Spotlights Cite This: J. Phys. Chem. Lett. 2018, 9, 6143−6143
pubs.acs.org/JPCL
Spotlights: Volume 9, Issue 20
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J. Phys. Chem. Lett. 2018.9:6143-6143. Downloaded from pubs.acs.org by 5.8.47.153 on 11/05/18. For personal use only.
SPECTROSCOPY AT THE NANOSCALE The recorded history of spectroscopy dates back to Sir Isaac Newton’s work in the 17th century, which paved the way for the discovery of ultraviolet, infrared, and visible light and eventually scientific advances including mass spectrometry and NMR. Today, nanoscience is changing the landscape, allowing spectroscopic study on a much smaller scale than Newtown could have imagined. There are several examples of spectroscopy at the nanoscale in this issue of The Journal of Physical Chemistry Letters.
light on the basic monomer of bacterial photosynthetic PPC systems, Bacteriochlorophyll a. Their control experiment allowed them to assign the origins of coherences in PPCs, and they report that many of the coherences observed in PPCs are vibrations in the pigment monomer, a finding that may clear up previous misconceptions caused by a lack of signals in previous studies.
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NEAR-FIELD SPECTROSCOPY OF NANOSCALE MOLECULAR AGGREGATES Molecular aggregates, self-assembled on surfaces at the nanoscale, are promising candidates for applications ranging from organic light-emitting diodes to light harvesting and sensing and beyond. The strong long-range interaction between the constituent molecules of molecular aggregates leads to delocalized eigenstates, where excitation is shared coherently by many molecules. Most eigenstates are inaccessible by conventional optical spectroscopy, so Gao and Eisfeld (10.1021/acs.jpclett.8b02482) theoretically investigated the advantages of a spatially localized electromagnetic field for the optical spectroscopy of molecular aggregates. They were able to obtain new information on the eigenfunctions and gain access to states that are optically forbidden by far-field selection rules. The authors report that their results should remain valid for other molecules and other transparent dielectric surfaces and thus could lead to new methods for investigating the optical and transport properties of molecular aggregates.
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IMAGE CORRELATION SPECTROSCOPY WITH SECOND HARMONIC GENERATING NANOPARTICLES IN SUSPENSION AND IN CELLS Higher-harmonic generating nanoparticles are a promising material for prolonged and label-free correlation spectroscopy studies, especially in a biological/biomedical context, due to their high contrast and the absence of fluorescence-related problems such as photobleaching, blinking, and saturation. Slenders et al. (10.1021/acs.jpclett.8b02686) applied the coherent intensity fluctuation model to study the mobility of second harmonic generating nanoparticles. They present a method for quantifying the diffusion coefficient from a single spectroscopy measurement without the need for separate point-spread-function calibrations, and they illustrate the technique using LiNbO3 nanoparticles. The authors performed label-free raster image correlation spectroscopy imaging in aqueous suspension and spatiotemporal image correlation spectroscopy in A549 human lung carcinoma cells, and their findings supported the expected theoretical result. Because quantitative characterization of the mobility of nanoparticles is crucial for an understanding of nanoparticle biokinetics in living systems, the findings could contribute to applications for deep-tissue imaging, tissue engineering, wound healing, and environmental nanoparticle exposure studies.
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TUNABLE ELECTRON-INJECTION CHANNELS OF HETEROSTRUCTURED ZNSE@CDTE NANOCRYSTALS FOR SURFACE-CHEMISTRY-INVOLVED ELECTROCHEMILUMINESCENCE Semiconductor nanocrystals (NCs) have been extensively employed in solution-processed optoelectronic devices such as photovoltaic cells, photodetectors, and light-emission devices. Although NCs can be easily injected with charges via electrochemical redox, controlling charge transfer and understanding charge-transfer channels has been a challenge. He et al. (10.1021/acs.jpclett.8b02645) combined potential- and spectrum-resolved electrochemiluminescence (ECL) strategies to investigate the electron-injecting channels of specially designed heterostructured ZnSe@CdTe NCs, and they achieved tunable electron-injecting channels via surface chemistry with configurational ions. The authors found that the radiative charge recombination of heterostructured ZnSe@ CdTe NCs occurred only within their CdTe core section, and both potential- and spectrum-resolved ECL results showed that configurational ions in ECL solution could bring out one, two, and even three different electron-injecting channels under given conditions. The findings may prove helpful in the design of novel electrochemiluminophores.
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COHERENCES OF BACTERIOCHLOROPHYLL a UNCOVERED USING 3D ELECTRONIC SPECTROSCOPY A comprehensive understanding of the earliest energy-transfer processes in naturally occurring photosynthetic systems has eluded researchers despite extensive efforts across many fields. Although a detailed picture of the structure and kinetics is known, much ambiguity remains in which design principles enable such remarkable efficiencies in these molecular machines. For example, it is known that pigment−protein complexes (PPCs) perform actions including light absorption, transfer, and charge separation, but less is known about the potential energy surfaces of PPCs. Even with sophisticated optical tools, basic properties such as the role of electronic and vibrational degrees of freedom cannot be unambiguously assigned. Two-dimensional electronic spectroscopy has shown coherences in a variety of PPCs, but researchers have been unable to assign the nature of the states involved. In their Letter, Irgen-Gioro et al. (10.1021/acs.jpclett.8b02217) shed © 2018 American Chemical Society
Published: October 18, 2018 6143
DOI: 10.1021/acs.jpclett.8b03114 J. Phys. Chem. Lett. 2018, 9, 6143−6143
