胶质液体泡沫的流变性

应用RV-30旋转粘度计和锥板式RS300应力控制流变仪, 采用稳态剪切方法和小振幅振荡剪切对胶质液体泡沫(CLA)体系的流变特性进行了系统分析, 讨论了温度、 相体积比(油相与水相体积比, PVR)和剪切速率对体系流变性质的影响. 稳态剪切实验结果表明, CLA体系表现出非牛顿流体特征, 其流变行为符合Herschel-Bulkley流变模式. 同时, CLA体系表现出剪切稀释特性, 不具有触变性. 粘弹性实验结果表明, 在低PVR(PVR=2~4)条件下, CLA无线性粘弹性区; 当PVR=8时, 表现出一定程度的粘弹性; 温度对体系的流变行为和粘弹性的影响不显著. 通过与高内相乳状液(HIPRE)体系比较, 发现CLA与HIPRE具有相似的流变特性, 这也说明两者在微观结构上具有一定的相似性.     

氧化石墨烯对聚乙烯醇/硼酸水凝胶流变性能的影响

研究了氧化石墨烯(GO)对聚乙烯醇(PVA)/硼酸(borate)水凝胶线性及非线性流变性能的影响。 通过扫描电子显微镜、硼谱核磁共振波谱以及流变研究了水凝胶的流变性能。 结果表明,GO质量浓度在稀溶液区时,GO片层与PVA链间通过硼酸根离子形成了具有弹性活性的缔合点,有效地提高了水凝胶的平台模量、松弛时间和零切粘度;当GO进一步增加到亚浓溶液区,部分的交联剂被GO的团聚体捕获并处于非弹性活性的缔合状态,处于有效缔合状态的交联剂变少,导致平台模量、松弛时间和零切粘度降低。 稳态剪切测试下,样品在剪切增稠区的粘度增加随着GO添加量的增加明显加强,这与剪切场下取向的氧化石墨烯片层参与网络结构的重排有关。     

Mg-Al类水滑石/高岭土分散体系流变振荡现象研究

恒剪切速率(DL)实验发现Mg-Al类水滑石(HTlc)/高岭土(kaolinite)分散体系中存在流变震荡现象,即粘度随时间发生周期性升高和降低的变化.研究了HTlc/kaolinite分散体系的质量比(R)、剪切速率、pH、无机盐及聚合物等因素对振荡现象的影响,发现较高的DL与无机盐含量均可使震荡现象消失.pH值及...     

氧化石墨及石墨烯对阳离子染料的吸附行为研究

利用改进的Hummers-Offeman法合成氧化石墨(GO)和石墨烯,并以其作为吸附剂,选择三种阳离子染料为模型染料,通过测定吸附前后三种阳离子染料溶液的紫外-可见吸收光谱,考察pH、染料初始浓度、温度对吸附效果的影响,研究GO及石墨烯对这三种阳离子染料的吸附行为。结果表明,GO及石墨烯对三种阳离子染料的吸附过程均符合准二级反应动力学方程,且染料结构和pH对其吸附效率也有影响。     

PEG浓度对锂藻土分散液的再凝胶化及屈服行为的影响

通过离子电导率和pH考察了锂藻土自身释放的Na+浓度,说明未经透析或离子交换处理的cw=30mg/mL的锂藻土分散液静置老化后形成的软固体是反应置限团簇聚集(RLCA)的胶体凝胶.通过剪切流变方法研究了聚乙二醇(PEG)浓度cp对锂藻土/PEG分散液体系的线性和非线性黏弹性的影响.小幅振荡剪切(SAOS)频率扫描结果表明,随着cp增加,锂藻土发生"RLCA凝胶-黏弹性液体-排空(Depletion)凝胶"转变,可观察到该体系的再凝胶化行为.稳态剪切和大振幅剪切实验结果表明,锂藻土/PEG分散体系的再凝胶化的非线性流变学行为也有体现.     

