Plasmonic nanoparticle synthesis and bioconjugation for bioanalytical sensing

Plasmonic nanoparticles, e.g. nanoscale particles consisting of noble metals, show high potential as transducer elements in novel optical sensors. Their optical properties are based on collective and coherent oscillation of the conduction electrons by irradiating electromagnetic waves. The resulting resonance band (localized surface plasmon resonance [LSPR]) is adjustable in the UV‐ to near‐infrared spectral range and can be defined by the chemical synthesis. The synthesis conditions can determine dimension, material and particle shape, and these parameters represent the main factors for the position of the LSPR and the bulk sensitivity. Therefore, a reproducible synthesis of nanoparticles with defined LSPR is of importance. The sensing principle is based on the strong influence of the surrounding medium's refractive index. Especially, anisotropically shaped particles are especially sensitive to small changes in the medium; therefore, their defined synthesis is in the focus of current developments. In this review, we give an overview of the different synthesis techniques for nanoparticles, including miniaturized fluid devices. For sensoric applications, the conjugation of nanoparticles with biomolecules represents a key step; thus, typical functionalization approaches are considered. In the following sections, different LSPR sensing strategies are introduced, and possible applications, especially in DNA analytics, are demonstrated.