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A simplified plasmadynamics model is presented that examines radial and axial dependence of the current sheet structure of a coaxial quasi-steady self-field plasma accelerator, dominated by electromagnetic forces. Two radial electric field distributions are considered as limiting cases. In the first case, constant current flows between constant-radius electrodes; in the second case, constant current flows between electrodes and also extends downstream of the electrodes. Calculations for Teflon ([Formula: see text]) plasma show the distribution of plasma parameters inside the current sheet, as well as terminal values for kinetic efficiency, voltage, and impedance for both [Formula: see text] distributions. Evaluation of the validity of simplifying assumptions is presented, as is the behavior of previously developed accelerators as interpreted by the model.

The concept of quantum-dot-in-perovskite solids pioneered by Ning and co-workers introduces a useful class of solution-processed type I heterostructures for optoelectronics applications. Concurrent searches for solution-processable detectors of ionizing radiation have focused on lead-halide perovskites. As described in this issue of ACS Nano, Cao et al. examined CsPbBr3 nanocrystals imbedded in Cs4PbBr6 as a wider gap host and determined its performance and possibilities as a scintillator for X-ray imaging. In this Perspective, we describe issues and research opportunities on ionizing radiation imaging and spectroscopy based on the CsPbBr3@Cs4PbBr6 composite and other perovskite-dot-in-host combinations in which the dot may be of lower dimensionality than 3, and we explore ionizing radiation detectors using halide perovskites.

A synthetic method for uniform and pure Cs3Sb2Br9 NCs has been developed. Cs3Sb2Br9 NCs exhibit a 10-fold increase in activity for the photocatalytic CO2 reduction reaction compared to CsPbBr3 NCs, achieving 510 μmol CO g-1 cat. after 4 h. Density functional theory shows that Cs3Sb2Br9 surfaces sufficiently expose Sb to allow reactivity, as opposed to the unreactive CsPbBr3 surface.

Solution processing of organic semiconductors offers key advantages, including low-cost and compatibility with large-area flexible substrates. Controlling film crystallization from solution, however, is not trivial. This is particularly important since the device properties are highly dependent on the film microstructure, which, in turn, can vary significantly with processing. In this work, we tuned the small molecule organic semiconductor film microstructure by using a binary solvent consisting of a host solvent and a high-boiling point solvent additive and studied the effect of additive content on charge transport. Spin coated 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene films processed from a mixture of chlorobenzene and dichlorobenzene, in various ratios, were investigated by using Polarized Optical Microscopy, Scanning Electron Microscopy and Atomic Force Microscopy analysis and their electrical properties were evaluated from bottom-contact bottom-gate organic field-effect transistors. We found that the mobility increased by three times for a 8% dichlorobenzene content as a result of reducing the density of the grain boundaries within the device channel.

Correction for ‘Synthesis of lead-free Cs3Sb2Br9 perovskite alternative nanocrystals with enhanced photocatalytic CO2 reduction activity’ by Chang Lu et al., Nanoscale, 2020, 12, 2987–2991, https://doi.org/10.1039/C9NR07722G.

The many allotropes of carbon are of fundamental interest as thermoelectrics. Some can have very large Seebeck coefficients α (sometimes, the symbol S is used for thermoelectric power; it is the thermoelectric voltage, Vth, generated per K). The Seebeck coefficient tells us how large a voltage is generated, if one side of the sample is heated and the other side is cooled (“thermoelectric generator”). For example, single-walled carbon nanotubes (SWNTs) can have Seebeck coefficients as high as 60 μV/K and graphene up to 100 μV/K when subject to a gate voltage. Sometimes, large electrical conductivities σ can also be obtained with these two carbon materials (in aggregate mats) of the order: σ ~ 105 S/m depending on the morphology and doping.

When we say “nanocomposite” or “matrix composite,” most of us think of a blend of nano/micro-scale filler materials and a host polymer to which we want to add some new properties. Usually, the properties that you get in such a matrix [nano]composite are determined by the rule of mixtures plus the architecture of the filler within the volume of the host. For instance, consider the example of trying to make poly methyl methacrylate (PMMA) electrically conductive by adding carbon nanotubes (CNTs). Start blending very few nanotubes into a volume of PMMA. Allow it to set and measure the conductivity. At very low loadings of carbon nanotubes in the PMMA (often measured in % by weight of added mass), the conductivity is zero. The CNTs are far apart and scattered throughout the volume, so they do not help to carry current. As more CNTs are added, the nanotubes begin to touch each other, known as the percolation threshold, and the materials become conductive, passing current through the volume by carrier hopping from CNT to CNT. But surely, the level of CNT loading at which this happens (~ 1% wt.) depends on whether or not the nanotubes spread out evenly within the polymer or if they all bunch together in small clusters.

