Spotlights pubs.acs.org/JPCL
Spotlights: Volume 8, Issue 13
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STRUCTURAL COLOR PATTERNS ON PAPER FABRICATED BY INKJET PRINTERS AND THEIR APPLICATION IN ANTICOUNTERFEITING Inkjet printing is a promising strategy for the fabrication of large-scale and complex structural color patterns because of its direct-writing, low-cost, mask-free, and high-throughput features. However, the substrates for inkjet printing structural color are usually plastics, and no paper-based substrates have been reported. Wu et al. (10.1021/acs.jpclett.7b01372) developed a convenient inkjet printing method to fabricate large-scale computer-designed structural color patterns on paper without any pretreatment using inks containing monodisperse cadmium sulfide spheres. Using this method, the authors obtained single-color and multicolor structural color patterns on paper. They also found that invisible patterns can be made by using inks containing uniform cadmium sulfide spheres with different diameters but the same intrinsic color. The prepared patterns can appear clearly and disappear when the viewing angle is changed, requiring no external stimuli, which makes the obtained structural color patterns highly desirable for anticounterfeiting applications.
amount of time, is fundamental to the success of theoretical and computational chemistry. DFT can capture the quantum nature of electrons, but the exact mathematical form of the interactions between electrons within DFT is not known and must be estimated. These approximations are successful in many cases, but they fail when electronic interactions play a prominent role. Vuckovic and Gori-Giorgi (10.1021/acs.jpclett.7b01113) approached the problem from a different perspective: They looked at the limit at which the interaction between the electrons becomes infinitely strong, which has been studied carefully in recent years. This limit has the advantage of unveiling the mathematical DFT structure of the electronic interactions. The authors simplified and rescaled this structure to make it suitable to describe systems with finite interaction, and they applied their new construction to simple, yet illustrative, chemical examples to show the potential of their approach for overcoming longstanding DFT limitations.
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pH-DEPENDENT INVERSION OF HOFMEISTER TRENDS IN THE WATER STRUCTURE OF THE ELECTRICAL DOUBLE LAYER Silica and water are two of the most abundant materials on Earth, and elucidating the structure of the silica/water interface is crucial for understanding the phenomena that play significant roles in chemical separations as well as geochemical, petrochemical, environmental, and biological processes. Changing the pH and electrolyte composition greatly affects the structure of water at the silica/aqueous interface, which can influence macroscopic properties, including the dissolution rates of silica. Several studies have identified specific ion effects on silica, but the pH dependence of these effects has not been studied at the molecular level. DeWalt-Kerian et al. (10.1021/ acs.jpclett.7b01005) used vibrational sum frequency generation (SFG) to specifically probe the amount of aligned water at this interface in the presence of different cationic species from pH 2−12. The SFG intensity trends observed at neutral pH (Cs+< K+ < Na+< Li+) matched reported behavior for cation adsorption on silica, but these trends were strikingly reversed at low and high pH for the different ions. The authors attribute this inversion of SFG trends to pH-dependent changes in cation adsorption, which alter the electrical double layer capacitance and in turn the local potentials that align water. The results indicate that specific cation effects are highly pHdependent, a finding that has implications for electrical double layer models that use pH-independent parameters.
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REVEALING THE CHEMISTRY AND MORPHOLOGY OF BURIED DONOR/ACCEPTOR INTERFACES IN ORGANIC PHOTOVOLTAICS Buried interfaces are the building blocks of many devices that surround us, including transistors, solar cells, and batteries. In fact, in some cases, the interfaces represent the devices themselves, thus playing a defining role in their performance. Understanding the complex chemistry and morphology of donor/acceptor interfaces in organic photovoltaics (OPVs) long plagued by low efficiencies and stability issues, yet highly affordableappears to be the main obstacle to designing materials with improved performance, stability, and lifetime. Most progress in OPV device performance has been achieved by trial-and-error preparation procedures that have led to complex and largely unknown morphologies. Griffin et al. (10.1021/acs.jpclett.7b00911) demonstrate a chemical imaging methodology that combines both experimental high spatial sensitivity and chemical selectivity with advanced theoretical modeling that can analyze the three-dimensional composition and morphology of virtually any device. Allowing both the precise measurement of composition and direct visualization of film morphology with depth, their approach reveals the intricate buried donor/acceptor interface of a model organic solar cell. The technique can identify and quantify the donor/acceptor interface length, which is crucial for device performance but has not been measured previously due to the lack of a viable methodology.
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SIMPLE FULLY NONLOCAL DENSITY FUNCTIONALS FOR ELECTRONIC REPULSION ENERGY Density functional theory (DFT), a formalism that makes quantum mechanical calculations doable in a reasonable © 2017 American Chemical Society
Published: July 6, 2017 2976
DOI: 10.1021/acs.jpclett.7b01510 J. Phys. Chem. Lett. 2017, 8, 2976−2976
