Oxygen-related Functional Groups Research Articles

Enhancing electrochemical properties of bacterial cellulose-derived carbon nanofibers through physical CO2 activation

Carbon nanofiber (CNF) derived from carbonization of bacterial cellulose (BC), with a unique three-dimensional porous nanostructure, has received significant interest in electrochemical applications. In this study, CNF samples were physically activated in CO2 at different temperatures and durations. Raman spectroscopy and FTIR analysis showed that CO2 activation caused hexagonal lattice defects, disorder, and oxygen-related functional groups in an amorphous carbon structure. CNF surface morphology changed after physical activation, reducing fiber diameter to 55 nm and introducing mesopores. Through activation temperature and time adjustments, surface area (870.1 m2/g) and micropore surface area (535.6 m2/g) and pore volume (0.2148 cm3/g) increased. EDX elemental analysis showed that activated CNF had a carbon concentration of > 90 %, while XPS analysis showed surface functional groups like C-C (sp2) and C-C (sp3) hybridization, which could improve electrolyte ion adsorption and accessibility. Electrochemical properties improved owing to CO2 activation. The optimal activation condition of 800 ℃ for 60 min resulted in the highest specific area capacitance of 552 mF cm−2 at 1 mA cm−2. This activated CNF electrode retained capacitance nearly unchanged up to 3,000 cycles. It also achieved the highest energy density of 76.7 mWh cm−2 at 500 mW cm−2. This study demonstrates the efficacy of CO2 physical activation for enhancing the electrochemical properties of CNF electrodes. The findings also highlight the importance of tailoring activation conditions, providing valuable insights for the design of advanced energy storage materials.

An investigation on purity enhancement through hydrofluoric acid treatment in graphite powder derived from coconut shell

The present research emphasizes a novel approach for synthesizing graphite powder derived from coconut shell (CS) as a precursor, particularly focusing on investigating the effects of hydrofluoric acid (HF) in removing silica and other impurities. The cost-effective pyrolysis technique employed in synthesizing graphite powder entails heating CS to 900 °C, followed by treatment with HF at varying sample-to-acid ratios. Several characterization methods are used to validate the successful synthesis of graphite powder, such as X-ray Diffraction (XRD), Raman Spectroscopy, Fourier-transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). XRD analysis shows a distinctive graphitic structure, with Gr14 (graphite prepared with a CSCP to HF ratio of 1:4) exhibiting a high graphitization degree of 93.02 %, indicative of excellent crystal structure and high-quality graphite. FTIR analysis of coconut shell charcoal powder (CSCP) reveals the presence of various oxygen-related functional groups, effectively removed by HF washing, leading to graphite with minimal impurities. The Raman spectra of Gr14 demonstrate fewer defects and a more organized structure than other samples. SEM image of CSCP reveals particles with non-uniform morphologies, while the EDX spectra indicate that Gr14 consists of 97.84 % carbon. Treating CSCP with HF enhances the electrical conductivity of the graphite, with Gr14 exhibiting a higher conductivity value. TGA results reveal the improved thermal stability of the graphite. The residual weight of Gr14 is maximum, confirming its exceptional thermal stability and purity. The findings suggest that HF has a significant influence on improving the purity of CS-derived graphite. The study concludes that, among the prepared samples, Gr14 exhibits favorable characteristics, such as minimal impurities, superior crystal structure, higher carbon content, good electrical conductivity, high thermal stability, and fewer defects, comparable to pure graphite. Future research in this study aims to use CS-derived graphite powder for synthesizing nanomaterials like graphene oxide (GO) and reduced graphene oxide (rGO).

