Nanotechnology

Peptidic coating for gold nanospheres multifunctionalizable with photostable and photolabile moieties

by Valerio Voliani

Journal of Materials Chemistry 2012 (RSC), doi: 10.1039/C2JM31782F

A single-step method to coat and trifunctionalize water-dispersed gold nanospheres (AuNss) with
carboxylic acids,... more A single-step method to coat and trifunctionalize water-dispersed gold nanospheres (AuNss) with
carboxylic acids, amines, and alkynes is reported. The coating is based on a mix of two hexa-peptides,
differing only in the C-terminal amino acid. The process yields AuNss that are non-cytotoxic, stable in
physiological environments, and which present three reactive surface groups allowing rapid, selective,
10 and modular conjugation (click- and peptide-reactions) to virtually any chosen biomolecule or
fluorophore. Conjugated nanostructures were analyzed in vitro and in living cells. Confocal imaging and
colocalization analyses demonstrate the presence and reactivity of three different types of covalent bonds
with payloads: two of these are photostable while one bond is photolabile and can be cleaved by *Wpower
irradiation with a 561-nm cw laser.

Single and Mixed Phase TiO2 Powders by Excess Hydrolysis of Titanium Alkoxide

by Material Science

To investigate excess-hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium-tetra-isopropoxide... more To investigate excess-hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium-tetra-isopropoxide using 6:1 and 100:1 H2O:Ti (r) ratios. Powders were dried and fired at a range of temperatures (≤800ºC). Hydroxylation and organic content in powders were characterised using ATR-FTIR, laser Raman microspectroscopy, and elemental microanalysis; surface area and pore size distribution were evaluated using N2 gas adsorption; phase composition was analysed using XRD and laser Raman microspectroscopy; and crystallite size was evaluated by XRD, TEM and SEM. Results showed near-complete hydrolysis in a predominantly aqueous medium (r = 100), resulting in precipitated crystalline powders exhibiting brookite and anatase, which begin to transform to rutile below 500°C. Powders precipitated in a predominantly organic medium (r = 6) underwent partial hydrolysis, were highly porous and exhibited an amorphous structure, with crystallisation of anatase occurring at ~300°C and transformation to rutile beginning at 500°-600°C.

High Density Growth of Indium seeded Silicon Nanowires in the Vapor phase of a High Boiling Point Solvent

by Hugh Geaney

Effects of Substrate Temperature on Indium Gallium Nitride Nanocolumn Crystal Growth

by Joshua Pearce

S. Keating, M.G. Urquhart, D.V.P. McLaughlin and J.M.Pearce, “Effects of Substrate Temperature on Indium Gallium Nitride Nanocolumn Crystal Growth”, Crystal Growth & Design, 11 (2), pp 565–568, 2011. http://dx.doi.org/10.1021/cg101450n

Indium gallium nitride films with nanocolumnar microstructure were deposited with varying indium content and substrate... more Indium gallium nitride films with nanocolumnar microstructure were deposited with varying indium content and substrate temperatures using plasma-enhanced evaporation on amorphous SiO2 substrates. FESEM and XRD results are presented, showing that more crystalline nanocolumnar microstructures can be engineered at lower indium compositions. Nanocolumn diameter and packing factor (void fraction) was found to be highly dependent on substrate temperature, with thinner and more closely packed nanocolumns observed at lower substrate temperatures.

Temperature dependent conductivity and structural properties of sol-gel prepared holmium doped Bi2O3 nanoceramic powder

by Prof.Dr. İbrahim USLU

İ. Taşçıoğlu, M. Arı, İ. Uslu, S. Koçyiğit, Y. Dağdemir, V. Çorumlu and Ş. Altındal
Ceramics International, CERI_5314
Accepted paper, Manuscript Number: CERI-D-12-00407R2

