November 2017 - ACS Axial | ACS Publications

Tailoring MoS2 Exciton–Plasmon Interaction by Optical Spin–Orbit Coupling

A single-atom-thick monolayer of Molybdenum disulfide is a two-dimensional material with remarkable electronic and optical properties, notes a paper in ACS Nano. These properties make it an ideal candidate for a wide range of optoelectronic applications. However, the atomic monolayer thickness poses a significant challenge in MoS2 photoluminescence emission due to weak light–matter interaction. In this video, the Nanosmart Team from Peking University describe MoS2 photoluminescence modification via optical spin-orbit coupling. The result is a way to manipulate MoS2 light–matter interaction actively and can be further applied in the spin-dependent light-emitting devices at the nanoscale.

ACS Publications Enhances ACS Mobile App

As a service to our global audience of chemistry researchers, students, and educators, ACS Publications introduced the ACS Mobile App in 2010. The app gave the global chemistry community access to new research from ACS Publications on leading mobile platforms. We recently enhanced the ACS Mobile App to ensure it is compatible with the latest version of iOS on Apple devices.

The ACS Mobile App provides you with a customizable live stream of new peer-reviewed chemistry research articles from all ACS journals. You can also access the latest news from Chemical & Engineering News, ACS’s industry-leading magazine, and preeminent chemistry news source. ACS Mobile is also a great complement to ACS2Go, ACS Publications’ mobile optimized website. ACS2Go gives you access to the full portfolio of ACS Publications research, with papers dating all the way back to 1879. You can also easily pair ACS2Go with your institution’s library.

If you haven’t downloaded the the ACS Mobile App to your mobile yet, the app is freely available at leading app stores! With this app for your iOS and Android devices you can quickly browse all the groundbreaking new chemistry research from ACS Publications. Download the app today to stay current with ACS chemistry research!

Other ACS Mobile App features include:

  • Alerts for newly published ACS chemistry research papers from all ACS journals
  • Filtering options for viewing content from selected ACS titles
  • Delivery of an indexed list of more than 40,000 chemistry research articles published annually, complete with graphical and text abstracts
  • Automatic saving of chemistry research abstracts for offline reading
  • A “Latest News” feed featuring stories from Chemical & Engineering News
  • Access to full-text articles for users at institutions that subscribe to ACS journals
  • Easy tools for sharing articles via social media, as well as email

Download the ACS Mobile App for iOS and Android Devices Now!

Video: Taking a Closer Look at Crystal Engineering of Self-Assembled Porous Protein Materials in Living Cells

Crystalline porous materials have been investigated for development of important applications in molecular storage, separations, and catalysis. The potential of protein crystals is increasing as they become better understood. Protein crystals have been regarded as porous materials because they present highly ordered 3D arrangements of protein molecules with high porosity and wide range of pore sizes. However, it remains difficult to functionalize protein crystals in living cells.

In this video, Professor Takafumi Ueno and Assistant Professor Satoshi Abe of the School of Life Science and Technology, Tokyo Institute of Technology, describe their research, which was recently published in ACS Nano. They discuss recent results regarding functionalization of protein crystals produced in insect cells. Porous protein crystals were designed and constructed for adsorption of exogenous molecules in living cells.

Get more great videos from ACS.

What Chemists Do: Outco’s Markus Roggen

What are chemists doing to legitimize new industries? Markus Roggen, Vice President of Extraction at Outco, works to make doses of medical marijuana more consistently effective, delivering a more reliable product to the public.

The What Chemists Do video series highlights just how many different careers are possible with a background in chemistry. Watch more videos.

Learn more about recent cannabis chemistry reasearch.

Supercharged Bleach Powers Greener Oxidations

Run-of-the-mill liquid bleach, aqueous NaOCl, is an attractive green option for industrial oxidations. It’s cheap, doesn’t tend toward explosive reactions like hydrogen peroxide, doesn’t require metal catalysts, and its waste product is table salt. But it is tough to work with and inefficient on a large scale. Now researchers have determined that an extra-pure, crystallized bleach—sodium hypochlorite pentahydrate—oxidizes more efficiently, often with higher yield and selectivity, than dilute aqueous bleach.

Aqueous bleach readily breaks down, so every use requires a titration to determine its current strength. Large-scale reactions also require huge volumes because NaOCl can’t be used at concentrations higher than 13% by weight; higher concentrations degrade too quickly to be useful. Finally, its high pH 13 slows down many reactions.