Effect of Ti on the properties of diamond microcrystals synthesized in C–O–H supercritical fluid at high pressure and high temperature

Diamond micropowders 1–10 μm were synthesized at 7.5 GPa, 1300–1500 °C, and 3–6 s. Detonation nanodiamonds and pentaerythritol (C5H8(OH)4) with the addition of Ti were used as the reaction medium. The total nitrogen concentration, determined by electron paramagnetic resonance (EPR) and infrared (IR) spectroscopies, in diamonds synthesized without the addition of Ti was 1700 ppm. In diamonds synthesized with the addition of Ti, there are no 2N (A-center) and N3VH0 centers as well as oxygen-related functional groups, and the total concentration of nitrogen centers is reduced to 640 ppm. The addition of Ti leads to an increase in the synthesis temperature by 100–200 °C.Thermodynamics model calculations of the equilibrium compositions of the reaction medium at a pressure of 7.5. GPa and temperatures of 500, 1000 and 1500 °C were performed. The Gibbs free energy of possible reactions between the components of the reaction medium was calculated. It has been shown that under equilibrium conditions and a reaction medium corresponding to the synthesis conditions, the formation of TiN is thermodynamically possible. This leads to a decrease in the nitrogen concentration in diamonds. However, the formation of TiO2 is a competing reaction that can lead to a decrease in the concentration of oxygen-related functional groups.

Development and optimization of a polysilicon-aluminum alkali mineral-enhanced biochar composite for effective heavy metal removal in acidic environments

While traditional biochar demonstrates promising performance in diverse settings, its efficacy may be constrained under specific conditions of high acidity and heavy metal concentrations. In this study, researchers developed a new polysilicon-aluminum alkali mineral-enhanced biochar composite material, GBMSs (green biochar-metakaolin-sodium silicate), by pyrolyzing fibers from dragon fruit peels and blending them with metakaolin and sodium silicate. Using a response surface methodology, this environmentally friendly composite material was optimized for removing copper and zinc contaminants across a range of initial pH levels from 2 to 6. Experimental findings indicated that the adsorption capacity of GBMSs for copper and zinc was significantly enhanced, ranging from 1.5 to 4 times greater compared to pure biochar or biochar mixed solely with a silicon-aluminum mineral. Various analytical techniques including scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were utilized to examine the influence of poly-silica-aluminum alkali minerals (GBMSs) on biochar composites. The findings revealed an upsurge in surface binding locations and oxygen-related functional groups because of integrating GBMSs. This augmentation of electronegative features on the biochar surface was credited to the development of stabilizing silica-aluminum connections, ultimately boosting its adsorption effectiveness in acidic surroundings. By applying Langmuir and Freundlich models, it was deduced that the adsorption of GBMSs adheres to a multilayer uniform adsorption mechanism, with surface ion interchange and complexation restricting the adsorption capability. This research highlights the potential of clay mineral-altered biochar in efficiently dealing with intricate environmental contamination.

In situ doping effect in monolayer MoS2 via laser irradiation

Abstract Two-dimensional (2D) semiconducting materials with a single atomic layer display exceptional structural symmetry and band structures, making them the most promising candidates for investigating the spin-valley coupling effect and fabricating novel optoelectronic devices. Their atomic thinness also makes it easy to adjust their excitonic optical response through plasma treatment or thermal annealing. In this study, we present a simple technique for modifying the optical properties of monolayer MoS2 by briefly exposing it to laser irradiation in ambient conditions. Initially, this exposure resulted in a nearly twofold increase in photoluminescence (PL) intensity, with the neutral exciton intensity increasing while the trion exciton intensity decreased. We propose that oxygen-related functional groups, such as O2 and H2O from the surrounding air, adsorb onto MoS2 and extract extra electrons, which enhances exciton emission while reducing trion emission. In a subsequent stage, both exciton intensities decreased as all extra electrons were depleted. Additionally, any structural distortions or potential damage were found to decrease the PL intensity, and these changes were linked to alterations in the Raman spectra.

Effect of Lithium Salts on the Properties of Cassava Starch Solid Biopolymer Electrolytes.

