Hitoshi Nagato

Electrical Control of LSPR from Gold Nanoparticles Using Electrochemical Oxidation

Large shift of localized surface plasmon resonance (LSPR) spectrum of gold nanoparticles was attained by electrochemical oxidation of the nanoparticle surface. This oxidation occurred in a cell consisting of a pair of indium tin oxide (ITO) electrodes with water medium between the electrodes. On one side of the ITO electrode, the gold nanoparticles were adsorbed. The LSPR spectrum was moved consecutively to the red by increasing the applied positive voltage. By the application of 5 V to the cell, the spectrum shift as large as 55 nm was obtained. Though the spectrum shift has already been observed by changing liquid crystal (LC) orientation surrounding gold nanoparticles, the amount of the shift was not large (11 nm). That was because the variation of the effective refractive index of LC was rather small. Our large shift due to electrochemical oxidation resulted from the large refractive index of Au-O. The upper limit of the LSPR spectrum shift by our method is estimated to be 138 nm.

New ion-jet printing head controlled by a low-voltage signal

The ion-jet printing method controls the ion flow directly to make an electrostatic latent image on an insulated layer. This printing method has several advantages over laser printing, such as high printing speed and simple maintenance. However, conventional ion-jet method poses a problem, particularly for office printer applications, because a high- voltage circuit is required to control the ion flow. We developed the new ion-jet printing method to solve this problem. The new process uses a precharge to accelerate the ion flow to the insulated layer, and the high-voltage bias is eliminated from the head. So, the new ion-jet head permits controlling the ion flow by a low-voltage signal. Experimentally, we attained a printing speed of 20 ppm and a resolution of 400 dpi at the control voltage of -30 V, and succeeded in printing Chinese characters with 32 X 32 dots per 2 mm square.

Bidirectional printing method for a thermal ink transfer printer

All thermal transfer serial printers currently use one-directional printing. A new bidirectional printing method for a thermal transfer printer is proposed. The new method features an electro-thermal ink transfer printing system and one-directional ink ribbon feeding at a constant speed. The image quality problems which were found in a preliminary experiment have been solved by using a newly developed ribbon and controlling the drive current pulse.