It seems quite trivial that we live in a three-dimensional world: there is left and right, forward and backward, up and down. Leibnitz (1646–1716) says, we have the concept of space because of “preestablished harmony”: God has created nature and he has created our mind, so they must fit together. Darwin (1809–1882) would say, our mind has developed in response to our environment, again they must fit together. According to Kant (1724–1804), space is a form of sensibility, which exists prior to any perception. Philosophers can fill many volumes with discussions on what space is and what dimension means.

Despite progress in small scale electrocatalytic production of hydrogen peroxide (H2O2) using a rotating ring-disk electrode, further work is needed to develop a non-toxic, selective, and stable O2-to-H2O2 electrocatalyst for realizing continuous on-site production of neutral hydrogen peroxide. We report ultrasmall and monodisperse colloidal PtP2 nanocrystals that achieve H2O2 production at near zero-overpotential with near unity H2O2 selectivity at 0.27 V vs. RHE. Density functional theory calculations indicate that P promotes hydrogenation of OOH* to H2O2 by weakening the Pt-OOH* bond and suppressing the dissociative OOH* to O* pathway. Atomic layer deposition of Al2O3 prevents NC aggregation and enables application in a polymer electrolyte membrane fuel cell (PEMFC) with a maximum r(H2O2) of 2.26 mmol h−1 cm−2 and a current efficiency of 78.8% even at a high current density of 150 mA cm−2. Catalyst stability enables an accumulated neutral H2O2 concentration in 600 mL of 3.0 wt% (pH = 6.6)., The synthesis of high concentration H2O2 from water and oxygen at moderate conditions could provide an on-site H2O2 source for medical and water purification applications. Here, authors show Al2O3-stabilized PtP2 nanocrystals to enable selective, stable and efficient neutral pH H2O2 production.

In the colloidal synthesis of inorganic perovskite materials, cesium oleate (CsOL) is the most commonly used Cs precursor. Yet, despite its ubiquitous use in literature, CsOL has been observed to be insoluble at room temperature and leads to surprisingly inconsistent results in CsPbX3 nanocrystal synthesis, depending on the Cs salt from which the precursor is derived. We show that under the conditions used in most reports, the amount of oleic acid (OA) added, while stoichiometrically sufficient, still leads to incomplete conversion of the Cs salts to CsOL. This results in a mixture of Cs sources being present during the reaction, causing decreased homogeneity and reproducibility. When a 1:5 Cs:OA ratio is used, complete conversion is readily obtained, even under mild conditions, resulting in a precursor solution that is soluble at room temperature and yields identical synthetic results, regardless of the initial Cs source. Furthermore, 1H nuclear magnetic resonance (NMR) of solutions prepared using varyin...

Two-dimensional (2D) materials have recently opened a new avenue to flexible thermoelectric materials with enhanced performance because of their unique electronic transport properties. Here, we report a feasible approach to improve the thermoelectric performance of transition-metal dichalcogenides by effectively decorating 2D MoS2 with Au nanoparticles using in situ growth. The present Au-decorated MoS2-assembled heterojunction system shows a certain decoupled phenomenon, that is, the Seebeck coefficient and conductivity increased simultaneously. This is due to the occurrence of p-type doping of the MoS2 2H phase and injection energy filtering of dopant-originated carriers around the local band bending at the interface. The composite flexible films can achieve a power factor value of 166.3 μW m–1 K–2 at room temperature, which have great potential for harvesting human body heat.