氧化石墨烯和石墨烯量子点的两亲性调控及其在Pickering乳液聚合中的应用

氧化石墨烯(Graphene oxide,GO)和石墨烯量子点(Graphene quantum dots,GQDs)与聚合物复合时的分散性较差,用Pickering乳液聚合法可有效解决该问题,这对于提升复合材料的功能性有重要意义。本文归纳了GO和GQDs的制备方法和结构模型,阐述了GO尺寸、离子强度、pH、GO和GQDs结构设计以及单体极性等因素对于GO和GQDs的两亲性调控及其用于Pickering乳液聚合的影响,总结了GO和GQDs用于Pickering乳液聚合的研究进展。GO和GQDs能否作为稳定剂用于Pickering乳液聚合主要与液-液、液-固界面的界面张力大小以及GO和GQDs能否自发地吸附在液-液界面有关,尺寸、离子强度、pH、亲疏水性等均可显著影响液-固界面的界面张力,单体的极性则决定了液-液和液-固界面的界面张力。通过改性、还原等手段对GO和GQDs进行修饰后,可赋予Pickering乳液聚合物导电、导热以及磁响应性等优异性能。最后对GO和GQDs稳定Pickering乳液的研究进行了展望。     

TMAH对TiN纳米粉体分散行为的影响

采用四甲基氢氧化铵(TMAH)作为分散剂,利用沉降法、ξ电位、粒度分析、TEM等研究了TiN纳米粉体在水介质中的分散稳定机制,探讨了pH值和分散剂对纳米颗粒分散行为的影响。结果表明：TiN纳米粉体的分散行为遵循静电稳定机制,pH值对TiN纳米粉体的分散性和稳定性有较大影响,在pH=8处TiN纳米粉体有较好的分散效果。有机阳离子型分散剂TMAH能在TiN纳米颗粒表面形成特征吸附,并通过静电作用和空间位阻作用提高TiN纳米颗粒的分散性。在pH=8、TMAH加入量为0.75wt%的条件下,TiN纳米粉体获得无团聚的最佳分散状态,悬浮液稳定时间可达1个月。     

NiMgAl三元类水滑石的制备研究

在Ni(NO3) 2-Mg(NO3) 2-Al(NO3) 3-NaOH体系中，研究了共沉淀法制备NiMgAl三元类水滑石的合成规律。考察了pH值、Ni/Mg/Al比、沉淀生成温度及水热处理条件对合成NiMgAl-HTLcs的影响，借助XRD 、ICP、 FT-IR对合成样品进行表征。实验结果表明，合成NiMgAl-HTLcs的适宜pH范围为5.5～7.0，Ni/Mg=2.0～4.0，水热处理条件为100 ℃，7 h。通过对合成物热行为研究表明，NiMgAl-HTLcs结构开始破坏温度为300 ℃，经焙烧后可得Ni元素高度分散的复合氧化物。     

温度对磁流变胶复合材料动态力学性能的影响研究与分析

磁流变胶(MRG)是新一代磁流变材料,其有效克服了磁流变液易沉降等缺点。磁流变胶是由软磁颗粒悬浮在凝胶状基质中形成的,其流变特性主要受磁场和温度两个因素控制。本文制备了含有羰基铁粉质量分数为60%的聚氨酯基磁流变胶。系统研究了温度对磁流变胶流变特性的影响。结果表明,温度对磁流变胶的粘弹性有显著影响。测量了频率分别为0.1、5和15 Hz,振幅分别为10%和50%的谐波应变信号在5个温度水平下的迟滞响应,分析了磁流变胶的粘弹性特性,并采用粘弹塑性模型预测了磁流变胶的非线性迟滞特性。分析结果表明,粘弹塑性模型能够准确预测磁流变胶在不同温度下的迟滞特性。     

pH响应型P(HEMA/MAA)纳米微凝胶分散液的凝胶化行为和流变性能

制备了在修复受损组织方面有应用潜能的纳米级聚(甲基丙烯酸羟乙酯/甲基丙烯酸) (P(HEMA/MAA))微凝胶; 采用试管倒转法对不同pH值和浓度的P(HEMA/MAA)微凝胶分散液的凝胶化相转变行为进行了研究; 借助椎板流变仪考察了低浓度和高浓度微凝胶分散液的流变性能, 并对pH触发物理凝胶化相转变机理进行了推测. 结果表明: 在生理pH值环境下, 一定浓度的P(HEMA/MAA)微凝胶分散液可以发生凝胶化相转变形成凝胶态, pH=7时, HEMA/MAA进料摩尔比为8/2的微凝胶分散液凝胶化后得到的凝胶力学性能最佳, 最大弹性模量(G')可达7.58×10³ Pa; P(HEMA/MAA)微凝胶颗粒在不同条件下具有不同的溶胀效果, 导致低浓度分散液的表观粘度发生相应的变化, 并由此推测出微凝胶颗粒的溶胀过程由外及内, 分为三个阶段; 高浓度微凝胶分散液发生凝胶化相转变主要是由颗粒间或颗粒与分散介质间形成的空间静电稳定作用和氢键共同作用引起的.     

高活性氮化碳纳米片的制备策略

Layered graphitic carbon nitride (g-C₃N₄) is a typical polymeric semiconductor with an sp² π-conjugated system having great potential in energy conversion, environmental purification, materials science, etc., owing to its unique physicochemical and electrical properties. However, bulk g-C₃N₄ obtained by calcination suffers from a low specific surface area, rapid charge carrier recombination, and poor dispersion in aqueous solutions, which limit its practical applications. Controlling the size of g-C₃N₄ (e.g., preparing g-C₃N₄ nanosheets) can effectively solve the above problems. Compared with the bulk material, g-C₃N₄ nanosheets have a larger specific surface area, richer active sites, and a larger band gap due to the quantum confinement effect. As g-C₃N₄ has a layered structure with strong in-plane C-N covalent bonds and weak van der Waals forces between the layers, g-C₃N₄ nanosheets can be prepared by exfoliating bulk g-C₃N₄. Alternatively, g-C₃N₄ nanosheets can otherwise be obtained through the anisotropic assembly of organic precursors. Nevertheless, some of these methods have various limitations, such as high energy consumption, are time consuming, and have low yield. Accordingly, developing green and cost-effective exfoliation and preparation strategies for g-C₃N₄ nanosheets is necessary. Herein, the research progress of the exfoliation and preparation strategies (including the thermal oxidation etching process, the ultrasound-assisted route, the chemical exfoliation, the mechanical method, and the template method) for two-dimensional C₃N₄ nanosheets are introduced. Their features are systematically analyzed and the perspectives and challenges in the preparation of g-C₃N₄ nanosheets are discussed. This study emphasizes the following: (1) The preparation method of g-C₃N₄ nanosheets should be properly selected according to the practical application needs. Additionally, various strategies (such as chemical method and ultrasonic method) can be combined to exfoliate nanosheets from bulk g-C₃N₄; (2) More reasonable nano- or even subnanostructured g-C₃N₄ nanosheets should be continuously explored; (3) Novel modification strategies, such as defective engineering, heterojunction construction, and surface functional group regulation, should be introduced to improve the reactivity and selectivity of the g-C₃N₄ nanosheets; (4) The application of in situ characterization techniques (such as in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), electron spin resonance (ESR) spectroscopy, and Raman spectroscopy) should also be strengthened to monitor the detailed catalytic process and investigate the g-C₃N₄ nanosheet structure-efficiency relationship. (5) To gain a deeper understanding of the relationship between the macroscopic properties and the microscopic structure, the combination of theoretical calculations and experimental results should be strengthened, which will be beneficial for exploiting high-quality g-C₃N₄ nanosheets.      

