Fullerene Doping Research Articles

Alkali metal-doped C20 fullerene sensors for COVID-19 biomarker detection: DFT insights into naked-eye and infrared techniques

Prompt diagnosis and prevention from coronavirus disease (COVID-19), a highly contagious infection, are critically required. While PCR testing is effective, it is costly, painful, and time-consuming. Alternatively, breath analysis for detecting COVID-19 provides a cost-effective and instant diagnostic approach. COVID-19 infected patients exhale ethyl butyrate (EB) as a biomarker of the infection. This study explores the doping of C20 fullerene with alkali metals to enhance its ability to detect ethyl butyrate. EB was weakly adsorbed onto C20 and strong adsorbed on doped fullerenes (M@C20) with maximum adsorption energies of −27.66 kcal/mol for Li@C20. QTAIM and IRI analyses confirmed Van der Waals interactions between EB and M@C20. NBO and MEP analyses provided evidence of charge transfer from the biomarker towards the M@C20. This charge transfer decreased the carbonyl bond stretching frequency from 1838 cm−1 to 1772, 1782, and 1788 cm−1 in three complexes (EB−Li@C20, EB−Na@C20, and EB−K@C20), respectively. This IR analysis supports the potential application of doped fullerenes in infrared-based detectors. Absorption maxima (λmax) were calculated as 534 nm (green), 594 nm (yellowish orange), and 587 nm (yellow) for three complexes. These shifts indicate potential application of M@C20 in naked-eye detectors. The shortest recovery time was 2.9 × 10−11 s for K@C20, suggesting it a suitable reusable sensor. These findings enable the development of fullerene-based sensors for both naked-eye and infrared-based detection of COVID-19.

Nano-structuration influence on the polyimide-based spatial light modulator’s parameters

The classical and the nano-structured spatial light modulators (SLMs) especially based on the polyimide photosensitive layers, as the key element of the optoelectronic devices, display, and telecommunications schemes are considered. The main emphasis is placed on the device with a polyimide photo-layer due to its high sensitivity and acceptable performance. A modulator’s basic characteristics are studied taken into account the comparison with the different types of the photo-layers, such as: ZnSe, ZnS, a-Si:H. Liquid crystal (LC) media is considered as the modulation system. It is indicated that the different methods and approaches are applied for investigation of the basic SLM parameters, such as: Z-scanning technique, third harmonic generation, four-wave mixing set-up, etc. In the current paper the laser holographic technique is used to investigate the resolution, sensitivity, and speed of the LC-SLM devices. The influence of the fullerene doping on the organic photo-layers based on the polyimide materials is presented. This influence of this nano-structuration process on the modulator’s basic parameters is discussed.

Study on the enhancement of dielectric properties of epoxy resin composites by fullerene doping

Abstract Based on the fact that C60 is one of the most abundant and readily available molecular configurations in the fullerene family, this paper investigates the effect of doping fullerenes on the dielectric properties of epoxy composites using C60 as a representative. The structure and properties of fullerene molecules are thoroughly examined from the point of view of materials chemistry. The equipment required for the experiment is selected, the experimental sample preparation plan is formulated, and the structure and dielectric properties of the prepared samples are analyzed by corresponding data analysis. The results show that in the range of r less than 1.03 Å, the particle distribution probability of the fullerene-doped epoxy composites in this interval is 0. As r continues to increase, the probability density of the fused C60 epoxy composites is higher than that of the epoxy matrix. The frequency band of 1 MHz has an enhancement of 0.053 and 0.043. However, the dielectric constant of the composite epoxy resin in the high-frequency interval gradually falls back with the increase of filler, while the enhancement of the dielectric constant occurs in the low-frequency interval, and the fullerene is also optimized in terms of the dielectric constant and dielectric loss properties. Fullerene’s excellent dielectric properties have been confirmed by this study, which is important to broaden the epoxy resin market and improve the competitiveness of products.

