A.J. Drexel Nanotechnology Institute

The A.J. Drexel Nanotechnology Institute (DNI) was established in January 2003 to coordinate interdisciplinary research, education and outreach, and strategic partnerships in nanotechnology for all of Drexel University.

Links:

  – A.J. Drexel Nanotechnology Institute

Projects

MXenes

MXenes are a family of two-dimensional (2D) inorganic compounds with the general formula of M_n+1X_nT_x, where M is an early transition metal, X is carbon and/or nitrogen, and T is a functional group on the surface of a MXene (typically O, OH and F) (M. Naguib, et al. Adv. Mater., 2014, 26, 992). MXenes have the high metallic conductivity of transition metal carbides, and are (unlike other 2D materials like graphene) hydrophilic because of their hydroxyl- and oxygen-terminated surfaces. MXenes were first discovered in 2011 at Drexel University, as a result of selectively etching the A layer out of bulk ternary transition metal carbides and nitrides, known as MAX phases, which yields multilayered MXenes. To increase surface area and accessibility of its surface, multilayered MXenes typically undergo further processing to yield solutions of delaminated MXenes.

Due to their hydrophilicity, MXenes can be processed in aqueous and polar organic solvents to form stable colloidal solutions that can be filtered to form freestanding films and spray-coated to form transparent conductive coatings. This provides a greater of potential applications for this family of materials. The first MXene discovered was Ti₃C₂ and it was initially investigated for its electrochemical properties in batteries and supercapacitors (B. Anasori, et al. Nature Reviews Materials, 2017, 2, 16098). In the past several years, however, over two dozen MXenes have been discovered along with dozens of other applications.

The wearable artificial kidney (WAK) is considered to be a potential candidate offering better quality of life to patients with end-stage renal disease. The key technology, also a major challenge, is the adsorbent system for dialysate regeneration. MXene 2D nanosheets are made of two to four atomic layers of a transition metal interleaved with carbon or nitrogen with surface terminations bonded to the outer metallic layers. The combination of a core transition-metal carbide with surface terminations makes MXenes conductive clay-resembling materials. This suggests that the MXene structure could potentially be fine-tuned to adsorb specific molecules by optimizing the interatomic and interlaminar distance of the material. Additionally, because MXene surfaces are terminated with −OH, −O−, and −F, their affinity with adsorbates could be further enhanced by forming hydrogen bonds on the surface. Therefore, we are devoted to developing a MXene-based adsorbent system to remove uremic toxins from dialysate and even blood directly. As the first step, we have demonstrated that urea, one of the most important uremic toxins, can be rapidly and selectively removed by MXene from aqueous solution and spent dialysate. What’s more, healthy donor hemocompatibility assays showed that MXene Ti3C2Tx has no significant impact on blood clotting, hemolysis, and platelet activation, indicating MXenes are safe to use for blood-contacting applications. 

Light Control by MXenes 

Ever consider what a two way mirror or an anti-reflective coating is made from? How can we control light to perform in the way we wish? Beyond simple transmission of light, MXenes have been shown to exhibit saturable absorption properties in the near infrared (near-IR), meaning the absorption of light decreases (transmission of light increases) with increasing light intensity. This property was used to create a photonic diode with fullerenes (C₆₀), which performed by transmitting light differently when viewed in the forward and reverse directions. Saturable absorption properties can be applied in applications such as lasers and tuned when we take advantage of disks/pillar-like nanostructures at near-IR or terahertz frequencies.

Transparent Conductors

What if every window harvested solar energy, was able to control the room temperature by adjusting the window color, and did it all without sacrificing visibility? In the visible and near-IR regimes, MXenes transmit EM waves and the quantity of transmission is directly dependent on the MXene composition and thickness of material present. This permits MXenes to be used as transparent conductors in energy storage and display applications. Furthermore, the color and transparency of the device reversibly changes with applied potential allowing for electrochromic devices (and maybe windows!) to be fabricated with different colors. 

Lithium-ion batteries are already a dominant technology in portable and flexible electronics industry. However, the cost and democratic reserves of Li resources raise the concerns for the future electrification and large-scale energy storage. Going “beyond Li-ion technology” needs robust electrodes for reversible (de) intercalation of metal-ions. As MXenes offer spontaneous intercalation of a variety of cations (Na+, K+, Mg+2, Zn+2, Ca+2 and Al+3), they could be the potential alternatives to conventional carbon and metal oxide materials for the design of hybrid metal capacitors and multi-valent batteries.

