**4. Doped graphene from asphaltene**

#### **4.1. Introduction to doped graphene applications**

The electronic and magnetic properties of graphene can be modified through combined transition-metal (TM) and nitrogen decoration of vacancies. Additional modes of functionalization that are currently being explored for a wide range of applications in nanoelectronics [36–38], spintronics [39] and electrocatalysts [40]. Researchers previously discovered that TMs bind to graphene strongly in a porphyrin ring coordinated by four nitrogens [41]. The stability in the presence of the defects associated with TMs can be attributed to the reduced electrostatic repulsion between nitrogen lone-pair electrons due to the hybridization between N and TM. Results from DTF studies have predicted these types of structures to be particularly promising candidates for graphene-based ferromagnets, which could find applications in nanoelectronics and nanomagnetism.

Graphene-type molecules, typically large polycyclic aromatic hydrocarbons (PAHs), have gained enormous interest because of their unique self-organization behavior and promising electronic properties for applications in organic electronics [42]. Asphaltene is a part of crude oils that contain a large number of structures, specifically high molecular weight bonded aromatic hydrocarbons components with hetero-atoms. Several metals (e.g., Ni, V, Fe, Al, Na, Ca, and Mg) shown to accumulate in the asphaltenes fraction of crude oil, typically in concentrations less than 1% w/w [43–45]. Vanadium and nickel, the most abundant of the trace metals, present mainly as chelated porphyrin compounds, and they linked to catalyst poisoning during upgrading of heavy oils [46, 47]. The concentrations of other trace metals not bound in porphyrin structures (e.g., Fe, Al, Na, Ca, and Mg) indicated to change in deposits as a function of well depth [48], and among sub fractions of asphaltene.

and oxygen from the system before growth. The use of a turbo pump also allowed for the system to reach pressures low enough (below 10−5 Torr) to operate a residual gas analyzer (RGA) instrument. In a typical growth, the sample was loaded into the furnace and allowed to pump

Raman was taken using Witec Alpha 300 micro-Raman confocal microscope after graphene

taken using a FEI Quanta 650 SEM equipped with Bruker EDX system for chemical analysis. Optical Microscope images of asphaltenes were taken on copper foils before and after growth. Transfers were performed by spin coating polymer, dissolving copper foil and transferring

Conditions for graphene growth were applied for all experiments. The resulting averaged Raman from all experiments show heavy carbonization and some graphitization of the solid carbon source. We were able to find metals in more than one sample of the post growth heptane extracted asphaltene. When drop coating was used for application before the growth process, the Raman from **Figure 6** indicates mostly carbon with some graphitization. Only

/Si wafers. Scanning Electron Microscope (SEM) Images were

Novel Applications with Asphaltene Electronic Structure http://dx.doi.org/10.5772/intechopen.78379 51

/Si wafers. Zeiss Axiovert 100A Light Microscope was used to take images of

down using the turbo pump for 2 hours prior to heating and gas flow (**Figure 5**).

**Experiment Temperature [°C] Time [min] Material Gas** 1050 5 C7-spin coated H (10 ccm) 1050 5 C7-drop coated H (10 ccm) 1050 5 Synthetic H (10 ccm)

**Table 4.** Experimental conditions and parameters and (above) figure of furnace used in experiment.

had been transferred to SiO2

**4.2. Single-layer asphaltene**

asphaltenes before and after growth.

**Figure 5.** CVD set-up at the J.J. Pickle Research Center Austin, TX [50].

graphene to SiO2

Graphene produced from chemical vapor deposition is viable for use in technologies such as touch screens, sensors, transistors, novel optical/electronic/photonic devices such as IR cameras, radiation shielding and camera lenses. Because they are expected to induce novel magnetic and superconducting behavior, TM adatoms and graphene are a topic of great interest are expected to induce novel magnetic and superconducting behavior. Because of this interest, there have been extensive theoretical studies but the experimental exploration of TM/graphene systems is very limited. Graphene with Boron and Nitrogen (BCN) is a sought after material due to the fact that graphene has no band gap [49]. Graphene in its single crystal form is a conductor, not a semi-conductor, so while it has amazing properties sought after by so many researchers, it has yet to make a significant impact on electronic industries for this reason. BCN is currently the subject of doped graphene research because it can be introduced by vapor. In contrast, TMs cannot be introduced by vapor. Even if they could be introduced at high temperatures, it has been determined that they would not be stable in an in-plan configuration due to the high differences in energy between TMs and carbon. Boron and Nitrogen both neighbor carbon on the periodic table and do not have a large differences in electron structure. As a carbon source, asphaltene is generated from waste crude oils and remains unsuitable for hydrocracking because of the presence of TMs. This study attempts to utilize that waste as a valuable source of metalloporphyrins for placing TMs doping graphene materials.