Effect of fullerene doping on electronic and photovoltaic properties of the cubic bicontinuous phase

Fullerene doping allows for tuning the conductivity and photovoltaic properties of cubic bithiophene-based liquid crystalline organic semiconductors.

Noncovalent Doping of Fullerene (C60) into ZnAl–LDH/PVA Matrix and Photocatalytic Degradation of Methylene Blue and Congo Red from Water

Noncovalent Doping of Fullerene (C60) into ZnAl–LDH/PVA Matrix and Photocatalytic Degradation of Methylene Blue and Congo Red from Water

Experimental Investigation of the Friction Modifying Effects of Graphene and C60 Fullerene Used as Nanoadditives in Engine Lubricating Oil Performed on an Oscillating Tribometer

The present article presents the results of tribological investigations performed on an off-the-shelf engine lubricant containing nanoadditives of multilayered graphene and C60 fullerene alternately. As anthropogenic CO2 is believed to be highly responsible for global climate change, its emission is regulated in many countries. CO2 emissions can be significantly decreased by improving the efficiency i.e. decreasing the losses in an engine. Hence reducing frictional losses was the ultimate scope of the investigations presented in this article. The experiments were carried out on an oscillating tribometer at the Department of Internal Combustion Engines at Széchenyi István University. The experiments showed that multilayered graphene in engine lubricant did not modify the friction coefficient inevitably (-1% to +4%). Fullerene nanoparticles, however, reduced the friction by 4–8%. The optimal fullerene doping quantity that resulted in the lowest friction showed to be at around 0.14 wt%.

Spin and orbital magnetism of exohedral fullerene doped with single transition metal atom (Sc-Ni): A relativistic density functional theory study

Relativistic density functional theory calculations have been implemented to study the structural configurations, electronic and magnetic properties of exohedral 3d transition metal atoms doping on C60 fullerene (TM-C60) by a full potential local orbital method. The calculated binding energies revealed that the TM-C60 molecules are energetically stable in all adsorption sites. We also found that the TM-doped exohedral C60 complexes are more reactive than pure C60 fullerene. The spin and orbital magnetic moments were also determined. We have indicated that in all of the five adsorption sites, exohedral TM-C60 molecules (except for Ni-C60) are magnetized. Our magnetic calculations show that the total spin magnetic moments of TM-C60 molecules mainly come from the TM atoms. We found that the spin magnetic moments of adsorbed TM atoms in exohedral doping C60 fullerene from Sc to Mn (HH adsorption site) and for Sc to Cr (HP and P adsorption sites) are greater than their free states. Our calculations suggest that exohedral doping 3d TM-C60 complexes can almost maintain spin magnetic moments. We have indicated that the magnetic properties of exohedral TM-C60 molecules change in the presence of spin–orbit coupling. Significant orbital contributions to magnetic moments are recognized in these configurations while the spin moments are unaffected. We found that Co in exohedral doping of C60 fullerene shows a robust orbital moment in all the five adsorption sites.

Flicker‐Free Fringe‐Field Switching Liquid Crystal Display Operable at Extremely Low Frequencies for Power Saving

A fringe‐field switching (FFS) liquid crystal (LC) mode used with a negative dielectric LC (n‐LC) that is operable at an extremely low‐frequency signal voltage regime, without image flickering, is proposed. By doping charge‐trapping fullerenes (doping concentration: 0.2 wt%) into a low‐resistivity polyimide LC alignment layer of the FFS n‐LC mode, the mobile ionic‐charge density within the n‐LC layer can be drastically decreased. Thus, excellent voltage‐holding ratios of 98.24% and 87.91% are achievable in the proposed FFS n‐LC mode at low operation frequencies of 0.5 Hz and 0.2 Hz, respectively, corresponding to the improvement rates of 155.69% and 1127.05% at each operation frequency, compared with the FFS n‐LC mode without the fullerene doping case. The evaluation results by the modulation flicker level reveal that the operation frequency of the proposed device scheme can be decreased significantly (≈0.2 Hz) without inducing the perceptible image‐flickering problems.

