Order Of Magnitude Enhancement Research Articles

Flexoelectric Engineering of Bulk Photovoltaic Photodetector.

The bulk photovoltaic effect (BPVE) offers an interesting approach to generate a steady photocurrent in a single-phase material under homogeneous illumination, and it has been extensively investigated in ferroelectrics exhibiting spontaneous polarization that breaks inversion symmetry. Flexoelectricity breaks inversion symmetry via a strain gradient in the otherwise nonpolar materials, enabling manipulation of ferroelectric order without an electric field. Combining these two effects, we demonstrate active mechanical control of BPVE in suspended 2-dimensional CuInP2S6 (CIPS) that is ferroelectric yet sensitive to electric field, which enables practical photodetection with an order of magnitude enhancement in performance. The suspended CIPS exhibits a 20-fold increase in photocurrent, which can be continuously modulated by either mechanical force or light polarization. The flexoelectrically engineered photodetection device, activated by air pressure and without any optimization, possesses a responsivity of 2.45 × 10-2 A/W and a detectivity of 1.73 × 1011 jones, which are superior to those of ferroelectric-based photodetection and comparable to those of the commercial Si photodiode.

Ultra-corrosion-resistant aluminum alloys achieved by femtosecond laser complete remediation of microarc oxidation defects

Microarc oxidation (MAO) is a widely employed technology for the corrosion protection of metal surfaces due to the formation of thick-layer ceramic substances. However, its practical effectiveness is strictly limited by the inevitable concomitant generation of numerous microscale pores/cracks on the oxidation surface to directly expose the substrate materials. As concerning this problem, we here introduced a novel method of the femtosecond laser irradiation to completely eliminate the above MAO defects on aluminum alloys, which consequently modulates the passivation layer into the dense and the superhydrophobic. Meanwhile, with the deep insights into the phase composition variations of the oxide layer, we can find that the laser treatments enable the development of both γ-Al2O3 and α-Al2O3 nanocrystallines with embedment in the amorphous substances to significantly improve the chemical stability of materials. Such laser modifications eventually result in the ultra-corrosion-resistant surface of aluminum alloys, with the measured corrosion current density of 1.46 × 10-13 A/cm2 as well as the impedance value over 112 GΩ∙cm2, about two orders of magnitude enhancement in the anticorrosion compared to the initial MAO sample.

Efficient statistical approach for thermo-electrical properties of gadolinia-doped ceria thin films

The thermo-electrical properties of gadolinia-doped ceria (GDC) thin films play a vital role in solid oxide fuel cell (SOFC) applications. Nonetheless, the effects of temperature, dopant concentration, and thickness on thermal expansion, and ionic conduction remain ambiguous. In the present study, we propose an efficient theoretical approach to emphasize the roles of surface layers and surface vicinity (called next-surface layers) on the thermo-electrical properties of GDC thin films. Using statistical moment method, thermal expansion coefficient, and ionic conductivity are calculated as functions of temperature, dopant concentration, and thickness. The lattice strain and ionic disorder in the surface and next-surface layers cause an increase in thermal expansion coefficient and ionic conductivity of thin films. Compared with bulk GDC, the thermal expansion coefficient is slightly larger while the ionic conductivity is more than one to two orders of magnitude enhancement and exhibits the maximum value at the higher concentration. The ionic conductivity depends non-linearly on the dopant concentration and the maximum conductivity is shifted toward a higher value as the temperature increases. The enhancement in thermal expansion coefficient and ionic conductivity offers new opportunities for SOFC electrolytes whose efficiency can be effectively controlled by tailoring the thickness. The theoretical calculations are compared to measured results from experiments.

Large area single crystal gold of single nanometer thickness for nanophotonics

Two-dimensional single crystal metals, in which the behavior of highly confined optical modes is intertwined with quantum phenomena, are highly sought after for next-generation technologies. Here, we report large area (>104 μm2), single crystal two-dimensional gold flakes (2DGFs) with thicknesses down to a single nanometer level, employing an atomic-level precision chemical etching approach. The decrease of the thickness down to such scales leads to the quantization of the electronic states, endowing 2DGFs with quantum-confinement-augmented optical nonlinearity, particularly leading to more than two orders of magnitude enhancement in harmonic generation compared with their thick polycrystalline counterparts. The nanometer-scale thickness and single crystal quality makes 2DGFs a promising platform for realizing plasmonic nanostructures with nanoscale optical confinement. This is demonstrated by patterning 2DGFs into nanoribbon arrays, exhibiting strongly confined near infrared plasmonic resonances with high quality factors. The developed 2DGFs provide an emerging platform for nanophotonic research and open up opportunities for applications in ultrathin plasmonic, optoelectronic and quantum devices.

Enhanced structural, electrical, and electrochemical performance of polyethylene oxides (PEO)‐based polymer electrolytes for solid state K+ ion batteries

AbstractFlexible polymer electrolytes with effective electrochemical characteristics must be developed to meet smart electronic technology demands. The current investigation explores the solid polymer electrolytes (SPEs) prepared by solution‐casting technique, using polyethylene oxides (PEO) doped with KCl salt in different weight percentages. The effect of the dopant on the chemical interactions and structural, optical, thermal, electrical, and electrochemical properties were studied using various strategies. It was found that the incorporation of KCl salt to PEO results in a three order of magnitude enhancement in ionic conductivity of polymer matrix from 10−9 to 10−6 S cm−1. The PEO doped with 20 wt.% KCl salt exhibited the highest ionic conductivity (4.32 × 10−6 S cm−1) and low activation energy (0.25 eV). According to the thermal analysis, the thermal stability of the films improved as the dopant concentration increased. Further, the electrochemical strength improved with increasing dopant concentration, according to cyclic voltammogram experiments. From the results of all the characterizations, PEO loaded with 20 wt.% KCl SPE system is a suitable candidate for use as an electrolyte in energy storage devices such as solid‐state batteries.

Direct Analysis of Whole Blood by a Disposable Monolithic Column Mass Spectrometry Analysis Kit†

Comprehensive SummaryA monolithic column‐based mass spectrometry (MS) analysis kit was prepared for whole blood analysis with MS. The kit is disposable and can be used for purification, storage, transportation and direct analysis of whole blood. The kit mainly consists of a capillary for quantitative microsampling, a cation exchange monolithic column for purification and storage, and a syringe for loading sample. This kit is very friendly to various users that one can easily siphon the blood in the kit followed by rapid clean‐up. We established a quantitative method using the kit with a limit detection as low as 0.33 nmol/L, and achieved more than five orders of magnitude enhancement in sensitivity compared to direct nanoelectrospray ionization MS analysis. The column can avoid analyte exposure to environment, which helps the storage of the sample for laboratory analysis. The relative standard deviation of immediate blood analysis and storage blood analysis within 10 d was less than 10%. This method has been successfully applied to the quantitative analysis of procainamide hydrochloride in 2 μL rat blood. These results indicate that this disposable kit does have the potential to achieve highly sensitive quantitative MS analysis in biological samples, which is expected to become a cost‐effective and powerful tool for in vitro diagnostics.

Evaporation Triboelectric‐Nanogenerator: Harvesting Low‐Grade Heat Energy from Ambient Environment

AbstractAlthough natural evaporation absorbs substantial thermal energy from the ambient environment, efficiently utilizing this high‐entropy energy remains challenging. Here, the first water evaporation‐induced triboelectric nanogenerator is proposed. It only uses tap water to harvest low‐grade heat energy from the surroundings to convert it into electricity. The natural evaporation of the liquid can generate unintermittent electricity with an open‐circuit voltage of 382 V, a peak power of 0.42 mW, and three orders of magnitude enhancement up to 59.7 mJ mL−1 after consuming the same amount of tap water compared with the droplet‐based electricity generators. After which, the excellent power output lights 2 W LED and drives wearable electronic devices. This device also inhibits carbon steel materials' corrosion in solutions through the evaporation effect of the salt water on the spot. The present study provides novel insights for triboelectric nanogenerators regarding energy sources and promotes the practical application of evaporation‐power generation technology.

Improving the Laser-Induced Breakdown Spectroscopy for Highly Efficient Trace Measurement of Hazardous Components in Waste Oils.

