Different strategies for functionalization of carbon nanomaterial based sensing materials: State of the art

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Morphological characterizations of nanocomposites

The technique consisting in the superimposition of layers of several tens of nm up to a final film thickness of some µm showed in Figure 29 (a), has proved to allow the building of hierarchically structured transducers, which presents the advantage of bridging the original nanostructures developed by self assembly of RGO with CD, to the macroscopic parameter to measure (resistance variation). Atomic force microscopy (AFM) can give a good idea of the nano-structure obtained after sLbL in ambient conditions, using light tapping mode (TM-AFM) on a calibre multimode scanning probe microscope from Bruker-Veeco, France. By comparing the images of Figure 29 (b) and Figure 29 (c), one can notice a three times increase of graphene sheets’ thickness in RGO@PBCD (around 3 nm) compared to GO (around 1.2 nm), which is comforting the idea that the decoration of RGO with functionalized CD has been effective and useful to prevent the restacking of graphene sheets. Comparing the SEM images of RGO@PYAD and PEG-CD-RGO@PYAD in Figure 30 (a) and (b) respectively, attests that the presence of PEG-CD on the surface of graphene sheets is effective in PEGCD-RGO@PYAD. Moreover the AFM images of Figure 30 (c) and (d) indicate the presence of PEG-CD on the surface of graphene in PEG-CD-RGO@PYAD.

Compositional analysis by UV-Visible spectroscopy

The amount of pyrene adamantan linked to RGO was also confirmed by UV-Vis Spectroscopy as shown in Figure 31 (c). A solution of pyrene adamantan in ethanol was made in four different concentrations as shown in Figure 31 (c) and they were submitted to UV-visible spectroscopy. The Absorbance was plotted as a function of concentration at constant wavelength to get the calibration curve. Using the calibration curve after doing UV-Vis spectroscopy for the filtrate obtained after reaction of graphene and pyrene adamantan, it was found that the concentration of unreacted pyrene adamantan in the filtrate is 0.43 mg/mL whereas, initial concentration of pyrene adamantan before reaction was 0.67 mg/mL. So amount of pyrene adamantan reacted is 0.24 mg/mL, i.e., 54 mg. The total production of RGO@PYAD obtained was 100 mg. Thus, a weight ratio of pyrene adamantan to graphene of 1.1/1 was found. The good agreement between TGA and UV-Visible spectroscopy is validating our results.

Vapour sensing performance of functionalized CD wrapped RGO sensors

The chemo-electrical properties of the fabricated sensors were studied by measuring the electrical resistance when exposed alternatively to a 5 minute cycle of dry nitrogen and saturated VOC while the sensors were placed in a 100 mm× 10 mm× 3 mm chamber with 10 slots. The dynamic vapour sensing device is provided with a mass flow controller, solvent bubbler, electrical valves controlled by Labview software program and KEITHLEY 6517 multimeter as depicted in Figure 32 (a). The total flow rate is always kept constant at 100 mL/min. The chemo-resistive responses of conductive CD nanocomposite (CCDC) sensors can be easily expressed by calculating the relative amplitude of electrical signals (Ar) towards solvents using Equation 1: = ………. (1).
Where R0 and R are the initial resistance of the sensor in pure nitrogen and the resistance of the sensor in the presence of solvent vapour, respectively.
However, the same volume of each vapour under saturated condition does not contain the same number of molecules due to differences in saturation vapour pressure of each analyte. Hence, in order to get rid of the influence of the number of molecules, which acts on the response amplitude, each response was normalized by a factor related to the number of analyte molecules, following Equation 2.

Table of contents :

