Is Chemically Synthesized Graphene ‘Really’ a Unique Substrate for SERS and Fluorescence Quenching?

Sil, Shreekantha; Kuhar, Nikki; Acharya, S.; Umapathy, Siva

doi:10.1038/srep03336

Cited by 54 publications

(45 citation statements)

References 37 publications

(45 reference statements)

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“…S1) showed that HU-NaBH 4 existed primarily as large areas of stacked sheets, which is in contrast to the highly exfoliated wrinkled structures seen in HU-TRGO and HU-N 2 H 4 . This morphology is consistent with other studies, in which the surface areas of NaBH 4 -reduced RGOs are distinctly lower than that of hydrazine-reduced RGOs (20,(47)(48)(49). As a result, a large proportion of the Mn-based impurities in HU-NaBH 4 would have been sheathed in between these stacked sheets, rendering them surface-inaccessible and thus, leading to the greatly reduced catalytic effect observed.…”

Section: Resultssupporting

confidence: 91%

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Wong

Sofer²,

Kubešová

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

144

118

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The synthesis of graphene materials is typically carried out by oxidizing graphite to graphite oxide followed by a reduction process. Numerous methods exist for both the oxidation and reduction steps, which causes unpredictable contamination from metallic impurities into the final material. These impurities are known to have considerable impact on the properties of graphene materials. We synthesized several reduced graphene oxides from extremely pure graphite using several popular oxidation and reduction methods and tracked the concentrations of metallic impurities at each stage of synthesis. We show that different combinations of oxidation and reduction introduce varying types as well as amounts of metallic elements into the graphene materials, and their origin can be traced to impurities within the chemical reagents used during synthesis. These metallic impurities are able to alter the graphene materials' electrochemical properties significantly and have wide-reaching implications on the potential applications of graphene materials.

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Section: Resultssupporting

confidence: 91%

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Wong

Sofer²,

Kubešová

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

144

118

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“…48,49 Besides graphene, SERS substrates using graphene derivative covered Au or Ag films were also studied. 28,50 Figure 6c 51 shows that octahedral Ag @ GO gives the strongest enhancement of 9.5 × 10 5 , stronger than 6.9 × 10 5 for a Ag nanocube on GO and 1.0 × 10 5 for a Ag nanosphere on GO. In future research, more promising structures are expected for specific applications.…”

Section: Gers Meets With the Metal Substratementioning

confidence: 99%

Lighting Up the Raman Signal of Molecules in the Vicinity of Graphene Related Materials

et al. 2015

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Surface enhanced Raman scattering (SERS) is a popular technique to detect the molecules with high selectivity and sensitivity. It has been developed for 40 years, and many reviews have been published to summarize the progress in SERS. Nevertheless, how to make the SERS signals repeatable and quantitative and how to have deeper understanding of the chemical enhancement mechanism are two big challenges. A strategy to target these issues is to develop a Raman enhancement substrate that is flat and nonmetal to replace the conventional rough and metal SERS substrate. At the same time, the newly developed substrate should have a strong interaction with the adsorbate molecules to guarantee strong chemical enhancement. The flatness of the surface allows better control of the molecular distribution and configuration, while the nonmetal surface avoids disturbance of the electromagnetic mechanism. Recently, graphene and other two-dimensional (2D) materials, which have an ideal flat surface and strong chemical interaction with plenty of organic molecules, were developed to be used as Raman enhancement substrates, which can light up the Raman signals of the molecules, and these substrates were demonstrated to be a promising for microspecies or trace species detection. This effect was named "graphene enhanced Raman scattering (GERS)". The GERS technique offers significant advantages for studying molecular vibrations due to the ultraflat and chemically inert 2D surfaces, which are newly available, especially in developing a quantitative and repeatable signal enhancement technique, complementary to SERS. Moreover, GERS is a chemical mechanism dominated effect, which offers a valuable model to study the details of the chemical mechanism. In this Account, we summarize the systematic studies exploring the character of GERS. In addition, as a practical technique, the combination of GERS with a metal substrate incorporates the advantages from both conventional SERS and GERS. The introduction of graphene to the Raman enhancement substrate extended SERS applications in a more controllable and quantitative way. Looking to the future, we expect the combination of the SERS concept with the GERS technology to lead to the solution of some important issues in chemical dynamics and in biological processes monitoring.

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“…2,7,8 The origin of GERS is still controversial since the electromagnetic enhancement (EE), which is mostly responsible of the high SERS on metallic surfaces, is not as effective on graphene because of the smooth surface and plasmon excitation in the terahertz region. 10 Other mechanisms have been therefore supposed to be the source of GERS, such as chemical enhancement (CE), fluorescence quenching 9 and efficient adsorption. 10 Graphene has a flat and smooth surface particularly suitable for homogeneous deposition of organic molecules, such as aromatics, which can interact through π-π bonding interactions capable of promoting charge transfer and therefore CE.…”

mentioning

confidence: 99%

“…10 Other mechanisms have been therefore supposed to be the source of GERS, such as chemical enhancement (CE), fluorescence quenching 9 and efficient adsorption. 10 Graphene has a flat and smooth surface particularly suitable for homogeneous deposition of organic molecules, such as aromatics, which can interact through π-π bonding interactions capable of promoting charge transfer and therefore CE. On the other hand, it has been demonstrated that graphene is not the only carbon-based platform for the enhancement of Raman signals, and various materials such as graphene oxide, multi-walled carbon nanotubes, graphite and activated carbon also exhibit Enhancement of Raman Scattering (ERS).…”

mentioning

confidence: 99%

“…The origin of such enhancement is, however, due to resonant effects and fluorescence quenching because of the efficient adsorption of the probe molecules on the different carbon surfaces. 10 The GERS enhancement factor (EF) is generally low and, to the best of our knowledge, it could range from 0.9 to 47 depending on the probe molecule and on the Raman mode used to calculate it. 2,16 The GERS EF covers only two orders of magnitude because the CE is mainly due to the charge transfer between graphene and the molecule to be detected, and it changes accordingly with the different Raman shifts generated by the molecular probe.…”

mentioning

confidence: 99%

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Introducing Ti-GERS: Raman Scattering Enhancement in Graphene-Mesoporous Titania Films

Carboni

Lasio

Loche

et al. 2015

J. Phys. Chem. Lett.

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Graphene sheets increase the Raman signal through a chemical enhancement mechanism which gives rise to graphene-mediated enhanced Raman scattering (GERS).The low enhancement factor and the surface available for analysis are, however, a limitation on the application of graphene-mediated enhanced Raman scattering (ERS).We have, therefore, developed a new GERS platform, which is based on mesoporous ordered films made of titania anatase containing dispersed sheets of exfoliated graphene. The analytical enhancement factor has revealed that the combination of titania and graphene produces a significant increase in GERS response using Rhodamine 6G as molecular probe. This is a new effect, which we have defined as Ti-GERS (Titania-induced Graphene-mediated ERS) and is attributed to synergic interfacial interactions between graphene sheets and titania at the nanocrystals edges within the nanocomposite. In the future, the Ti-GERS effect is expected to foster a

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Is Chemically Synthesized Graphene ‘Really’ a Unique Substrate for SERS and Fluorescence Quenching?

Cited by 54 publications

References 37 publications

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Lighting Up the Raman Signal of Molecules in the Vicinity of Graphene Related Materials

Introducing Ti-GERS: Raman Scattering Enhancement in Graphene-Mesoporous Titania Films

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