Improper disposal of waste oils containing hazardous components damages the environment and the ecosystem, posing a significant threat to human life and health. Here, we present a method of discharge-assisted laser-induced breakdown spectroscopy combined with filter paper sampling (DA-LIBS-FPS) to detect hazardous components and trace the source of polluting elements. DA-LIBS-FPS significantly enhances spectral intensity by 1-2 orders of magnitude due to the discharge energy deposition into the laser-induced plasma and the highly efficient laser-sample interaction on the filter paper, when compared to single-pulse LIBS with silica wafer sampling (SP-LIBS-SWS). Additionally, the signal-to-noise ratio and the signal-to-background ratio are both significantly increased. Resultantly, indiscernible lines, such as CN and Cr I, are well distinguished. In contrast with DA-LIBS combined with silica wafer sampling (DA-LIBS-SWS), the spectral signal fluctuations in DA-LIBS-FPS are reduced by up to 33%, because of the homogeneous distribution of the oil layer on the filter paper in FPS. Further examination indicates that the limit of detection for Ba is reduced from a several parts per million level in SP-LIBS-SWS to a dozens of parts per billion level in DA-LIBS-FPS, i.e., nearly 2 orders of magnitude enhancement in analysis sensitivity. This improvement is attributed to the extended plasma lifespan in DA-LIBS and the increasing electron density and plasma temperature in FPS. DA-LIBS-FPS provides a low-cost, handy, rapid, and highly sensitive avenue to analyze the hazardous components in waste oils with great potential in environmental and ecological monitoring.

An order of magnitude enhancement in ductility of a metallic glass of peak rejuvenation

Exceptional ductility has been a long-sought-after property of metallic glasses, and cryogenic thermal cycling rejuvenation has been actively explored to enhance the plasticity of metallic glasses. By tuning the holding time and number of cycles of cryogenic thermal cycling processing, we here report a (Zr0.8125Cu0.1875)79Ni10Al10Nb1 metallic glass of peak rejuvenation with the plasticity of an order of magnitude higher than that of the as-cast glass, without sacrificing its strength. Characterizations indicate that the loose atomic packing of the metallic glass of peak rejuvenation facilitates the generation and proliferation of shear bands in the early stage of plastic deformation, and the resultant dense shear bands tend to be deflected due to their interaction with each other and/or structural inhomogeneity in the matrix, hindering their rapid propagation and in turn increasing the plasticity. The combination of high relaxation enthalpy and high plasticity obtained here is outstanding from the previous rejuvenated metallic glasses which have either high relaxation enthalpy or high plasticity, while never both. This work identifies an alloy system with very high efficiency in plasticity improvement through cryogenic thermal cycling rejuvenation and represents a promising guide for improving the plasticity of metallic glasses.

Imaging Strain-Localized Single-Photon Emitters in Layered GaSe below the Diffraction Limit.

Nanoscale strain control of exciton funneling is an increasingly critical tool for the scalable production of single photon emitters (SPEs) in two-dimensional materials. However, conventional far-field optical microscopies remain constrained in spatial resolution by the diffraction limit and thus can provide only a limited description of nanoscale strain localization of SPEs. Here, we quantify the effects of nanoscale heterogeneous strain on the energy and brightness of GaSe SPEs on nanopillars with correlative cathodoluminescence, photoluminescence, and atomic force microscopy, supported by density functional theory simulations. We report the strain-localized SPEs have a broad range of emission wavelengths from 620 to 900 nm. We reveal substantial strain-controlled SPE wavelength tunability over a ∼100 nm spectral range and 2 orders of magnitude enhancement in the SPE brightness at the pillar center due to Type-I exciton funneling. In addition, we show that radiative biexciton cascade processes contribute to observed CL photon superbunching. Also, the GaSe SPEs show excellent stability, where their properties remain unchanged after electron beam exposure. We anticipate that this comprehensive study on the nanoscale strain control of two-dimensional SPEs will provide key insights to guide the development of truly deterministic quantum photonics.

