Passivation of aluminum with alkyl phosphonic acids for biochip applications

Self-assembly of decylphosphonic acid (DPA) and octadecylphosphonic acid (ODPA) was studied on aluminum films using XPS, ToF-SIMS and surface wettability. Modified aluminum films were tested for passivation against silanization and subsequent oligonucleotide attachment. Passivation ratios of at least 450:1 compared to unprotected aluminum were obtained, as quantified by attachment of radio-labeled oligos.     

含InAs自组装量子点肖特基二极管的关联放电效应

制作了含自组织量子点的金属半导体金属双肖特基势垒器件,研究了器件的电流输运特性.在量子点充放电造成的电流迟滞回路的基础上,观察到了电压扫描过程中的电流由低态到高态的跳跃现象.这种电流跳跃来源于充电量子点的关联放电效应.根据量子点系统的哈密顿量,分析了充电量子点关联放电的原因.这种关联放电效应起源于量子点与2DEG的相互作用,当一个量子点放电时通过量子点和2DEG电流的变化会影响其他的量子点,从而促使其放电,这种过程在整个系统中放大导致所有的量子点放电 关键词： 关联效应 自组装量子点     

Biosensors based on gold nanoelectrode ensembles and screen printed electrodes

Gold nanowires were synthesized within polycarbonate membranes according to an electroless deposition method, obtaining nanoelectrode ensembles (NEEs) with special electrochemical features. NEEs were coupled with home-produced carbon graphite screen printed electrodes and the electrochemical properties of the original nanoelectrode ensemble on screen printed substrate (NEE/SPS) assembly has been tested for sensors application. Glucose oxidase has been used as model enzyme in order to verify the feasibility of disposable gold NEE/SPS biosensors. Finally, different immobilisation and electrochemical deposition techniques based on either self assembled monolayers of cysteamine (CYS) or amino-propyl-triethoxysilane (APTES) and conductive polyaniline (PANI) molecular wires were used. Spatial patterning of the enzyme on the polycarbonate surface and of PANI wires on gold nanoelectrodes was obtained. Possible direct electron transfer between the enzyme and the PANI modified gold nanoelectrodes has been evaluated.     

Self-assembling and phase coexistence of SW trimers as complex amphiphile analogues. I. Simulations

We analyse by discrete molecular dynamics the self-assembly of SW trimer particles that contain a different number of attractive and repulsive spheres. They also have different geometries: linear, obtuse, rectangular and equilateral. We identify that some of these molecules exhibit liquid–vapour equilibria while others do not. For all of them, we show the morphological phase diagram built up from the different supra-molecular structures formed by each type of trimer. We simulated 14 different systems with a total of 321 states. The main features of the supra-molecular structures depend only on the composition and geometry of the trimer: triple SW trimers do not form supra-structures, double SW trimers and single SW trimers form monolayers, bilayers and worm-like micelles. The liquid–vapour coexistence properties are also exhibited. These trimers can be used to model complex amphiphiles beyond the standard ones, such as the Gemini and the Bola surfactants as well as colloidal particles.     

Superconducting and magnetic properties of Nb/Pd 1-xFex/Nb triple layers

The superconducting and magnetic properties of Nb/Pd_1-xFe_x/Nb triple layers with constant Nb layer thickness d_Nb=200 ? and different interlayer thicknesses 3 ?≤ d_PdFe ≤ ? are investigated. The thickness dependence of the magnetization and of the superconducting transition temperature shows that for small iron concentration x the Pd_1-xFe_x layer is likely to be in the paramagnetic state for very thin films whereas ferromagnetic order is established for x ≥ 0.13. The parallel critical field B_c2||(T){B_{c2||}}(T) exhibits a transition from two-dimensional (2D) behavior where the Nb films are coupled across the interlayer, towards a 2D behavior of decoupled Nb films with increasing d_PdFeand/or x. This transition allows a determination of the penetration depth x_F{\xi _F} of Cooper pairs into the Pd_1-xFe_x layer as a function of x. For samples with a ferromagnetic interlayer x_F{\xi _F} is found to be independent of x.     

On the Structure and Formation of Self-Assembled Lattices of Gold Nanoparticles

The structure and ordering of nanoparticles of gold functionalized with n-alkyl thiol molecules are studied both experimentally and theoretically. Samples where produced using n=6 to n=16 alkyl thiol molecules. High Resolution Electron Microscopy coupled with image processing was used to study the gold particle structure. The details of the particle structure are discussed. We found that when the gold surface is saturated with thiol molecules there is some tendency to produce molecules with a disulphide structure. We also show that ordered arrays of particles can be produced using Langmuir-Blodgett techniques. The crystal structure of the films produced is studied and found to be 3D hcp. We also report that thiol covered gold particles with a size of 5 nm present a rounded shape suggesting that thiol molecules might induce an isotropic surface energy. It is found in the theoretical calculations that a strong bond between gold and sulphur is required to stabilize the complex metal-n-alkyl thiol. It is predicted that otherwise a heavily distorted nanocore will be formed. This is contrary to the observed structure of the particles.     

Electrochemical Studies of Water-Soluble Palladium Nanoparticles

Aqueous-soluble monolayer-protected palladium nanoparticles were synthesized by hydrogen reduction of Pd(II) in a water solution. The particles were then further functionalized by incorporating multiple copies of mercapto derivatives of viologen into the particle protecting monolayers. The electrochemistry of the viologen moieties with the particles dissolved in solution or immobilized onto electrode surfaces was carefully studied using various electrochemical techniques. The particle molecular capacitance was evaluated by rotating-disk-electrode voltammetry and the electron-transfer rate constant of the particle-bound viologen moieties was estimated by impedance measurements.     

Unexpectedly low affinity of aromatic disulfides for π-stacking interactions of the arene-polyfluoroarene type

1,2,3,4,5-Pentafluorodiphenyl disulfide (1) was synthesized from C₆F₅SCl and C₆H₅SSiMe₃ in quantitative yield. The homo-crystals of disulfide 1 and co-crystals of 1,1′,2,2′,3,3′,4,4′,5,5′-decafluorodiphenyl disulfide (2) with naphthalene (stoichiometry 1:2, complex 4) and diphenyl disulfide (3) with octafluoronaphthalene (stoichiometry 2:1, complex 5) were prepared followed by XRD characterization. In the crystal lattice of 1, face-to-face and face-to-edge Ph_H/Ph_F orientations of neighboring rings were observed together with face-to-edge Ph_F/Ph_F orientations. For the face-to-face Ph_H/Ph_F orientation, the large offset of Ph_H and Ph_F groups excludes their π-stacking interaction which is very non-typical of the field. The crystal lattice of 4 reveals standard π-stacking interactions of the arene-polyfluoroarene type. While in the lattice of 4 each Ph_F ring interacts alternating with naphthalenes, in 5 two disulfides 3 are bridged by one octafluoronaphthalene with only one of the Ph_H rings of each disulfide interacting with the polyfluoroarene π-system. The large offset of neighboring molecules excludes however their π-stacking interactions in complex 5. An attempt to prepare 2/3 co-crystals failed.