C1s Peak Research Articles

Soot particles formed by n-heptane and n-heptane/oxymethylene ether-3 in an inverse diffusion flame: A comparative analysis of chemical features

Oxymethylene ether-3 (OME3) is a promising synthetic e-fuel and alternative fuel for diesel engines. In contrast to diesel fuel, the use of OME3 leads to a distinct combustion process in which soot particles are generated, which leads to changes in the chemical properties of these particles. These chemical properties are intricately connected to both the concentration and availability of potential radical sites, which, in turn, exert a substantial influence on soot oxidation during diesel particulate filter (DPF) regeneration. Hence, it is crucial to investigate the chemical features of soot samples. Nevertheless, a thorough investigation into the chemical features of n-heptane/OME3 soot samples has not been fully understood. Here, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), elemental analyser, and thermogravimetric analysis (TGA) were used to examine the impact of blending OME3 on chemical features of soot particles at various flame heights of an inverse n-heptane-OME3 flame. XPS results from C1s and O1s peaks showed that OME3 incorporation enhanced the concentrations of C = O, C–O, and O = C–O groups, especially C = O groups, with the percentage increase ranging from 11.93 % to 49.74 %. Similarly, the content of aliphatic C − H groups, along with O and H, increased with higher levels of OME3 blending. Moreover, it was discovered that blending OME3 altered the spatial distribution of hybridisation orbitals of carbon atoms, leading to a decrease in the sp2/sp3 ratio by as much as 40 % with the increase in the OME3 blending ratio. The alteration in these chemical properties due to the addition of OME3 enhanced the oxidative reactivity of soot particles, as manifested by up to a 15 % reduction in the measured activation energy. These findings are useful to optimise control strategies of DPF regeneration with the more widespread use of e-fuel.

Structure and vibrational properties of 1D molecular wires: from graphene to graphdiyne.

Graphyne- and graphdiyne-like model systems have attracted much attention from many structural, theoretical, and synthetic scientists because of their promising electronic, optical, and mechanical properties, which are crucially affected by the presence, abundance and distribution of triple bonds within the nanostructures. In this work, we performed the two-step bottom-up on-surface synthesis of graphyne- and graphdiyne-based molecular wires on the Au(111). We characterized their structural and chemical properties both in situ (UHV conditions) through STM and XPS and ex situ (in air) through Raman spectroscopy. By comparing the results with the well-known growth of poly(p-phenylene) wires (namely the narrowest armchair graphene nanoribbon), we were able to show how to discriminate different numbers of triple bonds within a molecule or a nanowire also containing phenyl rings. Even if the number of triple bonds can be effectively determined from the main features of STM images and confirmed by fitting the C1s peak in XPS spectra, we obtained the most relevant results from ex situ Raman spectroscopy, despite the sub-monolayer amount of molecular wires. The detailed analysis of Raman spectra, combined with density functional theory (DFT) simulations, allowed us to identify the main features related to the presence of isolated (graphyne-like systems) or at least two conjugated triple bonds (graphdiyne-like systems). Moreover, other spectral features can be exploited to understand if the chemical structure of graphyne- and graphdiyne-based nanostructures suffered unwanted reactions. As in the case of sub-monolayer graphene nanoribbons obtained by on-surface synthesis, we demonstrate that Raman spectroscopy can be used for a fast, highly sensitive and non-destructive determination of the properties, the quality and the stability of the graphyine- and graphdiyne-based nanostructures obtained by this highly promising approach.

Multi-Spectroscopic Characterization of MgO/Nylon (6/6) Polymer: Evaluating the Potential of LIBS and Statistical Methods.

