An innovative route is reported to fabricate nano-particles in aqueous solution from oxyfluoride glass by the thermal induction and corrosion treatment in this letter. The investigations of X-ray diffraction and transmission electron microscope based on nano-particles in glass ceramics (GCs) and aqueous solution indicate that the nano-particles formed in glass matrix during the thermal induction process are released to aqueous solution and their structure, shape and luminescent properties in glass host can be kept. Owing to the designable composition of the nano-particles during glass preparation process, the method is a novel way to obtain nano-particles in aqueous solution from GCs.
Nano-TiO2 was shown to cause various toxic effects in both rats and mice; however, the molecular mechanism by which TiO2 exerts its toxicity is poorly understood. In this report, an interaction of nano-anatase TiO2 with liver DNA from ICR mice was systematically studied in vivo using ICP-MS, various spectral methods and gel electrophoresis. We found that the liver weights of the mice treated with higher amounts of nano-anatase TiO2 were significantly increased. Nano-anatase TiO2 could be accumulated in liver DNA by inserting itself into DNA base pairs or binding to DNA nucleotide that bound with three oxygen or nitrogen atoms and two phosphorous atoms of DNA with the Ti–O(N) and Ti–P bond lengths of 1.87 and 2.38 Å, respectively, and alter the conformation of DNA. And gel electrophoresis showed that higher dose of nano-anatase TiO2 could cause liver DNA cleavage in mice.
Although it is known that nano-TiO2or other nanoparticles can induce liver toxicities, the mechanisms and the molecular pathogenesis are still unclear. In this study, nano-anatase TiO2(5 nm) was injected into the abdominal cavity of ICR mice for consecutive 14 days, and the inflammatory responses of liver of mice was investigated. The results showed the obvious titanium accumulation in liver DNA, histopathological changes and hepatocytes apoptosis of mice liver, and the liver function damaged by higher doses nano-anatase TiO2. The real-time quantitative RT-PCR and ELISA analyses showed that nano-anatase TiO2can significantly alter the mRNA and protein expressions of several inflammatory cytokines, including nucleic factor-κB, macrophage migration inhibitory factor, tumor necrosis factor-α, interleukin-6, interleukin-1β, cross-reaction protein, interleukin-4, and interleukin-10. Our results also implied that the inflammatory responses and liver injury may be involved in nano-anatase TiO2-induced liver toxicity.
Southern pine specimens vacuum-treated with nano-zinc oxide (nano-ZnO) dispersions were evaluated for leach resistance and UV protection. Virtually, no leaching occurred in any of the nano-ZnO–treated specimens in a laboratory leach test, even at the highest retention of 13 kg/m3. However, specimens treated with high concentrations of nano-ZnO showed 58–65% chemical depletion after 12 months of outdoor exposure. Protection from UV damage after 12 months exposure is visibly obvious on both exposed and unexposed surfaces compared to untreated controls. Graying was markedly diminished, although checking occurred in all specimens. Nano-zinc oxide treatment at a concentration of 2.5% or greater provided substantial resistance to water absorption following 12 months of outdoor exposure compared to untreated and unweathered southern pine. We conclude that nano-zinc oxide can be utilized in new wood preservative formulations to impart resistance to leaching, water absorption and UV damage of wood.
Historically most residential wood preservatives were aqueous soluble metal formulations, but recently metals ground to submicron size and dispersed in water to give particulate formulations have gained importance. In this study, the specific role nano-zinc oxide (ZnO) particle size and leach resistance plays in termite mortality resulting from exposure to particulate ZnO-treated wood was investigated. Southern yellow pine (SYP) sapwood impregnated with three concentrations of two particle sizes (30 and 70 nm) of ZnO were compared to wood treated with soluble zinc sulphate (ZnSO4) preservative for leach resistance and termite resistance. Less than four percent leached from the particulate nano-ZnO-treated specimens, while 13 to 25% of the zinc sulphate leached from the soluble treated wood. Nano-ZnO was essentially non-leachable from wood treated with 5% formulation for the 30-nm particle size. In a no-choice laboratory test, eastern subterranean termites (Reticulitermes flavipes) consumed less than 10% of the leached nano-ZnO-treated wood with 93 to 100% mortality in all treatment concentrations. In contrast, termites consumed 10 to 12% of the leached ZnSO4-treated wood, but with lower mortality: 29% in the 1% treatment group and less than 10% (5 and 8%...
