Name: facet-to-facet linking of shape-anisotropic colloidal cadmium chalcogenide nanostructures
Uploaded: 2017-08-10T14:00:00.000+00:00
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Description: Watch this Scientific Journal Video about Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures at JoVE.com

עבודה זו נתמכה על ידי JCO A * כוכב Investigatorship הענק (פרוייקט מס 1437C 00135), A * כוכב & הנדסה המועצה במגזר הציבורי מענקי מחקר (פרויקט מס 1421200076), ומדע מיזמי מחקר משותף של JSPS-NUS הענק (WBS R143-000-611-133).

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	<li>Figuerola, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=End-to-End+Assembly+of+Shape-Controlled+Nanocrystals+via+a+Nanowelding+Approach+Mediated+by+Gold+Domains.">End-to-End Assembly of Shape-Controlled Nanocrystals via a Nanowelding Approach Mediated by Gold Domains.</a> Adv. Mat. 21, 550-554 (2009).</li><li>Tang, Z., Kotov, N. A., Giersig, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spontaneous+Organization+of+Single+CdTe+Nanoparticles+into+Luminescent+Nanowires.">Spontaneous Organization of Single CdTe Nanoparticles into Luminescent Nanowires.</a> Science. 297, 237-240 (2002).</li><li>Kim, D., Kim, W. D., Kang, M. S., Kim, S. -. H., Lee, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Organization+of+Nanorods+into+Ultra-Long+Range+Two-Dimensional+Monolayer+End-to-End+Network.">Self-Organization of Nanorods into Ultra-Long Range Two-Dimensional Monolayer End-to-End Network.</a> Nano Lett. 15, 714-720 (2015).</li><li>Schliehe, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrathin+PbS+Sheets+by+Two-Dimensional+Oriented+Attachment.">Ultrathin PbS Sheets by Two-Dimensional Oriented Attachment.</a> Science. 329, 550-553 (2010).</li><li>Chakrabortty, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facet+to+facet+Linking+of+Shape+Anisotropic+Inorganic+Nanocrystals+with+Site+Specific+and+Stoichiometric+Control.">Facet to facet Linking of Shape Anisotropic Inorganic Nanocrystals with Site Specific and Stoichiometric Control.</a> Nano Lett. 16, 6431-6436 (2016).</li><li>Leatherdale, C. A., Woo, W. K., Mikulec, F. V., Bawendi, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+Absorption+Cross+Section+of+CdSe+Nanocrystal+Quantum+Dots.">On the Absorption Cross Section of CdSe Nanocrystal Quantum Dots.</a> J Phys Chem B. 106, 7619-7622 (2002).</li><li>Dabbousi, B. O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=(CdSe)ZnS+Core-Shell+Quantum+Dots:+Synthesis+and+Characterization+of+a+Size+Series+of+Highly+Luminescent+Nanocrystallites.">(CdSe)ZnS Core-Shell Quantum Dots: Synthesis and Characterization of a Size Series of Highly Luminescent Nanocrystallites.</a> J Phys Chem B. 101, 9463-9475 (1997).</li><li>Carbone, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+Micrometer-Scale+Assembly+of+Coilloidal+CdSe/CdS+Nanorods+Prepared+by+Seeded+Grwoth+Approach.">Synthesis and Micrometer-Scale Assembly of Coilloidal CdSe/CdS Nanorods Prepared by Seeded Grwoth Approach.</a> Nano Lett. 7, 2942-2950 (2007).</li><li>Shaviv, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Absorption+properties+of+Metal-Semiconductor+Hybrid+Nanoparticles.">Absorption properties of Metal-Semiconductor Hybrid Nanoparticles.</a> ACS Nano. 5, 4712-4719 (2011).</li><li>Lim, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Synthesis+of+CdSe+Tetrapods+with+High+Morphological+Uniformity+by+the+Persistent+Kinetic+Growth+and+the+Halide-Mediated+Phase+Transformation.">Controlled Synthesis of CdSe Tetrapods with High Morphological Uniformity by the Persistent Kinetic Growth and the Halide-Mediated Phase Transformation.</a> Chem Mat. 25, 1443-1449 (2013).</li></ol>

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קישור בטכניקה המתוארת בעבודה זו מאפשרת צורה-אניסוטרופי קדמיום chalcogenide חלקיקים יכולים עוברים קטיון עם Ag+ להתאחד, היבט היבט, לתוך הרכבות כגון רשתות קוויות או רשתות מסועף. כשל כדי ליצור מכלולים היטב התפזרו, מקיף של פן-כדי-היבט חלקיקים מקושר לעתים קרובות בגלל שתי סיבות: (i) ODPA לא מפוזרת גם ה...

