real-time-monitoring-ligand-receptor-interactions-with-fluorescence

Real-time Monitoring of Ligand-receptor Interactions with Fluorescence Resonance Energy Transfer

FRET is a process  whereby energy is non-radiatively transferred from an excited donor molecule to  a ground-state acceptor molecule through long-range ...

Nanoparticles are being developed for a host of biomedical and biotechnological applications, including drug delivery, enzyme immobilization and DNA transfection. Spherical nanoparticles are typically used for such applications, which reflects the fact that spheres are easier to make than other shapes. Micro- and nanotubes--structures that resemble tiny drinking straws--are alternatives that might offer advantages over spherical nanoparticles for some applications. This article discusses four approaches for making micro- and nanotubes, and reviews the current status of efforts to develop biomedical and biotechnological applications of these tubular structures.

The emerging field of nanotube biotechnology.

Das neue Gebiet der Biotechnologie-Nanor&#xF6;hrchen.

Nanoparticles are being developed for a host of biomedical and biotechnological applications including drug delivery, enzyme immobilization and DNA transfection. Spherical nanoparticles are typically used for such applications, but this only reflects the fact that spheres are easier to make than other shapes. Micro- and nanotubes--structures that resemble tiny drinking straws--are alternatives and may offer advantages over spherical nanoparticles for some applications. This article discusses four different approaches to making micro- and nanotubes and reviews the current status of efforts to develop biomedical and biotechnological applications of these tubular structures.

Smart nanotubes for biomedical and biotechnological applications.

Smart-Nanor&#xF6;hren f&#xFC;r biomedizinische und biotechnologische Anwendungen.

Electroless deposition of gold on the pore walls of polycarbonate templates is currently the best known method for controlling inside diameters of template-synthesized nanotubes. It would be very useful to have alternative template-based synthetic chemistries that yield nanotubes composed of other materials, but which still allow for precise control over the nanotube wall thickness and i.d. A film-formation process that is based on layer-by-layer deposition of the film-forming material along the pore walls of the template membrane provides this desired alternative synthetic chemistry. We describe here the use of Mallouk's alpha,omega-diorganophosphonate/Zr layer-by-layer film-forming method for preparing nanotubes within the pores of alumina template membranes. We have found that this method allows accurate, quantitative, and predictable control over the wall thickness, and thus i.d., of the layered nanotubes obtained.

Layer-by-layer nanotube template synthesis.

Schicht-f&#xFC;r-Schicht-Nanor&#xF6;hrchen Templatsynthese.

We describe synthetic membranes in which the molecular recognition chemistry used to accomplish selective permeation is DNA hybridization. These membranes contain template-synthesized gold nanotubes with inside diameters of 12 nanometers, and a "transporter" DNA-hairpin molecule is attached to the inside walls of these nanotubes. These DNA-functionalized nanotube membranes selectively recognize and transport the DNA strand that is complementary to the transporter strand, relative to DNA strands that are not complementary to the transporter. Under optimal conditions, single-base mismatch transport selectivity can be obtained.

DNA-functionalized nanotube membranes with single-base mismatch selectivity.

DNA-funktionalisierten Nanor&#xF6;hren-Membranen mit Single-Basenfehlpaarung Selektivit&#xE4;t.

Ion channels are protein pores that span cell membranes and open and close in response to stimuli like changes in the transmembrane potential, binding of a ligand, or mechanical stress. When open, ions pass through the pore, and hence across the cell membrane, and when closed, ion-transport is precluded. Hence, these channels are nanodevices that have a current-rectification function. There is intense research effort aimed at understanding the molecular-level mechanism for this function. One approach for elucidating the mechanism is to construct a simple abiotic system that mimics this function and to use the mechanistic details of this mimic as a guide to understand the more complex biological channel. We describe here such an abiotic mimic: a synthetic membrane that contains a single conical gold nanotube. The advantage of this mimic is that the surface charge and chemistry of the nanotube wall can be varied, at will, by judicious choice of electrolyte or by thiol chemisorption. This has allowed us to make conical Au nanotubes that rectify the ion current and, just as importantly, to definitively elucidate the mechanism of this function.

Conical-nanotube ion-current rectifiers: the role of surface charge.

Konische-Nanotube-Ionen-Stromrichter: die Rolle der Oberfl&#xE4;chenladung.

Nanotube-containing membranes prepared by the template method show promise for use as highly selective filters for membrane-based chemical and biological separations. Most of the work to date has been done on gold nanotubes prepared by electroless deposition of Au within the pores of polymeric filtration membranes. These polymeric filters have very low porosities (< 1%), and, as a result, the flux through Au nanotube membranes based on these templates is very low. In contrast, the other popular template membranes-anodic aluminas-have high porosities-30% to 50%. In spite of this potential advantage of anodic alumina templates, there have been no reports of electrolessly plated Au nanotubes within the pores of these templates. This is because the electroless plating method used to deposit Au nanotubes in polymeric templates does not work in aluminas. We have developed a modified electroless plating strategy that can be used to deposit high-quality Au nanotubes within the pores of the alumina templates. We describe this new plating method here.

Template synthesis of gold nanotubes in an anodic alumina membrane.

Template-Synthese von Gold-Nanor&#xF6;hrchen in einer anodischen Aluminiumoxid-Membran.

