纳米片组装钴铁氧体微球的制备及其性能

采用超声溶剂热法,成功地制备了由片状钴铁氧体(CoFe₂O₄)自组装的微球。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)对样品的结构和形貌进行了表征。结果表明,所制备的CoFe₂O₄微球为立方晶相结构,其粒径分布在20～30μm之间,是由二维纳米片组装而成。用振动样品磁强计(VSM)和网络矢量分析仪分别对纳米片组装微球样品及自制的CoFe₂O₄粉体的室温磁性和吸波性能进行了测试,结果显示,纳米片组装微球比自制粉体的磁性和微波吸收性能更好,其饱和磁化强度和矫顽力分别达到76.15emu/g和227.89Oe。此外,纳米片组装CoFe₂O₄微球在频率为6000MHz波段附近有一个明显的吸收峰,回损值大于-18dB,并有继续增大的趋势。说明产物的结构和形貌对其磁性和吸波性都有很大影响。     

石墨烯纳米片-乙二醇纳米流体光热转化特性研究

纳米流体应用于太阳能集热器是太阳能光热转化的重要突破,石墨烯纳米材料在可见光和近红外区域具有较好的吸收特性,实验基于Hummer法制备了石墨烯纳米片材料,对其进行表征。并配制了不同质量分数石墨烯纳米片-乙二醇纳米流体,将其在太阳能模拟器下进行闷晒实验,计算石墨烯纳米片的光热转化效率,并以基液作对比分析其光热转化特性。结果表明纳米流体溶液的光热转化效率随着其浓度的增加而提高,在达到临界值后光热转化效率不再提高反而降低。其中浓度为0.0007%(质量)时的石墨烯纳米片纳米流体溶液温度增加最高,为65.56℃,光热转化效率达到最高约为76.35%,较乙二醇效率升高49.65%。表明石墨烯纳米片具有良好的光学特性,在太阳能集热器中具有较好的应用前景。     

应用乳化液膜系统合成CdS与ZnS纳米复合微粒

利用双W/O型乳化液膜系统合成CdS及ZnS纳米微粒,并以W/O/W型乳化液膜系统合成合金型CdxZn1-xS、混合型CdSZnSmixture与核壳型CdScoreZnSshell(或ZnSooreCdSshell)的纳米复合微粒.XRD分析结果显示,CdS会随着界面活性剂Span80浓度增加而使晶型从立方体转变成六方体,而ZnS则没有晶型转变的现象发生.UV/VIS分析光学性质显示CdS及ZnS纳米微粒随着Span80浓度增加,吸收峰的强度均会有变强的趋势.其中CdS吸收波峰会随着Span80浓度增加而往短波长位移,而ZnS吸收波峰的位置不受Span80浓度影响.另外UV/VIS分析结果也显示,CdS纳米微粒的吸收波峰约在459 nm,ZnS纳米微粒的吸收波峰约在321 nm,而Cd0.5Zn0.5S与CdSZnSmixture纳米复合微粒会同时出现CdS与ZnS的吸收波峰.至于CdScoreZnSshell纳米复合微粒则仅会出现外层ZnS的吸收波峰;同样,ZnScoreCdSshell纳米复合微粒只会出现外层CdS的吸收波峰.另外,根据PL(λex=350 nm)的分析结果显示,CdS纳米微粒的放射波峰约在625 nm,ZnS纳米微粒的放射波峰约在537 nm,Cd0.5Zn0.5S纳米复合微粒则在537,572与625 nm三处同时出现明显的放射波峰,而CdSZnSmixture纳米复合微粒则在599 nm处出现不同于CdS与ZnS特征的放射波峰,至于CdScoreZnSshell或ZnScoreCdSshell纳米复合微粒则只会出现外层ZnS或CdS的放射波峰.     

