氧化石墨烯的制备及低温还原研究

用化学氧化法制备氧化石墨烯,并用一种新型的低温化学还原方法将其还原。用红外光谱、拉曼光谱、X射线衍射、X射线光电子能谱、扫描电镜、原子力显微镜等多种手段表征氧化石墨烯和还原氧化石墨烯的结构与形貌。结果表明,即使在低温条件下,壳聚糖依然可以还原氧化石墨烯,从而预示,在低温条件下,能够在同一环境下实现氧化石墨烯的还原和石墨烯的应用。     

氧化石墨烯的绿色还原研究进展

从还原剂和还原方法这两个方面综述了近些年来绿色还原氧化石墨烯的若干方法,对一些天然的还原剂的应用及结果进行了描述,分析了这些方法的优缺点并给出了部分反应可能的机理,还对一些新型的环境友好型的还原方法也进行了评价。同时,对于还原氧化石墨烯的研究提供了新的思路和展望。     

石墨烯的氧化还原法制备及结构表征

采用改进的Hummers法对天然鳞片石墨进行氧化处理制备氧化石墨,经超声分散,然后在水合肼的作用下加热还原制备了在水相条件下稳定分散的石墨烯。用红外光谱、拉曼光谱、扫描探针显微镜和ζ电位仪对样品进行了结构、谱学、形貌和ζ电位分析。结果表明,石墨被氧化后形成以C=O、C-OH、-COOH和C-O-C等官能团形式的共价键型石墨层间化合物;还原氧化石墨后形成的石墨烯表面的官能团与石墨的相似;氧化石墨烯和石墨烯在碱性条件下可形成稳定的悬浮液;氧化石墨烯和石墨烯薄片厚度为1.0nm左右。考察并讨论了还原过程中水合肼用量,体系反应温度、反应时间和pH值对石墨烯还原程度和稳定性的影响,水合肼用量和反应时间是影响石墨烯还原程度的主要因素;pH值对石墨烯稳定性影响较大。     

正丁基氯化镁还原氧化石墨烯的表征

采用元素分析、红外光谱(FTIR)、X射线光电子能谱(XPS)、拉曼光谱、X射线衍射(XRD)、固体¹³C核磁共振波谱(¹³C MAS NMR)、热失重分析(TGA)、导电率测试以及原子力显微镜(AFM)等手段对正丁基氯化镁还原的氧化石墨烯进行了系统的表征. 结果表明, 正丁基氯化镁可以有效还原氧化石墨烯, 随着其用量的增加, 氧化石墨烯还原程度增加, 碳/氧摩尔比升高, 片层间距减小, 热稳定性增强, 导电率增大(可达3.6×10² S/m). 还原后部分氧化石墨烯片层发生聚集.     

氢溴酸可控还原氧化石墨烯及氢气气敏性能

采用改进的Hummers法对石墨进行氧化处理制备大片径氧化石墨,经超声分散获得一定浓度的氧化石墨烯样品,并将其与氢溴酸水浴加热反应进行化学还原处理,改变氢溴酸的添加量,从而获得不同还原程度的氧化石墨烯样品。用AFM、 XRD、FT-IR、XPS及气敏测试仪对样品薄膜厚度、结构、官能团等变化规律及氢气气敏特性进行测试表征与分析。      

石墨烯薄膜的光化学还原制备与表征

采用光化学还原方法制备了图案化的石墨烯薄膜.研究了光还原氧化石墨烯薄膜(PRGO)的热稳定性和发光性质.热重分析(TGA)结果表明,光化学还原主要引起氧化石墨烯(GO)氧化基团的减少,而对GO内水含量影响较小;发光(PL)测试结果表明,不同激发条件下,PRGO的发光与GO相比表现出了不同的变化规律:在波长514 nm的光激发下,PRGO的发光强度比GO明显降低,同时伴随着发光峰峰位红移;而在波长830 nm的光激发下,PRGO的发光强度比GO略有增强,并且发光峰峰位无明显变化,此结果表明不同尺寸的碳团簇局域态(sp2C团簇)的光还原反应活性不同,这与GO特殊的能带结构密切相关.     

