Fullerenes and derivatives as electrocatalysts: Promises and challenges

Carbon-based metal-free nanomaterials are promising alternatives to precious metals as electrocatalysts of key energy storage and conversion technologies.Of paramount significance are the establishment of design principles by understanding the catalytic mechanisms and identifying the active sites.Distinct from sp2-conjugated graphene and carbon nanotube,fullerene possesses unique characteristics that are growingly being discovered and exploited by the electrocatalysis community.For instance,the well-defined atomic and molecular structures,the good electron affinity to tune the electronic structures of other substances,the intermolecular self-assembly into superlattices,and the on-demand chemical modification have endowed fullerene with incomparable advantages as electrocatalysts that are otherwise not applicable to other carbon ma-terials.As increasing studies are being reported on this intriguing topic,it is necessary to provide a state-of-the-art overview of the recent progress.This review takes such an initiative by summarizing the promises and challenges in the electrocatalytic applications of fullerene and its derivatives.The content is structured according to the composition and structure of fullerene,including intact fullerene(e.g.,fullerene composite and superlattices)and fullerene derivatives(e.g.,doped,endohedral,and disintegrated fullerene).The synthesis,characterization,catalytic mechanisms,and deficiencies of these fullerene-based materials are explicitly elaborated.We conclude it by sharing our perspectives on the key aspects that future efforts shall consider.

Tunable tribological properties in water-based lubrication of water-soluble fullerene derivatives via varying terminal groups

In this paper,three kinds of water-soluble fullerene derivatives were synthesized via electrophilic addition reaction and cycloaddition reaction,respectively.The chemical composition characterizations of these derivatives indicated the successful preparation of C60(OH)x,C60(C(COOH)2)x and C60(OH)x(NHCH2COOH)y fullerene derivatives.The aggregation and morphology characterizations showed that the three kinds of derivatives had an ideal spherical aggregating structures and excellent dispersibility in water,especially C60(OH)x and C60(C(COOH)2) x.The lubrication performance of the fullerene derivatives acted as lubricant additives were investigated at different concentrations in the range of 0-1 wt%.The results indicated that the addition of polyhydroxyl and carboxylic derivatives could improve the lubrication properties,which led to the reduction of wear to about 40% at most.It is attributed that the optimized substitutions of fullerene molecules may be of benefit to their distribution properties and lubricating behaviors in water based lubrication.

Synthesis of Fullerene Hydrazine Derivatives

C 60 /C 70 mixture reacts with hydrazine hydrate catalysed by tetrabutylammonium bromide (TBAB) in the presence of air to afford fullerene hydrazine derivatives C 60 (OH) n(NHNH 2) n and C 70 (OH) n(NHNH 2) n,which are characterized by means of MS and FTIR.A possible reaction mechanism is discussed.

Multilayer Film Fabrication and Photoelectric Conversion Property of Two Pyrrolidinofullerene Carboxylic Acid Derivatives

Two multilayer films of pyrrolidinofullerene carboxylic acid derivatives, which exhibit photoelectric conversion property, are reported here. The first monolayers were fabricated on hydrophilic indium-tin-oxide (ITO), quartz, and mica by esterification reaction. The multilayers were characterized by contact angle and UV spectrum. The photoelectric conversion properties of both multilayer films were studied.

Film-Forming Properties of Fullerene Derivatives in Electrospray Deposition Method

Thin films of three types of fullerene derivatives were prepared through the electrospray deposition (ESD) method. The optimized conditions for the fabrication of the thin films were investigated for different types of fullerene derivatives: [6,6]-phenyl-C61-butyric acid methyl ester, [6,6]-phenyl-C71-butyric acid methyl ester, and indene-C60-monoadduct. The spray diameter during the ESD process was observed as a function of the supply rate achieved by changing the applied voltage. In all cases, the spray diameter increased with increasing applied voltage, reaching the maximum diameter (Dmax) in the voltage range 4 to 6 kV. It was clear that Dmax was influenced by the dipole moments of the fullerene derivatives (as calculated by density functional theory methods). Scanning electron microscopy observation of the?fabricated thin films showed that imbricated structures were formed through the stacking of the fullerene-derivative sheets. Atomic force microscopy images revealed that the density of the imbricated structure was dependent on the spray diameter during the ESD process, and the root-mean-square roughness of the film surface decreased with increasing applied voltage. These findings suggest that the ESD method will be effective for the preparation of fullerene-derivative thin films for the production of organic devices.