DSC法研究纳米SiO2/MC尼龙6原位复合材料的多重熔融行为

借助差示扫描量热仪(DSC)研究纳米SiO2/MC尼龙6原位复合材料等温结晶后的多重熔融行为.结果表明:复合材料的熔融行为呈现三重熔融峰,分别对应于等温结晶过程形成的小晶片、主要结晶组分及完善性较差的组分再结晶和再组合形成较为完善结晶组分的熔融.在高温下结晶,纳米粒子含量的增加提高了体系再结晶、再组合程度;在低温下结晶,当纳米粒子含量较低时,再结晶、再组合程度相对于纯MC尼龙6有所降低,进一步增加纳米粒子的含量,再结晶、再组合的程度又逐步提高.     

贵金属纳米棒异质结结构的光学特性研究

文章应用离散偶极子近似的方法计算了金银两种贵金属材料形成的纳米棒异质结结构的表面等离子体共振引起的消光光谱及其近场电场分布。研究表明当保持纳米棒的总长度不变,增加银纳米棒的长度,纳米棒异质结结构的等离子体共振消光峰会发生蓝移。当改变银纳米棒的长度时,引起金银纳米棒之间的耦合方式改变,使得共振能级杂化出现新的共振峰。因此,通过改变异质结的结构参数对其消光谱的影响来调整表面等离子体共振峰的位置,以满足纳米棒在等离子体光子学方面的应用。     

两亲Janus纳米片的制备及胶体与界面性质研究进展

该文首先综述了两亲Janus纳米片制备方法的研究进展，包括界面保护法、乳液界面自组装溶胶-凝胶法、模板辅助溶胶-凝胶法以及嵌段共聚物自组装法。接着，系统介绍了两亲Janus纳米片在水溶液中的胶体特性及其在油水体系中的界面特性。最后，简要介绍了两亲Janus纳米片的应用领域，并对未来两亲Janus纳米片制备方法和胶体与界面特性的研究方向进行了展望。     

单体Ag纳米流体强化氨水鼓泡吸收特性

为探讨纳米流体对氨水鼓泡吸收传热传质特性的影响,利用自行设计的实验系统进行了不同浓度单体Ag纳米流体基液下的氨水鼓泡吸收实验。实验表明:纳米流体浓度与初始氨水浓度是影响鼓泡吸收过程中传热与传质的关键因素。当单体Ag纳米流体在浓度0.005%～0.020%内、基液中没有添加纳米流体时,5min内随着时间推移,吸收器内溶液温度明显高于添加有纳米流体的情况;氨水鼓泡吸收传质过程中,有效吸收比均大于1.0,随着氨水浓度上升,各浓度纳米流体基液下吸收率逐步减小,有效吸收比逐渐增大,且吸收率和有效吸收比均随着纳米浓度增大而上升,当氨水浓度为20%且纳米流体浓度为0.020%时,单体Ag纳米流体强化氨水鼓泡吸收有效吸收比达到最大值1.55。对实验现象和相关结论进行了可能的机理解释。     

ZnS纳米微粒的光谱特性研究

研究了ZnS纳米微粒的光谱特性,结果表明:在400～4000cm-1基本无吸收峰,表明ZnS纳米微粒具有热红外透明性;激发波长为290nm时,荧光发射峰在350nm.随着表面活性剂OP的增加,荧光强度不断变弱,表现出明显的纳米尺寸量子化效应.     

不同pH下GO-ATP纳米复合材料的分析与表征

通过超声波+磁力搅拌法,制备了GO-ATP纳米复合材料,采用X射线衍射(XRD)仪、傅里叶变换红外光谱(FTIR)仪、扫描电子显微镜(SEM)等手段,研究不同p H制备条件对GO-ATP纳米复合材料结构的影响。结果表明,p H值对GO-ATP纳米复合材料形成过程影响明显,极性环境不利于复合材料的形成;当p H为4~10时,随p H增大,GO-ATP纳米复合材料层间距增大,且含氧官能团峰渐强,当p H=10时,层间距最大,SEM显示ATP插层于GO片层中,有效抑制了GO的团聚。     

