Korea University: A Korean research team has developed a sensor that can effectively detect one-dimensional nanotoxicity. By applying the concept of micro-cantilever resonance to the sensors to detect zinc oxide nanowires (ZnO NWs), which are nanotoxic, the team succeeded in providing the world’s first example of detection of one-dimensional nanotoxicity. The success of this endeavor is expected to contribute to further research of nanotoxicity detection.
* Micro-cantilever Resonance Sensor: A cantilever as small as a micrometer (10？？m) in length. A common example of cantilever is a diving board. The application of a resonance frequency to the cantilever leads to a resonance phenomenon. Resonance frequency, a frequency naturally occurring in all objects, is linked to mass and spring constant. The occurrence of the resonance frequency depends on the changes of mass on the surface of the sensor.
The joint research of professor Sungsoo Na (corresponding author) and Ph.D student Juneseok You (first author) from KU’s School of Mechanical Engineering, and professor Jinsung Park (corresponding author) from the Department of Control and Instrumentation Engineering in KU’s College of Science and Technology was carried out under the support of the Ministry of Science, ICT and Future Planning and the National Research Foundation of Korea. The study was published online on January 19th in Biosensors and Bioelectronics, a renowned international scientific journal.
* Research Paper Title: Label-Free Detection of Zinc Oxide Nanowire Using a Graphene Wrapping Method
In addition to their unique electronic properties known as “piezoelectric” properties, ZnO NWs also have solid-state properties. Because of these properties, ZnO NWs are one of the world’s most actively studied materials. However, in the wake of recent reports about the harmful toxicity of nano materials, ZnO NWs have been classified as toxic materials. Since one-dimensional materials have a lower dispersion retainability and surface reactivity than zero-dimensional materials after dispersion, they are difficult to detect under water. To overcome the difficulties, the research team used micro-cantilever sensors and wrapped RGO around ZnO NWs selectively, and ZnO NWs were successfully detected at concentrations a hundred times lower than those in which cells had perished.
* Piezoelectric: The result of the interaction between electrical properties and the physical transformation or cracks of a material. When the structure of the material transforms, the voltage of each side changes.
* Dispersion Retainability: Dispersion indicates the condition of a material when it is physically evenly dispersed by a solvent. Dispersion retainability is the ability to retain the dispersion for a comparatively longer time.
* Surface Reactivity: Surface reaction is caused by physicochemical clashes of materials when a material moves to arbitrary directions in a solvent. It is proportional to the surface area of the material, and closely intertwined with the degree of dispersion.
The advantage of the resonance sensors is that they are able to detect materials at very low concentrations. However, as the sensors respond to the change of mass, they respond even when unwanted materials cling to the surface of the sensors. To remedy the shortcomings, reduced graphene oxide (RGO), which specifically combines with the material and is similar in size to one-dimensional materials, was also used instead of the sole use of ZnO NWs. With RGO, it became possible to detect ZnO NWs selectively, enabling convenient detection.
The research suggests that one-dimensional nanotoxicity can be detected via a micro-cantilever. Also the research is significant because it established the original technology of detecting one-dimensional nonotoxicity.
* Functionalize: To stick a material on the surface of another material chemically, or to change the condition of a material by physically changing the temperature or roughness of the surfaces of the material.