Can we downscale the energy storage devices for powering of microelectronics?

The current trend of emerging Internet of Things (IOT) and miniaturization of electronics demand for developing small scale energy storage devices. Scalable manufacturing of On-chip MXene devices can offer compatible integration with micro robotics, sensors and bio-medical implants. Additionally, transparent conducting behavior and color changing properties make MXenes suitable for developing transparent and electrochromic energy storage devices. Furthermore, MXenes can be used for flexible and wearable applications where MXene composites can combine the roles of energy storage, harvesting and sensing capabilities.

Interview: 

Q: Explain the role of nanotechnology in the development of your organization or department.

Although much has changed since Drexel University was founded in 1891, the original mission of the university still rings true today, and the introduction and use of new technologies is at the forefront of Drexel University initiatives.  As such, nanotechnology provides a platform for students and faculty to explore new interdisciplinary research, maintain a cutting-edge knowledge-base in curriculum development, and further opportunities for regional as well as international collaboration.  

Q: How has nanotechnology impacted the products or services you provide?

The rise of nanotechnology has enabled new collaborative and team research projects, and invigorated our Engineering curriculum.  Nanotechnology has become integrated with many of our research activities, curriculum, and faculty interests.    

Q: Briefly describe a current project involving nanotechnology, and what your anticipated outcome will be (new process, new product, etc.)

In the Electrical and Computer Engineering Dept., Prof. Adam Fontecchio and his graduate student Jared Coyle are developing a photovoltaic paint composed of nano sized droplets of liquid crystal dispersed in a polymer.  This ‘Solar Paint’ has the potential to revolutionize how we power our homes and vehicles in the future.  We are currently exploring methods for incorporating the photovoltaic material into commercial and residential paints, roofing shingles, and transparent coatings for windows on both homes and vehicles.  When applied, the products will transform surfaces that are currently aesthetic into active components that better all of our lives.    

Q: Where do you see nanotechnology applications leading in the future? 

The opportunities for nanotechnology are endless, spanning traditional disciplines, interdisciplinary activities, and projects involving unique combinations of skills not yet envisioned.  In the next 20 years, we should expect to see innovations in renewable energy, clean water, computer technologies, and biomedicine, to name just a few.      

Q: What advice would you offer to someone who wanted to work at your organization in 3-5 years?  

Anyone interested in nanotechnology would do well to take courses in math, physics, and chemistry.  In addition, participating in research activities related to nanotechnology can provide a good background for graduate work in the area.  I would also suggest to students that they keep up with current trends in technology – there are plenty of sources of information that are accessible to everyone regardless of background or technical education, and a few of my favorites to recommend include Wired magazine, The New York Times technology section, and Science Friday on National Public Radio (available as a podcast as well as live on the radio).

Q:  What industry do you think has been impacted the most by nanotechnology thus far? Why?

At this point the biggest impact has been in the biomedical field.  New pharmaceuticals to fight cancer, viruses, and many other diseases have stemmed from nanotechnology research.  In addition, nanocharacterization methods such as Scanning Probe Microscopy, Scanning Electron Microscopy, and X-Ray Spectroscopy and Diffraction are providing clues as the fundamental processes of biological systems.  We are currently experiencing breakthroughs in DNA analysis and sequencing of the Human Genome, which will offer new possibilities in individualized medicine.

Q:  What industry do you think has the greatest future potential to be impacted by nanotechnology?  Why?  

The growth in biomedical nanotechnology will continue to grow and impact all of our lives.  At the same time, alternative energy generation and storage is seeing advances in basic research and development that will grow to impact the whole world.  The current world economic difficulties in addition to the finite petroleum reserves force us to consider new ideas and techniques to provide electric power through photovoltaics; energy scavenging systems based on thermal gradients, vibrational energy, and waste thermal discharge.  These breakthroughs will be driven be global necessity, and the impact of nanotechnology on alternative energy will be as great as we are currently seeing in the biomedical field.

(Content source: Drexel University website, press releases, and interview.)