The potential of using laser-induced breakdown spectroscopy (LIBS) in combination with various other spectroscopic and statistical methods was assessed for characterizing pure and MgO-doped nylon (6/6) organic polymer samples. The pure samples, obtained through a polycondensation chemical technique, were artificially doped with MgO prior to analysis for comparative purposes. These artificially doped samples served as crucial reference materials for comparative analysis and reference purposes. The LIBS studies were performed under local thermodynamic equilibrium (LTE) and optically thin plasma conditions. To assess the structural crystallinity of the nylon (6/6) polymer samples, X-ray diffraction (XRD) analysis, and Fourier transform infrared (FTIR) spectroscopy were employed to detect functional groups such as N-H, C-H, and C-N in the adsorbent polyamide nylon sample. Additionally, diffuse reflectance spectroscopy (DRS) analysis was conducted to investigate the effects of doping and temperature on the band gap and material reflectance across different sample temperatures. Chemical compositional analysis was performed using X-ray photoelectron spectroscopy (XPS) with the carbon C1s peak at 248.8 eV serving as a reference for spectrum calibration, along with energy-dispersive X-ray (EDX) analysis, which demonstrated good agreement between the techniques. To validate the different methodologies, the results obtained from CF-LIBS and EDX were compared with those from the standard inductively coupled plasma mass spectrometry (ICP-MS) technique. Finally, for classification analysis, principal component analysis (PCA) was applied to the LIBS spectral data at different sample temperatures (25 °C, 125 °C, 225 °C, and 325 °C). The analyses demonstrated that the combination of LIBS with PCA, along with other methods, presents a robust technique for polymer characterization.

Potassium-doped nano graphene as an intermediate layer for graphene electronics

To suppress the intrinsic carrier density and increase the carrier mobility in graphene on a silicon dioxide (SiO2) substrate, potassium (K)-doped nano graphene was introduced as an intermediate layer between the graphene layer and SiO2 substrate. Back-gate type graphene field effect transistors with four terminal structures were fabricated, and their electrical properties were measured under vacuum. The results showed that the Dirac point shifted from +9.0 to −0.2 V after inserting the K-doped nano graphene. The results suggested that inserting the intermediate layer compensated for the intrinsic holes and achieved an electron doping of 2 × 1012 cm−2. The field-effect mobilities of electrons and holes also increased because the ionized K-atoms in the intermediate layer shielded the electric force from the negatively charged impurities in SiO2. The K density was estimated using x-ray photoelectron spectroscopy to be 1.49 × 1013 cm−2, and the C1s peak shifted by 0.2 eV, which confirms the upward modulation of the graphene Fermi level by the K-doped nano graphene intermediate layer. These results demonstrated the advantages of the intermediate layer on the carrier density and mobility in graphene.

Structural distinction of zigzag-edge coronoids analyzed by spectroscopies

Unlike armchair-edge coronoids, the band gap of zigzag-edge coronoids (ZCs) can be adjusted via the molecular and cavity sizes. Herein, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy are used to identify 12 structures of ZCs with different molecular and cavity sizes. Evidently, the C1s peak positions of the ZCs depend on the number of carbons (NC) between the inner and outer edges: they shift to a lower and higher binding energy if the ZCs have an even and odd value of NC, respectively, compared with that of structures without a cavity because of the change in band gap. The C1s peak positions of ZCs with NC = 2 and NC = 3–6 differ by more than 0.4 eV. Raman spectroscopic analysis reveals that the detected characteristic modes depend on NC. For structures with NC = 2, C−H vibration and C−C stretching vibration mode bands are observed, whereas for structures with NC = 3–6, C−H vibration and breathing mode bands are observed. In particular, the band originating from the C−H vibration on the inner edge appear in structures with NC = 3–6 and a pore size larger than 8.26 Å. As the molecular size increases, the intensities of the characteristic bands change and the breathing mode band shift to a higher wavenumber. These results indicate that the molecular and cavity sizes of the ZCs can be distinguished using XPS and Raman spectroscopy.

Influence of Y<sup>3+</sup> Doping on Dielectric and Optical Properties of Ce<sub>2</sub>S<sub>3</sub> Spherical Shaped Nanostructures Synthesized by Chemical Precipitation Method

