Nao Terasaki

Plugging a Molecular Wire into Photosystem I: Reconstitution of the Photoelectric Conversion System on a Gold Electrode

Plug and play: Photoinduced electron transfer occurs from photoexcited P700 in photosystem I (PSI) to a gold surface (see picture). A novel molecular connector system is used, in which an artificial molecular wire, which is assembled on the gold surface, was plugged into PSI by reconstitution. Analysis of the photoelectron transfer kinetics proved both the output of electrons from PSI and the effectiveness of the molecular wire.

Photocurrent enhancement in a porphyrin-gold nanoparticle nanostructure assisted by localized plasmon excitation.

The nanostructured assembly of porphyrin and gold nano-particles exhibits distinct enhancement of photocurrents from porphyrin in the longer wavelength region, where the localized plasmon resonance was responsible

Ultraviolet mechanoluminescence from SrAl2O4:Ce and SrAl2O4:Ce,Ho

Phosphors with ultraviolet (UV) mechanoluminescence (ML) SrAl2O4:Ce (SAOCe) and SrAl2O4:Ce,Ho (SAOHoCe) were reported in this letter. The results reveal that the ML emission band is located at 375nm similar to photoluminescent (PL) peak, which indicates that ML is emitted from the same center of Ce3+ ions as PL. Furthermore, the addition of Ho3+ increases the UV ML intensity of SAOHoCe (56nJ∕loadcycle) considerably [approximately two orders of magnitude greater than that of SAOCe (0.21nJ∕loadcycle)]. The formation of many shallow traps (Ho3+−e−) may be responsible for this enhancement.

Blue Light Emission from Stress-Activated CaYAl3O7 : Eu

We have revealed that CaYAl 3 O 7 :Eu phosphor emits blue light under the application of mechanical stress, called mechanoluminescence (ML). The influences of sintering temperature on photoluminescence (PL) and ML were investigated in order to gain suitable synthesis conditions. The results revealed that the sample sintered at 1300°C shows strong PL and ML intensities, while further heating induces quenching of PL and ML. The ML and PL spectra are similar, which indicates that ML is emitted from the same center of Eu 2+ ions as PL. This blue ML emission can be observed by the naked eye when the sample sintered at 1300°C is compressed. Furthermore, the ML intensity of CaYAl 3 O 7 :Eu proportionally increased with the increase of mechanical load.

Stress-Induced Mechanoluminescence in SrCaMgSi2O7 : Eu

We have revealed that SrCaMgSi 2 O 7 :Eu phosphors emit blue-greenish light under the application of a mechanical stress, called mechanoluminescence (ML). The ML showed a similar spectrum to photoluminescence (PL), which indicated that ML is emitted from the same center of Eu 2+ ions as PL. Such a blue-greenish light of ML emission can be seen by the naked eye when pressing the sample. In addition, the ML intensity of SrCaMgSi 2 O 7 :Eu proportionally increased with the increase of mechanical load.

BLUE LIGHT EMISSION FROM STRESS-ACTIVATED SR2MGSI2O7:EU

We discovered that Sr2MgSi2O7:Eu phosphor emits blue light under the application of a mechanical stress, a phenomenon known as mechanoluminescence (ML). The ML showed a similar spectrum as photoluminescence (PL), which indicated that ML is emitted from the same center of Eu2+ ions as PL. The analysis of structure and thermoluminescne suggested that the origin of ML for Sr2MgSi2O7:Eu phosphor can be attributed to strain-induced electroluminescence, that is, piezoelectricity impelled the trapped electrons to escape from the trap and produce ML. Furthermore, the relation between ML intensity and compressive load is close to linearity, which indicate that this sample can be used for smart-skin and self-diagnosis applications.

Photosensor based on an FET utilizing a biocomponent of photosystem I for use in imaging devices.

We have investigated a photosensor that consists of a field emission transistor (FET) utilizing the biocomponent of the photosystem I (PSI) protein complex for use in an imaging device. The PSI was immobilized on a gold electrode via the self-assembling monolayer (SAM) of 3-mercapto-1-propanesulfonic acid sodium salt to obtain a PSI-modified gold electrode. As for the PSI-modified gold electrode, the basic photoresponses originating from the excitation of PSI, including the photocurrent (106 nA) and the photoresponse of the open-circuit voltage (photo-Voc: 28.6 mV), were characterized. Then, the PSI-modified gold electrode was linked to the gate of the FET using a lead line, and the device was successfully driven by the photoelectric signals from the PSI like a voltage follower circuit. Further, we successfully demonstrated that the PSI-based FET acts as a photosensor in imaging devices.

Green Mechanoluminescence of Ca2MgSi2O7 : Eu and Ca2MgSi2O7 : Eu,Dy

We discovered that Ca 2 MgSi 2 O 7 :Eu,Dy phosphor emits green light under the application of a mechanical stress, a phenomenon known as mechanoluminescence (ML), and this green ML emission can be seen by the naked eye when pressing the sample. The ML showed a similar spectrum as photoluminescence (PL), which indicated that ML is emitted from the same center of Eu 2+ ions as PL. Furthermore, the addition of Dy 3+ increases the green ML intensity of Ca 2 MgSi 2 O 7 :Eu,Dy considerably-approximately two orders of magnitude greater than that of Ca 2 MgSi 2 O 7 :Eu. The formation of many shallow traps (Dy 4+ ) may be responsible for this enhancement.

Historical-Log Recording System for Crack Opening and Growth Based on Mechanoluminescent Flexible Sensor

Recently, there are innovative mechanoluminescent (ML) particles made available, each of which repeatedly emits light in response to small applied stresses even in elastic region. When dispersedly coated onto a structure, each particle acts as a sensitive mechanical sensor, while the two-dimensional emission pattern of the whole assembly reflects the dynamical stress distribution inside the structure and the mechanical information around the crack and defect. To use the remarkable advantage of the ML sensor in flexibility, electricity/lead-free, low-cost, and so forth, and to answer social needs for historical-log of stress/damage accumulation on social infra-structure, we investigate historical-log recording system for crack opening and fatigue crack growth, and finally succeed to record it with responding position and intensity reflecting the trace of propagating crack tip and stress intensity factor around the tip. Furthermore, crack mouse opening displacement accompanied by general traffic of bridge in use is successfully detected.

Photocell System Driven by Mechanoluminescence

A mechanoluminescence driven photocell system consisting of a mechanoluminescent (ML) material and a photocell was prepared. The ML material developed in our laboratory is the worlds first material developed for a practical use in the elastic deformation region. In this system, the ML composite (an epoxy pellet including europium-doped strontium aluminate (SAO:E), one of the most efficient ML materials) was used as a light source, and a silicon solar cell was used as the photoelectric converter. With the application of compressive stress to the ML composite pellet in the system, the photocurrent corresponding to the mechanoluminescence was successfully observed.