The Chemistry of Smell

We all learned about our five senses in grade school—sight, hearing, touch, taste, and smell. And as we got older, we learned more about what actually causes these senses to be activated. When light bounces off of an object, our eyes receive that light and we call it sight. When vibrations travel through the air, our eardrums vibrate too and our brain interprets the sound. Touch and taste are equally straightforward; when we brush up against something or put food in our mouth we touch and we taste. But what causes smells? We could just say aromas are in the air. But what is it that actually triggers our brain to recognize a scent?

The answer is small molecules and a little bit of chemistry.

Olfaction, A.K.A. Smell

The scientific word for smell is olfaction, and this process is facilitated by the olfactory system. You’ve probably noticed that “olfact-” is code for “has to do with smell;” we’ll keep using this code word as we talk about what triggers our sense of smell.

In any case, there are a lot of parts to the olfactory system. The most interesting of these parts are the olfactory receptors. These receptors are part of specialized brain cells that span from your nasal cavity, across your olfactory epithelium (a type of skin), and directly to your brain. Humans have about 12 million of these receptors while animals known for their sense of smell—like dogs—have 1 billion or more.

Courtesy of Rice University

These olfactory receptors are what receive smells and allow your brain to interpret them. But, this still doesn’t answer the question of what actually causes smells.

Small Molecules, Big Smells

When we sense a smell in the air, we’re actually sensing the presence of small, vaporized molecules. So, when you smell a flower, baking bread, or your smelly gym socks, you’re actually sensing molecules that have evaporated from the surface of those objects. These molecules move through the air and into your nose. Then, they bind with a specific set of olfactory receptors and generate a signal in your brain, triggering you to recognize that specific smell.

Courtesy of eSchoolToday

Not all materials can vaporize easily. That’s why materials like metal tend not to have a strong smell. There are also some molecules that humans don’t have odor receptors for. Gases like carbon monoxide and natural gas are odorless not because they’re not vapors, but because we simply don’t have the receptors to smell them.

All Molecules Are Not Created Equal

Not surprisingly, there are many, many different kinds of odor-causing molecules. There are also about 340 different types of odor receptors in humans that work together in different combinations to identify specific smells. Even in your home, there can be many different odor-causing molecules floating around. However, there are a few key molecules that when filtered out of your air can greatly improve your indoor air quality.


Ammonia and ammonia-related compounds have a characteristic, pungent smell. And in large quantities ammonia can be dangerous. But in homes, this gas often comes from a variety of minor sources and is an annoyance rather than a danger. Ammonia can come from cleaners, cat urine, older refrigerators, and fertilizers used near your home.


Formaldehyde levels in homes are typically low, but the smell of formaldehyde can be noticeable even at these low levels. This gas makes its way into homes through particleboard and plywood, cigarette smoke, and some dyes and preservatives. It is also a main ingredient in some insulation found in homes from the 1970s and 1980s.

Sulfur Compounds

Sulfur compounds, specifically hydrogen sulfide, are responsible for rotten egg smells in your home. If you’ve ever lived in a home that used well water you’re probably very familiar with this smell. While hydrogen sulfide is not dangerous at low levels—and the human nose can detect very low levels of this gas—it’s definitely a nuisance.

Homeowners have options when it comes to eliminating smells in their homes. Candles and air fresheners are often the first line of defense against home odors. But, now that we know that odors are actually caused by certain molecules in the air, there are some better options.

Rather than cover up odors the best option is to eliminate odor-causing molecules altogether. The easiest way to do this is to simply add odor-molecule trapping capabilities to the filters you already use in your home. Serionix manufactures filters like this, made to fit easily into your home furnace system. These filters were originally designed for cleanrooms and are incredibly effective at removing airborne chemicals. Using a filter like this gives you the cleanest possible air for your home!



What is Adsorption?

We know that the air in our homes can have unwanted contaminants in it; that’s why we use filters. But not all filters were created equally. High efficiency furnace filters and portable air purifiers do a great job removing things like pollen and pet dander from the air. Unfortunately, even though pollen and pet dander are small from our perspective, in terms of air quality they are actually rather big when compared to other air contaminants. Other hazards like bacteria, viruses, and irritating chemicals are much, much smaller. Trying to capture them with conventional filters is the microscopic equivalent of trying to catch minnows with a tuna net.  The chemicals we can’t capture using filters are often the most noticeable indicators of air quality in the form of malicious odors. When Zipper the cat pees on the carpet or your collard greens go bad it’s easy to notice that your air quality is suffering.

When air passes through a filter, big particles like dust and pet hair get caught in the filter fibers. But, small chemicals pass through the filters and into the ‘clean’ air.

There is a solution, though. Some filters can trap these small bacteria, viruses, and chemicals. But what does it mean for a filter to trap these tiny chemical molecules?  What traps them? And do they stay trapped? The answer to all of these questions is adsorption.

Molecular Velcro

Adsorption is a process where a substance in a gas or liquid becomes attached to a solid surface. Of course, if you’re not a chemist this doesn’t mean much. Instead of thinking about the scientific definition, think about Velcro. Some things stick to Velcro and some don’t—and the things that do stick tend to stay stuck.

Courtesy of

Adsorption works kind of like Velcro. The surface of a solid acts as the Velcro, and the tiny chemical molecules in the air act as the things that get stuck in Velcro. So, when air passes over the right kind of solid surface, chemical molecules in the air get stuck to that surface and the cleaned air passes over. And once the molecules are stuck to the surface, they don’t come back off.

When molecules in the air pass over an adsorptive surface, they get stuck to the surface and cleaned air passes over the surface.

There are lots of materials with this special, molecular-Velcro surface. The most common one is activated carbon. Activated carbon is similar to charcoal and naturally has this molecular-Velcro surface, which makes it really good at removing chemicals from the air. But, no one wants piles of charcoal sitting in their home to remove chemicals. So what can the average homeowner use instead to make sure they’re removing unwanted chemicals from their air?

Coated Filters

The answer to this question is a coated filter. Think about a typical home furnace filter. These filters are really good at removing ‘big’ particles like dust and pet dander, but not so good at removing chemicals. But, with the addition of a coating that gives the filter the same molecular-Velcro surface that occurs naturally in activated carbon, a standard filter can remove chemicals, too.

When the filter fibers are coated to make their surface adsorptive, airborne chemicals stick to the fibers. That way, all of the contaminants—including small chemicals—are trapped.

Serionix makes filters like this. At Serionix, we’ve created a ‘special sauce’ that we add to typical home air filters. That way, our filters not only filter out the big stuff that typical filters handle but also the tiny chemicals that cause odors and irritation. With this combination of features, our filters ensure fresh, clean air in your home.

Wired In: James Langer

Story courtesy of the News Gazette’s Paul Wood.

On Sundays, staff writer Paul Wood spotlights a high-tech difference maker. This week, meet JAMES LANGER, 36, president of Serionix, which makes high-performance filtration materials for removal of toxic chemicals from air and water, with a large number of customers — from the Army to an appliance maker.

The team

My co-founders are Weihua Zheng and James Economy. Dr. Zheng and I both graduated from Dr. Economy’s research group in the Materials Science and Engineering Department at the University of Illinois. Weihua and I met in 2008 when he joined the group, and we just clicked right from the beginning. Our friendship and mutual respect grew over the next several years and eventually led us to start Serionix together. Since starting the company, we have expanded the team to include several additional engineers each with ties to UIUC. Tim Hoerr of Serra Ventures has been a great help to us — influential as both an investor and adviser since the advent of the company.

Photo by: Robin Scholz/The News-Gazette
Entrepreneur James Langer, president of Serionix, which makes high-performance filtration technologies to remove toxic or unwanted chemicals, with a purple (new) and a yellow (used) filter that can be reused in the Serionix lab at EnterpriseWorks in Champaign on Tuesday, Dec. 1, 2015.

How did you become an entrepreneur?

I think I have been intrigued by the idea of starting a company ever since I saw my dad start one when I was in middle school. His startup never took off like he’d hoped, but his experience inspired me to see entrepreneurship as a possibility.