氧化石墨烯水热还原前后的发光光谱

分别采用改进Hummers方法和水热还原法制备了氧化石墨烯(GO)和还原氧化石墨烯(RGO)。 GO和RGO经透射电子显微镜(TEM)、紫外-可见吸收光谱(UV-Vis)、红外光谱(IR)、荧光发射和激发光谱(PL、PLE)等技术手段进行了表征。 荧光发射光谱显示,氧化石墨烯(GO)在可见光的激发下可以得到波长在600~800 nm范围内的宽谱近红外荧光。 通过比较氧化石墨烯水热还原前后的光谱变化,发现氧化石墨烯近红外荧光起源于氧化石墨烯的表面含氧基团,如C=O、COOH。 近红外荧光穿透性好、对生物组织损坏小,非常适合于生物成像,预示着氧化石墨烯在生物成像方面的应用潜力。     

石墨烯/还原氧化石墨烯/聚苯胺复合材料的制备及在超级电容器中的应用

本研究以低成本、易规模化的亲水性石墨烯/氧化石墨烯为前驱体,通过原位聚合的方法制备石墨烯/氧化石墨烯/聚苯胺复合材料,经过化学还原后制备得到石墨烯/还原氧化石墨烯/聚苯胺复合材料.采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和傅里叶红外变化光谱仪(FT-IR)对制备的材料进行了结构和形貌的表征.运用循环伏安法...     

电化学还原的氧化石墨烯修饰电极检测L-色氨酸

制备了氧化石墨烯修饰玻碳电极,并运用循环伏安法对氧化石墨烯进行了直接的电化学还原,研究了L-色氨酸在该电化学还原的氧化石墨烯修饰玻碳电极上的电化学行为。结果表明,L-色氨酸在该修饰电极上其氧化峰电流与裸玻碳电极相比增大了7.1倍,且峰电位负移80mV。利用差分脉冲伏安法,在pH=6.5的磷酸盐缓冲溶液中测定L-色氨酸,氧化峰电流与其浓度在0.4～65.0μmol/L范围内呈良好的线性关系,相关系数为0.998,方法检出限为0.2μmol/L。     

氮掺杂还原氧化石墨烯/四氧化三钴双功能催化剂的制备及表征

采用尿素作为氮源,通过热退火法制备氮掺杂还原氧化石墨烯,然后以乙酰丙酮钴作为钴源通过水热法制备氮掺杂还原氧化石墨烯/四氧化三钴杂化纳米片作为催化氧还原和氧析出反应的双功能催化剂。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线电子能谱仪(XPS)等对其进行形貌结构表征,通过旋转圆盘电极等电化学测试对其电催化性能进行分析,可以看出该催化剂具有良好的氧还原和氧析出催化性能。     

A Green and Mild Approach of Synthesis of Highly-Conductive Graphene Film by Zn Reduction of Exfoliated Graphite Oxide

We report a simple and green approach to synthesize reduced graphene oxide (RGO) nanosheets at room temperature based on Zn reduction of exfoliated GO. The evolution of GO to RGO has been characterized by X-ray diffraction, UV-Vis absorption spectroscopy and Raman spectroscopy. The results of X-ray photoelectron spectroscopy reveal that the atomic ratio of carbon to oxygen in the RGO can be tuned from 1.67 to 13.7 through controlling the reduction time. Moreover, the conductivity of the RGO is measured to be 26.9±2.2 kS/m, much larger than those previously obtained by chemical reduction through other reducing agents. More importantly, the resistance of the RGO film with 20 nm thick-ness can be as low as 2 kΩ/square, while a high transparency over 70% within a broad spectral range from 0.45 μm to 1.50 μm can be retained. The proposed method is low-cost, eco-friendly and highly-effcient, the as-prepared thinner RGO films are useful in a variety of potential application fields such as optoelectronics, photovoltaics and electrochemistry by serving as an ultralight, flexible and transparent electrode material.     

石墨烯负载MnOx催化剂的制备及其低温NH3-SCR活性

通过改进的Hummers法合成氧化石墨烯(GO), 随后采用水热法制备石墨烯负载锰氧化物(MnO_x/GR)催化剂. 考察了催化剂的低温NH₃选择性催化还原(NH₃-SCR)去除NO_x的性能, 并通过傅里叶变换红外(FTIR)光谱, 拉曼(Raman)光谱, X射线衍射(XRD), 透射电镜(TEM), N₂吸附-脱附, X射线光电子能谱(XPS)及H₂程序升温还原(H₂-TPR)等多种表征手段对催化剂的结构及NH₃-SCR性能进行分析. 结果显示, 不同MnO_x负载量的MnO_x/GR催化剂均展现了较好的低温SCR催化活性, 且在负载量为20%(w)时活性最优. 表征分析结果表明, 制备的GO表面含有丰富的含氧基团, 锰可以通过与含氧基团结合而负载到GO上; MnO_x/GR催化剂中MnO_x以纳米颗粒分散于石墨烯载体表面, 且以多种氧化物(MnO、Mn₃O₄和MnO₂)共同存在; 负载量为20%(w)的催化剂中高价锰和表面吸附氧含量增加, 低温区氧化还原能力增强及活性位点数量增加是其SCR活性提高的原因.     

