National Nanotechnology Research Center


National Nanotechnology Research Center

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Beyazkilic P.,National Nanotechnology Research Center | Beyazkilic P.,Institute of Materials Science and Nanotechnology | Tuvshindorj U.,National Nanotechnology Research Center | Tuvshindorj U.,Institute of Materials Science and Nanotechnology | And 7 more authors.
RSC Advances | Year: 2016

This article describes a facile method for the preparation of two-dimensionally patterned superhydrophobic hybrid coatings with controlled wettability. Superhydrophobic coatings were deposited from nanostructured organically modified silica (ormosil) colloids that were synthesized via a simple sol-gel method. On the defined areas of the superhydrophobic ormosil coatings, stable wetted micropatterns were produced using Ultraviolet/Ozone (UV/O) treatment which modifies the surface chemistry from hydrophobic to hydrophilic without changing the surface morphology. The degree of wettability can be precisely controlled depending on the UV/O exposure duration; extremely wetted spots with water contact angle (WCA) of nearly 0° can be obtained. Furthermore, we demonstrated high-throughput biomolecular adsorption and mixing using the superhydrophilic patterns. The proposed superhydrophilic-patterned nanostructured ormosil surfaces with their simple preparation, robust and controlled wettability as well as adaptability on flexible substrates, hold great potential for biomedical and chemical on-chip analysis. © The Royal Society of Chemistry 2016.

Yunusa M.,National Nanotechnology Research Center | Yunusa M.,Institute of Materials Science and Nanotechnology | Ozturk F.E.,National Nanotechnology Research Center | Ozturk F.E.,Institute of Materials Science and Nanotechnology | And 9 more authors.
RSC Advances | Year: 2017

We demonstrate a rice leaf-like hierarchically textured polymer fiber array for anisotropic non-wetting surfaces. To provide superhydrophobicity in addition to the anisotropic behavior, fiber surfaces are spray coated with organically modified silica nanoparticles. The resulting micro/nano hierarchically structured fiber surfaces demonstrate anisotropic non-wetting properties. We designed various fiber architectures for droplet transportation, mixing, and guiding exploiting the scalability of the fiber texture during thermal drawing; optional nanoparticle surface modification; and inherent flexibility of the fibers. © The Royal Society of Chemistry.

Ozkazanc G.,Bilkent University | Erdem E.Y.,Bilkent University | Erdem E.Y.,National Nanotechnology Research Center
20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016 | Year: 2016

We introduce capillary origami as a new method to print nanoparticles on curved, three dimensional polymer surfaces. When a liquid droplet containing nanoparticles is placed on a thin PDMS (polydimethylsiloxane) membrane, as the droplet evaporates, it folds the surface and leaves nanoparticles on it. We produced curved surfaces covered with a layer of magnetic iron-oxide (Fe3O4) nanoparticles with this method. These coated surfaces can be moved in a magnetic field.

Sari E.,National Nanotechnology Research Center | Jang L.W.,Chonbuk National University | Baek J.H.,Korea Photonics Technology Institute | Lee I.H.,Chonbuk National University | Demir H.V.,National Nanotechnology Research Center
Optics Express | Year: 2013

We study electroabsorption (EA) behavior of InGaN/GaN quantum structures grown using epitaxial lateral overgrowth (ELOG) in correlation with their dislocation density levels and in comparison to steady state and time-resolved photoluminescence measurements. The results reveal that ELOG structures with decreasing mask stripe widths exhibit stronger EA performance, with a maximum EA enhancement factor of 4.8 compared to the reference without ELOG. The analyses show that the EA performance follows similar trends with decreasing dislocation density as the essential parameters of the photoluminescence spectra (peak position, width and intensity) together with the photoluminescence lifetimes. While keeping the growth window widths constant, compared to photoluminescence behavior, however, EA surprisingly exhibits the largest performance variation, making EA the most sensitive to the mask stripe widths © 2013 Optical Society of America.

Rabaoui S.,Applied NanoMaterials | Dahman H.,Applied NanoMaterials | Dekhil S.,Applied NanoMaterials | Omri K.,Applied NanoMaterials | And 3 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2015

Thin films of Cu2SnS3 (CTS) were successfully prepared, by sol–gel spin coating technique on glass substrates. In this work, the effect of drying temperature on structural, morphological and optical characteristics is investigated. The X-ray diffraction patterns of the samples proved the polycrystalline nature and the formation of pure tetragonal Cu2SnS3 structure with (112) preferential orientation. The AFM and SEM images revealed that the CTS films have continuous and dense morphology. The average crystallite sizes calculated using the Debye–Scherrer formula increased from 3 to 6 nm and the direct optical band gap increased from 1.10 to 1.34 eV with increasing drying temperature from 150 to 300 °C. We found that by increasing the drying temperature, the sheet resistance decreased from 500 to 320 Ω. This makes the material as a good candidate for low cost and friendly environment thin film solar cells. © 2015 Springer Science+Business Media New York

Djeridi W.,Gabes University | Djeridi W.,Aix - Marseille University | Ouederni A.,Gabes University | Mansour N.B.,National Nanotechnology Research Center | And 4 more authors.
Materials Research Bulletin | Year: 2016

A series of activated carbon pellets (ACP) based on olive stones were studied for CO2 storage application. The surface area, pore volume, and pore diameter were evaluated from the analysis of N2 adsorption isotherm data. The characterization of carbon materials was performed by scanning electron microscopy (SEM), the powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The adsorption enthalpies were obtained by microcalorimetry. The effect of pyrolysis temperature on textural, electrical conductivity and gas adsorption capacities of the ACP were investigated by adsorbing CO2 at 303 K in the pressure range of 0-2.3 MPa. In fact the electrical conductivity is strongly affected by the microporosity of the samples and the size of the micropore. It increases when the pore size decreases which affect the CO2 adsorption. Also with increases temperature the free electrons concentration on the surface increases which affect the interaction of the adsorbed gas molecules. © 2015 Elsevier Ltd.