There is considerable interest in developing chemical devices that mimic the function of biological ion channels. We recently described such a device, which consisted of a single conically shaped gold nanotube embedded within a polymeric membrane. This device mimicked one of the key functions of voltage-gated ion channels: the ability to strongly rectify the ionic current flowing through it. The data obtained were interpreted using a simple electrostatic model. While the details are still being debated, it is clear that ion-current-rectification in biological ion channels is more complicated and involves physical movement of an ionically charged portion of the channel in response to a change in the transmembrane potential. We report here artificial ion channels that rectify the ion current flowing through them via this "electromechanical" mechanism. These artificial channels are also based on conical gold nanotubes, but with the critical electromechanical response provided by single-stranded DNA molecules attached to the nanotube walls.

DNA-nanotube artificial ion channels.

DNA-Nanor&#xF6;hrchen k&#xFC;nstliche Ionenkan&#xE4;le.

Nanotechnology concerns the science of very small particles and deals with both the fundamental aspects of understanding the properties of such nanoparticles and with developing technological applications of nanoparticles. Biomedical and biotechnological applications of nanoparticles have been of special recent research and development interest, with potential applications that include use of nanoparticles as drug (or DNA) delivery vehicles, and as components in medical diagnostic kits, biosensors and membranes for bioseparations. Spherical nanoparticles are typically used for such applications, but this only reflects the fact that spheres are easier to make than nanoparticles having other shapes. Micro and nanotubes - structures that resemble tiny drinking straws - are alternatives and may offer advantages over spherical nanoparticles for some applications. This article discusses different approaches for making micro and nanotubes and reviews the current status of efforts to develop biomedical and biotechnological applications of these tubular structures.

Smart nanotubes for biotechnology.

Smart-Nanor&#xF6;hrchen f&#xFC;r die Biotechnologie.

There is increasing interest in the concept of using nanopores as the sensing elements in biosensors. The nanopore most often used is the alpha-hemolysin protein channel, and the sensor consists of a single channel embedded within a lipid bilayer membrane. An ionic current is passed through the channel, and analyte species are detected as transient blocks in this current associated with translocation of the analyte through the channel-stochastic sensing. While this is an extremely promising sensing paradigm, it would be advantageous to eliminate the very fragile lipid bilayer membrane and perhaps to replace the biological nanopore with an abiotic equivalent. We describe here a new family of protein biosensors that are based on conically shaped gold nanotubes embedded within a mechanical and chemically robust polymeric membrane. While these sensors also function by passing an ion current through the nanotube, the sensing paradigm is different from the previous devices in that a transient change in the current is not observed. Instead, the protein analyte binds to a biochemical molecular-recognition agent at the mouth of the conical nanotube, resulting in complete blockage of the ion current. Three different molecular-recognition agents, and correspondingly three different protein analytes, were investigated: (i) biotin/streptavidin, (ii) protein-G/immunoglobulin, and (iii) an antibody to the protein ricin with ricin as the analyte.

Protein biosensors based on biofunctionalized conical gold nanotubes.

Protein-Biosensoren auf biofunktionalisierten konische Gold Basis von Nanor&#xF6;hren.

We report here a novel system where the rate of energy transfer is based on changes in the spectral overlap between the emission of the donor and the absorption of the acceptor (J) as well as changes in the quantum yield of the acceptor. We use the fluorophore dansyl as the donor and polydiacetylene (PDA) as the acceptor to demonstrate the modulation of FRET through conformationally induced changes in the PDA absorption spectrum following thermal treatment that converts the PDA backbone of the liposome from the blue form to the red form. Energy transfer was found to be significantly more efficient from dansyl to the red-form PDA. These findings support the basis of a new sensing platform that utilizes J-modulated FRET as an actuating mechanism.

Modulating fluorescence resonance energy transfer in conjugated liposomes.

Wir berichten hier ein neuartiges System, wo die Rate der Energie&uuml;bertragung auf &Auml;nderungen in der spektrale &Uuml;berlappung zwischen der Emission des Spenders und der Absorption von der Akzeptor (J) sowie Ver&auml;nderungen in der Quantenausbeute der Akzeptor basiert. Wir verwenden das Fluorophor Dansyl als Spender und Polydiacetylene (PDA) als Akzeptor demonstrieren die Modulation der Bund durch konformationsgehinderten verursachten &Auml;nderungen in der PDA-Absorptionsspektrum nach der thermischen Behandlung, die das R&uuml;ckgrat der Liposomen PDA aus dem blauen Formular in die rote Form konvertiert. Energie&uuml;bertragung wurde deutlich effizienter aus Dansyl auf den PDA rot-Form gefunden. Diese Ergebnisse unterst&uuml;tzen die Grundlage einer neuen Sensor-Plattform, die J-modulierte FRET als ein Stellantrieb nutzt.

Modulierenden Fluoreszenz-Resonanz-Energie-Transfer in konjugierten Liposomen.

Electroactive nanotube membranes and redox-gating.

Elektroaktive Nanotube Membranen und Redox-gating.

