Order Of Magnitude Enhancement Research Articles

Melt crystallization of syndiotactic polypropylene in nanolayer confinement impacting structure

Layer multiplying coextrusion technique was used to fabricate films with hundreds of alternating layers of a crystallizable polymer, syndiotactic polypropylene (sPP), and an amorphous polymer, polycarbonate (PC). Atomic force microscopy and wide-angle X-ray scattering revealed the absence of any oriented crystal morphology of sPP in the extruded layered films. An approach of isothermal melt recrystallization of sPP nanolayers revealed the formation of oriented lamellae under the rigid confinement of hard glassy PC layers. X-ray scattering data showed that sPP crystallized as stacks of single crystal lamellae oriented parallel to the layers at high crystallization temperatures. As the crystallization temperature decreased, on-edge lamellar orientation was preferred. Formation of in-plane lamellae was attributed to heterogeneous bulk nucleation, while nucleation of on-edge lamellae was initiated at substrate interface. It was observed that as the layers thickness reduced, the orientations of both in-plane and on-edge lamellae became sharper. Detailed analysis of crystal orientations in 30 and 120 nm sPP layers was carried out. Melt recrystallization of 30 nm layers revealed formation of in-plane lamellae above 90 °C and mainly on-edge lamellae below 70 °C. At intermediate temperatures, formation of mixed crystals was reported. In 120 nm layers, crystallization temperature of 100 °C was required to form in-plane crystals, while on-edge lamellae were formed below 90 °C. We also investigated crystallization onset for on-edge and in-plane lamellar nucleation. Although, the two crystal fractions were significantly affected as a function of crystallization temperature, it was noticeable that both crystal habits were initiated at the same time. The results suggested that the relative growth rates of in-plane and on-edge crystal orientations was responsible for different fractions of the two crystal orientations at a given crystallization temperature. Oxygen transport properties of melt recrystallized sPP layers were measured. When the melt recrystallization temperature increased from 85 to 105 °C in 120 nm sPP layers, at least one order of magnitude enhancement in the barrier properties was observed. It was evident from the X-ray data that the amount of in-plane crystal fraction increased with increasing crystallization temperature. In-plane crystals acted as impermeable platelets to oxygen flux resulting in improved gas barrier properties. A similar effect was observed in 30 nm sPP layers over a temperature range of 60–105 °C. A correlation between in-plane crystal fraction and the oxygen permeability was obtained from X-ray and oxygen transport data analysis. It was shown that the permeability decreased exponentially with increasing in-plane crystal fraction.

A New Method to Calculate the Pure Component Parameters of Any Two-Parameter Equation of State

Reliable equations of state are very important in the design of refrigeration cycles, since thermodynamic properties can be calculated by simple differentiation. In this paper, a new method to calculate the parameters of any two-parameter equation of state is presented. The method is based on the use of Clapeyron equation and the experimental PVT data. This method was tested on a newly developed cubic equation of state and proved to be simple and fast. Results showed orders of magnitude enhancement in prediction of the saturated vapor pressure even near the critical region. The Percent Absolute Average Deviation (%AAD) was always less than 0.1 in the studied cases. It also showed that the parameters calculated using the original equation deviate strongly from the “experimental” values as the temperature decreases below the critical point. This method can be used to redefine the temperature dependences of these parameters and develop new mixing rules for the mixtures.

Photoluminescence plasmonic enhancement in InAs quantum dots coupled to gold nanoparticles

Photoluminescence enhancement due to dipole field from gold nanoparticles was observed at 77 K for GaAs capped InAs quantum dots. The gold nanoparticles were coupled to the surface of the cap layer by using dithiol ligands. The enhancement was investigated as a function of the GaAs capped layer thickness. An order of magnitude enhancement in the emission was observed in samples with a cap thickness of 12 nm. This enhancement however is drastically decreased in samples with a cap thickness of 200 nm. The observed enhancement is interpreted in terms of photon scattering from the large dipole scattering cross section.

