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Luminescent quantum dots (QDs) of I-III-VI.sub.2 semiconductors present a new class of luminescence materials that combine unique optical and electronic properties while exhibiting low toxicity compared to conventional cadmium-based QDs. Advances in the colloidal synthesis of ternary QDs have been used to develop fluorescence chemical and biological sensors for the detection of various analytes. The review covers the main approaches to synthesizing QDs of the I-III-VI.sub.2 structure, the features of their structure and properties, and current trends in their use as low-toxic luminescent labels in biomedicine and chemical analysis., Author(s): T. S. Ponomaryova [sup.1], A. S. Novikova [sup.1], A. M. Abramova [sup.1], O. A. Goryacheva [sup.1], D. D. Drozd [sup.1], P. D. Strokin [sup.1], I. Yu. Goryacheva [sup.1] Author [...]

Multilayer graphene shell encapsulated gold nanoparticle--quantum dot hybrids were derived by combining wetchemical, thermal, and covalent chemistry approaches. Uniformly patterned gold nanoparticles on a silicon substrate were obtained via gold film deposition in an electroless method followed by a thermal dewetting process. The resulting gold nanoparticles were further surface oxidized and utilized as catalysts for the chemical vapor deposition growth of multilayer graphene shell encapsulated on the gold nanoparticles (referred as 'multilayer graphene shell encapsulated Au nanoparticle' or graphene nanoparticles (GNPs)). As a next step, the surface of GNPs was modified to result in carboxylic (-COOH) functionalities, which enabled carbodiimide-based covalent linking of amine-terminated Cd[S.sub.x][Se.sub.1-x]@ZnS quantum dots (QDs) on the GNP surface. The GNPs and GNP-QD heterostructures were characterized using scanning and transmission electron microscopy for size, morphology, spatial distribution, and crystal structure evaluation. In addition, UV-vis, fluorescence spectroscopy, and discrete dipole approximation (DDA) modeling were utilized for understanding the band gap energies, fluorescence quenching, and light-matter interactions of the derived hybrids/heterostructures. Keywords Graphene * Gold nanoparticles * Quantum dots * Optical properties, discrete dipole approximation, Introduction The surface modification of photonic nanostructures such as gold (Au) nanoparticles can lead to novel physical phenomena including selective light-matter interactions and rapid energy transfer processes [1-3]. The surface [...]

The development of analytical platforms incorporating Au nanoparticles (NPs) for optical biosensing requires approaches to produce optically responsive and target selective materials. In the present work, fluorescence emission and bioselectivity of Au NPs have been combined by a one-step surface functionalization using fluorescein isothiocyanate (FITC) and biotin. First, colloidal Au NPs (d =17.7 ± 2.7 nm) exhibiting an absorption maximum ([λ.sub.max]) at 524.5 nm have been surface-modified with the polyelectrolytes (PE) poly(allylamine hydrochloride) (PAH) and poly(sodium styrene sulfonate) (PSS). Two strategies were then assessed for the functionalization of Au NPs: (i) functionalization of PAH with biotin and subsequent coating of the NPs and (ii) surface modification of the NPs with the PE followed by postfunctionalization with biotin. The effect of the surface functionalization on the colloidal NPs was monitored by optical absorption and fluorescence emission spectroscopies, dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM). Finally, the optical response and specificity of the functionalized NPs towards avidin was evaluated by optical measurements. The results have shown that these hybrid nanostructures have potential to be used in biosensing. In particular, the aggregation of biotinylated Au assemblies associated with the biorecognition of avidin could be assessed by fluorescence emission spectroscopy. Keywords Biosensor * Gold nanoparticles * Optical properties * Hybrid nanostructures * Polyelectrolytes * Biotinylation, Introduction Gold nanoparticles (Au NPs) have been widely studied for diverse bioapplications namely due to their optical properties which are dependent on the morphological characteristics and surrounding medium [1-5]. These [...]

1. Introduction The expression 'QD' will be used in this work to describe CdSe/ZnS core/shell semiconductor nanocrystals which can be fabricated to yield specific optical properties [1]. An excellent review [...]