Extraordinary Enhancement Research Articles

Dispersion of Multi-Walled Carbon Nanotubes Using Polyvinylpyrrolidone for Application in Cement - Based Composites to Enhance Electrical Conductivity

The purpose of this study is to analyse the effective method of dispersion of MWCNTs for the application in cement-based composites. Efficient dispersion of Carbon Nanotubes (CNTs) is one of the most challenging and crucial aspects for the application in cement-based composite. In this study, two different CNTs, pristine and functionalized (p-MWCNTs and f-MWCNTs) were dispersed in de-ionized water using different surfactants, Polyvinylpyrrolidone (PVP k-30 and PVP k-90) & Sodium Dodecyl Sulfate (SDS) and conducted a comparative investigation of the effects. Dispersion using an ultrasonic, treatment with surfactant and integrated method of both were analysed. The influence of CNTs dispersion on the electrical conductivity of the aqueous solution and to cement composites has been studied. Among the surfactant used PVPk-30 provide the best-dispersing effect while PVPk-30+SDS shows an extraordinary enhancement of conductivity of an aqueous solution. Analysis of electrical conductivity of Various % CNTs’ loaded specimen (0,0.001,0.003,0.025 wt.%) with different curing period (3,7,14,21,28 days) showed that the electrical resistivity decreases with CNTs’ loading. Dispersion effect of surfactant on p-MWCNTs and f-MWCNTs has been characterized by Ultraviolet-visible Spectroscopy (UV-Vis) and electrical resistivity measurement is carried for investigation and comparison on enhancement of electrical conductivity.

Surface plasmon dispersion engineering for optimizing scattering, emission, and radiation properties on a graphene spherical device.

We present a dispersion engineering method based on the rigorous electromagnetic theory to study the scattering properties of a double graphene layer spherical structure. The localized surface plasmons (LSPs) supported by the structure provide resonance channels that lead to an enhancement of the electromagnetic cross section. The method is used to find conditions under which two different multipolar LSP resonances occur at the same frequency value. The superscattering feature under these conditions is revealed by an extraordinary enhancement of the scattering cross section when the structure is illuminated by a plane wave field. Moreover, by studying the behavior of a single emitter localized near the graphene sphere, we show that the spontaneous emission and radiation efficiencies are also largely enhanced when the two different LSP resonances overlap.

Improved piezoelectric properties of PLA/PZT hybrid composite films

Piezoelectric polymer-ceramic composites are promising materials for Sensing, Wireless electronics and actuating applications. We report the fabrication of highly piezoelectric biocompatible films containing lead zirconate titanate (PZT) ferroelectric ceramic particles dispersed in poly lactic acid (PLA) with different volume fractions using a solvent cast technique. The properties of the piezoelectric polymer-ceramic films were investigated by Fourier transform infrared spectrometry (FTIR) and field emission scanning electron microscopy (FE-SEM). In the FTIR spectra appear a large number of absorption bands which are attributed to the phases from PLA matrix confirming the total embedding of PZT filler into the matrix. The SEM results showed a good distribution of fillers in the matrix. We find that the added PZT imposes a significant effect on the α–β phase transformation. Our finding can lead to extraordinary enhancement of piezoelectric properties for the PLA/PZT composite films. Keywords: Piezoelectric polymer-ceramic, PLA, PZT, solvent cast technique.

Electrostabilized homogeneous dispersion of boron nitride nanotubes in wide-range of solvents achieved by surface polarity modulation through pyridine attachment

Boron nitride nanotubes (BNNTs) show exceptional physical properties including high mechanical strength and thermal conductivity; however, their applications have been restricted due to limited dispersibility in processing solvents. Here, a novel BNNT dispersion method with exceptional dispersibility in a wide range of solvents has been demonstrated by surface polarity modulation through short-molecule pyridine attachment. Nitrogen atoms in pyridine are selectively bonded to electron-deficient boron atoms of the BNNT surface through Lewis acid-base reaction, which changes the surface polarity of BNNTs from neutral to negative. Re-dispersing pyridine-attached BNNTs (Py-BNNTs) create a thick and stable electronic double layer (EDL), resulting in uniform dispersion of BNNTs in solvents with an exceptional solubility parameter range of 18.5–48 MPa1/2. The uniform dispersion of BNNTs is maintained even after the mixing with diverse polymers. Finally, composites incorporating uniformly-distributed BNNTs have been realized, and extraordinary property enhancements have been observed. The thermal conductivity of 20 wt.% Py-BNNT/epoxy composite has been significantly improved by 69.6% and the tensile strength of 2 wt.% Py-BNNT/PVA has been dramatically improved by 75.3%. Our work demonstrates a simple and facile route to dispersing BNNTs in diverse solvents, consequently leading to selective utilization of BNNT dispersed solvents in various application fields.

Gold Nanorod Array-Bridged Internal-Standard SERS Tags: From Ultrasensitivity to Multifunctionality.

Bimetallic gold core-silver shell (Au@Ag) surface-enhanced Raman scattering (SERS) tags draw broad interest in the fields of biological and environmental analysis. In reported tags, silver coating tended to smooth the surface and merge the original hotspot of Au cores, which was disadvantageous to signal enhancement from the aspect of surface topography. Herein, we developed gold nanorod (AuNR)-bridged Au@Ag SERS tags with uniform three-dimensional (3D) topography for the first time. This unique structure was achieved by selecting waxberry-like Au nanoparticles (NPs) as cores, which were capped by vertically oriented AuNR arrays. Upon selective surface blocking with thiol-ligands, Ag NPs were controlled to anisotropically grow on the tips of the AuNRs, producing high-density homo- (Ag-Ag) and hetero- (Au-Ag) hotspots in a single NP. The 3D hotspots rendered this NP extraordinary SERS enhancement ability (an analytical enhancement factor of 3.4 × 106) 30 times higher than the counterpart with a smooth surface, realizing signal detection from a single NP. More importantly, multiplexing signals ("blank" or multiplex "internal standard") can be achieved by simply changing thiol-ligands, as exemplified in the synthesis of NPs with 8 signatures. Furthermore, the multifunctionality has been demonstrated in living cell/in vivo imaging, photothermal therapy, and SERS substrates for ratiometric quantitative analysis, relying on the inherent internal standard signal. The prepared Au@Ag NPs have great potential as standard tools in many SERS-related fields.

Extraordinary enhancement of a 5-fluorouracil electrode by praepagen HY micellar solutions

Being able to incorporate 16 drug molecules in a micelle, alkyl hydroxyethyl dimethyl ammonium chloride (Praepagen HY), a surfactant, showed a distinct improvement in the performance of electrodes for determination of the anticancer: 5-flourouracil (abbreviated FU). Praepagen HY can bring in this number of drug molecules into action where they are needed. This was attained by dissolving the samples in a praepagen HY utilizing a few carbon paste electrodes comprising derivatives of FU, namely FU-DAP, FU-DUL and FU-VAR designated S1, S2 and S3 respectively. Thus, the presently fabricated sensors developed competitive properties which make them strongly attractive for determination of FU especially the first. These electrodes show Nernstian slopes of 31.6 mV, 31.7 mV and 28.6 mV per decade respectively for FU‏ ion over a wide concentration range from 6.3 × 10−6 to 1.0 × 10−2, 3.5 × 10−6 to 1.0 × 10−2, and 1.2 × 10−5 to 1.0 × 10−2 M with notably low detection limits of 3.2 × 10−6, 1.9 × 10−6 and 1.1 × 10−5 M, They show significantly fast response time (ca. 5-10 s). The present sensors show distinct selectivity toward the drug ion in comparison to other common anions. The potentiometric responses are independent of the pH of the test solution in the pH range 4.0–8.0. Practically, these sensors were satisfactorily used as indicators in potentiometric titration with S1, S2 and S3 and determination of the drug ions in pharmaceutical preparations and urine.

Multipolar terahertz absorption spectroscopy ignited by graphene plasmons

Terahertz absorption spectroscopy plays a key role in physical, chemical and biological systems as a powerful tool to identify molecular species through their rotational spectrum fingerprint. Owing to the sub-nanometer scale of molecules, radiation-matter coupling is typically dominated by dipolar interaction. Here we show that multipolar rotational spectroscopy of molecules in proximity of localized graphene structures can be accessed through the extraordinary enhancement of their multipolar transitions provided by terahertz plasmons. In particular, specializing our calculations to homonuclear diatomic molecules, we demonstrate that a micron-sized graphene ring with a nano-hole at the core combines a strong near-field enhancement and an inherently pronounced field localization enabling the enhancement of the dipole-forbidden terahertz absorption cross-section of {{rm{H}}}_{2}^{+} by 8 orders of magnitude. Our results shed light on the strong potential offered by nano-structured graphene as a robust and electrically tunable platform for multipolar terahertz absorption spectroscopy at the nanoscale.

Analysis of the Limits of the Near-Field Produced by Nanoparticle Arrays.

Periodic arrays are an exceptionally interesting arrangement for metallic nanostructures because of their ability to support collective lattice resonances. These modes, which arise from the coherent multiple scattering enabled by the lattice periodicity, give rise to very strong and spectrally narrow optical responses. Here, we investigate the enhancement of the near-field produced by the lattice resonances of arrays of metallic nanoparticles when illuminated with a plane wave. We find that, for infinite arrays, this enhancement can be made arbitrarily large by appropriately designing the geometrical characteristics of the array. On the other hand, in the case of finite arrays, the near-field enhancement is limited by the number of elements of the array that interact coherently. Furthermore, we show that, as the near-field enhancement increases, the length scale over which it extends above and below the array becomes larger and its spectral linewidth narrows. We also analyze the impact that material losses have on these behaviors. As a direct application of our results, we investigate the interaction between a nanoparticle array and a dielectric slab placed a certain distance above it and show that the extraordinary near-field enhancement produced by the lattice resonance can lead to very strong interactions, even at significantly large separations. This work provides a detailed characterization of the limits of the near-field produced by lattice resonances and, therefore, advances our knowledge of the optical response of periodic arrays of nanostructures, which can be used to design and develop applications exploiting the extraordinary properties of these systems.

Enhanced electro-optical properties of TiO2 Nanocone Arrays for ultrathin GaAs Solar cells

An antireflective coating made by TiO2 nanocone array is designed on an ultrathin multilayer GaAs substrate (the thickness of GaAs is 300 nm). The intrinsic light trapping, carrier recombination and photoconversion are simulated by a complete photoelectric simulation. The results show that the optimized light trapping design can enhance the electromagnetic resonance in active layer and lead to an extraordinary enhancement of both absorption and power conversion capabilities in GaAs solar cell. The short-circuit current density increases by 51.12%, from 12.01 mA/cm2 to 18.15 mA/cm2 and power conversion efficiency increases by 52.83%, from 11.00% to 16.81% compared to the reference benchmark.

Surface Plasmon‐Assisted Transparent Conductive Electrode for Flexible Perovskite Solar Cells