A few years ago, researchers at Nippon Light Metal (NLM) figured out a way to manufacture a more concentrated and stable form of NaOCl. Sodium hypochlorite pentahydrate was first described in 1919, but not until Nippon researchers found a way to make it on an industrial scale in 2013 did it become practical for industry. The light-yellow crystal is 44% NaOCl by weight, has a pH of around 11, and is stable for a year when stored in the refrigerator.

In new research funded by the company, Yoshikazu Kimura of Iharanikkei Chemical Industry Company, Masayuki Kirihara of Shizuoka Institute of Science & Technology, and coworkers, including at NLM, explored using sodium hypochlorite pentahydrate versus aqueous bleach in a variety of industrial oxidations.

The crystal is “a superior substitute” to aqueous bleach, Kimura says, because of its higher efficiency, stability, and ease of use. The catalyzed oxidation of bulky secondary alcohols to ketones is “an especially remarkable example,” Kimura adds. When catalyzed by tetrabutylammonium hydrogen sulfate and a nitroxyl-radical-based catalyst known as TEMPO, oxidation of 2-octanol to 2-octanone with liquid bleach yields only 11% after 22 hours. But with the crystalline form, the yield was 97% after just one hour. The crystal also made possible some reactions that don’t work with aqueous bleach at all, such as oxidative cleavage of trans-diols to diketones.

This article is reproduced with permission from C&EN (© American Chemical Society). The article was first published on November 17, 2017.

Snakeskin-Like Material Molts When Damaged

Imagine a raincoat that heals a scratch by shedding the part of the outer layer that’s damaged. To create such a material, scientists have turned to nature for inspiration. Roland Hönes, Vitaliy Kondrashov, and Jürgen Rühe report a water-repellant material that molts like a snake’s skin when damaged to reveal another hydrophobic layer beneath it. Their work appears in the paper, “Molting Materials: Restoring Superhydrophobicity after Severe Damage via Snakeskin-like Shedding” published in the ACS journal Langmuir.

Watch a Video Exploring this Molting Material

Lotus leaves, water striders and other superhydrophobic examples from nature have inspired scientists to copy their water-repelling architecture to develop new materials. Such materials are often made by coating a substrate with nanostructures, which can be shored up by adding microstructures to the mix. Superhydrophobic surfaces could be useful in a range of applications including rain gear, medical instruments and self-cleaning car windows. But most of the prototypes so far haven’t been strong enough to stand up to damage by sharp objects. To address this shortcoming, Jürgen Rühe and colleagues again found a potential solution in nature — in snake and lizard skins.

The researchers stacked three layers to create their material: a water-repellant film made with poly-1H,1H,2H,2H-perfluorodecyl acrylate (PFA) “nanograss” on the top, a water-soluble polymer in the middle and a superhydrophobic silicon nanograss film on the bottom. Nanograss consists of tiny needle-like projections sticking straight up. The team scratched the coating and submerged the material in water, which then seeped into the cut and dissolved the polymer. The top layer then peeled off like molted skin and floated away, exposing the bottom, water-repellant film. Although further work is needed to strengthen the top coating so that a scratch won’t be able to penetrate all three layers, the researchers say it offers a new approach to creating self-cleaning and water-repellant materials.

Looking at Latin America’s Challenges in Innovation and STEM Education

Recently, I got a fantastic opportunity to participate in the SciFinder Future Leaders program sponsored by CAS, a division of the American Chemical Society. I shared the experience with 21 Ph.D. students and postdoctoral researchers from around the world. We got to share our experiences and ideas about how to build a brighter future through chemistry.

The program offered twelve days of memorable moments and learning in areas such as innovation, information management for scientists, marketing, and alternative careers in science. The experience made me think about the current situation in Latin America. I considered how the valuable lessons we learned from the SciFinder Future Leaders program could be used to build a brighter future in that region.

Latin American countries have around 20 million students in their higher education systems, most of them studying in the three biggest countries of the region: Argentina, Brazil, and Mexico. However, less than 17% of graduates in the region attained STEM degrees. According to a 2015 report from The Organisation for Economic Co-operation and Development (OECD), Mexico is the exception in the region with 24% of graduates attaining STEM degrees, one of the highest levels in the world. On the other hand, some countries in the region have fewer than 10% of their graduates focusing on STEM areas.

This lack of focus on STEM is a problem. It is not a secret that countries require science and technology education and investment for societal development and economic growth. It is essential for the region to bring more students to the STEM field. Addressing these problems will require a mixture of public and private policies, such as more scholarships and incentives to study in STEM fields.

