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In this study, CNCs-TiO2 heterojunctions were synthesized successfully via a two-step method. The obtained materials were systematically characterized by a series of technologies including XRD, TEM, HRTEM, FT-IR, XPS, UV-DRS, PL and EIS. Moreover, the photocatalytic activity of CNCs-TiO2 was evaluated by the photodegradation of crystal violet (CV) under UV and visible light irradiation. The results of characterization demonstrated that the CNCs-TiO2 heterojunctions were formed. For composite CNCs-TiO2, the anatase TiO2 was uniformly dispersed on the surface of CNCs with graphite structures via a new chemical bond, Ti O C and the growth of crystalline grains was inhibited. The photo-absorbing range of TiO2 was extended to the visible light region after coupling with CNCs leading to the enhancement of light-harvesting ability. In addition, compared with pure TiO2 particles, the recombination of photoinduced electrons and holes was restrained. The photodegradation experiment indicated that the CNCs-TiO2 exhibited enhanced photocatalytic activity in contrast with TiO2 under UV and visible light irradiation, which was the result of the combined action of improved adsorption capability, enhanced light harvesting performance and efficient charge separation and transfer. The degradation of CV in the photocatalytic system followed the pseudo-first-order kinetics model. Lastly, the main mechanism for the enhanced photocatalytic activity of CNCs-TiO2 was significantly put forwarded.

BiCuSeO based oxide show excellent thermoelectric performance due to its low thermal conductivity and moderate Power factor. There is rare study on the same crystal structured BiCuSO with lower cost and more earth abundance. The thermoelectric performance of BiCuSO is limited by its high resistivity result from its low carrier concentration and large band gap. In this paper, p-type polycrystalline BiCuSO doped with Pb was fast prepared by one-step high pressure method and the composition dependent thermoelectric properties was studied. The electrical resistivity and Seebeck coefficient of Bi1-xPbxCuSO both decreased monotonically with increasing Pb content due to the increased carrier concentration. The power factor was improved and the thermal conductivity was suppressed by Pb doping. The maximum figure of merit, ZT∼0.14 @ 700 K was obtained for the Bi0.975Pb0.025CuSO sample, which makes them promising candidates for thermoelectric applications.

Recently, it was found that element semiconductor tellurium (Te) behaved a high thermoelectric (TE) performance. Further enhancement of its TE performance was expected in decreasing phonon thermal conductivity. In this paper, element semiconductor Te doped with arsenic (As) and alloyed with selenium (Se) was prepared by one-step high-pressure method. Trace amounts of As doping could increase the carrier concentration of Te effectively and thereby optimize its power factor. The phonon thermal conductivity of Te was depressed sharply, due to the effect of high-pressure compression (introducing dislocations, lattice curvatures and nanograins) and Se alloying (introducing point defects and crystal dislocation). The beneficial effect of As doping on the power factor, high-pressure compression and Se alloying on thermal conductivity led to a peak ZT of 0.81 at 540 K for Te doped with 0.5 mol% As and alloyed with 10 mol% Se.

In this report, a composite photocatalyst consisting of cobalt phthalocyanine sulfate (CoPcS) and TiO2 was prepared by a facile synthesis. Careful characterizations and measurements indicate a covalent grafting of CoPcS onto TiO2 through Ti–O–S linkages, acquiring an intimate heterojunction between TiO2 and CoPcS. The obtained composite was evaluated for its photocatalytic activity toward the degradation of methyl blue (MB) under visible light irradiation. The evaluation showed a significantly enhanced degradation rate of MB by CoPcS/TiO2. The improved photocatalytic performance of CoPcS/TiO2 was attributed to the photosensitization of TiO2 by CoPcS, charge separation by electron transfer at the interface of the heterojunction formed between CoPcS and TiO2, and oxygen activation via CoPcS. A synergetic mechanism in improving the photocatalytic performance of TiO2 by CoPcS was investigated.

BiCuSeO based materials have been drawn much attention since they were found to be excellent thermoelectric materials recently. Apart from high performance, the time and energy-efficient synthesis of BiCuSeO is also essential for its commercialization. In this paper, a simple one-step high pressure method was used to quickly synthesize the copper-deficient BiCuSeO. The introduction of Cu vacancy improves the carrier concentration and power factor. Through the phonon scattering of fine grains and crystal defects caused by Cu deficiency and high pressure compression, an extremely low phonon thermal conductivity of BiCu0.94SeO ~ 0.3 Wm−1K−1 @ 750 K is obtained. An enhanced ZT ~ 0.87 at 750 K is obtained for BiCu0.94SeO. This value is twice higher than that of the original BiCuSeO, compared with the traditional time-consuming method.

