The inherent unpredictability of physical property randomness holds great promise for information security applications. A novel encryption approach is devised based on the optoelectronic responses of conducting domain walls (CDWs) in BiFeO3 thin films, integrating nonlinear transformations with true random secret keys to enhance the overall security. The plaintext is defined by the wavelength-dependent photocurrents at 405, 520 and 635 nm optical excitations and the distortions in each RGB channel are introduced by additional electrical pulsing. The nonlinear transformation makes the characteristic pattern hidden, increasing the image entropy from 2.59 to 6.83. The encryption is then conducted by true random secret keys generated by the stochastic fluctuations of domain wall currents (DWCs) to implement logical encryption operations. The image entropy is further increased to 7.95 with the transition of correlation plots from strong correlations between pixels to aperiodic characteristic pattern. The encryption shows high resistances to attacks by exhaustive method and quantum search, logarithmically extending cracking time with key length bits. The robustness of the scheme is verified by typical differential attacks, noise additions and occlusion interruptions. The approach conveniently embeds a two-step encryption in the optoelectronic responses of conducting domain walls, providing a proof-ofconcept solution for data security in AI and IoT.

Suppression of crystalline Li15Si4 in silicon-carbon composite anode in lithium ion battery was achieved in electrochemical half-cells with an active material composed of 60 % nanosilicon, 20 % conductive carbon and 20 % P84 binder, and lithium metal counter/reference electrode. The half-cells were cycled between 1.5 V and 50 mV, the latter being the discharge voltage when crystalline Li15Si4 was found to form. Following this, the same cells were cycled between 1.5 V and 10 mV. A third set of cycling was carried out on the cells between 1.5 V and 5 mV. The gravimetric capacity was 1000 mAh/g after ninety cycles with the 50 mV discharge cutoff, 450 mAh/g after 200 additional cycles with 10 mV cutoff, and 300 mAh/g after 200 additional cycles with 5 mV cutoff. Unlike previous reports that showed precipitous drop of capacity accompanied by the formation of crystalline Li15Si4 the capacity drop in these cells was gradual. Cyclic voltammetry measurements carried out on the halfcells demonstrate the absence of sharp delithiation peak at 0.42 V that has been shown to indicate crystalline Li15Si4 formation. We provide supporting arguments of such absence of crystalline Li15Si4 via X-ray diffraction, Raman spectroscopy, field effect scanning electron microscopy/energy dispersive X-ray spectroscopy.

Deriving battery grade materials from natural sources is a key element to establishing sustainable energy storage technologies. In this work, we present the use of avocado peels as a sustainable source for conversion into hard carbon based anodes for sodium ion batteries. The avocado peels are simply washed and dried then proceeded to a high temperature conversion step. Materials characterization reveals conversion of the avocado peels in high purity, highly porous hard carbon powders. When prepared as anode materials they show to the capability to reversibly store and release sodium ions. The hard carbon-based electrodes exhibit excellent cycling performance, namely, a reversible capacity of 352.55 mAh/g at 0.05 A/g, rate capability up to 86 mAh/g at 3500 mA/g, capacity retention of >90%, and 99.9% coulombic efficiencies after 500 cycles. This study demonstrates avocado derived hard carbon as a sustainable source that can provide excellent electrochemical and battery performance as anodes in sodium ion batteries.

Electrochemical ion storage behaviors of Fe3O4 nanoparticles, as a representative transition metal oxide for an environmentally benign and low-cost anode for a sodium-ion battery, are thoroughly investigated through a combination of electrochemical analysis and diagnostics of Fe3O4 electrode cells, X-ray-based and spectroscopic analysis of material structure evolution as functions of depth of discharge (DoD) and state of charge (SoC), and first principle modeling. The gravimetric capacity is found to be 50 mA h/g for bulk Fe3O4 (50 nm average crystallite size) and 100 mA h/g─about a tenth of the theoretical prediction for complete conversion─for Fe3O4 nanoparticles (8.7 nm average particle size), respectively. A fundamental and mechanistic study of material evolution as functions of DoD and SoC shows that Fe3O4 does not allow electrochemical incorporation of Na+ ions into the empty cation positions of the inverse spinel structure, leading to our assertion that electrochemical intercalation of Na+ ions to conversion of the Fe3O4 anode in sodium-ion batteries is nonviable. A density functional theory investigation points to the impracticality of the intercalation of Na+ ions into Fe3O4 and further validates our experimental findings. We propose several possible mechanisms corresponding to the observed low capacity, including formation of solid electrolyte interphases with unfavorable properties and adsorption of Na+ ions onto surfaces of nanoparticles and/or at heterointerfaces in Fe3O4 composite electrodes in a NaPF6-based electrolyte system.