Holmium (Ho)-doped Bi2O3 nanoceramic powders derived from sol-gel method have been studied in terms of structural,... more Holmium (Ho)-doped Bi2O3 nanoceramic powders derived from sol-gel method have been studied in terms of structural, morphological, and electrical properties. The morphology of the nanoceramic materials was analyzed by scanning electron microscopy (SEM) and their structure by Xray powder diffraction (XRD). Temperature dependence of DC conductivity measurements of nanoceramic powders were carried out by using DC four-point probe technique (4PPT) in air at temperatures ranging from 429 °C to 896 °C (702-1169 K). Electrical conductivity results demonstrate that there is a sharp increase at around 700 °C, which indicates an existence of order-disorder transition. This result supported by the Differential Thermal Analyzer (DTA) curve and XRD pattern which show that the sample has stable high oxygen ionic conductivity fluorite type face centered cubic -phase. Electrical characteristics also show that the DC conductivity in the studied materials obeys Arrhenius relation with different activation energies and conduction mechanisms: two temperature regions with activation energies Ea1=1.40 eV (702-993 K) and Ea2=0.66 eV (1006-1169 K). The analysis of experimental data revealed that the translation motion of the charge carrier, oxygen vacancies, and space charge polarization are responsible for the change in activation energy as a function of temperature.

Silver nanoparticles; size, function and areas for advancement

by Michael Sweet

In press Advances in Applied Microbiology

Nanoparticles (NP) are attracting increased attention in commerce and applied microbiology due to their anti-microbial... more Nanoparticles (NP) are attracting increased attention in commerce and applied microbiology due to their anti-microbial activity, high electrical conductivity, and optical properties. For example, silver NPs have broad spectrum antimicrobial properties against a wide range of bacteria and fungi, making them ideal for minimizing biofouling. By controlling the size, shape, surface and agglomeration state of the NPs, specific ion release profiles can be developed for any given application. Currently NPs are formed in a wide variety of different shapes and sizes including spheres, plates and wires. This review will look at both commercially and naturally produced NP with a focus on silver NPs and address how these are formed. Furthermore potential areas for improving these techniques will be highlighted, focusing on advancing shape and structure formation using modern applications. Finally the review evaluates the feasibility of bioengineering microorganisms to synthesise particles of defined shape and size, by examining genes associated with NP production.

Assessing the diffusion of nanotechnology in Turkey: A social network analysis approach

by Hamid Darvish

"Original Copy", " Will be published in the COLLNET 'Journal of Scientometrics and Information Management ', June 2012 Edition"

According to the United Nations, nanotechnology is one of the emerging research fields which will have a positive... more According to the United Nations, nanotechnology is one of the emerging research fields which will have a positive impact on both developing and developed countries. For example, nanotechnology is used for water purification in poor countries. On the other hand, it is used in developed countries (rich) to manufacture better computer devices. Nanotechnology is a part of the strategic plan for each developing country. For example, the 7th European Union Scientific Framework (EUSF) has invested tremendously in nanotechnology since 2000. The Turkish government also has adopted a new approach by becoming part of the EUSF and has invested heavily in research and development. Focusing on an invisible college in the scientific community in Turkey, this study aims to evaluate the diffusion of nanotechnology among scientists. Using social network analysis metrics, we identified and analyzed the role and status of scientists in the two most prominent universities (Hacettepe University & Bilkent University) regarding nano-related technologies diffusion in Turkey. We found that co-authorship across the two universities is minimal, even in subject area research in both universities. However, the number of nano-related articles have increased exponentially in past decade in Turkey. Furthermore, a co-word analysis revealed the scientific trends in both universities. Keywords description revealed that the scientific trends in Hacettepe University are mostly nano biomedical research oriented whereas in Bilkent University scientific trends are metallurgical oriented in nano-related technologies. Data were derived from Thomson Reuters’ Web of Science (WoS) version 4 database and CiteSpace was used to map the co-author network structure.

Nerlich, B. (2012). Biomilitarism and nanomedicine: Evil metaphors for the good of human health? Covalence Magazine

by Brigitte Nerlich

article for a special issue on nanoscience, ethics and religion edited by Chris Toumey

Size Controlled Growth of Germanium Nanorods and Nanowires by Solution Pyrolysis Directly on a Substrate

by Hugh Geaney

The calibration of carbon nanotube based bio-nano sensors

by Rajib Chowdhury

Journal of Applied Physics, 107[12] (2010), pp. 124322:1-8.

