Graphene Nanoplatelets as a Solid Phase Extraction Sorbent for Analysis of Chlorophenols in Water

Sadanala, Krishna Chaitanya,Chung, Bong Chul The Korean Society for Applied Biological Chemistr 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.6

Graphene nanoplatelets are a novel class of carbon nanostructures. They possess an ultra high surface area, and thus have great potentials for the use as sorbent materials. We herein demonstrate the use of graphene nanoplatelets as an adsorbent material for solid-phase extraction. Surface compositions of graphene nanoplatelets were examined by X-ray photoelectron spectroscopy. Scanning electron and transmission electron microscopies were performed to elucidate the morphology of graphene nanoplatelets. Three chlorophenols, 3-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenols were selected as model analytes and extracted on a graphene nanoplatelets-packed solid-phase extraction cartridge, followed by elution with alkaline methanol. The extracted chlorophenols were identified and quantified by UV-vis spectrophotometer. Under the optimized experimental conditions, good linearity ($R^2$ >0.9969), recovery (95-103%), precision (<12%), and accuracy (< ${\pm}9$%) were achieved. The advantages of graphene nanoplatelets as solid phase extraction adsorbent, such as good reusability and no impact of sorbent drying, have been detailed. The present study proposes a useful method for water sample pretreatment and reveals the potential of graphene nanoplatelets as an excellent sorbent material in analytical processes.

Graphene Nanoplatelets as a Solid Phase Extraction Sorbent for Analysis of Chlorophenols in Water

Krishna Chaitanya Sadanala,정봉철 한국응용생명화학회 2013 Applied Biological Chemistry (Appl Biol Chem) Vol.56 No.6

Graphene nanoplatelets are a novel class of carbon nanostructures. They possess an ultra high surface area, and thus have great potentials for the use as sorbent materials. We herein demonstrate the use of graphene nanoplatelets as an adsorbent material for solid-phase extraction. Surface compositions of graphene nanoplatelets were examined by X-ray photoelectron spectroscopy. Scanning electron and transmission electron microscopies were performed to elucidate the morphology of graphene nanoplatelets. Three chlorophenols, 3-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenols were selected as model analytes and extracted on a graphene nanoplatelets-packed solid-phase extraction cartridge,followed by elution with alkaline methanol. The extracted chlorophenols were identified and quantified by UV-vis spectrophotometer. Under the optimized experimental conditions,good linearity (R2 >0.9969), recovery (95–103%), precision (<12%),and accuracy (<±9%) were achieved. The advantages of graphene nanoplatelets as solid phase extraction adsorbent, such as good reusability and no impact of sorbent drying, have been detailed. The present study proposes a useful method for water sample pretreatment and reveals the potential of graphene nanoplatelets as an excellent sorbent material in analytical processes.

Comparative study on the morphological properties of graphene nanoplatelets prepared by an oxidative and non-oxidative route

Jung-Chul An,Eun Jung Lee,So-Young Yoon,Seong-Young Lee,Yong-Jung Kim 한국탄소학회 2018 Carbon Letters Vol.26 No.-

Morphological differences in multi-layered graphene flakes or graphene nanoplatelets prepared by oxidative (rGO-NP, reduced graphene oxide-nanoplatelets) and non-oxidative (GIC-NP, graphite intercalation compound-nanoplatelets) routes were investigated with various analytical methods. Both types of NPs have similar specific surface areas but very different structural differences. Therefore, this study proposes an effective and simple method to identify structural differences in graphene-like allotropes. The adsorptive potential peaks of rGO-NP attained by the density functional theory method were found to be more scattered over the basal and non-basal regions than those of GIC-NP. Raman spectra and high resolution TEM images showed more distinctive crystallographic defects in the rGO-NP than in the GIC-NP. Because the R-ratio values of the edge and basal plane of the sample were maintained and relatively similar in the rGO-NP (0.944 for edge & 1.026 for basal), the discrepancy between those values in the GIC-NP were found to be much greater (0.918 for edge & 0.164 for basal). The electrical conductivity results showed a remarkable gap between the rGO-NP and GIC-NP attributed to their inherent morphological and crystallographic properties.

