Guest Editorial: Introduction to the JSTQE Issue on Semiconductor Nanocrystal Optoelectronics

[No abstract available

Identification of Molecular Fluorophore as a Component of Carbon Dots able to Induce Gelation in a Fluorescent Multivalent-Metal-Ion-Free Alginate Hydrogel

We introduce a simple approach to fabricate fluorescent multivalent metal ion-free alginate hydrogels, which can be produced using carbon dots accessible from natural sources (citric acid and L-cysteine). Molecular fluorophore 5-oxo-2,3-dihydro-5H-[1,3]-thiazolo[3,2-a] pyridine-3,7-dicarboxylic acid (TPDCA), which is formed during the synthesis of carbon dots, is identified as a key segment for the crosslinking of hydrogels. The crosslinking happens through dynamic complexation of carboxylic acid groups of TPDCA and alginate cages along with sodium ions. The TPDCA derived hydrogels are investigated regarding to their thermal, rheological and optical properties, and found to exhibit characteristic fluorescence of this aggregated molecular fluorophore. Moreover, gradient hydrogels with tunable mechanical and optical properties and controlled release are obtained upon immersion of the hydrogel reactors in solutions of divalent metal ions (Ca2+, Cu2+, and Ni2+) with a higher affinity to alginate. - 2019, The Author(s).This contribution was made possible by the NPRP award [8–878–1–172] from Qatar National Research Fund (a member of Qatar foundation), Qatar University grant QUCG-CAM-19/20-2 and by a grant from the Germany/ Hong Kong Joint Research Scheme sponsored by the Research Grants Council of Hong Kong and the Germany Academic Exchange Service of Germany (Reference No.: G-CityU103/16). M.D. thanks the VEGA Scientific Grant Agency for support through project no. 2/0158/17.Scopu

Effect of chemical composition on luminescence of thiol-stabilized CdTe nanocrystals

Judicious selection of the amount of surfactant during synthesis enables a drastic increase in the photoluminescence efficiency of aqueous CdTe nanocrystals (NCs) stabilized by thioglycolic acid (TGA). Elemental determination of the NCs was undertaken to identify the origin of this effect. The molar ratio of (Te + S) to Cd approached unity when the optimum amount of TGA was used during synthesis, whereas the number of S atoms originating from TGA molecules in one NC (2.6 nm of diameter) remained unchanged at 90 ± 3. This indicates that the core lattice composition at the beginning of synthesis, rather than the surface conditions, affects the photoluminescence efficiency of the NCs even after prolonged refluxing

Evolution of the electronic structure with size in II-VI semiconductor nanocrystals

In order to provide a quantitatively accurate description of the band gap variation with sizes in various II-VI semiconductor nanocrystals, we make use of the recently reported tight-binding parametrization of the corresponding bulk systems. Using the same tight-binding scheme and parameters, we calculate the electronic structure of II-VI nanocrystals in real space with sizes ranging between 5 and 80 {\AA} in diameter. A comparison with available experimental results from the literature shows an excellent agreement over the entire range of sizes.Comment: 17 pages, 4 figures, accepted in Phys. Rev.

Guided self-assembly of Fe3O4 nanoparticle on chemically active surface templates generated by electro-oxidative nanolithography

An approach for the site-selective binding of magnetic Fe3O4 particles onto predefined surface templates is reported. Chem. active surface patterns are prepd. by electro-oxidative nanolithog. performed with the conductive tip of a scanning probe microscope on n-octadecyltrichlorosilane (OTS) monolayers self-assembled on silicon. The chem. functionalization allows prefabricated nanoparticles with an org. ligand shell to attach selectively on these surface sites, just by immersing the sample into the particle soln. Besides the use of the active surface patterns to guide the assembly of Fe3O4 nanoparticles with nanometer precision, several aspects of the patterning process are briefly discussed in terms of optimization of the obtainable line width. [on SciFinder (R)

Guided self-assembly of Fe3O4 nanoparticle on chemically active surface templates generated by electro-oxidative nanolithography

An approach for the site-selective binding of magnetic Fe3O4 particles onto predefined surface templates is reported. Chem. active surface patterns are prepd. by electro-oxidative nanolithog. performed with the conductive tip of a scanning probe microscope on n-octadecyltrichlorosilane (OTS) monolayers self-assembled on silicon. The chem. functionalization allows prefabricated nanoparticles with an org. ligand shell to attach selectively on these surface sites, just by immersing the sample into the particle soln. Besides the use of the active surface patterns to guide the assembly of Fe3O4 nanoparticles with nanometer precision, several aspects of the patterning process are briefly discussed in terms of optimization of the obtainable line width. [on SciFinder (R)

Energy transfer with semiconductor nanocrystals

Fo¨ rster (or fluorescence) resonant energy transfer (FRET) is a powerful spectroscopic technique to study interactions, conformational and distance changes, in hybrid nanosystems. Semiconductor nanocrystals, also known as colloidal quantum dots, are highly efficient fluorophores with a strong band-gap luminescence tuneable by size as a result of the quantum confinement effect. Starting from a short summary on the FRET formalism and on the basic properties of semiconductor nanocrystals, this Feature Article provides an overview of the major classes of hybrid FRET systems with semiconductor nanocrystals as at least one component. Systems under consideration include thin solid films containing differently sized semiconductor nanocrystals, solution-based complexes of differently sized semiconductor nanocrystals, nanocrystal-based bioconjugates, and hybrid structures of semiconductor and gold nanoparticles. We focus in particular on the directional energy transfer in layer-by-layer assembled multilayers of differently sized CdTe semiconductor nanocrystals and on the energy transfer from individual rod-like semiconductor CdSe/CdS nanoantennae to single dye molecules, which can be efficiently controlled by external electric fields leading to the realisation of the FRET optical switch

Large improvement of electron extraction from CdSe quantum dots into s TiO2 thin layer by N3 dye coabsorption

Large increase of electron extraction from CdSe quantum dots into TiO2 by N3 dye coadsorption , Thin Solid Films 516 2008 6994 699