参杂缺陷石墨烯的高分子复合材料导热特性分子动力学模拟

Polymers are widely used advanced materials composed of macromolecular chains, which can be found in materials used in our daily life. Polymer materials have been employed in many energy and electronic applications such as energy harvesting devices, energy storage devices, light emitting and sensing devices, and flexible energy and electronic devices. The microscopic morphologies and electrical properties of the polymer materials can be tuned by molecular engineering, which could improve the device performances in terms of both the energy conversion efficiency and stability. Traditional polymers are usually considered to be thermal insulators owing to their amorphous molecular chains. Graphene-based polymeric materials have garnered significant attention due to the excellent thermal conductivity of graphene. Advanced polymeric composites with high thermal conductivity exhibit great potential in many applications. Therefore, research on the thermal transport behaviors in graphene-based nanocomposites becomes critical. Vacancy defects in graphene are commonly observed during its fabrication. In this work, the effects of vacancy defects in graphene on thermal transport properties of the graphene-polyethylene nanocomposite are comprehensively investigated using molecular dynamics (MD) simulation. Based on the non-equilibrium molecular dynamics (NEMD) method, the interfacial thermal conductance and the overall thermal conductance of the nanocomposite are taken into consideration simultaneously. It is found that vacancy defects in graphene facilitate the interfacial thermal conductance between graphene and polyethylene. By removing various proportions of carbon atoms in pristine graphene, the density of vacancy defects varies from 0% to 20% and the interfacial thermal conductance increases from 75.6 MW·m⁻²·K⁻¹ to 85.9 MW·m⁻²·K⁻¹. The distinct enhancement in the interfacial thermal transport is attributed to the enhanced thermal coupling between graphene and polyethylene. A higher number of broken sp² bonds in the defective graphene lead to a decrease in the structure rigidity with more low-frequency (< 15 THz) phonons. The improved overlap of vibrational density states between graphene and polyethylene at a low frequency results in better interfacial thermal conductance. Moreover, the increase in the interfacial thermal conductance induced by vacancy defects have a significant effect on the overall thermal conductance (from 40.8 MW·m⁻²·K⁻¹ to 45.6 MW·m⁻²·K⁻¹). In addition, when filled with the graphene layer, the local density of polyethylene increases on both sides of the graphene. The concentrated layers provide more aligned molecular arrangement, which result in better thermal conductance in polyethylene. Further, the higher local density of the polymer near the interface provides more atoms for interaction with the graphene, which leads to stronger effective interactions. The relative concentration is insensitive to the density of vacancy defects. The reported results on the thermal transport behavior of graphene-polyethylene composites provide reasonable guidance for using graphene as fillers to tune the thermal conduction of polymeric composites.     

非简谐振动对SiC类石墨烯热输运性质的影响

考虑到原子的非简谐振动,应用固体物理理论和方法,计算了SiC类石墨烯的简谐系数和非简谐系数,得到它的德拜温度、热容量和热导率等随温度的变化规律,探讨了原子非简谐振动对它的热输运性质的影响.结果表明:SiC类石墨烯的德拜温度随温度的升高而在117-126 K之间线性增大,定容比热随温度升高而非线性增大,热导率随温度升高而非线性减小,温度较低时变化较快,而温度较高时变化较慢,并随着温度升高而趋于常量;考虑到非简谐振动后,SiC类石墨烯的德拜温度、定容比热和热导率的值分别大于、小于和大于简谐近似的相应值,温度愈高,其差值愈大,即温度愈高,非简谐效应的影响愈显著;二维平面状的SiC类石墨烯的定容比热和热导率随温度的变化规律,与三维块状SiC晶体总体趋势相同,只是具体数值不同.     

石墨烯-聚苯乙烯磺酸盐-铂复合物的制备及在多巴胺检测中的应用

在微波辅助条件下,还原石墨烯氧化物和氯铂酸,一步反应制备了石墨烯-聚苯乙烯磺酸盐-铂纳米复合物。利用透射电镜技术,X射线衍射技术和拉曼光谱技术表征了该纳米复合物的形貌和结构。研究了多巴胺在此纳米复合物上的电化学行为,并探讨了计时安培法检测多巴胺的可行性。结果表明,检测多巴胺的线性范围为2.0×10"7～4.0×10"3mol/L,检出限为4.0×10"8mol/L(信噪比S/N=3)。此外,此纳米复合物修饰电极被用于检测人血清和尿液样品中的多巴胺。     

氧化石墨烯/铁氰化铈修饰玻碳电极同时测定扑热息痛和咖啡因

采用滴涂法和电沉积法制备了氧化石墨烯/铁氰化铈(CeFe(CN)6)纳米复合膜修饰玻碳电极。用扫描电镜对氧化石墨烯和氧化石墨烯/CeFe(CN)6纳米复合膜进行了表征。分别用循环伏安法和差分脉冲伏安法研究了扑热息痛和咖啡因在修饰电极上的电化学行为。结果表明,在0.1 mol/L醋酸盐缓冲溶液(pH5.0)中,扑热息痛和咖啡因在此修饰电极上具有良好的电化学行为,扑热息痛和咖啡因分别在1.0×10-7～6.0×10-5mol/L和1.0×10-6～1.3×10-4mol/L浓度范围内与电化学响应信号呈良好的线性关系,相关系数分别为0.990和0.992;信噪比为3时,扑热息痛和咖啡因检出限分别为5.0×10-8mol/L和5.2×10-7mol/L。将本方法用于人尿样品分析,回收率为96.1%～105.4%。     

石墨烯固相萃取测定水中稠环芳烃

建立了石墨烯固相萃取柱萃取和高效液相色谱法检测8种稠环芳烃的方法。采用紫外检测器进行定性和定量分析。对包括吸附剂的种类、洗脱剂的种类和用量、样品溶液的pH和样品体积等实验参数进行了详细优化。在优化条件下,8种稠环芳烃在0.0200～150μg/L浓度范围内与峰面积呈良好的线性关系,相关系数为0.990～0.996。信噪比为3时,稠环芳烃的检出限为0.0020～0.080μg/L。方法的精密度为1.30%～4.65%。将该方法用于环境水样分析,回收率为82.50%～106.5%。     

苏丹红Ⅰ在锰卟啉/氧化石墨烯-多壁碳纳米管修饰电极上的电化学行为及测定

制备了水溶性良好、带负电的氧化石墨烯-多壁碳纳米管(GO-MWNTs)纳米复合材料,用带正电的锰卟啉(MnTMPy)自组装到GO-MWNTs表面,构建了MnTMPy/GO-MWNTs/GC修饰电极。利用电化学阻抗谱对所制备的修饰电极进行表征,利用循环伏安法研究了苏丹红Ⅰ在电极上的电化学行为。结果表明,在50nmol/L～15μmol/L浓度范围内,苏丹红Ⅰ的差分脉冲伏安响应电流与其浓度呈现良好的线性关系,相关系数为0.996,检出限为20nmol/L。该方法可简便、快捷、灵敏地检测辣椒粉中苏丹红Ⅰ的含量。