Formation Of Functional Groups Research Articles

Physicochemical Properties of UV-Irradiated, Biaxially Oriented PLA Tubular Scaffolds

PLA and its blends are the most extensively used materials for various biomedical applications such as scaffolds, implants, and other medical devices. The most extensively used method for tubular scaffold fabrication is by using the extrusion process. However, PLA scaffolds show limitations such as low mechanical strength as compared to metallic scaffolds and inferior bioactivities, limiting their clinical application. Thus, in order to improve the mechanical properties of tubular scaffolds, they were biaxially expanded, wherein the bioactivity can be improved by surface modifications using UV treatment. However, detailed studies are needed to study the effect of UV irradiation on the surface properties of biaxially expanded scaffolds. In this work, tubular scaffolds were fabricated using a novel single-step biaxial expansion process, and the surface properties of the tubular scaffolds after different durations of UV irradiation were evaluated. The results show that changes in the surface wettability of scaffolds were observed after 2 min of UV exposure, and wettability increased with the increased duration of UV exposure. FTIR and XPS results were in conjunction and showed the formation of oxygen-rich functional groups with the increased UV irradiation of the surface. AFM showed increased surface roughness with the increase in UV duration. However, it was observed that scaffold crystallinity first increased and then decreased with the UV exposure. This study provides a new and detailed insight into the surface modification of the PLA scaffolds using UV exposure.

Insight into product characteristics from microwave co-pyrolysis of low-rank coal and corncob: Unraveling the effects of metal catalysts

Microwave pyrolysis of low-rank coal can provide high yield and quality of valuable products. Coupling with hydrogenated and catalytic pyrolysis is considered to achieve the selective or targeted generation of pyrolysis products. In this study, three metal catalysts KCl, Fe2O3, and CaO were used in the microwave catalytic co-pyrolysis of low-rank coal and corncob to investigate their effects on the temperature rise, product distribution, and product structure characteristics. The results showed that the maximum and final temperatures of microwave co-pyrolysis with the addition of a metal catalyst increased, and the corresponding yield and quality of tar were considerably improved. The porous structure of the char with the added metal catalyst was significantly enhanced, and the carbon microcrystal structure became significantly strong, but the change in thickness was minimal. The formation of aliphatic hydrocarbons and CO functional groups in both char and tar was inhibited when Fe2O3 and CaO were added. Among the three metal catalysts, CaO had the most obvious effect on the pyrolysis products, resulting in a maximum tar yield of 10.89 % and the highest light oil of 17.20 %. The char had a more regular and integrated porous structure; its Aar/Aal ratio reached a maximum of 12.603, showing the highest aromaticity. In addition, the total of valuable gas component and heat value of the pyrolysis gas arrived at 84.81 vol% and 14.93 MJ/m3, which showed excellent yield and performance. This work provides sufficient evidences for clean and efficient utilization of low-rank coal using catalytic microwave pyrolysis technology.

Evaluation of fuel properties and combustion behaviour of hydrochar derived from hydrothermal carbonisation of agricultural wastes

Biomass energy is an effective way to replace traditional fossil fuels. In this paper, hydrochar fuels were prepared using agricultural wastes (AW) from corn field at different hydrothermal carbonisation (HTC) temperatures. Their physicochemical properties, combustion characteristics, kinetic analysis and tendency of slagging and scaling were systematically investigated. The results showed that hydrochar had the highest energy yield of 68.54% when the HTC temperature was 220 °C. With the increase in HTC temperature, the H/C and O/C atomic ratios of hydrochar decreased, while the porosity increased first and then decreased. The higher HTC temperature was favourable for the formation of aromatic structures and unfavourable for the formation of oxygen-containing functional groups. As the HTC temperature increased, the Ti and Tb of hydrochar gradually moved to higher temperature range. The Coats-Redfern integration method was applied for the kinetic analysis of AW and hydrochar. The slagging and fouling indices of hydrochar were measured and indicated its low slagging and fouling tendencies, which are conducive to improving the heat transfer efficiency of the heat receiving surface.