Characterization of titanium influences on structure and thermodynamic stability of novel C20-nTin nanofullerenes (n=1-5): a density functional perspective.

In this survey, effects of titanium heteroatom(s) on structural parameters and thermodynamic stability of C20 fullerene and its C20-nTin derivatives (n = 1-5) are compared and contrasted, at DFT levels of theory. The results show that in going from C19Ti1 to C15Ti5, binding energy increases while absolute value heat of atomization decreases. According to vibrational frequency analysis, excepting C16Ti4-1, the other optimized structures give no imaginary frequency as true minima. The calculated binding energy of 887.12kcalmol-1/atom displays C15Ti5 as the most thermodynamically stable heterofullerene. It has Cs symmetry and contains five titanium atoms alternatively in equatorial position. The substitutional doping of C20 fullerene leads to high Mülliken charge distribution upon the surfaces of the resulted heterofullerenes especially C19Ti1 as suitable hydrogen storage. The contour plots indicate the most negative electrostatic potential by red color for C atoms, whereas the most positive electrostatic potential by yellow color for Ti heteroatoms. The contour plots and multiwfn analysis exhibit charge transfer from titanium heteroatoms to the neighboring carbon atoms. Furthermore, the resulted electron density maps from multiwfn qualitatively confirm the contour plot's findings. The hydrogen adsorption is an endothermic process for C20 fullerene and exothermic process for C20-nTin heterofullerenes. Major criteria examined for thermodynamic stability; from C19Ti1 to C15Ti5, binding energy and hydrogen adsorption increase while heat of atomization decreases.

Inverted organic solar cells with non-clustering bathocuproine (BCP) cathode interlayers obtained by fullerene doping

Bathocuproine (BCP) is a well-studied cathode interlayer in organic photovoltaic (OPV) devices, where it for standard device configurations has demonstrated improved electron extraction as well as exciton blocking properties, leading to high device efficiencies. For inverted devices, however, BCP interlayers has shown to lead to device failure, mainly due to the clustering of BCP molecules on indium tin oxide (ITO) surfaces, which is a significant problem during scale-up of the OPV devices. In this work, we introduce C70 doped BCP thin films as cathode interlayers in inverted OPV devices. We demonstrate that the interlayer forms smooth films on ITO surfaces, resulting from the introduction of C70 molecules into the BCP film, and that these films possess both improved electron extraction as well exciton blocking properties, as evidenced by electron-only devices and photoluminescence studies, respectively. Importantly, the improved cathode interlayers leads to well-functioning large area (100 mm2) devices, showing a device yield of 100%. This is in strong contrast to inverted devices based on pure BCP layers. These results are founded by the effective suppression of BCP clustering from C70, along with the electron transport and exciton blocking properties of the two materials, which thus presents a route for its integration as an interlayer material towards up-scaled inverted OPV devices.

On the Stability of Permanent Electrochemical Doping of Quantum Dot, Fullerene, and Conductive Polymer Films in Frozen Electrolytes for Use in Semiconductor Devices.

Semiconductor films that allow facile ion transport can be electronically doped via electrochemistry, where the amount of injected charge can be controlled by the potential applied. To apply electrochemical doping to the design of semiconductor devices, the injected charge has to be stabilized to avoid unintentional relaxation back to the intrinsic state. Here, we investigate methods to increase the stability of electrochemically injected charges in thin films of a wide variety of semiconductor materials, namely inorganic semiconductors (ZnO NCs, CdSe NCs, and CdSe/CdS core/shell NCs) and organic semiconductors (P3DT, PCBM, and C60). We show that by charging the semiconductors at elevated temperatures in solvents with melting points above room temperature, the charge stability at room temperature increases greatly, from seconds to days. At reduced temperature (−75 °C when using succinonitrile as electrolyte solvent) the injected charge becomes entirely stable on the time scale of our experiments (up to several days). Other high melting point solvents such as dimethyl sulfone, ethylene carbonate, and poly(ethylene glycol) (PEG) also offer increased charge stability at room temperature. Especially the use of PEG increases the room temperature charge stability by several orders of magnitude compared to using acetonitrile. We discuss how this improvement of the charge stability is related to the immobilization of electrolyte ions and impurities. While the electrolyte ions are immobilized, conductivity measurements show that electrons in the semiconductor films remain mobile. These results highlight the potential of using solidified electrolytes to stabilize injected charges, which is a promising step toward making semiconductor devices based on electrochemically doped semiconductor thin films.