הרכבה בבימויו של מוליכים למחצה colloidal רכיבי Nc מציע שער סינתטי הזיוף של nanostructures physicochemical הסינתטיות גם הסכום קולקטיבית או שונים בתכלית מן שלהם אבני בניין הפרט NC1 , 2 , 3 , 4. בין הגישות השונות להתכנסות ננו-חלקיק, שיטת הצירוף מונחה - ב אילו רכיבי Nc בעיקרו מקובעים אחד עם השני - מתבלטת המאפשר להשתלב אלקטרונית interparticle. עם זאת, מצורף אוריינטציה המקובלת בדרך כלל דורש איזון עדין של חלקיקים דיפול - ליגנד -, אינטראקציות ממס מבוסס בדרך כלל שקשה לבצע ולעשות החלים על מערכות שונות NC.
לאחרונה פיתחנו שיטה רטוב-כימי של covalently להצטרף צורה-אניסוטרופי קדמיום chalcogenide רכיבי Nc על ידי החדרת ביניים אורגניים תגובתי באמצעות תהליך סלקטיבי-אתר התגרענות. החלקיקים מקושרים לאחר מכן על ידי היתוך גרעיני ספונטני של תגובתי תחומים ביניים אורגניים5. למרות הטכניקה עדיין מבוססת על מנגנון מונחה המצורף, יש הרבה פחות צורך לשקול אינטראקציות interparticle חלש, ובכך מאפשר יותר גמישות ובקרה. החיבור של צורה-אניסוטרופי קדמיום chalcogenide רכיבי Nc מבוצע על ידי המרת הראשון שלהם היבטים עצה chalcogenide כסף באמצעות תהליך חלקי קטיון (בתמיסה); זה ואחריו הסרת סלקטיבי ליגנדים passivating פני השטח. השרות החשאי ואז לבוא יחד באמצעות היתוך גרעיני של הצדדים החשופים chalcogenide כסף, וכתוצאה מכך מכלולים של קדמיום chalcogenide רכיבי Nc המקושרות end-to-end.
ב פרוטוקול זה, נדגים הטכניקה המקשרים יכול להיות מיושם למגוון של צורה-אניסוטרופי קדמיום chalcogenide רכיבי Nc (קרי, נזרע CdSe NRs תקליטורים ו NRs CdSe מתחילה CdSe או תוכנית-המיתאר), שרשראות מניב NR ליניארי ארוכה או TP מסועף מאוד רשתות. תוצאות אלו מראים כי הטכניקה ניתן להרחיב את מגוון רחב של צורות NC ו נוטה? כסף קטיון מתכת chalcogenides.