To that end, I came to graduate school in 2006 with a vague idea of working with a startup or starting a technology company, but lost that vision somewhere along the way — mostly because I didn’t really know where to start. In January 2011, Weihua and I entered into the Cozad business plan competition on campus and instantly got hooked on entrepreneurship! Through extensive networking and pitching our business concept, we became more connected to the local entrepreneurial community and received a lot of support and feedback to refine our business concept. Over the next year, we generated significant financial support for the business through Small Business Innovation Research grants and extensions of those same grants that have provided over $2 million in total funding that we have used to bring our air filtration technology to a commercial-ready state.

What does your product do that nothing else does?

Our filtration product removes toxic and smelly compounds from air, far more efficiently than conventional products, at a price point three times cheaper. As an added kicker, the filter changes color when it runs out of life to remind a user to replace it.

What’s in the future for Serionix?

We are preparing to bring our product to market in the next year, in applications ranging from electronics cleanrooms to vehicle cabin air filters, residential pet odor removal and beyond. We are currently working with a major appliance manufacturer to design an odor filter for one of their products, and are on the cusp of getting sales and development agreements with several corporate partners.

Tech tidbits …


Twitter handle? None, yet

Favorite app? Cooks Illustrated — the recipes always work!

Book or Kindle? Book for sure. I retain information better and enjoy the feel of a book in my hand.

Wearable electronics? Just my watch!

Serionix Wins Cozad Competition

Story courtesy of News Gazette’s Don Dodson.

CHAMPAIGN — Serionix took the top monetary prize at the Cozad New Venture Competition this past weekend.

The company — which has come up with filter materials to remove perchlorate from drinking water — took first place in the Most Fundable Venture category, earning the firm $15,000.

Jim Langer, the firm’s president, said he hopes to use the winnings for intellectual property development, such as filing patent applications, or business development, such as meeting with customers on the West Coast.

Langer said Serionix started a year ago as a result of taking part in the 2011 Cozad competition. But last year, the firm didn’t make the finals.

“That served as motivation for us to work hard, and the results this year indicate it paid off,” he said.

Before taking part in last year’s competition, “we had no clear direction of what we really wanted to do, but as a result of the competition, and exposure to and connection with mentors, we were able to craft pieces for what ultimately became the company,” he said. “Cozad was the spark that set it off.”

Serionix recently won the Student Startup Award at Champaign County’s Innovation Celebration and was a finalist for the Lemelson-MIT Illinois Student Prize.

Photo By: The News Gazette
Jim Langer, left, and Weihua Zheng of Serionix, which has developed ion-exchange fiber composite materials to help remove perchlorate from drinking water.

Other monetary winners at this year’s Cozad competition included:

— GlucoSentient, which won a $10,000 prize as the Burrill Best Digital Healthcare Application. GlucoSentient aims to improve the lives of patients with asthma or chronic obstructive pulmonary disease who take theophylline. It proposes home monitoring through use of a blood glucose meter.

— Transplants Without Donors, which won a $7,500 prize as Best Social Venture. That team invented a life-saving therapy based on the creation of artificial organs from the patients’ stem cells and biomaterials.

— HigherMed, which won a $5,000 prize for second place in the Most Fundable Venture category. That team plans to develop and market an easier-to-use prescription pill bottle cap, primarily for people with decreased dexterity.

— Oso Simple Technologies and Prawg each won a $2,500 prize for Best Mobile Application. Oso Simple aims to reduce the water used on lawns and gardens, while Prawg focuses on real-time interaction between TV shows and their audiences. Prawg also won a $1,000 prize for Most Patentable Idea/Venture.

— StudyCloud won a $2,000 prize for third place in the Most Fundable Venture category. StudyCloud is an online collaboration platform poised at integrating social web technology with online education.

Twenty teams took part in the competition’s semifinals, and nine advanced to Saturday’s finals, held at the UI’s Business Instructional Facility.

The finalists were: Easy Go Dispenser, EscaWheel, GlucoSentient, HigherMed, OceanComm, Serionix, StudyCloud, Transplants Without Donors and uZee.

