The generation of hot electrons is an intrinsic property of all plasmonic nanocrystals under illumination. However, the number of such excited electrons will strongly depend on the shape, material, and excitation wavelength. In this paper, we develop a practical self-consistent formalism to describe the generation of energetic electrons in a plasmonic nanocrystal with an arbitrary shape. We apply our formalism to gold nanospheres, nanorods, and nanostars. Among the investigated shapes, the nanostar geometry demonstrates the best performance, with an internal energy efficiency of ∼25%. This superior capability of hot-electron generation in the nanostars comes from the following factors: strong hot spots in the red spectral region, isotropic optical response, and the absence of interband transitions at the plasmonic resonance. Spherical gold nanocrystals show strong interband absorption at the plasmon resonance, and the related efficiency of the generation of hot holes in the d band can reach a level of 70%. By analyzing the energy performance of nanocrystals under CW illumination, we show that the most relevant parameter to consider is the rate of hot-electron generation, whereas the steady-state numbers of thermalized and nonthermalized electrons play secondary roles. The physical principles formulated in this study can be used to design a variety of plasmonic nanomaterials for applications in photocatalysis and photodetection.
We present a comprehensive review of recent developments in the field of chiral plasmonics. Significant advances have been made recently in understanding the working principles of chiral plasmonic structures. With advances in micro- and nanofabrication techniques, a variety of chiral plasmonic nanostructures have been experimentally realized; these tailored chiroptical properties vastly outperform those of their molecular counterparts. We focus on chiral plasmonic nanostructures created using bottom-up approaches, which not only allow for rational design and fabrication but most intriguingly in many cases also enable dynamic manipulation and tuning of chiroptical responses. We first discuss plasmon-induced chirality, resulting from the interaction of chiral molecules with plasmonic excitations. Subsequently, we discuss intrinsically chiral colloids, which give rise to optical chirality owing to their chiral shapes. Finally, we discuss plasmonic chirality, achieved by arranging achiral plasmonic particles into handed configurations on static or active templates. Chiral plasmonic nanostructures are very promising candidates for real-life applications owing to their significantly larger optical chirality than natural molecules. In addition, chiral plasmonic nanostructures offer engineerable and dynamic chiroptical responses, which are formidable to achieve in molecular systems. We thus anticipate that the field of chiral plasmonics will attract further widespread attention in applications ranging from enantioselective analysis to chiral sensing, structural determination, and in situ ultrasensitive detection of multiple disease biomarkers, as well as optical monitoring of transmembrane transport and intracellular metabolism.
ccording to the Chinese government, China needs a minimum of 120 million hectares of arable land to feed its people. That is the 'red line' for food security that officials have pledged to protect. So it may seem like good news that the most recent comprehensive survey of national land use in China has reported a healthy surplussome 135 million hectares of the country are classed as planted with crops-rice paddy fields, irrigable land and dry farms. Simultaneously, total grain production hit a record 602 million tonnes in 2013, after a decade of continuous growth. I fear these figures are not as positive as they seem. Moreover, I worry that they may create a false sense of security and encourage policy-makers to relax efforts to protect China's arable land. We should not be misled by the superficial surplus. The story is not so simple. Although the quantity of arable land in China seems healthy, there are serious concerns about its quality-and of its ability to supply future generations with enough food. I was involved in the land-use assessmentthe second National Land Resource Survey of China-and am pleased to see the results published and discussed. The survey completed its work in 2009, but the previous central government declined to publish the results, because members did not agree with the findings of the first such survey, finished in 1996. This is not unusual. Surveys to classify large areas of remote land are difficult. A study published in December suggested that the area of cropland abandoned since 1990 in western Russia, Belarus and Ukraine has been severely underestimated. When President Xi Jinping came to power in 2012, he investigated the discrepancy in the Chinese figures and decided that the results of the second survey were robust, because they are based on high-resolution remote sensing and backed up by investigation on the ground. He authorized China's land and resources ministry (MLRC) to release the results at the end of 2013. At a press conference on 30 December, officials from the MLRC pledged to continue to protect arable land, and reinforced their commitment to the food security red line. Beyond the headline figures, there are some worrying trends. Although the overall area of arable land has increased in the time between the two surveys, the quality of the land, and so its suitability, has decreased. Some 3 million hectares of high-quality arable land and some 1 million hectares of paddy land have been built on or converted to urban use in just over a decade. More than 3 million hectares have been contaminated with pollution. The effects were shown starkly last year, when heavy metals such as cadmium appeared on the tables of restaurants as a result YULAN LI
Novel furoxan-based nitric oxide (NO) releasing derivatives of oleanolic acid (OA) were synthesized for potential therapy of liver cancers. Six compounds produced high levels of NO in human hepatocellular carcinoma (HCC) cells and exhibited strong cytotoxicity selectively against HCC in vitro. Treatment with 8b or 16b significantly inhibited the growth of HCC tumors in vivo. These data provide a proof-in-principle that furoxan/OA hybrids may be used for therapeutic intervention of human liver cancers.
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