AbstractFlexible perovskite solar cells (PeSCs) possess the extraordinary potential in the applications of portable power sources and wearable electronics because of their superiorities in ease fabrication and efficient power conversion. These features are reinforced when a transparent conductive electrode with good flexibility is achieved. A unique electrode based on Ag periodic mesh (APM) perforated with hexagonal close‐packed nanoholes is proposed, showing a square resistance of ≈19.0 Ω sq−1 and optical transmittance of 66.0% in the whole visible region. PeSCs made on the optimal APM electrode with a rigid glass substrate achieve over twofold of photocurrent as compared to the counterpart on flat Ag film, resulting in a maximum power conversion efficiency of 17.06%. Experimental and theoretical characterizations indicate that the performance enhancement is mainly ascribed to the surface plasmon‐assisted extraordinary transmission enhancement and the scattering of incident light. Furthermore, the APM electrode enables PeSCs that are not only efficient but also highly flexible against bending deformation. Flexible PeSCs on plastic remain 90% of their initial efficiency after 1500 bending cycles with a bending radius of 3.0 mm. It is anticipated that the APM electrode with unique light coupling abilities provides a facile design route to achieving efficient and flexible PeSCs.

A large-area fabrication of moth-eye patterned Au/TiO2 gap-plasmon structure and its application to plasmonic solar water splitting

TiO2 is promising candidate for solar water splitting material. To enhance the insufficient absorption range of TiO2, TiO2 decorated with Au nanoparticles(AuNPs) structure have been studied intensively. This plasmonic approach can extend absorption range to visible light, but its incident photon-to-current conversion efficiency is still insufficient. Therefore, it is important to amplify surface plasmon resonance, obtained by using AuNPs. At the same time, for application to next-generation energy device, the way to improve this plasmonic effect needs to be available to large area fabrication, high reproducibility, low cost and so on. In this study, we successfully fabricated a three-dimensional (3D) moth-eye AuNP/TiO2/Au hierarchical structure for water splitting via direct printing method and deposition process. The proposed structure can effectively intensify the light–matter interaction owing to two mechanisms: Photonic mode light trapping attributed by moth-eye structure and enhanced surface plasmon resonance by gap-plasmon structure. Moth-eye structure, densely packed subwavelength-nanocone array, was easily fabricated by direct printing method. Using this moth-eye structure as a template, we effectively fabricated 3D moth-eye patterned gap-plasmon structure on 5 × 5 cm2. Compared with the two-dimensional (2D) AuNP/TiO2/Au absorber, the 3D moth-eye type absorber has higher absorption in entire 300–800 nm range. In accordance with this result, the 3D moth-eye absorber provides a photocurrent density of approximately 52.82 μA cm−2, which is approximately 2.3 times higher than that of the flat 2D TiO2/Au thin film (22.96 μA cm−2). Notably, it exhibits extraordinary enhancement of the photocurrent density—from 1.5 to 22.51 μA cm−2—in the visible range (≥420 nm).

Uwagi o istocie przestępstwa o charakterze terrorystycznym i jego karaniu. Część II

Remarks on the essence of a terrorist crime and penalty for it. Part IIThe paper is an attempt to draw attention to some of the most important aspects of the problem of terrorist crimes, a problem that is complex both in criminological sense and in terms of the legal dogma. The starting point for the reflections in Part I of the article is a historical analysis of the origins and evolution of the dogmatic and normative perception of and approach to the concept of terrorist crime — beginning with the legislation of the interwar period, through post-war provisions and ending with the regulations of the 1969 Criminal Code. The Central question of this part is an analysis of the normative form of the terrorist crime construct under Article 115 § 20 of the Criminal Code, its legal nature as well as consequences of the application of the analysed norms. The reflection of Part II of the paper encompasses issues concerning the consequences of a terrorist crime in terms of statutory and judicial penalties as well as other penal measures. In this part the author analyses, in particular, the question of extraordinary enhancement of punishment for terrorist crimes, including doubts that can be aroused in practice by the regulations concerning punishment progression applied to terrorists as well as the possibility and rules of applying other measures having an impact on the legal situation of the perpetrators of terrorist crimes.

