Nav: Home

Towards high quality ZnO quantum dots prospective for biomedical applications

December 03, 2019

Nanocrystalline zinc oxide (ZnO) is currently one of the most commonly used semiconductor metal oxide nanomaterials due to its unique catalytic and electro-optical characteristics. The inherent and distinctive physicochemical properties of ZnO nanostructures are dependent on a variety of factors that are determined by the applied synthetic procedure and the character of the resulting nanocrystal-ligand interface. Thus, the preparation of stable ZnO nanostructures, especially nanoparticles with sizes below 10 nm, i.e. quantum dots (QDs), with desired physicochemical properties still remains a huge challenge for chemists. Recently, scientists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) and Warsaw University of Technology (WUT) in cooperation with the Interdisciplinary Research Institute of Grenoble (IRIG) used dynamic nuclear polarization (DNP)-enhanced solid state nuclear magnetic resonance (NMR) spectroscopy for detailed characterization of the organic-inorganic interfaces of ZnO QDs prepared by the traditional sol-gel process and the recently developed one-pot self-supporting organometallic (OSSOM) procedure. In parallel, investigations were carried out on the design and preparation of bio-stable ZnO QDs along with the determination of their structure-biological activity relationship. These studies were published in the high-impact journals "Angewandte Chemie" and "Scientific Reports".

"We wanted to unambiguously confirm that ZnO QDs prepared in our laboratory using the OSSOM approach are of unprecedentedly high quality," recounts co-author of both papers, Dr. Ma?gorzata Wolska-Pietkiewicz. "Up to now, ZnO QDs have been commonly produced by a sol-gel process. However, the main disadvantage of this traditional method is the low reproducibility, which likely inhibits both the uniformity of particle morphology and organic ligand shell composition. Consequently, the resulting nanostructures are essentially unstable and tend to aggregate. In my opinion, this has significantly limited potential applications of nanocrystalline ZnO in various technologies," adds Dr. Wolska-Pietkiewicz.

"An alternative to the omnipresent sol-gel method are highly promising wet-organometallic approaches. Recently developed in our laboratory, the OSSOM procedure is based on the controlled exposition of a well-defined organozinc precursor to air. The OSSOM process is thermodynamically controlled and occurs at room temperature," says Professor Janusz Lewi?ski. To highlight the superiority of the organometallic approach for the preparation of ZnO QDs, both the procedure-driven properties as well as the structures of the organic ligand shells of QDs prepared by both the OSSOM approach and the sol-gel procedure were compared. For this purpose scientists applied the DNP-NMR method that is being developed in the group of Dr Gaël De Paëpe (IRIG). "This NMR technique allows us to study nanomaterials' interfaces with atomic precision and thus to demonstrate the difference between tested materials," continues Dr. Daniel Lee and adds that the ability to determine the exact nature and structure of the interface gives a valuable insight into future designs for new and fully stable functional nanomaterials. In addition, DNP-NMR measurements are relatively fast and take only a few hours. This really isn't much, especially compared to conventional NMR spectroscopy, which (in the case of measurements with comparable resolution) would require ... about a year.

"The OSSOM method leads to the formation of ZnO QDs coated with strongly anchored and highly-ordered organic coatings. Contrastingly, on the surface of sol-gel derived ZnO nanostructures, coating ligand molecules are randomly distributed," Dr. Wolska-Pietkiewicz points out. What is more, ligands could be easily removed from the surface of QDs derived from sol-gel process, changing the properties of the resulting nanomaterial. "In our method, the surface is super-protected, and QDs are stable. As a result, the OSSOM approach affords high-quality ZnO QDs with unique physicochemical properties, which are prospective for biological applications," adds Dr. Wolska-Pietkiewicz.

Why it is so important?

"This preliminary study has only just scratched the surface (pun intended) of what can be achieved." - says Dr. Lee. "We have shown that being able to study nanomaterials' surface stability at an atomic scale enables the understanding of how to provide their stability, which is extremely important from the point of view of subsequent applications: from sensors and optical devices to targeted drug delivery and nanomedicines."

"In the near future, we could design, for example, safe and effective drug nanocarriers for cancer therapies, in which we would be able to deposit appropriately selected, active molecules within our ordered organic layer. Positioning is important especially for targeted therapies, e.g. photodynamic therapy, because it allows the drug to be released evenly in a particular environment and at the right speed. In addition, owing to the achieved ligands ordering, we are able to pack a lot of active drug particles on a small carrier" adds Professor Lewinski.

Institute of Physical Chemistry of the Polish Academy of Sciences

Related Quantum Dots Articles:

'Growing' active sites on quantum dots for robust H2 photogeneration
Chinese researchers had achieved site- and spatial- selective integration of earth-abundant metal ions in semiconductor quantum dots (QDs) for efficient and robust photocatalytic H2 evolution from water.
New insights into the energy levels in quantum dots
Researchers from Basel, Bochum and Copenhagen have gained new insights into the energy states of quantum dots.
What a pair! Coupled quantum dots may offer a new way to store quantum information
Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have for the first time created and imaged a novel pair of quantum dots -- tiny islands of confined electric charge that act like interacting artificial atoms.
Spinning quantum dots
A new paper in EPJ B presents a theoretical analysis of electron spins in moving semiconductor quantum dots, showing how these can be controlled by electric fields in a way that suggests they may be usable as information storage and processing components of quantum computers.
Controlling the charge state of organic molecule quantum dots in a 2D nanoarray
Australian researchers have fabricated a self-assembled, carbon-based nanofilm where the charge state (ie, electronically neutral or positive) can be controlled at the level of individual molecules.
Modified quantum dots capture more energy from light and lose less to heat
Los Alamos National Laboratory scientists have synthesized magnetically-doped quantum dots that capture the kinetic energy of electrons created by ultraviolet light before it's wasted as heat.
Using quantum dots and a smartphone to find killer bacteria
A combination of off-the-shelf quantum dot nanotechnology and a smartphone camera soon could allow doctors to identify antibiotic-resistant bacteria in just 40 minutes, potentially saving patient lives.
Synthesizing single-crystalline hexagonal graphene quantum dots
A KAIST team has designed a novel strategy for synthesizing single-crystalline graphene quantum dots, which emit stable blue light.
US Naval Research Laboratory 'connects the dots' for quantum networks
Researchers at the US Naval Research Laboratory developed a novel technique that could enable new technologies that use properties of quantum physics for computing, communication and sensing, which may lead to 'neuromorphic' or brain-inspired computing.
Quantum rebar: Quantum dots enhance stability of solar-harvesting perovskite crystals
Engineering researchers have combined two emerging technologies for next-generation solar power -- and discovered that each one helps stabilize the other.
More Quantum Dots News and Quantum Dots Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at