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Faisal Shahzad,Aamir Iqbal,샤비,황석원,구종민 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.79 No.-
Herein, we demonstrate the selective sensing of Dopamine (DA), an important neurotransmitter, by usingNafion-stabilized two-dimensional transition metal carbides (Ti3C2TxMXenes). Ti3C2Tx was deposited ona glassy carbon electrode followed by Nafion coating to achieve a robust sensitivity ( 3 nM), goodselectivity, wide detection window (0.015–10 mM), high stability, reproducibility, and outstandingrecoveries for DA detection in real samples. MXene-based biosensor exhibited much betterelectrochemical performance when compared with reduced graphene oxide-based biosensor undersimilar experimental conditions due to the MXenes good electrical conductivity and negatively chargedsurface which assisted in the selective and sensitive detection of DA.
Shahzad, Faisal,Iqbal, Aamir,Zaidi, Shabi Abbas,Hwang, Suk-Won,Koo, Chong Min Elsevier 2019 Journal of industrial and engineering chemistry Vol.79 No.-
<P><B>Abstract</B></P> <P>Herein, we demonstrate the selective sensing of Dopamine (DA), an important neurotransmitter, by using Nafion-stabilized two-dimensional transition metal carbides (Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> MXenes). Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> was deposited on a glassy carbon electrode followed by Nafion coating to achieve a robust sensitivity (∼3nM), good selectivity, wide detection window (0.015–10μM), high stability, reproducibility, and outstanding recoveries for DA detection in real samples. MXene-based biosensor exhibited much better electrochemical performance when compared with reduced graphene oxide-based biosensor under similar experimental conditions due to the MXenes good electrical conductivity and negatively charged surface which assisted in the selective and sensitive detection of DA.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Sulfur-doped graphene laminates for EMI shielding applications
Shahzad, Faisal,Kumar, Pradip,Yu, Seunggun,Lee, Seunghwan,Kim, Yoon-Hyun,Hong, Soon Man,Koo, Chong Min The Royal Society of Chemistry 2015 Journal of Materials Chemistry C Vol.3 No.38
<▼1><P>Herein, for the first time, we demonstrate that a laminated structure of sulfur-doped reduced graphene oxide (SrGO) provides significant potential for electromagnetic interference shielding applications.</P></▼1><▼2><P>Herein, for the first time, we demonstrate that a laminated structure of sulfur-doped reduced graphene oxide (SrGO) provides significant potential for electromagnetic interference shielding applications. In this study, SrGO was prepared through the reaction between graphene oxide and hydrogen disulfide (H2S) gas at elevated temperatures. The doping degree of S was controlled through varying the time and temperature of the reaction and the maximum doping content of 5.6 wt% was achieved. Because of the n-type doping contribution of the S atom to the doped graphene, SrGO laminate not only revealed a 47% larger electrical conductivity (75 S cm<SUP>−1</SUP>) than undoped reduced graphene oxide laminate (51 S cm<SUP>−1</SUP>) but also revealed 119% larger EMI shielding effectiveness (33.2 dB) than the undoped one (15.5 dB) at the same sample thickness.</P></▼2>
Sulfur doped graphene/polystyrene nanocomposites for electromagnetic interference shielding
Shahzad, Faisal,Yu, Seunggun,Kumar, Pradip,Lee, Jang-Woo,Kim, Yoon-Hyun,Hong, Soon Man,Koo, Chong Min Elsevier 2015 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.133 No.-
<P><B>Abstract</B></P> <P>In this paper, for the first time, we present a simple and straightforward method to improve not only electrical conductivity and complex permittivity but also electromagnetic interference (EMI) shielding effectiveness of reduced graphene oxide (rGO)/polystyrene (PS) nanocomposites through sulfur doping. Sulfur-doped reduced graphene oxide with thiophene-like structure (2.6at.% S), synthesized through a simple heating process of a mixture of graphene oxide and sulfur powder, revealed almost three times larger electrical conductivity (1095Sm<SUP>−1</SUP>) than undoped rGO (395Sm<SUP>−1</SUP>). The SrGO/PS nanocomposite showed not only 150% larger electrical conductivity and 50% larger complex permittivity, but also improved EMI shielding effectiveness (24.5dB) at a frequency of 18GHz than rGO/PS nanocomposite (21.4dB) at the same loading level of 7.5vol.%. Considering the simplicity and effectiveness of process, sulfur doping of graphene is expected to be used as a versatile method to improve EMI shielding efficiency of graphene/polymer nanocomposites.</P>
Shahzad, Faisal,Kumar, Pradip,Kim, Yoon-Hyun,Hong, Soon Man,Koo, Chong Min American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.14
<P>Electrically conductive thin carbon materials have attracted remarkable interest as a shielding material to mitigate the electromagnetic interference (EMI) produced by many telecommunication devices. Herein, we developed a sulfur-doped reduced graphene oxide (SrGO) with high electrical conductivity through using a novel biomass, mushroom-based sulfur compound (lenthionine) via a twostep thermal treatment. The resultant SrGO product exhibited excellent electrical conductivity of 311 S cm(-1), which is 52% larger than 205 S cm(-1) for undoped rGO. SrGO also exhibited an excellent EMI shielding effectiveness of 38.6 dB, which is 61% larger than 24.4 dB measured for undoped rGO. Analytical examinations indicate that a sulfur content of 1.95 atom % acts as n-type dopant, increasing electrical conductivity and, therefore, EMI shielding of doped graphene.</P>
Shahzad, Faisal,Zaidi, Shabi Abbas,Koo, Chong Min American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.28
<P>Doping with heteroatoms is a well-established method to tune the electronic properties and surface chemistry of graphene. Herein, we demonstrate the synthesis of a fluorine-doped reduced graphene oxide (FrGO) at low temperatures that offers multiple opportunities in applied fields. The as-synthesized FrGO product shows a better electrical conductivity of 750 S m(-1) than that of undoped rGO with an electrical conductivity of 195 S m(-1). To demonstrate the multifunctional applications of the as-synthesized FrGO, it was examined for electromagnetic interference shielding and electrochemical sensing of histamine as an important food biomarker. A laminate of FrGO delivered an EMI shielding effectiveness value of 22 dB in Ku band as compared with 11.2 dB for an rGO laminate with similar thickness. On the other hand, an FrGO modified sensor offered an excellent sensitivity (similar to 7 nM), wide detection range, and good selectivity in the presence of similar biomarkers. This performance originates from the better catalytic ability of FrGO as compared with rGO, where fluorine atoms play the role of catalytic active sites owing to their high electronegativity. The fluorination reaction also helps to improve the reduction degree of the chemically synthesized graphene, consequently enhancing the electrical conductivity, which is a prime requirement for increasing the electromagnetic and electrochemical properties of graphene.</P>