In the present investigation, Y3+ doped (5 wt. %, 10 wt. %, and 12 wt. %) cerium sesquisulfides (Ce2S3) nanoparticles (NPS) were synthesized by a simple chemical precipitation method. Thin films of Y3+:Ce2S3 NPs achieved on ITO (indium tin oxide) substrate. XRD (X-ray diffraction) patterns were used to estimate the size of the NPS, morphology index, texture coefficient, and lattice constants. The crystallite size was found to be in the range of 18-34 nm. UV-visible spectral studies were carried out in order to understand optical absorptivity, and optical band (Eg) of the as-synthesized nanostructures (NS). It has been observed that the red shift in the optical absorptivity and Eg value varies between 3.45 eV to 2.59 eV. Morphology and the presence of Y+3 were investigated by scanning electron microscope (SEM) and energy dispersive X-ray studies (EDX). However, agglomerated spherical-shaped NPs and homogeneous dispersion of Y3+ were observed in EDX analysis. Chemical constituents and nature of the doped NS were examined by X-ray photoelectron spectroscopy (XPS), and binding energies matched with Y 3d3/2, Y 3d5/2, Ce 3d3/2, Ce 3d5/2, O1s, C1s peaks. Y3+: Ce2S3 (12 wt. %) NS subjected for dielectric property studies in the frequency range of 10 Hz-10 MHz at room temperature (RT). High dielectric permittivity (Ɛ), and very low dielectric loss (tan δ) were observed at low frequency for 12 wt. % Y3+:Ce2S3 NS as compared with other doped NS. The as-synthesized NS can be used for high dielectric permittivity, low dielectric loss, and capacitor-related applications.

Strontium titanate perovskite embedded reduced graphene oxide photoanode for dye-sensitized solar cell

Simple chemical reduction process is followed to form strontium titanate perovskite nanoparticles (SrTiO3 NPs) embedded reduced graphene oxide nanocomposite (RGO-SrTiO3 NC). The optical band gap of the RGO-SrTiO3 NC is found as 3.24 eV. The XRD analysis reveals that the crystallite size of the RGO-SrTiO3 NC is considerably low (31.69 nm) when compared to the SrTiO3 NPs (56.93 nm). The Raman investigation establishes RGO existence in RGO-SrTiO3 NC. The C1s peak (285.02 eV) observed in the XPS spectrum of the RGO-SrTiO3 NC unveils modification of SrTiO3 by the RGO. The SEM examination indicate that the SrTiO3 NPs are embedded firmly on the RGO flakes by means of strong binding forces between RGO and SrTiO3 NPs. The SAED pattern of the RGO-SrTiO3NC is in agreement with its corresponding XRD pattern, confirming strong association between SrTiO3 NPs and RGO. The EDAX and elemental analysis of the RGO-SrTiO3 NC unveil existence of elemental peaks corresponding to Sr, Ti, C and O. The RGO-SrTiO3 NC exhibits significantly low PL intensity, indicating reduced charge recombination. The DSSC fabricated using the photoanode of RGO-SrTiO3 NC delivers an enhanced efficiency of 5.42% when compared to SrTiO3 NPs (2.59%) due to the presence of highly conducting RGO.

