Front. Phys., 2014, 9(5): 652–664 DOI 10.1007/s11467-014-0418-0 REVIEW ARTICLE Development of new classes of plasmon active nano-structures and their application in bio-sensing and energy guiding Ondrej Stranik, Jacqueline Jatschka, Andrea Cs´ aki, Wolfgang Fritzsche † Leibniz Institute of Photonic Technology, Jena 07745, Germany Corresponding author. E-mail: † wolfgang.fritzsche@ipht-jena.de Received September 3, 2013; accepted February 7, 2014 Metal nanostructures exhibit special optical resonance modes originating from the subwavelength confinement of conductive electrons in the material. These resonance modes represent a strong research focus due to their application potential in optics and sensing application. In this short review recent achievements of our group in this field are highlighted. A wet-chemistry approach synthesis of advanced metallic nanostructures will be introduced and their exact positioning and manipulation by electric field is shown. Next, the application of these nanostructures for a detection of small molecules will be described in several examples. Also, it will be shown that metal nanostructures can be used for sub-wavelength light focusing and for efficient energy coupling into polymer chains. Keywords plasmonics, sensing, nanostructures fabrication, energy guiding PACS numbers 42.25.Fx, 42.79.-e, 78.20.-e Contents 1 Introduction 652 2 Results and discussion 654 2.1 Synthesis of nanostructures 654 2.1.1 Advanced core-shell nanoparticles 654 2.1.2 Nanoparticle flow synthesis 654 2.2 Nanostructures manipulation 655 2.3 Application of nanostructures in bio-sensing 657 2.3.1 Sensing with Localized Surface Plasmon Resonance 657 2.3.2 Electric detection of small molecules by nanoparticles 659 2.4 Controlled energy guiding with nanostructures 659 3 Summary 661 Acknowledgements 661 References and notes 661 1 Introduction The specific optical properties of metals are determined by their loosely bound conductive electrons, which can be appointed as free electron gas in the material. Their large mobility and their plasma frequency lying at the ultraviolet range cause that visible light does not pene- trate into the metal and is mostly reflected [1]. However, when the electrons are spatially confined into small vol- umes by creation of metallic nanostructures or interfaces then a coupled resonance state of light with collective oscillations of electrons, called surface plasmon polari- ton resonances (SPR), can be created at the surfaces of these metallic objects [2, 3]. The research field investi- gating these resonances is called Plasmonics. In general, plasmonics deals with generation, propagation and de- tection of these plasmon oscillations [4, 5]. These plasmon resonances were already observed in a large variety of metallic structures and new scientific ar- ticles describing other systems with specific properties are being constantly published. An overview diagram of the different geometries supporting SPR is given in Fig. 1. The shapes are ordered according to its complexity in form of a triangle, where the tips represent the basic SPR modes in zero, one and two dimension. A representative of zero dimension is a sub-wavelength metal nanoparti- cle. Such particle supports localized surface plasmon res- onances [6], where the dipole mode is the most promi- nent. These resonances can be easily excited by direct illumination of the particles and their existence is con- firmed by absorption or scattering measurement. In two dimensions a plane gold surface supports propagating surface plasmon modes [7]. These modes produce oscil- lating charges on the surface with evanescent light expo- c  Higher Education Press and Springer-Verlag Berlin Heidelberg 2014