Improving Nucleation in the Fabrication of High-Quality 3D Macro-Porous Copper Film through The Surface-Modification of A Polystyrene Colloid-Assembled Template

A new approach is developed to the fabrication of high-quality three-dimensional macro-porous copper films. A highly-ordered macroporous copper film is successfully produced on a polystyrene sphere (PS) template that has been modified by sodium dodecyl sulfate (SDS). It is shown that this procedure can change a hydrophobic surface of PS template into a hydrophilic surface. The present study is devoted to the influence of the electrolyte solution transport on the nucleation process. It is demonstrated that the permeability of the electrolyte solution in the nanochannels of the PS template plays an important role in the chemical electrodeposition of high-quality macroporous copper film. The permeability is drastically enhanced in our experiment through the surface modi. cation of the PS templates. The method could be used to homogeneously produce a large number of nucleations on a substrate, which is a key factor for the fabrication of the high-quality macroporous copper film.

Transparent colloid containing upconverting nanocrystals: An alternative medium for three-dimensional volumetric display

We report an alternative medium of transparent upconverting colloid containing lanthanide ion doped NaYF4 nanocrystals for three-dimensional (3D) volumetric display. The colloids exhibit tunable upconversion luminescence with a wide spectrum of colors by adjusting the doping concentrations of the nanocrystals and the compositions of the colloids. Our preliminary experimental result indicates that an upconverting colloid-based 3D volumetric display using a convergent, near infrared laser beam to induce a localized luminescent spot near the focus is technically feasible. Therefore arbitrary 3D objects can be created inside the upconverting colloid by use of computer controlled 3D scanning systems. (C) 2008 Optical Society of America

Monodisperse raspberry-like gold submicrometer spheres: Large-scale synthesis and interface assembling for colloid sphere array

We first suggested a one-pot method to synthesize monodisperse raspberry-like submicrometer gold spheres (MRSGS) with high yield. The resulting gold spheres were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersed X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical technology. It was found that the rough structure provided by raspberry-like gold spheres led to a tremendous electrochemical active area, which was very important because these novel hierarchical gold spheres will probably find important applications in biosensors, electrocatalysis, and others.

Preparation of Pd/C catalyst for formic acid oxidation using a novel colloid method

A novel colloid method using (WO3)(n)center dot xH(2)O as colloidal source was developed to prepare Pd/C catalyst for formic acid oxidation. Transmission electron microscopy image shows that the Pd/C nanoparticles have an average size of 3.3 nm and a narrow size distribution. Electrochemical measurements indicate that the Pd/C catalyst exhibits significantly high electrochemical active surface area and high catalytic activity with good stability for formic acid oxidation compared with that prepared by common method.

Templateless, surfactantless, electrochemical route to a cuprous oxide microcrystal: From octahedra to monodisperse colloid spheres

Herein we report a simple electrochemical route for the controlled synthesis of a Cu2O microcrystal from perfect octahedra to monodisperse colloid spheres via control of the electrodeposition potential without the introduction of any template or surfactant. Perfect Cu2O octahedra and monodisperse colloid spheres have been obtained in high yield (similar to 100%).

Interdigited phospholipid/alkanethiol bilayers assembled on APTMS-supported gold colloid electrodes

The preparative procedure of a kind of phospholipid/alkanethiol bilayers on a planar macroelectrode was copied to the as-prepared gold colloid electrodes. The electrochemical and spectral results show that the bilayers on colloid electrodes are interdigited, which are different from their 2-D counterparts on a planar macroelectrode.

Application of impedance spectroscopy for monitoring colloid Au-enhanced antibody immobilization and antibody-antigen reactions

We used colloidal An to enhance the amount of antibody immobilized on a gold electrode and ultimately monitored the interaction of antigen-antibody by impedance measurement. Self-assembly of 6 nm (diameter) colloidal An onto the self-assembled monolayers (SAMs) of 4-aminothiophenol modified gold electrode resulted in an easier attachment of antibody. The redox reactions of [Fe(CN)(6)](4-)/[Fe(CN)(6)](3-) on the gold surface were blocked due to the procedures of self-assembly of 4-aminothiophenol and antibody immobilization, which were investigated by cyclic voltammetry and impedance spectroscopy. The interaction of antigen with grafted antibody recognition layers was carried out by soaking the modified electrode into a phosphate buffer at pH 7.4 with various concentrations of antigen at 37 degreesC for 30 min. The antibody recognition layers and their interactions with various concentrations of antigen could be detected by measurements of the impedance change. The results show that this method has good correlation for detection of Hepatitis B virus surface antigen in the range of 0.5-200 mug/l and a detection limit of about 50 ng/l.