Conjugated polydiacetylene (PDA) possessing stimuli-responsive properties has been intensively investigated for developing efficient sensors. We report here fluorescence resonance energy transfer (FRET) in liposomes synthesized using different molar ratios of dansyl-tagged diacetylene and diacetylene-carboxylic acid monomers. Photopolymerization of diacetylene resulted in cross-linked PDA liposomes. We used steady-state electronic absorption, emission, and fluorescence anisotropy (FA) analysis to characterize the thermal-induced FRET between dansyl fluorophores (donor) and PDA (acceptor). We found that the monomer ratio of acceptor to donor ( R ad) and length of linkers (functional part that connects dansyl fluorophores to the diacetylene group in the monomer) strongly affected FRET. For R ad = 10 000, the acceptor emission intensity was amplified by more than 18 times when the liposome solution was heated from 298 to 338 K. A decrease in R ad resulted in diminished acceptor emission amplification. This was primarily attributed to lower FRET efficiency between donors and acceptors and a higher background signal. We also found that the FRET amplification of PDA emissions after heating the solution was much higher when dansyl was linked to diacetylene through longer and flexible linkers than through shorter linkers. We attributed this to insertion of dansyl in the bilayer of the liposomes, which led to an increased dansyl quantum yield and a higher interaction of multiple acceptors with limited available donors. This was not the case for shorter and more rigid linkers where PDA amplification was much smaller. The present studies aim at enhancing our understanding of FRET between fluorophores and PDA-based conjugated liposomes. Furthermore, receptor tagged onto PDA liposomes can interact with ligands present on proteins, enzymes, and cells, which will produce emission sensing signal. Therefore, using the present approach, there exist opportunities for designing FRET-based highly sensitive and selective chemical and biochemical sensors.

Fluorescence resonance energy transfer in polydiacetylene liposomes.

Konjugierte Polydiacetylene (PDA) Reize-responsive Eigenschaften aufweisen ist intensiv untersucht worden, f&uuml;r die Entwicklung von effizienter Sensors. Wir berichten hier Fluoreszenz Resonanz Energietransfer (FRET) in Liposomen, die mit unterschiedlichen molaren Verh&auml;ltnisse Diacetylen Dansyl markiert und Diacetylen-carboxylic saure Monomere synthetisiert. Photopolymerisation von Diacetylen f&uuml;hrte querverbundenen PDA-Liposomen. Wir haben station&auml;ren elektronische Absorption, Emission und Fluoreszenz Anisotropie (FA) Analyse der Thermal-induzierte FRET zwischen Dansyl Fluorophore (Spender) und PDA (Akzeptor) charakterisieren. Wir fanden, dass das Monomer-Verh&auml;ltnis der Akzeptor Spender (R n. Chr.) und die L&auml;nge der Linker (funktionale Teil, die Dansyl Fluorophore der Diacetylen-Gruppe in das Monomer verbindet) stark beeinflusst FRET. F&uuml;r R Ad = 10 000, die Emissionsintensit&auml;t der Akzeptor wurde durch mehr als 18 Mal wann die Liposomen-L&ouml;sung von 298 338 K. erhitzt wurde verst&auml;rkt Eine Abnahme der R Anzeige ergab verminderte Akzeptor-Emission-Verst&auml;rkung. Dies war vor allem niedrigere FRET-Effizienz zwischen Spender und Acceptors und eine h&ouml;here Hintergrundsignal zugeschrieben. Wir fanden, die auch die Bund-Verst&auml;rkung der PDA-Emissionen nach Heizung die L&ouml;sung war viel h&ouml;her, wenn Dansyl Diacetylen durch l&auml;ngere und flexible Linker als durch k&uuml;rzere Verkn&uuml;pfungsprogramme verkn&uuml;pft war. Wir zugeschrieben das Einf&uuml;gen von Dansyl in der Bilayer der Liposomen, die zu einer erh&ouml;hten Dansyl Quantenausbeute und eine h&ouml;here Interaktion von mehreren Acceptors mit begrenzt verf&uuml;gbar Spendern gef&uuml;hrt. Dies war nicht der Fall f&uuml;r k&uuml;rzere und steifere Verkn&uuml;pfungsprogramme wo PDA Verst&auml;rkung viel kleiner war. Die vorliegenden Studien Zielen auf unser Verst&auml;ndnis der Bund zwischen Fluorophore und PDA-basierte konjugierte Liposomen. Dar&uuml;ber hinaus kann Rezeptor markiert auf PDA Liposomen interagieren mit Liganden auf Proteine, Enzyme und Zellen, die Emission Sensorik Signal produzieren wird. Daher verwenden das derzeitige Konzept, gibt es M&ouml;glichkeiten f&uuml;r die Gestaltung von FRET-hochempfindliche und selektiver chemischer und biochemische Sensors.

Fluoreszenz-Resonanz-Energie-Transfer in Polydiacetylene Liposomen.