Degradation of high density polyethylene (HDPE) through bacterial strain from Cow faeces

The prime objective of our research was to assess the efficiency of fecal bacteria Brevibacillus parabrevis CGK45 from cow in the degradation of HDPE plastic films without any physical or chemical pre-treatment. The biodegradation studies were conducted considering various parameters such as percent weight loss and half-life of HDPE film, biomass of surface adhered cells in terms of protein content as well as viability of bacterial biofilm (CFU/cm2) on plastic surface, and hydrophobicity of bacterial culture. The extent of biodegradation was assessed by implementation of various techniques i.e., Field Emission Scanning electron microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared Spectroscopy (FTIR). The bacterial strain was identified as Brevibacillus parabrevis CGK45 (Accession number MW965577) by phylogenetic analysis using 16S rRNA gene sequence homology. A significant weight loss (4.03%) in the HDPE film treated with strain CGK45 was observed after 90 days. The SEM analysis visualized remarkable bacterial colonization as well as structural changes in the surface micromorphology on HDPE surface. Furthermore, SEM-EDX analysis showed excellent reduction in the atomic percentage of carbon content (2.2%) whereas FTIR analysis confirmed the conformational shifting of peak and formation of new functional groups [ester (1290 cm−1) and alcohol (1368 cm−1)] apparently due to bacterial biofilm biodegradation. The findings of our investigation provides an insight into the ability of cow dung strain B. parabrevis CGK45 in the colonization and utilization of high density polyethylene as a sole carbon source proving its suitability for future environment friendly degradation studies.

Effect of ultrasound-assisted cold plasma pretreatment on cell wall polysaccharides distribution and extraction of phenolic compounds from hyssop (Hyssopus officinalis L.)

Hyssopus officinalis L (Hyssop) is a good source of phenolic compounds. However, conventional methods for extraction of these compounds typically take a long time and have relatively low recovery rates. This study focused on cold atmospheric plasma (CAP) pretreatment and investigated its effects on the ultrasound-assisted extraction (UAE) of phenolic compounds from hyssop. Hyssop was treated at dielectric barrier discharge plasma with air and nitrogen gases for 5, 10, and 15 min. Optical emission spectroscopy was used to evaluate present active species in the plasma. The water contact angle changes, cell wall polysaccharides distribution, and structural variations of the treated samples were determined after treatment. Antioxidant activity and total phenolic contents (TPC) of the extracts were also evaluated. The results showed that CAP treatment reduced the contact angle making surface more hydrophilic. Compared with hyssop, overall no significant changes in the basic structure of all treated samples or the formation of new functional groups were recognized. In addition, CAP pretreatment before UAE increased the antioxidant activity of extracts according to the FRAP assay than the un-pretreated sample and conventional solvent extraction method. Also, TPC increased in samples treated with nitrogen plasma.

Peanut shell biochar immobilized Pseudomonas hibiscicola strain L1 to remove electroplating mixed-wastewater

Mixed electroplating wastewater is in urgent need of eco-friendly and effective treatment. In this study, Pseudomonas hibiscicola L1 strain (strain L1) immobilized in peanut shell biochar (PBC) was effective in the simultaneous removal of Ni(II), Zn(II), Cu(II), Cr(VI) and ammonia nitrogen from mixed electroplating wastewater. PBC improves the biological activity of strain L1. Compared with single PBC and free strain L1, the biochar-immobilized strain L1 had higher removal ratios. The biochar immobilized strain L1 showed excellent removal of Cu(II) (94.92%) > Zn(II) (91.46%) > ammonia nitrogen (79.90%) > Ni(II) (77.02%) > Cr(VI) (34.40%). Scanning electron microscopy (SEM) results showed that strain L1 was well immobilized on PBC with strong bioactivity. X-ray diffractometry (XRD) showed the formation of crystals of Zn(OH)2, Cu(OH)2, CrO(OH) and Ni(OH)2, etc. Fourier transform infrared spectroscopy (FTIR) revealed the formation of multiple functional groups on the surface of the biochar immobilized strain L1. In addition, the highest removal ratios for Ni(II), Zn(II), Cr(VI), Cu(II) and ammonia nitrogen in the sequencing batch reactor (SBR) were 78.70%, 94.57%, 59.70%, 92.50% and 98.81% by biochar immobilized strain L1, respectively. Therefore, biochar immobilized strain L1 has good application potential in treating mixed electroplating wastewater.