In this work, we show that the spin dynamics of excitons can be dramatically altered by Maxwell magnetic field coupling, together with an ion-enhanced, low-internal-splitting-energy organic semiconducting emitter. By employing a unique, alternating current (AC)-driven organic electroluminescent (OEL) device architecture that optimizes this magnetic field coupling, almost complete control over the singlet-to-triplet ratio (from fluorescent to phosphorescent emission in a single device) is realized. We attribute this spin population control to magnetically sensitive polaron–spin pair intersystem crossings (ISCs) that can be directly manipulated through external driving conditions. As an illustration of the utility of this approach to spin-tailoring, we demonstrate a simple hybrid (double-layer) fluorescence–phosphorescence (F–P) device using a polyfluorene-based emitter with a strong external Zeeman effect and ion-induced long carrier diffusion. Remarkable control over de-excitation pathways is achieved by controlling the device-driving frequency, resulting in complete emission blue–red color tunability. Picosecond photoluminescence (PL) spectroscopy directly confirms that this color control derives from the magnetic manipulation of the singlet-to-triplet ratios. These results may pave the way to far more exotic organic devices with magnetic-field-coupled organic systems that are poised to usher in an era of dynamic spintronics at room temperature., Organic optoelectronics: spin-state control The light emission of an organic electroluminescent device can be tuned between blue fluorescence and red phosphorescence by using magnetic field effects to control the exciton population of singlet and triplet spins within the device. That’s the finding of a Chinese-US collaboration that use an alternating current (AC) power source to generate the required magnetic fields for the spin-state control inside a hybrid device featuring the blue fluorescent emitter polyfluorene (PFN-Br) and the red phosphorescent emitter PVK:Ir(MDQ)2(acac). By sweeping the frequency of the drive voltage from 50 to 70,000 Hz the color of the emission was seen to shift from blue to cold-white to warm-white to red. In addition to applications as a tunable light source, the approach could also be useful for performing experiments in dynamic spintronics at room temperature.

Colloidal semiconductor quantum dot (CQD)-based photocathodes for solar-driven hydrogen evolution have attracted significant attention because of their tunable size, nanostructured morphology, crystalline orientation, and band gap. Here, we report a thin film heterojunction photocathode composed of organic PEDOT:PSS as a hole transport layer, CdSe CQDs as a semiconductor light absorber, and conformal Pt layer deposited by atomic layer deposition (ALD) serving as both a passivation layer and cocatalyst for hydrogen evolution. In neutral aqueous solution, a PEDOT:PSS/CdSe/Pt heterogeneous photocathode with 200 cycles of ALD Pt produces a photocurrent density of −1.08 mA/cm2 (AM-1.5G, 100 mW/cm2) at a potential of 0 V versus reversible hydrogen electrode (RHE) (j0) in neutral aqueous solution, which is nearly 12 times that of the pristine CdSe photocathode. This composite photocathode shows an onset potential for water reduction at +0.46 V versus RHE and long-term stability with negligible degradation. In th...

Metal halide perovskites present specific challenges as emitters in large area, surface emission lighting devices. Among these challenges is the vast difference in carrier mobilities between the perovskite and many organic buffer layers typically used in such device fabrication as transport and blocking layers. This can make it difficult to engineer recombination to achieve white emitting devices generally. However, in this work, we introduce unique modulation of excitonic confinement within the perovskite layer of the device stack to control overall placement of the recombination zone. This results in a white light emitter that is bright and highly tunable, providing a path to realize white perovskite related light-emitting devices.

Self-assembly has proven to be a powerful method of preparing structurally intricate nanostructures. In this work, we design a nanoscale “Chinese Coin” based on Bi2Te3 nanoplates (NPs) by using a simple and scalable solution process; i.e., a single pore is introduced on a hexagonal/round plate similar to a fender washer. The diameter of the nanopores is well controlled within the range of 5–100 nm and depends strongly on the reaction time and heating temperatures, suggesting a kinetics related mechanism. Moreover, the thermal evolution of stable Bi2Te3 plate-pore structures was systematically explored to elucidate the underlying energetics of the V2-VI3 chalcogenides. We found that the nanopore is initiated near the middle of the plate, followed by the successive removal of Bi2Te3 slices from the high edge-energy pore with increased temperatures (70–150 °C), leading finally to the formation of a stable nanopore. The morphology of the pore as well as the local lattice crystallinity was studied using high-r...

Highly robust and flexible n-type thermoelectric (TE) films based on Ag2Te nanoshuttle/polyvinylidene fluoride were prepared by a solution-processable method without a surfactant. A good power performance of over 30 μW (m K2)-1 at room temperature was achieved. Moreover, the synthesized fabrics also exhibited potential for application in flexible electronic devices with negligible performance change after 1000 bending cycles.