The annual competition is named for V. Dale Cozad, founder of Cozad Asset Management. The program was established through an endowment from Peter and Kim Fox and is administered through the UI’s Technology Entrepreneur Center.

UI Researchers Develop Effective, Less Costly Way to Remove Contaminants

Story courtesy of the News Gazette’s Don Dodson.

CHAMPAIGN — Jim Langer and Weihua Zheng have come up with a relatively inexpensive — but effective — way to remove perchlorate from water.

Perchlorate is a rocket-fuel component that has found its way into water sources, sometimes near air force bases. Exposure to it can affect the thyroid gland.

But by using “clever chemistry,” Langer and Zheng have been able to develop a filter material that can remove the contaminant from water.

The filter can be used on a faucet or in a pitcher, and the researchers see commercial potential for it.

They’ve started a company, Serionix, in the University of Illinois Research Park with their adviser,  James Economy, a UI professor emeritus of materials science and engineering.

Photo by: Vanda Bidwell/The News Gazette
Jim Langer of Serionix pours water through filter material designed to remove the rocket-fuel component perchlorate

Already, the company has received two Small Business Innovation Research grants — $150,000 from the National Science Foundation and $100,000 from the Department of Defense.

The NSF grant will be used to commercialize the technology for removal of perchlorate and possibly other contaminants from water.

The Defense Department grant will be used to develop ways of protecting facilities from chemical warfare — possibly by using the filter material in heating, ventilating and air-conditioning systems.

Langer, 32, of Urbana said the filter is made possible by composite materials known as “ion-exchange fiber composites.”

The technology involves coating tiny fibers with resin and activating the material by chemical or temperature means.

That gives the material the functionality of ion exchange. In water softeners, ion exchange is used to remove calcium and magnesium from water.

In Serionix filters, ion exchange is used to convert perchlorate to chloride.

The technology has won Serionix recognition on several levels. In February, the company won the Student Startup Award at Champaign County’s Innovation Celebration.

Last week, Langer was one of five UI finalists for the $30,000 Lemelson-MIT Illinois Student Prize, given for creative solutions to real-world problems.

Langer said Serionix is working with Champaign-based Serra Ventures to develop corporate strategies.

He figures Serionix may work with corporate partners to manufacture materials for Serionix — or the firm may license the technology so interested companies can integrate it into their products.

Among the best-known filtration products on the market today are Procter & Gamble’s PUR water filter and Clorox Co.’s Brita water filter.

“There are probably 10 or 15 more companies in that space,” Langer said.

Serionix’s material could “add functionality and marketability” to those kinds of products, he added.

In February 2011, the U.S. Environmental Protection Agency announced it would develop regulations for perchlorate in drinking water.

Just what the regulations will be isn’t clear yet. But Langer said that in developing regulations for arsenic in water, the EPA allowed small municipalities to treat water in the home, rather than centrally.

If the EPA were to take the same approach for perchlorate, Serionix’s filter could become an important “regulatory compliance tool,” he said.

Langer is the president and CEO of Serionix.

Originally from the Minneapolis area, he received a bachelor’s degree in chemistry from the University of St. Thomas in St. Paul, Minn., in 2002. He then worked four years as an analytical chemist for CIMA Labs before joining the doctoral program at the UI.

Co-founder Weihua Zheng, 26, of Savoy is originally from China’s Hebei province. He received a bachelor’s degree in chemical engineering from Zhejiang University in China in 2007. After working a year at an ion-exchange plant in China, he came to the UI in 2008.

Both credit Economy with helping them start Serionix.

“For a long time, he’s encouraged us to have an entrepreneurial mind-set,” whether in collaborating with other groups on campus or approaching companies to see what interest they may have in research, Langer said.

The latter half of the Serionix name is loosely derived from “ion exchange,” Langer said. As for the origin of the first half, “we liked how it sounded.”

Both Langer and Zheng said they plan to devote full time to Serionix after they complete their degrees.

“Definitely, I want to see this through with the company,” Langer said. “I could see myself being a professor 10 to 20 years from now, but I feel connected with the entrepreneur community here.”

Scroll Up