We report here the synthesis and characterization of polydiacetylene (PDA) films and nanotubes using layer-by-layer (LBL) chemistry. 10,12-Docosadiyndioic acid (DCDA) monomer was self-assembled on flat surfaces and inside of nanoporous alumina templates. UV irradiation of DCDA provided polymerized-DCDA (PDCDA) films and nanotubes. We have used zirconium-carboxylate interlayer chemistry to synthesize PDCDA multilayers on flat surfaces and in nanoporous template. PDCDA multilayers were characterized using optical (UV-vis, fluorescence, ellipsometry, FTIR) spectroscopies, ionic current-voltage ( I- V) analysis, and scanning electron microscopy. Ellipsometry, FTIR, electronic absorption and emission spectroscopies showed a uniform DCDA deposition at each deposition cycle. Our optical spectroscopic analysis indicates that carboxylate-zirconium interlinking chemistry is robust. To explain the disorganization in the alkyl portion of PDCDA multilayer films, we propose carboxylate-zirconium interlinkages act as "locks" in between PDCDA layers which restrict the movement of alkyl portion in the films. Because of this locking, the induced-stresses in the polymer chains can not be efficiently relieved. Our ionic resistance data from I- V analysis correlate well with calculated resistance at smaller number of PDCDA layers but significantly deviated for thicker PDCDA nanotubes. These differences were attributed to ion-blocking because some of the PDCDA nanotubes were totally closed and the nonohmic and permselective ionic behaviors when the diameter of the pores approaches the double-layer thickness of the solution inside of the nanotubes.

Synthesis and characterization of polydiacetylene films and nanotubes.

Wir berichten hier die Synthese und Charakterisierung von Polydiacetylene (PDA)-Filme und Nanor&ouml;hren mit Schicht-f&uuml;r-Schicht (LBL) Chemie. 10,12-Docosadiyndioic S&auml;ure (DCDA) Monomer war monomolekularen auf flachen Oberfl&auml;chen und innerhalb nanopor&ouml;se Tonerde Vorlagen. UV-Bestrahlung von DCDA zur Verf&uuml;gung gestellt (PDCDA) polymerisiert-DCDA Filme und Nanor&ouml;hren. Wir haben Zirkonium-carboxylat Zwischenschicht Chemie benutzt, PDCDA Multischichten auf flachen Oberfl&auml;chen und in nanopor&ouml;sen Vorlage zu synthetisieren. PDCDA Multischichten zeichneten sich mit optischen (UV-Vis, Fluoreszenz, Ellipsometry, FTIR) SPEKTROSKOPIEN, Ionische Strom-Spannungs (I-V)-Analyse und Rasterelektronenmikroskopie. Ellipsometry, FTIR, elektronischen Absorption und Emission SPEKTROSKOPIEN zeigte eine einheitliche DCDA-Abscheidung bei jeder Ablagerung. Unsere optische Spektralanalyse zeigt, dass carboxylat-Zirkonium interlinking Chemie robust ist. Um die Desorganisation in der Alkyl-Teil des PDCDA-Mehrschichtfolien erkl&auml;ren, schlagen wir vor, dass zwischen PDCDA Schichten carboxylat-Zirkonium-Wechselbeziehungen als &quot;Locks&quot; handeln, die die Bewegung des Alkyl-Teils in den Filmen beschr&auml;nken. Wegen dieser Sperren, k&ouml;nnen die induzierten Spannungen in die Polymerketten nicht effizient entlastet werden. Unsere Ionische Resistenzdaten-V Analyse korrelieren gut mit berechneten Widerstand bei kleineren Anzahl PDCDA lagen aber f&uuml;r dickere PDCDA Nanotubes erheblich abwichen. Diese Unterschiede wurden Ionen blockieren, denn einige der PDCDA Nanotubes v&ouml;llig geschlossenen und die nonohmic und Permselective Ionischen Verhaltensweisen zugeschrieben, wenn der Durchmesser der Poren die Doppelschicht-Dicke der L&ouml;sung innerhalb der Nanotubes n&auml;hert.

Synthese und Charakterisierung von Polydiacetylene Filmen und Nanor&ouml;hren.

In this study, we demonstrate a facile and simple synthesis of quantum dot (QD)-polymer composites. Highly fluorescent semiconducting CdSe/ZnS quantum dots were embedded in different commercially available polymers using one easy step. QD-polymer composite nanoparticles were also synthesized using template-assisted synthesis. In particular, we self-assembled lamellar micelles inside nanoporous alumina membranes which were used for the synthesis of mesoporous silica hollow nanotubes and solid nanorods. We observed that the addition of excess free octadecylamine (ODA) in the QD-silica solution resulted in gelation. The gelation time was found to be dependent on free ODA concentration. Similarly, the emission of QD-polymer composites was also found to be dependent on free ODA concentration. Highly purified QDs provided polymer composites that have a much lower emission compared to unpurified nanocomposites. This was attributed to passivation of the QD surfaces by amine, which reduced the surface defects and non-radiative pathways for excited QDs. Finally, highly fluorescent QD-polymer patterns were demonstrated on glass substrates which retained their emission in both polar and non-polar solvents.

Synthesis and characterization of quantum dot-polymer composites.