This study evaluates the effect of lithium salts on the structural, electrochemical, and thermal properties of cassava starch solid biopolymer electrolytes (SBPEs). Films of SBPEs were synthesized using plasticizing agents and lithium salts (LiCl, Li2SO4, and CF3LiSO3) via thermochemical method. The SBPEs with lithium salts exhibited characteristic FTIR bands starch, with slight variations in the vibration oxygen-related functional groups compared to salt-free biopolymer spectra. The RCOH/COC index (short-range crystallinity) was higher in the films synthesized without lithium salt and the lowest value was established in the films synthesized with Li2SO4. Thermal degradation involved dehydration between 40 to 110 °C and molecular decomposition between 245 to 335 °C. Degradation temperatures were close when synthesized with salts but differed in films without lithium salt. DSC revealed two endothermic processes: one around 65 °C linked to crystalline structure changes and the second at approximately 271 °C associated with glucose ring decomposition. The electrochemical behavior of the SBPEs varied with the salts used, resulting in differences in the potential and current of peaks from the redox processes and its conductivity, presenting the lowest value (8.42 × 10-5 S cm-1) in the SBPE films without salt and highest value (9.54 × 10-3 S cm-1) in the films with Li2SO4. It was concluded that the type of lithium salt used in SBPEs synthesis affected their properties. SBPEs with lithium triflate showed higher molecular ordering, thermal stability, and lower redox potentials in electrochemical processes.

Processes occurring in the NaCMC/glauconite suspension under the cold plasma treatment. Influence of plasma on adsorptive and stabilizing properties of the system

The paper presents the studies on the processes at the interface of the colloidal suspensions composed of clay mineral - glauconite (GT) and polysaccharide - sodium carboxymethyl cellulose (NaCMC) with the cold plasma treatment (CPT). The surface composition and chemical binding in NaCMC and GT changes are determined by means of FTIR and XPS (both methods detected the incorporation of oxygen-related functional groups). Moreover, the additional information about both the textural properties and morphological changes on the surfaces before and after CPT are studied using the BET, CHN, SEM HRTEM and STEM-EDS methods. The elemental mapping and scanning electron microscope imaging confirmed the NaCMC adsorption on GT (carbon mapping) and proved the GT surface lost its “house of card structure” after the CPT. As follows the CPT causes the protonation of NaCMC and the polymer cross-linking whereas the GT sample is more oxidized. Moreover, it was found that a significant improvement in the GT/NaCMC system stability and the NaCMC adsorption on the GT surface were a result of the CPT. The obtained data could be used for the colloidal stability of polymer/solid suspensions, thus providing new opportunities for the chemical industry; particularly for preparation of new functionalized materials.

Electrochemical oxidation of recycled carbon fibers for an improved interaction toward alkali-activated composites

In this study, recycled carbon fibers (rCF) obtained from pyrolysis are utilized as reinforcements in fly ash-GGBS alkali-activated composites. Since the bond between the fiber and matrix is relatively poor, anodic oxidation was conducted by applying various voltages to enhance the interfacial interactions. Cyclic voltammetry (CV) was performed to investigate the chemical reaction process during the electrochemical fiber modification. Scanning electron microscopy showed the removal of contaminations and impurities from the fiber surfaces by anodization. Thermogravimetric analysis (TGA) analysis was performed to compare the heat resistance properties of the CF reinforced composites and single-fiber tension tests were carried out to evaluate the influence of the electrochemical treatment on the fiber's properties. Single fiber pullout tests and energy dispersive X-ray mapping indicated a remarkable improvement of compatibility between the modified fibers and the matrix, since chemical bonds are formed between oxygen-related functional groups from the anodized fiber surfaces and the alkali-activated matrix. With the addition of 1 wt.% rCFs compressive and flexural strengths have been enhanced by up to 25% and 19%, respectively, compared to the plain composites. The results reveal that electrochemical surface treatment of rCFs is beneficial for enhancing the flexural behavior of rCF-reinforced composite owing to enhanced interfacial bonding. However, this method also provokes a slight increase of porosity compared with untreated fiber-reinforced samples, as proved by mercury intrusion porosimetry (MIP). This study provides a promising utilization of rCF in the production of waste-based fiber-reinforced alkali-activated composites, promoting the management of carbon fiber-reinforced plastic waste.