A second valuable lesson I took from the SciFinder Future Leaders program that I would apply in Latin America is the need to incentivize innovation. The world has changed; never before has it been so urgent to incorporate new solutions to solve our old problems. During the program, we had a session dedicated to the study of innovation to solve our daily problems as students, or researchers, or even as a society. It was awesome to discover how many brilliant ideas can emerge when a small group of researchers and students are sitting together, and the environment promotes creativity.

How many ideas would see the light of day in Latin America if we could create an environment that supports innovation? It is not a secret that our region is at the bottom of the list when it comes to promoting innovative ideas. While some countries, such as Chile and Costa Rica, have some advantages, even their situation is not so different. Also, it is common to find authors from the region working on successful ventures in other parts of the world. Latin American societies need to take action to support innovation. They must create conditions that allow the development of new ideas and initiatives, fostering startups, non-governmental organizations, and companies focused on IT or science and technology.

I believe Latin America has serious challenges to overcome. We cannot break through these barriers if we continue thinking in the same old manner. We need to think of new ways to solve our persistent problems. This is the way Latin America can research its full potential.

Gabriela Gonzalez received her Bachelor of Science degree from the Central University of Venezuela. She is currently a Ph.D. student at the University of Campinas in Brazil and a social entrepreneur. She created the becas_la Instagram account to increase Latin American students’ awareness of scholarships and other opportunities.

Learn more about the SciFinder Future Leaders program.

Understanding Wine “Legs,” the Marangoni Effect and Minibot Motors

As wine enthusiasts know, the “legs” or “tears” that run down a glass after a gentle swirl can yield clues about a wine’s alcohol content. Interestingly, the physical phenomenon — called the Marangoni effect – responsible for creating these tears can be harnessed for practical applications. Scientists have developed little motors that can run based on this phenomenon. The team reported this work the paper “Marangoni Effect-Driven Motion of Miniature Robots and Generation of Electricity on Water,” published in ACS’ journal Langmuir.

Watch a Video on the Marangoni Effect and Its Applications

Miniature robots in water have been shown to clean up pollutants and perform other useful tasks. But fueling them has been a challenge. One promising method to propel little machines through water involves using chemical reactions to produce bubbles, which then get ejected and push the robots around. However, this approach requires the use of expensive catalysts. To eliminate the catalysts but still propel the machines on water, Lidong Zhang and colleagues turned to the Marangoni effect in which fluid moves due to changes in surface tension.

To build their minimotors, the researchers created concentrated droplets of polyvinylidene fluoride (PVDF) and dimethyl formamide (DMF) that, due to the Marangoni effect, rotate rapidly on water. Testing showed that the droplets could propel paper goldfish hundreds of centimeters without emitting any pollutants into the air. Also, with the addition of an electromagnetic generator, the kinetic energy could be converted to electrical energy, a feature that could broaden the propeller’s applicability.

Pressure Pumps Up Protein Reaction Yields

Protein-based drugs are often used to treat conditions such as multiple sclerosis, hemophilia, or gout. But if used in their native form, they can be short-lived or trigger harmful inflammation. To prevent this, drugmakers attach polyethylene glycol (PEG), a polymer that stabilizes therapeutic proteins and enhances their efficacy, to specific sites within the protein—a reaction known as PEGylation. Now, scientists report that performing the reaction under high-pressure conditions can make it vastly more efficient, bumping up yields of PEGylated proteins from 5 to 90%.

Although it’s well known that increasing pressure can speed up reactions, using high pressure to modify proteins is “not very conventional,” says Alexander Wei of Purdue University, who was not involved with the study. “This is not the sort of thing that a protein chemist might typically do, so it’s a nice insight into how one can modify proteins.”

One challenge when attaching PEG to specific sites on a protein is that the typical target amino acids are embedded deep within the protein’s folds and thus are inaccessible. Increasing pressure can temporarily unfold the protein, exposing the target sites for the chemical reaction. Yongdong Liu and Zhiguo Su of the Chinese Academy of Sciences tested the effects of pressure on PEGylation of human ciliary neurotrophic factor (CNTF), a protein that has been previously shown to reversibly refold at high pressure.

The researchers found that gradually increasing pressure during the PEGylation reaction increased yields so that at a pressure of 250 megapascals, 90% of the protein was PEGylated. Lower pressures didn’t improve the reaction’s efficiency as much, and the protein remained permanently unfolded at too-high pressures.