Atomically defined angstrom-scale all-carbon junctions

Full-carbon electronics at the scale of several angstroms is an expeimental challenge, which could be overcome by exploiting the versatility of carbon allotropes. Here, we investigate charge transport through graphene/single-fullerene/graphene hybrid junctions using a single-molecule manipulation technique. Such sub-nanoscale electronic junctions can be tuned by band gap engineering as exemplified by various pristine fullerenes such as C60, C70, C76 and C90. In addition, we demonstrate further control of charge transport by breaking the conjugation of their π systems which lowers their conductance, and via heteroatom doping of fullerene, which introduces transport resonances and increase their conductance. Supported by our combined density functional theory (DFT) calculations, a promising future of tunable full-carbon electronics based on numerous sub-nanoscale fullerenes in the large family of carbon allotropes is anticipated.

Effect of dopant nitrogen on the thermoelectric properties of C20 and C60 fullerene in graphene nanoribbon junction

We study the thermoelectric properties of a system that consists of fullerene molecule which connects to graphene nanoribbons. Our research includes C20 as the smallest fullerenes and C60 as the most stable and abundant type of fullerenes. The calculations are done using the density functional theory and non-equilibrium Green function in a linear response regime. We address properly the important thermoelectric quantities and their behaviors. Results show that doping of fullerene with a nitrogen causes new levels of energy in vicinity of Fermi level. Although doping has different effects on the electrical conductivity, phonon and electron contributions to the thermal conductivity and thermopower of the molecule but it eventually causes the figure of merit increases.

Enhanced reproducibility of planar perovskite solar cells by fullerene doping with silver nanoparticles

A small cross-section of silver nanoparticles (AgNPs) placed at the rear-part of the solar cell avoids the parasitic absorption of the nanoparticles which is the biggest barrier for plasmonic structures when acting as photocurrent enhancers. Herein, we demonstrate p-i-n planar perovskite solar cells with the structure ITO/PEDOT:PSS/MAPbI3/PCBM/Ni:Au, where the PCBM electron extraction layer (EEL) was intentionally modified with variable amounts of AgNPs. The addition of small amounts of AgNPs (e.g., 5 wt. %) into the PCBM improved the overall reproducibility and reliability of the solar cell fabrication process after optimization. Plasmonic simulations suggest that any plasmonic-optical effects are relatively small compared to sample absorbance due to perovskite alone. It has been concluded that plasmonic-electrical effects play a major role in averaged performance improvement. Therefore, the addition of small AgNPs in low concentration to the EEL layer accounts for higher Jsc, Voc and FF as a result of a better perovskite coverage by the EEL and an improved charge carrier collection as evidenced by morphological and electrical analysis.

Remarkably improved electrical insulating performances of lightweight polypropylene nanocomposites with fullerene

A polypropylene/fullerene nanocomposite was fabricated via solution processing with good dispersion of the fullerene nanoparticles. It was observed that a small amount of fullerene (~1 wt. ‰) can significantly improve the direct current (DC) electrical insulation performance (i.e. improved space charge distribution, greater DC dielectric breakdown strength, and larger DC volume resistivity) of polypropylene. Thermally stimulated depolarization current tests indicate that fullerene doping remarkably increases the deep trap density of pure polypropylene. The mechanisms by which the electrical properties of the polypropylene nanocomposites were improved are the introduction of deep traps and the high electron affinity of fullerene. The deep traps result from the interfaces between polypropylene and fullerene. This work provides a potential method to tailor lightweight nanodielectric materials with excellent electrical insulating performances.

