonanz-Mikro-Raman-Spektroskopie und Raster-Kraft-Mikroskopie (AFM) den jeweiligen Schichten zugeordnet.
Ein effizienterer Weg um die Raman-Sensitivität zu erhöhen ist die Verwendung der oberflächenverstärkten Raman-Streuung (SERS). Sie beruht hauptsächlich auf der Verstärkung der elektromagnetischen Strahlung aufgrund von lokalisierten Oberflächenplasmonenresonanzen in Metallnanostrukturen.
Beide oben genannten Signalverstärkungsmethoden wurden in dieser Arbeit zur oberflächenverstärkten Resonanz-Raman-Streuung kombiniert um geringe Mengen organischer und anorganischer Materialien (ultradünne Cobalt-Phthalocyanin-Schichten (CoPc), CuS und CdSe Nanokristalle) zu untersuchen. Damit wurden in beiden Fällen Verstärkungsfaktoren in der Größenordnung 103 bis 104 erreicht, wobei bewiesen werden konnte, dass der dominante Verstärkungsmechanismus die elektromagnetische Verstärkung ist.
Spitzenverstärkte Raman-Spektroskopie (TERS) ist ein Spezialfall von SERS, bei dem das Auflösungsvermögen von Licht unterschritten werden kann, was zu einer drastischen Verbesserung der lateralen Auflösung gegenüber der konventionellen Mikro-Raman-Spektroskopie führt. Dies konnte mit Hilfe einer Spitze erreicht werden, die als einzelner plasmonischer Streuer wirkt. Dabei wird die Spitze in einer kontrollierten Weise gegenüber der Probe bewegt. Die Anwendung von TERS erforderte zunächst die Entwicklung und Optimierung eines AFM-basierten TERS-Aufbaus und TERS-aktiver Spitzen, welche Gegenstand dieser Arbeit war. TERS-Bilder mit Auflösungen unter 15 nm konnten auf einer Testprobe mit kohlenstoffhaltigen Verbindungen realisiert werden. Die TERS-Verstärkung und ihre Abhängigkeit vom Substratmaterial, der Substratmorphologie sowie der AFM-Betriebsart wurden anhand der CoPc-Schichten, die auf nanostrukturierten Goldsubstraten abgeschieden wurden, evaluiert. Weiterhin konnte gezeigt werden, dass die hohe örtliche Auflösung der TERS-Verstärkung die selektive Detektion des Signals weniger CdSe-Nanokristalle möglich macht.:Bibliografische Beschreibung 3
Parts of this work are published in 5
Table of contents 7
List of abbreviations 10
Introduction 11
Chapter 1. Principles of Raman spectroscopy, surface- and tip-enhanced Raman spectroscopies 15
1.1. Raman spectroscopy: its benefits and limitations 15
1.2. Electromagnetic enhancement in SERS and TERS 18
1.2.1. Light scattering by a sphere 19
1.2.2. Image dipole effect 22
1.3. Chemical enhancement 23
1.4. Summary 25
Chapter 2. Raman and AFM profiling of nanocrystal multilayer structures 27
2.1. Materials and methods 27
2.1.1. Nanocrystal growth 27
2.1.2. Sample preparation 28
2.1.3. TEM, AFM and Raman measurements 29
2.2. Structure of embedded NCs 31
2.2.1. Size and shape of embedded NCs by TEM 31
2.2.2. Phonon spectra of NCs 32
2.3. Profiling on NC multilayers 34
2.3.1. AFM profiling of multilayer NC structures 34
2.3.2. Raman profiling of NC multilayers 38
2.4. Summary 40
Chapter 3. Surface-enhanced Raman spectroscopy 43
3.1. Materials and methods 43
3.1.1. SERS substrate preparation 43
3.1.2. Organic and inorganic materials 45
3.1.3. Micro-Raman spectroscopy measurements 46
3.1.4. Micro-ellipsometry 46
3.1.5. Numerical simulations 47
3.2. SERS on organic films 47
3.2.1. SERS enhancement of CoPc 48
3.2.2. Polarization dependence of enhancement in SERS 51
3.3. SERS by nanocrytals 53
3.4. Summary 55
Chapter 4. Implementation of tip-enhanced Raman spectroscopy 57
4.1. TERS enhancement factor 58
4.2. State of the art of optical systems for TERS 60
4.3. Implementation of the optical system 61
4.4. TERS tips 64
4.4.1. State of the art of TERS tips 64
4.4.2. Fabrication of tips for AFM-based TERS 66
4.4.3. Mechanical properties of fully metallic TERS tips 68
4.5. Summary 74
Chapter 5. Tip-enhanced Raman spectroscopy imaging 75
5.1. Materials and methods 75
5.1.1. Preparation of multi-component sample 75
5.1.2. TERS experiments 76
5.1.3. Simulations of electric field enhancement 76
5.2. High resolution discrimination of carbon-containing compounds by TERS 78
5.3. Effect of substrate material and morphology on TERS enhancement 82