层间共价增强石墨烯材料的构筑、性能与应用

大批量石墨烯可控制备技术的逐渐成熟为实现其宏观组装和应用提供了基础。在众多的组装策略中,调节石墨烯层间的界面相互作用可以直接影响组装体的力学、电学、热学以及渗透等性质,具有重要的意义。石墨烯片层间以共价键连接的层间共价石墨烯材料以其可调的层间距、较强的层间作用力、丰富的功能化、以及可能的原子构型重排等特性,受到了广泛的关注和深入的研究。相比于其他非共价的键合手段,共价连接是一种更为牢固的枢纽。本文中我们将总结讨论层间共价石墨烯材料的构筑方法、性能以及应用。在构筑方法中,依据石墨烯本身的制备方法分为氧化还原法以及化学气相沉积法,而在氧化还原法中,以其宏观材料的形貌分为纸状和纤维状来讨论。接着,我们重点介绍了层间共价对其力学和电学性能的影响,并概述了此类宏观组装体材料的应用。层间共价石墨烯材料继承了石墨烯自身优异的特性,同时也具有宏观组装所赋予的性能,有望在多个领域得到广泛的应用。     

Mn0.2Cd0.8S@CoAl LDH S-型异质结构建及其光催化析氢性能研究

构建高效、稳定的异质结光催化剂体系是实现太阳能驱动分解水制氢的有效途径。本研究通过物理混合法将Mn_0.2Cd_0.8S纳米棒与CoAl LDH纳米片进行耦合,成功制备出一种新型的Mn_0.2Cd_0.8S@CoAl LDH (MCCA) S型异质结光催化剂。光致发光光谱和光电流测试结果表明,该异质结在内建电场的作用下可以有效地加快Mn_0.2Cd_0.8S和CoAl LDH界面间光生载流子的分离和电子转移。关键的是,CoAl LDH的引入有效地抑制了光生电子与空穴的复合,从而提高了Mn_0.2Cd_0.8S的光催化产氢活性。最佳CoAl LDH负载量的MCCA-3在5 h内的产氢量为1177.9 μmol。与单独使用纯Mn_0.2Cd_0.8S纳米棒和CoAl LDH纳米片相比,这是一个显著的改进。本研究为合理设计用于光催化制氢的S型异质结光催化剂提供了一条简单有效的途径。     

超级电容器用石墨烯薄膜：制备、基元结构及表面调控

石墨烯薄膜是一种以石墨烯纳米片为基元结构的宏观体,通过合理的结构设计和表面修饰使其具有优异的电学、力学和热学性能,将在电化学储能、电子器件、健康和环保等领域具有潜在的应用。本文主要综述了从石墨烯基元调控到二维宏观膜组装以及石墨烯薄膜在超级电容器应用中的研究进展。主要介绍了石墨烯薄膜的简易制备方法,并详细介绍了通过对石墨烯基元的结构调控和表面修饰来优化石墨烯薄膜电化学性能的两大策略,最后对石墨烯薄膜应用所面临的挑战和未来的发展进行了总结与展望。     

银纳米粒子修饰的二维金属-有机框架纳米片用于光热增强银离子释放抗菌

近年来,二维(2D)金属-有机框架(MOF)纳米复合材料被广泛的应用于生物医学领域,尤其是在抗菌方面。在此,我们通过光照诱导还银离子成功在二维MOF纳米片上生长银纳米粒子,得到了一种银纳米粒子(Ag NPs)修饰的二维Zr-Fc-MOF (MOF-Ag)纳米片,并将其用于光热增强Ag⁺释放抗菌治疗。通过水热法和超声处理合成MOF纳米片,然后通过原位光辐照诱导还原在MOF纳米片上生长Ag NPs。系列表征结果表明Ag NPs成功负载到MOF纳米片上。聚乙烯吡咯烷酮(PVP)的修饰不仅可以增强MOF-Ag在溶液中的稳定性,还可以增强它的生物相容性。在近红外激光(NIR)照射下,MOF纳米片可以在短时间升温,而温度的升高可以加速Ag NPs在溶液中氧化为银离子。通过细菌生长曲线、菌落相对数和细菌形态变化等实验表明PVP@MOF-Ag纳米片具有优异的广谱杀菌性能。此外,2D MOF纳米片良好的光热性能不仅可以增强Ag⁺的释放,还可以增强细胞膜的通透性,随后进入细菌中的Ag⁺可以诱导内源性活性氧的产生,从而引发细菌的氧化应激,实现高效抗菌。基于良好的体外抗菌性能,进一步将PVP@MOF-Ag纳米片用于小鼠伤口愈合,在此期间PVP@MOF-Ag纳米片表现出良好的治疗效果和生物安全性。我们的研究结果表明,PVP@MOF-Ag纳米片可以作为光热增强Ag⁺释放抗菌治疗和伤口愈合的有效平台。     