Effect of Crystallinity of Fullerene Derivatives on Doping Density in the Organic Bulk Heterojunction Layer in Polymer Solar Cells

Polymer solar cells （PSCs） based on poly（3-hexylthiophene） （P3HT） and [6,6]-phenyl-C61-butyric acid methyl ester （PCBM） are fabricated by using 1,8-diiodooctane （DIO） as a solvent additive to control the doping density of the PSCs. It is shown that the processing of DIO does not change the doping density of the P3HT phase, while it causes a dramatic reduction of the doping density of the PCBM phase, which decreases the doping density of the whole blend layer from 3.7 × 10^16 cm-3 to 1.2 ×10^16 cm-3. The reduction of the doping density in the PCBM phase originates from the increasing crystallinity of PCBM with DIO addition, and it leads to a decreasing doping density in the blend film and improves the short circuit current of the PSCs.

Spectral Investigations of Hybrid Nanostructures Including Modified Fullerene C60 and Carbazole-Derivative Fluorophore

Hybrid nanostructures including modified fullerene C60 and fluorophoric (E)-2-Cyano-3-(9-ethyl-9Н-carbazole-3-yl)-acrylic acid (cyanoacrylic acid I) were created. Spectral properties (absorption and luminescence spectra) of the hybrid nanostructures were investigated. It was established what molecules C60 strongly affected spectral properties of cyanoacrylic acid I in the hybrid nanostructures. Luminescence quenching of fluorophore and a change of luminescence features were observed in the hybrid nanostructures.

EXPERIMENTAL STUDY ON TRIBOLOGICAL PROPERTIES OF FULLERENE COPOLYMER NANOBALL

A novel fullerene-styrene-maleic anhydride copolymer is reported. TEM analyses shows it is water- soluble nanoball of average diameter of about 83 nm. The tribological behavior is evaluated by foul-ball machine. It was found that addition of fullerene copolymer to base stock (2%triethanolamine aqueous solution)resulted in a raise in load-carrying ability(F value)from 130 N to maximum 480 N, and a reduction in coefficient of friction from 0.235 to minimum 0. 063. SEM analyses indicates that the wear scare obtained with fullerene copolymer exhibited mild scratches, while sharp grooving and serious pull-out phenomnon were observed in the presence of base stock without additive .The improvements in friction, wear and load-carrying capacity are probably due to the presence of fullerene copolymer nanoballs, which may act as molecule ball bearings, which in turn lead to elastic rolling lubrication.

An Approach to New Water-soluble Oligo(ethylene glycol) Camptothecin Analogues by 1,3-Dipolar Cycloaddition

Combined with an effective copper-catalyzed triazole-forming reaction, a series of novel camptothecin derivatives were synthesized. Incorporating oligo（ethylene glycol） chains into the derivatives enhanced their water-solubility when compared to the parent compound （up to 55-fold）.

