•Embedding CQDs into OLEDs to modulate devices performance.•WOLED exhibits a linear optical modulation as excitation voltage change.•WOLED turn-on voltage is 12 V, which is reduced by 40% than reference device.•OLED could obtain high luminous brightness with a lower voltage.In this work, carbon quantum dots (CQDs) are embedded as a functional material into white-organic-light-emitting diodes (WOLEDs) devices with a structure of dual-light-emitting layer. When the forward voltage is applied on devices ranging from 14 V to 22 V, the CIE coordinates of CQDs WOLEDs changed from (0.27,0.29) to (0.34,0.37) which exhibits linear optical modulation effect. Meanwhile the as-fabricated CQDs WOLEDs obtain excellent optical and electrical properties. By embedding CQDs, WOLEDs with a low turn-on voltage of 12 V which is 40% lower than reference devices can be achieved. Moreover, the devices could also obtain high luminous brightness with a lower voltage. Such superior properties are attributed to the CQDs multiple exciton generation (MEG) effect. The results demonstrate that CQDs as functional materials of WOLEDs may open up new thoughts to develop the optically modifiable WOLEDs and the low power consumption optoelectronic devices.Download high-res image (309KB)Download full-size image

In this paper, CuO nanoparticles were synthetized via a sol–gel method and their corresponding gas sensor was achieved simultaneously. CuO nanoparticle samples were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and field emission scanning electron microscopy, respectively. The results show that the sample we have synthesized was CuO and the morphology of the sample was nanoparticles with an average diameter of ∼100 nm. We determined the operating temperature of the gas sensors to be 220 °C, considering their appropriate sensitivity, rapid response and the uniformity of testing. Under this working temperature, the sensitivity and response/recovery time of the gas sensor were tested with acetone, methanol and ethanol gas. It was found that the CuO nanoparticles gas sensor performed a high response to the low concentrations of these three gases. At a gas concentration of 0.1 ppm and 10 ppm, the response to the three gases was about 2.5, 1.9, 2.7 and 5.3, 5.9, 5.3, respectively. It is believed that the CuO nanoparticles may be a promising candidate for low concentration reducing volatile organic gases sensing applications.

The hierarchical flower-like CuO nanostructure was synthesized by a facile sol–gel method without template. Indirectly-heated sensors are fabricated by coating the sol–gel on ceramic tubes with signal electrodes and subsequent annealing. The obtained nanostructures are analyzed by X-ray diffraction and scanning electron microscopy. Their gas sensing performances were investigated. The results indicated that the sensor based on hierarchical flower-like CuO exhibited excellent sensing properties towards ethanol, formaldehyde, acetone and dimethylbenzene. The sensor based on the CuO exhibited the optimal gas sensing performance, giving a ppb-level detection limit and a high response (Rg/Ra) of 1.378 to 50 ppb formaldehyde at 250 °C. The response and recovery time of the flower-like CuO nanostructure sensor are 11.9 and 8.4 s, respectively. The significantly enhanced sensing properties to formaldehyde could be attributed to the changes in crystallite size and specific surface area. The results indicate that the hierarchical flower-like CuO nanostructure gas sensor can be a simple and useful platform for formaldehyde and other volatile organic compounds sensing application.

Nickel oxide (NiO) flower-like hierarchical nanostructures were obtained by electrodeposition and oxidation methods. The surface morphology and structure of the fabricated NiO were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The gas sensing characteristics toward toluene gas are investigated. The sensors based on this nanostructures exhibit a high response to 5 parts-per-million (ppm) of toluene (ratio of resistance to gas and air = 2.63) under an operating temperature of 250 °C. Furthermore, the response and recovery time to 2 ppm can reach 13.6 s and 24.5 s, respectively. The results indicate that the flower-like nanostructure is a potential candidate for gas sensors with good performances for practical applications.

A series of white-light-emitting NaSrPO4:Eu2+, Mn2+ phosphors were successfully synthesized by solid-state reaction and their photoluminescence properties were investigated. The NaSrPO4:Eu2+, Mn2+ phosphor system exhibits a broad excitation band in the wavelength range of 250–420 nm, which is well-matched with ultraviolet (UV) light-emitting-diode (LED) chips (typically 365 nm). As a result of fine-tuning of the emission composition of the Eu2+ and Mn2+ ions, warm-white-light emission can be realized in a single host lattice under 365 nm excitation. Efficient resonant energy transfer from the Eu2+ to Mn2+ ions has been observed. The energy transfer efficiency and critical distance were calculated. The results indicate that the developed phosphor can be used as a potential candidate for white LEDs.