In English

The hexagon-shape graphene nanoflakes (GNFs) limited by zigzag edges only (with doubly and triply coordinated atoms) have unique increased reactivity. Despite the high systems symmetry (D6h) the Carbon atoms in GNFs occupy non-equivalent positions. Can such physical and chemical characteristics of GNFs, which depend of the atom position in the cluster, definition? This characteristic together with the simplicity of its calculation makes it possible to predict the properties of nanoflakes obtained from GNFs by introducing single and multiatomic vacancies into them or by replacing Carbon atoms with electron withdrawing and electron donating atoms. This characteristic includes the C1s core-level binding energy shifts, the maxima of which characterize the C atoms of a certain type. The proposed work is devoted to quantum chemical calculations of the electronic density of states (DOS) of pristine hexagon-shape GNF C96 (multiplicity, M=5), their saturated counterpart –polycyclic aromatic hydrocarbon(PAH) C96H24 (M=1) and their derivatives with one and two single vacancies in the ground electronic state (GES). All calculations were performed using the density functional theory (DFT) method with the involvement of the valence-split basis set 6-31G (d,p). Systems with open shells were considered using the UB3LYP exchange-correlation functional. The obtained spectra were fitted using Gaussian curve fitting program to determine the binding energy for each peak. The Gaussian function distribution of the theoretically calculated C1s core-level binding energy shifts of GNFs testified the presence of six peaks, each of which refers to a certain type of Carbon atoms. The C1s peak with the highest binding energy (-285.57 eV) is caused by contributions from the doubly coordinated edge cyclic chain (ECC) Carbon atoms. The C1s orbitals of the central hexagon (CHex) atoms and the first cyclic chain (FCC) atoms form delocalized molecular orbitals (MOs) in different parts of the cluster. The analogous spectrum of PAH C96H24 is slightly shifted to the region of lower binding energies and contains only two well-defined peaks. The peak with a higher binding energy (-284.36 eV) is generated by the 1s states of the CHex atoms and the atoms of the FCC, which are bounded to the CHex atoms. The electronic DOS difference in C1s core-level spectra of GNF C96 (M=5) and their saturated counterpart PAH C96H24 is established due to the presence of two weakly bounded π-systems in GNF and common conjugated system in PAH. The electronic DOS of defect-containing cluster C96-1(1) (M=3) (one CHex atom has been removed from the C96nanoflake) is generated by the C1s core-level atoms of the second cyclic chain (SCC), which are located at the different distances from the center of the nanoflake. The peak of the lowest intensity (-284.63 eV) appears in the spectrum as a reflection of the appearance of doubly coordinated Carbon atoms surrounding the single vacancy in the C96-1(1) nanoflake. The analysis of the electronic DOS of the C1s core-level spectrum of the C96-2(1) nanoflakeis shown, that doubly coordinated Carbon atoms, concentrated around two single vacancies, are essentially non-equivalent. If the MO with the lowest binding energy is localized on two of them – the MO with the highest binding energy is localized on the third atoms (one around each single vacancy). The electronic C1s core-level DOS spectrum of defect-containing molecular systems with one C96-1(1)H24 and two C96‑2(1)H24 single vacancies are similar to the analogous spectrum of PAH C96H24. In the first of them – one additional maximum appears due to C1s atoms surrounding the single vacancy. In the second – there are two additional maxima, each of which is generated by C1s core-level atoms adjacent to individual vacancies.

Effective self-charge boosting sweat electrolyte textile supercapacitors array from bio-compatible polymer metal chelates

Planar structured sweat electrolyte textile supercapacitors made from biocompatible polymer metal chelates with effectively boosts their own self-charge. We have investigated sweat electrolyte based energy storage devices that use cotton fabric placed on the skin to achieve effective self-charge boosting and high flexible textile-supercapacitors. Poly3,4-ethylenedioxythiophene: Tris (2-aminoethyl)amine: Manganese oxide@manganese carbonates (PEDOT:TREN:MnO2@MnCO3) matrix hydrogel adorned electrodes. Hydrothermal synthesis employed with active materials under 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) as a solvent. Physiochemical properties and surface morphological features are explored. Mn 2p1/2 (653.2 eV), Mn 2p3/2 (641.3 eV), N1s (401.4 eV), and C1s (401.4 eV) peaks are all present and predicted in the XPS profiles of the composite (285.3 eV). In a state of perspiration, the textile supercapacitor's capacitance is 30 Fcm−2 and this performance preserves 92% of their early performances afterwards 50,000 charge-discharge series, and they also showed remarkable specific capacitance at large area device in real time performance. It is promising good results in biocompatibility tests. To test the sweat dilution with water for a wearable smart and textile-based energy storage device also performed well, this sweat-based textile-supercapacitor could be good candidates to start fabrication or printing e textile embed energy storage system.

Spectroscopic distinction of carbon nanobelts and nanohoops

Among nanocarbon materials prepared via organic synthesis, carbon nanobelts (NBs), such as cyclacenes and cyclophenacenes, and carbon nanohoops (NHs), such as cycloparaphenylenes, are starting materials for preparing carbon nanotubes with controlled structures. Herein, X-ray photoelectron spectroscopy (XPS) and Raman spectra of zigzag NBs (ZNBs), armchair NBs (ANBs) and NHs were simulated using a computational method and calibrated against the experimental spectra of NHs with 6 and 12 benzenes. The XPS results showed that the C1s peak positions for the ZNBs were at binding energies (BEs) at least 0.5 eV higher than those for the ANBs and NHs. As the diameter increased, the peak position was shifted to higher BEs for the ZNBs but to lower BEs for the ANBs and NHs, because of the change of highest occupied molecular orbital and lowest unoccupied molecular orbital energies. The Raman spectroscopic analysis revealed that there were distinct characteristic modes for each type of structure, i.e., the C–H vibrational band for the ZNBs, the G band for the ANBs, and the D band for the NHs. As the diameter increased, the positions of these characteristic bands and the radial breathing modes were shifted. These results indicate that NBs and NHs can be distinguished using XPS and Raman spectroscopy.

