Spotlights Cite This: J. Phys. Chem. Lett. 2018, 9, 902−902
pubs.acs.org/JPCL
Spotlights: Volume 9, Issue 4
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QUANTUM CHEMICAL TOPOLOGY OF THE ELECTRON LOCALIZATION FUNCTION IN THE FIELD OF ATTOSECOND ELECTRON DYNAMICS The Space Race ended decades ago, but a renewed fever for space exploration is heating up. Books and movies such as Hidden Figures and The Martian have brought both real and fictional scientists and astronauts into the zeitgeist, and businessmen like Elon Musk and Richard Branson are branching out into space tourism. Through its Orion program, NASA plans to launch humans on a mission to Mars in 2032, a mere 14 years from now. One of the challenges facing NASA is galactic cosmic radiation, a form of ionizing radiation (IoR) that can cause health issues including cancer and bone problems, especially over long periods of exposure. Of course, IoRs are enormously useful in other areas, such as hadron therapies in cancer treatment and sterilization in agroindustry. Innovative numerical simulations are required to understand the earliest physical chemical steps after irradiation, and research is ongoing to understand the interaction of IoRs with matter and their subsequent ultrafast consequences. Parise et al. (10.1021/ acs.jpclett.7b03379) set out to decipher the attosecond response of molecules’ electron clouds submitted to IoRs. They developed a quantum chemical topology of the electron localization function (ELF) for attosecond dynamics, with a special emphasis on irradiation of molecules by alpha particles in the keV−MeV energy range. Their method enables qualitative and quantitative characterization of the formation/ breaking of bonds between nuclei, electron flows among topological basins, or the attachment of electron density to the colliding particle. To illustrate the strength of their approach, they successively considered collision of water or of a DNA base (guanine) by alpha particles and analyzed the evolution of the ELF topological basins in combination with other descriptors of the electron dynamics.
I−III−VI2 semiconductor QDs. Most notably, these materials exhibit a localized surface plasmon resonance in the 2.4 eV region of the spectrum. The energy of this resonance is sensitive to the dielectric environment of the QDs, making it interesting for sensing applications. The presence of free carriers is further evidenced by the cooling dynamics of CuFeS2 QDs as well as by the absence of a measurable photocurrent in these materials. The authors also note that the presence of free carriers in these materials is linked to surface passivation. In particular, improved surface passivation was achieved by the use of room-temperature cadmium ion treatment, leading to the emergence of a photocurrent in CuFeS2 QD films. The results suggest that CuFeS2 QDs may be suited for applications such as thermoelectrics and conductive layers in a variety of devices.
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WHY DOES CUFES2 RESEMBLE GOLD? According to the old saying, “all that glitters is not gold”, and it’s true that plenty of 49ers were disappointed by fool’s gold in the American west. But sometimes the material that resembles gold can turn out to be even more useful, as in the case of CuFeS2, a naturally occurring mineral that is recognizable by its characteristic golden luster. CuFeS2 quantum dots (QDs) have been shown to be efficient thermoelectric and photovoltaic transport layers, and their benign, environmentally friendly composition may offer a viable substitute for semiconductors composed of heavier elements. However, their use in devices has been stymied by their unusual chemical, optical, and physical behavior. Although CuFeS2 behaves as a semiconductor, its bulk and nanoscale forms bear an uncanny resemblance to metallic gold; in fact, researchers have yet to reach a consensus on whether the material is a metal or a semiconductor. Sugathan et al. (10.1021/acs.jpclett.7b03190) address this question through an extensive spectroscopic, structural, and computational study. They observed several peculiarities of CuFeS2 QDs that distinguish them from other © 2018 American Chemical Society
Published: February 15, 2018 902
DOI: 10.1021/acs.jpclett.8b00404 J. Phys. Chem. Lett. 2018, 9, 902−902