Role of pH value on electrophoretic deposition of nano-silica onto carbon fibers for a tailored bond behavior with cementitious matrices

Electrophoretic deposition (EPD) of nano-silica (NS) onto carbon fiber (CF) surfaces may considerably improve the bond properties toward cementitious matrices. In the article at hand, varied pH conditions (neutral, acidic, and alkaline environments) are studied during EPD for a tailorable interfacial bond. Zeta potential measurements and cyclic voltammetry (CV) confirmed the importance of pH with regard to the EPD process. Scanning electron microscopy (SEM) and X- ray photoelectron spectroscopy (XPS) revealed that an acidic environment enables the most pronounced and homogeneous NS coating on the CF surfaces. X-ray diffraction (XRD) analysis delivered deeper insights into the microstructures of modified CFs, indicating a decreased graphite interlayer spacing d002 and an increased crystallite size Lc after treatment. This results in a changed temperature-stability as well as mechanical properties, as revealed by thermogravimetric analysis (TGA), single-fiber tensile tests, and Weibull analysis.To assess the interaction of the modified CFs with cementitious matrices, single-fiber pullout tests were performed, showing the highest bond strength and total pullout work of CFs treated in an acidic environment. This is mainly explained by a reaction of the high number of NS particles with calcium hydroxide to form calcium silicate hydrate (C-S-H) gel and, thus, intensifying the interfacial transition zone, subsequently increasing the bond properties of CF to a matrix. As well, abundant oxygen-related functional groups were introduced on the CF surfaces from anodic oxidation, leading to an enhanced bond by promoting precipitation of cement hydration products onto the CF surfaces.

Efficiency of KOH-activated carbon for removal of heavy metal pollution from water

The study to reduce heavy metals pollution from water using the KOH-activated carbon was studied the factors affecting the adsorption capacities of Cu(II) and Pb(II), in particular, initial metals concentration, pH of the solution, and contact time in static conditions. Using X-ray photoelectron spectroscopy and FTIR analysis to determine the elemental composition and surface functional groups of the activated carbon surface, the presence of oxygen-related functional groups was observed. The maximum adsorption capacities were 135.8 mg g-1 and 31.0 mg g-1 for removal of lead and copper solutions with the initial concentration of 300 mg L-1 of metal at 318 K, respectively. The removal percentage was found to be higher for Pb (II) when compared with Cu (II).

Investigation on the structural quality dependent electromagnetic interference shielding performance of few-layer and lamellar Nb2CTx MXene nanostructures

Tunable Electromagnetic Interference (EMI) shielding behaviors of 2D MXene (Nb2CTx) were explored via different exfoliation conditions. Stacked, lamellar few-layer, oxygen-related surface functional groups, and structural defects along with oxidative products of Nb2CTx were identified by tuning chemical etching conditions during one-step exfoliation process. Exfoliation of Nb2CTx with a tightly packed stacked structure remarked at lower etching times. The unpacking of Nb2CTx into lamellar morphology followed by separated few-layer Nb2CTx remarked at moderate etching time, whereas structural misalignment, defects, and oxidation of Nb2CTx occurred during prolonged chemical etching times. Synergistic effect of one-step extracted few-layers and lamellar structured Nb2CTx favorably enrich the assembly of multiple electrical conductive pathways responsible for absorption dominated EMI shielding performance in X- and Ku-band region. The assembled wax nanocomposites with 80% of Nb2CTx loading exfoliated at 100 h etching time at a thickness of 1 mm exhibited EMI shielding effectiveness of about 44.09 ± 1.99 dB at 12 GHz, and its EMI attenuation mechanism explained by conduction and eddy current loss. The combined action of few-layer and lamellar Nb2CTx nanostructures could be interesting for making novel shielding materials; open a new avenue for niobium series in the MXene family for elaborated applications.