Operando photoelectron spectroscopy analysis of graphene field-effect transistors

In this study, operando photoelectron spectroscopy was used to characterize the performance of graphene field-effect transistors under working conditions. By sweeping the back-gate voltages, the carrier concentration of the graphene channel on the 150 nm Si3N4/Si substrate was tuned. From the C1s core level spectra acquired under the application of different gate voltages, the binding energy shifts caused by electric-field effects were obtained and analyzed. Together with the C1s peak shape information and the photoluminescence spectrum of the Si3N4/Si substrate, the presence of local potential across the x-ray beam spot associated with defects and gate leakage current in amorphous Si3N4 was identified. The presence of defects in Si3N4/Si substrate could not only screen the partial electric field generated by the back gate but also serve as long-range scattering centers to the carriers, thus affecting charge transport in the graphene channel. Our findings will help further investigate the dielectric/graphene interface properties and accelerate the utilization of graphene in real device applications.

Plasma Enabled Lithophilic Host for Lithium Anodes

The surge in electric vehicles and portable electronics has sparked increased demand for high-energy-density, rechargeable batteries. Lithium (Li) metal is sought after as the highest energy density anodes. However, Li metal suffers from many challenges including dendritic growth during stripping and plating and safety issues. This talk aims to discuss strategies to mitigate dendritic growth by using a 3D carbon-based host, as well as scalable fabrication techniques to integrate Li metal into a desirable 3D matrix. Electron microscopy and X-ray photoelectron spectrometers are combined to investigate the surface chemistry and morphology, in order to better understand the interaction between the Li metal and 3D carbon-based host material. Identified shifts in the C1s and O1s peaks demonstrate added surface functional groups in the carbon-based host material. With surface functionalization, the proposed Li-metal anode demonstrates significantly improved stability of stripping and plating when compared with lithium metal foil. As a result, the cells assembled with our proposed Li metal anode and the LiNixMnyCozO2 (x+y+z=1) cathode displays enhanced cycling reversibility as compared to the cells assembled with the Li metal foil.

Fabrication of Multiscale 1-Octadecene Monolayer Patterned Arrays Based on a Chemomechanical Method

A controlled and self-assembled micromachining system was built to fabricate a mico/nanoscale monolayer patterned array on a silicon surface using a diamond tip. The process was as follows: (1) we preprocessed a silicon wafer to obtain a hydrogen-terminated silicon surface; (2) we scratched three rectangular arrays of 10 μm × 3 μm with a spacing of 2 μm on the silicon surface with a diamond tip in 1-octadecene solution; the Si-H bonds were broken, and silicon free radicals were formed; (3) the 1-octadecene molecules were connected with silicon atoms based on Si-C covalent bonds, and the 1-octadecene nano monolayer was self-assembled on the patterned arrays of the silicon surface. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Sessile water contact angles were used to detect and characterize the self-assembled monolayers (SAMs). The XPS results showed that the Si2p peak and the O1s peak were significantly decreased after self-assembly; however, the C1s peak was successively significantly increased. Sessile water contact angles showed that the hydrophilicity was weakened after the formation of 1-octenecene SAMs on the silicon substrate. The nanofriction of the sample was measured with AFM. The change in nanofriction also demonstrated that the SAMs were formed in accordance with the patterned array. We demonstrated that, by using this method, self-assembled multiscale structures on silicon substrate can be formed quickly and conveniently.

Highly Dispersive Metal Atoms Anchored on Carbon Matrix Obtained by Direct Rapid Pyrolysis of Metal Complexes

Highly Dispersive Metal Atoms Anchored on Carbon Matrix Obtained by Direct Rapid Pyrolysis of Metal Complexes

Successive Free-Radical C(sp 2 )–C(sp 2 ) Coupling Reactions to Form Graphene

Successive Free-Radical C(sp ² )–C(sp ² ) Coupling Reactions to Form Graphene

Synthesis and characterization of potassium-doped multilayer graphene prepared by wet process using potassium hydroxide

Potassium (K) doping of multilayer graphene was demonstrated by means of a wet chemical process using potassium hydroxide (KOH) aqueous solution (KOH treatment). The presence of K atoms along the stacking direction was confirmed from depth profiles of 41K+ ions obtained by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). The intensity images of 41K+ ions obtained by TOF-SIMS suggested that the K atoms existed throughout the whole area. For the KOH-treated multilayer graphene, no peak due to K intercalation between graphene layers was obtained by x-ray diffraction (XRD); in Raman spectra, splitting of the G-band peak and disappearance of the 2D-band peak were not observed. A graphite intercalation compound structure was not determined by either XRD or Raman results. However, the up-shift in the G-band peak position in the Raman spectra suggested that K atoms were doped in the graphene. X-ray photoelectron spectroscopy carbon 1s spectra implied that KOH treatment resulted in K-termination at the edges and/or domains of graphene. In addition, a C1s shoulder peak appeared at 1 eV higher binding energy compared to the C1s peak of pristine graphene. Temperature-dependent conductivity measurement results indicated that the conductivity of multilayer graphene was increased by KOH treatment. In addition, the conductivity increased with increasing temperature, which could be explained by band overlap.

Development and characterization of Al–Al3Ni–Sn metal matrix composite

The Al–Al3Ni–Sn composite was developed using a powder compassion and sintering metallurgical processing route. Microstructures of the sintered samples revealed the combination of a globular, chain-like and elliptic (raindrop) Al3Ni phases. The differential scanning calorimetry (DSC) analysis confirmed the high temperature stability of the composite. After heat treatment conducted at 500 °C, the Al3Ni chain-like phase in the matrix transformed to raindrop particles. The presence of the Al3Ni intermetallic compound had a positive effect on the hardness since the Al–Al3Ni–Sn composite was harder in comparison to the A356 aluminium alloy. Microstructures were analysed using the LEO 1525 field-emission scanning electron microscope (FE-SEM). The XPS scanned spectra of the A356-Ni-Sn alloy revealed the Al2p, Si2p, C1s, Sn3d5, O1s, Ni2p3 and Mg1s intensity peaks.

Composition tuning in copper - oxide decorated reduced graphene oxide yields efficient photo- and reduction catalysts

A direct low-cost chemical reduction method is presented for the synthesis of the ternary Cu-Cu2O-CuO system. In the presence of graphene oxide, the chemical reduction results in nanostructured copper and copper oxide decorated reduced graphene oxide structures. The presence of graphene oxide limits the conversion of copper to copper oxide and help the formation of the ternary system without the need for any controlled atmosphere. The composition of the ternary system could be changed by varying the amount of copper precursor used. X-ray diffraction studies and XPS analysis confirms the compositional variation in the synthesized nanocomposites. The dominant metallic phase converts to a mixture of metallic copper and Cu2O dominant composition and then to a CuO dominant composition as the copper content increases in the sample. C1s peak shift in the XPS spectra indicates a strong interaction between graphene sheets and copper in copper rich compositions which has not been reported before. The composite nanostructures possess promising catalytic efficiency towards the visible light photodegradation as well as the hydride reduction reactions. The reduced graphene oxide-copper nanocomposites show improved photocatalytic activity with a rate constant value of 0.012 min-1 compared to pure CuO which is having a rate constant value of 0.002 min-1. The enhanced visible light assisted photodegradation is found to be due to the reduced graphene oxide assisted charge transfer and effective plasmonic coupling of the thermal and photonic energies over Cu2O nanostructures. The electronic nature of the enhancement in photocatalytic activity was also confirmed by the quantitative assessment of hydroxyl radical formation using coumarin as a fluorescent probe during the visible light illumination reactions. The highest efficiency for the hydride reduction of para nitroaniline was exhibited by a different catalyst, CuRGO2 with a rate constant value of 0.269 min-1. The Cu2O-Cu-CuO ternary composition of CuRGO2 is instrumental in the high catalytic activity observed for this composite in the hydride reduction reaction. Thus, a rational design of heterostructured nanocatalyst for the visible light assisted degradation as well as the hydride reduction of organic pollutants can be achieved using the presented direct reduction synthesis.