Efficient angular dispersed high-order harmonic generation by dual laser pulses interacting with a solid target

High-order harmonics emitted from relativistic laser–solid interaction can be used as a bright extreme ultraviolet source. However, such a source usually has mixed frequencies along the emission direction. Through theoretical and numerical studies, we propose a scheme to realize monochromatic harmonic emission along individual directions by using dual laser pulses with orthogonal polarizations, where a relativistic P-polarized laser is used as a pump laser in combination with a moderate S-polarized laser as a seed laser. We find that harmonics of the S-polarized laser can be efficiently generated with several orders of magnitude enhancement and spontaneous angular dispersion depending on the harmonic order. Our scheme may be beneficial to future applications requiring monochromatic radiation along a specific direction or multi-chromatic radiations in different directions.

M13 Bacteriophage-Assisted Recognition and Signal Spatiotemporal Separation Enabling Ultrasensitive Light Scattering Immunoassay.

The demand for the ultrasensitive and rapid quantitative analysis of trace target analytes has become increasingly urgent. However, the sensitivity of traditional immunoassay-based detection methods is limited due to the contradiction between molecular recognition and signal amplification caused by the size effect of nanoprobes. To address this dilemma, we describe versatile M13 phage-assisted immunorecognition and signal transduction spatiotemporal separation that enable ultrasensitive light-scattering immunoassay systems for the quantitative detection of low-abundance target analytes. The newly developed immunoassay strategy combines the M13 phage-assisted light scattering signal fluctuations of gold nanoparticles (AuNPs) with gold in situ growth (GISG) technology. Given the synergy of M13 phage-mediated leverage effect and GISG-amplified light scattering signal modulation, the practical detection capability of this strategy can achieve the ultrasensitive and rapid quantification of ochratoxin A and alpha-fetoprotein in real samples at the subfemtomolar level within 50 min, displaying about 4 orders of magnitude enhancement in sensitivity compared with traditional phage-based ELISA. To further improve the sensitivity of our immunoassay, the biotin-streptavidin amplification scheme is implemented to detect severe acute respiratory syndrome coronavirus 2 spike protein down to the attomolar range. Overall, this study offers a direction for ultrasensitive quantitative detection of target analytes by the synergistic combination of M13 phage-mediated leverage effect and GISG-amplified light scattering signal modulation.

Nonlinear THz Generation through Optical Rectification Enhanced by Phonon-Polaritons in Lithium Niobate Thin Films.

We investigate nonlinear THz generation from lithium niobate films and crystals of different thicknesses by optical rectification of near-infrared femtosecond pulses. A comparison between numerical studies and polarization-resolved measurements of the generated THz signal reveals a 2 orders of magnitude enhancement in the nonlinear response compared to optical frequencies. We show that this enhancement is due to optical phonon modes at 4.5 and 7.45 THz and is most pronounced for films thinner than 2 μm where optical-to-THz conversion is not limited by self-absorption. These results shed new light on the employment of thin film lithium niobate platforms for the development of new integrated broadband THz emitters and detectors. This may also open the door for further control (e.g., polarization, directivity, and spectral selectivity) of the process in nanophotonic structures, such as nanowires and metasurfaces, realized in the thin film platform. We illustrate this potential by numerically investigating optical-to-THz conversion driven by localized surface phonon-polariton resonances in sub-wavelength lithium niobate rods.

Ion Steric Effect Induces Giant Enhancement of Thermoelectric Conversion in Electrolyte-Filled Nanochannels.

Ionic thermoelectricity in nanochannels has received increasing attention because of its advantages, such as high Seebeck coefficient and low cost. However, most studies have focused on dilute simple electrolytes that neglect the effects of finite ion sizes and short-range electrostatic correlation. Here, we reveal a new thermoelectric mechanism arising from the coupling of the ion steric effect due to finite ion sizes and ion thermodiffusion in electric double layers, using both theoretical and numerical methods. We show that this mechanism can significantly enhance the thermoelectric response in nanoconfined electrolytes depending on the properties of electrolytes and nanochannels. Compared to the previously known mechanisms, the new mechanism can increase the Seebeck coefficient by 100% or even 1 order of magnitude enhancement under optimal conditions. Moreover, we demonstrate that the short-range electrostatic correlation can help preserve the Seebeck coefficient enhancement in a weaker confinement or in more concentrated electrolytes.

