Retraction: Colloidal Cobalt Phosphide Nanocrystals as Trifunctional Electrocatalysts for Overall Water Splitting Powered by a Zinc-Air Battery.

Adv. Mater. 2018, 30, 1705796 https://doi.org/10.1002/adma.201705796 The above article, published online on January 15, 2018, in Wiley Online Library (https://doi.org/10.1002/adma.201705796), has been retracted by agreement between the authors, the journal Editor in Chief Jos Lenders, and Wiley-VCH GmbH. The retraction has been agreed on following concerns raised by a third party and a subsequent investigation at Wake Forest University. Data integrity issues were found in Figures 1a, S2b, and S17. As a result, the authors consider the conclusions of this article invalid.

Correction: Synthesis of lead-free Cs3Sb2Br9 perovskite alternative nanocrystals with enhanced photocatalytic CO2 reduction activity.

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.

Binary and Ternary Colloidal Cu-Sn-Te Nanocrystals for Thermoelectric Thin Films.

Recent advances in copper chalcogenide-based nanocrystals (NCs), copper sulfide, and copper selenide derived nanostructures, have drawn considerable attention. However, reports of crystal phase and shape engineering of binary or ternary copper telluride NCs remain rare. Here, a colloidal hot-injection approach for producing binary copper/tin telluride, and ternary copper tin telluride NCs with controllable compositions, crystal structures, and morphologies is reported. The crystal phase and growth behavior of these tellurides are systematically studied from both experimental and theoretical perspectives. The morphology of Cu1.29 Te NCs is modified from 1D nanorods with different aspect ratios to 2D nanosheets and 3D nanocubes, by controlling the preferential growth of specific crystalline facets. A controllable phase transition from Cu1.29 Te to Cu1.43 Te NCs is also demonstrated. The latter can be further converted into Cu2 SnTe3 and SnTe through Sn incorporation. Temperature dependent thermoelectric properties of metal (Cu and Sn) telluride nanostructure thin films are also studied, including Cu1.29 Te, Cu1.43 Te, Cu2 SnTe3 , and SnTe. Cu2 SnTe3 is a low carrier density semimetal with compensating electron and hole Fermi surface pockets. The engineering of crystal phase and morphology control of colloidal copper tin telluride NCs opens a path to explore and design new classes of copper telluride-based nanomaterials for thermoelectrics and other applications.

Scalable neutral H2O2 electrosynthesis by platinum diphosphide nanocrystals by regulating oxygen reduction reaction pathways.

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).

Perovskite Quantum-Dot-in-Host for Detection of Ionizing Radiation.

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.

Synthesis of lead-free Cs3Sb2Br9 perovskite alternative nanocrystals with enhanced photocatalytic CO2 reduction activity.

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.

Wearable Thermoelectric Devices Based on Au-Decorated Two-Dimensional MoS2.

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.

Controllable Colloidal Synthesis of Tin(II) Chalcogenide Nanocrystals and Their Solution-Processed Flexible Thermoelectric Thin Films.

A systematic colloidal synthesis approach to prepare tin(II, IV) chalcogenide nanocrystals with controllable valence and morphology is reported, and the preparation of solution-processed nanostructured thermoelectric thin films from them is then demonstrated. Triangular SnS nanoplates with a recently-reported π-cubic structure, SnSe with various shapes (nanostars and both rectangular and hexagonal nanoplates), SnTe nanorods, and previously reported Sn(IV) chalcogenides, are obtained using different combinations of solvents and ligands with an Sn4+ precursor. These unique nanostructures and the lattice defects associated with their Sn-rich composition allow the production of flexible thin films with competitive thermoelectric performance, exhibiting room temperature Seebeck coefficients of 115, 81, and 153 µV K-1 for SnS, SnSe, and SnTe films, respectively. Interestingly, a p-type to n-type transition is observed in SnS and SnSe due to partial anion loss during post-synthesis annealing at 500 °C. A maximum figure of merit (ZT) value of 0.183 is achieved for an SnTe thin film at 500 K, exceeding ZT values from previous reports on SnTe at this temperature. Thus, a general strategy to prepare tin(II) chalcogenide nanocrystals is provided, and their potential for use in high-performance flexible thin film thermoelectric generators is demonstrated.

Highly robust and flexible n-type thermoelectric film based on Ag2Te nanoshuttle/polyvinylidene fluoride hybrids.

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.

Colloidal Cobalt Phosphide Nanocrystals as Trifunctional Electrocatalysts for Overall Water Splitting Powered by a Zinc-Air Battery.

Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this work, highly monodisperse CoP and Co2 P nanocrystals (NCs) are synthesized using a robust solution-phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal-rich Co2 P NCs show higher OER performance owing to easier formation of plentiful Co2 P@COOH heterojunctions. Density functional theory calculation results indicate that the desorption of OH* from cobalt sites is the rate-limiting step for both CoP and Co2 P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co2 P NC anode can achieve a current density of 10 mA cm-2 at 1.56 V, comparable even to the noble metal-based Pt/C and RuO2 /C pair. Furthermore, the CoP NCs are employed as an air cathode in a primary zinc-air battery, exhibiting a high power density of 62 mW cm-2 and good stability.