A dc electric field is used to attract thermally charged CdSe nanocrystals in solution to rapidly form large-area, micron-thick films of equal thickness on both electrodes. A pair of Au-on-Si or conducting ITO-on-glass electrodes was submerged in the nanoparticle solution and a dc voltage was applied in a dark room. Uniform, robust, very smooth, and apparently identical films formed on both electrodes. Photoluminescence and absorption of the films showed that they are indeed made of dense arrays of individual nanocrystals. The deposition implies there are both positively and negatively thermally. charged dots in solution. These high quality dense arrays of the nanoparticles could be useful in several applications.

Introduction Current NICE guidelines recommend early invasive strategy with coronary angiography within 72 hours of first presentation of NSTEMI to those who have an intermediate or higher risk of adverse cardiovascular events, defined as a GRACE 2.0 risk greater than 3.0%. The aim of this audit is to explore NICE guideline adherence, patient characteristics and clinical outcomes. Methods Retrospective data from patients with a final diagnosis of NSTEMI in the months of October 2018 and January 2019 was gathered from clinical coding. Patients were stratified by their GRACE 2.0 score, which was retrospectively calculated using their clinical notes and investigations on the Integrated Clinical Environment. Results There were 116 patients of which 90 (77.6%) had an intermediate to high risk. Data was analysed for all the 90 patients (table 1) with further analysis for those who underwent early or late inpatient coronary angiography with fisher’s exact test (table 2). From the 90 patients 44 (48.9%) underwent coronary angiography, while 46 patients (51.1%) were not suitable for invasive intervention hence treated with standard medical therapy. 18 patients (40.9%) had coronary angiography within 72 hours and 26 waited more than 72 hours. 13 (72.2%) of those who had early coronary angiography went on to have percutaneous coronary intervention compared to the 10 (38.5%) patients who had delayed coronary angiography (p=0.0018). Conclusion Despite expectations there was only 40.9% adherence to NICE guideline. In contrast to expectations intermediate to high-risk patients are less likely to have early invasive strategy. However, there is no difference in outcome between an early versus late invasive strategy for inpatients. Standard medical treatment is still practiced at higher number of patients with multiple comorbidities, higher age and intermediate to high risk. This shows that meeting NICE recommendations can be challenging for numerous factors beyond a clinician’s control. Further data from medium sized district general hospitals with catheterization laboratory facility is needed to assess the overall ability of these centres to meet NICE recommendations. Conflict of Interest None

Cobalt nanoparticle thin films were electrophoretically deposited on copper current collectors and were annealed into thin films of hollow Co3O4 nanoparticles. These thin films were directly used as the anodes of lithium ion batteries (LIBs) without the addition of conducting carbons and bonding agents. LIBs thus fabricated show high gravimetric capacities and long cycle lives. For ≈1.0 μm thick Co3O4 nanoparticle films the gravimetric capacities of the batteries were more than 800 mAh g−1 at a current rate of C/15, which is about 90% of the theoretical maximum. Additionally, the batteries were able to undergo 200 charge/discharge cycles at a relatively fast rate of C/5 and maintain 50% of the initial capacity. In order to understand the electrochemistry of lithiation in the context of nanoparticles, Raman spectra were collected at different stages of the electrode cycles to determine the chemical and structural changes in the nanomaterials. Our results indicate that initially the electrode nanoparticles were under significant strain and as the battery underwent many cycles of charging/discharging the nanoparticles experienced progressive strain relaxation.

Coupling of switchable ferroelectric polarization with the carrier transport in an adjacent semiconductor enables a robust, non-volatile manipulation of the conductance in a host of low-dimensional systems, including the two-dimensional electron liquid that forms at the LaAlO3 (LAO)-SrTiO3 (STO) interface. However, strength of the gate-channel coupling is relatively weak, limited in part by the electrostatic potential difference across a ferroelectric gate. Here, through application of phenomenological Landau-Ginzburg-Devonshire theory and self-consistent Poisson-Schrödinger model calculations, we show how compositional grading of PbZr1−xTixO3 ferroelectric gates enables a more than twenty-five-fold increase in the LAO/STO channel conductance on/off ratios. Incorporation of polarization gradients in ferroelectric gates can enable breakthrough performance of ferroelectric non-volatile memories.

