Synthesis and characterization of reduced graphene oxide-loaded cotton as phase-boundary catalyst in the oxidation of styrene by aqueous hydrogen peroxide

The research described in this thesis is a comprehensive account of the synthesis and characterisation of reduced graphene oxide-loaded textile as a phase-boundary catalyst in the oxidation of styrene with aqueous hydrogen peroxide. A new model of phase-boundary catalyst (PBC) is designed from octadecyltrichlorosilane /polypyrrole/reduced graphene oxide/cotton (OTS/PPy/RGO/CT) for the oxidation of styrene by aqueous hydrogen peroxide. Cotton cellulose textile acts as a layered platform where the reduced graphene oxide (RGO) and polypyrrole (PPy) embedded on it. It has been reported that graphene arose as a candidate as a catalyst for oxidation reaction. Cotton textile is chosen owing to the relatively high network surface area, the abundance of hydroxyl functional group and ability to immobilize graphene oxide (GO) on its surface. Polypyrrole is one of conducting polymers capable to increase the conductivity and induced magnetic field. The effect of magnetic field on the selectivity and activity of the PBC has been studied by applying an electric current on the conductive layered catalyst. A well-attached graphene oxide to cotton (GO/CT) composite has been prepared by dipping pristine cotton in GO ink, and followed by the reduction of GO to reduced graphene oxide (RGO) in order to produce RGO/CT. The composite surface was further modified with polypyrrole (PPy) via chemical polymerization to obtain PPy/RGO/CT composite. Finally, the PPy/RGO/CT was functionalized with octadecyltrichlorosilane (OTS) in order to get floated layered catalyst (OTS/PPY/RGO/CT) in the immiscible liquid-liquid system. The catalysts were characterised by X–ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV–Vis) spectroscopy, Field-emission scanning electron microscopy (FESEM), thermal analysis and chemical analysis, followed by X–ray photoelectron (XPS) spectroscopy, while the influence of improving electric current of textile by PPy and RGO was also examined using four-point probe technique. The results from FTIR and XPS spectral analyses proved that the polypyrrole and RGO were successfully attached to the textile. The four-point probe technique proved that the presence of PPy and RGO increased the electrical conductivity of cotton textile. PPy plays an important role in increasing the electrical conductivity compared to RGO since PPy is conducting material and its amount is larger than RGO. Meanwhile, apply electric current did not give significant effect on the catalyst‘s activity in static condition. The catalytic activity of OTS/PPy/RGO/CT in stirring condition shows that the reduced graphene oxide act as the catalytic active site in the oxidation of styrene with aqueous hydrogen peroxide, as indicated by the 21% increase in the conversion of styrene when the RGO amount was increased (12 times) in OTS/RGO/CT. Meanwhile, main products of the conversion of styrene using reduced graphene oxide–loaded cotton catalyst were styrene oxide and benzaldehyde, with a higher selectivity toward styrene oxide. However, individual graphene materials and PPy before grafting to cellulose fibers were more selective toward benzaldehyde. Lastly, it can be concluded that, based on its properties, reduced graphene oxide-loaded cotton textile is a promising phase-boundary catalyst for the oxidation reaction, specifically for the oxidation of styrene with aqueous hydrogen peroxide

Conducting fabrics of polyester coated with polypyrrole and doped with graphene oxide

Polyester (PES) has been coated with polypyrrole (PPy) to produce conducting fabrics. Graphene oxide (GO) has been used in different concentrations (10, 20 and 30% weight) as counter ion to neutralize the positive charges of the PPy structure. Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) of the PPy/GO powders corroborated the incorporation of GO as counter ion due to the presence of O in the EDX spectrum, as well as an excess of C, arising from GO contribution. The doping level (N+/N) decreased with the GO content. Field emission scanning electron microscopy (FESEM) showed the formation of the PPy/GO coating and the incorporation of GO in the composite. Electrochemical impedance spectroscopy (EIS) in solid state and solution, cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM) were used to test the electrical properties and electroactivity of the fabrics. There was a decrease in the electrical properties and electroactivity as the GO content increased. The conductivity of the fabrics could be tuned by varying the GO content.Spanish Ministerio de Ciencia e Innovación (contract CTM2011-23583) for the financial support. Conselleria d'Educació, Formació i Ocupació (Generalitat Valenciana) for the Programa VALi+D Postdoctoral Fellowship. C2011-UMINHO-2C2T-01 FCT funding from Programa Compromisso para a Ciência 2008, Portugal. XPS studies were performed at CEMUP (University of Porto, Portugal) facilities. Electron Microscopy Service of the UPV (Universitat Politècnica de València) is gratefully acknowledged for help with FESEM and EDX characterization