5.4. Effect of the AFM imaging mode on TERS enhancement 85
5.5. TERS on free-standing colloidal CdSe NCs 90
5.6. Summary 91
Conclusions 93
References 95
List of figures 104
Erklärung 109
Lebenslauf 111
Publication list 112
Acknowledgements 117
|
558 |
Production of adsorptive material from modified nanocrystals cellulose for industrial applicationBanza, Musamba Jean Claude 05 1900 (has links)
PhD. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Water is the essence of life, yet it is progressively polluted by dyes, heavy metal ions, food
additives, medicines, detergents, agrochemicals, and other toxins from industrial,
municipal, and agricultural sources. Among the different wastewater treatment
technologies, adsorption is a technique that, when used in conjunction with a welldesigned
system, produces high-quality treated water at a reasonable cost. For water
treatment, activated carbon is the most often employed adsorbent. Its manufacture, on the
other hand, is energy demanding, costly, and creates greenhouse emissions. As a result,
finding low-cost alternative adsorbents from industrial and agricultural waste and
biomass has attracted a lot of interest. In this context, developing sustainable platforms
for wastewater treatment using sustainable nanomaterials such as cellulose nanocrystals
(CNCs) is a unique technique with a low carbon footprint. CNCs, which are made by
hydrolyzing pulp fibers in sulfuric acid, are rod-like nanomaterials with a lot of
remarkable qualities including high specific surface area, high specific strength,
hydrophilicity, biodegradability, and surface functionalization.
These characteristics, as well as their accessibility, make them suitable candidates for
water treatment applications. However, because of their great colloidal stability and
nano-dimensions, extracting these CNCs after usage in water treatment is difficult. To
overcome this problem, including these CNCs into nanocomposite systems that can be
readily separated after usage in batch and continuous water treatment processes is a great
concept. Furthermore, pure CNCs have low selectivity towards a wide range of water
pollutants, necessitating surface functionalization to provide this selectivity. As a result,
this thesis investigates the extraction of CNCs from millet husk waste and waste papers,
the development of CNC-incorporated nanocomposites and evaluation of their
adsorption characteristics using batch and fixed bed column adsorption studies, and (ii)
the evaluation of the selective adsorption characteristics of surface functionalized CNCs
and their ability to tailor the nanocomposites' characteristics for use in water treatment
applications. The response surface methodology, artificial neural network, and adaptive
neuro-fuzzy inference systems were also applied to model the removal of heavy metal
ions.
The first part of the research ( cellulose nanocrystals extraction and optimization)
The cellulose nanocrystals were extracted from millet husk residue waste using a
homogenized acid hydrolysis method. The effects of the process variables
homogenization speed (A), acid concentration (B), and acid to cellulose ratio (C) on the
yield and swelling capacity were investigated and optimized using the Box Behnken
design (BBD) method in response surface methodology. The numerical optimization
analysis results showed that the maximum yield of CNCs and swelling capacity from
cellulose was 93.12 % and 2.81 % obtained at homogenization speed, acid concentration,
and acid to cellulose ratio of 7464.0 rpm, 63.40 wt %, and 18.83 wt %, respectively. ANOVA
revealed that the most influential parameter in the model was homogenization speed for
Yield and acid concentration for swelling capacity. The TGA revealed that cellulose had
greater heat stability than CNCs. The functional groups of CNCs and cellulose were
identical according to the FTIR data. When compared to cellulose, the SEM picture of
CNCs is porous and shows narrow particle size with needle-like shape. The XRD pattern
revealed an increase in CNC intensity.