Asphaltene materials were extracted from crude using different n-alkanes and dissolved in toluene for deposition. Asphaltene/toluene (1 mg/ml) solutions were then deposited using drop coating onto previously prepared copper foil and experiments proceeded according to **Table 4**. Experiment 1 deposited asphaltene onto copper using spin coating. A 4 inch tube furnace was used to anneal the material under a reducing environment (H2 ). The system was equipped with a turbo pump with a direct line-of-sight to the sample and the substrate and allowed for base pressures below 10−8 Torr. A turbo pump was used and all the flanges on the high vacuum side of the system were constructed with conflat flanges; capable of achieving ultra-high vacuum (UHV). Reaching low background pressures allowed the removal of residual gasses like water


**Table 4.** Experimental conditions and parameters and (above) figure of furnace used in experiment.

and oxygen from the system before growth. The use of a turbo pump also allowed for the system to reach pressures low enough (below 10−5 Torr) to operate a residual gas analyzer (RGA) instrument. In a typical growth, the sample was loaded into the furnace and allowed to pump down using the turbo pump for 2 hours prior to heating and gas flow (**Figure 5**).

Raman was taken using Witec Alpha 300 micro-Raman confocal microscope after graphene had been transferred to SiO2 /Si wafers. Scanning Electron Microscope (SEM) Images were taken using a FEI Quanta 650 SEM equipped with Bruker EDX system for chemical analysis. Optical Microscope images of asphaltenes were taken on copper foils before and after growth. Transfers were performed by spin coating polymer, dissolving copper foil and transferring graphene to SiO2 /Si wafers. Zeiss Axiovert 100A Light Microscope was used to take images of asphaltenes before and after growth.

#### **4.2. Single-layer asphaltene**

electrostatic repulsion between nitrogen lone-pair electrons due to the hybridization between N and TM. Results from DTF studies have predicted these types of structures to be particularly promising candidates for graphene-based ferromagnets, which could find applications

Graphene-type molecules, typically large polycyclic aromatic hydrocarbons (PAHs), have gained enormous interest because of their unique self-organization behavior and promising electronic properties for applications in organic electronics [42]. Asphaltene is a part of crude oils that contain a large number of structures, specifically high molecular weight bonded aromatic hydrocarbons components with hetero-atoms. Several metals (e.g., Ni, V, Fe, Al, Na, Ca, and Mg) shown to accumulate in the asphaltenes fraction of crude oil, typically in concentrations less than 1% w/w [43–45]. Vanadium and nickel, the most abundant of the trace metals, present mainly as chelated porphyrin compounds, and they linked to catalyst poisoning during upgrading of heavy oils [46, 47]. The concentrations of other trace metals not bound in porphyrin structures (e.g., Fe, Al, Na, Ca, and Mg) indicated to change in deposits as a

Graphene produced from chemical vapor deposition is viable for use in technologies such as touch screens, sensors, transistors, novel optical/electronic/photonic devices such as IR cameras, radiation shielding and camera lenses. Because they are expected to induce novel magnetic and superconducting behavior, TM adatoms and graphene are a topic of great interest are expected to induce novel magnetic and superconducting behavior. Because of this interest, there have been extensive theoretical studies but the experimental exploration of TM/graphene systems is very limited. Graphene with Boron and Nitrogen (BCN) is a sought after material due to the fact that graphene has no band gap [49]. Graphene in its single crystal form is a conductor, not a semi-conductor, so while it has amazing properties sought after by so many researchers, it has yet to make a significant impact on electronic industries for this reason. BCN is currently the subject of doped graphene research because it can be introduced by vapor. In contrast, TMs cannot be introduced by vapor. Even if they could be introduced at high temperatures, it has been determined that they would not be stable in an in-plan configuration due to the high differences in energy between TMs and carbon. Boron and Nitrogen both neighbor carbon on the periodic table and do not have a large differences in electron structure. As a carbon source, asphaltene is generated from waste crude oils and remains unsuitable for hydrocracking because of the presence of TMs. This study attempts to utilize that waste as a

valuable source of metalloporphyrins for placing TMs doping graphene materials.