Polarization dependent, plasmon-enhanced infrared transmission through gold nanoslits on monolayer black phosphorus

Enhanced transmission is essential in many application cases. However, as an ordinary method to enhance wave transmission, traditional extraordinary transmission based on nanohole array structures has no capability to widen its operation bandwidth. Here, we use a continuous monolayer black phosphorus film to enhance transmission through gold nanostructure arrays at the mid-infrared region. By exciting surface plasmon polaritons at the BP/gold nanostructure arrays interface, enhanced transmission over a broad range of wavelengths was theoretically demonstrated. Using finite-difference time-domain simulations, we analyzed the effects of geometric parameters on the transmission spectra and demonstrated unique polarization-dependent transmission enhancement in BP/gold silt arrays and BP/gold patch arrays, which originates from the anisotropic properties of BP. Our work provides new guidance to the design of broadband, polarization-dependent extraordinary transmission enhancement.

Evaluation of the Returned Electromagnetic Signal from Retro-reflectors in Turbid Media

We provide first-principle theoretical and numerical simulations using the coherent Transfer Matrix Approach (TMA) to describe the behavior of the three main class of the optical beacons namely phase conjugators, reflectors, and retroreflectors within a turbid medium. Our theory describes the extraordinary enhancement (about 5 dB) offered by retroreflectors compared to reflectors in our detailed experiments and shows that they effectively act as local optical phase conjugators. Moreover, the performance of retroreflectors shows little degradation for increased light incident angles in turbid media, while the performance of reflectors degrades drastically. These results may find applications for detection of the echoes of electromagnetic radiation in turbid media.

Quantum Suppression of Intramolecular Deuterium Kinetic Isotope Effects in a Pericyclic Hydrogen Transfer Reaction.

It is generally accepted that hydrogen tunneling enhances both primary and secondary H/D kinetic isotope effects (KIEs) over what would be expected under the assumptions of classical barrier transition. Previous studies have exclusively shown that the effects of tunneling upon primary H/D KIEs have been much larger than those observed for secondary H/D KIEs. Here we present a series of experimental H/D KIE results associated with the Chugaev elimination of methyl xanthate derived from β-phenylethanol over the temperature range of 180 to 290 °C. Intramolecular H/D KIEs computed according to classical transition state theory (TST) are markedly overestimated relative to experimentally measured values. Experimental intermolecular H/D KIEs and direct dynamic calculations based on canonical variational transition state theory (CVT) with small-curvature tunneling correction (SCT) reveal that this result is largely the consequence of extraordinary tunneling enhancement of the secondary H/D KIE. This unexpected behavior is examined in the context of other similar hydrogen transfer reactions.

Non-Fourier heat conduction in oil-in-water emulsions

Emulsions have widely been used in various application, e.g. in energy system as a potential second refrigerant. However, there is a lack of comprehensive study on extraordinary effective thermal conductivity enhancement in the oil-in-water (O/W) emulsions, and effects of temperature and droplet size were not considered in the widely used models of effective thermal conductivity for the O/W emulsions. In this study, non-Fourier heat conduction characteristics in the O/W emulsions were investigated experimentally. The O/W emulsions were prepared with different droplet sizes by controlling the ultrasonic processing time. The O/W emulsions containing small droplets are stable. Effective thermal conductivity of O/W emulsions nonlinearly varies with droplet size, concentration, fluid properties and temperature. Small droplet size is beneficial for effective thermal conductivity enhancement of O/W emulsions. Thermal conductivity of fluids can be enhanced significantly especially at low concentration although thermal conductivity of oil is much lower than water conductivity, which could be due to non-Fourier heat conductions in O/W emulsions. Time lag ratio less than 1 indicates that no thermal waves exist in O/W emulsions, and diffusion-dominant non-Fourier heat conduction could exist in the O/W emulsions. A new model of effective thermal conductivity, which considers effects of fluid thermosphysical properties, oil concentration, droplet size and temperature, was developed for the O/W emulsions based on the measured data. This study could be helpful for exploring the mechanisms behind extraordinary heat conductivity enhancement phenomena of oil-in-water emulsions.