Edge-halogenated graphene nanoplatelets with F, Cl, or Br as electrocatalysts for all-vanadium redox flow batteries

Park, Minjoon,Jeon, In-Yup,Ryu, Jaechan,Jang, Haeseong,Back, Jong-Beom,Cho, Jaephil Elsevier 2016 Nano energy Vol.26 No.-

<P><B>Abstract</B></P> <P>The catalytic activity of V<SUP>2+</SUP>/V<SUP>3+</SUP> and VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox couples on the halogen-doped graphene nanoplatelets (F-, Cl-, and Br-GNPs) is studied by ball-milling graphite flakes with fluorine (F<SUB>2</SUB>), chlorine (Cl<SUB>2</SUB>), and bromine (Br<SUB>2</SUB>) molecules, respectively. Using the edge-selectively halogenated graphene materials with different edge exfoliation degrees, the vanadium redox reactions can be significantly facilitated by having abundant edge defects with large surface area in the order: Br-GNP>Cl-GNP>F-GNP. The influence of halogen functionalization on graphene nanoplatelets towards vanadium redox couples is further confirmed by stack-type vanadium redox flow batteries that demonstrates better cell performance than graphene nanoplatelets without dopant at the edges. Notably, the Br-GNP showed unique electrochemical performance of increased initial charge/discharge capacity and improved rate capability, respectively. It was found that halogen doping on graphene-based materials can promote vanadium redox reactions by creating effective active sites, and the electrocatalytic activity is dependent on edge exfoliation degree and well-preserved basal planes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Edge-halogenated graphene nanoplatelets for vanadium redox reactions was studied. </LI> <LI> Halogen doping on graphene-based materials can promote vanadium redox reactions. </LI> <LI> A large degree of edge exfoliation by Br facilitates mass transport of vanadium ions. </LI> <LI> Br-GNP catalyst leads to decrease of cell overpotentials in VRFBs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Highly sensitive and simultaneous detection of dopamine and uric acid at graphene nanoplatelet-modified fluorine-doped tin oxide electrode in the presence of ascorbic acid

Rahman, Md. Mahbubur,Lopa, Nasrin Siraj,Ju, Myung Jong,Lee, Jae-Joon Elsevier 2017 Journal of Electroanalytical Chemistry Vol.792 No.-

<P><B>Abstract</B></P> <P>We developed a graphene nanoplatelet-modified fluorine-doped tin oxide electrode (GNP/FTO) for the simultaneous detection of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) and investigated the interaction mechanisms of DA, UA, and AA with GNPs considering their charging states at different pH values. Owing to the unique structure and properties originating from the oxygen and nitrogen functional groups at the edges, GNPs showed high electrocatalytic activity for the electrochemical oxidations of AA, DA, and UA with peak-to-peak potential separations (Δ<I>E</I> <SUB> <I>P</I> </SUB>) between AA-DA and DA-UA of <I>ca</I>. 0.23 and 0.17V, respectively. These values are sufficiently high to allow the simultaneous detection of DA and UA without interference from AA. The highly sensitive and stable GNP/FTO sensor showed sensitivities of <I>ca</I>. 0.15±0.004 and 0.14±0.007μA/μM, respectively, with detection limits of <I>ca</I>. 0.22±0.009 and 0.28±0.009μM, respectively, for DA and UA. The sensor could detect DA and UA concentrations in human serum samples with excellent recoveries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> FTO was modified with graphene nanoplatelets (GNPs) by the e-spray method. </LI> <LI> Dopamine and uric acid were simultaneously detected with GNP/FTO without interference from ascorbic acid. </LI> <LI> Sensor allows low detection limits of 0.22 and 0.28μM for dopamine and uric acid, respectively. </LI> <LI> Sensor shows good stability and recoveries from human serum samples. </LI> <LI> The interaction mechanisms between dopamine, uric acid, and ascorbic acid with GNPs were discussed and verified. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Preparation of Kish graphite-based graphene nanoplatelets by GIC (graphite intercalation compound) via process

안정철,김헤정,홍익표 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.26 No.-

Several-micrometer-wide at a few-nanometer-thick graphene platelets were successfully prepared from Kish graphite by simple GIC (graphite intercalation compound) via exfoliation process. High crystalline Kish graphite flakes were recovered from the steelmaking by-product using the modified beneficiation process. Sulfuric acid was served as the functional intercalating agent in the GIC formation step. XRD results revealed the stable and clear first-stage state formed in the acid-intercalated GIC. Carbon content in the recovered Kish graphite was found to influence the average thickness of prepared graphene nanoplatelets. Larger Kish graphite flakes were also beneficial to produce thin graphene platelets with the average thickness of 5 nm.

