News and Thoughts:

Goodbye Northwestern, it has been a wonderful time.

hood

After a long period of job searching, I am delighted to take the post at Cardiff University starting from January 2019.  I am deeply indebted to all my mentors, colleagues, friends, and family for their help and support during this process.  Working on photo energy researches during the past 6 and a half years in Northwestern has been a wonderful experience.  It is a true privilege to collaborate the brightest minds (you know I am talking about you!) on the daily basis and be able to access to the cutting-edge technologies.  My views to science and its interplay with education and society got to grow and mature, and they are the best gift that I will bring with across the Atlantic Ocean and pass them onto my future coworkers.

Judging at Intel ISEF 2017

ISEF17

“Science’s rightful place is in service of society” (D. Sarewitz, 2013) is always a big part of my belief.  This summer, I was very fortunate to participate as a Chemistry Grand awards judge in the International Science and Engineering Fair (ISEF), the biggest science fair in the world.

Although science fair was a huge thing in my high school, I wasn’t doing so well as many of my high school classmates, and ISEF 2017 is the first time for me to see such a high-level competition.  I was very impressed by one high schooler’s perseverance with identifying an undocumented ferric sulfate compound from the reaction of sulfuric acid and gold ore, which he obtained from hiking; by the applicability of the algorithm that another student developed to filter and assign signals in high-dimensional protein NMR spectroscopy to accelerate drug discovery (and by his smartness, too); and by the usefulness of silk fibers as moisture-activated torsional actuators discovered by the other student, and by many other projects.

The judges caucus is another special experience.  We are composed of industrial scientists, university professors, researchers, postdocs, and PhD students.  Some had participated more science fairs than the others; we discussed all(!) the projects and tried to persuade(!) our colleagues why one project is better/worse.  The voting/discussion cycle repeated again and again until all the prizes were decided.  (Awarded students, you should really thank the eloquent and passionate judges who lobby for your project!)

Judging ISEF was overall a great experience, especially seeing/feeling the pure enthusiasm for the science of all the students, and I am very glad I could contribute and help.  Thanks to my grad school friend Grace for the invitation!

Ethylhexyl in real life.

As a “purist”, I never really like to see any 2-ethylhexyl substituent in my molecules, as it usually has an undefined stereogenic center at the 2 position.  Materials incorporating such a functionality thus are random mixtures(!) of (R)- and (S)- stereoisomers, not to mention molecules possessing multiple 2-ethylhexyl substituents.

Materials scientists, especially aromatic polymer chemists, use 2-ethylhexyl to enhance the solubility, as such a bulky subsituent disrupts pi-stacking/aggregation.  Outside of the research labs, as it turns out, molecules with 2-ethylhexyl are actually ubiquitous in our daily life; I wonder if those 2-ethylhexyls were implemented also for modulating the aggregation properties.

Just to name a few, 2-ethylhexyl nitrate (2-EHN) is a cetane improver added to diesel fuels, bis(2-ethylhexyl) phthalate, which is produced approx. 3 billion kg/year, is a plasticizer for PVC, and octocrylene and octyl methoxylcinnamate are ingredients in sunscreen products that absorb UVB and UVA.  Without a doubt, I should have given ethylhexyl much more credits!

We know so little, so little indeed, about solubility.

PDI is a notoriously insoluble dye, and it is well known that linear aliphatic N-substituents won’t make it much more soluble.  However, the Grozema group published a mind-blowing work back in 2014 (DOI: 10.1039/c4cc00330f) and totally turn down this common believe (along with other important findings, of course).  See the picture!  I knew this work for quite a while (thanks Pat for showing me this paper), and still couldn’t make sense out of it.  This just shows how little we know about intermolecular interaction; there is more to learn!

pdi_ester

DNA nucleobase to form crystalline porous organic framewroks.

Continuing our work of G-quadruplex-driven self-assembly, we found that the same strategy can be used to guide the formation of highly crystalline organic frameworks consisted of segregated donor/acceptor chromophore pi-stacks.  The materials display, in addition to high porosity, facile carrier generation and mobility, and can be applied as the cathode material in lithium-ion batteries.   The joint force of scientists from three departments (Hupp/Farha @ Chem., Snurr @ Chem. Eng. and Hersam @ Mat Sci.) made this work possible.  Thanks, everyone!

Alkyl groups modulate π-stacking interactions: size is not the only thing that matters.

The group of Ken Shimizu at the University of South Carolina reported a very interesting finding: the strength of repulsive and/or attractive interactions between π-stacked aromatics can be non-trivially influenced by the alkyl substituents.  Should the interacting area (surface contact area) between aromatics be large enough, even those bearing tBu substituents can display stronger attraction than those bearing Me one!   

Does methanol dissolve silica?  Maybe not, suggested by Biotage.

This is an age-old question for people using MeOH in their flash chromatography.  I guess the answer/result might have something to do with the pore size of the frit of your column.  Anyhow, have a look at an interesting analysis conducted in Biotage.

Singlet fission in multi-crystalline diketopyrrolopyrrole (DPP) derivatives observed

The nice work of Pat reports the one of the first observation and thorough study of singlet fission processes in DPP materials, a common class of industrial pigments.  This work opens a new direction for SF study (DOI: 10.1021/acs.jpcb.5b10565).

Photo-induced charge transfer in G-quadruplexes continues to fascinate the JACS readers

After our first G-quadruplex paper in 2013, photoinduced charge transfer in self-assembled, monodispersed G-quadruplex of a donor-acceptor triad was highlighted again in JACS Spotlight (DOI:10.1021/jacs.5b02864 , and DOI:10.1021/ja4093727 for the 2013 paper)! The combined transient absorption, stimulated Raman, and electron paramagnetic spectroscopies suggested the hole delocalization in the H-bonded cyclic guanine moieties (DOI: 10.1021/jacs.5b00977).