Abstract:A novel gas sensing platform involving a hybrid of reduced graphene oxide (rGO) sheets with unsubstituted copper phthalocyanine (CuPc) nanoflowers has been explored as a room temperature ppb level chemiresistive chlorine (Cl2) sensor with a detection limit as low as 1.97 ppb.
“…The very weak absorption peaks at 1627 cm −1 corresponding to the C=C group suggest the presence of organic materials in the samples used as binders 41 . The absorption peaks seen at 1237 and 1737 cm −1 for the green pigment of sample A are consistent with the C–N and N–H stretching modes of copper phthalocyanine 42,43 . Altogether, these FTIR results are consistent with our findings from Raman spectroscopy.Figure 7Fourier transform infrared (FTIR) spectra for selected pigments present in Jama-Coaque pottery.…”
Ecuadorian pottery is renowned for its beauty and the particularly rich colour of its pigments. However, a major challenge for art historians is the proper assessment of the provenance of individual pieces due to their lack of archaeological context. Of particular interest is the Jama-Coaque culture, which produced fascinating anthropomorphic and zoomorphic pottery from ca. 240 B.C. until the Spanish Conquest of 1532 A.D. in the coastal region of Ecuador. Using a combination of microscopic and spectroscopic techniques, i.e., transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), energy-dispersive x-ray spectroscopy (EDX), and scanning electron microscopy (SEM); we are able to characterize these pieces. We have found several kinds of iron-oxide based nanostructures in all the colour pigments we investigated for the Jama-Coaque culture, suggesting the same unique volcanic source material was used for their clay. Such nanostructures were absent from the pigment samples studied from other contemporary coastal-Ecuadorian cultures, i.e., the Tumaco-La Tolita and Bahía cultures. In the yellow pigments of goethite we find carbon nanofibres, indicating these pigments were subjected to a thermal treatment. Finally, in the blue, green, and black pigments we detect modern pigments (phthalocyanine blue, lithopone, and titanium white), suggesting modern restoration. Our results demonstrate the power of TEM, Raman, FTIR, EDX, and SEM archaeometric techniques for characterizing pieces without a clear archaeological context. Furthermore, the characterization of nanostructures present in such pieces could be used as a possible fingerprint for a provenance study.
“…The very weak absorption peaks at 1627 cm −1 corresponding to the C=C group suggest the presence of organic materials in the samples used as binders 41 . The absorption peaks seen at 1237 and 1737 cm −1 for the green pigment of sample A are consistent with the C–N and N–H stretching modes of copper phthalocyanine 42,43 . Altogether, these FTIR results are consistent with our findings from Raman spectroscopy.Figure 7Fourier transform infrared (FTIR) spectra for selected pigments present in Jama-Coaque pottery.…”
Ecuadorian pottery is renowned for its beauty and the particularly rich colour of its pigments. However, a major challenge for art historians is the proper assessment of the provenance of individual pieces due to their lack of archaeological context. Of particular interest is the Jama-Coaque culture, which produced fascinating anthropomorphic and zoomorphic pottery from ca. 240 B.C. until the Spanish Conquest of 1532 A.D. in the coastal region of Ecuador. Using a combination of microscopic and spectroscopic techniques, i.e., transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), energy-dispersive x-ray spectroscopy (EDX), and scanning electron microscopy (SEM); we are able to characterize these pieces. We have found several kinds of iron-oxide based nanostructures in all the colour pigments we investigated for the Jama-Coaque culture, suggesting the same unique volcanic source material was used for their clay. Such nanostructures were absent from the pigment samples studied from other contemporary coastal-Ecuadorian cultures, i.e., the Tumaco-La Tolita and Bahía cultures. In the yellow pigments of goethite we find carbon nanofibres, indicating these pigments were subjected to a thermal treatment. Finally, in the blue, green, and black pigments we detect modern pigments (phthalocyanine blue, lithopone, and titanium white), suggesting modern restoration. Our results demonstrate the power of TEM, Raman, FTIR, EDX, and SEM archaeometric techniques for characterizing pieces without a clear archaeological context. Furthermore, the characterization of nanostructures present in such pieces could be used as a possible fingerprint for a provenance study.
“…A selective room temperature chemiresistor with a ppb limit of detection for Cl 2 was fabricated through the functionalization of rGO with CuPc nanoflowers ( Figure 6 a). 23 Functionalization of rGO was carried out by mixing CuPc powder and GO in DMF, followed by hydrazine reduction. Structural and spectroscopic studies revealed that CuPc islands grow uniformly in a network of nanoflowers lying parallel to the rGO surface.…”
Section: Hybrids Based On Reduced
Graphene Oxide/metallophthalocyaninmentioning
confidence: 99%
“…(c) Conductance–time plots for different doses of Cl 2 . Adapted with permission from ref ( 23 ). Copyright 2017, Royal Society of Chemistry.…”
Section: Hybrids Based On Reduced
Graphene Oxide/metallophthalocyaninmentioning
Environmental
monitoring through gas sensors is paramount for the
safety and security of industrial workers and for ecological protection.
Graphene is among the most promising materials considered for next-generation
gas sensing due to its properties such as mechanical strength and
flexibility, high surface-to-volume ratio, large conductivity, and
low electrical noise. While gas sensors based on graphene devices
have already demonstrated high sensitivity, one of the most important
figures of merit, selectivity, remains a challenge. In the past few
years, however, surface functionalization emerged as a potential route
to achieve selectivity. This review surveys the recent advances in
the fabrication and characterization of graphene and reduced graphene
oxide gas sensors chemically functionalized with aromatic molecules
and polymers with the goal of improving selectivity toward specific
gases as well as overall sensor performance.
“…The sensor detection limit was measured to be 1.97 ppb at room temperature. (80) The physisorption of Cl 2 molecules occurred on the central metal ion present on the grains of CuPc-decorated rGO. Table 1 shows the sensing responses of several graphene-based gas sensors for some toxic gases.…”
Graphene and chemically modified graphene can be fabricated via numerous routes each with its own merits concerning ease of processability, cost-effectiveness for large-scale production, and also health and safety. One of the promising applications of graphene-based composites is gas sensing, which is mainly useful for environmental monitoring. We review some of the significant findings on graphene-based sensing materials for the detection of organic vapors, toxic gases, and chemical warfare agent simulants using an electrochemical method. Electrochemical sensing can be performed by inducing interactions between gas molecules and a graphene layer, such as charge transfer that gives a change in an electrical signal. The intrinsic properties of graphene and its role in some gas sensing applications will be discussed. Graphene and graphene oxide (GO) work as continuous conductive networks with a large number of surface adsorption sites for many gas molecules. Hybrid graphene devices incorporate semiconductors, metals, and molecular binders to enhance the capabilities of solidstate gas sensors. This article also addresses current approaches to the commercialization of graphene-based gas sensors.
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