Organic Fluorescent Nanofibers and Sub-micrometer Rods

Luminescent nanofibers are a particular class of nanofibers. Like the other members of this family, they are very small objects whose typical diameters range between 50 to 500 nm (it is noteworthy that beyond these values, the term of microfibers is more appropriate) and lengths can reach several hundred micrometers. Besides, they display special photophysical behavior. By definition, fluorescent nanofibers have the property to emit light after absorption of UV or visible radiations, and electroluminescent nanofibers emit light upon electrical excitation. Passive properties are also encountered. This is the case in particular for waveguiding, light being guided along the long axis when the fiber width is above a minimum critical value. It is thus easy to understand why these fibers are presently attracting increasing attention. One of the most promising applications is their use in nanotechnologies. This field has developed tremendously during the last few years and submicrometer organic materials that exhibit specific optical properties are now of high demand. Among them, luminescent nanofibers occupy a very special position, because their morphology makes then unique for use in miniaturized systems, especially photonic devices, where they can be incorporated individually and act as active component to generate or transmit light from one point to another (Schiek et al., 2008). Their use has been proposed as frequency doublers (Brewer et al., 2006) and nanolasers (Quochi et al., 2006). They are also prime candidates for applications in the fields of photovoltaic cells and organic light-emitting diodes (OLEDs) for color displays or white light illumination (Ner et al., 2008; Ner et al., 2009). Other original uses can be found. For example, some fluorescent nanofibers have been shown to act as chemosensors to detect traces of amine vapor (Che et al., 2008; Che & Zang, 2009), explosives (Long et al., 2009; Naddo et al., 2007; Naddo et al., 2008; Tao et al., 2007; Wang et al., 2001; Wang et al., 2002; Zang et al., 2009) and metal ions (Wang et al., 2001; Wang, Drew et al., 2002). As biosensors, nanofibers reveal the presence of pathogen bacteria (Memisevic et al., 2009) and proteases (Law et al., 2007), and could be used for diagnostic purpose. Generally, the sensing performance is improved by the extended effective surface area of the nanofibers. These structures could also play the role of antennae in light-harvesting nanomaterials (Channon et al., 2009; Channon et al., 2009; Source: Nanofibers, Book edited by: Ashok Kumar, ISBN 978-953-7619-86-2, pp. 438, February 2010, INTECH, Croatia, downloaded from SCIYO.COM