Effect of the fullerene in the properties of thin PEDOT/C60 films obtained by co-electrodeposition

Organic electronics requires the development of reproducible and highly conductive thin films. The arrangement of poly(3,4-ethylenedioxythiophene) (PEDOT) with fullerene C60 leads to products with the combined properties of both species that are excellent candidates for these applications. However, very little has been studied about the effect of doping PEDOT with C60, and thus there is a lack of information regarding the morphology, electrochemical and electrochromic properties of the resulting films. Herein, simultaneous electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with fullerene C60 was carried out via cyclic voltammetry in the range from 0.0V to +1.5V (vs Ag/AgCl) in a three-compartment cell. ITO coated on PET was used as both working and counter electrodes. The fullerene presence within the films was confirmed with MALDI and TGA (27.5% of fullerene content). The cyclic voltamograms showed that the C60-doped film has a higher oxidation potential, what was attributed to the electron affinity of the fullerene cage. Furthermore, the spectroelectrochemical and electrochromic analyses showed that the PEDOT/C60 films present a dark violet coloration in the reduced state, which differs from the usual dark blue of the PEDOT polymer. Finally, the morphology was analyzed using AFM and SEM, and pillar structure of broccoli-like particles was observed for both films. However, the fullerene doping generated smaller polymer-based particles, thus forming a denser structure with higher surface area, suggesting the use of the cages as nucleation points for the polymerization.

Electronic structure evolution in doping of fullerene (C60) by ultra-thin layer molybdenum trioxide

Ultra-thin layer molybdenum oxide doping of fullerene has been investigated using ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS). The highest occupied molecular orbital (HOMO) can be observed directly with UPS. It is observed that the Fermi level position in fullerene is modified by ultra-thin-layer molybdenum oxide doping, and the HOMO onset is shifted to less than 1.3 eV below the Fermi level. The XPS results indicate that charge transfer was observed from the C60 to MoOx and Mo6+ oxides is the basis as hole dopants.

Effect of fullerene doping on the electrical properties of P3HT/PCBM layers

Poly (3-hexylthiophene-2, 5-diyl) (P3HT) and its blend with Phenyl-C61-Butyric acid-Methyl-Ester (PCBM) and fullerene (C60) thin films were prepared and their electrical properties for memory applications were studied. Due to doping, a sharp decrease in the resistance for a P3HT:PCBM:C60 device was observed at around 70°C which makes it useful for thermal switching applications. Addition of C60 to P3HT:PCBM blend gave a high value for RRESET/RSET in thermal switching. For bias switching, threshold voltage reduces to 1.4V from 25V with the addition of C60 to P3HT layer.

Electronic structure evolution in doping of fullerene (C60) by molybdenum trioxide

Molybdenum oxide doping of fullerene has been investigated using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), and inverse photoemission spectroscopy (IPES). The lowest unoccupied molecular orbital and the highest occupied molecular orbital (HOMO) can be observed directly with IPES and UPS. It is observed that the Fermi level position in fullerene is modified by molybdenum oxide doping, and the HOMO onset is shifted to less than 0.3 eV below the Fermi level. The energy level shift is found to saturate at doping ratio of 18%. Till this stage, the shift depends on the doping concentration in a semi-logarithmic scale, with a slope substantially higher than that of the traditional semiconductor theory. The XPS results indicate that charge transfer continues beyond the energy level shift saturation till the doping ratio reaches 66% as evidenced by the Mo5+ component. At higher doping concentration, there is more Mo6+ component, which indicates the saturation of the charge transfer between MoOx and C60.

In situ doping and crosslinking of fullerenes to form efficient and robust electron-transporting layers for polymer solar cells

Efficient electron-transporting layers (ETLs) with a stable conductive fullerene doped into a thermally crosslinkable fullerene matrix have been developed for inverted polymer solar cells (PSCs). The improved electrical conductivity and solvent resistance of these ETLs have significantly enhanced the performance of PSCs.