Colloidal quantum dots: the opportunities and the pitfalls for DNA analysis applications

Colloidal quantum dots (QDs) have received considerable attention as luminescent probes for DNA analysis applications. The underlying photophysical and photochemical properties of these probes need consideration when designing assays for DNA analysis. These properties include intermittent fluorescence often termed 'blinking', photobleaching, photoinduced fluorescence enhancement and, as a result of recent evidence, photo-induced generation of reactive oxygen species leading to DNA damage. Even though the design of assays for DNA analysis using QDs needs care, QDs do provide advantages over fluorophores for many emerging DNA analysis methods where low copy numbers of DNA are present. Many of the more traditional DNA assay methods using fluorophore labeled probes either cannot be translated, or show no benefit in using QDs as the lumophore

Direct detection of DNA on gold structured planar substrates by Raman microscopy

Detection of DNA sequences is pivotal to many modern molecular diagnostic methods, but the ability to directly detect DNA sequences, without the need for signal amplification (such as by applying a polymerase chain reactions) is highly desirable. Here we investigate the potential for gold inverted pyramidal structures (also known as Klarite®) for DNA detection, as these simple chips containing the structured surface on a face could offer an improved format for DNA based diagnostic methods. Our strategy included optimization of the fabrication protocols to achieve flat gold surfaces within the inverted pyramidal surface and then a subsequent assessment of these substrates for direct DNA detection by Raman microscopy. These studies demonstrate for the first time the potential of these gold structured planar substrates for DNA analysis applications

A nanoporous gold membrane for sensing applications

Design and fabrication of three-dimensionally structured, gold membranes containing hexagonally close-packed microcavities with nanopores in the base, are described. Our aim is to create a nanoporous structure with localized enhancement of the fluorescence or Raman scattering at, and in the nanopore when excited with light of approximately 600 nm, with a view to provide sensitive detection of biomolecules. A range of geometries of the nanopore integrated into hexagonally close-packed assemblies of gold micro-cavities was first evaluated theoretically. The optimal size and shape of the nanopore in a single microcavity were then considered to provide the highest localized plasmon enhancement (of fluorescence or Raman scattering) at the very center of the nanopore for a bioanalyte traversing through. The optimized design was established to be a 1200 nm diameter cavity of 600 nm depth with a 50 nm square nanopore with rounded corners in the base. A gold 3D-structured membrane containing these sized microcavities with the integrated nanopore was successfully fabricated and ‘proof of concept’ Raman scattering experiments are described

Flash synthesis of CdSe/CdS core-shell quantum Dots

We report on the "flash" synthesis of CdSe/CdS core-shell quantum dots (QDs). This new method, based on a seeded growth approach and using an excess of a carboxylic acid, leads to an isotropic and epitaxial growth of a CdS shell on a wurtzite CdSe core. The method is particularly fast and efficient, allowing the controllable growth of very thick CdS shells (up to 6.7 nm in the present study) in no more than 3 min, which is considerably shorter than in previously reported methods. The prepared materials present state-of-the-art properties with narrow emission and high photoluminescence quantum yields, even for thick CdS shells. Additionally, Raman analyses point to an alloyed interface between the core and the shell, which, in conjunction with the thickness of the CdS shell, results in the observed considerable reduction of the blinking rate. © 2013 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe