Zeta potential measurement on the surface of blue-green algae particles for micro-bubble process.

Any kind of blue-green alga produces metabolites of musty substances and toxins. Therefore, it is necessary to remove the blue-green algae, and processing also including nutrient removal is desired for the water quality improvement of eutrophic lakes. The purpose of this study has been to investigate the possibility of a flotation system using a hybrid technique (chemical compounds and electrostatic bridge) applied to raw water containing phytoplankton with high pH of water, and to examine the zeta potential value of phytoplankton surface and the removal efficiency for phytoplankton, ammonia, nitrogen, and phosphoric acid.The results were as follows: firstly, zeta potential of M. aeruginosa particles was observed to achieve charge neutralization on their surface by adhesion of magnesium hydroxide precipitation with increasing pH. Secondly, maximum removal efficiency concerning chlorophyll-a was observed as 84%, and this efficiency was obtained in the condition of pH > 10, and magnesium hydroxide precipitation was observed. Thirdly, in the pH condition that the maximum removal efficiency of chlorophyll-a was obtained, the removal efficiency and the amount of decrease of NH(4)-N and PO(4)-P before and after the change of pH values were observed as 6.7% (0.04 mg-P/L) and 63.6% (0.07 mg-N/L), respectively.     

Control of apex shape of the fiber probe employed in photonscanning tunneling microscope by a multistep etching method

In this paper, we discuss about the control of the shape of the very apex of a sharpened fiber probe used in photon scanning tunneling microscope (PSTM) by means of a method based on selective chemical etching. Under ambient conditions, through a multistep etching method proposed here, fiber probes with a flattened apex having a diameter of around 15-20 nm could be produced with high reproducibility. It has also been discovered that, during the etching process, the shape of the apex of the probe takes a rounded or a flattened shape with respect to the etching time in an almost cyclic fashion and such a phenomenon could help in understanding the mechanism of the etching process. These kind of probes with flat apex after metal coating are suitable for the fabrication of apertured probes used in PSTM and also for super tips which have a promising future as nanosensors in the fields of biology and biochemistry     

Deducing structural variations of the apex of probes used in near-field optical microscopy through simultaneous measurement of shear force and evanescent intensity

We propose a simple method employing the simultaneous detection of evanescent intensity and shear force to deduce variations in the near-field optical morphology of the apex of the probes used in near-field microscopy. Fabrication of our probes involves sharpening by chemical etching, metal coating, and removal of metal from the apex. We show that through the simultaneous measurement of shear force and evanescent intensity, it is possible to detect variations in the optical morphology of the very apex of the probes during near-field imaging by a scanning near-field optical microscope.     

Near-field optical imaging of flagellar filaments of salmonella in water with optical feedback control

We report on the high-resolution observation of biological samples in water with a collection-mode near-field optical microscope (c-mode NOM) operating under optical feedback control. With rapidly decreasing evanescent field power used as the feedback signal, for the first time to our knowledge, an image of straight-type flagellar filaments of salmonella in water has been obtained. The estimated diameter of a single filament is around 55 nm with a pixel size of 10 nm. A comparison with its nominal value of 25 nm obtained from electron microscope observations under high vacuum confirms that our c-mode NOM performs high-resolution imaging in water.     

A model based on geometrical construction in designing apencil-shaped fiber probe for near-field optics

We propose a model based on geometrical considerations to determine the etching times required in fabricating a pencil-shaped fiber probe. In this model, we introduce a minimum etching time which is defined as the time required for having a zero apex diameter. Based on its value, the total etching times required in fabricating the pencil-shaped probe could be determined. We have found that the theoretically determined minimum etching time of 2.1 min agrees very well with our experimental value of 2 min     

Fabrication of a pencil-shaped fiber probe for near-field optics byselective chemical etching

We propose a novel method by chemical etching using hydrofluoric (HF) acid and a buffered HF solution (BHF) to fabricate a pencil-shaped fiber probe for near-field optics. We succeeded in producing such probes with high reproducibility using a dispersion-compensating fiber having the high GeO₂ doped core. The method involves tapering of the cladding, then sharpening of the core. The fabricated probe has a conical tip with a cone angle of 20° and an apex diameter of less than 10 nm     

Reproducible fabrication of a fiber probe with a nanometric protrusion for near-field optics

We propose a new type of fiber probe with a nanometric protruding tip emerging from a metal film and describe a novel method, called the selective resin-coating method, for fabricating such probes. It is a reproducible etching process consisting of four steps and can be applied to silica fibers sharpened by selective chemical etching. With this method, we obtained tips with the apex diameter and the foot diameter of the protrusion being less than 10 and 30 nm, respectively, when the gold film was ~120 nm thick.