Oxide thermoelectrics: The challenges, progress, and outlook

Abstract

A comparative study of Raman enhancement in capillaries

This work reports on the comparative studies of Raman enhancement in liquid core waveguides (LCWs). The theoretical considerations that describe Raman enhancement in LCWs is adapted to analyze and compare the performance of hollow core photonic crystal fibers (HCPCFs) to conventional Teflon capillary tubes. The optical losses in both platforms are measured and used to predict their performance for different lengths. The results show that for an optimal waveguide length, two orders of magnitude enhancement in the Raman signal can be achieved for aqueous solutions using HCPCFs. This length, however, cannot be achieved using normal capillary effects. By integrating the interface of the fluidic pump and the HCPCF into a microfluidic chip, we are able to control fluid transport and fill longer lengths of HCPCFs regardless of the viscosity of the sample. The long-term stability and reproducibility of Raman spectra attained through this platform are demonstrated for naphthalenethiol, which is a well-studied organic compound. Using the HCPCF platform, the detection limit of normal Raman scattering in the range of micro-molars has been achieved. In addition to the higher signal-to-noise ratio of the Raman signal from the HCPCF-platform, more Raman modes of naphthalenethiol are revealed using this platform.

Polyvalent saccharide-functionalized generation 3 poly(amidoamine) dendrimer–methotrexate conjugate as a potential anticancer agent

A saccharide-terminated generation 3 (G3) polyamidoamine (PAMAM) dendrimer was synthesized as a drug carrier. Utilizing this dendritic platform, we have successfully synthesized polyvalent conjugates (G3-MTX) containing the drug methotrexate (MTX). Surface Plasmon Resonance (SPR) results showed that G3-MTX presented three orders of magnitude enhancement in binding avidity to folate-binding protein (FBP) as compared to the free folic acid (FA). Flow cytometric and confocal microscopic analysis showed that conjugate (G3-MTX-FI) containing imaging agent fluorescein-5(6)-carboxamidohexanoic acid (FI) was internalized into folate receptor (FR)-expressing KB cells in dose-dependent and receptor-mediated fashion. The G3-MTX induced a dose-dependent cytotoxicity in the KB cells. Therefore, the polyvalent G3-MTX may have potential as an anticancer nanodevice for the specific targeting and killing of FR-expressing tumor cells.

Enhanced soft X-ray emission from carbon nanofibers irradiated with ultra-short laser pulses

A comparative experimental study of the X-ray emission in the water-window spectral region has been performed using carbon nanofibers (CNFs) of different sizes and graphite plate targets, irradiated with ultra-short (Ti:sapphire) laser pulses. More than an order of magnitude enhancement in the X-ray yield is observed from CNFs of 60-nm diameter with respect to graphite targets. The X-ray emission from CNFs of 160-nm diameter was also high. The integrated X-ray yield of these carbon-based targets scales with the laser intensity (IL) as \(I_{\mathrm{L}}^{\sim 1.3-1.4}\) in the intensity range of 4×1016–4×1017 W/cm2. The effect of the laser pulse duration on the X-ray emission from the CNFs was also studied by varying the pulse duration from 45 fs up to 3 ps at a constant fluence of 2×104 J/cm2. The optimum laser pulse duration for maximum X-ray emission increases with the diameter of the CNFs used. The results are explained from physical considerations of heating and hydrodynamic expansion of the CNF plasma in which resonance field enhancement takes place while passing through two times the critical density. The results add to the efforts towards achieving an efficient low-cost water-window X-ray source for microscopy.

A new regime for high rate growth of nanocrystalline diamond films using high power and CH 4/H 2/N 2/O 2 plasma

In this work, we report high growth rate of nanocrystalline diamond (NCD) films on silicon wafers of 2 inches in diameter using a new growth regime, which employs high power and CH 4/H 2/N 2/O 2 plasma using a 5 kW MPCVD system. This is distinct from the commonly used hydrogen-poor Ar/CH 4 chemistries for NCD growth. Upon rising microwave power from 2000 W to 3200 W, the growth rate of the NCD films increases from 0.3 to 3.4 μm/h, namely one order of magnitude enhancement on the growth rate was achieved at high microwave power. The morphology, grain size, microstructure, orientation or texture, and crystalline quality of the NCD samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, and micro-Raman spectroscopy. The combined effect of nitrogen addition, microwave power, and temperature on NCD growth is discussed from the point view of gas phase chemistry and surface reactions.

