Exfoliation of Graphene and Assembly Formation with Alkylated‐C₆₀: A Nanocarbon Hybrid towards Photo‐Energy Conversion Electrode Devices

Abstract

925wileyonlinelibrary.com COMMUNICATION performance. By analogy to the aforementioned graphene and metallic oxide composites, the hybrids of graphene and fullerenes is expected to create a new class of active materials with the strong electron-accepting capability characteristic of fullerenes and the good charge transport properties associated with graphene. Similarly, our previous study has shown that the assembly of C 60 derivatives and single-walled carbon nanotubes (SWCNTs) are promising for photovoltaics. [ 29 ] Compared with SWCNTs, which are 1D and a mixture of semiconducting and metallic, graphene is 2D and has purely semimetal characteristics, thus providing a more preferred geometry and a simpler electronic structure to collaborate with C 60 , promoting the charge separation and charge transfer.Various fabrication methods have been explored for obtaining a single layer graphene nanosheet. [ 14,30 ] Among them, along with the breakthrough isolation of a single layer of graphene from a graphite surface by the adhesive tape method, [ 31 ] chemical treatment of solution-dispersible graphene has received intense interest and is regarded as one of the most cost-effective and tractable preparation methods. [ 32,33 ] In general, graphite is converted to solution dispersible graphite oxide (GO) by oxidation-based intercalation followed by a chemical reduction which turns GO to graphene (strictly referred to as reduced graphene oxide, rGO). Most oxygen-containing substituent groups can be removed by chemical reduction; however, a large number of defects remain in the rGO, which leads to considerable disruption of the favorable electronic properties of graphene. [ 32,34 ] Great efforts have been devoted to directly exfoliating graphite into graphene sheets, i.e., exfoliating graphite by sonicating it directly in organic solvents [ 35 ] or with the aid of organic intercalators/surfactants. [36][37][38] However, the amount of exfoliated graphene is usually very little relative to the starting material and the actual yield is typically less than 1%. Moreover, the resulting graphene tends to agglomerate or restack through van der Waals interactions. In this regard, there is a highly important demand to develop a methodology of producing large quantities of unoxidized graphene containing fewer defects and simultaneous compositing with other functional molecules for improving their optoelectronic properties.Here, we show that graphene of high quantity is directly exfoliated from graphite in organic solvents in the presence of an alkylated-C 60 molecule ( 1 , Figure 1 a), which is 3,4,5-tris(eicosyloxy)phenyl substituted N -methyl[60]fulleropyrrolidine, [ 39 ] through noncovalent attractive interactions. Importantly, for the as-obtained 1-graphene assembly, graphene boosts nearly 270-fold higher photocurrent than 1 itself.As we reported recently, SWCNTs are mostly unbundled due to the assembly with 1 and well-dispersed in organic solvents,

Metal-Free All-Carbon Nanohybrid for Ultrasensitive Photoelectrochemical Immunosensing of alpha-Fetoprotein

“…Notably, the maximum absorption of GO at 230 nm, which was commonly assigned to the π–π* transition of the aromatic CC bond, showed a blue shift in Gr-GO (228 nm), AC 60 -GO (220 nm), and AC 60 -Gr-GO (213 nm), which suggested an electron transfer among GO and AC 60 , and graphite sheets. − Such electron communication could be ascribed to the π–π noncovalent interactions among them. In addition, the UV–vis spectra (Figure f) showed the absorbance of AC 60 -Gr-GO was much higher than that of Gr-GO, confirming the wide light absorption in the whole UV–vis range due to AC 60 . Therefore, AC 60 -Gr-GO nanohybrid was successfully prepared.…”

“…In addition, the UV−vis spectra (Figure 2f) showed the absorbance of AC 60 -Gr-GO was much higher than that of Gr-GO, confirming the wide light absorption in the whole UV−vis range due to AC 60 . 30 Therefore, AC 60 -Gr-GO nanohybrid was successfully prepared.…”

“…Fullerenes, such as C 60 , have attracted enormous interest both theoretically and experimentally due to their unique physiochemical properties. − Concretely, C 60 can be reversibly reduced by accepting up to six electrons and exhibited wide absorption in the whole UV–vis range, making it an attractive photoactive probe in constructing PEC biosensors. − However, few studies have been reported for the applications of fullerenes in the research areas of PEC biosensing, partially due to the low electronic conductivity and poor interfacial interactions with biomolecules. − In principle, prospective properties could be achieved by a rational modification of fullerene into potential derivatives. In our previous work, we showed that the solubility of fullerene in organic solvents could be immensely enhanced by modifying fullerene with three long alkyl chains via a Prato reaction, and the photoelectric conversion efficiency of alkylated fullerene C 60 (AC 60 ) could be greatly improved by assembling with graphene due to the high affinity of long alkyl chains to the graphene …”

“…In our previous work, we showed that the solubility of fullerene in organic solvents could be immensely enhanced by modifying fullerene with three long alkyl chains via a Prato reaction, and the photoelectric conversion efficiency of alkylated fullerene C 60 (AC 60 ) could be greatly improved by assembling with graphene due to the high affinity of long alkyl chains to the graphene. 30 To address the challenge of PEC biosensing application of fullerenes, herein, we report the coupling of AC 60 with graphite flake (Gr) and graphene oxide (GO) into a metal-free all- carbon nanohybrid (AC 60 -Gr-GO) by a simple wet grinding method, thanks to delicate noncovalent interactions among them. As electron collector and transporter, the Gr in the assembly accelerated the charge-transfer and enhanced the photoelectric conversion efficiency of AC 60 up to 35 times.…”

The formation of self-assembled structures of C60 in solution and in the volume of an evaporating drop of a colloidal solution

“…In a number of pure and mixed organic solvents, fullerene С n (n = 60, 70, 76, …) molecules show a pronounced tendency to self-assembly and the formation of fairly large functional fullerene aggregates of various shapes and sizes. The problem was fundamentally studied by different physical and chemical methods in [3][4][5][6][7][8][9][10][11] and the obtained results provided a vector toward potential applications in material chemistry [12,13], biomedicine [14][15][16], phototherapy [17][18][19], molecular electronics [20], optoelectronics [21,22] and solar energy [23][24][25].…”