Size-dependent properties Optical

We begin our discussion of nanocrystals in diis chapter widi die most challenging problem faced in die field die preparation and characterization of nanocrystals. These systems present challenging problems for inorganic and analytical chemists alike, and die success of any nanocrystal syndiesis plays a major role in die furdier quantitative study of nanocrystal properties. Next, we will address die unique size-dependent optical properties of bodi metal and semiconductor nanocrystals. Indeed, it is die striking size-dependent colours of nanocrystals diat first attracted... 

An explanation for these size-dependent optical properties, tenned quantum confinement , was first outlined by Bms and co-workers in the early 1980s, [156, 158, 159, 160 and 161] and has fonned the basis for nearly all subsequent discussions of these systems. Though recent work has modified and elaborated on this simple model, its basic predictions are surjDrisingly accurate. The energy of the lowest-lying exciton state is given by the following simple fonnula ... 

Keywords Aggregation-induced enhanced emission (AIEE) Fluorescent organic nanoparticles Ion-association method Organic dye nanoparticles Reprecipitation method Restriction of intramolecular rotation Size-dependent optical properties... 

Metal nanoparticles have extraordinary size-dependent optical properties, not present in the bulk metal and have, consequently, been the subject of intense research during the past decade or so.27 Attention has recently focused on functionalising colloidal nanoparticles with molecular recognition components for potential sensing applications.28,29,30 We have prepared a new amido-disulfide functionalised zinc metalloporphyrin (8) which was self-assembled on to gold nanoparticles to produce a novel anion-selective optical sensing system (9) (Scheme 3).4... 

Kim, C.K., Kallum, R.R., Singh, J.P., Fortner, A., Griffin, J., Darbha, G.K., and Ray, PC. 2006. Gold nanoparticle based miniaturized laser induced fluorescence probe for specific DNA hybridization detection Studies on size dependent optical properties. Nanotechnology, 17 3085-93. 

Semiconductor nanoparticles have been extensively studied in recent years owing to their strongly size-dependent optical properties. Among these nanomaterials, CdS and PbS are particularly attractive due to their nonlinear optical behavior and unusual fluorescence or photoluminescence properties [ 136,137]. A number of studies have been published recently regarding the preparation of CdS, PbS and ZnS nanoparticles in inverse microemulsion systems [138-143]. In these works, NP-5/NP-9 was the most commonly used surfactant and petroleum ether the most commonly used oil. The aqueous phase for each inverse microemulsion consisted of cadmium nitrate (0.1 M) and ammonia sulfide (0.1 M) respectively. CdS was recovered from the mixture of double microemulsions [141]. Electron microscopy revealed that the spherical particles were aroimd 10-20 nm in diameter, as seen in Fig. 14. 

Gold received much attention due to their unique size-dependent optical properties, insolubility in nitric acid and resistance to heat, moisture, oxygen and most corrosive reagents. For substrates in surface-enhanced Raman Spectroscopy (SERS), ergonomic electronic contacts, ultra fast data communication and biomedicine surface modified gold nanoparticles are perspective agents, while in the industry of catalysis platinum nanoparticles (Pt NPs) exhibiting excellent anticorrosive and catalytic properties are usually employed. 

Volkov, V.V., Asahi, T., Masuhara, H., Masuhara, A., Kasai, H., Oikawa, H. and Nakanishi, H. (2004) Size-dependent optical properties of polydiacetylene nanocrystal. J. Phys. Chem. B, 108, 7674-7680. 

Due to their size-dependent optical properties, quantum dots (QDs) have found many applications in biological labeling applications. In these applications. 

The current widespread interest in size-dependent optical properties of nanomaterials is a consequence of their many applications in research areas such as chemosensors, biosensors,nanoparticle optics, and surface-enhanced spectroscopy. Recently, interest in surface-enhanced Raman spectroscopy (SERS)... 

Yu, X.J., Xie, P.B. and Su, Q.D. (2001) Size-dependent optical properties of nanocrystalline Ce02 Er obtained by combustion synthesis. Physical Chemistry Chemical Physics, 3,... 

Moreels I et al (2009) Size-dependent optical properties of colloidal PbS quantum dots. ACS... 

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