Thermal and flame retardant properties of graphene nanoplatelet/phenolic foam/wood composite boards

한정인,송은지,김민지,김경훈,이영석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

In the architectural field, flame retardant properties are important factors in the safety aspect. In this study, graphene nanoplatelet (GnP)/phenolic foam (PF)/wood composite boards were fabricated with different GnP contents to investigate the effect of GnP on the flame retardant properties of wood-based composite board. Thermogravimetric analysis (TGA) was conducted under air and N₂ atmosphere to evaluate thermal properties. Flame retardant properties were investigated by limiting oxygen index (LOI) test. As a result, the initial decomposition temperature of composite board increased with the GnP content. The char yield also increased up to 22% when GnP was added, whereas char yield of pure wood board and PF was 1%, respectively. In addition, the LOI value of composite boards increased up to 8% compared to pure wood board. These results are attributed by higher char yield, which prevents contact with oxygen and delays the combustion of composite boards.

Preparation of Kish graphite-based graphene nanoplatelets by GIC (graphite intercalation compound) via process

An, J.C.,Kim, H.J.,Hong, I. Korean Society of Industrial and Engineering Chemi 2015 Journal of industrial and engineering chemistry Vol.26 No.-

Several-micrometer-wide at a few-nanometer-thick graphene platelets were successfully prepared from Kish graphite by simple GIC (graphite intercalation compound) via exfoliation process. High crystalline Kish graphite flakes were recovered from the steelmaking by-product using the modified beneficiation process. Sulfuric acid was served as the functional intercalating agent in the GIC formation step. XRD results revealed the stable and clear first-stage state formed in the acid-intercalated GIC. Carbon content in the recovered Kish graphite was found to influence the average thickness of prepared graphene nanoplatelets. Larger Kish graphite flakes were also beneficial to produce thin graphene platelets with the average thickness of 5nm.

Study of Interfacial Properties of Carbon Fiber Epoxy Matrix Composites Containing Graphene Nanoplatelets

Faizan S. Awan,Mohsin A. Fakhar,Laraib A. Khan,Tayyab Subhani 한국섬유공학회 2019 Fibers and polymers Vol.20 No.3

Two-dimensional functionalized graphene nanoplatelets were incorporated in carbon fiber epoxy matrixcomposites to prepare a novel class of hierarchical composites. The nanoplatelets were coated on the surface of fibers by electrophoretic deposition prior to the preparation of composites. Later the nanoplatelet-deposited fibers were impregnated with epoxy resin by a combination of hand layup and vacuum bagging process. The composites were characterized microstructurally by spectroscopy, and optical and electron microscopy. The mechanical characterization was performed by flexural and interlaminar shear tests. It was observed that nanoplatelets possessed different functional groups responsible for making interactions with epoxy and carbon fibers. The flexural strength of composites increased by ~41 %, flexural modulus by ~26 % while interlaminar shear strength increased by ~24 %. The observation of the fractured surfaces of composites provided qualitative evidences of the improved interfacial adhesion. The enhancement in the properties is attributed to hydrogen bonding and mechanical interlocking of nanoplatelets with carbon fibers and epoxy resin. Electron microscopy revealed the retention of nanoplatelets on carbon fibers after manufacturing the composites. Such hierarchical composites are ideal candidate materials for improved through-thickness properties especially for futuristic aerospace structural applications.

Magnetic filler alignment of single graphene nanoplatelets modified by Fe3O4 to improve the thermal conductivity of the epoxy composite

Seyed Foad Abbaspour,Mojtaba Kanvisi 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.122 No.-

In this paper, to improve the thermal conductivity of polymer composites, the epoxy matrix has beenfilled with single graphene nanoplatelets (SGNPs) modified by Fe3O4 magnetic nanoparticles. Fe3O4modified graphene nanoplatelets were aligned by the magnetic field tunnel method in the epoxy matrix. The highest alignment and controlled orientation of the nanoplatelets were achieved in different compositesamples. FT-IR and TEM tests were used to investigate the structure and characterization ofSGNP@Fe3O4 synthesized nanoparticles. A constant intensity magnetic field at different times was usedto control the nanoplatelets’ orientation in the epoxy matrix. This controlled orientation and high alignmentof the fillers lead to an increase in the thermal conductivity of the composite. The thermal conductivityof the EP/SGNP @Fe3O4 composite showed a 309% increase in high alignment compared to the nonalignedsamples.