Synthesis of PtNPs/AQ/Ru(bpy)(3)(2+) colloid and its application as a sensitive solid-state electrochemiluminescence sensor material

The facile synthesis of the novel platinum nanoparticles/Eastman AQ55D/ruthenium(II) tris( bipyridine) (PtNPs/ AQ/Ru(bpy)(3)(2+)) colloidal material for ultrasensitive ECL solid-state sensors was reported for the first time. The cation ion-exchanger AQ was used not only to immobilize ECL active species Ru(bpy)(3)(2+) but also as the dispersant of PtNPs. Colloidal characterization was accomplished by transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), and UV-vis spectroscopy. Directly coating the as-prepared colloid on the surface of a glassy carbon electrode produces an electrochemiluminescence (ECL) sensor. The electronic conductivity and electroactivity of PtNPs in composite film made the sensor exhibit faster electron transfer, higher ECL intensity of Ru(bpy)(3)(2+), and a shorter equilibration time than Ru(bpy)(3)(2+) immobilized in pure AQ film. Furthermore, it was demonstrated that the combination of PtNPs and permselective cation exchanger made the sensor exhibite excellent ECL behavior and stability and a very low limit of detection (1 x 10(-15) M) of tripropylamine with application prospects in bioanalysis. This method was very simple, effective, and low cost.

Electrochemical detection of DNA immobilized on gold colloid particles modified self-assembled monolayer electrode with silver nanoparticle label

The target DNA was immobilized successfully on gold colloid particles associated with a cysteamine monolayer on gold electrode surface. Self-assembly of colloidal An onto a cysteamine modified gold electrode can enlarge the electrode surface area and enhance greatly the amount of immobilized single stranded DNA (ssDNA). The electrontransfer processes of [Fe(CN)(6)](4)-/[Fe(CN)(6)](3-) on the gold surface were blocked due to the procedures of the target DNA immobilization, which was investigated by impedance spectroscopy. Then single stranded target DNA immobilized on the gold electrode hybridized with the silver nanoparticle-oligonucleotide DNA probe, followed by the release of the silver metal atoms anchored on the hybrids by oxidative metal dissolution, and the indirect determination of the released solubilized Ag-1 ions by anodic stripping voltammetry (ASV) at a carbon fiber microelectrode. The results show that this method has good correlation for DNA detection in the range of 10-800 pmol/1 and allows the detection level as low as 5 pmol/1 of the target oligonucleotides.

Site-selective self-assembly of MPA-bridged CuHCF multilayers on APTMS-supported gold colloid electrodes

(3-Aminopropyl)trimethoxysilane (APTMS)-supported gold colloid electrode was constructed by virtue of a recently developed solution-based self-assembly strategy. The preparing procedure of 3-mercaptopropionic acid (MPA)-bridged copper hexacyanoferrate (CuHCF) multilayers on a planar macroelectrode (Bharathi et al. Langmuir 2001, 17, 7468) was copied to the as-prepared colloid electrode. The optical spectra, atomic force microscopy, and electrochemistry demonstrate successful copy of the multilayer system on a macroelectrode to the as-prepared colloid electrode. Remarkably, it was found that multilayer growth is highly selective to the nanoscale sites where gold nanoparticles are immobilized, and multilayer growth does not take place on the sites without nanoparticles. Interestingly, a preliminary electrochemical investigation indicates that electrochemical properties of multilayers systems on the colloid electrode are different from their counterparts on a planar macroelectrode, which might be due to high curvature effects of the gold nanoparticles. This indicates a different motif of multilayers on the colloid electrode from that on a planar macroelectrode.