The aim of this study was to investigate the effects of reaction temperature on the photocatalytic activity of TiO2 with Pd and Cu cocatalysts. N2 sorption, transmission electron microscopy and high-resolution transmission electron microscopy were used to characterize the specific surface area, pore volume, pore size, morphology and metal distribution of the catalysts. The photocatalytic destruction of methylene blue under UV light irradiation was used to test its activity. The concentration of methylene blue in water was determined by UV-vis spectrophotometer. Pd/TiO2 catalyst was more active than Cu/TiO2 and TiO2. At 0–50 °C reaction temperature, the activity of TiO2 and Pd/TiO2 increased with an increase of reaction temperature. When the temperature was as high as 70 °C, the reaction rate of TiO2 drop slightly and Pd/TiO2 became less effective. In contrast, Cu/TiO2 was more active at room temperature than the other temperatures. The results indicate that the photocatalytic activity of the catalyst is influenced by the reaction temperature and the type of cocatalyst. When the reaction temperature is higher than 70 °C, the recombination of charge carriers will increase. The temperature range of 50–80 °C is regarded as the ideal temperature for effective photolysis of organic matter. The effects of reaction temperature mainly influence quantum effect, i.e., electron-hole separation and recombination.

In this study, wearable devices are made using wireless vertical-type light-emitting diode (LED) packages of a transparent conductive film coated on flexible colorless polyimide (PI) with 50 μm thickness. The low-stress ultrathin transparent conductive multilayers are deposited on the PI using high-power impulse magnetron sputtering at 65 °C. It can be used as the electrode in an ultraflexible photoplethysmography (PPG) biosensor. The nearly stress-free multilayer, consisting of a Ag layer with 20 nm thickness sandwiched between indium tin oxide (ITO) layers with 30 nm thickness, is transparent to infrared (940 nm) and exhibits a sheet resistance and resistivity of 5.7 Ω/sq. and 4.57 × 10 −5 Ω•cm, respectively. We fabricate a PPG biosensor with a vertical-type infrared LED bonded onto the flexible ITO/Ag/ITO/PI. We demonstrate that our PPG biosensor is a sensitive and accurate screening tool for the detection of pulsation signals and the heart rate (HR). The standard deviation of HR detections is as low as 2.6 bpm, satisfying the standard of <5% for approximately 3.5 bpm set by the AAMI SP10/ISO 81060-2:2009. This kind of a PPG biosensor can be applied to wearable devices for healthcare monitoring applications.