Electrochemiluminescence (ECL), a light-emitting phenomenon induced by electrochemical redox reactions, has potential applications in lightweight and flexible light-emitting devices. Previously, an ultrafast ECL response of <100 μs was successfully achieved under application of alternating current voltage by using a DNA-modified electrode including Ru(bpy)₃²⁺, an orange ECL material. In this study, we investigated effect of electrolyte composition on the fast responsive ECL in the DNA/Ru(bpy)₃²⁺ hybrid film-based ECL device. As a result, the ECL intensity and lifetime of ECL were improved by introducing additional Ru(bpy)₃²⁺ into the electrolyte solution. The increase concentration of Ru(bpy)₃²⁺ inhibited dissolution of aggregated part formed on DNA/Ru(bpy)₃²⁺ hybrid film and increase in the amount of reactive charge in the aggregated part.

The need for energy harvesting technology as a power source for isolated small electronic devices is increasing. Our body heat or exhausted heat is one of the promising energy sources, and therefore thermoelectric technology is attracting attention. For such applications, the ease of installation and the user's comfortableness should be emphasized. Measuring whether the required power can be generated at an acceptable cost without increasing or decreasing the naturally occurring heat flow is also essential. In this paper, we review the progress of thermoelectric cloths, which have been studied by the author's group with a consistent policy, and propose a direction in which wearable thermoelectric generators should be developed. We hope this paper will serve as a hint for those conducting similar research.

There is growing interest in “vibration energy harvesting,” which is the process of acquiring relatively small amounts of electrical energy from the vibration energy. The greatest feature of the technology is that it can provide power permanently and is expected to be applied to devices that do not require battery replacement. Such technology will be used in the future for power supply applications for massively distributed sensor systems symbolized by the internet of things (IoT) and cyber physical system (CPS). Piezoelectric polymers are functional materials characterized by their softness, but they are also expected to be used for vibration power generation applications focusing on their processability and large surface area. In this paper, the characteristics of piezoelectric polymers and examples of vibration power generation will be introduced.

In recent years, electret-based vibrational energy harvesters (E-VEHs) have attracted attention as autonomous power sources for low-power devices such as sensors. Electrets, which are insulating materials that (quasi-) permanently hold electric charge or polarization, play a crucial role in E-VEHs. However, their fabrication traditionally requires charging of insulating materials using methods like corona discharge, which has been a limiting factor in the productivity of E-VEHs. To address this challenge, we proposed E-VEHs utilizing the spontaneous orientation polarization (SOP) phenomenon. Thin films of materials such as tris- (8-hydroxyquinolinato) aluminium and 1,3,5-tris (1-phenyl-1H-benzimidazole-2-yl) benzene exhibit the SOP phenomenon, where permanent dipoles naturally orient perpendicular to the substrate in average, generating surface potentials of several volts over 100nm film thickness. By utilizing these polar organic molecules as electrets, we have developed E-VEHs that require no charging process. This paper introduces the operational mechanism of SOP-based E-VEHs and discusses design guidelines for performance enhancement using numerical simulations.

This paper describes the characteristics of single-walled carbon nanotube films as thermoelectric materials. Recently, the thermoelectric properties of carbon nanotubes for energy harvesting have been widely investigated. Since carbon nanotubes can be used to generate a certain amount of thermoelectric power even without any special modification, many reports are more application-oriented than scientific. In addition, due to the complexity of the materials, it is not easy to extract the guiding principles for carbon nanotube-based thermoelectrics, and its research prospects are difficult to understand. In this paper, we first introduce our efforts to elucidate the structure-property relationship in the thermoelectric properties of single-walled carbon nanotubes. Then, focusing on chemical doping, we propose the guiding principle required for its advancement and present our recent studies using this principle.

Water on Earth has the cycle in which water evaporates from the oceans, falls to the ground as rain, and returns to the oceans through rivers. Hydropower generation uses this cycle to generate electricity. While rivers exist only locally on the ground, water vapor in the air is a resource that is accessible in most environments on Earth. In recent years, technologies enabling electricity generation using this water vapor in the air or humidity are emerging. Electricity generation using humidity has the advantage of being able to generate power in any location, even in dark places, and is attracting attention as a potential convenient energy harvesting device for powering Internet of Things (IoT) devices. This paper outlines the basic concepts of these humidity-related electricity generation technologies and various methods, as well as the research and development of hygroelectric cell being developed by the authors.

Solar radiation is the most abundant renewable energy source. However, its overall utilization remains inefficient as half of the energy is in the form of infrared (IR) light, which cannot be harnessed due to its low energy. The investigation on the method for converting the infrared light, an unused renewable energy source, into an energy resource could be an import subject for effective utilization for clean and sustainable solar energy. In addition, invisibility of IR light provides us an opportunity to invent the clear and transparent devices photo-energy conversion. In this explanatory article, I will introduce the methodology and mechanism of energy conversion of infrared light and applications for IR light responsive photocatalyst and various transparent devices.

Lanthanide elements from lanthanum (atomic number 57) to lutetium (atomic number 71) exhibit excellent luminescence and magnetic properties derived from their 4f orbital electrons. The author has been working on fabricating magnetic soft materials by doping holmium (Ho) and terbium (Tb), which have high magnetic moments among lanthanides, into polymer scaffolds. In this review, the development of colorless magnetic particles using lanthanide-doped polymers is summarized. The applications of full-color magnetic particles, fluorescent magnetic particles, and magnetic MOF (metal organic frameworks) particles with adsorption properties that take advantage of the colorless feature will also be introduced.