Graphene-based fabrics and their applications: a review

[EN] Graphene has emerged as a revolutionary material in different fields of science and engineering due to its extraordinary properties such as: high electron mobility, high thermal conductivity, mechanical properties, easy functionalization, etc. The field of textiles is continuously integrating new materials to provide fabrics with new functionalities, hence its incorporation on fabrics was a logical step. Its application to the field of textiles has been recently reported, which has allowed the development of textiles with different functionalities such as: antistatic, UV-protecting, electroconductive, photocatalytic, antibacterial, thermal conductivity, energy storage in flexible supercapacitors, electrodes for batteries, sensors, etc. Up to date no review has been written regarding graphene-based fabrics and their applications. The present review aims to fill the existing gap and provide perspectives into the preparation and applications of graphene-based fabrics and yarns.J. Molina wishes to thank to the Spanish Ministerio de Ciencia e Innovacion (contract CTM2011-23583) for the financial support. J. Molina is grateful to the Conselleria d'Educacio, Formacio i Ocupacio (Generalitat Valenciana) for the Programa VALi + D Postdoctoral Fellowship (APOSTD/2013/056).Molina Puerto, J. (2016). Graphene-based fabrics and their applications: a review. RSC Advances. 6:68261-68291. https://doi.org/10.1039/c6ra12365aS6826168291

Persistent and Developing Sleep Problems: A Prospective Cohort Study on the Relationship to Poor Outcome in Patients Attending a Pain Clinic with Chronic Low Back Pain

: Sleep problems are common in people with low back pain (LBP); however, the mechanisms of how sleep influences pain are complex. To date there is a lack of prospective research on the timing and development of sleep problems in those who have LBP; such information would be useful to identify individuals at risk for poor outcomes. Our aims are to investigate the predictive role of sleep problems on self-report recovery and pain intensity using logistic regression reporting odds ratios (ORs). An observational cohort of 761 chronic LBP patients recruited from a pain management clinic participated, and they completed data at baseline and at 6-month follow-up (n = 682). Results show increased odds for reported nonrecovery (OR 1.52) and pain intensity (OR 2.69) among those who reported sleep problems at baseline. Further analysis on the experience of sleep problems through time showed that those with developing sleep problems (ie, no sleep problems at baseline but reported sleep problems at follow-up) were at increased odds for reporting nonrecovery (OR 2.17) and pain intensity (OR 2.95), as were those who reported sleep problems at both baseline and follow-up, for recovery (OR 2.88) and pain intensity (OR 3.45). Those with resolving sleep problems (ie, sleep problems present at baseline but not at follow-up) were at decreased odds for nonrecovery (OR 0.50) and pain intensity (0.49). Presenting, persistent, and developing sleep problems have a significant impact on recovery for those with LBP. Clinicians may wish to consider treatment options that can address sleep problems

Persistent and Developing Sleep Problems: A Prospective Cohort Study on the Relationship to Poor Outcome in Patients Attending a Pain Clinic with Chronic Low Back Pain

Sleep problems are common in people with low back pain (LBP); however, the mechanisms of how sleep influences pain are complex. To date there is a lack of prospective research on the timing and development of sleep problems in those who have LBP; such information would be useful to identify individuals at risk for poor outcomes. Our aims are to investigate the predictive role of sleep problems on self-report recovery and pain intensity using logistic regression reporting odds ratios (ORs). An observational cohort of 761 chronic LBP patients recruited from a pain management clinic participated, and they completed data at baseline and at 6-month follow-up (n = 682). Results show increased odds for reported nonrecovery (OR 1.52) and pain intensity (OR 2.69) among those who reported sleep problems at baseline. Further analysis on the experience of sleep problems through time showed that those with developing sleep problems (ie, no sleep problems at baseline but reported sleep problems at follow-up) were at increased odds for reporting nonrecovery (OR 2.17) and pain intensity (OR 2.95), as were those who reported sleep problems at both baseline and follow-up, for recovery (OR 2.88) and pain intensity (OR 3.45). Those with resolving sleep problems (ie, sleep problems present at baseline but not at follow-up) were at decreased odds for nonrecovery (OR 0.50) and pain intensity (0.49). Presenting, persistent, and developing sleep problems have a significant impact on recovery for those with LBP. Clinicians may wish to consider treatment options that can address sleep problems