Chemical Identification of Single Ultrafine Particles Using Surface-Enhanced Infrared Absorption

Due to their large impact on health and environmental safety, fine and ultrafine particles are of special importance. While infrared (IR) spectroscopy can yield important material-specific information, direct investigation of small samples or single nano-objects is impossible, due to the great mismatch between particle size and IR wavelengths. Fortunately, surface-enhanced infrared absorption spectroscopy allows detection of $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ ultrafine dust particles a few tens of nanometers in diameter. The extraordinary near-field enhancement of the IR vibrational signal is achieved using plasmonically resonant Au ``bowtie'' apertures, in which the ultrafine specks are easily trapped.

Reversible two-channel mechanochromic luminescence for a pyridinium-based white-light emitter with room-temperature fluorescence-phosphorescence dual emission.

Organic mechanochromic luminescent (ML) materials have attracted extensive interest due to their potential uses in displays, sensing, bioimaging and data storage. ML materials that distinctively respond to different mechanical stimuli are especially fascinating. A simple pyridinium-based white-light emitter (P1-PF6) exhibiting this sort of ML with room-temperature fluorescence-phosphorescence dual emission (rFPDE) was found to possess a 3.66% quantum yield. Interestingly, mechanical grinding induced phosphorescence disappearance owing to a collapse of the crystalline ordering. Grinding followed by adding a drop of ethanol resulted in an extraordinary tricolor emission switching between white, blue and pinkish orange. More interestingly, mechanical pressing induced phosphorescence enhancement, resulting in the emission color changing from white to pinkish orange. This novel phenomenon may be due to the fact that pressure facilitates a closer arrangement between adjacent molecules, thereby enhancing the intermolecular interactions. In sum, a very scarce example is herein reported. Moreover, because the pure organic pyridinium with rFPDE achieves reversible two-channel ML over a wide wavelength range, this material has potential applications in multi-dimensional sensors.

Fracture Toughness (Mode-II) of Nanostitched Composites

The properties of fracture toughness (mode-II) of nanostitched carbon/epoxy composites were investigated. The mode-II of the nanostitched structure demonstrated extraordinary enhancement considering to the control sample. It was proved that carbon nanostitching yarn in the though-the-thickness of the preform structure was adequate. The fundamental mechanism for raising the mode-II strength in the nanostitched composite was the interlayer matrix breakages predominantly as a form of shear hackle marks in where nanostitching suppressed the layer to layer opening in stitching region during crack growth. Multiwall carbon nanotubes in the matrix and filament also diminished the stress clustering perhaps as a form of friction, filaments/matrix debonding in the interlaced unit cell and filament slippage in the failed matrix zone. So, nanostitched carbon/epoxy composite showed better interlainar shear properties.

Hierarchically hydrogen-bonded graphene/polymer interfaces with drastically enhanced interfacial thermal conductance.

Interfacial thermal transport is a critical physical process determining the performance of many material systems with small-scale features. Recently, self-assembled monolayers and polymer brushes have been widely used to engineer material interfaces presenting unprecedented properties. Here, we demonstrate that poly(vinyl alcohol) (PVA) monolayers with hierarchically arranged hydrogen bonds drastically enhance interfacial thermal conductance by a factor of 6.22 across the interface between graphene and poly(methyl methacrylate) (PMMA). The enhancement is tunable by varying the number of grafted chains and the density of hydrogen bonds in the unique hierarchical hydrogen bond network. The extraordinary enhancement results from a synergy of hydrogen bonds and other structural and thermal factors including molecular morphology, chain orientation, interfacial vibrational coupling and heat exchange. Two types of hydrogen bonds, i.e. PVA-PMMA hydrogen bonds and PVA-PVA hydrogen bonds, are analyzed and their effects on various structural and thermal properties are systematically investigated. These results are expected to provide new physical insights for interface engineering to achieve tunable thermal management and energy efficiency in a wide variety of systems involving polymers and biomaterials.