Search

Non-thermal plasma is a promising technology for high purity nanomaterial synthesis in a fast, flexible and controllable process. Gliding arc discharge, as one of the most efficient non-thermal plasmas, has been widely used in gas treatment but rarely studied for the nanomaterial synthesis. In this study, a comparison study for carbon nanosheets synthesis including toluene dissociation and graphite exfoliation was investigated in a 2D gliding arc reactor at atmospheric pressure. The effects of gas flow rate, precursor concentration and power input on the structures of carbon nanosheets produced through the two synthesis routes were explored and compared. Amorphous carbon nanosheets were produced in both approaches with a few crystalline structures formation in the case of toluene dissociation. The thickness of carbon nanosheets synthesized from graphite exfoliation was less than 3 nm, which was thinner and more uniform than that from toluene dissociation. The flow rate of carrier gas has direct influence on the morphology of carbon nanomaterials in the case of toluene dissociation. Carbon spheres were also produced along with nanosheets when the flow rate decreased from 2 to 0.5 L/min. However, in the case of graphite exfoliation, only carbon nanosheets were observed regardless of the change in flow rate of the carrier gas. The generated chemical species and plasma gas temperatures were measured and estimated for the mechanism study, respectively.

Whitening cosmetics have a large market scale and broad development prospects, while whitening products of traditional Chinese medicine have always been a research hotspot. In this study, the whitening active extract of Platycodon grandiflorum (PGE) was isolated and purified for the first time, and the whitening activity mechanism and chemical composition of PGE were elucidated. A total of 45 components were identified via high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis, including arbutin, syringin, chlorogenic acid, platycoside E, platycodin D3, baicalin, platycodin D, and luteolin. The scavenging rates of PGE toward DPPH and ABTS free radicals were 98.03% and 84.30%, respectively. The inhibition rate of PGE toward tyrosinase was up to 97.71%. The PGE had significant anti-inflammatory effects on RAW264.7 macrophages stimulated by lipopolysaccharide (LPS) and had significant inhibition effects on tyrosinase and melanin generation of B16F10 cells stimulated by α-MSH. The results showed that the PGE achieved a synergistic whitening effect by inhibiting the activation of oxygen free radicals on tyrosinase, antioxidation, anti-inflammatory effect, enzyme activity, and melanin generation. As a whitening agent extracted from natural plants, PGE has great potential in the research and development of plant whitening cosmetics, which lays a foundation for the further development and utilization of Platycodon grandiflorum resources and also provides a theoretical basis for the development of green and organic whitening cosmetics.

Semen Ziziphi Spinosae (Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chou) is a functional food and a traditional Chinese medicine (TCM) in China. Herein, Semen Ziziphi Spinosae protein (SZSP) was prepared by an alkaline extraction and acid precipitation method, of which the structural, physicochemical, functional and emulsion properties were investigated. Results showed that SZSP contained an ideal amino acid composition. The structural properties of the proteins were characterized using Fourier transform infrared spectroscopy (FTIR), relative fluorescence and circular dichroism (CD) spectroscopy analysis. The electrophoresis profiles showed that the main molecular weight of the protein components was about 10–40 kDa and contained some glycoproteins. Differential scanning calorimetry analysis indicated that the denaturation temperature of SZSP was 110.5 °C. The functional properties showed that SZSP has good water and oil absorption capacity, high emulsifying ability and foaming stability. The overall results suggest that SZSP is a promising protein source for the functional food industry.

Carbon dots have recently emerged and gained much interest as a new class of carbon nanomaterials especially suited for biological applications owing to their characteristic advantages such as non-toxicity, bio-compatibility, and element abundance. In this study, a fast and effective method was developed for the synthesis of fluorescent carbon dots by microplasma technology, at atmospheric pressure, using isopropanol as the only reactant. Characterizations of the synthesized carbon dots including the investigation of their structure, morphology and optical properties were performed. The results show that the carbon dots produced have a narrow size distribution (average diameter of 1.78 nm) and are amorphous and graphitic in nature. The photoluminescent study indicates that the carbon dots present an excitation-dependent emission property with the excitation wavelengths in a range of 310–410 nm. The high density electrons produced by microplasma induce the chemical reactions and accelerate the formation process of functional groups doped carbon dots.

We present an innovative approach for reacting carbon dioxide and water to give syngas by combining heterogeneous catalysis and non-thermal plasma techniques. This approach utilizes an abundant water and nickel catalyst, and mitigates the thermodynamic penalty by using a Dielectric Barrier Discharge (DBD) plasma reactor. Argon dilution was used in the experiment to reduce the exothermic recombination of hydrogen and oxygen, which is considered as the major hurdle for H2O conversion. As a result, the syngas ratio was dramatically improved from 0.07 to 0.86. In addition, the conversions of CO2 and H2O were improved by packing Ni/γ–Al2O3 catalysts into the DBD reactor. The yields of H2 and CO were up to 13.8% and 5.6% respectively. The conditions for plasma catalysis and the catalyst characterization are presented and discussed.

In this study, an effective approach was presented for the synthesis of N-doped carbon dots via a microplasma-assisted process at atmospheric pressure. The effects of operation parameters on the surface groups and photoluminescence (PL) property of carbon dots were studied in detail. Nitrogen element was successfully doped as N H group and pyrrolic–like structure in the carbon dots. The morphology, structures, chemical compositions and photoluminescence properties of N-doped carbon dots were systematically characterized. The generated chemical species and mechanism were monitored and studied by optical emission spectroscopy. The synthesized particles owned excitation-dependent emission property with a quantum yield up to 9.90%. The plasma treatment time and operating voltage affect the carbonization degree, doping state of nitrogen and particle size, resulting in different PL behaviours. The variation of electrode sizes has slight effects on the yield of N-doped carbon dots from 0.31% to 0.42% owing to the differences in electron density.

We have developed a phenolic resin with a structure modified according to the mechanism for its consolidation with sand. Application of the new resin allows us to reduce the cost of sand control measures because less resin must be used. We have studied the factors affecting the resin sand consolidation strength. We propose a method for injecting the resin into the formation, on the surface of calcium carbonate particles suspended in water.

An oil displacement agent consisting of nonionic and anionic surfactants and emulsion stabilizers has been developed to enhance oil recovery from heavy oil reservoirs. The experimental results show that the proposed displacement agent enhances oil recovery by more than 20 % compared with water flooding and that the emulsion contained in the fluid produced can be easily broken (demulsified). The mechanism of action for the displacement agent is described.