Chapter I: Structure & content of the Thesis
I.1. General introduction & context of the thesis
I.2. Outline of the manuscript
Chapter II: Bibliographic survey
II.1. Brief note on cancer
II.2. Statistics of cancer related deaths
II.3. Conventional diagnostic tools for cancer
II.4. Interest of VOC sensing
II.5. Exhaled breath VOC biomarkers
II.6. Biomarker analysis: a noninvasive technique of cancer diagnosis
II.7. Cancer biomarkers
II.7.1. Alcohols
II.7.2. Carbonyl compounds
II.7.3. Aliphatic hydrocarbons
II.7.4. Aromatic hydrocarbons
II.8. Different methods of biomarker analysis
II.9. Electronic nose
II.10. Chemical sensors in e-nose
II.11. Smart materials
II.12. Definitions of properties related to vapour sensing
II.13. Classification of sensors
II.13.1. Chromatography
II.13.2. Electrochemical sensors
II.13.3. Mass sensitive sensors
II.13.4. Optical sensors
II.13.5. Chemoresistive sensors
II.13.5.1. Metal oxides
II.13.5.2. Conjugated polymers
II.13.5.3. Conductive polymer nanocomposite (CPC) sensors
II.14. Smart carbon nanomaterials
II.14.1. Structural aspect of carbon nanomaterials
II.14.2. Synthesis and growth
II.14.3. Carbon nanomaterials for vapour sensing applications
II.14.4. Different strategies for functionalization of carbon nanomaterial based sensing materials: State of the art
II.14.4.1. Noncovalent functionalization
II.14.4.2. Covalent functionalization
II.14.4.3. Hybridization
II.15. Safety and security: Environmental issue with carbon nanomaterials
II.15.1. Toxicity of carbon nanotubes
II.15.2. Toxicity of graphene
II.15.3. Occupational exposure limits: safe handling of toxic nanoparticles
II.16. Conclusion and Outlook
II.17. Experimental Strategies undertaken from the light of literature survey
II.17.1. Strategy 1: Conductive oligomeric nanocomposites (COC)
II.17.2. Strategy 2: Conductive nanohybrids
II.17.3. Strategy 3: Conductive polymer nanocomposites (CPC)
Chapter III: Vapour sensing properties of cyclodextrin based conductive Nanocomposite
III.1. Introduction
III.2. Synthesis of nanocomposites and fabrication of sensors
III.2.1. Synthesis of pyrene butyric acid adamantine methyl amide
III.2.2. Synthesis of Graphene Oxide (GO)
III.2.3. Synthesis of RGO and pyrene adamantan linked RGO (RGO@PYAD)
III.2.4. Synthesis of functionalized CD wrapped RGO
III.3. Morphological characterizations of nanocomposites
III.4. Other characterizations in support of successful synthesis
III.4.1. Compositional analysis by thermo gravimetric Analysis (TGA)
III.4.2. Compositional analysis by UV-Visible spectroscopy
III.5. Vapour sensing performance of functionalized CD wrapped RGO sensors53
III.5.1. Sensitivity and selectivity of the functionalized cyclodextrin wrapped graphene based sensors
III.5.2. Functionalization of CD as a tool of tailoring selectivity of sensors
III.5.3. Limit of detection
III.6. Vapour sensing performance of star polymer (triazole PEG) functionalizaed β-CD wrapped graphene
III.7. Conclusion
Chapter IV: Vapour sensing properties of conductive nanohybrids
IV.1. Influence of polyhedral oligomeric silsesquioxane on the molecular selectivity of CNT based hybrid chemical vapour sensors for disease diagnosis
IV.1.1. Introduction
IV.1.2. Synthesis of nanohybrids and fabrication of sensors
IV.1.3. Characterization of the nanohybrids
IV.1.3.1. Morphological study by atomic force microscopy (AFM)
IV.1.3.2. Structural characterization by Fourier transform infra red spectroscopy
IV.1.3.3. Structural characterization by X-ray diffractogram
IV.1.3.4. Study of dispersion of CNT by UV-Visible spectroscopy
IV.1.3.5. Elemental analysis by energy dispersive X-ray spectroscopy (SEM-EDX) .
IV.1.3.6. Compositional analysis by thermo gravimetric analysis (TGA)
IV.1.4. Dynamic vapor sensing
IV.1.5. Tailoring selectivity
IV.1.6. Limit of detection
IV.1.7. Conclusion
IV.2. Tailoring of selectivity & sensitivity of CNT / graphene based vapour sensors by grafting with fullerene
IV.2.1. Introduction
IV.2.2. Synthesis of hybrid nanomaterials
IV.2.3. Morphological study by atomic force microscopy (AFM)
IV.2.4. Morphological study by scanning electron microscopy (SEM)
IV.2.5. Compositional analysis by thermo gravimetric analysis (TGA)
IV.2.6. Dynamic Vapour sensing characterizations
IV.2.7. Limit of detection at ppb level
IV.2.8. Conclusion
Chapter V: Vapour sensing properties conductive polymer nanocomposites (CPC) . 
V.1. Introduction
V.2. Synthesis of sulfonated poly (ether ether ketone)/CNT nanocomposite vapour sensors
V.2.1. Sulfonation of Poly (ether ether ketone)
V.2.2. Fabrication of sensor
V.3. Characterizations of sulfonated Poly (ether ether ketone)
V.3.1. Determination of degree of sulfonation by nuclear magnetic resonance spectroscopy (NMR)
V.3.2. Structural characterizations by FTIR spectroscopy
V.4. Characterization of SPEEK/CNT nanocomposites
V.4.1. Study of degradation by thermo gravimetric analysis (TGA)
V.4.2. Morphological characterization by SEM and AFM
V.4.3. Vapour sensing performance of sulfonated poly (ether ether ketone)/CNT nanocomposites
V.4.4. Influence of hybrid fillers on performance of sulfonated PEEK based CPC sensors
V.5. Conclusion
Chapter VI: Construction of electronic nose & conclusive remarks with future Prospects
VI.1. Library of sensors
VI.2. Principle component analysis
VI.3. E-Nose construction
VI.4. Discrimination of pure and binary mixture of VOC by principle component analysis (PCA)
VI.4. Conclusion and future prospects
List of Figures
List of Tables

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