The second part of the research ( CNCs modification for selective removal)
A novel type of recyclable adsorbents with outstanding adsorption capability was
produced using CNCs with succinic anhydride and EDTA. and their adsorption
properties were studied in detail utilizing batch adsorption experiments of Chromium
(VI) in aqueous solution. The effects of several factors on Cr (VI) adsorption were
examined, including contact duration, adsorbent dose, starting concentration, pH, and
temperature. The cellulose nanocrystals treated with succinic anhydride and EDTA
possessed a needle-like form, high porosity, and a narrow particle size distribution. The
carboxylate transition of the carboxyl group of cellulose was verified by FTIR. XRD
analysis of particles after modification revealed the presence of additional phases, which
were attributed to succinic anhydride and EDTA modification. A spontaneous exothermic
adsorption process was validated by the observed thermodynamic characteristics. The
best model for describing adsorption kinetics and mechanism was a pseudo-second order
kinetic and intra-particle diffusion model. The Langmuir adsorption isotherm was seen in
equilibrium adsorption data, with a maximum adsorption capacity (qmax) of 387.25± 0.88
mgL-1. We showed that the removal effectiveness of Cr (VI) maintained at 220± 0.78 mg.g-1after 6 adsorption-desorption cycles, and that the CNC-ALG hydrogel beads are excellent adsorbents for the selective removal of Cr (VI) from wastewaters.
The third part of the research ( modeling of removal of heavy metal ions using RSM,
ANN and quantum mechanism studies )
The effects of contact time , pH, nanoparticle dose, and beginning Cd2+ concentration on
Cd2+ removal were examined using the central composite design (CCD) technique. The
performance and prediction capabilities of Response Surface Methodology (RSM) and
Artificial Neural Network (ANN) modelling methodologies were explored, as well as their
performance and prediction capacities of the response (adsorption capacity). The
process was also described using the adsorption isotherm and kinetic models. Statistical
data, on the other hand, revealed that the RSM-CCD model beat the ANN model technique. The optimum conditions were determined to be a pH of 5.73, a contact time of 310 minutes, an initial Cd2+ concentration of 323.04 mg/L, a sorbent dosage of 16.36 mg, and an adsorption capacity of 440.01 mg/g. The spontaneous adsorption process was well
characterized by the Langmuir model, and chemisorption was the dominant regulator.
The binding energy gaps HOMO-LUMO were used to find the preferred adsorption sites.
The fourth part of research ( optimization of removal using ANN and ANFIS)
An artificial neural network and an adaptive neuro-fuzzy inference system were utilized
to predict the adsorption capability of mix hydrogels in the removal of nickel (II) from
aqueous solution. Four operational variables were evaluated in the ANFIS model to
determine their influence on the adsorption study, including starting Ni (II) concentration
(mg/L), pH, contact time (min), and adsorbent dosage (mg/L) as inputs and removal
percentage (percent) as the single output. In contrast, 70% of the data was employed to
develop the ANN model, while 15% of the data was used in testing and validation. To train
the network, feedforward propagation with the Levenberg-Marquardt algorithm was
used. To optimise, design, and develop prediction models for Ni (II) adsorption using
blend hydrogels, (ANN) and (ANFIS) models were employed for trials. The results
demonstrate that the ANN and ANFIS models are viable prediction techniques for metal
ion adsorption.
The fourth part of research ( mechanistic modeling and optimization of removal using
ANN, RSM and ANFIS)
An artificial neural network, response surface methodology and an adaptive neuro-fuzzy
inference system were utilized to predict the adsorption capability of modified cellulose
nanocrystals and sodium alginate for the removal of Cr (VI) from aqueous solution. Four
variables such as time, pH, concentration, and adsorbent dose were evaluated to
determine their influence on the adsorption study. To examine the viability of the models,
five statistical functions ( RMSE, ARE, SSE, MSE, and MPSD) were applied. absorption
mechanism was described via four mechanistic models (Film diffusion, Weber and
Morris, Bangham, and Dummwald-Wagner models. Further statistical indices supported
ANFIS as the best prediction model for adsorption compared to ANN and RSM. Film
diffusion was identified as the rate-limiting process via mechanistic modelling.
