Morphology and Thermal Characteristics of Polysaccharide Extracted by Ultrasound from <i>Ophiopogon japonicas</i>

The crude polysaccharide UPOJ was extracted by ultrasound from Ophiopogon japonicas and purified by DEAE-cellulose52 column and Sephadex G-150 gel column. Purified polysaccharide UPOJ-DS was obtained. The thermal characteristics of UPOJ-DS were studied by using the thermal analysis system Q1000DSC LNCS FACS Q600SDT. The heating rate was 10&deg;C/min and the test temperature was 20&deg;C ~ 800&deg;C. The results showed that there were three large mass losses in the process of heating, in which the maximum weight loss rate was 66.68% at 220&deg;C ~ 330&deg;C and the decomposition reaction took place in the polysaccharide itself, which indicated that the composition, water content, intermolecular interaction and aggregation behavior of UPOJ-DS were affected by temperature. The surface morphology of UPOJ-DS was observed by environmental scanning electron microscope (ESEM). The results indicated that the polysaccharide molecules were lamellar or clastic, with smooth surface, strong intermolecular interaction and close binding.

Antioxidant Activity <i>in Vitro</i>of Polysaccharide Extracted by Ultrasound with Different Powers from <i>Ophiopogon japonicas</i>

The polysaccharides were extracted by different power ultrasound from Ophiopogon japonicas. The extraction yield and in vitro antioxidant activities including scavenging effect on hydroxyl radical, superoxide anion free radicals and DPPH were investigated. The results showed that with the increase of ultrasonic power, the yield of the polysaccharides decreased first and then increased. The antioxidant activity of polysaccharides increased first and then decreased with the increase of ultrasonic power. When the power was 400 W, the scavenging effect on superoxide anion and DPPH of the polysaccharides was the strongest, and the scavenging ability of hydroxyl radical was the strongest when the power was 560 W. Therefore, different ultrasonic power could affect the extraction yield and antioxidant activity of Ophiopogon japonicas polysaccharide. It will provide theoretical basis and experimental support for the application of ultrasonic extraction on polysaccharides from Ophiopogon japonicas.

Rh掺杂的Cu纳米线催化剂促进5-羟甲基糠醛电催化加氢

生物质是世界上广泛存在的可再生资源,可以转化成高价值燃料和化学品.基于可再生能源产生的电力,将生物质衍生的5-羟甲基糠醛(HMF)电催化转化为2,5-呋喃二甲醇(BHMF)具有重要的研究意义和应用价值.HMF在电转化过程中容易发生二聚反应,从而导致BHMF的选择性较低,产物分离难度大.因此,探索获得高选择性BHMF的高效催化体系极为重要.在此,本文报道了Rh掺杂的Cu纳米线催化剂,其在HMF电还原为BHMF反应中表现出较高的转化率,且有效抑制了二聚反应的发生.动力学实验和原位光谱研究表明,Rh的引入可以有效促进水解离形成活性氢物种,促进5-羟甲基糠醛电催化加氢并抑制其二聚.此催化剂设计策略可以拓展到其他生物质衍生分子的电催化转化过程中.

Efficient improvement of 2.7 μm luminescence of Er^(3+):oxyfluoride glass containing gallium by Yb^(3+) ions codoping

Mid-infrared laser materials with low phonon energy have significant applications. However, the development of available glass systems for high-power laser gain medium have posed a great challenge.Therefore, we investigated the 2.7 μm spectroscopic properties of Er^(3+)/Yb^(3+) -codoped oxyfluoride glass containing gallium, which were prepared by typically melting and quenching methods. The 2.7 μm luminescence properties of the Er^(3+)/Yb^(3+)-codoped oxyfluoride glass containing gallium were recorded by a 980 nm laser diode. The Judde Ofelt parameters, decay curves, emission cross section, energy transfer efficiency and quantum efficiency were calculated. The maximum emission cross section of YbFGa-0.5 is 1.63 × 10^(-20) cm^2 by 980 nm excitation. The energy transfer efficiency is calculated to be77.8% for the YbFGa-0.5 glass around 2700 nm. The quantum efficiency at 1530 nm is 65.6%. The result reveals that the best doping concentration ratio of Er^(3+):Yb^(3+) ions is 1:0.5, and suggests an effective energy transfer from Yb^(3+) to Er^(3+) ions.

Integration of nanoscale light emitters:an efficient ultraviolet and blue random lasing from NaYF_4:Yb/Tm hexagonal nanocrystals

Near infrared light-controlled release of payloads from ultraviolet-sensitive(UV-sensitive) polymer hydrogels or nanocarriers is one of the most promising strategies for biotherapy. Here, we propose the concept of light activation of NaYF_4:20%Yb, 2%Tm nanocrystals(NCs). NaYF_4:20%Yb, 2%Tm NCs are synthesized by a solvothermal method. Effective upconversion luminescence from NaYF_4:20%Yb, 2%Tm NCs excited by a continuous wave(CW) 980 nm laser is obtained. The NaYF_4:20%Yb, 2%Tm NCs are then used as a laser gain medium and sandwiched between Al and quartz reflectors to form laser microcavities. UV and blue upconverted random lasing is obtained from the laser microcavities. Hence, we verify explicitly that the NaYF_4:Yb, Tm NCs support UV and blue upconversion random lasing via a 980 nm nanosecond laser excitation. Our work provides what we believe is a new concept for precision and localized cancer therapy by external light excitation.

Zeolite templated carbon nanodots for broadband ultrafast pulsed fiber laser generation

Carbon nanodots(C-dots) with a uniform size of about 2 nm are synthesized via in situ pyrolysis of n-propylamine that is confined in the nanochannels of zeolite Linde Type A(LTA). The as-synthesized C-dots@LTA composite shows nonlinear optical saturable absorption properties in a broad wavelength band and can be used as saturable absorber(SA) to generate ultrafast pulsed fiber lasers. By inserting a zeolite LTA single crystal hosting C-dots into the fiber laser cavity, mode-locked fiber lasers with long-term operation stability at 1.5 μm and 1 μm are achieved. These results show that the C-dots@LTA are a promising SA material for ultrafast pulsed fiber laser generation in a broad wavelength band. To the best of our knowledge, this is the first demonstration of a C-dots@LTA-based mode-locked fiber laser.

Traditional soliton erbium-doped fiber laser with InSe as saturable absorber

Indium selenide(InSe)is a typical layered metal-chalcogenide semiconductor that has potential for developing ultrafast optoelectronic devices.In this work,InSe-polyvinyl alcohol(InSe-PVA)film is employed as saturable absorber and prepared by mixing InSe nanosheets solution and polyvinyl alcohol solution.The nonlinear absorption properties of the InSe saturable absorber(InSe-SA)are investigated,showing that the nonsaturable absorption and modulation depth are 37.5%and 9.55%,respectively.Traditional soliton lasers are generated in erbium-doped fiber(EDF)laser-employed InSe as a mode-locker.The central wavelength and pulse duration of the traditional soliton pulse are 1568.73 nm and 2.06 ps,respectively,under a repetition rate of 1.731 MHz.The maximum average output power is 16.4 mW at the pump power of 413 mW.To the best of our knowledge,this is the first demonstration of a traditional soliton pulse with InSe as a mode-locker.The experimental results further demonstrate that InSe is an outstanding nonlinear absorption material in ultrafast fiber laser.