Inhibition of M-MuLV reverse transcriptase activity by fullerene derivatives

Influence of fullerene (C60) derivatives on M-MuLV reverse transcriptase activity is investi- gated. Two water-soluble fullerene derivatives, fullerol (C60(OH)23-24) and trimalonic acid C60 (TMA C60, C63(COOH)6) are used in the experiments and their effects on in vitro reverse transcription-polymerase chain reaction (RT-PCR) of β-actin mRNA in HeLa cells are determined. PCR products are detected by agarose gel electrophoresis. It is found that the amounts of PCR products decrease with addition of either of two fullerene derivatives to RT reaction mixture. The inhibition of fullerene derivatives is dose-dependent, and IC50 values of fullerol and TMA C60 are 0.089 and 0.039 mmol/L, respectively. The amount of PCR products obtained by direct addition of fullerol or TMA C60 to PCR are greater than those obtained by addition of the equivalent amount of fullerol or TMA C60 to RT, indicating an inhibitory ef- fect of fullerol or TMA C60 on RT. The compensative experiment of M-MuLV reverse transcriptase shows that increasing enzyme amounts can antagonize the activity of fullerol or TMA C60. These results imply that fullerenes can inhibit M-MuLV reverse transcriptase activity, with the inhibition of TMA C60 slightly stronger than fullerol, and that their potential in treatment of diseases induced by RNA viruses such as leukemia virus needs further investigation.

Synthesis of water-soluble C_(60) derivatives and their scavenging free radical activity

Four piperazine-appended [60] fuilerenes (1a-1d) were synthesized and characterized. Their activities of scavenging radical were studied via UV-Vis and EPR. The results indicate that light irradiation is of advantage to increase the activity of scavenging radical.

A Convenient Synthesis of Novel Meldrum＇s Acid C60 Fullerene Derivatives

A series of novel Meldrum＇s acid C60 derivatives were prepared in moderate yields from a convenient one-pot reaction of C60, the Meldrum＇s acid derivatives, 12 and 1,8-diazabicyclo-[5,4,0]-undec-7-ene （DBU） in toluene at room temperature under nitrogen atmosphere. All the new compounds were fully characterized by the spectral data and elemental analysis. A carbene intermediate mechanism was proposed for this reaction.

Synthesis of two A-B-C type conjugated amphiphilic triblock fullerene derivatives and their application in organic solar cells

Two A-B-C type conjugated amphiphilic triblock fullerene derivatives C60-2 HMTPB and C60-2 EHTPB were obtained in multi steps synthesis with three different blocks,and the amphiphilic diblock molecular C60-4 TPB was also preferred as a reference.When as modifying layer on zinc oxide(ZnO),the three fullerene derivatives can all reduce the work function of ZnO via modulation of the interfacial dipoles and lead a better electrical coupling.As introducing treatment of toluene,the obvious self-assembly of fullerene derivatives were observed,which were supported by X-ray diffraction and contact angle of water measurement.Base on PTB7-Th:PC71 BM system,the inverted organic solar cells devices with structure of ITO/ZnO/fullerene derivatives/PTB7-Th:PC71BM/Mo03/Al got power conversion efficiencies of 8.62%,8.83%and 9.00%for C60-4 TPB,C60-2 HMTPB and C60-2 EHTPB,respectively,compared 8.13%of devices with bare ZnO.The result of conjugated amphiphilic triblock fullerene derivatives provides a straightforward approaching by simultaneously modulating the morphology and interfacial work function of ZnO,which can also lead high performance in optoelectronic devices.

Synthesis of two pentaarylated [60]fullerene derivatives Ar_5C_(60)-H (Ar = p-MeC_6H_4, m-MeC_6H_4) and their novel electrochemical properties

Through one pot reaction of C60 with organocopper/magne-sium reagent ( p - MeQ H4 )2 CuMgBr or ( m - MeC6 H )2 -CuMgBr prepared from CuBr-Me2S and p-MeC6H4MgBr or m-MeC6H4MgBr and subsequent quenching with aqueous NH4Cl, two pentaarylated [60] fullerene derivatives (p-MeC6H4)5C60H (1) and (m-MeC6H4)5C60H (2) have been synthesized in 94% and 96% yields, respectively. While known compound 1 prepared via this improved method is unambiguously identified, new compound 2 is fully characterized by elemental analysis, IR, UV-vis, 1H NMR and 13C NMR spectroscopies. Additionally, electrochemical study shows that the two [60] fullerene derivatives 1 and 2 in dichloromethane solution display two sequential one-electron reductions which are shifted by about 0.4V towards more negative potential values with respect to free C60. Such remarkable cathodic shift is attributed to the multiple breakage of the double-bond conjugation within the fullerene core.