Acid-free polyaniline:graphene-oxide hole transport layer in organic solar cells

Emeraldine-based polyaniline (EB-PANI) was synthesized via oxidative polymerization of aniline in aqueous acid. Various aliquots of graphene oxide (GO) aqueous dispersion were added to aniline during polymerization to achieve a mass percent of GO in the PANI:GO nanocomposites of 0%, 0.49%, 2.4%, 4.9%, 7.3%, 9.8%, 12.2%, and 24.5%, respectively. TEM images of the GO taken from different locations showed that most of the GO is either a double layer or multilayer graphene sheet—although some of the locations showed a single-layer graphene sheet. Raman shift of GO presents the G band located at 1591 cm−1 and the D band located at 1321 cm−1. The thermogravimetric analysis (TGA) of the PANI:GO nanocomposite showed the evidence of existing GO in PANI. The X-ray photoelectron spectroscopy (XPS) narrow scans of EB-PANI, GO, and PANI:GO showed a maximum that is assigned to the C–C peak position (284.8 eV). The deconvolution of the C1s peak in EB-PANI reveals the presence of C–N/C=N species (285.8 eV) assigned to the amine and imine nitrogens in polyaniline. The acid-free hole transport layer (HTL) synthesized from PANI:GO composites was used in two different types of organic solar cells (OPVs), i.e., P3HT:PC60BM (1:0.6) and PCDTBT:PC70BM (1:4). The highest power conversion efficiency (PCE) as a function of GO loadings in the PANI:GO nanocomposites for P3HT:PCBM cells was for the nanocomposite PANI:GO-7.5 with an average of ~ 0.2%, where the GO loading was 7.3% w/w. Equivalently, the PCDTBT:PCBM cells exhibited the highest PCE for PANI:GO-7.5 nanocomposite (~ 0.5%), as well.

Carbon-containing-titania coated stainless steel prepared by high voltage powder spray coating and its adhesion phenomena

Nowadays, many studies involve coating materials on stainless steel prepared by various methods, and many approaches have been taken to improve the abrasion resistance of the coatings. Here, the attachment of carbon/titania (C/TiO2) on stainless steel and the evaluation of its coating adhesion is reported. The commercially available epoxy resin was used as the source of carbon, and the transformation from epoxy resin to pyrolytic carbon was performed. It is proposed that the incorporation of an inorganic particle will improve the adhesion properties through the reduction of the carbon shrinkage. C/TiO2 was prepared from the mixture of commercialized epoxy resin (Oxyplast PR12®) and anatase TiO2 powder, followed by spraying the mixture onto stainless steel (AISI 304) surface using high voltage powder spray coating (HVPSC). The sprayed powders on stainless steel underwent pyrolysis at several temperatures from 300 to 700 °C for an hour to determine the optimum temperature for excellent adhesion. The physical properties of C/TiO2 coated samples were characterized by Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), surface profiler meter and X-ray photoelectron (XPS) spectroscopy. The FTIR analysis of C/TiO2 coating identified the appearance of peaks CH sp3, CO, CO, and TiO. It was noticed that the absorption band of CH sp3, CO, and CO slowly disappeared as the pyrolysis temperature increased, indicating that the structure changed from epoxide to pyrolytic carbon. FESEM images showed that the TiO2 particles were fully covered with the carbon layer, and the thickness was determined to be in the range of 4.8–15.5 μm. The abrasive and peel adhesion test was performed, showing no detachment of coated material of C/TiO2 pyrolyzed at 300 °C, suggesting that this temperature produces the best coating adhesion. The carbon-based coating adhesion phenomena were elucidated by XPS analysis of Fe2p, C1s, and Ti2p element peaks. It was demonstrated that the presence of an oxide layer on stainless steel, availability of functional groups, and structure shrinkage were the factors that affect the adhesion of the carbonaceous coating. The structure shrinkage was reduced due to the presence of TiO2, which is associated with strong coating adhesion. This demonstrated that the carbonaceous coating produced by HVPSC formed an excellent adhesion in the presence of TiO2.