In dieser Studie zeigen wir eine einfache und einfache Synthese von Quantenpunkt (QD)-Polymer-Kompositen. Stark fluoreszierende halbleitenden CdSe/ZnS-Quantenpunkte wurden in verschiedenen handels&uuml;blichen Polymere mit einem einfachen Schritt eingebettet. QD-Polymer zusammengesetzte Nanopartikel wurden auch synthetisiert, welche Vorlage-assistierte-Synthese. Insbesondere assembled wir lamell&auml;re Mizellen innen nanopor&ouml;se Tonerde-Membranen, die verwendet wurden, f&uuml;r die Synthese von Mesopor&ouml;se Kiesels&auml;ure hohlen Nanor&ouml;hren und solide hergestellt. Wir beobachteten, dass die Zugabe von &uuml;bersch&uuml;ssigen freien Octadecylamine (ODA) der QD-Kiesels&auml;ure-L&ouml;sung Gelbildung gef&uuml;hrt. Die Gelbildung Zeit wurde festgestellt, dass freie ODA-Konzentration abh&auml;ngig sein. Ebenso wurde die Emission von QD-Polymer Composites auch gefunden, um kostenlose ODA-Konzentration abh&auml;ngig zu sein. Hoch gereinigten QDs bereitgestellten Polymer-Verbundwerkstoffen, die eine viel geringere Emission im Vergleich zu ungereinigtem Nanocomposites haben. Dies war Passivierung der QD-Oberfl&auml;chen von Amin, zugeordnet, die Oberfl&auml;chenst&ouml;rungen und nichtstrahlenden Wege f&uuml;r aufgeregt QDs reduziert. Schlie&szlig;lich wurden stark fluoreszierende QD-Polymer-Muster auf Glassubstraten demonstriert, die ihre Emissionen in sowohl polaren und unpolaren L&ouml;sungsmitteln aufbewahrt.

Synthese und Charakterisierung von Quantum Dot-Polymer Composites.

Solid lubricants (SLs) characterized by low coefficients of friction (mu) and wear rates (w) drastically improve the life span of instruments that undergo extreme frictional wear. However, the performance of SLs such as sputtered or nanoparticulate molybdenum disulfide (MoS(2)), tungsten disulfide (WS(2)), or graphite deteriorates heavily under extreme operational conditions such as elevated temperatures and high humidity. Here, we present our preliminary results, which demonstrate that composites of carbon nanotubes (CNTs) and MoS(2) produced by electrodeposition of MoS(2) on vertically aligned CNT films have low mu ( approximately 0.03) and w (approximately 10(-13) mm(3)/N.mm) even at 300 degrees C, which are about 2 orders of magnitude better than those of nanoparticulate MoS(2)-based coatings. The high load-bearing capacity of CNTs provides a strong enduring support to MoS(2) nanoclusters and is responsible for their ultralow w. The incorporation of these composites in liquid lubricants reduces the friction coefficient of the liquid lubricants by approximately 15%. The technique described here to produce SL coatings with extremely appealing frictional properties will provide valuable solutions for a variety of tribological applications where the coatings encounter high temperature, reduced pressure, and/or low- and high-humidity conditions.

Carbon nanotube-MoS2 composites as solid lubricants.

Festschmierstoffe (SLs) zeichnet sich durch geringe Koeffizienten von Reibung (Mu) und Verschlei&szlig; Preise (w) drastisch erh&ouml;hen die Lebensdauer der Instrumente, die extreme kraftschl&uuml;ssigen Verschlei&szlig; unterzogen werden. Jedoch die Leistung von SLs wie zuckten oder nanopartikul&auml;ren Molybd&auml;ndisulfid (MoS(2)), Wolfram-sulfid (WS(2)) oder Graphit verschlechtert stark unter extremen Einsatzbedingungen wie hohen Temperaturen und hoher Luftfeuchtigkeit. Hier pr&auml;sentieren wir unsere vorl&auml;ufige Ergebnisse, die zeigen, dass die Zusammensetzungen von Kohlenstoff-Nanor&ouml;hren (CNT) und MoS(2) von Electrodeposition von MoS(2) auf vertikal ausgerichteten Filme produziert haben niedrige Mu (ca. 0,03) und w (etwa 10(-13) mm(3)/N.mm) auch bei 300 Grad C, die etwa 2 Gr&ouml;&szlig;enordnungen besser als die der nanopartikul&auml;ren MoS (2) sind-basierten Beschichtungen. Die hohe Tragf&auml;higkeit der CNTs gew&auml;hrt eine starke dauerhafte Unterst&uuml;tzung MoS(2) Nanoclustern und ist verantwortlich f&uuml;r ihre Weise w. Die Einbeziehung dieser Composites in fl&uuml;ssigen Schmierstoffen reduziert die Reibungszahl der fl&uuml;ssige Schmierstoffe um ca. 15 %. Die hier beschriebene SL-Lacke mit sehr ansprechenden Reibungseigenschaften produzieren Technik bieten wertvolle L&ouml;sungen f&uuml;r eine Vielzahl von tribologische Anwendungen, wo die Beschichtungen Hochtemperatur, vermindertem Druck und/oder niedriger und hoher Luftfeuchtigkeit auftreten.

Kohlenstoff-Nanor&ouml;hrchen-MoS2-Verbundwerkstoffen als Festschmierstoffe.

We demonstrate conical pores etched in tracked glass chips for fabricating patterns at the micrometer scale. Highly fluorescent patterns based on photopolymerization of diacetylene films were formed by irradiating UV light through conical pores called "photo-pens". The properties of photopens were investigated through experiments, finite-difference-time-domain (FDTD) simulations and numerical calculations based on Fresnel equations. We show that the pattern dimensions are easily controlled by adjusting the exposure time. Thus, patterns with a range of dimensions can be fabricated without any need of changes in the pore diameter. Parallel patterning was also demonstrated by simultaneously exposing the films to photons through multiple pores in the chip. Our method provides an inexpensive, versatile, and efficient way for patterning without the use of sophisticated masks.