used to anneal the material under a reducing environment (H2

Asphaltene materials were extracted from crude using different n-alkanes and dissolved in toluene for deposition. Asphaltene/toluene (1 mg/ml) solutions were then deposited using drop coating onto previously prepared copper foil and experiments proceeded according to **Table 4**. Experiment 1 deposited asphaltene onto copper using spin coating. A 4 inch tube furnace was

a turbo pump with a direct line-of-sight to the sample and the substrate and allowed for base pressures below 10−8 Torr. A turbo pump was used and all the flanges on the high vacuum side of the system were constructed with conflat flanges; capable of achieving ultra-high vacuum (UHV). Reaching low background pressures allowed the removal of residual gasses like water

). The system was equipped with

function of well depth [48], and among sub fractions of asphaltene.

in nanoelectronics and nanomagnetism.

50 Modified Asphalt

Conditions for graphene growth were applied for all experiments. The resulting averaged Raman from all experiments show heavy carbonization and some graphitization of the solid carbon source. We were able to find metals in more than one sample of the post growth heptane extracted asphaltene. When drop coating was used for application before the growth process, the Raman from **Figure 6** indicates mostly carbon with some graphitization. Only

**Figure 5.** CVD set-up at the J.J. Pickle Research Center Austin, TX [50].

**Figure 6.** Raman summary of experiment 1, 2 & 3.

experiment 1 exhibited the ratio of (> 2:1) 2D to G and D peaks that would indicate the presence of quality graphene rather than sp2 hybridized carbon.

Metals identified in post growth samples from experiment 1 and 2 included Al, Fe, Zr and adatoms included sulfur. Electron Diffraction X-ray (EDX) analysis was taken of the copper foil before any etching in **Figure 7** and foil which had been sonicated in acetone before applying asphaltenes shows no metals or adatoms present before growth indicating that metals and adatoms indeed came from asphaltene samples. After growth, EDX spectra taken of sample from Experiment 1 show the presence of Aluminum and Iron.

To further study asphaltene adatoms, EDX elemental analysis was taken of synthetic asphaltene containing no metals applied to copper foil. Needless to say from data in **Figure 8** no TM or adatoms could be found present after growth.

Images taken using optical microscope **Figure 9** show copper coated with heptane extracted asphaltenes before and after Experiment 1 growth. There are clustered discotic structures before growth and curiously there are areas after growth that show clearly more than a few layers graphitized **Figure 10**. There are areas that can be seen where copper can be seen as clear orange from underneath sheets of graphitized carbon in **Figure 9(c)** and **(d)**.

form is a conductor, not a semi-conductor, so while it has amazing properties sought after by so many researchers, it has yet to make a significant impact on electronic industries for this reason. BCN is currently being researched because it can be introduced by vapor. In contrast, TMs cannot be introduced by vapor. Even if they could be introduced at high temperatures, it has been determined that they would not be stable in an in-plan configuration due to the high differences in energy between TMs and carbon. Boron and Nitrogen both neighbor carbon on the periodic table and do not have a large difference in electron structure. Our carbon source generated from waste crude oils is unsuitable for hydrocracking because of the presence of TMs. We were able to utilize that waste as a valuable source of metalloporphyrins for placing TMs directly inside the graphene lattice.

**Figure 8.** EDX (left) copper with drop coated synthetic asphaltene (right) after growth.

**Figure 7.** EDX analysis (top left) of copper foil sonicated in acetone before application of solid carbon source with corresponding SEM image (bottom left) EDX elemental analysis respectively (top right) from SEM section (bottom right)

Novel Applications with Asphaltene Electronic Structure http://dx.doi.org/10.5772/intechopen.78379 53

from asphaltene extracted using heptane in Experiment 1.

#### **4.3. Summary**

Because they are expected to induce novel magnetic and superconducting behavior, TM adatoms and graphene are a topic of great interest. There have been extensive theoretical studies because of these interesting properties but the experimental exploration of TM/ graphene systems is very limited. Graphene with Boron and Nitrogen (BCN) is a sought after material due to the fact that graphene has no band gap. Graphene in its single crystal

Novel Applications with Asphaltene Electronic Structure http://dx.doi.org/10.5772/intechopen.78379 53

**Figure 7.** EDX analysis (top left) of copper foil sonicated in acetone before application of solid carbon source with corresponding SEM image (bottom left) EDX elemental analysis respectively (top right) from SEM section (bottom right) from asphaltene extracted using heptane in Experiment 1.