Determination of Sudan I Using Electrochemically Reduced Graphene Oxide

Electrochemically reduced graphene oxide (ER-GO) was prepared by reducing exfoliated graphene oxide sheets on a glassy carbon electrode (GCE). The voltammetric responses of Sudan I-IV were studied at the ER-GO modified GCE (ER-GO/GCE). Compared with chemically reduced graphene oxide (CR-GO) modified electrode (CR-GO/GCE), ER-GO/GCE showed higher voltammetric responses to Sudan I. The electrode had a linear response to Sudan I in the range of 0.04–8.0 µmol L^?1 and a detection limit of 0.01 µmol L^?1. The real sample determination indicated that the proposed method was reliable, effective, and sufficient.     

Electrical Conductivity of Alkaline-reduced Graphene Oxide

A green route using a very simple and straightforward ultrasonic process under alkaline conditions, rather than a general chemical reduction process using hydrazine, was utilized to obtain the hydrophilic reduced graphene oxide(RGO) sheets, via removing oxygen functional groups from graphene oxide(GO) and repairing the aromatic structure. It is found that the conductivity of the obtained RGO could be tuned by changing pH value in alkaline solution, and the current-voltage(I-V) curves of both GO and RGO are nonlinear and slightly asymmetric. Under the same applied voltage, the current of RGO is much larger than that of GO, indicating a pronounced increase in the electrical conductivity of RGO, compared to that of GO.     

Lewis Acid-Promoted Reduction of Bis(triorganotin) Oxides to Hexaorganoditins

Hexalkylditin is prepared by a Lewis acid-promoted (MgCl₂) reductive reaction of bis(trialkyltin) oxide using magnesium metal as reducing agent. Hexabutyl- and hexaphenylditin are synthesized with 95% and 80% yield separately and a radical mechanism is proposed for the reaction condition. Unsymmetric ditin, Bu₃Sn-SnPh₃, was first synthesized by this reductive method.     

Covalently Grafting Graphene onto Si Photocathode to Expedite Aqueous Photoelectrochemical CO2 Reduction

Silicon semiconductor functionalized with molecular catalysts emerges as a promising cathode for photoelectrochemical (PEC) CO₂ reduction reaction (CO₂RR). However, the limited kinetics and stabilities remains a major hurdle for the development of such composites. We herein report an assembling strategy of silicon photocathodes via chemically grafting a conductive graphene layer onto the surface of n⁺-p Si followed by catalyst immobilization. The covalently-linked graphene layer effectively enhances the photogenerated carriers transfer between the cathode and the reduction catalyst, and improves the operating stability of the electrode. Strikingly, we demonstrate that altering the stacking configuration of the immobilized cobalt tetraphenylporphyrin (CoTPP) catalyst through calcination can further enhance the electron transfer rate and the PEC performance. At the end, the graphene-coated Si cathode immobilized with CoTPP catalyst managed to sustain a stable 1-Sun photocurrent of −1.65 mA cm⁻² over 16 h for CO production in water at a near neutral potential of −0.1 V vs. reversible hydrogen electrode. This represents a remarkable improvement of PEC CO₂RR performance in contrast to the reported photocathodes functionalized with molecular catalysts.     

Synergistic effect of UV and l-ascorbic acid on the reduction of graphene oxide: Reduction kinetics and quantum chemical simulations

A photochemical strategy for eco-friendly reduction of graphene oxide (GO) was developed by using l-ascorbic acid (L-AA) as a photosensitive reducing agent. L-AA was excited and oxidized with deprotonation by UV irradiation (254 nm) and the proton coupled electron transfer induces chemical reduction of GO. This photochemical process is quite eco-friendly and scalable, and the reduction kinetics and degree of GO were highly enhanced. To understand the improved reduction power by UV light, the redox properties of L-AA in the ground and excited states were characterized by using quantum chemical simulations. Based on the results, we clearly demonstrated the mechanism how UV irradiation considerably enhances the reducing power of L-AA for the reduction of GO.