Microstructure and electrothermal characterization of transparent reduced graphene oxide thin films manufactured by spin-coating and thermal reduction

We herein report the microstructure, optical and electrothermal properties of a series of reduced graphene oxide (RGO) thin films, which are manufactured by spin-coating (1 and 3 layers) of graphene oxide (GO) dispersion on a quartz substrate and thermal reduction at different temperatures of 800–1000 °C. The energy dispersive X-ray spectra reveal that the relative carbon content of RGO films increases from 84.3 at% to 93.5 at% with increasing the thermal reduction temperature from 800 °C and 1000 °C, whereas the oxygen content decreases from 15.7 at% to 6.5 at%. The optical transmittance of RGO1 (1 spin-coating layer) and RGO3 (3 spin-coating layers) films at 550 nm is characterized 32.7–40.8% and 6.3–12.4%, respectively, although it decreases with increasing the thermal reduction temperature. The sheet resistance of RGO1 films decreases from 5160 Ω/sq to 1220 Ω/sq with the increment of the thermal reduction temperature, whereas the sheet resistance of RGO3 films decreased from 1080 Ω/sq to 350 Ω/sq. The decreases in optical transparency and sheet resistance values of RGO thin films are due to the successful reduction of GO films with oxygen-related functional groups to electrically conductive graphene films during the thermal treatment. The RGO thin films are characterized to exhibit high performance electrothermal behavior in terms of uniform temperature distribution, controllable steady-state saturated temperatures, rapid temperature responsiveness, and electric power efficiency at input power densities.

Electrical property of graphene-coated carbon fiber by self-assembly and thermal-reduction

To improve the electrical properties of carbon fiber (Cf), the fiber surface was carboxylated with nitric acid, aminated with ethylenediamine, and coated with graphene oxide (GO) through self-assembly. The GO-coated Cf was reduced by heat treatment in a temperature range of 500 to 1300 °C. For structural analysis of the reduced GO (rGO), HRTEM, XRD, and Raman spectroscopy were performed, and an I-V curve was obtained to visualize the electrical property. As the heat treatment temperature increased, the crystallinity increased, and the ID/G at 900 degrees was 1.3067, which is the highest value in Raman spectroscopy. The I-V curve reached its highest point at 700 °C and lowest point at 900 °C. This confirmed that the difference in properties at the two temperatures originated from the number of vacancy defects present in the coated rGO. Our experiment confirmed that vacancy defects were more fatal than the oxygen-related functional groups present in GO in terms of electrical properties.

Transforming Carbon Black into Graphene Oxide Quantum Dots by Pulsed Laser Ablation in Ethanol

Graphene oxide quantum dots (GOQDs) are nanometer-sized graphene oxide fragments that exhibit unique properties, making them interesting candidates for a range of new applications. Carbon black, one of the commercially available carbon precursors, is produced by the thermal decomposition or incomplete combustion of organic compounds. It is commonly used as a supporting material for catalysts because of its excellent electrical conductivity, high surface area, and stability. In this paper, we report the transformation of carbon black into GOQDs in 10 min using a one-step facile approach. This transformation was achieved by pulsed laser ablation (PLA) in ethanol using the earth-abundant and low-cost carbon black as precursor. Only ethanol and carbon black were used for the transformation. The carbon clusters ablated from the carbon black were completely transformed into GOQDs with a homogeneous size distribution and heights in the range of 0.3-1.7 nm. This confirmed that the transformed GOQDs consisted of only single- or few-layered graphene quantum dots. The UV-vis spectra showed absorption bands at 215, 260, and 320 nm, which were attributed to the π→π* transition of the C=C of the sp<sup>2</sup> C bond in the sp<sup>3</sup> C matrix. A distinct blue emission peak at 450 nm was evident at an excitation wavelength of 360 nm. The broader PL emission spectra are due to the oxygen-related functional groups emitting PL between 300 and 440 nm.