Annealing-induced one order of magnitude enhancement in heat dissipation at graphene/SiO2 interface

The potential applications of two-dimensional (2D) materials-based devices in various fields have garnered significant interest. However, the limited heat transfer efficiency across the interface between 2D materials and the substrate has impeded their widespread application. This study presents a novel approach to enhancing the interface thermal transport of a widely used graphene/substrate structure through repeated annealing. Using Raman thermometry, we measured the interface thermal resistance (R) at 9.51 × 10−5 m2 K/W, which was subsequently reduced by an order of magnitude to 5.00 × 10−6 m2 K/W after repeated annealing. Our experimental results, supported by atomic modeling, revealed the significant influence of wrinkles on the interface thermal transport. Atomic force microscopy (AFM) images vividly illustrate the modulation of the surface structure due to repeated annealing, with the initial loose structure becoming tighter and the wrinkle flattened. Further phonon transport analysis revealed a significantly reduced phonon coupling rate between graphene and SiO2 due to the presence of wrinkles in the graphene. Our findings highlight the feasibility of annealing as a means of manipulating interface thermal transport and provide insights into the underlying mechanism, which may inspire further studies on enhancing thermal interface properties.

Sodium enhancement in evolved cataclysmic variables

ABSTRACT We present follow-up spectroscopy of 21 cataclysmic variables (CVs) with evolved secondaries and ongoing or recently terminated mass transfer. Evolutionary models predict that the secondaries should have anomalous surface abundances owing to nuclear burning in their cores during their main-sequence evolution and subsequent envelope stripping by their companion white dwarfs. To test these models, we measure sodium (Na) abundances of the donors from the Fraunhofer ‘D’ doublet. Accounting for interstellar absorption, we find that all objects in our sample have enhanced Na abundances. We measure 0.3 dex ≲ [Na/H] ≲ 1.5 dex across the sample, with a median [Na/H] = 0.956 dex, i.e. about an order of magnitude enhancement over solar values. To interpret these values, we run Modules for Experiments in Stellar Astrophysics binary evolution models of CVs in which mass transfer begins just as the donor leaves the main sequence. These generically predict Na enhancement in donors with initial donor masses $\gtrsim 1\, {\rm M}_{\odot }$, consistent with our observations. In the models, Na enrichment occurs in the donors’ cores via the NeNa cycle near the end of their main-sequence evolution. Na-enhanced material is exposed when the binaries reach orbital periods of a few hours. Donors with higher initial masses are predicted to have higher Na abundances at fixed orbital period owing to their higher core temperatures during main-sequence evolution. The observed [Na/H] values are on average ≈0.3 dex higher than predicted by the models. Surface abundances of evolved CV donors provide a unique opportunity to study nuclear burning products in the cores of intermediate-mass stars.

Hybrid Polypyrrole and Polydopamine Nanosheets for Precise Raman/Photoacoustic Imaging and Photothermal Therapy.

The development of near-infrared light (NIR)-responsive conductive polymers provides a useful theranostic platform for malignant tumours by maximizing spatial resolution with deep tissue penetration for diagnosis and photothermal therapy. Herein, we demonstrated the self-assembly of ultrathin two-dimensional (2D) polypyrrole nanosheets utilizing dopamine as a capping agent and a monolayer of octadecylamine as a template. The 2D polypyrrole-polydopamine nanostructure (DPPy) had tunable size distribution which showed strong absorption in the first and second near-infrared windows, enabling photoacoustic imaging and photothermal therapy. The hybrid double-layer was demonstrated to increase Raman intensity for 3D Raman imaging (up to two orders of magnitude enhancement and spatial resolution up to 1μm). The acidic environment drove reversible doping of polypyrrole, which could be detected by Raman spectroscopy. The combined properties of the nanosheets could substantially enhance performance in dual-mode Raman and photoacoustic guided photothermal therapy, as shown by the 69% light to heat conversion efficiency and higher cytotoxicity against cancer spheroids. These pH-responsive features highlight the potential of 2D conductive polymers for applications in accurate, highly efficient theranostics. This article is protected by copyright. All rights reserved.

