Showing papers by "Peidong Yang published in 2019"

Designing materials for electrochemical carbon dioxide recycling

Abstract: Electrochemical carbon dioxide recycling provides an attractive approach to synthesizing fuels and chemical feedstocks using renewable energy. On the path to deploying this technology, basic and applied scientific hurdles remain. Integrating catalytic design with mechanistic understanding yields scientific insights and progresses the technology towards industrial relevance. Catalysts must be able to generate valuable carbon-based products with better selectivity, lower overpotentials and improved current densities with extended operation. Here, we describe progress and identify mechanistic questions and performance metrics for catalysts that can enable carbon-neutral renewable energy storage and utilization. Electrochemical carbon dioxide reduction is an attractive approach for obtaining fuels and chemical feedstocks using renewable energy. In this Review, the authors describe progress so far, identify mechanistic questions and performance metrics, and discuss design principles for improved activity and selectivity.

Nanowires for Photonics.

Abstract: All-photonic integrated circuits are promising platforms for future systems beyond the limitation of Moore's law. Over the last several decades, one-dimensional (1D) nanowires have demonstrated great potential in photonic circuitry because of their unique 1D structure to effectively generate and tightly confine optical signals as well as easily tunable optical properties. In this Review, we categorize nanowires based on the optical properties (i.e., semiconducting, metallic, and dielectric nanowires) for their potential photonic applications (as light emitters or plasmonic and photonic waveguides). We further discuss the recent efforts in integration of nanowire-based photonic elements toward next-generation optical information processors. However, there are still several challenges remaining before the nanowires are fully utilized as photonic building blocks. The scientific and technical challenges and outlooks are provided to indicate the future directions.

Measurement of the cosmic-ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite

Abstract: The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2 1/2 years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.

Three-Dimensional Phthalocyanine Metal-Catecholates for High Electrochemical Carbon Dioxide Reduction.

Abstract: The synthesis of a new anionic 3D metal-catecholate framework, termed MOF-1992, is achieved by linking tetratopic cobalt phthalocyanin-2,3,9,10,16,17,23,24-octaol linkers with Fe3(-C2O2-)6(OH2)2 trimers into an extended framework of roc topology. MOF-1992 exhibits sterically accessible Co active sites together with charge transfer properties. Cathodes based on MOF-1992 and carbon black (CB) display a high coverage of electroactive sites (270 nmol cm-2) and a high current density (-16.5 mA cm-2; overpotential, -0.52 V) for the CO2 to CO reduction reaction in water (faradaic efficiency, 80%). Over the 6 h experiment, MOF-1992/CB cathodes reach turnover numbers of 5800 with turnover frequencies of 0.20 s-1 per active site.

Nontoxic nanopore electroporation for effective intracellular delivery of biological macromolecules.

Abstract: We present a simple nanopore-electroporation (NanoEP) platform for delivery of nucleic acids, functional protein, and Cas9 single-guide RNA ribonucleoproteins into both adherent and suspension cells with up to 80% delivery efficiency and >95% cell viability. Low-voltage electric pulses permeabilize a small area of cell membrane as a cell comes into close contact with the nanopores. The biomolecule cargo is then electrophoretically drawn into the cells through the nanopores. In addition to high-performance delivery with low cell toxicity, the NanoEP system does not require specialized buffers, expensive materials, complicated fabrication processes, or cell manipulation; it simply consists of a generic nanopore-embedded water-filter membrane and a low-voltage square-wave generator. Ultimately, the NanoEP platform offers an effective and flexible method for universal intracellular delivery.

Introduction: 1D Nanomaterials/Nanowires.

Abstract: Wires of different forms have been an integral part of human society for centuries. Electricity is being delivered through powerlines to every household; information is routinely transmitted through optical fibers, and bridge-building requires the use of mechanically robust cables. In the past 25 years, scientists have discovered a fundamentally new process for making nanoscopic wires, 1000 times thinner than human hairs, enabling a new generation of computing, integrated photonics, energy and biomedical technologies.

Perovskite nanowire-block copolymer composites with digitally programmable polarization anisotropy.

Abstract: One-dimensional (1D) nanomaterials with highly anisotropic optoelectronic properties are key components in energy harvesting, flexible electronics, and biomedical imaging devices. 3D patterning methods that precisely assemble nanowires with locally controlled composition and orientation would enable new optoelectronic device designs. As an exemplar, we have created and 3D-printed nanocomposite inks composed of brightly emitting colloidal cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) nanowires suspended in a polystyrene-polyisoprene-polystyrene block copolymer matrix. The nanowire alignment is defined by the programmed print path, resulting in optical nanocomposites that exhibit highly polarized absorption and emission properties. Several devices have been produced to highlight the versatility of this method, including optical storage, encryption, sensing, and full-color displays.

Quantitative imaging of anion exchange kinetics in halide perovskites.