**Figure 8.** EDX (left) copper with drop coated synthetic asphaltene (right) after growth.

experiment 1 exhibited the ratio of (> 2:1) 2D to G and D peaks that would indicate the pres-

Metals identified in post growth samples from experiment 1 and 2 included Al, Fe, Zr and adatoms included sulfur. Electron Diffraction X-ray (EDX) analysis was taken of the copper foil before any etching in **Figure 7** and foil which had been sonicated in acetone before applying asphaltenes shows no metals or adatoms present before growth indicating that metals and adatoms indeed came from asphaltene samples. After growth, EDX spectra taken of sample

To further study asphaltene adatoms, EDX elemental analysis was taken of synthetic asphaltene containing no metals applied to copper foil. Needless to say from data in **Figure 8** no TM

Images taken using optical microscope **Figure 9** show copper coated with heptane extracted asphaltenes before and after Experiment 1 growth. There are clustered discotic structures before growth and curiously there are areas after growth that show clearly more than a few layers graphitized **Figure 10**. There are areas that can be seen where copper can be seen as

Because they are expected to induce novel magnetic and superconducting behavior, TM adatoms and graphene are a topic of great interest. There have been extensive theoretical studies because of these interesting properties but the experimental exploration of TM/ graphene systems is very limited. Graphene with Boron and Nitrogen (BCN) is a sought after material due to the fact that graphene has no band gap. Graphene in its single crystal

clear orange from underneath sheets of graphitized carbon in **Figure 9(c)** and **(d)**.

hybridized carbon.

ence of quality graphene rather than sp2

**Figure 6.** Raman summary of experiment 1, 2 & 3.

52 Modified Asphalt

from Experiment 1 show the presence of Aluminum and Iron.

or adatoms could be found present after growth.

**4.3. Summary**

form is a conductor, not a semi-conductor, so while it has amazing properties sought after by so many researchers, it has yet to make a significant impact on electronic industries for this reason. BCN is currently being researched because it can be introduced by vapor. In contrast, TMs cannot be introduced by vapor. Even if they could be introduced at high temperatures, it has been determined that they would not be stable in an in-plan configuration due to the high differences in energy between TMs and carbon. Boron and Nitrogen both neighbor carbon on the periodic table and do not have a large difference in electron structure. Our carbon source generated from waste crude oils is unsuitable for hydrocracking because of the presence of TMs. We were able to utilize that waste as a valuable source of metalloporphyrins for placing TMs directly inside the graphene lattice.

The results demonstrated in these works illustrate the use of asphaltene as a light-harvesting active molecular dye effectively in dye sensitized solar cells for application in the field of organic photovoltaics. Higher-power conversion efficiencies can be achieved by further optimizing the device structure. In addition, they also show asphaltene as a promising candidate for doping multi-layer and potentially single layer graphene for future novel nanoscale mag-

Novel Applications with Asphaltene Electronic Structure http://dx.doi.org/10.5772/intechopen.78379 55

We would like to acknowledgeDr. Harry Chou's assistance with graphene growth and characterization in Section 4. Doped Graphene from asphaltene at The University of Texas (Austin, TX). Thanks To Dr. Carl Magnuson for assistance and instruction on tube furnace

1 Materials Research and Technology Institute, The University of Texas at El Paso, TX, USA

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2 Department of Chemistry, The University of Texas at El Paso, El Paso, TX, USA

netic or optoelectronic uses.

**Acknowledgements**

construction and apparatus.

and Russell R. Chianelli1,2\*

\*Address all correspondence to: chianell@utep.edu

**Author details**

Eva M. Deemer1

**References**

10.1002/anie.200604203

10.1126/science.271.5256.1705

**Figure 9.** Optical microscope images of heptane asphaltene on copper foil from experiments before (a,b) and after growth (c,d).

**Figure 10.** Optical microscope image of experiment 1 transferred to SiO2/Si wafer with rips and wrinkles (left) compared to OM image of a graphene sheet (purple) on SiO2 /Si wafer (pink). Arrows show wrinkles and tears in the material (right). (graphene provided courtesy Ruoff group at UT).