Photo-pens: a simple and versatile tool for maskless photolithography.

Wir demonstrieren die konische Poren ge&auml;tzt nachverfolgten Glas-Chips f&uuml;r die Herstellung von Mustern an der Mikrometer-Skala. Stark fluoreszierende Muster auf der Grundlage von Photopolymerisation Diacetylen Filme wurden durch Bestrahlung von UV-Licht durch konischen Poren genannt &quot;Foto-Stifte&quot; gebildet. Die Eigenschaften des Photopens wurden durch Experimente, endliche-Unterschied-Zeit-Domain (FDTD) Simulationen und numerische Berechnungen basierend auf Fresnel Gleichungen untersucht. Wir zeigen, dass die Musterbema&szlig;ungen leicht gesteuert werden, durch die Anpassung der Belichtungszeit. So k&ouml;nnen Muster mit einer Reihe von Dimensionen ohne jegliche &Auml;nderungen in der Porendurchmesser hergestellt werden. Parallele Musterung wurde auch gezeigt, indem man gleichzeitig die Filme Photonen durch mehrere Poren im Chip. Unsere Methode bietet eine preiswerte, vielseitige und effiziente M&ouml;glichkeit f&uuml;r Musterung ohne den Einsatz von hoch entwickelten Masken.

Foto-Kugelschreiber: ein einfaches und vielseitige Werkzeug f&uuml;r maskenlosen Fotolithografie.

In this study, we investigate photophysical and photoinduced current responses of a nanocomposite which consists of multiwalled carbon nanotubes (CNTs), thiol derivative perylene compound (ETPTCDI), and cadmium selenide quantum dots (QDs). These QDs as well as the ETPTCDI harvest photons and transfer their excited electrons or holes to CNTs to complete the circuit. Both QDs and ETPTCDI contribute charges to the carbon nanotubes, which increased the overall photon harvest efficiency of the nanocomposite. Herein, we investigate through a series of photophysical photoluminescence quenching studies the charge transfer between donors (QDs and ETPTCDI) and acceptor (CNTs). The incorporation of ETPTCDI into the nanocomposite significantly increases the adhesion between QDs and CNTs through bonding between QDs and thiol groups on ETPTCDI and Ï€-Ï€ interactions between ETPTCDI and CNTs. Thus, ETPTCDI acted as a molecular linker between QDs and CNTs. Furthermore, a significant increase (>5 times) in the Stern-Volmer constant, K(sv), for QD emission after addition of ETPTCDI-tagged CNTs clearly indicates a large enhancement in the adhesion between CNTs and QDs. The nanocomposite shows a âˆ¼2-4-fold increase in the photoconductivity when exposed to AM1.5 solar-simulated light. The damage to the nanocomposite from the intensity of the solar-simulated light is also investigated. The proposed nanocomposite has the potential for photovoltaic applications such as being the active component in a hybrid bulk heterojunction solar cell.

Investigating photoinduced charge transfer in carbon nanotube-perylene-quantum dot hybrid nanocomposites.

In dieser Studie untersuchen wir photophysikalische und photoinduzierte aktuelle Antworten von einem Nanocomposite Multiwalled Carbon nanotubes (CNTs) besteht, Thiol Derivative perylen zusammengesetzte (ETPTCDI) und Cadmium Selenid Quantum dots (QDs). Diese QDs sowie die ETPTCDI Ernte Photonen und &uuml;bertragen ihre aufgeregt Elektronen oder L&ouml;cher bis CNTs um die Schaltung zu vervollst&auml;ndigen. QDs und ETPTCDI beitragen, Geb&uuml;hren f&uuml;r die Kohlenstoff-Nanor&ouml;hrchen, die die Photon Ernte Gesamteffizienz der Nanocomposite erh&ouml;ht. Hier untersuchen wir durch eine Reihe von photophysikalische Photolumineszenz abschrecken Studien, die die Ladung zwischen Geber (QDs und ETPTCDI) und Akzeptor (CNTs) &uuml;bertragen. Die Einbeziehung der ETPTCDI in die Nanocomposite erh&ouml;ht signifikant die Adh&auml;sion zwischen QDs und CNTs durch Verklebung zwischen QDs und Thiol-Gruppen ETPTCDI und &pi;-&pi;-Wechselwirkungen zwischen ETPTCDI und CNTs. Aus diesem Grund agierte ETPTCDI als eine molekulare Linker QDs bis CNTs. Dar&uuml;ber hinaus eine deutliche Steigerung (&gt; 5 mal) in der Stern-Volmer-Konstante, K(sv), f&uuml;r QD-Emission nach Zusatz von CNTs ETPTCDI markiert eindeutig eine gro&szlig;e Verbesserung in der Haftung zwischen der CNT und QDs anzeigt. Die Nanocomposite zeigt ein &sim;2-4-fach in der Photoconductivity beim AM1. 5 solar simulierten Licht ausgesetzt. Die Sch&auml;den an den Nanocomposite von der Intensit&auml;t des Lichts solar simuliert wird ebenfalls untersucht. Die vorgeschlagenen Nanocomposite hat das Potenzial f&uuml;r Photovoltaik-Anwendungen befindet sich z. B. der aktiven Komponente in eine hybride Bulk Heterojunction-Solarzelle.

