Editorial [Hot topic: Fiber Optic Chemical and Biological Sensors: Perspectives and Challenges Approaching the Nano-Era (Guest Editor: Andrea Cusano, Antonello Cutolo and Michele Giordano)]

Fiber optic sensors emerged from the low loss fiber optic technology developed in the 70's and incredibly increased their growth in both research and applications over the last two decades. Cost effectiveness of fiber optic sensors comes out from the rapid developments in telecommunications optics, cost reduction in laser diodes and optical fibers. Actually primary fiber optic sensors markets are oil wells, security, smart structures and seismic detection in oil industry with a market grew of about 90% in 2005 achieving revenue of about 130 million $. Today, market opportunities for sensors are developing and expanding due to the increase of environmental global modifications, homeland security needs and elderly population. Fiber optic based technology can respond to these needs due to the inherent networking efficiency, the optimal cost/performance ratio and the demonstrated ease of integration of optical fibers with sensitive materials for physical, chemical and biochemical sensors. A wide choice of discrete and distributed fiber optic sensors are commercial available based on well assessed optical transduction schemes such as Fabry Perot cavities and Fiber Bragg Gratings or Raman and Brillouin scattering techniques that cover most of the relevant applications in physical sensing (temperature, strain, stress, vibration). Moreover applications in chemical, biological, environmental and medical fields requires a new generation of devices which principle of operation relies on the sensing functions added by specific designed coating materials. In fact fiber optic sensing technology still continues to be the subject of significant basic research effort not only investigating novel phenomena that can be utilized in sensing but also addressing the integration of novel materials and nano/micro technology in the optical sensor design. In particular, the ongoing interest is stimulated by an ever increasing portfolio of technologies through which light may be caused to interact with chemical or biological conditions which surround it and, in recent years, materials nano/micro technology has provided new opportunities for chemical and biological applications. This issue will contribute toward encapsulating recent exciting developments in the integration of new transduction mechanisms and novel materials whilst in parallel covering the continually expanding world of field trials and application assessments, with special attention to explore new perspectives and outline technological challenges. A novel generation of fiber optic devices for chemical and biological sensing is approaching based on the concurrent addressing of the issues related to the different aspects of their global design, such as: dielectric properties definition and optical modeling, materials identification, functionalization and activation, novel optical transduction principle development. Up to now, great effort has been carried out by the scientific community to develop photonic devices, however, the weak integration of competencies required to address this challenge, intrinsically multidisciplinary, limits the capability to achieve high performances devices. A highly integrated approach involving continuous interactions of different backgrounds aimed to optimize each single aspect with a continuous feed-back, would enable the definition of an overall and global design concept. This special issue presents relevant developments in the field of fiber optic chemical and biological nano/micro sensors starting from a last five years review presented in chapter 1 including gas optodes (oxygen, hydrogen, carbon dioxide and ammonia), humidity sensors, monitors for pH, cations and anions, sensors for organic compounds. Also, biosensors based on enzymes, antibodies, nucleic acids and whole microorganisms are described to illustrate the state-of-the-art in this active area. Chapter 2 illustrates advanced interdisciplinary approaches to in-fibre chemical sensing where nano structured materials (nanocristalline polymers, carbon nanotubes and microstructured metallic oxides) and innovative optical transducers schemes (near field optical transducers, photonic bandgap fibers and nano-coated long period gratings) are concurrently developed. Addressing molecular recognition through the mimic of biological receptors is the theme of chapter 3 where the development of optical biosensors based on molecularly imprinted polymers is reviewed and recent innovations presented with special emphasis on their analytical applications.......