Controllable colloidal synthesis of anisotropic tin dichalcogenide nanocrystals for thin film thermoelectrics.

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.

Tailoring spin mixtures by ion-enhanced Maxwell magnetic coupling in color-tunable organic electroluminescent devices.

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.

Imbedded Nanocrystals of CsPbBr3 in Cs4 PbBr6 : Kinetics, Enhanced Oscillator Strength, and Application in Light-Emitting Diodes.

Solution-grown films of CsPbBr3 nanocrystals imbedded in Cs4 PbBr6 are incorporated as the recombination layer in light-emitting diode (LED) structures. The kinetics at high carrier density of pure (extended) CsPbBr3 and the nanoinclusion composite are measured and analyzed, indicating second-order kinetics in extended and mainly first-order kinetics in the confined CsPbBr3 , respectively. Analysis of absorption strength of this all-perovskite, all-inorganic imbedded nanocrystal composite relative to pure CsPbBr3 indicates enhanced oscillator strength consistent with earlier published attribution of the sub-nanosecond exciton radiative lifetime in nanoprecipitates of CsPbBr3 in melt-grown CsBr host crystals and CsPbBr3 evaporated films.

Ultrathin, Washable, and Large-Area Graphene Papers for Personal Thermal Management.

Freestanding, flexible/foldable, and wearable bifuctional ultrathin graphene paper for heating and cooling is fabricated as an active material in personal thermal management (PTM). The promising electrical conductivity grants the superior Joule heating for extra warmth of 42 °C using a low supply voltage around 3.2 V. Besides, based on its high out-of-plane thermal conductivity, the graphene paper provides passive cooling via thermal transmission from the human body to the environment within 7 s. The cooling effect of graphene paper is superior compared with that of the normal cotton fiber, and this advantage will become more prominent with the increased thickness difference. The present bifunctional graphene paper possesses high durability against bending cycles over 500 times and wash time over 1500 min, suggesting its great potential in wearable PTM.

Self-Assembled Heterostructures: Selective Growth of Metallic Nanoparticles on V2 -VI3 Nanoplates.

Precise control of the selective growth of heterostructures with specific composition and functionalities is an emerging and extremely challenging topic. Here, the first investigation of the difference in binding energy between a series of metal-semiconductor heterostructures based on layered V2 -VI3 nanostructures is investigated by means of density functional theory. All lateral configurations show lower formation energy compared with that of the vertical ones, implying the selective growth of metal nanoparticles. The simulation results are supported by the successful fabrication of self-assembled Ag/Cu-nanoparticle-decorated p-type Sb2 Te3 and n-type Bi2 Te3 nanoplates at their lateral sites through a solution reaction. The detailed nucleation-growth kinetics are well studied with controllable reaction times and precursor concentrations. Accompanied by the preserved topological structure integrity and electron transfer on the semiconductor host, exceptional properties such as dramatically increased electrical conductivity are observed thanks to the pre-energy-filtering effect before carrier injection. A zigzag thermoelectric generator is built using Cu/Ag-decorated Sb2 Te3 and Bi2 Te3 as p-n legs to utilize the temperature gradient in the vertical direction. Synthetic approaches using similar chalcogenide nanoplates as building blocks, as well as careful control of the dopant metallic nanoparticles or semiconductors, are believed to be broadly applicable to other heterostructures with novel applications.

2D Chalcogenide Nanoplate Assemblies for Thermoelectric Applications.

Engineered atomic dislocations have been used to create a novel, Sb2 Te3 nanoplate-like architecture that exhibits a unique antisymmetric chirality. High-resolution transmission electron microscopy (HRTEM) coupled with atomic force microscopy and X-ray photoelectron spectroscopy reveals the architectures to be extremely well ordered with little residual strain. Surface modification of these topologically complex macrostructures (≈3 µm) has been achieved by direct growth of metallic Ag nanoparticles onto the edge sites of the Sb2 Te3 . Again, HRTEM shows this nanoparticle decoration to be atomically sharp at the boundaries and regularly spaced along the selvedge of the nanostructure. Transport experiments of densified films of these assemblies exhibit marked increases in carrier density after nanoengineering, yielding 3.5 × 104 S m-1 in electrical conductivity. An increased Seebeck coefficient by 20% in parallel with electrical conductivity is also observed. This gives a thermoelectric power factor of 371 µW m-1 K-2 , which is the highest value for a flexible, freestanding film to date. These results suggest an entirely new direction in the search for wearable power harvesters based on topologically complex, low-dimensional nanoassemblies.

Achieving High Performance in AC-Field Driven Organic Light Sources.

