Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes

Navneet Soin; Sekhar C. Ray; Sweety Sarma; Debarati Mazumder; Surbhi Sharma; Yu Fu Wang; Way Faung Pong; Susanta Sinha Roy; André M. Strydom

doi:10.1021/acs.jpcc.7b01645

Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes

Navneet Soin
, Sekhar C. Ray
, Sweety Sarma
, Debarati Mazumder
, Surbhi Sharma
, Yu Fu Wang
, Way Faung Pong
, Susanta Sinha Roy
, André M. Strydom

Research output: Contribution to journal › Article › peer-review

29 Citations (Scopus)

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Abstract

In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N ₂ treatment led to higher N-doping levels in the FLG (4.06 atomic %) as compared to the ECR process (2.18 atomic %), the ferromagnetic behavior of the ECR FLG (118.62 × 10 ^-4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10 ^-4 emu/g) and pristine graphene (3.47 × 10 ^-4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp ² -type nitrogen moieties, the rf-PECVD process led to the formation of sp ³ -coordinated nitrogen functionalities, as confirmed through Raman measurements. The samples were further characterized using X-ray absorption near-edge spectroscopy (XANES), and X-ray and ultraviolet photoelectron spectroscopies revealed an increased electronic density of states and a significantly higher concentration of pyrrolic groups in the rf-PECVD samples. Because of the formation of reactive edge structures and pyridinic nitrogen moieties, the ECR-functionalized FLG samples exhibited highest saturation magnetization behavior with the lowest field hysteretic features. In comparison, the rf-PECVD samples displayed the lowest saturation magnetization owing to the disappearance of magnetic edge states and formation of stable nonradical-type defects in the pyrrole type structures. Our experimental results thus provide new evidence regarding the control of the magnetic and electronic properties of few-layered graphene nanoflakes through control of the plasma-processing route.

Original language	English
Pages (from-to)	14073-14082
Number of pages	10
Journal	Journal Of Physical Chemistry C
Volume	121
Issue number	26
DOIs	https://doi.org/10.1021/acs.jpcc.7b01645
Publication status	Published (in print/issue) - 7 Jun 2017

Funding

S.C.R. and S.S. (UNISA) gratefully acknowledge the financial support received from the National Research Foundation (NRF), South Africa (Grants EQP13091742446 and PDTWAS150813137166). A.M.S. thanks SA-NRF (93549) and the FRC and URC of University of Johannesburg for financial assistance. The authors also thank D. Britz for his help with magnetic property characterizations.

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Soin N Tuning the electronic and magnetic properties of nitrogen functionalized few layered graphene nanoflakesAuthor Accepted Manuscript, 1.98 MB

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@article{de5731fb7b2b4de7ae08766c7dfc2246,

title = "Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes",

abstract = " In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N 2 treatment led to higher N-doping levels in the FLG (4.06 atomic \%) as compared to the ECR process (2.18 atomic \%), the ferromagnetic behavior of the ECR FLG (118.62 × 10 -4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10 -4 emu/g) and pristine graphene (3.47 × 10 -4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp 2 -type nitrogen moieties, the rf-PECVD process led to the formation of sp 3 -coordinated nitrogen functionalities, as confirmed through Raman measurements. The samples were further characterized using X-ray absorption near-edge spectroscopy (XANES), and X-ray and ultraviolet photoelectron spectroscopies revealed an increased electronic density of states and a significantly higher concentration of pyrrolic groups in the rf-PECVD samples. Because of the formation of reactive edge structures and pyridinic nitrogen moieties, the ECR-functionalized FLG samples exhibited highest saturation magnetization behavior with the lowest field hysteretic features. In comparison, the rf-PECVD samples displayed the lowest saturation magnetization owing to the disappearance of magnetic edge states and formation of stable nonradical-type defects in the pyrrole type structures. Our experimental results thus provide new evidence regarding the control of the magnetic and electronic properties of few-layered graphene nanoflakes through control of the plasma-processing route. ",

author = "Navneet Soin and Ray, \{Sekhar C.\} and Sweety Sarma and Debarati Mazumder and Surbhi Sharma and Wang, \{Yu Fu\} and Pong, \{Way Faung\} and Roy, \{Susanta Sinha\} and Strydom, \{Andr{\'e} M.\}",

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doi = "10.1021/acs.jpcc.7b01645",

language = "English",

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T1 - Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes

AU - Soin, Navneet

AU - Ray, Sekhar C.