Roles of structural and chemical defects in graphene on quenching of nearby fluorophores

Oxidation scanning probe lithography was used to systematically fabricate graphene/defective graphene ribbon arrays on a graphene sheet. The tribological, structural, and chemical natures of the defects created by o-SPL were characterized using lateral force microscopy (LFM), micro-Raman (μ-RS) and micro-X-ray spectroscopy (μ-XPS), respectively. While LFM revealed all fabricated patterns exhibited increase in friction, μ-RS and μ-XPS analysis showed that a transition of defect type from structural to chemical defects occurred in the defective graphene ribbons at a threshold voltage (8.5 V). Subsequently, micro-photoluminescence (μ-PL) quenching spectroscopy was measured for a thin layer of polystyrene containing isolated fluorophores (MEH-PPV) spin cast on the ribbon patterns. Whilst the quenching efficiency was suppressed more significantly as defect concentration increased, for pure structural defects, the μ-PL lifetime varied linearly with defect concentration and then saturated to a constant as chemical defects dominated. Among all oxygen related functional groups, the presence of CO bonds led to greatly reduced quenching efficiency while simultaneously reducing the strong blue spectral shift seen for pure graphene with the spectrum at higher CO bond concentration approaching to pristine MEH-PPV. This work demonstrated that local chemical and structural composition in 2D quencher strongly affects the quenching efficiency and dynamics.

Evolution of structural inhomogeneity in polyacrylonitrile fibers by oxidative stabilization

Structural inhomogeneity of stabilized polyacrylonitrile (PAN) fibers was systematically investigated. When the temperature was not high enough (below 200 °C in an air atmosphere) to initiate either cyclization or oxidation, absorbed oxygen related functional groups on the surface of PAN fibers were observed. However, when the temperature was above 200 °C, oxygen started to penetrate into PAN fibers through the skin, resulting in an increase in the oxygen content and significant relaxation of molecular structure. As expected, oxygen was diffused from the skin to the core with increasing temperature. At 240 °C, Raman spectroscopy confirmed that cyclization homogeneously occurred in the whole cross-section of fibers. However, higher temperature (≥260 °C) resulted in different ratios of D and G bands depending on both position and temperature, indicating that inhomogeneous structures were obtained due to temperature gradient by exothermic reactions. In addition, oxygen level in the core was much less than that on the surface. This provides evidence that there is a limit to equalize oxygen content across the fiber. Therefore, cyclization, dehydrogenation, and oxidation as critical reactions in the stabilization of PAN fibers started simultaneously. Above a certain temperature, in particular, increased activation energy due to oxidation at the surface can cause significant inhomogeneity of the resulting fibers.

Ecklonia cava based mesoporous activated carbon for high-rate energy storage devices

Activated carbon has received enormous global attention as an electrode material for electrical double layer capacitors (EDLCs) due to its superior electrochemical performance. But while manufacturing high-quality activated carbon as an electrode material, overcoming limitations such as depletion of raw material resources, poor high-rate performance, and cycle stability is still a significant challenge. To address these limitations, we firstly suggest a novel mesoporous activated carbon derived from ecklonia cava (Meso-ACDE) using an acid-base reaction and KOH activation processes. The optimized Meso-ACDE electrode showed a superior specific capacitance of 182Fg−1 at the current density of 0.2Ag−1 and a high-rate capacitance of 154Fg−1 at the current density of 20.0Ag−1 with an excellent cycling stability up to 2000 cycles. The enhanced electrochemical performance of the Meso-ACDE electrode was mainly attributed to the well-developed mesoporous structure with a high concentration of oxygen related functional groups, which were acquired during the activation process. Thus, we believe that the Meso-ACDE could be a promising alternative to conventional activated carbon for high-performance EDLCs.