Monitoring of biofilm development and physico-chemical changes of floating microplastics at the air-water interface

Microplastics in the aquatic environment serve as a habitat for microbial life, on which they can form biofilms. However, how the development of the biofilm alters the properties of floating microplastics that are at the air-water interface and, therefore, not fully submerged, is not well understood. In this context, an aging experiment was conducted to monitor biofilm formation and changes in physico-chemical properties of low-density polyethylene (floating) microplastics over time. The growth of the biofilm followed the typical bacterial/biofilm growth phases and reached about 30% of the total mass of the microplastics, while the concentration of extracellular polymeric substances within the biofilm remained stable. Presence of chlorophyll a and urease activity indicated presence of photosynthetic microrganisms within the biofilm which was also confirmed by analysis of the biofilm composition. Chemical characterization by FTIR showed the formation of additional functional groups attributed to the formed biofilm, and SEM imaging showed cracks on the surface of the aged microplastics, indicating incipient degradation of the polyethylene. Moreover, the adsorption capacity of the aged particles for metals (Pb(II)) was 52% higher compared to the pristine ones. Aging increased the density and size of the particles; however, it did not lead to the submersion of the aged particles even after 12 weeks of aging, suggesting that additional environmental processes may influence the transport of microplastics from the air-water interface into the water body.

Toward More Efficient Carbon-Based Electrocatalysts for Hydrogen Peroxide Synthesis: Roles of Cobalt and Carbon Defects in Two-Electron ORR Catalysis

Electrochemical production of H2O2 is a cost-effective and environmentally friendly alternative to the anthraquinone-based processes. Metal-doped carbon-based catalysts are commonly used for 2-electron oxygen reduction reaction (2e-ORR) due to their high selectivity. However, the exact roles of metals and carbon defects on ORR catalysts for H2O2 production remain unclear. Herein, by varying the Co loading in the pyrolysis precursor, a Co-N/O-C catalyst with Faradaic efficiency greater than 90% in alkaline electrolyte was obtained. Detailed studies revealed that the active sites in the Co-N/O-C catalysts for 2e-ORR were carbon atoms in C-O-C groups at defect sites. The direct contribution of cobalt single atom sites and metallic Co for the 2e-ORR performance was negligible. However, Co plays an important role in the pyrolytic synthesis of a catalyst by catalyzing carbon graphitization, tuning the formation of defects and oxygen functional groups, and controlling O and N concentrations, thereby indirectly enhancing 2e-ORR performance.

Biodegradation of polystyrene (PS) by marine bacteria in mangrove ecosystem.

Plastics pollution poses a new threat to marine ecosystems. Mangrove locating at estuary worldwide is probably the most heavily polluted area trapping various plastics transported from terrestrial and nearby marine aquaculture. Expanded polystyrene (EPS) is one of most common plastic debris therein and even in the plastic garbage. Here we showed the bacterial diversity of the polystyrene-degrading microbial community from EPS waste sites from a subtropical mangrove area. After enrichment with EPS, the degradation consortia were obtained. They shared a similar community structure dominated by bacteria of Sphingomonadaceae, Rhodanobacteraceae, Rhizobiaceae, Dermacoccaceae, Rhodocyclaceae, Hyphomicrobiaceae, and Methyloligellaceae. Diverse bacteria standing for the first member of the genera of Novosphingobium, Gordonia, Stappia, Mesobacillus, Alcanivorax, Flexivirga, Cytobacillus, Thioclava, and Thalassospira showed PS degradation capability as a pure culture. Further, PS biodegradation of Gordonia sp. and Novosphingobium sp. was quantified by weight loss, in addition to obvious morphological and structural changes of the PS films observed by SEM, ATR-FTIR, and contact angle analysis. The formation of new oxygen-containing functional groups implied the degradation pathway of oxidation. Although the degradation rates ranged from 2.7% to 7.7% after one month in lab and possibly lower in situ, their role in EPS removal is unneglectable.

Sonochemical fabrication of gradient antibacterial materials based on Cu-Zn alloy.