Recently, it was found that element semiconductor tellurium (Te) has a high thermoelectric performance. However, it needs to be doped with high-toxic arsenic (As) to tune the carrier concentration of Te. In this paper, low-toxic bismuth (Bi) was employed as dopant to optimize the thermoelectric performance of Te combining with a high-pressure synthesis method. The effect of substituting Bi on the electrical transport and thermal transport properties of Te has been investigated. The results show that the solubility limit of Bi in Te is about 0.1 mol%. However, the trace amounts of Bi doping can tune the carrier concentration of Te effectively and thereby optimize its power factor. The thermal conductivity of non-doped Te prepared by high pressure is much lower than that of the sample prepared at ambient pressure. And Bi doping can further decrease the value due to the phonons scattered by the heavy impurity atom. An enhanced figure of merit ZT ~ 0.72 was obtained at 517 K, which is about four times that of non-doped Te and is comparable to the state-of-the-art thermoelectric alloys with more complex composition such as Bi2Te3 and PbTe.

In this paper, hydrothermal approach combined with high pressure sintering method was employed to synthesize PbS. The X-ray diffraction results show that single phase PbS can be obtained by a simple hydrothermal method. The scanning electron microscope results show that the PbS sample has nearly cubic shape and preserves well crystallized and coarse grains after high pressure sintering. The thermoelectric performance of PbS obtained in this study is comparable to that of a PbS sample prepared by conventional method. The carrier type and concentration of PbS can be tuned effectively by doping with Bi. The maximum figure of merit for PbS doped with 1 mol% Bi reaches 0.44 at 550 K, which is about 30 % higher than that of undoped PbS. These results indicate that hydrothermal method provides a viable and controllable way of tuning the electrical transport and thermoelectric properties for PbS.

Lignocellulosic biomass contains about 45% cellulose. The total reducing sugars (TRS) obtained from lignocellulosic materials is beneficial to the sustainable development. Natural deep eutectic solvents (NADESs) provide an attractive alternative for the “green” conversion of cellulose. In this work, series of amino acids based NADESs with FeCl3.6H2O as ligands catalyst were synthesized and characterized by in situ IR, FT-IR, 1H NMR and TG-DTA. NADESs showed great thermal stability. The efficient hydrolysis performance of cellulose in NADESs was investigated under mild conditions. The influencing factors such as the type of NADESs, reaction temperature, reaction time, and FeCl3.6H2O addition on the TRS yield were studied. The optimized process conditions for hydrolyzing cellulose in L-Proline/ Ethylene glycol/FeCl3.6H2O were molar ratio 1: 2: 1, reaction time 120 min and temperature 120 °C. The yield of total reducing sugar was 66.7%. The conversion mechanism was also investigated.

In this work, undoped semiconductors, germanium (Ge) and germanium tin (GeSn), were grown on ferrimagnetic insulator yttrium iron garnet (YIG) thin films using ultra-high vacuum molecular beam epitaxy. The crystallinity of the structure was determined from x-ray diffraction and high-resolution transmission electron microscopy combined with energy dispersive x-ray spectroscopy. Both spin pumping and inverse spin Hall effects (ISHEs) of YIG/Ge and YIG/GeSn heterojunctions have been investigated with the help of broadband ferromagnetic resonance (FMR). We observe that the spin mixing conductances of YIG/Ge (60 nm) and YIG/GeSn (60 nm) are 5.4 × 1018 m−2 and 7.2 × 1018 m−2, respectively, responsible for giant spin current injection. Furthermore, it is found that spin pumping injects giant spin current from ferrimagnetic YIG into the Ge semiconductor. The infrared laser modulated ISHE was examined using heavy metal platinum as a spin current collector. Also, it has been noted that the variation in the power of laser irradiation significantly changed the ISHE voltage of YIG/Ge/Pt spin junctions, saturated magnetization, FMR linewidth, and Gilbert damping parameter of YIG, which could be attributed to the laser-induced thermal effect. The outcomes from this study are promising for the development of Ge-based spintronic and magnonic devices.