Investigating the catalytic activity of a novel phase‐boundary catalyst in oxidation of styrene

Inhibiting the environment pollutions motivated the development of green catalytic systems. The present research proposed a novel model of phase-boundary catalyst by using octadecyltrichlorosilane/polypyrrole/reduced graphene oxide/cotton (OTS/PPy/RGO/CT) for the oxidation of styrene by aqueous hydrogen peroxide. The catalytic activities were examined in both stirring and static conditions. The effect of electric current was also studied in static condition. The structural properties of the fabricated catalysts were characterized by X-ray diffractometer, Fourier transformed infrared spectroscopy, field emission scanning electron microscopy, and thermal analysis. Moreover, the influence of PPy and RGO on electrical current of textile was also examined by using four-point probe technique. The catalytic activity of OTS/RGO/CT showed that the RGO could act as the catalytic active site in the oxidation of styrene with aqueous hydrogen peroxide, as indicated by the 21% enhancement in the conversion of styrene when the RGO amount was increased (12 times) in OTS/RGO/CT in stirring condition. Finally, it could be stated that RGO-loaded cotton textile was a promising heterogonous catalyst for the oxidation reaction, specifically for the oxidation of styrene with aqueous hydrogen peroxide

Physical and electrochemical appraisal of cotton textile modified with polypyrrole and graphene/reduced graphene oxide for flexible electrode

The aim of this study was to prepare a flexible fabric electrode for electronic devices. Cotton fabric (CT) was used as the substrate for coating graphene oxide (GO) and reduced graphene oxide (RGO) as electroactive materials, then subjected to the chemical polymerization of polypyrrole (PPy). The sheet resistances and surface morphologies of the as-prepared composite textiles were evaluated by means of using van der Pauw technique and FESEM, respectively. XPS results showed a reduction of around 17% in the ratio of O/C in RGO/CT in comparison with the GO/CT, which could be related to the reduction of GO to RGO. The PPy/RGO/CT composite fabric exhibited sheet resistance of 7.5 Ω/sq, whereas PPy/GO/CT samples presented a sheet resistance of 308.3 Ω/sq. Charge-transfer resistance of PPy/GO/CT was 10 times of PPy/RGO/CT, which showed the insulating role of GO in this composite. Therefore, PPy/RGO/CT can hold a significant promise in flexible electrode applications

Fabrication and characterisation of novel ZnO/MWCNT duplex coating deposited on Mg alloy by PVD coupled with dip-coating techniques

Zinc oxide (ZnO)/multi-walled carbon nanotube (MWCNT) duplex coating was synthesized on Mg-0.8Ca-3Zn alloy by physical vapour deposition (PVD) combined with dip coating. The ZnO inner layer was 1.1 μm thick and consisted of spherical nanoparticles. The outer layer of the MWCNTs was 10.2 μm thick, the diameter of the raw MWCNTs was approximately 42 nm, and their lengths were around a few microns. The ZnO/MWCNT duplex coating showed higher compressive strength than the single-layer coated ZnO and bare Mg alloy after immersion in simulated body fluid (SBF) solution. Polarisation and electrochemical impedance spectroscopy tests revealed that the ZnO/MWCNT duplex coating has lower corrosion current (icorr = 7.2 μA/cm2) and higher charge transfer resistance (Rt = 5250 Ω cm2) than the ZnO single-layer coated (Rt = 3420 Ω cm2; icorr = 42.3 μA/cm2) and bare Mg alloy (Rt = 1720 Ω cm2; icorr = 205.4 μA/cm2). In the immersion test, the ZnO/MWCNT duplex coating protected the substrate effectively in the SBF solution, while moderate to serious damage in this electrolyte was observed on the surface of the ZnO-coated and bare samples, respectively. The results indicated that the deposition of MWCNTs as the outer layer and ZnO as the inner layer on the surface of bare Mg alloy sample is a promising technique to enhance its corrosion resistance