Tin chalcogenides have shown promise in applications including energy storage, optoelectronics, photovoltaics, and thermoelectrics. Here, we present a colloidal synthesis strategy to produce tin dichalcogenide nanocrystals (NCs) with controllable stoichiometry, vacancies, shape, and crystal structure. Compared with previously reported methods, we use less expensive precursors, such as tin(iv) chloride and sulfur or selenium powder, to produce tin(iv) chalcogenide NCs. SnS2 and SnSe2 NCs with novel NC morphologies including SnS2 nanoflowers/nanoflakes, SnSe2 nanosheets with circular and hexagonal shapes, as well as mixtures of nanospheres and nanoflakes were prepared by varying the solvents and anion precursors. We were also able to reduce tin(iv) to tin(ii) to produce tin(ii) chalcogenide NCs. The corresponding thin films were prepared by spin-coating, followed by post-treatment to study their thermoelectric properties. Room temperature Seebeck coefficients of -150 μV K-1 and -126 μV K-1 were measured for SnS2 and SnSe2 films, demonstrating their promise as thin film thermoelectric materials.

The environmental impacts of nanoparticles are explored, particularly exo-polysaccharides, organic molecules, and bio-minerals, which comprise nanocrystals and mesocrystals composed of nanoparticle aggregates. An increasing number of recent studies on Engineered NPs have shown the detrimental effect on the various environmental compartments. As a result, a more comprehensive understanding of nanoparticles’ elemental speciations, distributions, transport mechanisms, and phyto-toxic impacts is crucial. Because of their possible health risks, and their impact on biologically active elements in specific environmental matrices, qualitative and quantitative in-situ measurements of nanoparticle distributions and interactions are necessary. Specifically, nanoparticle applications displaying heterogeneous distribution patterns of metals in different environmental matrices are discussed along with analysis of changes in chemical speciation via synchrotron radiation systems.

We present a hybrid photovoltaic/thermal (PV/T) system. This system utilizes a thermal fluid in a tubular geometry to act both as an infrared absorber and an optical lens. The optical lens then focuses light onto a PV fixed to the back of the glass tubing. The result is a capture of both PV and thermal energy for the system. In this work, multiple thermal fluids are tested to compare PV efficiency as a function of angle as well as thermal capture. We show that using higher index thermal fluids in our system has the ability to enhance PV energy production when compared to traditionally flat panels. Increases of approximately 98.1% in electrical energy generated over the span of 12 h for the tubular structure, compared with that of the planar, can be added to the heat captured by the thermal fluid. This provides an inexpensive approach to high density solar power generation.

In recent years, significant attention has been paid to perovskite materials. In particular, lead triiodide-based perovskites have exhibited superb optoelectronic properties. Enhancing the stability of these materials is an essential step towards large-scale applications. In this study, by simply adding trioctylphosphine (TOP) as part of the post-synthesis treatment, we significantly enhance the stability of CsPbI3 quantum dots (QDs) in the solution phase, which otherwise decay rapidly in hours. For CsPbI3 QDs treated with TOP, the absorption and photoluminescence emission properties are unchanged over the course of weeks, and the quantum yield remains almost constant at 30% even after 1 month. The morphologies of both treated and untreated QDs are initially cubic; however, the treated QDs largely maintain their initial size and shape, while the untreated ones lose size uniformity, which is a sign of degradation. Infrared spectroscopy and X-ray photoelectron spectroscopy confirm the presence of P in the TOP-treated QDs. We insights that help to resolve the intrinsic instability issue of triiodide perovskite materials and devices.

A synthetic method for uniform and pure Cs3Sb2Br9 NCs has been developed. Cs3Sb2Br9 NCs exhibit a 10-fold increase in activity for the photocatalytic CO2 reduction reaction compared to CsPbBr3 NCs, achieving 510 μmol CO g-1 cat. after 4 h. Density functional theory shows that Cs3Sb2Br9 surfaces sufficiently expose Sb to allow reactivity, as opposed to the unreactive CsPbBr3 surface.

A novel axisymmetric device with pulsed spark emission was developed as an active flow control alternative to passive vortex generators. The flowfield induced by the actuator was studied in quiesce...