The sixth part of research (continuous fixed-bed column study)
The hydrogel's technical feasibility for adsorption of Cu2+, Ni2+, +Cd2+, and Zn2+ ions
from the packed bed column's produced AMD was assessed. The hydrogel was considered
to have a high potential for significant interactions with dangerous metal ions. This
characteristic, together with the adsorbent's availability, low cost, and efficient
regeneration of the spent adsorbent, distinguishes it from the many other adsorbents
described in the literature by other researchers. With a bed height of 25 cm, an influent
metal ion concentration of 10 mg/l, and a flow velocity of 10 ml/min, the bed performed
better. As a consequence, the breakthrough curve for the packed bed experiment shows
that the breakthrough points were approached sooner by increasing the flow rate and
influent concentration, and later by increasing the bed height. The experimental results
were satisfactorily described by the BDST, Yoon–Nelson, and Thomas models. The
hydrogels had a net-work structure and more homogeneous porosity, according to the
SEM, TGA, XRD, and FTIR results for CNCs. The hydrogels revealed varied degrees of
opacity and heavy metal ions absorption capacity depending on the temperature of the
analysis. Diffraction confirmed the existence of crystalline structures and the presence of
carboxyl and amide groups.
|
559 |
INVESTIGATION OF NANOCELLULOSE MECHANICAL PROPERTIES AND INTERACTIONS IN SALT AND SURFACTANT SOLUTIONS MEASURED BY ATOMIC FORCE MICROSCOPY / NANOCELLULOSE PROPERTIES MEASURED BY ATOMIC FORCE MICROSCOPYMarway, Heera January 2017 (has links)
This understanding of nanocellulose can be directly applied in future formulation design to use nanocellulose in polymer nanocomposites, foams, emulsions, latexes, gels and biomedical materials. / In this study, the potential of nanocellulose as a reinforcing agent in composite materials was investigated using atomic force microscopy (AFM). AFM was used to probe the mechanical properties of nanocelluloses and to investigate their interactions and adhesion in liquid media. Amplitude modulated-frequency modulated AFM was used to map the mechanical properties of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs). Results showed Young’s moduli of 90 GPa and 120 GPa for CNCs and CNFs, respectively, which are comparable to literature values determined using other methods.
Additionally, colloid probe AFM was implemented to observe the interactions (attractive, repulsive, steric, adhesive) between cellulose and silica colloid probes with anionic CNCs (containing either a Na+ or H+ counterion) and cationic CNCs. Colloid probe AFM measurements were carried out in five different liquid media: two salt solutions (NaCl and CaCl2) and three surfactant solutions (cationic cetyltrimethylammonium bromide, CTAB; anionic sodium dodecyl sulfate, SDS; and nonionic Triton X100). It was found that low salt concentrations resulted in electrostatic repulsion and high adhesion, whereas the reverse was observed at high salt concentrations. On the contrary, an increased surfactant concentration and increased number of surfactant aggregates (micelles, bilayers, etc.) resulted in increased adhesion. Surprisingly, the interactions were strongly dependent on the CNC counterion as surfactant adsorption seemed to be primarily driven by electrostatic interactions; CTAB adsorbed more to anionic CNCs, SDS adsorbed more to cationic CNCs and Triton X100 adsorbed minimally to all CNCs. Electrophoretic mobility and particle size data showed complementary results to colloid probe AFM, indicating that interactions between surfactants and CNC films and CNCs in suspension are closely related. This research suggests that CNCs have potential as reinforcing agents due to their high strength and the tunability of their interactions through the simple addition of salts or surfactants. This understanding can be directly applied in future formulation design to use nanocellulose in polymer nanocomposites, foams, emulsions, latexes, gels and biomedical materials. / Thesis / Master of Applied Science (MASc) / Nanocellulose is a sustainable nanomaterial most commonly extracted from plants and trees. In recent research, nanocellulose has been shown to have potential as a reinforcing agent for materials such as plastics, foams, paints and adhesives. In this study, the potential of nanocellulose was investigated using atomic force microscopy (AFM). As predicted, AFM measurements indicated that nanocellulose has a high stiffness, supporting the substitution of this biobased material in the place of metals and synthetic fibres. AFM was also used to examine particle interactions in salt and soap-like (surfactant) solutions; changes in nanocellulose size and charge were used to support the findings. Negatively charged nanocellulose interacted more with positively charged surfactants and vice versa. Low salt and high surfactant concentrations led to high adhesion and better material compatibility, which is preferred. This understanding can help us design better nanocellulose materials for future applications.
|
560 |
Synthesis and Property Characterization of Novel Ternary Semiconductor NanomaterialsMao, Baodong 26 June 2012 (has links)
No description available.
|
Page generated in 0.0711 seconds