Song Jin

Bio: Song Jin is an academic researcher from University of Wisconsin-Madison. The author has contributed to research in topics: Nanowire & Perovskite (structure). The author has an hindex of 84, co-authored 275 publications receiving 31826 citations. Previous affiliations of Song Jin include Wisconsin Alumni Research Foundation & Cornell University.

Enhanced Hydrogen Evolution Catalysis from Chemically Exfoliated Metallic MoS2 Nanosheets

Abstract: Promising catalytic activity from molybdenum disulfide (MoS2) in the hydrogen evolution reaction (HER) is attributed to active sites located along the edges of its two-dimensional layered crystal structure, but its performance is currently limited by the density and reactivity of active sites, poor electrical transport, and inefficient electrical contact to the catalyst. Here we report dramatically enhanced HER catalysis (an electrocatalytic current density of 10 mA/cm2 at a low overpotential of −187 mV vs RHE and a Tafel slope of 43 mV/decade) from metallic nanosheets of 1T-MoS2 chemically exfoliated via lithium intercalation from semiconducting 2H-MoS2 nanostructures grown directly on graphite. Structural characterization and electrochemical studies confirmed that the nanosheets of the metallic MoS2 polymorph exhibit facile electrode kinetics and low-loss electrical transport and possess a proliferated density of catalytic active sites. These distinct and previously unexploited features of 1T-MoS2 make ...

Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors

Abstract: The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm(-2)) and high quality factors (Q ∼ 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 10(16) cm(-3). Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials.

Nanostructured silicon for high capacity lithium battery anodes

Abstract: Nanostructured silicon is promising for high capacity anodes in lithium batteries. The specific capacity of silicon is an order of magnitude higher than that of conventional graphite anodes, but the large volume change of silicon during lithiation and delithiation and the resulting poor cyclability has prevented its commercial application. This challenge could potentially be overcome by silicon nanostructures that can provide facile strain relaxation to prevent electrode pulverization, maintain effective electrical contact, and have the additional benefits of short lithium diffusion distances and enhanced mass transport. In this review, we present an overview of rechargeable lithium batteries and the challenges and opportunities for silicon anodes, then survey the performance of various morphologies of nanostructured silicon (thin film, nanowires/nanotubes, nanoparticles, and mesoporous materials) and their nanocomposites. Other factors that affect the performance of nanostructured silicon anodes, including solvent composition, additives, binders, and substrates, are also examined. Finally, we summarize the key lessons from the successes so far and offer perspectives and future challenges to enable the applications of silicon nanoanodes in practical lithium batteries at large scale.

High-Performance Electrocatalysis Using Metallic Cobalt Pyrite (CoS2) Micro- and Nanostructures

Abstract: The development of efficient and robust earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) is an ongoing challenge. We report metallic cobalt pyrite (cobalt disulfide, CoS2) as one such high-activity candidate material and demonstrate that its specific morphology—film, microwire, or nanowire, made available through controlled synthesis—plays a crucial role in determining its overall catalytic efficacy. The increase in effective electrode surface area that accompanies CoS2 micro- and nanostructuring substantially boosts its HER catalytic performance, with CoS2 nanowire electrodes achieving geometric current densities of −10 mA cm–2 at overpotentials as low as −145 mV vs the reversible hydrogen electrode. Moreover, micro- and nanostructuring of the CoS2 material has the synergistic effect of increasing its operational stability, cyclability, and maximum achievable rate of hydrogen generation by promoting the release of evolved gas bubbles from the electrode surface. The benefits of ca...

Efficient hydrogen evolution catalysis using ternary pyrite-type cobalt phosphosulphide

Abstract: The scalable and sustainable production of hydrogen fuel through water splitting demands efficient and robust Earth-abundant catalysts for the hydrogen evolution reaction (HER). Building on promising metal compounds with high HER catalytic activity, such as pyrite structure cobalt disulphide (CoS2), and substituting non-metal elements to tune the hydrogen adsorption free energy could lead to further improvements in catalytic activity. Here we present a combined theoretical and experimental study to establish ternary pyrite-type cobalt phosphosulphide (CoPS) as a high-performance Earth-abundant catalyst for electrochemical and photoelectrochemical hydrogen production. Nanostructured CoPS electrodes achieved a geometrical catalytic current density of 10 mA cm(-2) at overpotentials as low as 48 mV, with outstanding long-term operational stability. Integrated photocathodes of CoPS on n(+)-p-p(+) silicon micropyramids achieved photocurrents up to 35 mA cm(-2) at 0 V versus the reversible hydrogen electrode (RHE), onset photovoltages as high as 450 mV versus RHE, and the most efficient solar-driven hydrogen generation from Earth-abundant systems.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Combining theory and experiment in electrocatalysis: Insights into materials design

Abstract: BACKGROUND With a rising global population, increasing energy demands, and impending climate change, major concerns have been raised over the security of our energy future. Developing sustainable, fossil-free pathways to produce fuels and chemicals of global importance could play a major role in reducing carbon dioxide emissions while providing the feedstocks needed to make the products we use on a daily basis. One prospective goal is to develop electrochemical conversion processes that can convert molecules in the atmosphere (e.g., water, carbon dioxide, and nitrogen) into higher-value products (e.g., hydrogen, hydrocarbons, oxygenates, and ammonia) by coupling to renewable energy. Electrocatalysts play a key role in these energy conversion technologies because they increase the rate, efficiency, and selectivity of the chemical transformations involved. Today’s electrocatalysts, however, are inadequate. The grand challenge is to develop advanced electrocatalysts with the enhanced performance needed to enable widespread penetration of clean energy technologies. ADVANCES Over the past decade, substantial progress has been made in understanding several key electrochemical transformations, particularly those that involve water, hydrogen, and oxygen. The combination of theoretical and experimental studies working in concert has proven to be a successful strategy in this respect, yielding a framework to understand catalytic trends that can ultimately provide rational guidance toward the development of improved catalysts. Catalyst design strategies that aim to increase the number of active sites and/or increase the intrinsic activity of each active site have been successfully developed. The field of hydrogen evolution, for example, has seen important breakthroughs over the years in the development of highly active non–precious metal catalysts in acid. Notable advancements have also been made in the design of oxygen reduction and evolution catalysts, although there remains substantial room for improvement. The combination of theory and experiment elucidates the remaining challenges in developing further improved catalysts, often involving scaling relations among reactive intermediates. This understanding serves as an initial platform to design strategies to circumvent technical obstacles, opening up opportunities and approaches to develop higher-performance electrocatalysts for a wide range of reactions. OUTLOOK A systematic framework of combining theory and experiment in electrocatalysis helps to uncover broader governing principles that can be used to understand a wide variety of electrochemical transformations. These principles can be applied to other emerging and promising clean energy reactions, including hydrogen peroxide production, carbon dioxide reduction, and nitrogen reduction, among others. Although current paradigms for catalyst development have been helpful to date, a number of challenges need to be successfully addressed in order to achieve major breakthroughs. One important frontier, for example, is the development of both experimental and computational methods that can rapidly elucidate reaction mechanisms on broad classes of materials and in a wide range of operating conditions (e.g., pH, solvent, electrolyte). Such efforts would build on current frameworks for understanding catalysis to provide the deeper insights needed to fine-tune catalyst properties in an optimal manner. The long-term goal is to continue improving the activity and selectivity of these catalysts in order to realize the prospects of using renewable energy to provide the fuels and chemicals that we need for a sustainable energy future.

Chemistry and properties of nanocrystals of different shapes.

Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH3NH3PbI3

Abstract: Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors.