Luminescent carbon nanoparticles based on carbon exhibit advantageous optical properties. They are also biocompatible, and therefore better suited for imaging procedures in the biosciences than metal-based semiconductor quantum dots.
A variety of processes have thus been developed to make these miniature objects known as carbon dots or C-dots. Chinese researchers have now introduced a new method in the journal Angewandte Chemie, by which C-dots can be produced particularly quickly and inexpensively. In addition, they have demonstrated the use of these luminescent dots as printer ink.
The new process is based on plasma-induced pyrolysis. A plasma is a gas whose components have been partially or completely separated into ions and electrons. This plasma is highly reactive and energetic; its uses include plasma welding, for which it serves as the heat source. A team led by Su Chen at Nanjing University of Technology directed a special plasma beam onto a small amount of egg yolk or egg white in order to carbonize the material. Within a few minutes, they formed C-dots with a yield of about 6 %.
The C-dots obtained from the egg yolk have a crystalline structure and a diameter of about 2.2 nm; those from the egg white are amorphous and measure about 3.4 nm. They contain mainly graphitic structures. Oxygen and nitrogen atoms are also bound to the surface in various ways, allowing for good solubility in a broad range of aqueous and organic solvents.
The C-dots are not sensitive to acids or bases. Under UV light, they fluoresce bright blue. It is presumed that the luminescence comes from passivated surface defects that “trap” the excitatory UV light like antennae.
The researchers were able to follow the pyrolytic process by means of thermogravimetric analysis and IR spectroscopy: it includes the uncoiling and breaking down of proteins as well as various chemical reactions. Towards the end, primarily carbon dioxide, ammonia, and water are released. “This process is not limited to eggs,” explains Chen, “it works with many inexpensive natural carbon sources, including sugars.”
The scientists fabricated inks based on the luminescent C-dots and printed glowing patterns on a variety of surfaces by both inkjet and silk-screen printing processes. The addition of small amounts of organic dyes or semiconducting quantum dots allows the color of the ink to be varied. “Such fluorescent inks may be useful in optoelectronic applications,” says Chen, “for example in forgery-proof labeling and optoelectronic sensor applications.”
Author: Su Chen, Nanjing University of Technology (China), mailto:email@example.com
Title: Amphiphilic Egg-Derived Carbon Dots: Rapid Plasma Fabrication, Pyrolysis Process, and Multicolor Printing Patterns
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201204381
Su Chen | Angewandte Chemie
Scientists call for improved technologies to save imperiled California salmon
14.12.2017 | NOAA Fisheries West Coast Region
Cardiolinc™: an NPO to personalize treatment for cardiovascular disease patients
14.12.2017 | Luxembourg Institute of Health
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
14.12.2017 | Life Sciences
14.12.2017 | Life Sciences
14.12.2017 | Health and Medicine