An efficient method for the surface functionalization of luminescent quantum dots with lipoic acid-based ligands

We describe an operationally advantageous general methodology to efficiently activate lipoic acid-based compounds - a family of popular surface ligands for semiconductor nanocrystals - by the use of a borohydride exchange resin, and the use of the activated species to replace the native surface ligands of quantum dots. The procedure enables the phase transfer of the nanocrystals between polar and aqueous media and, if unsubstituted lipoic acid is used, a facile adjustment of their solubility in a wide range of solvents with varying polarity (from hexane to water). We show that the protocol is applicable to different types of nanocrystals and a variety of lipoic acid-based ligands, and that the resulting quantum dots maintain their optical properties - in particular, an intense luminescence - and long term colloidal stability

Competing surface reactions limiting the performance of ion-sensitive field-effect transistors

© 2015 Elsevier B.V. All rights reserved.Ion-sensitive field-effect transistors based on silicon nanowires are promising candidates for the detection of chemical and biochemical species. These devices have been established as pH sensors thanks to the large number of surface hydroxyl groups at the gate dielectrics which makes them intrinsically sensitive to protons. To specifically detect species other than protons, the sensor surface needs to be modified. However, the remaining hydroxyl groups after functionalization may still limit the sensor response to the targeted species. Here, we describe the influence of competing reactions on the measured response using a general site-binding model. We investigate the key features of the model with a real sensing example based on gold-coated nanoribbons functionalized with a self-assembled monolayer of calcium-sensitive molecules. We identify the residual pH response as the key parameter limiting the sensor response. The competing effect of pH or any other relevant reaction at the sensor surface has therefore to be included to quantitatively understand the sensor response and prevent misleading interpretations

Hole-transport functionalized copper(i) dye sensitized solar cells

Ligands containing first and second generation hole-transport triphenylamino-dendrons have been evaluated as ancillary ligands in copper(i) DSCs yielding an optimal efficiency of 3.77% in unmasked cells. The effects of masking the DSCs on measured parameters are discussed. © 2013 the Owner Societies

Modulation of the solubility of luminescent semiconductor nanocrystals through facile surface functionalization

The solubility of luminescent quantum dots in solvents from hexane to water can be finely tuned by the choice of the countercations associated with carboxylate residues present on the nanocrystal surface. The resulting nanocrystals exhibit long term colloidal and chemical stability and maintain their photophysical properties. This journal is © the Partner Organisations 2014

Improvement of internet portal sites for Mountain villages by the comparison of the sites for rural tourism villages nationwide and overseas [Korean]

This study aims to compare internet portal sites for rural tourism, and to suggest the improved contents for homepage information on mountain villages under the Korea Forest Service. Design, interface, information source, and communication as estimation indicators were used to understand the characteristics of portal sites, and sub-items under indicators to analyse the portal sites were established. Nationwide portal sites were compared for rural tourism information. Also, German and Italian portal sites were compared as overseas cases. As a result, an internet portal site for information on mountain villages under the Korea Forest Service has to be improved as compared with other portal sites related to rural tourism. Firstly, it is necessary to modify and improve the category explaining mountain villages. Secondly, homepage for developing mountain villages has to be established and linked to potential visitors. Thirdly, portal sites for developing mountain villages subsequently have to be constructed under the site of the Korea Forest Service

The Different Faces of 4′-Pyrimidinyl-Functionalized 4,2′:6′,4′′-Terpyridines: Metal–Organic Assemblies from Solution and on Au(111) and Cu(111) Surface Platforms

A comparative investigation of crystal growth from solution and on-surface assembly <i>in vacuo</i> between copper and three 4′-(2-R-pyrimidin-5-yl)-4,2′:6′,4′′-terpyridines, with R = H (<b>1</b>), Me (<b>2</b>), or Et (<b>3</b>), is presented. In solution, ligand <b>3</b> combines with copper­(II) acetate or copper­(I) triflate in MeOH solution to give [Cu₂(OAc)₄(<b>3</b>)]_<i>n</i> or {[Cu­(<b>3</b>)­(OMe)­(MeOH)]­[CF₃SO₃]·MeOH}_<i>n</i>. In [Cu₂(OAc)₄(<b>3</b>)]_<i>n</i>, paddle-wheel {Cu₂(μ-OAc)₄} nodes direct the assembly of one-dimensional (1D) zigzag chains which pack into two-dimensional (2D) sheets. In {[Cu­(<b>3</b>)­(OMe)­(MeOH)]­[CF₃SO₃]·MeOH}_<i>n</i>, the solvent is a ligand and also generates {Cu₂(μ-OMe)₂} units which function as planar 4-connecting nodes to generate a 2D (4,4) net with ligand <b>3</b>. On Au(111) or Cu(111) surfaces <i>in vacuo</i>, no additional solvent or anions are involved in the assembly. The different substituents in <b>1</b>, <b>2</b>, or <b>3</b> allow precise molecular resolution imaging in scanning tunneling microscopy. On Au(111), <b>1</b> and <b>2</b> assemble into close-packed assemblies, while <b>3</b> forms a regular porous network. The deposition of Cu adatoms results in reorganization leading to ladder-shaped surface metal–organic motifs. These on-surface coordination assemblies are independent of the 4′-substituent in the 4,2′:6′,4′′-tpy and are reproduced on Cu(111) where Cu adatoms are available during the deposition and relaxation process at room temperature. Upon annealing at elevated temperatures, the original surface assemblies of <b>1</b> and <b>3</b> are modified and a transition from ladders into rhomboid structures is observed; for <b>2</b>, a further quasi-hexagonal nanoporous network is observed

Selective Sodium Sensing with Gold-Coated Silicon Nanowire Field-Effect Transistors in a Differential Setup

Ion-sensitive field-effect transistors based on silicon nanowires with high dielectric constant gate oxide layers (<i>e.g.</i>, Al₂O₃ or HfO₂) display hydroxyl groups which are known to be sensitive to pH variations but also to other ions present in the electrolyte at high concentration. This intrinsically nonselective sensitivity of the oxide surface greatly complicates the selective sensing of ionic species other than protons. Here, we modify individual nanowires with thin gold films as a novel approach to surface functionalization for the detection of specific analytes. We demonstrate sodium ion (Na⁺) sensing by a self-assembled monolayer (SAM) of thiol-modified crown ethers in a differential measurement setup. A selective Na⁺ response of ≈−44 mV per decade in a NaCl solution is achieved and tested in the presence of protons (H⁺), potassium (K⁺), and chloride (Cl^–) ions, by measuring the difference between a nanowire with a gold surface functionalized by the SAM (active) and a nanowire with a bare gold surface (control). We find that the functional SAM does not affect the unspecific response of gold to pH and background ionic species. This represents a clear advantage of gold compared to oxide surfaces and makes it an ideal candidate for differential measurements