(CdSe) ZnS core shell quantum dots decorated zinc oxide nanowires for solar energy harvesting applications

ABSTRACTZnO nanostructures have proven to be versatile functional materials with promising electronic, piezoelectric and optical properties. Here, we report on the application of (CdSe) ZnS Core Shell quantum dots decorated ZnO Nanowires (ZnONWs) and Nanobelts (NBs) in solar energy harvesting. Results indicate that both as grown and decorated ZnO Nanostructures are photoactive, have a fast response time and generate photocurrent under excitation in a photoelectrochemical cell setup. An order of magnitude enhancement in the photocurrent response of (CdSe) ZnS Core Shell quantum dots decorated ZnONBs is seen as compared to response from as grown ZnONBs. Generated photocurrent decreases with time but stabilizes at higher value for (CdSe) ZnS Core Shell quantum dots coated ZnONBs. Detailed performances of these devices are discussed.

Stretching-induced percolation in polyvinylidene fluoride and nickel composites

To investigate the stretching effect of polymer-based composites, the films of polyvinylidene fluoride (PVDF) and nickel (Ni) composites were stretched at 120°C. It was found there was an abrupt increase in dielectric constants and conductivities with stretching ratio (SR). In comparison to percolation effect caused by involvement of conductive particles, it was named as stretching-induced percolation here. When SR was near the threshold, dielectric constants showed 17 times improvement and conductivities displayed four to five orders of magnitude enhancement at 100 Hz in low Ni fraction composites. And the reasons of stretching-induced percolation were analyzed here. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Impurities good and bad: Doped cluster nanoplasmas in intense laser fields and characterization of impurity level

Doping of cluster-based targets can bring out considerable modifications in the evolution of the nanoplasma formed from clusters in intense laser fields. The consequence could be either an increase or, a decrease (depending upon the properties and proportion of the dopant) in the emission of the resulting charge particles or photons from nanoplasma. As we can control the percentage of CS2 in the doped Ar-CS2 cluster, we can have argon-doped CS2 cluster (when argon constitutes about 10–40%) and CS2-doped argon cluster (when fraction of CS2 is 10–40%). In the experimental studies of electron spectra and X-ray emission from pristine Arn (n ≤ 25, 000) and doped Ar-CS2 clusters at laser intensities of about 1015 W cm−2, it is observed that there is more than an order of magnitude enhancement in those emissions in doped Ar-CS2 clusters than in the former case. Conversely, a significant reduction in those emissions was found in the latter case. Such observations signify the importance of characterization of these targets. In this direction, we demonstrate a simple method for the characterization of doping level based on the Rayleigh scattering measurements.

Tuning Gold Nanorod-Nanoparticle Hybrids into Plasmonic Fano Resonance for Dramatically Enhanced Light Emission and Transmission

We investigate the optical response of a gold nanorod array coupled with a semicontinuous nanoparticle film. We find that, as the gold nanoparticle film is adjusted to the percolating regime, the nanorod-film hybrids are tuned into plasmonic Fano resonance, characterized by the coherent coupling of discrete plasmonic modes of the nanorod array with the continuum band of the percolating film. Consequently, optical transmission of the percolating film is substantially enhanced. Even more strikingly, electromagnetic fields around the nanorod array become much stronger, as reflected by 2 orders of magnitude enhancement in the avalanche multiphoton luminescence. These findings may prove instrumental in the design of various plasmonic nanodevices.

Increase of SARS-CoV 3CL peptidase activity due to macromolecular crowding effects in the milieu composition

The 3C-like peptidase of the severe acute respiratory syndrome virus (SARS-CoV) is strictly required for viral replication, thus being a potential target for the development of antiviral agents. In contrast to monomeric picornavirus 3C peptidases, SARS-CoV 3CLpro exists in equilibrium between the monomer and dimer forms in solution, and only the dimer is proteolytically active in dilute buffer solutions. In this study, the increase of SARS-CoV 3CLpro peptidase activity in presence of kosmotropic salts and crowding agents is described. The activation followed the Hofmeister series of anions, with two orders of magnitude enhancement in the presence of Na₂SO₄, whereas the crowding agents polyethylene glycol and bovine serum albumin increased the hydrolytic rate up to 3 times. Kinetic determinations of the monomer dimer dissociation constant (K(d)) indicated that activation was a result of a more active dimer, without significant changes in K(d) values. The activation was found to be independent of substrate length and was derived from both k(cat) increase and K(m) decrease. The viral peptidase activation described here could be related to the crowded intracellular environment and indicates a further fine-tuning mechanism for biological control, particularly in the microenvironment of the vesicles that are induced in host cells during positive strand RNA virus infection.

Giant Hall effect in nonmagneticMo/SnO2granular films

We have measured the resistivities and Hall coefficients, ${R}_{H}$, of a series of nonmagnetic ${\text{Mo}}_{x}{({\text{SnO}}_{2})}_{1\ensuremath{-}x}$ nanogranular films with the Mo volume fraction $x$ ranging from $\ensuremath{\sim}0.29$ to 1. We found that the magnitude of ${R}_{H}(2\text{ }\text{K})$ largely increased by a factor of $\ensuremath{\sim}800$ as $x$ was reduced from $\ensuremath{\sim}0.8$ to $\ensuremath{\simeq}0.36$. Then, it slightly decreased with a further decrease in $x$ down to $\ensuremath{\simeq}0.32$, which was determined to be the classical percolation threshold, ${x}_{c}$, from the resistivity dependence on $x$. This nearly 3 orders of magnitude enhancement in ${R}_{H}$ at a metal volume fraction $x>{x}_{c}$ is explained in terms of the recent theoretical concept of the local quantum-interference effect induced giant Hall effect in granular systems.

Enhanced visible photoluminescence from ultrathin ZnO films grown on Si-nanowires byatomic layer deposition

Bright room temperature visible emission is obtained in heterostructures consisting of ∼ 3.5 nm thick ZnO ultrathin films grown on Si-nanowires produced by means of self-maskingdry etching in hydrogen-containing plasma. The ZnO films were deposited onSi-nanowires by using atomic layer deposition (ALD) under an ambient temperature of25 °C. The orders of magnitude enhancement in the intensity of the roomtemperature photoluminescence peaked around 560 nm in the presentZnO/Si-nanowire heterostructures is presumably due to the high aspect (surface/volume) ratio inherent to the Si-nanowires, which has, in turn, allowed considerably more ZnOmaterial to be grown on the template and led to markedly more efficient visible emission.Moreover, the ordered nanowire structure also features an extremely low reflectance (∼0.15%) at 325 nm, which may further enhance the efficiency of emission by effectively trappingthe excitation light.

2-Methacryloyloxyethyl phosphorylcholine polymer (MPC)-coating improves the transfection activity of GALA-modified lipid nanoparticles by assisting the cellular uptake and intracellular dissociation of plasmid DNA in primary hepatocytes

We previously reported that modification of GALA peptide on the surface of liposomes enhanced fusion with endosomal membrane, and cytoplasmic release of encapsulated macromolecules. We report herein that an additional coating of GALA-modified liposomes with 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer resulted in a two order of magnitude enhancement in the transfection activity of encapsulating plasmid DNA (pDNA). Quantification of the delivered gene copies in whole cells and isolated nuclei revealed that the increase of transfection activity can be attributed to improved efficiencies in cellular uptake and post-nuclear delivery processes. Imaging studies revealed that the intracellular dissociation of pDNA from the lipid envelope is enhanced by GALA modification and further coating with MPC polymer in a stepwise manner. The MPC polymer-coating decreased the ζ-potential of GALA-modified liposomes, suggesting that it assisted in the functional display of negatively charged GALA on the cationic liposomes by providing shielding from mutual electrostatic interactions. Collectively, these data indicate that MPC polymer-coating induced the fusogenic activity of the GALA-modified envelope with endosomes, leading to a more effective cytoplasmic release pDNA. The extensive fusion of the lipid envelope may also reduce electrostatic interactions between mRNA and cationic lipid components, thereby resulting in an enhancement in the translation process.