<table><tbody><tr><td>Cadmium oxide (CdO), 99.5%</td><td>Sigma Aldrich</td><td></td><td>Highly toxic</td></tr><tr><td>Tri-n-octylphosphine oxide (TOPO), 90 % and 99%</td><td>Sigma Aldrich</td><td></td><td>Technical and analytical grade</td></tr><tr><td>Cadmium acetylacetonate (Cd(acac)&lt;sub&gt;2&lt;/sub&gt;), 99.9%</td><td>Sigma Aldrich</td><td></td><td>Highly toxic</td></tr><tr><td>Hexadecanediol (HDDO), 90%</td><td>Sigma Aldrich</td><td></td><td>Technical grade</td></tr><tr><td>1-octadecene (ODE), 90%</td><td>Sigma Aldrich</td><td></td><td>Technical grade</td></tr><tr><td>Dodecylamine (DDA), 98%</td><td>Sigma Aldrich</td><td></td><td>Toxic</td></tr><tr><td>Cadmium nitrate tetrahydrate ((CdNO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt;.4H&lt;sub&gt;2&lt;/sub&gt;O), 98%</td><td>Sigma Aldrich</td><td></td><td>Highly toxic</td></tr><tr><td>Myristic acid (MA), 99%</td><td>Sigma Aldrich</td><td></td><td>Analytical grade</td></tr><tr><td>Octyl phosphonic acid (OPA), 97%</td><td>Sigma Aldrich</td><td></td><td>Analytical grade</td></tr><tr><td>Oleylamine (Oly), 70%</td><td>Sigma Aldrich</td><td></td><td>Technical grade</td></tr><tr><td>Hexadecyltrimethylammonium bromide (CTAB), 95%</td><td>Sigma Aldrich</td><td></td><td>Toxic</td></tr><tr><td>Selenium pellets (Se, 5 mm), 99.99%</td><td>Sigma Aldrich</td><td></td><td>Analytical grade</td></tr><tr><td>Hexadecylamine (HDA), 90%</td><td>Alfa Aesar</td><td></td><td>Technical grade, toxic</td></tr><tr><td>n-tetradecylphosphonic acid (TDPA), 98%&amp;nbsp;</td><td>Alfa Aesar</td><td></td><td>Analytical grade</td></tr><tr><td>Silver nitrate (AgNO&lt;sub&gt;3&lt;/sub&gt;), 99.9%</td><td>Alfa Aesar</td><td></td><td>Analytical grade</td></tr><tr><td>Oleic acid (OA), 90%</td><td>Alfa Aesar</td><td></td><td>Technical grade</td></tr><tr><td>Tri-n-octylphosphine (TOP), 97%</td><td>Strem</td><td></td><td>Analytical grade, toxic, air sensitive</td></tr><tr><td>n-hexylphosphonic acid (HPA), 97%</td><td>Strem</td><td></td><td>Analytical grade</td></tr><tr><td>n-octadecylphosphonic acid (ODPA), 97%</td><td>Strem</td><td></td><td>Analytical grade</td></tr><tr><td>Tellurium powder (Te), 99.9%</td><td>Strem</td><td></td><td>Air sensitive</td></tr><tr><td>Tri-n-butylphosphine (TBP), 99%</td><td>Strem</td><td></td><td>Analytical grade, highly toxic, air sensitive</td></tr><tr><td>Diisooctylphosphonic acid (DIPA), 90%</td><td>Fluka</td><td></td><td>Technical grade, toxic</td></tr></tbody></table>

facet-to-facet linking of shape-anisotropic colloidal cadmium chalcogenide nanostructures

כאן, אנו מתארים פרוטוקול המאפשר nanocrystals chalcogenide קדמיום צורה-אניסוטרופי (רכיבי Nc), כגון nanorods (NRs) ו- tetrapods (TPs), במטרה להיות covalently ולא site-specifically מקושרים באמצעות היבטים הקצה שלהם, וכתוצאה מכך פולימר דמוי ליניארי או מסועף רשתות. ההליך המקשרים מתחיל עם קטיון תהליך שבו מגזרי קצה chalcogenide קדמיום רכיבי Nc יומרו תחילה chalcogenide כסף. זה ואחריו הסרת סלקטיבי ליגנדים על פני השטח שלהם. התוצאה קדמיום chalcogenide רכיבי Nc עם סוף chalcogenide כסף תגובתי ההיבטים הרבים שיש נתיך באופן ספונטני על קשר אחד עם השני, ובכך הקמת מצורף פן-כדי-היבט interparticle. דרך הבחירה הביוספירה של קודמן ריכוזים, רשת נרחבת של רכיבי Nc המקושר יכול להיות מיוצר. אפיון מבניים של השרות החשאי המקושרת מתבצעת באתר ברזולוציה נמוכה גבוה במיקרוסקופ אלקטרונים הילוכים (TEM), כמו גם הספקטרומטריה ואנליזת-אנרגיה, אשר מאשרים את הנוכחות של chalcogenide כסוף התחומים בין שרשראות של קדמיום chalcogenide רכיבי Nc.

באמצעות CdSe-נזרע NRs תקליטורים כמערכת מודל, כמופיע ב איור 1(א), הפגנו שנוכל להשתמש תהליך חלקי של exchange Ag+ במיוחד להפוך את הצדדים בקצות NR Ag2ס הצדדים2S Ag הם כתרים על ידי DDA, אשר מגיב ODPA ויה לתגובה חומצה בסיס ליצירת לא מסיסים מלח5</s...

Watch this Scientific Journal Video about Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures at JoVE.com

Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

פרוטוקול המפרט כיצד צורת אניסוטרופי קדמיום colloidal chalcogenide nanocrystals יכולים להיות מקושרים covalently באמצעות היבטים הקצה שלהם מוצג כאן.