At present research, we highlight ultrasonic treatment as a new way to create materials with a gradient change of chemical or physical properties. We demonstrate the possibility to fabricate novel materials with biocide activity based on simple and cheap Cu-Zn alloy. In this research, we propose a green preparative technique for the sonication of an alloy in an alkali solution. The method leads to a significant visual change and differentiation of particles into three different fractions. Due to the chemical micro gradients in media near the solid surface under intensive sonication, fast formation of specific functional groups occurs on the particles' surface. The particles were studied X-ray diffraction analysis (XRD) analysis, the field-emission scanning electron microscope (SEM) as well as electron backscatter diffraction (EBSD) mode, X-ray Photoelectron Spectroscopy (XPS), the differential pulse anodic stripping voltammetry (DPASV) technique. A strong correlation of both methods proves a redistribution of copper ions from Fraction I to Fraction III that influence for the antibacterial properties of the prepared material. The different biocidal activity was demonstrated for each separated Fraction that could be related to their different phase content and ability to release the different types of ions.

Post-synthetic regulation of the fluorescence of CDs: insights into the fluorescence mechanism.

Exploring the origin of emission is fundamental in the field of carbon dots (CDs). Due to the lack of suitable in situ probing techniques, it is necessary to explore effective alternative methods that can accurately reflect the relationship between the emission and the composition of the functional groups of CDs. Herein, we propose a new method of post-synthetic treatment of CDs by photo-oxidation to investigate the origin of emission for CDs. After the addition of a photo-oxidant into pre-prepared CDs under UV irradiation, the fluorescence of CDs can be regulated from the original orange emission to the final green emission due to the damage of original functional groups and the formation of new functional groups on CDs during the post-treatment process. The abundant dynamic information about the functional groups and emissions of CDs during the visible and ready-to-monitor post-treatment process makes it possible to quantitatively analyze the origin of the emission of CDs. Our results suggest that the emission sub-peaks at 560 nm and 600 nm relate to the CD surface-state-associated -NH3+ groups, while the emission sub-peak at 537 nm or 494 nm is associated with the CD surface-state-associated -OH groups or the CD surface-state-associated carbonyl groups (CO). Under UV irradiation, the CD surface-state-associated -NH3+ groups can be continuously converted into the CD surface-state-associated -OH groups and the CD surface-state-associated carbonyl groups (CO), leading to the changed emission color of CDs.

A flexible and sensitive electrochemical sensing platform based on dimethyl sulfoxide modified carbon cloth: towards the detection of dopamine and carvedilol.

The determination of neurotransmitters and adrenoreceptor drugs is highly essential due to their specific functions in the human body. In this work, the determination of carvedilol (CAR) and dopamine (DA) was carried out using carbon cloth (CC), which was modified using a facile strategy of drop-casting dimethyl sulfoxide (DMSO). This induced the formation of functional groups without any loss in the structural integrity of CC. The DMSO modified CC (CC-DMSO) was used for the detection of CAR in the range of 1 nM to 10 μM with a limit of detection (LOD) of 120 pM. Similarly, the CC-DMSO was able to detect DA in the range of 10 pM to 10 μM with a highly promising LOD of 0.3 pM. A bending test was also carried out on the electrode and it could be seen that only a negligible variation in sensing capability was observed when the electrode was in the bent form. In addition, the detection of CAR and DA was also carried out in real samples such as human serum. This study reveals that this modification strategy can serve as a versatile and flexible sensing platform for the detection of CAR and DA together in real world medical scenarios.

Physiochemical characterization of sodium doped zinc oxide nano powder for antimicrobial applications

Zinc oxide (ZnO) is one of the semiconductor materials with unique antimicrobial properties towards various microorganisms. In this article, pure and Na doped ZnO nanopowders were synthesized by easiest and cost-effective co-precipitation process. X-ray diffraction (XRD),Fourier transform infrared spectroscopy(FT-IR), ultraviolet – visible (UV – Vis) spectroscopy, scanning electron microscopy(SEM), and Energy dispersive X-ray analysis (EDAX) techniques were used to characterize the particle size, surface morphology and chemical composition of prepared materials. The XRD analysis revealed that the samples exhibiting hexagonal wurtzite crystal structure with high crystallinity and the average crystallite size values increased from 23.51 to 28.118 nm. The UV – Vis spectroscopy results exposed that the bandgap energy (Eg) of the samples with the values in the range of 3.068–3.301 eV. The SEM micrographs showed that the morphology of the of synthesized particles are hexagonal and spherical in nanometric size. The EDX spectra confirmed the elemental composition of Na, Zn and O in the crystal lattice and FTIR spectroscopic data proved the formation of functional groups and the presence of chemical bonding at the ZnO interface.Antibacterial activity of pure and Na doped Zinc oxide nanoparticles against Gram-negative pathogenssuch as Escherichia coli, Pseudomonas aeruginosa & Klebsiella pneumoniae and Gram-positive pathogens such as Staphylococcus aureus reveal that the zone of inhibition increases with increasing Na concentration. The antifungal activity against Aspergillus and Candida was investigated.These results demonstrated that the pure and Na doped ZnO samples exhibit enhanced antibacterial and antifungal activity with increasing particle sizein presence of visible light and they could be used as good antibacterial as well as antifungal agents.