Bearbeitende photoinduzierten Charge Transfer in Carbon Nanotube-perylen-Quantenpunkt Hybrid Nanocomposites.

An ultracompact plasmonic beam splitter is theoretically and numerically investigated. The splitter consists of a V-shaped nanoslit in metal films. Two groups of nanoscale metallic grooves inside the slit (A) and at the small slit opening (B) are investigated. We show that there are two energy channels guiding light out by the splitter: the optical and the plasmonic channels. Groove A is used to couple incident light into the plasmonic channel. Groove B functions as a plasmonic scatter. We demonstrate that the energy transfer through plasmonic path is dominant in the beam splitter. We find that more than four times the energy is transferred by the plasmonic channel using structures A and B. We show that the plasmonic waves scattered by B can be converted into light waves. These light waves redistribute the transmitted energy through interference with the field transmitted from the nanoslit. Therefore, different beam splitting effects are achieved by simply changing the interference conditions between the scattered waves and the transmitted waves. The impact of the width and height of groove B are also investigated. It is found that the plasmonic scattering of B is changed into light scattering with increase of the width and the height of B. These devices have potential applications in optical sampling, signal processing, and integrated optical circuits.

Ultracompact beam splitters based on plasmonic nanoslits.

Eine ultrakompakte plasmonic Strahlteiler ist theoretisch und numerisch untersucht. Der Splitter besteht aus einem v-f&ouml;rmigen Nanoslit in Metallschichten. Zwei Gruppen von Nanoscale metallische Rillen in den Schlitz (A) und bei der Er&ouml;ffnung des kleinen Schlitz (B) werden untersucht. Wir zeigen, dass es zwei Energiekan&auml;le, die F&uuml;hrung von Licht durch die Splitter: die optische und die plasmonic Kan&auml;le. Nut A wird verwendet, um einfallendes Licht in den plasmonic Kanal zu koppeln. Nut B fungiert als ein plasmonic Scatter. Wir zeigen, dass die Energie&uuml;bertragung &uuml;ber plasmonic-Pfad in der Strahlteiler dominant ist. Wir finden, dass mehr als vier Mal die Energie &uuml;bertragen wird, vom plasmonic Channel mit Strukturen A und B. Wir zeigen, dass die plasmonic Wellen von B gestreut in Lichtwellen umgewandelt werden k&ouml;nnen. Diese Lichtwellen verteilen die &uuml;bertragene Energie durch Eingriff in das Feld von der Nanoslit &uuml;bertragen. Daher sind unterschiedliche Balken aufteilen Effekte erzielt, indem Sie einfach die Interferenz-Bedingungen zwischen den verstreuten Wellen und die &uuml;bertragenen Wellen. Die Auswirkungen der Breite und H&ouml;he von Groove B, wird ebenfalls untersucht. Es wird festgestellt, dass die plasmonic Streuung von B ins Licht Streuung mit Zunahme der Breite und der H&ouml;he von B. ge&auml;ndert wird Diese Ger&auml;te haben potentielle Anwendungen in optische Abtastung, Signalverarbeitung und integrierte optische Schaltungen.

Ultrakompakte Strahlteiler basierend auf plasmonic Nanoslits.

We investigate interactions between receptors and ligands at bilayer surface of polydiacetylene (PDA) liposomal nanoparticles using changes in electronic absorption spectroscopy and fluorescence resonance energy transfer (FRET). We study the effect of mode of linkage (covalent versus noncovalent) between the receptor and liposome bilayer. We also examine the effect of size-dependent interactions between liposome and analyte through electronic absorption and FRET responses. Glucose (receptor) molecules were either covalently or noncovalently attached at the bilayer of nanoparticles, and they provided selectivity for molecular interactions between glucose and glycoprotein ligands of E. coli. These interactions induced stress on conjugated PDA chain which resulted in changes (blue to red) in the absorption spectrum of PDA. The changes in electronic absorbance also led to changes in FRET efficiency between conjugated PDA chains (acceptor) and fluorophores (Sulphorhodamine-101) (donor) attached to the bilayer surface. Interestingly, we did not find significant differences in UV-vis and FRET responses for covalently and noncovalently bound glucose to liposomes following their interactions with E. coli. We attributed these results to close proximity of glucose receptor molecules to the liposome bilayer surface such that induced stress were similar in both the cases. We also found that PDA emission from direct excitation mechanism was âˆ¼2-10 times larger than that of the FRET-based response. These differences in emission signals were attributed to three major reasons: nonspecific interactions between E. coli and liposomes, size differences between analyte and liposomes, and a much higher PDA concentration with respect to sulforhodamine (SR-101). We have proposed a model to explain our experimental observations. Our fundamental studies reported here will help in enhancing our knowledge regarding interactions involved between soft particles at molecular levels.

Investigating Ligand-Receptor Interactions at Bilayer Surface Using Electronic Absorption Spectroscopy and Fluorescence Resonance Energy Transfer.