פן-כדי-היבט הקישור של קדמיום Colloidal צורה-אניסוטרופי Chalcogenide Nanostructures

Here, we describe a protocol that allows for shape-anisotropic cadmium chalcogenide nanocrystals (NCs), such as nanorods (NRs) and tetrapods (TPs), to be ...

facet-to-facet-linking-shape-anisotropic-colloidal-cadmium

Universidad San Sebastian

Research

JoVE Journal

Chemistry

7.6K Views.  National University of Singapore. פרוטוקול המפרט כיצד צורת אניסוטרופי קדמיום colloidal chalcogenide nanocrystals יכולים להיות מקושרים covalently באמצעות היבטים הקצה שלהם מוצג כאן.

Video: Facet-to-facet Linking of Shape-anisotropic Colloidal Cadmium Chalcogenide Nanostructures

Compact Quantum Dots for Single-molecule Imaging

Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.
Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.
Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm).

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging. Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

נקודות קוונטיות קומפקטיות להדמית מולקולה בודדה

Single-molecule imaging is an important tool for  understanding the mechanisms of biomolecular function and for visualizing the  spatial and temporal ...

Engineering

Revealing Dynamic Processes of Materials in Liquids Using Liquid Cell Transmission Electron Microscopy

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.

We have developed a self-contained liquid cell, which allows imaging through liquids using a transmission electron microscope. Dynamic processes of nanoparticles in liquids can be revealed in real time with sub-nanometer resolution.

חושף תהליכים דינמיים של חומרים בנוזלים באמצעות מיקרוסקופ אלקטרוני הילוכים סלולריים נוזלי

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted ...

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

סינתזה ואפיון של קולואידים מולקולריים

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

We propose a simple self-assembly technique of silica colloidal nanoparticles to create a nanofluidic junction between two microchannels in polydimethylsiloxane (PDMS). Using this technique, a nanoporous bead membrane with a pore size down to ~45 nm was built inside a microchannel and applied to electrokinetic preconcentration of DNA samples.

יצירת צומת תת-50 ננומטר ננו-נוזלי ב PDMS Microfluidic שבב באמצעות תהליך ההרכבה העצמית של חלקיקים קולואיד

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its ...

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous networks, ribbons, worm-like aggregates, toroidal structures, and spherical particles) is described. These aggregates are morphologically influenced by extensive hydrophobic side chain-side chain interactions of the singular polycarbodiimide strands, as inferred by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Polycarbodiimide-g-polystyrene copolymers (PS-PCDs) were prepared by a combination of synthetic methods, including coordination-insertion polymerization, copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) &#34;click&#34; chemistry, and atom transfer radical polymerization (ATRP). PS-PCDs were found to form specific toroidal architectures at low concentrations in CHCl3. To determine the influence of a more polar solvent medium (i.e., THF and THF/EtOH) on polymer aggregation behavior, a number of representative PS-PCD composites have been tested to show discrete concentration-dependent spherical particles. These fundamental studies are of practical interest to the development of experimental procedures for desirable architectures by directed self-assembly in thin film. These architectures may be exploited as drug carriers, whereas other morphological findings represent certain interest in the area of novel functional materials.

Here, we present a protocol to prepare and visualize secondary structures (e.g., fibers, toroidal architectures, and nano-spheres) derived from helical polycarbodiimides. The morphology characterized by both atomic force microscopy (AFM) and scanning electron microscopy (SEM) was shown to depend on molecular structure, concentration, and the solvent of choice.

מורפולוגיה הרכבה עצמיות המתקבלות סליל Polycarbodiimide קופולימרים ונגזר triazole שלהם

A facile method for the preparation of polycarbodiimide-based secondary structures (e.g., nano-rings, &#34;craters,&#34; fibers, looped fibers, fibrous ...

Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully understood. We have traced the trajectories of individual nanoparticles using liquid-cell transmission electron microscopy (TEM) to investigate the mechanism of the assembly process. Herein, we present the protocols used for liquid-cell TEM studies of the self-assembly mechanism. First, we introduce the detailed synthetic protocols used to produce uniformly sized platinum and lead selenide nanoparticles. Next, we present the microfabrication processes used to produce liquid cells with silicon nitride or silicon windows and then describe the loading and imaging procedures of the liquid-cell TEM technique. Several notes are included to provide helpful tips for the entire process, including how to manage the fragile cell windows. The individual motions of nanoparticles tracked by liquid-cell TEM revealed that changes in the solvent boundaries caused by evaporation affected the self-assembly process of nanoparticles. The solvent boundaries drove nanoparticles to primarily form amorphous aggregates, followed by flattening of the aggregates to produce a 2-dimensional (2D) self-assembled structure. These behaviors are also observed for different nanoparticle types and different liquid-cell compositions.