Charge balance in organic light emitting structures is essential to simultaneously achieving high brightness and high efficiency. In DC-driven organic light emitting devices (OLEDs), this is relatively straight forward. However, in the newly emerging, capacitive, field-activated AC-driven organic devices, charge balance can be a challenge. In this work we introduce the concept of gating the compensation charge in AC-driven organic devices and demonstrate that this can result in exceptional increases in device performance. To do this we replace the insulator layer in a typical field-activated organic light emitting device with a nanostructured, wide band gap semiconductor layer. This layer acts as a gate between the emitter layer and the voltage contact. Time resolved device characterization shows that, at high-frequencies (over 40 kHz), the semiconductor layer allows for charge accumulation in the forward bias, light generating part of the AC cycle and charge compensation in the negative, quiescent part of the AC cycle. Such gated AC organic devices can achieve a non-output coupled luminance of 25,900 cd/m(2) with power efficiencies that exceed both the insulator-based AC devices and OLEDs using the same emitters. This work clearly demonstrates that by realizing balanced management of charge, AC-driven organic light emitting devices may well be able to rival today's OLEDs in performance.

Nanowires as Building Blocks to Fabricate Flexible Thermoelectric Fabric: The Case of Copper Telluride Nanowires.

A general approach to fabricate nanowires based inorganic/organic composite flexible thermoelectric fabric using a simple and efficacious five-step vacuum filtration process is proposed. As an excellent example, the performance of freestanding flexible thermoelectric thin film using copper telluride nanowires/polyvinylidene fluoride (Cu1.75Te NWs/PVDF = 2:1) as building block is demonstrated. By burying the Cu1.75Te NWs into the PVDF polymer agent, the flexible fabric exhibits room-temperature Seebeck coefficient and electric conductivity of 9.6 µV/K and 2490 S/cm, respectively, resulting in a power factor of 23 µW/(mK(2)) that is comparable to the bulk counterpart. Furthermore, this NW-based flexible fabric can endure hundreds of cycles of bending tests without significant performance degradation.

Differential cytotoxic and radiosensitizing effects of silver nanoparticles on triple-negative breast cancer and non-triple-negative breast cells.

Identification of differential sensitivity of cancer cells as compared to normal cells has the potential to reveal a therapeutic window for the use of silver nanoparticles (AgNPs) as a therapeutic agent for cancer therapy. Exposure to AgNPs is known to cause dose-dependent toxicities, including induction of oxidative stress and DNA damage, which can lead to cell death. Triple-negative breast cancer (TNBC) subtypes are more vulnerable to agents that cause oxidative stress and DNA damage than are other breast cancer subtypes. We hypothesized that TNBC may be susceptible to AgNP cytotoxicity, a potential vulnerability that could be exploited for the development of new therapeutic agents. We show that AgNPs are highly cytotoxic toward TNBC cells at doses that have little effect on nontumorigenic breast cells or cells derived from liver, kidney, and monocyte lineages. AgNPs induced more DNA and oxidative damage in TNBC cells than in other breast cells. In vitro and in vivo studies showed that AgNPs reduce TNBC growth and improve radiation therapy. These studies show that unmodified AgNPs act as a self-therapeutic agent with a combination of selective cytotoxicity and radiation dose-enhancement effects in TNBC at doses that are nontoxic to noncancerous breast and other cells.

Cellular responses of eastern oysters, Crassostrea virginica, to titanium dioxide nanoparticles.

Because of the continued development and production of a variety of nanomaterials and nanoparticles, their uptake and effects on the biota of marine ecosystems must be investigated. Filter feeding bivalve molluscs are highly adapted for capturing particles from the external environment and readily internalize nano- and micro-sized particles through endocytosis, so they are commonly used as valuable indicator species for nanoparticle studies. In these studies, adult eastern oysters, Crassostrea virginica, were exposed to a range of titanium dioxide nanoparticle (TiO2-NP) concentrations (5, 50, 500, and 5000 µg/L) in conjunction with natural sunlight. Isolated hepatopancreas tissues were also exposed to the same TiO2-NP concentrations using particles exposed to similar light and dark conditions. Dose-dependent decreases in lysosomal stability were observed in the adult oyster studies as well as in the isolated tissues, at exposures as low as 50 µg/L. Titanium accumulation in isolated hepatopancreas tissue studies was directly correlated to lysosomal destabilization. Based on measurements of lipid peroxidation as an indicator of oxidative stress, TiO2-NPs toxicity was not related to increased ROS production over the short-term course of these exposures. Analysis of particle size using dynamic light scattering (DLS) indicated that concentration had a significant impact on agglomeration rates, and the small agglomerates as well as individual particles are readily processed by oysters. Overall, this study illustrates that low concentrations of TiO2-NPs may cause sublethal toxicity on oysters, which might be enhanced under natural sunlight conditions. In estuarine environments, where these nanomaterials are likely to accumulate, agglomeration rates, interaction with organics, and responses to sunlight are critical in determining the extent of their bioreactivity and biological impacts.