Wir untersuchen die Wechselwirkungen zwischen Rezeptoren und Liganden an Bilayer Oberfl&auml;che des Polydiacetylene (PDA) liposomalen Nanopartikel mit &Auml;nderungen im elektronischen Resorption Spektroskopie und Fluoreszenz Resonanz Energietransfer (FRET). Wir untersuchen die Auswirkungen der Art der Verbindung, die zwischen den Rezeptor und Liposomen Bilayer (kovalente gegen&uuml;ber). Wir untersuchen auch das gr&ouml;&szlig;enabh&auml;ngigen Wechselwirkungen zwischen Liposomen und Analyten durch elektronische Absorption und FRET Antworten. Glukose (Rezeptor) Molek&uuml;le wurden entweder kovalent oder noncovalently angebracht, an der Bilayer von Nanopartikeln und sie Selektivit&auml;t f&uuml;r Molekulare Wechselwirkungen zwischen Glukose und Glykoprotein Liganden von E. Coli. Diese Interaktionen induzierten Stress auf konjugierte PDA-Kette, die &Auml;nderungen (blau, rot) in das Absorptionsspektrum des PDA gef&uuml;hrt. Die &Auml;nderungen im elektronischen Absorption f&uuml;hrte auch zu &Auml;nderungen in FRET-Effizienz zwischen konjugierten PDA Ketten (Akzeptor) und Fluorophore (Sulphorhodamine-101) (Spender) an der Oberfl&auml;che Bilayer angeschlossen. Interessanterweise fand wir nicht signifikante Unterschiede im UV-Vis und FRET Antworten f&uuml;r noncovalently und kovalent gebundene Glucose zu Liposomen, die nach ihrer Interaktionen mit E. Coli. Wir zugeschrieben diese Ergebnisse um N&auml;he Glukose Rezeptor Molek&uuml;le zu den Liposomen Bilayer Oberfl&auml;che zu schlie&szlig;en, so dass die induzierte Spannung waren in beiden F&auml;llen &auml;hnlich. Wir fanden auch, dass PDA-Emission aus direkte Anregung Mechanismus &sim;2-10-mal gr&ouml;&szlig;er als die der FRET-basierten Antwort war. Diese Unterschiede in der Emission Signale wurden drei Gr&uuml;nden zugeschrieben: unspezifische Interaktionen zwischen Escherichia Coli und Liposomen, Gr&ouml;&szlig;enunterschiede zwischen Analyt und Liposomen und eine viel h&ouml;here Konzentration der PDA mit Bezug auf Sulforhodamin (SR-101). Wir haben ein Modell, um unsere experimentellen Beobachtungen erkl&auml;ren vorgeschlagen. Unsere grundlegenden Studien berichtet hier hilft bei der Verbesserung unseres Wissens &uuml;ber Interaktionen, die zwischen weichen Teilchen auf molekularer Ebene beteiligt.

Ligand-Rezeptor-Interaktionen auf Bilayer Oberfl&auml;che mit elektronischen Absorptionsspektroskopie und Fluoreszenz-Resonanz-Energie-Transfer untersucht.

Article	Year
The emerging field of nanotube biotechnology. Nature reviews. Drug discovery\| PubMed ID: 12509757	2003
Smart nanotubes for biomedical and biotechnological applications. Drug news & perspectives\| PubMed ID: 14702137	2003
Layer-by-layer nanotube template synthesis. Journal of the American Chemical Society\| PubMed ID: 15125653	2004
DNA-functionalized nanotube membranes with single-base mismatch selectivity. Science (New York, N.Y.)\| PubMed ID: 15310896	2004
Conical-nanotube ion-current rectifiers: the role of surface charge. Journal of the American Chemical Society\| PubMed ID: 15339163	2004
Template synthesis of gold nanotubes in an anodic alumina membrane. Journal of nanoscience and nanotechnology\| PubMed ID: 15518394	2004
DNA-nanotube artificial ion channels. Journal of the American Chemical Society\| PubMed ID: 15571378	2004
Smart nanotubes for biotechnology. Current pharmaceutical biotechnology\| PubMed ID: 15727554	2005
Protein biosensors based on biofunctionalized conical gold nanotubes. Journal of the American Chemical Society\| PubMed ID: 15810817	2005
Modulating fluorescence resonance energy transfer in conjugated liposomes. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 17014092	2006
Electroactive nanotube membranes and redox-gating. Small (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 17191302	2007
Fluorescence resonance energy transfer in polydiacetylene liposomes. The journal of physical chemistry. B\| PubMed ID: 18816092	2008
Synthesis and characterization of polydiacetylene films and nanotubes. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 18823090	2008
Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 18946047	2008
Synthesis and characterization of quantum dot-polymer composites. Journal of materials chemistry\| PubMed ID: 19936033	2009
Carbon nanotube-MoS2 composites as solid lubricants. ACS applied materials & interfaces\| PubMed ID: 20355996	2009
Photo-pens: a simple and versatile tool for maskless photolithography. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 20886901	2010
Investigating photoinduced charge transfer in carbon nanotube-perylene-quantum dot hybrid nanocomposites. ACS nano\| PubMed ID: 20945933	2010
Ultracompact beam splitters based on plasmonic nanoslits. Journal of applied physics\| PubMed ID: 21647248	2011
Investigating Ligand-Receptor Interactions at Bilayer Surface Using Electronic Absorption Spectroscopy and Fluorescence Resonance Energy Transfer. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 22734511	2012

Punit Kohli

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