AU - Sarma, Sweety

AU - Mazumder, Debarati

AU - Sharma, Surbhi

AU - Wang, Yu Fu

AU - Pong, Way Faung

AU - Roy, Susanta Sinha

AU - Strydom, André M.

PY - 2017/6/7

Y1 - 2017/6/7

N2 - In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N 2 treatment led to higher N-doping levels in the FLG (4.06 atomic %) as compared to the ECR process (2.18 atomic %), the ferromagnetic behavior of the ECR FLG (118.62 × 10 -4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10 -4 emu/g) and pristine graphene (3.47 × 10 -4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp 2 -type nitrogen moieties, the rf-PECVD process led to the formation of sp 3 -coordinated nitrogen functionalities, as confirmed through Raman measurements. The samples were further characterized using X-ray absorption near-edge spectroscopy (XANES), and X-ray and ultraviolet photoelectron spectroscopies revealed an increased electronic density of states and a significantly higher concentration of pyrrolic groups in the rf-PECVD samples. Because of the formation of reactive edge structures and pyridinic nitrogen moieties, the ECR-functionalized FLG samples exhibited highest saturation magnetization behavior with the lowest field hysteretic features. In comparison, the rf-PECVD samples displayed the lowest saturation magnetization owing to the disappearance of magnetic edge states and formation of stable nonradical-type defects in the pyrrole type structures. Our experimental results thus provide new evidence regarding the control of the magnetic and electronic properties of few-layered graphene nanoflakes through control of the plasma-processing route.

AB - In this article, we report the modification of the electronic and magnetic properties of few-layered graphene (FLG) nanoflakes by nitrogen functionalization carried out using radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) and electron cyclotron resonance (ECR) plasma processes. Even though the rf-PECVD N 2 treatment led to higher N-doping levels in the FLG (4.06 atomic %) as compared to the ECR process (2.18 atomic %), the ferromagnetic behavior of the ECR FLG (118.62 × 10 -4 emu/g) was significantly higher than that of the rf-PECVD FLG (0.39 × 10 -4 emu/g) and pristine graphene (3.47 × 10 -4 emu/g). Although both plasma processes introduce electron-donating N atoms into the graphene structure, distinct dominant nitrogen bonding configurations (pyridinic, pyrrolic) were observed for the two FLG types. Whereas the ECR plasma introduced more sp 2 -type nitrogen moieties, the rf-PECVD process led to the formation of sp 3 -coordinated nitrogen functionalities, as confirmed through Raman measurements. The samples were further characterized using X-ray absorption near-edge spectroscopy (XANES), and X-ray and ultraviolet photoelectron spectroscopies revealed an increased electronic density of states and a significantly higher concentration of pyrrolic groups in the rf-PECVD samples. Because of the formation of reactive edge structures and pyridinic nitrogen moieties, the ECR-functionalized FLG samples exhibited highest saturation magnetization behavior with the lowest field hysteretic features. In comparison, the rf-PECVD samples displayed the lowest saturation magnetization owing to the disappearance of magnetic edge states and formation of stable nonradical-type defects in the pyrrole type structures. Our experimental results thus provide new evidence regarding the control of the magnetic and electronic properties of few-layered graphene nanoflakes through control of the plasma-processing route.

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U2 - 10.1021/acs.jpcc.7b01645

DO - 10.1021/acs.jpcc.7b01645

M3 - Article

AN - SCOPUS:85024472846

SN - 1932-7447

VL - 121

SP - 14073

EP - 14082

JO - Journal Of Physical Chemistry C

JF - Journal Of Physical Chemistry C

IS - 26

ER -

Tuning the Electronic and Magnetic Properties of Nitrogen-Functionalized Few-Layered Graphene Nanoflakes

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