We report intense, narrow line-width, surface chemisorption-activated and reversible ultraviolet (UV) photoluminescence from radiative recombination of the two-dimensional electron gas (2DEG) with photoexcited holes at LaAlO3/SrTiO3. The switchable luminescence arises from an electron transfer-driven modification of the electronic structure via H-chemisorption onto the AlO2-terminated surface of LaAlO3, at least 2 nm away from the interface. The control of the onset of emission and its intensity are functionalities that go beyond the luminescence of compound semiconductor quantum wells. Connections between reversible chemisorption, fast electron transfer, and quantum-well luminescence suggest a new model for surface chemically reconfigurable solid-state UV optoelectronics and molecular sensing.

Raman scattering in thin film La0.2Sr0.8FeO3-delta on MgO(0 0 1) collected at 300K after different stages of annealing at selected temperatures T (300 K < T < 543 K, to 10 h) and analysis reveal changes in spectral characteristics due to a loss of oxygen, onset of oxygen vacancy-induced disorder, and activation of Raman-inactive modes that are attributed to symmetry lowering. The interpretation is further supported by carrier transport measurements under identical conditions showing orders of magnitude increase in the resistivity induced by oxygen loss. After prolonged annealing in air, evolution of the spectrum signals the appearance of a possible topotactic transformation of the crystal structure from that of the rhombohedral ABO(3) perovskites to that of Brownmillerite-like structure consisting of octahedrally and tetrahedrally coordinated Fe atoms.

Carbon nanotubes combine low density with exceptional mechanical, electrical and optical properties. Unfortunately, these nanoscale properties have not been retained in bulk structures. I will describe surface modification assisted self-assembly of single wall carbon nanotube into macroscopic nanotube networks hydrogels and aerogels. The nanotube networks are ultra-lightweight, electrically conducting and thermally insulating. The shapes and sizes of these nanotube networks are readily tunable and is a tremendous strength of our fabrication method. The interesting properties and structure of these nanotube networks make them suitable for diverse applications. For example, we have used these networks as scaffolds to enhance elastic modulus of polymers by 36,000%. The porous nanotube networks also show high capacitance, and can be impregnated with catalysts nanoparticles at high loading, which can then be simultaneously used as electrodes and catalysts supports in electrochemical cells. A weakness of the nanotube networks is their fragility – but we have recently developed a method to transform these inelastic networks into superelastic materials by coating them with between one and five layers of graphene nanoplates.

Nuclear site analysis methods are used to enumerate the normal modes of ABX3 perovskite polymorphs with octahedral rotations. We provide the modes of the 14 subgroups of the cubic aristotype describing the Glazer octahedral tilt patterns, which are obtained from rotations of the BX6 octahedra with different sense and amplitude about high-symmetry axes. We tabulate all normal modes of each tilt system and specify the contribution of each atomic species to the mode displacement pattern, elucidating the physical meaning of the symmetry unique modes. We have systematically generated 705 schematic atomic displacement patterns for the normal modes of all 15 (14 rotated + 1 unrotated) Glazer tilt systems. We show through some illustrative examples how to use these tables to identify the octahedral rotations, symmetric breathing, and first-order Jahn-Teller anti-symmetric breathing distortions of the BX6 octahedra, and the associated Raman selection rules. We anticipate that these tables and schematics will be useful in understanding the lattice dynamics of bulk perovskites and could serve as a reference point in elucidating the atomic origins of a wide range of physical properties of synthetic perovskite thin films and superlattices.

In this work, we have developed a new fabrication method for nanoparticle (NP) assemblies for Li-ion battery electrodes that require no additional support or conductive materials such as polymeric binders or carbon black. By eliminating these additives, we are able to improve the battery capacity/weight ratio. The NP film is formed by using electrophoretic deposition (EPD) of colloidally synthesized, monodisperse cobalt NPs that are transformed through the nanoscale Kirkendall effect into hollow Co(3)O(4). EPD forms a network of NPs that are mechanically very robust and electrically connected, enabling them to act as the Li-ion battery anode. The morphology change through cycles indicates stable 5-10 nm NPs form after the first lithiation remained throughout the cycling process. This NP-film battery made without binders and conductive additives shows high gravimetric (>830 mAh/g) and volumetric capacities (>2100 mAh/cm(3)) even after 50 cycles. Because similar films made from drop-casting do not perform well under equal conditions, EPD is seen as the critical step to create good contacts between the particles and electrodes resulting in this significant improvement in battery electrode assembly. This is a promising system for colloidal nanoparticles and a template for investigating the mechanism of lithiation and delithiation of NPs.