不同pH下GO-ATP纳米复合材料的分析与表征

通过超声波+磁力搅拌法,制备了GO-ATP纳米复合材料,采用X射线衍射(XRD)仪、傅里叶变换红外光谱(FTIR)仪、扫描电子显微镜(SEM)等手段,研究不同p H制备条件对GO-ATP纳米复合材料结构的影响。结果表明,p H值对GO-ATP纳米复合材料形成过程影响明显,极性环境不利于复合材料的形成;当p H为4¹0时,随p H增大,GO-ATP纳米复合材料层间距增大,且含氧官能团峰渐强,当p H=10时,层间距最大,SEM显示ATP插层于GO片层中,有效抑制了GO的团聚。     

Nanofluid optical property characterization: towards efficient direct absorption solar collectors

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10^-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.     

Experimental investigation on low concentration nanofluids with Fresnel lens and evacuated tubes for solar applications

Optical and thermo-physical properties of the nanofluids play a major role in the absorption of solar energy. In the present study, photo-thermal energy conversion of low concentration Al₂O₃/Deionised water (DI) water and CuO/DI water nanofluids in solar thermal collector is experimentally investigated. Properties of 50,100,150, and 200 ppm concentrations of nanofluids are reported. The absorbance results in the visible range indicate that CuO nanofluid of 200 ppm concentration is nearly three times higher compared to Al₂O₃ nanofluid. The extinction coefficient, optical energy band gap, and photoluminescence obtained from the absorbance data are also reported. Surfactant free nanofluids are used, and the thermal conductivity measurements show a negligible enhancement for both the nanofluids. Maximum receiver temperatures of 89 and 72°C are found with CuO and Al₂O₃ nanofluids, respectively, for the maximum concentration. A maximum receiver efficiency of 34.89% is obtained for CuO nanofluids.     

Janus graphene oxide nanosheets prepared via Pickering emulsion template

Janus graphene oxide (GO) nanosheets functionalized by amino-containing chemicals were prepared via Pickering emulsion template. A wax-in-water Pickering emulsion was used to mask one side of GO nanosheets in order to achieve asymmetric chemical functionalization. Janus particles were obtained by removing the oil phase. The successful reaction of epoxy groups on the surface of GO with amino-containing chemicals was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The asymmetric surface structure of Janus GO nanosheets was detected by atomic force microscope (AFM) and X-ray diffraction (XRD). The efficient stabilization of an oil-in-water Pickering emulsion by Janus GO was proved. Polymer microspheres fabricated by using Janus GO as Pickering stabilizer had a more hydrophilic surface compared with those stabilized by symmetrically modified GO.     

磁性纳米片的制备及功能化应用研究进展

磁性纳米片因其独特的性质已在磁共振成像、微波吸收、催化剂、电池、吸附净化等领域受到了广泛关注。该文归纳了磁性纳米片的制备方法以及功能化应用方向，阐述了不同制备方法对磁性纳米片的形貌、大小以及厚度的影响。归纳了磁性纳米片的合成机理以及性能调控因素，为其规模化制备提供理论支持。此外，着重介绍了磁性纳米片在各个领域的功能化应用进展，总结出磁性纳米片基本性质及功能化改性后的作用行为对进一步应用的意义。最后，对磁性纳米片研究中亟待解决的问题以及未来的研究方向进行了展望。     

Construction,structure and photocatalysis of janus nanofiber modified by g-C3N4 nanosheets heterostructure photocatalysts