El-Atab N.,Masdar Institute of Science and Technology | Turgut B.B.,National Nanotechnology Research Center | Okyay A.K.,National Nanotechnology Research Center | Okyay A.K.,Institute of Material Science and Nanotechnology | And 3 more authors.
Nanoscale Research Letters | Year: 2015

In this work, we demonstrate a non-volatile metal-oxide semiconductor (MOS) memory with Quattro-layer graphene nanoplatelets as charge storage layer with asymmetric Al2O3/HfO2 tunnel oxide and we compare it to the same memory structure with 2.85-nm Si nanoparticles charge trapping layer. The results show that graphene nanoplatelets with Al2O3/HfO2 tunnel oxide allow for larger memory windows at the same operating voltages, enhanced retention, and endurance characteristics. The measurements are further confirmed by plotting the energy band diagram of the structures, calculating the quantum tunneling probabilities, and analyzing the charge transport mechanism. Also, the required program time of the memory with ultra-thin asymmetric Al2O3/HfO2 tunnel oxide with graphene nanoplatelets storage layer is calculated under Fowler-Nordheim tunneling regime and found to be 4.1 ns making it the fastest fully programmed MOS memory due to the observed pure electrons storage in the graphene nanoplatelets. With Si nanoparticles, however, the program time is larger due to the mixed charge storage. The results confirm that band-engineering of both tunnel oxide and charge trapping layer is required to enhance the current non-volatile memory characteristics. © 2015, El-Atab et al.

Yildirim A.,National Nanotechnology Research Center | Yildirim A.,Institute of Materials Science and Nanotechnology | Ozgur E.,National Nanotechnology Research Center | Ozgur E.,Institute of Materials Science and Nanotechnology | And 3 more authors.
Journal of Materials Chemistry B | Year: 2013

Although numerous mesoporous silica nanoparticle (MSN) drug carriers and theranostic agents with various surface functionalities have been designed in the last decade, their biocompatibility remains a matter of intensive debate. Here, we systematically evaluated interactions of a series of MSNs possessing different surface functional groups (ionic, polar, neutral, and hydrophobic) with blood constituents, in terms of their hemolytic activity, thrombogenicity, and adsorption of blood proteins on their surfaces. Using a hemolysis assay we showed that surface functionalization can reduce or even completely prevent the hemolytic activity of bare MSNs. We investigated thrombogenicity of MSNs by measuring prothrombin time (PT) and activated partial thromboplastin time (aPTT). We observed that none of the MSNs used in this study exhibit significant thrombogenic activity. Lastly, we examined non-specific protein adsorption on MSN surfaces using human serum albumin (HSA) and gamma globulins (γGs) and found that surface functionalization with ionic groups can greatly reduce protein adsorption. Demonstration of the surface functionalization having a crucial impact on blood compatibility might serve as a guideline for further investigation related to the design of mesoporous silica systems for biomedical applications, and shed light on research towards the ultimate goal of developing smart theranostic systems. This journal is © The Royal Society of Chemistry 2013.

Yildirim A.,National Nanotechnology Research Center | Yildirim A.,Institute of Materials Science and Nanotechnology | Budunoglu H.,National Nanotechnology Research Center | Budunoglu H.,Institute of Materials Science and Nanotechnology | And 7 more authors.
ACS Applied Materials and Interfaces | Year: 2011

One-pot synthesis of fluorinated mesoporous silica nanoparticles (FMSNs) is reported. Uniform mesoporous nanoparticles are prepared by condensation of tetraethyl orthosilicate (TEOS) and fluoroalkyl containing organotriethoxy silane monomers, respectively. The method enables selective deposition of fluorine atoms on the surface of the particles. FMSNs are used to prepare stable liquid marbles with water. An organo-modified silica sol is used with FMSNs to prepare mechanically stable superhydrophobic surfaces (water contact angle of 161°). The mechanical stability of the surface is investigated with water dripping and adhesive tape tests. The prepared FMSNs are promising building blocks for robust, large-area, and multifunctional self-cleaning surfaces. © 2011 American Chemical Society.

Cetin B.,Bilkent University | Ozer M.B.,TOBB University of Economics and Technology | Solmaz M.E.,Izmir Kâtip Celebi University | Solmaz M.E.,National Nanotechnology Research Center
Biochemical Engineering Journal | Year: 2014

Microfluidics and lab-on-a-chip technology offers unique advantages for the next generation devices for diagnostic therapeutic applications. For chemical, biological and biomedical analysis in microfluidic systems, there are some fundamental operations such as separation, focusing, filtering, concentration, trapping, detection, sorting, counting, washing, lysis of bio-particles, and PCR-like reactions. The combination of these operations led to the complete analysis systems for specific applications. Manipulation of the bio-particles is the key ingredient for these applications. Therefore, microfluidic bio-particle manipulation has attracted a significant attention from the academic community. Considering the size of the bio-particles and the throughput of the practical applications, manipulation of the bio-particles is a challenging problem. Different techniques are available for the manipulation of bio-particles in microfluidic systems. In this review, some of the techniques for the manipulation of bio-particles; namely hydrodynamic based, electrokinetic-based, acoustic-based, magnetic-based and optical-based methods have been discussed. The comparison of different techniques and the recent applications regarding the microfluidic bio-particle manipulation for different biotechnology applications are presented. Finally, challenges and the future research directions for microfluidic bio-particle manipulation are addressed. © 2014 Elsevier B.V.

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