缺陷工程调控石墨相氮化碳及其光催化空气净化应用进展

Since the pioneering work on polychlorinated biphenyl photodegradation by Carey in 1976, photocatalytic technology has emerged as a promising and sustainable strategy to overcome the significant challenges posed by energy crisis and environmental pollution. In photocatalysis, sunlight, which is an inexhaustible source of energy, is utilized to generate strongly active species on the surface of the photocatalyst for triggering photo-redox reactions toward the successful removal of environmental pollutants, or for water splitting. The photocatalytic performance is related to the photoabsorption, photoinduced carrier separation, and redox ability of the semiconductor employed as the photocatalyst. Apart from traditional and noble metal oxide semiconductors such as P25, bismuth-based compounds, and Pt-based compounds, 2D g-C₃N₄ is now identified to have enormous potential in photocatalysis owing to the special π-π conjugated bond in its structure. However, some inherent drawbacks of the conventional g-C₃N₄, including the insufficient visible-light absorption ability, fast recombination of photogenerated electron-hole pairs, and low quantum efficiency, decrease its photocatalytic activity and limit its application. To date, various strategies such as heterojunction fabrication, special morphology design, and element doping have been adopted to tune the physicochemical properties of g-C₃N₄. Recent studies have highlighted the potential of defect engineering for boosting the light harvesting, charge separation, and adsorption efficiency of g-C₃N₄ by tailoring the local surface microstructure, electronic structure, and carrier concentration. In this review, we summarize cutting-edge achievements related to g-C₃N₄ modified with classified non-external-caused defects (carbon vacancies, nitrogen vacancies, etc.) and external-caused defects (doping and functionalization) for optimizing the photocatalytic performance in water splitting, removal of contaminants in the gas phase and wastewater, nitrogen fixation, etc. The distinctive roles of various defects in the g-C₃N₄ skeleton in the photocatalytic process are also summarized. Moreover, the practical application of 2D g-C₃N₄ in air pollution control is highlighted. Finally, the ongoing challenges and perspectives of defective g-C₃N₄ are presented. The overarching aim of this article is to provide a useful scaffold for future research and application studies on defect-modulated g-C₃N₄.      

钠离子电池电极材料的设计策略——固态离子学视角

钠离子电池是目前最有前景及可行性的新兴储能候选体系。对于钠离子电池而言，如何实现其电极材料的理性设计及构筑，是重要的科学问题。本文立足于钠离子/电子输运这一核心问题，从固态离子学视角探讨钠离子电池电极材料的设计策略。首先，对于体相电极材料，输运特性的明晰、调控以及缺陷化学模型的建立，是传统电极材料开发的关键。其次，对于纳米电极材料，随着尺寸的减小，电极材料的热力学性质、动力学特性以及钠离子微观储输机制都会发生相应变化，因此从纳米离子学视角，以尺寸效应调控电极材料具有重要的科学价值及现实意义。最后，无论对于体相材料还是纳米材料，从材料的本征输运特性出发，通过电化学电路的设计和构筑来优化电极动力学，可以为钠电电极材料的理性设计及可控制备提供理论指导。我们相信，通过本文系统地对钠离子电池电极材料设计策略的梳理，必将对钠离子电池的开发，提供有意义的指导，并为最终的产业化打下良好的基础。     

