Nanowire Decoration with Organic Compounds: Tuning Sensor Sensitivity and Specificity
Dr. De Smet is an Assistant Professor at the Department of Chemical Engineering of Delft University of Technology, The Netherlands. Together with three group members he wrote a review chapter titled Organic Surface Modification of Silicon Nanowire-Based Sensor Devices, for one of InTech’s latest books, Nanowires-Implementations and Applications.
InTech: What is the subject of your chapter?
Our chapter is on the decoration of nanowire-based sensors with organic molecules. Nanowires are a strong candidate for achieving the next generation of sensors. Electrical sensors based on nanowires exhibit enhanced sensitivity compared with regular planar sensor platforms, originating from the advantageous surface-to-volume ratio of nanowires. Moreover, their 1-D character offers the possibility to detect single-molecule events. Typical dimensions of such wires are 50 nm * 50 nm * 1 micrometer (width * height * length). They can be prepared from different materials, including silicon. Thin layers of organic molecules can be chemically bound onto the nanowire surface allowing the integration of so-called receptors. Receptors are chemical compounds that can have a very specific affinity with target compounds. So, the modification of nanowire surfaces ensures the selectivity to a broad range of target species, including DNA, protons and antibodies, and metal ions. Upon the binding of target compounds to the receptors the conductance through the nanowire changes. This change is a measure for the amount of bound target compounds.
InTech: What audience are you targeting?
Research has become more interdisciplinary over the past decades. Nanosensor research is a good example of this. Engineering is needed for the fabrication of the devices. Biology delivers the receptor molecules, which are put on the device interfaces via chemistry. Finally, electrical engineering and physics is needed for the device characterization and for obtaining more knowledge on the sensing mechanism. It is important that nanosensor project members from different background communicate smoothly. This chapter gives an overview of the different methods that have been reported on covering nanowire-based sensors with organic molecules and receptors. The chapter will be most valuable for nanosensors researchers with limited background in chemistry.
InTech: What do you hope to achieve in the long run with your work?
New ways of surface modification methods will not only open doors using different, new types of receptors that have a biological or medical relevance, but it will also allow the chemical tuning of multi-array sensors. This type of sensors has a collection of nanowires on one sensor device, which could be covered with different receptors on the different nanowires. Such a sensor will enable sensitive sensing of different target compounds, e.g. viruses or bacteria, in one go. We aim to contribute to control the surface chemistry of individual nanowires in an array of nanowires. This will stimulate the fabrication of sensors that are suitable for multiple-target detection.
InTech: What are the implications your work has for science and society?
The year 2011 marks the 10th anniversary of nanowire-based sensors that are made of silicon. They form a special class of sensors. Although an increasing number of studies show the potential of these sensors, to date the number of applications is limited. As soon as we have a higher control of the surface chemistry of the nanowires, it will be possible to apply the sensors in medical, agro-food and environmental areas. Given the high sensitivity of nanowire-based sensors, they will circumvent time-consuming cell cultures or other labor-intensive amplification techniques that are currently often required for diagnosis.
InTech: Why did you decide to publish an Open Access paper?
The reason for going Open Access is a mixture of the widely known and discussed ethical reasons that support Open Access, including the importance of access to knowledge and information to higher education and research and the fact that a large portion of our research is publicly funded. Obviously, there is also an extremely strong practical reason: open access work is more widely read and ensures a greater visibility.
Like many universities, also Delft University of Technology supports the global distribution of knowledge through Open Access publishing. The Open Access fee of our chapter has been paid by the Incentive Fund Open Access of the Netherlands Organization for Scientific Research (NWO). NWO is an independent administrative body under the auspices of the Dutch Ministry of Education, Culture and Science and is the largest financer of scientific innovation in the Netherlands.
InTech: In your opinion, how inclined are researchers in the Netherlands towards the Open Access publishing model?
I notice that in the Netherlands Open Access is mainly an issue for publishers, managers, librarians and financiers – not too much for scientists at the moment, but I guess this also holds for other countries. When deciding where to submit a manuscript it is all about journal scope, journal quality and impact factor. Apart from entirely (and relatively new) Open Access journals, there is also in increasing number of more established journals that offer the option of ‘Author-Choice Open Access’. Although some scientists have the feeling that a paper presently is paid twice this way I believe that an increasing number of Dutch researchers make use of this option. This system will work as long as special Open Access funds are available, like those of NWO and some Dutch universities, including Delft University of Technology. However, the real test will come in the next few years: what will happen when these funds are dried up? I am not sure whether researchers are willing to pay Open Access fees – which could be as high as a few thousand Euros per publication – from research budgets.
InTech: Are researchers acquainted with the benefits of Open Access?
Also in the Netherlands Open Access has become a heavily discussed topic. As said, not too many researchers are into it yet, but the number is increasing. There is a lot of attention for Open Access in the Netherlands. Early in 2011, the Royal Netherlands Academy of Arts and Sciences adopted a policy on Open Access and Digital Preservation for its research organization. The Academy requests its researchers to publish publications Open Access as far as possible. At about the same time, presented their global perspective on Open Access. Basically, it is hardly impossible to stay away from the debate on Open Access. Along the way, more and more researchers are being exposed to the related benefits.
Interview by: Katarina Lovrečić
About Dr. De Smet
Dr. De Smet received the MSc degree (2001) in Molecular Sciences and the PhDdegree(2006) in the field of organic monolayers from Wageningen University, The Netherlands. He then worked as a Postdoctoral Researcher on plasma polymers at the Ian Wark Research Institute, University of South Australia, Australia. In 2007 he was appointed as an Assistant Professor at the Department of Chemical Engineering at the Technological University of Delft, The Netherlands. His research activities include the preparation and characterization of functional organic monolayers and polymer films and their application to the surface of different sensor platforms, including nanowire-based sensors and interdigitated electrodes. His group collaborates with different companies that work on the device design and fabrication (Philips Research and Nanosens) and different partners that work on molecular receptors (Royal Tropical Institute, Erasmus University and Plant Research International from Wageningen University). He is (co)author of 19 peer-reviewed journal papers he is co-inventor of two issued patents. Dr. De Smet was awarded a Talent Stipend (2006) and a Veni grant (Innovational Research Incentives Scheme, 2007) from the Netherlands Organization for Scientific Research (NWO).