Selection of aptamers for signal transduction proteins by capillary electrophoresis

High-affinity aptamers for important signal transduction proteins, i.e. Cdc42-GTP, p21-activated kinase1 (PAK1) and MRCK (myotonic dystrophy kinase-related Cdc42-binding kinase) alpha were successfully selected in the low micro- to nanomolar range using non-systematic evolution of ligands by exponential enrichment (SELEX) with at least three orders of magnitude enhancement from their respective bulk affinity of naïve DNA library. In the non-SELEX procedure, CE was used as a highly efficient affinity method to select aptamers for the desired molecular target through a process that involved repetitive steps of partitioning, known as non-equilibrium CE of equilibrium mixtures with no PCR amplification between successive steps. Various non-SELEX conditions including the type, concentration and pH of the run buffer were optimized. Other considerations such as salt composition of selection buffer, protein concentration and sample injection size were also studied for high stringency during selection. After identifying the best enriched aptamer pool, randomly selected clones from the aptamer pool were sequenced to obtain the individual DNA sequences. The dissociation constants (K(d)) of these sequences were in the low micromolar to nanomolar range, indicating high affinity to the respective proteins. The best binders were also subjected to sequence alignment to generate a phylogenetic tree. No significant consensus region based on approximately 50 sequences for each protein was observed, suggesting the high efficiency of non-SELEX for the selection of numerous unique sequences with high selectivity.

Use of Reversal Nanoimprinting of Nanoparticles to Prepare Flexible Waveguide Sensors Exhibiting Enhanced Scattering of the Surface Plasmon Resonance

AbstractA flexible surface plasmon resonance (SPR)‐based scattering waveguide sensor is prepared by directly imprinting hollow gold nanoparticles (NPs) and solid gold NPs onto flexible polycarbonate (PC) plates—without any surface modification—using a modified reversal nanoimprint lithography technology. Controlling the imprinting conditions, including temperature and pressure, allows for the fine adjustment of the depths of the embedded metal NPs and their SPR properties. This patterning approach exhibits a resolution down to the submicrometer level. A 3D finite‐difference time domain simulation is used to examine the optical behavior of light propagating parallel to the air/substrate interface within the near‐field regime. Consistent with the simulations, almost an order of magnitude enhancement in the scattering signal after transferring the metal NPs from the glass mold to the PC substrate is obtained experimentally. The enhanced signal is attributed to the particles' strong scattering of the guiding‐mode waves (within the waveguide) and the evanescent wave (above the waveguide) simultaneously. Finally, the imprinting conditions are optimized to obtain a strongly scattering bio/chemical waveguide sensor.

Discovery of New Ferroelectrics: [H2dbco]2·[Cl3]·[CuCl3(H2O)2]·H2O (dbco = 1,4-Diaza-bicyclo[2.2.2]octane)

Compound [H(2)dbco](2) x [Cl(3)] x [CuCl(3)(H(2)O)(2)] x H(2)O undergoes a sharp dielectric anomaly and a paraelectric-to-ferroelectric phase transition at approximately -23 degrees C with a spontaneous polarization of 1.04 microC cm(-2), being the first molecular metal coordination compound ferroelectrics with a large dielectric response involving a 2 orders of magnitude enhancement and distinct Curie phase transition point. This work has proved an effective way for exploration of new ferroelectrics based on a five-coordinated divalent metal through the combination of crystal engineering and Landau phase transition theory.

Differential amplification of structural perturbations in weakly coupled MEMS resonators

Measuring shifts in eigenstates caused by vibration localization in an array of weakly coupled resonators offers 2 distinct advantages for sensor applications compared with the technique of simply measuring resonant frequency shifts: 1) orders of magnitude enhancement in parametric sensitivity; and 2) intrinsic common mode rejection. In this paper, we experimentally demonstrate the common mode rejection in weakly coupled MEMS resonators with significant potential implications for sensor applications. The vibration behavior is studied in pairs of nearly identical MEMS resonators that are electrically coupled and subjected to small perturbations in stiffness under different ambient pressure and temperature. The shifts in the eigenstates for the same parametric perturbation in stiffness are experimentally demonstrated to be more than 3 orders of magnitude greater than corresponding resonant frequency variations. They are also shown to remain relatively constant to variations in ambient temperature and pressure. This increased relative robustness to environmental drift, along with the advantage of ultra-high parametric sensitivity, opens the door to an alternative approach to achieving higher sensitivity and stability in micromechanical sensors.