The efficiency of catalyzing the oxygen reduction reaction (ORR) - the process that breaks the bonds of oxygen molecules - to a large degree determines the electrochemical performance of fuel cells. Platinum and platinum-based composites have long been considered as the most efficient ORR catalysts. In their search for practically viable non-precious metal ORR catalysts, researchers have also been investigating vertically-aligned nitrogen-containing carbon nanotubes. Having a strong electron-withdrawing ability, poly(diallyldimethylammonium chloride) (PDDA) was used to create net positive charge for carbon atoms in the nanotube carbon plane via intermolecular charge transfer. The resultant PDDA functionalized/adsorbed carbon nanotubes were demonstrated to act as metal-free catalysts for oxygen reduction reaction in fuel cells with similar performance as platinum catalysts.
Owing to their large surface area, strong infrared photoluminescence and magnetic properties, nanodiamonds are promising for various biomedical applications, including as drug/gene carriers and alternatives to the current bio-imaging platforms. However, the biomedical applications will hardly be realized unless the potential hazards of nanodiamonds to humans and other biological systems are ascertained. The biocompatibility of nanodiamonds at the cellular level has been confirmed by many independent studies. Following these earlier cytotoxicity studies, many groups have used nanodiamonds and their functionalized derivatives for drug/gene deliveries. In spite of the earlier reports that nanodiamonds are biocompatible at the cellular level, researchers have now demonstrated in a new study that nanodiamonds can activate DNA repair proteins in embryonic stem cells, suggesting possible DNA damages.
There is an increasing interest in flexible solar cells and researchers have been investigating weavable fiber solar cells based on metal wires, glass fibers, or polymer fibers. Unfortunately, the low efficiencies of these fiber-based solar cells greatly limit their promising applications. In order to improve these efficiencies, scientists are exploring various nanomaterials to improve charge separation and transport in these fiber-based photovoltaic devices. One recent promising result has been demonstrated by a research team in China who have developed a novel solar cell from flexible, light-weight, ultrastrong, and semiconductive carbon nanotube fiber. The high alignment of building nanotubes in the fiber allows charges to separate and transport along the fibers efficiently, which provides a fiber solar cell with high performance.
Imagine intelligent medical implants that can continuously monitor their condition inside the body and autonomously respond to changes such as infection by releasing anti-inflammatory agents. Thanks to nanotechnology, medical research is moving quickly towards this goal. A new study shows that the use of polypyrrole films as electrically controlled drug release devices on implant surfaces can potentially improve bone implants. By electrodepositing antibiotics or anti-inflammatory drugs in a polymer coating on medical devices, researchers demonstrate that such drugs can be released from polypyrrole on demand - by applying a voltage - and control cellular behavior important for orthopedic applications, i.e. inhibit inflammation and kill bacteria.
Ranging from electronic gadgets to medical applications, many nanomaterial-based devices have appeared in the market. One of the most important issues for these devices is their reliability and life-time of operation. A vital factor behind these issues is the structural stability of the nano-device - debonding of the nanomaterial from the substrate material being the single largest contribution for device degradation. In order to improve bonding between nanomaterials and their substrate, it is essential to understand and quantify the bonding mechanisms. A new nano-scratch technique developed by researchers in the U.S. could serve as the basis for a reliable quantification technique for interpreting nanomaterial-substrate bond strength.
The toxicity issues surrounding carbon nanotubes (CNTs) are highly relevant for two reasons: Firstly, as more and more products containing CNTs come to market, there is a chance that free CNTs get released during their life cycles, most likely during production or disposal, and find their way through the environment into the body. Secondly, and much more pertinent with regard to potential health risks, is the use of CNTs in biological and medical settings. Some groups are using CNTs in research for vaccination as well as gene and cancer therapy. Here, the CNT applications are designed to interact directly with the immune system. Understanding the interplay between CNTs and immune proteins is therefore critical for both improving CNT applications in biology and medicine and avoiding potentially noxious immune responses.
With the advance of nanomedicine, bio-nanotechnology, and molecular biology, researchers require tools that allow them to work on a single cell level. These tools are required to probe individual cells, monitor their processes, and control/alter their functions through nanosurgery procedures and injection of drugs, DNA etc. - all without damaging the cells, of course. Researchers have now developed a multifunctional endoscope-like device, using individual CNTs for prolonged intracellular probing at the single-organelle level, without any recordable disturbance to the metabolism of the cell. These endoscopes can transport attoliter volumes of fluid, record picoampere signals from cells, and can be manipulated magnetically. Furthermore, the tip deflects with submicrometer resolution, and the attachment of gold nanoparticles allows intracellular fingerprinting using surface-enhanced Raman spectroscopy (SERS).
Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. One advantage that carbon nanotubes offer for gas sensors, compared to metal oxide materials, is their fast response time and the fact that they react with gases at lower temperatures, sometimes even as low as room temperature. In order for CNT-based sensors to be able to compete with state-of-the-art CMOS technology, researchers need to develop a low cost, reliable and large-scale reproducible CNT deposition process on the wafer level. Researchers in the UK have now presented a novel concept of wafer level localized growth of 'spaghetti'-like CNTs on a fully processed CMOS substrate. This is the first successful proof of concept for growing CNTs at the post CMOS wafer stage.