Enhanced activity and durability of Pt nanoparticles supported on reduced graphene oxide for oxygen reduction catalysts of proton exchange membrane fuel cells

• ∼3 nm sized Pt nanoparticles supported on rGO using a facile polyol method. • Systematic XPS analyses for oxygen related functional concentration investigations. • Pt/rGO with superior catalytic activity and durability as 1.6 and 3.8 times higher than that of Pt/CB. Proton exchange membrane fuel cells (PEMFCs) are mainly used as a power source of hydrogen fuel cell vehicles. Also, their catalytic activity and durability of oxygen reduction reaction are important because they operate at high voltage and strongly acidic conditions. In this research, we studied the characteristics of the Pt nanoparticles (NPs) supported on the graphene oxide (GO), partially reduced graphene oxide (GO-r), and reduced graphene oxide (rGO) to investigate the enhancement of the activity and durability of oxygen reduction catalysts for PEMFCs. Pt catalysts supported on carbonaceous materials were synthesized through a facile polyol method, and the characteristics of the synthesized catalysts were analyzed with transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, linear sweep voltammetry, cyclic voltammetry, electrochemical impedance spectroscopy, and Raman spectroscopy. The outcomes demonstrated that the rGO was superior to the carbon black support in oxygen reduction activity and long-term durability. Here, the reduced concentration of oxygen related functional groups on the graphene support was the key factor to enhance the oxygen reduction properties and long-term durability of the Pt/rGO catalyst.

Effect of the synthesis method on the properties of lithium doped graphene oxide composites with tin oxide nanoparticles: Towards white luminescence

Graphene oxide (GO) based composites functionalized with nanoparticles are emerging as potential candidates for multifunctional devices. As the synthesis route can strongly influence the way in which the nanoparticles are anchored to GO and the resulting properties, different routes have been employed and evaluated in this work for the preparation of composites formed by GO and undoped or Li doped SnO2 nanoparticles. Promotion of synergetic effects, as well as changes in the structural and luminescent properties of the composites have been also analyzed. In comparison with GO, composite samples synthesized in this work involve enhanced luminescence while retaining nearly white emission, which could lead to wider applicability of GO based composites in free standing and emitting and sensing devices. Aspects, such as GO reduction, stabilization of different Sn-based oxides, variation in the concentration of oxygen related functional groups, changes in the sp2 domain sizes, incorporation of lithium and enhancement of the luminescence, have been analyzed in this work by means of x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive x-ray spectroscopy (EDS), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) characterizations.

X-ray absorption anomaly of well-characterized multiwall carbon nanotubes

We studied X-ray absorption of multiwall carbon nanotube (MWCNT) produced by the chemical vapor deposition method using ethanol and benzene precursors at 1473 K with X-ray absorption fine structure in order to obtain a new designing direction for X-ray shielding fabrics. Acid oxidation and thermal annealing further treated the MWCNTs. The energy dependence of X-ray absorptivity of MWCNTs was efficiently used to remove the effect of the metallic impurity contribution, to elucidate the relationship between X-ray mass attenuation coefficient and the structure of MWCNT. The thermal annealing treatment at 2773 K was the most effective method to increase the crystallinity and to remove the impurities of MWCNTs. The acid and oxidation treated MWCNT induced not only the surface structure difference between MWCNT and highly oriented pyrolytic graphite (HOPG) but also the addition of surface oxygen related functional groups from those treatments, which influence the mass attenuation coefficient (μ/ρ). The X-ray absorptivity of heat treated E-MWCNT and B-MWCNT at 2773 K was close to that of HOPG indicating that those MWCNTs have a well-ordered crystal structure, quite similar to HOPG. On the other hand, E-MWCNT having a less-crystalline surface structure showed larger X-ray absorptivity than HOPG by about 9%.