Understanding Self-assembly,Colloidal Behavior and Rheological Properties of Graphene Derivatives for High-performance Supercapacitor Fabrication

Graphene derivatives, such as graphene oxide(GO) and reduced graphene oxide(RGO), have been widely used as promising twodimensional nanoscale building blocks due to their fascinating properties, cost-effective production, and good processability. Understanding the intrinsic self-assembling, colloidal, and rheological features of graphene derivatives is of critical importance to establish the formation-structureproperty relationship of graphene-based materials. This article reviews recent progresses in our studies of these interesting properties of graphene derivatives for developing high performance supercapacitors. The content is organized to include characteristics of the dispersions of graphene derivatives, self-assembly of nanosheets from liquid medium, colloidal behavior, rheological properties of the dispersions, processing methods based on the properties, and performance of the fabricated supercapacitors. GO and RGO nanosheets are proved to form different types of assembled structures with unique morphologies, such as ultrathin layer-by-layer films, porous aggregates, and nanoscrolls. The unique rheological properties of GO dispersions and hydrogels, feasible for both the traditional wet-processing and newly-developed technology like three-dimensional printing, are highlighted for their potential in structural manipulation and scalable fabrication of graphene-based devices. The research devoted to up-grading the performance of supercapacitors is presented in some details, which could be applicable for fabricating other graphene-based energy storage devices. Some challenges and perspectives in our point of view are given in the last part of this feature article.     

基于γ-石墨炔分子磁隧道结对称性依赖的输运性质

利用非平衡格林函数和密度泛函理论,研究不同类型γ-石墨炔分子磁隧道结(MMTJ)自旋极化输运特性的影响。磁隧道结以铁磁性的锯齿形石墨烯纳米带作电极。随着纳米带宽度变化,考虑γ-石墨炔的两种接触点,我们构造了8种有代表性的且具有不同对称性的隧道结。通过计算我们发现,对称性对磁隧道结的自旋输运起决定性作用。对于偶数碳链的锯齿形石墨烯纳米带,石墨炔的接触点位居于正中,这种结构的自旋极化输运性质远优于其它结构。比如在非常宽的偏压范围内都能达到100%的自旋极化率,且隧穿磁阻(TMR)高达3.7 × 10⁵,这表明该结构在自旋滤波器和自旋阀器件方面的应用潜力最大。与之形成对比的是,当耦合位置偏离锯齿形石墨烯纳米带的中心时,输运性质迅速变为普通电输运,相应的巨磁阻效应比最优对称结构约小4个数量级。     

仿鲍鱼壳石墨烯多功能纳米复合材料

石墨烯具有力学性能高、电导率优异等特点,然而单层石墨烯纳米片在组装成为宏观纳米复合材料的过程中,往往会出现片层团聚、界面作用弱、无规取向等问题,导致宏观石墨烯纳米复合材料性能远低于单片石墨烯。因此,如何将微观石墨烯纳米片层的高性能在宏观纳米复合材料中体现出来,是目前研究的热点和难点。本专论结合目前石墨烯纳米复合材料的研究现状,简要讨论了受天然鲍鱼壳的“砖-泥”结构的启发,仿生构筑高性能石墨烯纳米复合材料的最新研究进展。并对本课题组在仿鲍鱼壳石墨烯多功能纳米复合材料领域近年来的工作进行介绍,包括石墨烯纤维、薄膜和块材等多种宏观石墨烯纳米复合材料,系统总结构筑仿鲍鱼壳结构和反鲍鱼壳结构两种策略,在一定程度上解决了石墨烯在组装过程中的科学问题。同时,详细阐述了仿鲍鱼壳石墨烯多功能纳米复合材料的增强增韧机制和功能化策略,分析了今后研究工作中可能遇到的问题,并展望了未来的发展趋势。