Here we introduce experimental protocols for the real-time observation of a self-assembly process using liquid-cell transmission electron microscopy.

במיקרוסקופ אלקטרונים הילוכים נוזלי-תא לצורך מעקב הרכבה עצמית של חלקיקים

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

We demonstrate the fabrication of periodic gold nanocup arrays using colloidal lithographic techniques and discuss the importance of nanoplasmonic films.

ייצור של מערכים Nanocup זהב תקופתיים באמצעות Colloidal ליתוגרפיה

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing ...

Ligand Nano-cluster Arrays in a Supported Lipid Bilayer

Currently there is considerable interest in creating ordered arrays of adhesive protein islands in a sea of passivated surface for cell biological studies. In the past years, it has become increasingly clear that living cells respond, not only to the biochemical nature of the molecules presented to them but also to the way these molecules are presented. Creating protein micro-patterns is therefore now standard in many biology laboratories; nano-patterns are also more accessible. However, in the context of cell-cell interactions, there is a need to pattern not only proteins but also lipid bilayers. Such dual proteo-lipidic patterning has so far not been easily accessible. We offer a facile technique to create protein nano-dots supported on glass and propose a method to backfill the inter-dot space with a supported lipid bilayer (SLB). From photo-bleaching of tracer fluorescent lipids included in the SLB, we demonstrate that the bilayer exhibits considerable in-plane fluidity. Functionalizing the protein dots with fluorescent groups allows us to image them and to show that they are ordered in a regular hexagonal lattice. The typical dot size is about 800 nm and the spacing demonstrated here is 2 microns. These substrates are expected to serve as useful platforms for cell adhesion, migration and mechano-sensing studies.

We present a protocol to functionalize glass with nanometric protein patches surrounded by a fluid lipid bilayer. These substrates are compatible with advanced optical microscopy and are expected to serve as platform for cell adhesion and migration studies.

מערכי ננו-אשכול ליגנד בתוך bilayer שומנים נתמך

Currently there is considerable interest in creating ordered arrays of adhesive protein islands in a sea of passivated surface for cell biological ...

Bioengineering

Fabrication of Zero Mode Waveguides for High Concentration Single Molecule Microscopy

In single molecule fluorescence enzymology, background fluorescence from labeled substrates in solution often limits fluorophore concentration to pico- to nanomolar ranges, several orders of magnitude less than many physiological ligand concentrations. Optical nanostructures called zero mode waveguides (ZMWs), which are 100&#8722;200 nm in diameter apertures fabricated in a thin conducting metal such as aluminum or gold, allow imaging of individual molecules at micromolar concentrations of fluorophores by confining visible light excitation to zeptoliter effective volumes. However, the need for expensive and specialized nanofabrication equipment has precluded the widespread use of ZMWs. Typically, nanostructures such as ZMWs are obtained by direct writing using electron beam lithography, which is sequential and slow. Here, colloidal, or nanosphere, lithography is used as an alternative strategy to create nanometer-scale masks for waveguide fabrication. This report describes the approach in detail, with practical considerations for each phase. The method allows thousands of aluminum or gold ZMWs to be made in parallel, with final waveguide diameters and depths of 100&#8722;200 nm. Only common lab equipment and a thermal evaporator for metal deposition are required. By making ZMWs more accessible to the biochemical community, this method can facilitate the study of molecular processes at cellular concentrations and rates.

Described here is a nanosphere lithography method for parallel fabrication of zero mode waveguides, which are arrays of nanoapertures in a metal-clad glass microscopy coverslip for single molecule imaging at nano- to micromolar concentrations of fluorophores. The method takes advantage of colloidal crystal self-assembly to create a waveguide template.

ייצור של מגלי גל במצב אפס למיקרוסקופיה של מולקולה בודדת בריכוז גבוה

In single molecule fluorescence enzymology, background fluorescence from labeled substrates in solution often limits fluorophore concentration to pico- to ...