Abstract: Ion exchange, as a postsynthetic transformation strategy, offers more flexibilities in controlling material compositions and structures beyond direct synthetic methodology. Observation of such transformation kinetics on the single-particle level with rich spatial and spectroscopic information has never been achieved. We report the quantitative imaging of anion exchange kinetics in individual single-crystalline halide perovskite nanoplates using confocal photoluminescence microscopy. We have systematically observed a symmetrical anion exchange pathway on the nanoplates with dependence on reaction time and plate thickness, which is governed by the crystal structure and the diffusion-limited transformation mechanism. Based on a reaction–diffusion model, the halide diffusion coefficient was estimated to be on the order of 10 − 14 cm 2 ⋅ s − 1 . This diffusion-controlled mechanism leads to the formation of 2D perovskite heterostructures with spatially resolved coherent interface through the precisely controlled anion exchange reaction, offering a design protocol for tailoring functionalities of semiconductors at the nano-/microscale.

Measurement of the cosmic-ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite.

Abstract: The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with two and a half years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time an experiment directly measures the cosmic ray protons up to ~100 TeV with a high statistics. The measured spectrum confirms the spectral hardening found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee, and sheds new light on the origin of Galactic cosmic rays.

Self-Assembly of Two-Dimensional Perovskite Nanosheet Building Blocks into Ordered Ruddlesden-Popper Perovskite Phase.

Abstract: The self-assembly of nanoparticles, a process whereby nanocrystal building blocks organize into even more ordered superstructures, is of great interest to nanoscience. Here we report the layer-by-layer assembly of 2D perovskite nanosheet building blocks. Structural analysis reveals that the assembled superlattice nanocrystals match with the layered Ruddlesden-Popper perovskite phase. This assembly proves reversible, as these superlattice nanocrystals can be reversibly exfoliated back into their building blocks via sonication. This study demonstrates the opportunity to further understand and exploit thermodynamics to increase order in a system of nanoparticles and to study emergent optical properties of a superlattice from 2D, weakly attracted, perovskite building blocks.

Pressure-induced semiconductor-to-metal phase transition of a charge-ordered indium halide perovskite

Abstract: Phase transitions in halide perovskites triggered by external stimuli generate significantly different material properties, providing a great opportunity for broad applications. Here, we demonstrate an In-based, charge-ordered (In+/In3+) inorganic halide perovskite with the composition of Cs2In(I)In(III)Cl6 in which a pressure-driven semiconductor-to-metal phase transition exists. The single crystals, synthesized via a solid-state reaction method, crystallize in a distorted perovskite structure with space group I4/m with a = 17.2604(12) A, c = 11.0113(16) A if both the strong reflections and superstructures are considered. The supercell was further confirmed by rotation electron diffraction measurement. The pressure-induced semiconductor-to-metal phase transition was demonstrated by high-pressure Raman and absorbance spectroscopies and was consistent with theoretical modeling. This type of charge-ordered inorganic halide perovskite with a pressure-induced semiconductor-to-metal phase transition may inspire a range of potential applications.

Ion Write Microthermotics: Programing Thermal Metamaterials at the Microscale.

Abstract: Considerable advances in manipulating heat flow in solids have been made through the innovation of artificial thermal structures such as thermal diodes, camouflages, and cloaks. Such thermal devices can be readily constructed only at the macroscale by mechanically assembling different materials with distinct values of thermal conductivity. Here, we extend these concepts to the microscale by demonstrating a monolithic material structure on which nearly arbitrary microscale thermal metamaterial patterns can be written and programmed. It is based on a single, suspended silicon membrane whose thermal conductivity is locally, continuously, and reversibly engineered over a wide range (between 2 and 65 W/m·K) and with fine spatial resolution (10-100 nm) by focused ion irradiation. Our thermal cloak demonstration shows how ion-write microthermotics can be used as a lithography-free platform to create thermal metamaterials that control heat flow at the microscale.

Copper(I)-Based Highly Emissive All-Inorganic Rare-Earth Halide Clusters

Abstract: Summary The development of new environmentally friendly luminescent materials is crucial for future solid-state lighting, sensor, and display applications. Here, a Cu(I)-based all-inorganic rare-earth halide material, Rb 8 CuSc 3 Cl 18 , has been synthesized by a solid-state reaction method. In this compound, two Cu(I) ions are connected to three rare-earth halide octahedra to form a paddle-wheel-like cluster. The Cu(I) coordinated rare-earth halide clusters contribute to a strong blue photoluminescence emission. This Cu(I)-regulated emission can be extended to other isostructural compounds, such as Rb 8 CuY 3 Cl 18 . Moreover, the crucial role of Cu(I) has been illustrated by the isostructural non-emissive Rb 8 AgSc 3 Cl 18 . On the basis of comprehensive spectroscopy studies and density functional theory calculations, we found that Cu(I) photo-oxidation and correct orbital-energy-level alignment are crucial for the observed bright-blue emission through a proposed metal (Cu)-to-octahedra ([ScCl 6 ] 3− ) charge-transfer mechanism. The discovery of Cu(I)-based all-inorganic rare-earth halide clusters establishes a new strategy for constructing promising emissive halide materials.

Liquid-Like Interfaces Mediate Structural Phase Transitions in Lead Halide Perovskites

Abstract: Microscopic pathways of structural phase transitions are difficult to probe because they occur over multiple, disparate time and length scales. Using $in$ $situ$ nanoscale cathodoluminescence microscopy, we visualize the thermally-driven transition to the perovskite phase in hundreds of non-perovskite phase nanowires, resolving the initial nanoscale nucleation and subsequent mesoscale growth and quantifying the activation energy for phase propagation. In combination with molecular dynamics computer simulations, we reveal that the transformation does not follow a simple martensitic mechanism, and proceeds via ion diffusion through a liquid-like interface between the two structures. While cations are disordered in this liquid-like region, the halide ions retain substantial spatial correlations. We find that the anisotropic crystal structure translates to faster nucleation of the perovskite phase at nanowire ends and faster growth along the long nanowire axis. These results represent a significant step towards manipulating structural phases at the nanoscale for designer materials properties.

Solar-driven carbon dioxide fixation using photosynthetic semiconductor bio-hybrids.

Abstract: Solar-driven conversion of carbon dioxide to value-added carbon products is an ambitious objective of ongoing research efforts. However, high overpotential, low selectivity and poor CO2 mass transfer plague purely inorganic electrocatalysts. In this instance, we can consider a class of biological organisms that have evolved to achieve CO2 fixation. We can harness and combine the streamlined CO2 fixation pathways of these whole organisms with the exceptional ability of semiconducting nanomaterials to harvest solar energy. A novel nanomaterial-biological interface has been pioneered in which light-capturing cadmium sulfide nanoparticles reside within individual organisms essentially powering biological CO2 fixation by solar energy. In order to further develop the photosensitized organism platform, more biocompatible photosensitizers and cytoprotective strategies are required as well as elucidation of charge transfer mechanisms. Here, we discuss the ability of gold nanoclusters to photosensitize a model acetogen effectively and biocompatibly. Additionally, we present innovative materials including two-dimensional metal organic framework sheets and alginate hydrogels to shield photosensitized cells. Finally, we delve into original work using transient absorption spectroscopy to inform on charge transfer mechanisms.

Reply to Nathamgari et al.: Nanopore electroporation for intracellular delivery of biological macromolecules.

Abstract: We are pleased to see that simulation results by Mukherjee et al. (1) and Nathamgari et al. (2) are accordant with our experimental results (3). We also very much appreciate the detailed simulation study by Mukherjee et al. (1), specifically, on the prediction of the existence of an intermediate optimum voltage for transporting macromolecules. Although we agree with Nathamgari et al. (2) on the simplicity of the nanopore-electroporation system in allowing for an easy … [↵][1]1To whom correspondence may be addressed. Email: p_yang{at}berkeley.edu. [1]: #xref-corresp-1-1

Co-feeding copper catalysts couple carbon.

Abstract: The mechanistic electrochemical mass spectrometry study of ethylene production on Cu-based nanocatalysts under CO2/CO co-feeds indicates the existence of separate, reactant-specific surface adsorption sites for CO2 and CO, which guided the design of a multi-component CO2RR electrocatalyst.

Method of depositing nanoparticles on an array of nanowires

Abstract: This disclosure provides systems, methods, and apparatus related to nanostructures. In one aspect, an array of nanowires is provided. The array of nanowires comprises a plurality of nanowires. End of nanowires of the plurality of nanowires are attached to a substrate. A liquid including a plurality of nanoparticles is deposited on the array of nanowires. The liquid is evaporated from the array of nanowires. Nanoparticles of the plurality of nanoparticles are deposited on the nanowires as a meniscus of the liquid recedes along lengths of the plurality of nanowires.

유기 프리 라디컬들을 사용한 초박형 금속 나노와이어들의 합성

Abstract: 유기 환원제를 사용하여 용액 내의 금속 나노와이어들을 합성하기 위한 방법들이 제공된다. 반응 혼합물은 금속 염, 유기 환원제, 및 용매를 갖는 용액으로 제공될 수 있고, 용매는 표면 리간드를 포함하거나 표면 리간드로 구성된다. 유기 환원제, 예컨대 벤조인은 금속 염의 금속 이온들을 금속으로 환원하는 유기 프리 라디컬들을 형성하도록 반응 혼합물에서 분해될 수 있다. 용매의 표면 리간드는 금속 나노와이어들이 용액 내에서 형성되는 방식으로 금속과 배위 결합할 수 있다. 나노와이어들의 직경 및 모폴로지, 반응 속도, 반응 수율, 및 다른 특징들이 반응 온도 및 환원제의 화학물질과 같은 파라미터들을 조정함으로써 튜닝가능할 수도 있다.