We demonstrate a viable approach to fabricating ultrafast axial nano-oscillators based on carbon nanoscrolls (CNSs) using molecular dynamics simulations. Initiated by a single-walled carbon nanotube (CNT), a monolayer graphene can continuously scroll into a CNS with the CNT housed inside. The CNT inside the CNS can oscillate along axial direction at a natural frequency of tens of gigahertz. We demonstrate an effective strategy to reduce the dissipation of the CNS-based nano-oscillator by covalently bridging the carbon layers in the CNS. We further demonstrate that such a CNS-based nano-oscillator can be excited and driven by an external AC electric field, and oscillate at more than 100 GHz. The CNS-based nano-oscillators not only offer a feasible pathway toward ultrafast nano-devices but also hold promise to enable nanoscale energy transduction, harnessing, and storage (e.g., from electric to mechanical).
We report the fabrication of gold/polycarbonate (Au/PC) hybrid nano resonators on plastic substrates through a nano-transfer printing (nTP) technique, and the parametric studies of the resonant frequency of the resulting hybrid nano resonators. nTP is a nanofabrication technique that involves an assembly process by which a printable layer can be transferred from a transfer substrate to a device substrate. In this article, we applied nTP to fabricate Au/PC hybrid nano resonators on a PC substrate. When an AC voltage is applied, the nano resonator can be mechanically excited when the AC frequency reaches the resonant frequency of the nano resonator. We then performed systematic parametric studies to identify the parameters that govern the resonant frequency of the nano resonators, using finite element method. The quantitative results for a wide range of materials and geometries offer vital guidance to design hybrid nano resonators with a tunable resonant frequency in a range of more than three orders of magnitude (e.g., 10 KHz-100 MHz). Such nano resonators could find their potential applications in nano electromechanical devices. Fabricating hybrid nano resonators via nTP further demonstrates nTP as a potential fabrication technique to enable a low-cost and scalable roll-to-roll printing process of nanodevices.
New types of porphyrin nano- and micro-particles composed of J- and H-heteroaggregates were prepared by electrostatic self-assembly of two oppositely charged porphyrins, tetrakis(4-trimethylammoniophenyl)porphyrin (H2TAPP4+) and tetrakis(4-sulfonatophenyl)porphyrin cobalt(II) (CoTPPS4−), in aqueous solutions. Transmission electron microscopy (TEM) images showed novel morphology and size distribution of porphyrin particles fabricated under different experimental conditions. The assembly process of the nano- and micro-particles was monitored by UV–Vis spectra. Fluorescence spectra and UV–Vis spectra provided optical information on the formation of the nano- and micro-particles. Cyclic voltammograms of the porphyrin particles indicated that the electron gain and loss of the H2TAPP4+ion were restrained, and the electron transfer of the CoTPPS4−ion was promoted in the J- and H-type porphyrin heteroaggregates within the particles. The stability and constitution of the nano- and micro-particles were confirmed by UV-light irradiation, heat-treatment, and pH and ionic strength changes. Photoelectrochemical measurements showed that the photoelectron transfer of TiO2modified with the particles was more efficient than that of TiO2sensitized by either monomers. The photoelectronic and photocatalytic properties of the products indicated that the pyramidal or spherical configuration of the nano- and micro-particles was favorable for the absorption and transfer of the energy. It can be found that TiO2sensitized by the porphyrin nano- and micro-particles exhibits significant improvement in energy conversion and photocatalytic activity with reference to pure TiO2.
Computer-aided design plays a fundamental role in both top-down and bottom-up nano-system fabrication. This paper presents a bottom-up nano-filter patterning process based on DNA self-assembly. In this study we designed a new method to construct fully designed nano-filters with the pores between 5 nm and 9 nm in diameter. Our calculations illustrated that by constructing such a nano-filter we would be able to separate many molecules.
The Class F fly ash has been subjected to high energy ball milling and has been converted into nanostructured material. The nano structured fly ash has been characterized for its particle size by using particle size analyzer, specific surface area with the help of BET surface area apparatus, structure by X-ray diffraction studies and FTIR, SEM and TEM have been used to study particle aggregation and shape of the particles. On ball milling, the particle size got reduced from 60 μm to 148 nm by 405 times and the surface area increased from 0.249 m2/gm to 25.53 m2/gm i.e. by more than 100%. Measurement of surface free energy as well as work of adhesion found that it increased with increased duration of ball milling. The crystallite was reduced from 36.22 nm to 23.01 nm for quartz and from 33.72 nm to 16.38 nm for mullite during ball milling to 60 h. % crystallinity reduced from 35% to 16% during 60 h of ball milling because of destruction of quartz and hematite crystals and the nano structured fly ash is found to be more amorphous. Surface of the nano structured fly ash has become more active as is evident from the FTIR studies. Morphological studies revealed that the surface of the nano structured fly ash is more uneven and rough and shape is irregular...
Pine needle-like Pd micro/nano-leaves have been synthesized by a facile, template-free electrochemical method. As-synthesized Pd micro/nano-leaves were directly electrodeposited on an indium tin oxide substrate in the presence of 1.0 mM H2PdCl4 + 0.33 M H3PO4. The formation processes of Pd micro/nano-leaves were revealed by scanning electron microscope, and further characterized by X-ray diffraction and electrochemical analysis. Compared to conventional Pd nanoparticles, as-prepared Pd micro/nano-leaves exhibit superior electrocatalytic activities for the formic acid oxidation.
Super-hydrophobic surfaces which have been fabricated by various methods such as photolithography, chemical treatment, self-assembly, and imprinting have gained enormous attention in recent years. Especially 2D arrays of nano-needles have been shown to have super-hydrophobicity due to their sharp surface roughness. These arrays can be easily generated by removing the top portion of the honeycomb films prepared by the breath figures method. The hydrophilic block of an amphiphilic polymer helps in the fabrication of the nano-needle arrays through the production of well-ordered honeycomb films and good adhesion of the film to a substrate. Anisotropic patterns with water wettability difference can be useful for patterning cells and other materials using their selective growth on the hydrophilic part of the pattern. However, there has not been a simple way to generate patterns with highly different wettability. Mechanical stamping of the nano-needle array with a polyurethane stamp might be the simplest way to fabricate patterns with wettability difference. In this study, super-hydrophobic nano-needle arrays were simply fabricated by removing the top portion of the honeycomb films. The maximum water contact angle obtained with the nano-needle array was 150°. By controlling the pore size and the density of the honeycomb films...
The vertically orientated TiO2 nanotube array (TNA) decorated with TiO2 nano-particles was successfully fabricated by electrochemically anodizing titanium (Ti) foils followed by Ti-precursor post-treatment and annealing process. The TNA morphology characterized by SEM and TEM was found to be filled with TiO2 nano-particles interior and exterior of the TiO2 nano-tubes after titanium (IV) n-butoxide (TnB) treatment, whereas TiO2 nano-particles were only found inside of TiO2 nano-tubes upon titanium tetrachloride (TiCl4) treatment. The efficiency in TNA-based DSSCs was improved by both TnB and TiCl4 treatment presumably due to the increase of dye adsorption.
A study of nucleate boiling phenomena on nano/microstructures is a very basic and useful study with a view to the potential application of modified surfaces as heating surfaces in a number of fields. We present a detailed study of boiling experiments on fabricated nano/microstructured surfaces used as heating surfaces under atmospheric conditions, employing identical nanostructures with two different wettabilities (silicon-oxidized and Teflon-coated). Consequently, enhancements of both boiling heat transfer (BHT) and critical heat flux (CHF) are demonstrated in the nano/microstructures, independent of their wettability. However, the increment of BHT and CHF on each of the different wetting surfaces depended on the wetting characteristics of heating surfaces. The effect of water penetration in the surface structures by capillary phenomena is suggested as a plausible mechanism for the enhanced CHF on the nano/microstructures regardless of the wettability of the surfaces in atmospheric condition. This is supported by comparing bubble shapes generated in actual boiling experiments and dynamic contact angles under atmospheric conditions on Teflon-coated nano/microstructured surfaces.
Synthesis and characterization of nano-crystalline silicon grown by atom beam sputtering technique are reported. Rapid thermal annealing of the deposited films is carried out in Ar + 5% H2 atmosphere for 5 min at different temperatures for precipitation of silicon nano-crystals. The samples are characterized for their optical and structural properties using various techniques. Structural studies are carried out by micro-Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy, and selected area electron diffraction. The optical properties are studied by photoluminescence and UV-vis absorption spectroscopy, and bandgaps are evaluated. The bandgaps are found to decrease after rapid thermal treatment. The micro-Raman studies show the formation of nano-crystalline silicon in as-deposited as well as annealed films. The shifting and broadening in Raman peak suggest formation of nano-phase in the samples. Results of micro-Raman, photoluminescence, and TEM studies suggest the presence of a bimodal crystallite size distribution for the films annealed at higher temperatures. The results show that atom beam sputtering is a suitable technique to synthesize nearly mono-dispersed silicon nano-crystals. The size of the nano-crystals may be controlled by varying annealing parameters.
