Search

Density function theory is performed in order to investigate the effect of Ce/N co-doping on geometry structure, electronic and optical properties of anatase TiO2. Comparing the energy band and density of states of pure TiO2 and Ce/N doped anatase TiO2. We can conclude that, the valence band of pure TiO2 is main composed of O 2p states and the conduction is mainly composed of Ti 3d states. For N-doped TiO2, the topmost part of the valence band is mainly occupied by N 2p states which is higher than that of the O 2p states which can narrowed the band gap. Ce doping will introduce 4f states which is involved in the conduction band. These may lead the conduction band move down. As for Ce and N co-doped, the top of the valence band is mainly occupied by an admixture N 2p, O 2p and the bottom of the conduction band is predominantly occupied by an admixture of Ce 4f ,Ti 3d. The strong interaction between the dopants and the ions lead the band gap get narrower. We predict that Ce+N doping is one of the best choices for enhancing the photoelectrochemical activity of TiO2.

Ultrasonic assisted multistage countercurrent extraction technique of ginsenosides Rb1, Rb2, Rc, Rd, Re, Rg1, and Rg2 from Panax quiquefolium L. was developed in this paper. It provides the analytic technique to determine simultaneously the seven major ginsenosides. The effects of ethanol concentration, ratio of liquid to solid, extraction temperature and extraction time on the extraction yields of the seven ginsenosides and total ginsenosides from Panax quiquefolium L.were investigated. The optimal process condition of ultrasonic assisted four-stage countercurrent extraction (4-UAMSCCE) was found using orthogonal array experimental design technique: 70% (v/v) ethanol solution, liquid: solid ratio of 10 ml/g, extraction temperature 45°C and extraction time 30 min. Under optimum process condition, the extraction efficiency of 4-UAMSCCE had been compared with those of conventional techniques including heat distillation extraction (HDE), ultrasonic assisted extraction (UAE), four-stage countercurrent extraction (4-MSCCE). Results show that the 4-UAMSCCE offers the highest ginsenosides extraction rate and considerable savings in time, energy and solvent consumption.

Imperatorin and isoimperatorin are important components of Angelica dahurica with many beneficial functions to human health. In this study, an ultrasound-assisted extraction technique has been developed for the fast extraction of imperatorin and isoimperatorin from Angelica dahurica root. The high extraction yield of imperatorin and isoimperatorin was obtained under optimum extraction conditions: ultrasonication time 20 min, extraction temperature 30°C, ultrasound power 240w, ethanol concentration 80%, and ratio of solvent volume to sample weight 12:1 (ml/g), particle size 60 meshes. Compared to heat-reflux extraction, ultrasound-assisted extraction reduced extraction time and obtained higher percentage extracted of imperatorin and isoimperatorin. Scanning electron micrographs revealed that ultrasound could result in the destruction of cell walls, which increased the mass transfer rate of the solvents into the root materials