The synthesis of cylindrical silicon‐core and ferroelectric oxide perovskite‐shell nanowires and their response characteristics as individual three‐terminal nanoscale electronic devices is reported. The co‐axial nanowire geometry facilitates large ferroelectric field‐effect modulation (>104) of nanowire conductivity following sequential application and removal of an applied dc field. Source‐drain current–voltage traces collected during sweeps of ferroelectric gate potential and switching of the component of shell outward and inward polarization provide direct evidence of ferroelectric coupling on nanowire channel conductance. Despite a very small (1:20) ferroelectric‐to‐semiconductor channel thickness ratio, an unexpectedly strong electrostatic coupling of ferroelectric polarization to channel conductance is observed because of the co‐axial gate geometry and curvature‐induced strain enhancement of ferroelectric polarization.

We applied a DC electric field between two flat electrodes to attract thermally charged maghemite (γ-Fe2O3) nanocrystalline quantum dots dissolved in hexane to form smooth, robust, large area and apparently identical films of equal thickness on both electrodes. Visible microscopy, scanning electron microscopy, atomic force microscopy and profilometry showed that the electrophoretically deposited dot films were very smooth with an rms roughness of ∼10 nm for ∼0.2 µm thick films. The films were of high quality. They did not re-dissolve in hexane (as do those formed by dry casting), which is a good solvent for these dots, or in common cleaning solvents such as water, alcohols and acetone. The deposition on both electrodes implies there are both positively and negatively thermally charged dots, unlike conventional electrophoretic deposition. We used simple thermodynamics to explain the results of electrophoretic deposition macroscopically. To connect the macroscopic nature of the deposition to the microscopic nature of the dots we performed electrophoretic mobility measurements of the dots and the results seem to complement the thermodynamic treatment.

The nanocrystal quantum dot (NQD) charge states strongly influence their electrical transport properties in photovoltaic and electroluminescent devices, optical gains in NQD lasers, and the stability of the dots in thin films. We report a unique electrostatic nature of CdSe NQDs, studied by electrophoretic methods. When we submerged a pair of metal electrodes, in a parallel plate capacitor configuration, into a dilute solution of CdSe NQDs in hexane, and applied a DC voltage across the pair, thin films of CdSe NQDs were deposited on both the positive and the negative electrodes. Extensive characterizations including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared ( FTIR) and Raman studies revealed that the films on both the positive and the negative electrodes were identical in every respect, clearly indicating that: ( 1) a fraction (< 1%) of the CdSe NQDs in free form in hexane solution are charged and, more importantly, ( 2) there are equal numbers of positive and negative CdSe NQDs in the hexane solution. Experiments also show that the number of deposited dots is at least an order of magnitude higher than the number of initially charged dots, indicating regeneration. We used simple thermodynamics to explain such amphoteric nature and the charging/regeneration of the CdSe NQDs.

The response of charge to externally applied electric fields is an important basic property of any material system, as well as one critical for many applications. Here, we examine the behaviour and dynamics of charges fully confined on the nanometre length scale. This is accomplished using CdSe nanocrystals1,2,3 of controlled radius (1–2.5 nm) as prototype quantum systems. Individual electron–hole pairs are created at room temperature within these structures by photoexcitation and are probed by terahertz (THz) electromagnetic pulses4. The electronic response is found to be instantaneous even for THz frequencies, in contrast to the behaviour reported in related measurements for larger nanocrystals5 and nanocrystal assemblies6,7. The measured polarizability of an electron–hole pair (exciton) amounts to ∼104 Å3 and scales approximately as the fourth power of the nanocrystal radius. This size dependence and the instantaneous response reflect the presence of well-separated electronic energy levels induced in the system by strong quantum-confinement effects.

We describe recent results in the application of THz time-domain spectroscopy to examine photo-induced conductivity in insulators. These investigations permit us to determine the fundamental interactions governing the observed charge transport. Applications to non-contact probing of conductivity in nanostructured materials, such as semiconductor nanoparticles, will also be highlighted. Full-text article is not available.

Terahertz (THz) time-domain spectroscopy provides a powerful tool to determine the frequency-dependent conductivity of materials using propagating electromagnetic waves. The approach permits probing nanostructures and bulk materials that are difficult to contact. We describe recent measurements on photoexcited semiconductor nanoparticles and insulators.