We study metallic nano-particles for light trapping by investigating the optical absorption efficiency of the hydrogenated amorphous silicon thin film with and without metallic nano-particles on its top. The size and shape of these nano-particles are investigated as to their roles of light trapping: scattering light to the absorption medium and converting light to surface plasmons. The optical absorption enhancement in the red light region (e.g., 650nm) due to the light trapping of the metallic nano-particles is observed when a layer of metallic nano-particle array has certain structures. The investigation of the light with incident angles shows the importance of the coupling efficiency of light to surface plasmons in the metallic nano-particle light trapping.
Nano-branched rutile TiO2 nanorod arrays were grown on F:SnO2 conductive glass (FTO) by a facile, two-step wet chemical synthesis process at low temperature. The length of the nanobranches was tailored by controlling the growth time, after which CdS quantum dots were deposited on the nano-branched TiO2 arrays using the successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The photovoltaic properties of the CdS-sensitized nano-branched TiO2 solar cells were studied systematically. A short-circuit current intensity of approximately 7 mA/cm2 and a light-to-electricity conversion efficiency of 0.95% were recorded for cells based on optimized nano-branched TiO2 arrays, indicating an increase of 138% compared to those based on unbranched TiO2 nanorod arrays. The improved performance is attributed to a markedly enlarged surface area provided by the nanobranches and better electron conductivity in the one-dimensional, well-aligned TiO2 nanorod trunks.
Bionic self-cleaning surfaces with well-ordered polymer nano-fibers are firstly fabricated by disturbing crystallization during one-step coating-curing process. Orderly thin (100 nm) and long (5–10 μm) polymer nano-fibers with a certain direction are fabricated by external macroscopic force (Fblow) interference introduced by H2 gas flow, leading to superior superhydrophobicity with a water contact angle (WCA) of 170° and a water sliding angle (WSA) of 0-1°. In contrast, nano-wires and nano-bridges (1–8 μm in length/10-80 nm in width) are generated by “spinning/stretching” under internal microscopic force (FT) interference due to significant temperature difference in the non-uniform cooling medium. The findings provide a novel theoretical basis for controllable polymer “bionic lotus” surface and will further promote practical application in many engineering fields such as drag-reduction and anti-icing.
Chitin nano-fibers with positive and negative charges have been, respectively, produced from partially deacetylated and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidized α-chitin. The average diameters and lengths of the TEMPO-oxidized chitin nano-fibers (TOChN) were 14 ± 4.3 and 190 ± 140 nm, respectively, and the average diameters and lengths of the partially deacetylated chitin nano-fibers (DEChN) were 6 ± 1.7 and 320 ± 105 nm, respectively. A partially deacetylated chitin nano-fiber film (DEChN-F), a TEMPO-mediated and oxidized chitin nano-fiber film (TOChN-F), and a composite film (DE-TO-ChN-F) consisting of a combination of the two were prepared by drying the dispersions at 40 °C. The DEChN-F, TOChN-F, and DE-TO-ChN-F all have similar tensile strengths of approximately 90 MPa; however, the chitosan film (Chitosan-F) had a tensile strength of approximately 30 MPa. In addition, TOChN-F and DE-TO-ChN-F have a thermal weight loss at 210 °C, and DEChN-F has a thermal weight loss at 280 °C. DEChN-F was found to have antimicrobial activity with regards to Escherichia coli. Finally, the chitin nano-fiber films could be slightly degraded by cellulase, which provided a novel biological performance of the chitin nano-material.
Nano/micro-manufacturing under wet condition is an important consideration for various tool-based processes such as indentation, scratching, and machining. The existence of liquids adds complexity to the system, changes the tool/work interfacial condition, and affects material behaviors. For indentation, it may also affect material property measurements. However, little effort has been made to study this challenging issue at nano- or atomistic scale. In this study, we tackle this challenge by investigating nano-indentation processes submerged in water using the molecular dynamics (MD) simulation approach. Compared with dry indentation in which no water molecules are present, the existence of water molecules causes the increase of indentation force in initial penetration, but the decrease of indentation force in full penetration. It also reduces the sticking phenomenon between the work and tool atoms during indenter retraction, such that the indentation geometry can be better retained. Meanwhile, nano-indentation under wet condition exhibits the indentation size effect, while dry nano-indentation exhibits the reverse indentation size effect. The existence of water leads to higher computed hardness values at low indentation loads and a smaller value of Young's modulus. In addition...