To confirm that PEG was attached to the correct site on the protein—in this case, a cysteine molecule—the team digested PEGylated and non-PEGylated CNTF with an enzyme and checked the size of the fragments using high-pressure size exclusion chromatography. Only the fragment containing the cysteine residue had increased in size, suggesting that this is where PEG had attached.

The conventional process of adding PEG to proteins takes several hours and can be expensive because large amounts of reagent are used. “What impressed me with this study was that they can do this modification really fast with almost no excess reagent,” says Nicole Nischan, a postdoctoral scholar at the University of Texas Southwestern Medical Center, who was not involved with the study.

Processing proteins under high pressure is simple and already approved for the food industry by the U.S. Food & Drug Administration, she adds. In future studies, researchers will need to analyze whether proteins that have PEG molecules added under high-pressure function as well as those made in the conventional manner.

Although the approach may work for other proteins as well, “some proteins may be more sensitive to hydrostatic pressure than others, so they may not be able to regain structure if you applied pressure,” Wei says.

This article is reproduced with permission from C&EN (© American Chemical Society). The article was first published on November 21, 2017.

Celebrate Thanksgiving with Cranberry Sauce — And Pectin Chemistry Research!

Thanksgiving is here, so it’s only natural to have food — and the chemistry behind it — on the brain! Thanksgiving is a time for gratitude and enjoying being with family and friends, but the meal can also spur disagreement, such as whether canned or homemade cranberry sauce is superior. Regardless of where you stand on that issue, Thanksgiving is the perfect time to explore the chemistry behind a key molecule in this holiday treat: pectin.

Pectin is a naturally occurring polysaccharide polymer and is used in food as a gelling agent. It has an array of beneficial uses beyond cranberry sauce, some of which are outlined in the following selection of articles from Biomacromolecules and Journal of Agriculture and Food Chemistry.

Give Thanks for Pectin Chemistry and Have a Happy Thanksgiving


Effects of Pectin Molecular Weight Changes on the Structure, Dynamics, and Polysaccharide Interactions of Primary Cell Walls of Arabidopsis thaliana: Insights from Solid-State NMR
Biomacromolecules, 2017, 18 (9), pp 2937–2950
DOI: 10.1021/acs.biomac.7b00888
Zooming in: Structural Investigations of Rheologically Characterized Hydrogen-Bonded Low-Methoxyl Pectin Networks
Biomacromolecules, 2015, 16 (10), pp 3209–3216
DOI: 10.1021/acs.biomac.5b00870
Aeropectin: Fully Biomass-Based Mechanically Strong and Thermal Superinsulating Aerogel
Biomacromolecules, 2014, 15 (6), pp 2188–2195
DOI: 10.1021/bm500345u
Microfluidics-Assisted Diffusion Self-Assembly: Toward the Control of the Shape and Size of Pectin Hydrogel Microparticles
Biomacromolecules, 2014, 15 (5), pp 1568–1578
DOI: 10.1021/bm401596m

Journal of Agriculture and Food Chemistry

Highly Methoxylated Pectin Improves Insulin Resistance and Other Cardiometabolic Risk Factors in Zucker Fatty Rats
J. Agric. Food Chem., 2008, 56 (10), pp 3574–3581
DOI: 10.1021/jf703598j
Antioxidant Activity and Emulsion-Stabilizing Effect of Pectic Enzyme Treated Pectin in Soy Protein Isolate-Stabilized Oil/Water Emulsion
J. Agric. Food Chem., 2011, 59 (17), pp 9623–9628
DOI: 10.1021/jf202020t
Effects of Lecithin and Pectin on Riboflavin-Photosensitized Oxidation of Orange Oil in a Multilayered Oil-in-Water Emulsion
J. Agric. Food Chem., 2011, 59 (17), pp 9344–9350
DOI: 10.1021/jf2015107
Biocompatible Polyelectrolyte Complex Nanoparticles from Lactoferrin and Pectin as Potential Vehicles for Antioxidative Curcumin
J. Agric. Food Chem., 2017, 65 (28), pp 5720–5730
DOI: 10.1021/acs.jafc.7b01848
A New Water-Soluble Nanomicelle Formed through Self-Assembly of Pectin–Curcumin Conjugates: Preparation, Characterization, and Anticancer Activity Evaluation
J. Agric. Food Chem., 2017, 65 (32), pp 6840–6847
DOI: 10.1021/acs.jafc.7b02250

What’s your favorite cranberry sauce style? Leave your preference in the comments!