The construction of photocatalyst with gradient band structure is guided by the principle of band gap engineering. Rational structural design is advanced and applied to construct a new-typed peculiarly structural and functional carbon-based [TiO₂/C]//[Bi₂WO₆/C] Janus nanofiber modified by g-C₃N₄ nanosheets heterostructure photocatalyst (denoted as TB-JgHP). The flexible carbon-based [TiO₂/C]//[Bi₂WO₆/C] Janus nanofiber with one side responding to ultraviolet light and the other capturing visible light is fabricated by conjugate electrospinning, and then g-C₃N₄ nanosheets are uniformly grown in-situ on the surface of the Janus nanofibers by using gas-solid reaction via gasification of urea. The optimized TB-JgHP possesses remarkable hydrogen evolution efficiency (17.48 mmol h⁻¹ g⁻¹) and methylene blue degradation rate (99.2%) under simulated sunlight illumination for 100 min, demonstrating prominent dual-functional characteristics. The enhanced photocatalytic performance benefits from the unique Janus structure as well as the synergistic effects among the triple heterostructures of TiO₂ and Bi₂WO₆, g-C₃N₄ and TiO₂, g-C₃N₄ and Bi₂WO₆. The formation of gradient band structure among heterostructures is more conducive to the multi-step separation of photo-induced electron-hole pairs and more effective absorption of light. Further, flexible self-standing carbon-based photocatalysts not only have outstanding electron transport performance, but also are easy to separate from solution with preeminent recyclable stability. Based on a series of characterization techniques, it is further proved that TB-JgHP has higher carrier separation efficiency than the counterpart contrast samples. The formation mechanism of TB-JgHP is proposed, and the construction technique is established. The design philosophy and construction technique presented in this work pave a new avenue for research and development of other heterostructure photocatalysts.     

Solar energy conversion with tunable plasmonic nanostructures for thermoelectric devices

The photothermal effect in localized surface plasmon resonance (LSPR) should be fully utilized when integrating plasmonics into solar technologies for improved light absorption. In this communication, we demonstrate that the photothermal effect of silver nanostructures can provide a heat source for thermoelectric devices for the first time. The plasmonic band of silver nanostructures can be facilely manoeuvred by tailoring their shapes, enabling them to interact with photons in different spectral ranges for the efficient utilization of solar light. It is anticipated that this concept can be extended to design a photovoltaic-thermoelectric tandem cell structure with plasmonics as mediation for light harvesting.     

Photocatalytic degradation of PCP-Na over BiOI nanosheets under simulated sunlight irradiation

The photocatalytic removal of sodium pentachlorophenate (PCP-Na) over BiOI nanosheets under simulated solar light irradiation has been studied. BiOI nanosheets exhibited an excellent photocatalytic activity to remove PCP-Na from aqueous solution driven by simulated light. The photocatalytic reaction over BiOI nanosheets followed the pseudo first-order reaction, owning to its weak adsorption behavior to PCP-Na molecules and low initial PCP-Na concentration. Finally, the photocatalytic mechanism was investigated initially on the basis of the experimental result and band edge potential analysis.     

Self-assembly of MXene-decorated stearic acid/ionic liquid phase change material emulsion for effective photo-thermal conversion and storage

As a typical latent functionally thermal fluid with large energy storage capacity and good liquidity, phase change material emulsion (PCME) plays a broad and important role in solar energy utilization. However, the high-temperature instability and supercooling problems of PCME limit its practical application. The ionic liquid (IL)-based PCME allows for the possibility of being used as a heat transfer fluid (HTF) under more extreme temperature conditions. In this work, stearic acid (SA)/IL PCME, prepared by one-step self-assembly of MXene nanosheets at the SA/IL interface, can effectively absorb and convert solar energy into thermal energy. Furthermore, MXene-decorated SA/IL PCMEs have good high-temperature stability, little supercooling degree (0.9–3.1 °C), and large energy storage capacity. The maximum apparent specific heat capacity and average absorbance of the MXene-decorated SA/IL PCME are 4.5 and 303.1 times higher than those of IL, respectively. Under 2 sun irradiation, the 0.05–20 wt% MXene-decorated SA/IL PCME achieves high photo-thermal conversion efficiencies (91.3% at 68.9 °C, 39.4% at 115.1 °C) due to its large energy storage capacity and excellent optical absorption property. The simple interfacial self-assembly provides a promising strategy to prepare high-performance SA/IL PCME used as a novel HTF for medium-temperature solar energy utilization systems.