Jihua Guo

A technique for controlling the alignment of silver nanowires with an electric field

Highly aligned silver nanowire arrays are synthesized under direct current electric field (DCEF) treatment by a solid state ionics method without any template at normal temperature and pressure. The degree of alignment of the synthesized nanowires increases with increase of the DCEF strength. The mechanism of the effect of the DCEF on the nanowire alignment is discussed briefly. Moreover, the alignment of the individual nanowires in a bundle is further proved by observing the polarization dependence in the experiment of the polarized reflection measurements.

Synthesis of copper nanowires under a direct current electric field.

Nanowires composed of pure copper were synthesized using (KI)(1.5)(CuI)(8.5) thin film under a direct current electric field (DCEF). The (KI)(1.5)(CuI)(8.5) film was used as the medium for transmitting cuprous ions. Investigation shows the copper nanowires with diameters in the range of 20-150 nm were single crystals with a face-centred cubic (fcc) structure. The electric field strength (EFS) was also found to play an important role in determining the diameter of the nanowires.

Shape-controlled synthesis of silver nanostructures

At room temperature, without any template and in the solid phase, shape-controlled silver nanostructures are synthesized using solid electrolyte RbAg(4)I(5) thin film under direct current electric field (DCEF) treatment. With different DCEF strengths, we have synthesized silver single-crystalline nanowires, nanotubes, nanoparticles and nanoframes. The growth mechanism and the relationship between the DCEF strength and the synthesized nanostructures are discussed briefly.

A novel application of the solid electrolyte thin film for preparing copper nanowires

We report a novel application of the solid electrolyte K-Cu-I thin film for preparing copper nanowires. The K-Cu-I film was prepared by depositing a mixture of KI and CuI powders on a heated glass substrate in vacuum and had a copper ion conductivity of 1.5x10-3Ω-1cm-1 at 540K. At 540K, being applied a direct current (DC) electric field of 1.0x104 V/m, the copper ions migrated toward cathode through the K-Cu-I film and congregated to form nanowires at the edge of the cathode. The copper nanowires were about 40~100nm in diameter and several micrometers in length.

The transmission of organic group in solid electrolyte film

We found a new solid electrolyte K-Cu-I thin film which can transmit the organic group (OG). The film was prepared by depositing a mixture of KI and CuI powders on heated glass substrate in vacuum. Under direct current (DC) electric field, the OGs can migrate toward cathode through the K-Cu-I film and congregated at the edge of the cathode. At room temperature, the film had an OG conductivity that can reach up to 0.15Ω-1cm-1 when the electron conductivity was ignorable (σ≤10-4Ω-1cm-1).

Improvement and application of scanning near-field optical microscope based on a piezoelectric bimorph shear force beam

A non-optical shear-force detection method to control the probe-simple distance for a scanning near field optical microscope (SNOM) is proposed. A rectangular piezoelectric bimorph beam is designed so that one piezo layer of the beam is used for vibrating the scanning probe and the other for detecting the vibration. Optical fiber probe is attached on one side ofthe beam to detect the shear force. When the beam is excited at resonance by the stimulation piezo layer, the other detecting layer can generate a maximum piezo voltage. The amplitude ofthe piezo voltage will decrease as the fiber tip gets close to the sample because ofthe shear force interaction experienced by the tip. The oscillating amplitude change, picked up from the detecting piezo layer, severe as feedback and shear force imaging signal. Shear force topographic and optical images of mother disc of compact disk and multicomponent compounds (Rb0 5Cs0.5Ag4I5) thin films have been taken. The results show that the improved system is easy-to-use and fit for study ofvarioi.is thin films.

Imaging of green fluorescent protein in live plant by scanning near-field optical microscopy

An auxin/IAA induced in vivo green fluorescent protein (GFP) in a living plant Arabidopsis root has been studied by a scanning near-field microscope in transmission mode. The promising near-field images of the inducible GFPs at sub- surface of a plant cell suggest that they may locate proximity to the cell wall, i.e. both sides of and in the cytoplasm membrane. The clear and faint fluorescent spots with 1-3 micrometers showed that the proteins localized nearer and farther to the cell wall, respectively. All GFP molecules gathered together in a cell, and no individual GFP was observed in the experiment.

Improvement of tapping-mode scanning near-field optical microscope

The commercial crystal tuning fork glued with an optical fiber probe is used as the sensitive detecting element for the tapping-mode scanning near-field optical microscopy. Firstly, the single-mode optical fiber is etched down to a small diameter to decrease the burden of the tuning fork. Secondary, the fiber is etched for the second time to form the sharp tip with large cone angle. Thirdly, the fiber probe, with nanometric tip and high light throughput, is glued to tuning fork by Cyanoacrylate Adhesive. The measured quality factor, Q, of the tuning fork/optical fiber probe assembly prepared in this way is higher than 300. The optical signal is modulated to the frequency of the tuning fork by optical fiber probe as it is detecting the topography of sample. The high-resolution of the tapping- mode detector is proved by imaging the topography of the grating and biological cell.