[from Science, First Release Notification for July 21]
Proton-Coupled Energy Transfer in Molecular Triads
Abstract
A photochemical mechanism was experimentally discovered and denoted proton-coupled energy transfer (PCEnT). A series of anthracene–phenol–pyridine triads formed the local excited anthracene state after light excitation at ca. 400 nm, which led to fluorescence around 550 nm from the phenol–pyridine unit. Direct excitation of phenol–pyridine would have required light around 330 nm, but the coupled proton transfer within the phenol–pyridine unit lowered its excited state energy so that it could accept excitation energy from anthracene. Singlet-singlet energy transfer thus occurred despite the lack of spectral overlap between the anthracenefluorescence and the phenol–pyridine absorption. Moreover, theoretical calculations indicated negligible charge transfer between the anthracene and phenol–pyridine units. PCEnT was suggested as an elementary reaction of possible relevance to biological systems and future photonic devices.
A neural network that teaches itself the laws of physics could help to solve some of physics’ deepest questions. But first it has to start with the basics, just like the rest of us. The algorithm has worked out that it should place the Sun at the centre of the Solar System, based on how movements of the Sun and Mars appear from Earth.
The machine-learning system differs from others because it’s not a black that spits out a result based on reasoning that’s almost impossible to unpick. Instead, researchers designed a kind of ‘lobotomized’ neural network that is split into two halves and joined by just a handful of connections. That forces the learning half to simplify its findings before handing them over to the half that makes and tests new predictions.
A long-awaited experimental result has found the proton to be about 5% smaller than the previously accepted value. The finding seems to spell the end of the ‘protonradius puzzle’: the measurements disagreed if you probed the proton with ordinary hydrogen, or with exotichydrogen built out of muons instead of electrons. But solving the mystery will be bittersweet: some scientists had hoped the difference might have indicated exciting new physics behind how electrons and muons behave.
This week is a special one for all of us at Nature: it’s 150 years since our first issue, published in November 1869. We’ve been working for well over a year on the delights of our anniversary issue, which you can explore in full online.
A century and a half has seen momentous changes in science, and Nature has changed along with it in many ways, says an Editorial in the anniversary edition. But in other respects, Nature now is just the same as it was at the start: it will continue in its mission to stand up for research, serve the global research community and communicate the results of science around the world.
Nature creative director Kelly Krause takes you on a tour of the archive to enjoy some of the journal’s most iconic covers, each of which speaks to how science itself has evolved. Plus, she touches on those that didn’t quite hit the mark, such as an occasion of “Photoshop malfeasance” that led to Dolly the sheep sporting the wrong leg.
Scientific glassblower Terri Adams uses fire and heavy machinery to hand-craft delicate scientific glass apparatus. “My workbench hosts an array of tools for working with glass, many of which were custom-made for specific jobs,” says Adams. “Each tool reminds me of what I first used it for and makes me consider how I might use it again.” (Leonora Saunders for Nature)
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