Spotlights pubs.acs.org/JPCL
Spotlights: Volume 8, Issue 2
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QUANTUM TUNNELING: THE LONGER THE PATH, THE LESS TIME IT TAKES When you are planning to walk from point A to meet a friend for coffee at point B, common sense tells you to take the shortest path to increase your chances of getting there while the brew is still hot. Everyone knows that the shortest path takes the least time. Not so with quantum tunneling! In his Letter (10.1021/acs.jpclett.6b02692), Pollak shows that, with quantum tunneling, it is faster to traverse a long distance than a short distance. His results indicate a shorter tunneling time as the width of the potential barrier increases. Pollak presents a general formalism for the study of quantum transition time probability distributions and shows the effect of friction on quantum tunneling dynamics. The formalism was applied to the quantum mechanics of a parabolic barrier. Using an initial thermal distribution, the author demonstrates that the probability distribution shifts to shorter times as the temperature is reduced and tunneling is increased. When the temperature is low and tunneling dominates the dynamics, increasing the length of the path traversed decreases the transition time. The introduction of friction to the problem does not “destroy” the phenomenon that the transition time becomes shorter as the distance increases, except when the friction coefficient is very large. This work may add to the knowledge gained from attosecond ionization experiments that have been conducted in recent years.
new methods for practical field diagnostics and thereby help to prevent the diffusion of various infectious diseases.
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GATE-INDUCED INSULATOR TO BAND-LIKE TRANSPORT TRANSITION IN ORGANOLEAD HALIDE PEROVSKITE Methylammonium lead iodide perovskite (CH3NH3PbI3) has been recently extensively studied for its remarkable potential in solution-processable solar cells and other diverse optoelectronic applications such as photodetectors, lasers, and light-emitting diodes. Understanding the intrinsic charge transport in organolead halide perovskites is essential for the development of high-efficiency photovoltaics and other optoelectronic devices. Despite the rapid advancement of the organolead halide perovskite in photovoltaic and diversity optoelectronic applications, the intrinsic charge carrier transport in these materials remains elusive partly due to the difficulty of fabricating electrical devices and obtaining good electrical contact. In their Letter (10.1021/acs.jpclett.6b02841), Li et al. report the successful fabrication of monolayer graphenecontacted field-effect transistors (FETs) from individual methylammonium lead triiodide perovskite microplates and describe a systematical investigation of charge transport of the monolayer graphene-contacted FETs. They found that an insulator to band-like transport transition occurs by varying the gate voltage, which depends on the orthorhombic-to-tetragonal phase transition temperature and defect densities. These findings may have practical implications in the development of electronic and optoelectronic devices for use in lowtemperatures, such as on satellites and airplanes.
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OPTICAL TRAP-MEDIATED HIGH-SENSITIVITY NANOHOLE ARRAY BIOSENSORS WITH RANDOM NANOSPIKES Chipotle made headlines in 2015 after hundreds of their customers fell ill after dining in their U.S. restaurants, but many other lower-profile outbreaks occur annually, caused by produce, meat, and even ice cream. Foodborne illness sickens millions of people every yearand it kills hundreds of thousands. Outbreaks can be hard to identify because viruses move faster than both diagnosis and reporting, and research is ongoing to develop faster and more sensitive detection methods. In their Letter (10.1021/acs.jpclett.6b02262), Yoshikawa et al. describe the mechanism underlying the possibility of achieving high-sensitivity optical biosensors for use in virus detection. The authors investigated the possibility of a highly sensitive virus sensor based on a nanohole array modified with random nanospikes in conjunction with optical guiding of viruses using greatly enhanced light-induced force under the extraordinary optical transmission modulated by the mirror image effect. They found that by trapping the viruses in that region, the peak shift caused by virus adhesion could be doubled, when compared with a conventional nanohole array in the absence of random nanospikes. Using this method, rapid and sensitive virus detection was efficiently realized, even in cases of low virus concentrations. The work presented could lead to the development of localized light-guided nanohole array sensors based on this trapping effect and the resulting enhanced spectral peak shift, which in turn may contribute to © 2017 American Chemical Society
Published: January 19, 2017 546
DOI: 10.1021/acs.jpclett.7b00066 J. Phys. Chem. Lett. 2017, 8, 546−546