We derive the calibration constants necessary for using single-walled carbon nanotubes (SWCNTs) as nano-scale mass... more We derive the calibration constants necessary for using single-walled carbon nanotubes (SWCNTs) as nano-scale mass sensors. The carbon nanotube resonators are assumed to be either in cantilevered or in bridged configurations. Two cases, namely when the added mass can be considered as a point mass and when the added mass is distributed over a larger area are considered. Closed-form transcendental equations have been derived for the frequency shift due to the added mass. Using the energy principles, generalized nondimensional calibration constants have been derived for an explicit relationship between the added mass and the frequency shift. A molecular mechanics model based on the universal force field potential is used to validate the new results presented. The results indicate that the distributed nature of the mass to be detected has considerable effect on the performance of the sensor.

Karthick B and Ramesh Maheshwari, 2008. Lotus-Inspired Nanotechnology Applications.

by Karthick Balasubramanian

Resonance (Journal of science education from Indian Academy of Sciences, Bangalore). 1141-1145.

The water-repellent surface of lotus (Nelumbo nucifera) leaf and flower is due to nanosized wax papillae on the upper... more The water-repellent surface of lotus (Nelumbo nucifera) leaf and flower is due to nanosized wax papillae on the upper side of each epidermal cell. As a result, raindrops make a high contact angle with the papillae and roll off carrying dust and dirt particles, leaving the surface clean. This self-cleaning property of highly hydrophobic surfaces, termed as the lotus effect, has opened the possibilities of fabricating superhydrophobic surfaces for a variety of products.

Optimization of open circuit voltage in amorphous silicon solar cells with mixed-phase (amorphous+nanocrystalline) p-type contacts of low nanocrystalline content

by Joshua Pearce

J. M. Pearce, N. Podraza, R. W. Collins, M.M. Al-Jassim, K.M. Jones, J. Deng, and C. R. Wronski "Optimization of Open-Circuit Voltage in Amorphous Silicon Solar Cells with Mixed Phase (Amorphous + Nanocrystalline) p-Type Contacts of Low Nanocrystalline Content", Journal of Applied Physics, 101(11), 114301, 2007.

Both the origins of the high open circuit voltages (VOC) in amorphous silicon solar cells having p layers prepared... more Both the origins of the high open circuit voltages (VOC) in amorphous silicon solar cells having p layers prepared with very high hydrogen dilution and the physical structure of these optimum p layers remain poorly understood topics, with several studies offering conflicting views. This work attempts to overcome the limitations of previous studies by combining insights available from electronic measurements, real time spectroscopic ellipsometry, atomic force microscopy, and both high-resolution transmission electron microscopy (TEM) and dark field TEM of cross sections of entire solar cells. It is found that solar cells fabricated with p layers having a low volume fraction of nanocrystals embedded in a protocrystalline Si:H matrix possess lower recombination at the i/p interface than standard cells and deliver a higher VOC. The growth of the p layers follows a thickness evolution in which pure protocrystalline character is observed at the interface to the i layer. However, a low density of nanocrystallites nucleates with increasing thickness. The advantages offered by the protocrystalline character associated with the amorphous phase of the mixed-phase (amorphous+nanocrystalline) p layers prepared with excess H2 dilution account for the improved VOC of the optimum p layers. In this model, the appearance of a low volume fraction of nanocrystals near the top transparent conductor interface is proposed to be incidental to the high VOC.

Color Detection Using Chromophore-Nanotube Hybrid Devices

by Bryan Wong

Nano Letters, 9, 1028 (2009)

- Featured as "Headline News" in "physicsworld.com"
http://physicsworld.com/cws/article/news/37873

- Featured in "MIT Technology Review"
http://www.technologyreview.com/computing/22257/?a=f

- Featured as "News and Views" in "Nature Photonics"
http://www.nature.com/nphoton/journal/v3/n4/full/nphoton.2009.35.html

- Featured as "Nanotechnology News" in "PhysOrg.com"
http://www.physorg.com/news160318604.html

- Featured in "Ceramic Tech Today"
http://ceramics.org/ceramictechtoday/2009/05/26/carbon-nanotubes-used-to-detect-color/

- Featured as "News" in "The Future of Things"
http://thefutureofthings.com/news/7187/carbon-nanotubes-see-full-visible-spectrum.html

- Featured as "Technology" in "Photonics Spectra"
http://www.photonics.com/Content/ReadArticle.aspx?ArticleID=38650

- Featured on the cover of "electroindustry"
http://www.nxtbook.com/ygsreprints/ygs/P10945_Nema_August09_EI/

- Featured as "Issues and Events" in "Physics Today"
http://dx.doi.org/10.1063/1.3248467

Optoelectronic Properties of Carbon Nanorings: Excitonic Effects from Time-Dependent Density Functional Theory

by Bryan Wong

Journal of Physical Chemistry C, 113, 21921 (2009)

Self-Assembled Cyclic Oligothiophene Nanotubes: Electronic Properties from a Dispersion-Corrected Hybrid Functional

by Bryan Wong

Physical Review B, 84, 075115 (2011)

- Selected by the editor to appear in the August 22, 2011 issue of the "Virtual Journal of Nanoscale Science & Technology" (Volume 24, Issue 8)
http://link.aip.org/link/VIRT01/v24/i8/p92

Nanoscale Effects on Heterojunction Electron Gases in GaN/AlGaN Core/Shell Nanowires

by Bryan Wong

Nano Letters, 11, 3074 (2011)

Spectroscopic Properties of Nanotube-Chromophore Hybrids

by Bryan Wong

ACS Nano, 5, 7767 (2011)

Anomalous Optoelectronic Properties of Chiral Carbon Nanorings...and One Ring to Rule Them All

by Bryan Wong

Journal of Physical Chemistry Letters, 2, 2702 (2011)

Reversible, Opto-Mechanically Induced Spin-Switching in a Nanoribbon-Spiropyran Hybrid Material

by Bryan Wong

Nanoscale, 4, 1321 (2012)

Biosynthesis of Metallic Nanoparticles using Micro and Macro Organisms

by Jameel Shaik

Co-authored with Indu, H to be published in Nanotechnology in Biology and Medicine, Studium Press, USA as a book-chapter

One of the interesting applications of nanotechnology lies in the synthesis and stabilization of various metallic... more One of the interesting applications of nanotechnology lies in the synthesis and stabilization of various metallic nanoparticles. Nanoparticles, generally considered as particles with a size of up to 100 nanometers (nm), exhibit improved properties as compared to the larger particles based on specific characteristics such as size, distribution, and morphology. The application of nanoscale materials and structures, usually ranging from 1 to 100 nm, is an emerging area of nanoscience and nanotechnology. Currently, there is a constant need to develop eco-friendly processes for the synthesis of nanoparticles. The focus for this synthesis has shifted from physical and chemical processes towards ‘green’ chemistry and bioprocesses. Arrays of physical, chemical, and biological methods have been used to synthesize nanomaterials.
In order to synthesize noble metal nanoparticles of particular shape and size, specific methodologies have been formulated. Although ultraviolet irradiation, aerosol technologies, lithography, laser ablation, ultrasonic fields, and photochemical reduction techniques have been employed successfully to produce nanoparticles, they remain expensive and involve the use of hazardous chemicals. Therefore, there is a growing concern to develop environment-friendly and sustainable methods and now-a-days the techniques of nanoparticles synthesis employs the use of plants, microorganisms etc., which is referred to as “Green Synthesis” of nanoparticles.  Since the synthesis of nanoparticles of different compositions, sizes, shapes and controlled dispersity is an important aspect of nanotechnology many more new cheap and cost-effective procedures are being developed. Green synthesis of gold & silver nanoparticles using plant sources, microorganisms and their applications in several fields will be dealt in this review.