Electric field controlled superlubricity of fullerene-based host–guest assembly

Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems.In this work,the assembly structure and microscale superlubricity of a host–guest assembly are effectively controlled by the electric field.With the help of the scanning tunneling microscopy(STM)technique,the host–guest assembly structures constructed by the co-assembly of fullerene derivative(Fluorene-C60)with macrocycles(4B2A and 3B2A)are explicitly characterized.Combined with density functional theory(DFT),the distinct different assembly behaviors of fullerene derivatives are revealed at different probe biases,which is attributed to the molecular polarity of the fullerene derivative.Through the control on the adsorption behavior,the friction coefficient of host–guest assembly is demonstrated to be controllable in the electric field by using atomic force microscopy(AFM).At positive probe bias,the friction coefficient of the host–guest assembly is significantly reduced and achieves superlubricity(μmin=0.0049).The efforts not only help us gain insight into the host–guest assembly mechanism controlled by the electric field,but also promote the further application of fullerene in micro-electro-mechanical systems(MEMS).

A multifunctional and scalable fullerene electron transporting material for efficient inverted perovskite solar cells and modules

The interfacial properties between charge transporting material and perovskite(PVSK)play critical roles in governing the photovoltaic performances of perovskite solar cells(PVSCs).Herein,we develop a multifunctional fulleropyrrolidine(FMG)as an electron transporting material(ETM),which facilitates the construction of efficient and stable inverted PVSCs and modules.It revealed that the facile and scalable FMG possesses not only excellent electron extraction capabilities,but also multi-groups to simultaneously passivate PVSKs via Lewis acid-base and hydrogen bonding interactions.The coating of FMG onto PVSK interestingly yields a dense and interactive layer with the graded ETM-PVSK heterojunction architecture.As a result,FMGbased PVSCs demonstrate a champion efficiency of 23.8%,outperforming 21.0%of PCBM-based devices.FMG could also be utilized to improve photovoltaic performance of large-scale modules.In addition,FMG has successfully elongated the lifetime of the corresponding PVSCs,maintaining 85%of the initial performance after the continuous 60-day one sun equivalent illumination in ambient.

Efficient and Convenient Preparation of Water-Soluble Fullerenol

An efficient and convenient preparation of fullerenols was described. With polyethylene glycol (PEG) 400 as catalyst, fullerenols were conveniently synthesized via the direct reaction of fullerene with aqueous NaOH. By con-trol of reaction conditions, either water-soluble C60 fullerenol or water-insoluble C60 fullerenol could be obtained selectively.

Spectroscopic Studies of a Water-soluble Derivative of Hypocrellin A and Its One- and Two-Electron Reduction Products

In this study the spectroscopic characteristics of a water-soluble derivative of hypocrellin A (HA), 14-dehydroxy-15-deacetyl-hypocrellin A-13-sulfonate(13-SO3Na-DDHA),and its one- and two-electron reduction products have been investigated. From the changes in absorbance with pH it was observed that the two phenolic hydroxy groups at C-3 and C-10 positions of 13-SO3Na-DDHA or HA dissociated stepwise with increase of pH values. The pKa values for 13-SO3Na-DDHA and HA were determined using an effective method established in this study. Attempts were also made to use absorption and ESR spectroscopies to study the photoreduction of 13-SO3Na-DDHA. It was found that 13-SO3Na-DDHA was directly reduced to its two-electron reduction product in buffered aqueous solution (pH 7. 7). However, in DMF-buffer (1 :1/ v : v,pH 7. 7), it proceeded with one-electron reduction to generate its semiquinone radical anions. The semiquinone radical anions decayed according to second-order kinetics. indicating that the