Modelling and performance analysis of a novel thermophotovoltaic system with enhanced radiative heat transfer for combined heat and power generation

Solid-state energy conversion technologies such as thermophotovoltaics (TPV) have attracted much interest recently in the development of high-performance combined heat and power generation (CHP) systems because of the merits such as vibration-free operation, long working life, and versatile fuel source. However, current work is limited in power density, system efficiency, and power to heat generation ratio that are constrained by the device structure and working principle of existing techniques. In this work, we propose to apply zero-gap TPV (zTPV) to create a new type of CHP system that can potentially address the limitations in existing systems. zTPV, different from conventional TPV with a vacuum or gas-filled gap between the thermal emitter and photovoltaic cell, possesses an infrared-transparent intermediate solid layer. Our theoretical analysis, combining electromagnetic, thermal, and power generation modelling in zTPV, has confirmed that an one-order-of-magnitude higher thermal radiation dictates the energy conversion in zTPV. The significantly higher thermal radiation is due to the energy transfer of low-loss high-wavevector electromagnetic modes. In conventional TPVs, these modes are not allowed to transport in the gap, and thus not able to contribute to energy conversion. In contrast, the inserted infrared transparent layer allows the transport of these high-density modes, leading to much higher power density (over one order of magnitude enhancement), higher power conversion efficiency (nearly 25% improvement), and high power to heat ratio that is relevant to the system efficiency improvement in CHP applications. The novel device configuration of zTPV allows us to propose a hybrid CHP design that integrates zTPV with thermoelectric (TE) arrays into an ultra-compact CHP device. The effect of different system parameters is modelled and analyzed to demonstrate the high performance of the hybrid CHP.

Analyte enrichment and sensitive detection over nanosecond laser textured stainless steel superhydrophobic surfaces

In this report, we have investigated the use of nanosecond laser texturing produced superhydrophobic surfaces for enrichment and sensitive detection of analytes. We have shown that by carefully choosing the laser processing parameters, the superhydrophobic surfaces capable of maintaining a small (5 μL) aqueous droplet in spherical shape till the last stage of evaporation and hence enabling the droplet to deposit its entire content over ∼80–100 μm size residual spot upon complete evaporation, can be prepared. The spot was found to get formed by bridging over the micro structures suggesting that the droplet remained suspended over the structures i.e. did not penetrate the structures till the very end of the evaporation process. By performing fluorescence spectroscopy of the residual spot, Rhodamine 6G could be detected at an ultra-low concentration of 10−18 molL−1 in a 5 μL water droplet. When compared with the results obtained on unprocessed stainless steel substrate, these superhydrophobic steel surfaces were found to provide four orders of magnitude enhancement in the lowest detectable concentration of Rhodamine 6G.

Organic electrochemical transistors as on-site signal amplifiers for electrochemical aptamer-based sensing

Electrochemical aptamer-based sensors are typically deployed as individual, passive, surface-functionalized electrodes, but they exhibit limited sensitivity especially when the area of the electrode is reduced for miniaturization purposes. We demonstrate that organic electrochemical transistors (electrolyte gated transistors with volumetric gating) can serve as on-site amplifiers to improve the sensitivity of electrochemical aptamer-based sensors. By monolithically integrating an Au working/sensing electrode, on-chip Ag/AgCl reference electrode, and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) counter electrode — also serving as the channel of an organic electrochemical transistor— we can simultaneously perform testing of organic electrochemical transistors and traditional electroanalytical measurement on electrochemical aptamer-based sensors including cyclic voltammetry and square-wave voltammetry. This device can directly amplify the current from the electrochemical aptamer-based sensor via the in-plane current modulation in the counter electrode/transistor channel. The integrated sensor can sense transforming growth factor beta 1 with 3 to 4 orders of magnitude enhancement in sensitivity compared to that in an electrochemical aptamer-based sensor (292 μA/dec vs. 85 nA/dec). This approach is believed to be universal, and can be applied to a wide range of tethered electrochemical reporter-based sensors to enhance sensitivity, aiding in sensor miniaturization and easing the burden on backend signal processing.