Coordination Chemistry Reviews 253 (2009) 1607–1618 Contents lists available at ScienceDirect Coordination Chemistry Reviews journal homepage: www.elsevier.com/locate/ccr Review Gold nanoparticle probes Zhenxin Wang ∗ , Lina Ma State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022, China Contents 1. Introduction ........................................................................................................................................ 1607 2. Synthesis, stabilization and functionalization of gold nanoparticle probes ....................................................................... 1608 2.1. Synthesis .................................................................................................................................... 1608 2.2. Stabilization and functionalization ......................................................................................................... 1608 3. Applications of gold nanoparticle probes .......................................................................................................... 1609 3.1. Heavy metal cations determination ........................................................................................................ 1609 3.2. DNA detection .............................................................................................................................. 1612 3.3. Protein analysis ............................................................................................................................. 1613 3.4. Enzymatic activity assay .................................................................................................................... 1615 3.5. Cellular analysis ............................................................................................................................. 1616 4. Conclusion and outlook ............................................................................................................................ 1616 Acknowledgements ................................................................................................................................ 1616 References .......................................................................................................................................... 1616 article info Article history: Received 27 October 2008 Accepted 7 January 2009 Available online 15 January 2009 Keywords: Gold nanoparticles Synthesis Application Probes Chemical sensing and imaging abstract Depending on their size, shape, degree of aggregation and nature of the protecting organic shells on their surface, gold nanoparticles (AuNPs) can appear red, blue and other colors and emit bright resonance light scattering of various wavelengths. Because of this unique optical property, AuNPs have been extensively explored as probes for sensing/imaging a wide range of analytes/targets, such as heavy metallic cations, nucleic acids, proteins, cells, etc. Since their initial discovery, novel synthetic methods have led to precise control over particle size, shape and stability, thus allowing the modification of a wide variety of ligands on the AuNP surfaces to meet different experimental conditions. This review discusses the synthesis and applications of functionalized AuNPs in chemical sensing and imaging. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The combination of nanotechnology with chemistry, biology, physics, and medicine for the development of ultrasensitive detec- tion and imaging methods in the analytical or biological sciences is becoming increasingly important in modern science [1–14]. Par- ticularly attractive is the use of functional AuNPs in biological and pharmaceutical field, such as the ultrasensitive detection and imaging methods for bioreorganizing events, because AuNPs have unique optical properties (i.e. surface plasma resonance absorption and resonance light scattering), a variety of surface coatings and great biocompatibility [5–7,11–18]. ∗ Corresponding author. Fax: +86 431 5262243. E-mail address: wangzx@ciac.jl.cn (Z. Wang). Generally, the optical properties of small metal nanoparticles are dominated by collective oscillation of electrons at surfaces (known as “surface plasmon resonance”, SPR or “localized surface plasmon resonance”, LSPR) that are in resonance with the inci- dent electromagnetic radiation [4–6,13,19]. For gold, it happens that the resonance frequency of this oscillation, governed by its bulk dielectric constant, lies in the visible region of the electro- magnetic spectrum [19]. Because nanoparticles have a high surface area to volume ratio, the plasmon frequency is exquisitely sensi- tive to the dielectric (refractive index) nature of its interface with the local medium. Any changes to the environment of these par- ticles (surface modification, aggregation, medium refractive index, etc.) leads to colorimetric changes of the dispersions [5,8,20–25]. Due to coupling of the plasmons, assemblies (or aggregations) of AuNPs are often accompanied by distinct color changes. Colori- metric sensors using AuNPs have been widely explored and have important applications [6,8,14]. Not only is light strongly absorbed 0010-8545/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ccr.2009.01.005