Quantum cluster

A different approach was taken by Hao and Cooper (1994), who used a combination of the him linear muffin-tin orbital (LMTO) method and an ab initio molecular quantum cluster method, to investigate S02 adsorption on a Cu monolayer supported by 7—AI2O3. Emphasis here was on the geometry of adsorption sites, with the conclusion that the preferred adsorption site is the Al—Al bridging one. 

Muhammed MAH, Pradeep T (2010) Luminescent quantum clusters of gold as bio-labels. In Demchenko AP (ed) Advanced Fluorescence Reporters in Chemistry and Biology II. Springer Ser Fluoresc 9 333-353... 

The materials described in this chapter are denoted in the literature mostly as metal clusters or metal nanoclusters . However, the terminology metal clusters spans various scientific disciplines and has consequently multiple meanings, including plasmonic nanoparticles and various nanosized metallic structures. Therefore alternative names have been given, although they are at the moment supported only by a fraction of the scientific community quantum clusters [26], nanodots [27], metal quantum dots [25] and superatoms [28]. 

Abstract Quantum clusters of gold are materials with a core dimension in the subnanometer regime. They exhibit a totally different chemistry when compared with the metallic nanoparticles. In this chapter, we present this new family of materials. Various approaches used for the synthesis of both water and organic soluble clusters are described. After reviewing the various properties of these clusters with special reference to their luminescent properties, we look at their bio-labeling applications. We hope that this chapter initiates the reader into a new family of materials in the context of luminescence imaging and other purposes. 

Keywords Biolabeling Gold Luminescence Quantum clusters... 

Formation of Quantum Clusters Inside the Cavities of Biologically Relevant... 

Synthesis of Quantum Clusters by the Core Etching or Core... 

The quantized nature of electronic energy levels due to size confinement is amplified in this term. They show characteristic absorption features and can be distinguished from each other from their absorption profiles [2], Quantum clusters typically exhibit strong photoluminescence and their wavelength of emission can be tuned from the near infra red (NIR) to ultra violet (UV) [1]. 

Quantum clusters of gold can be synthesized in different ways. All the synthetic methods reported so far can be broadly classified into four categories. 

Two phase reduction (Brust synthesis) This method is usually employed to make organic soluble quantum clusters [8]. This method consists of two steps. The first is the transfer of AuCLi from aqueous to the organic layer by a phase transfer reagent such as tetraoctyl ammonium bromide (TOABr). The next step is the subsequent reduction of AuCU in the presence of suitably selected ligands such as thiols, phosphines, etc. 

A group of water-soluble glutathione-protected clusters with defined chemical compositions have been synthesized by reducing Au3+ ions in the presence of glutathione. This produces a mixture of quantum clusters that are the kinetically... 

In this method, a metallic nanoparticle is synthesized first. The metallic nanoparticles are then treated with large amounts of suitably selected molecules, resulting in the formation of quantum clusters. 

Quantum clusters are highly photostable when compared with organic fluorophores. A study was conducted to check the photostability of clusters in comparison to organic fluorophores and semiconductor quantum dots [12]. Photostability of a gold cluster capped with dihydrolipoic acid (AuNC DHLA) was compared with polymer coated CdSe/ZnS semiconductor quantum dots and two different organic fluorophores namely fluorescein and rhodamine 6G (Fig. 5). For the study, 20 pi of fluorescent AuNC DHLA was dissolved in sodium borate buffer of pH 9. The sample was loaded into a quartz cuvette and was exposed to blue-light (480 nm)... 

Habeeb Muhammed MA, Ramesh S, Sinha SS et al (2008) Two distinct fluorescent quantum clusters of gold starting from metallic nanoparticles by pH-dependent ligand etching. Nano Res 1 333-340... 

Habeeb Muhammed MA, Shaw AK, Pal SK et al (2008) Quantum clusters of gold exhibiting FRET. J Phys Chem C 112 14324-14330... 

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