Study of Thermal Effect on the Mechanical Properties of Nylon 610 Nanocomposites with Graphite Flakes That Have Undergone Supercritical Water Treatment at Different Temperatures.

This study investigates the thermal effect of supercritical water treatment at different temperatures (150, 175, 200 °C) and semi-vacuum state (-0.08 MPa) on graphite flakes which are then incorporated into nylon 610. The treatment is deemed to increase the surface activity of nanofillers through the formation of oxygen-containing functional groups. X-ray diffraction (XRD) analysis indicated that the crystal structure of the flakes remained similar before and after supercritical water treatment. Fourier transform infrared spectroscopy (FTIR) also showed the presence of hydrogen bonding between the flakes and the polymer matrix through the appearance of amide bands. The intensity of the amide peaks is higher for nanocomposites with treated flakes than untreated ones. Furthermore, scanning electron microscopy (SEM) showed that at higher wt%, aggregation will occur, which leads to a weakening in physical properties. The tensile strength of nanocomposites with treated flakes decreased with increasing wt%, while those with untreated flakes increased with increasing wt%. Young's modulus of all the nanocomposites generally increased with increasing wt%. The highest tensile strength obtained is 967.02 kPa, while that of neat nylon 610 is 492.09 kPa. This enhancement in mechanical properties can be attributed to the intact structure of the graphite flakes and the interaction between the flakes and the nylon 610 matrix. A higher temperature of water treatment was discovered to cause higher oxidation levels on surface of the nanofillers but would result in some structural damage. The optimum nylon 610 nanocomposite synthesized was the one that was incorporated with 1.5 wt% graphite flakes treated at 150 °C and -0.08 MPa, as it has the highest tensile strength.

The enhanced mechanism of Fe(III)/H2O2 system by N, S-doped mesoporous nanocarbon for the degradation of sulfamethoxazole

Fenton-like technology has been widely used in the field of water treatment as an advanced oxidation processes (AOPs), and a multitude of non-homogeneous catalysts have been reported effectively to enhance it. Herein, nitrogen and sulfur co-doped nanocarbon materials (NSC) was designed and synthesized, which formed a unique mesoporous structure and abundant functional groups on the surface. It exhibits superior catalytic performance to enhance the Fe(III)/H2O2 system for sulfamethoxazole (SMX) degradation, kobs is 18 times higher than Fe(III)/H2O2 system after the introduction of NSC under the same experimental conditions. Also, the working pH of Fe(III)/H2O2 system was broadened by NSC. Quenching and probe experiments demonstrate that hydroxyl radical (∙OH) was the dominant active species. Both dissociative and surface-bound iron species were observed, which indicates direct reduction and in-situ binding of Fe(III), respectively. Further investigation found nitrogen and sulfur co-doped attribute to the formation of abundant functional groups, the CO bond and CSC bond on the surface of NSC result in the directly reduce of Fe(III), while –COOH contributes to the in-situ binding. The intermediates and possible degradation pathway of SMX degradation were proposed based on the results of liquid chromatography-quadrupole time of flight-mass spectrometer (LC-QTOF-MS). The results of cycling and co-existing ions experiments demonstrate that NSC has outstanding potential for application. This work provides a novel insight into the sustained removal of micropollutants from the aqueous environment based on the nanocarbon materials enhancing the Fenton-like oxidation.

Characterization of Natural Ca-Bentonite Clays from Ebenebe in Anambra State, Nigeria, Impregnated with Ca(NO3)2, Zn(NO3)2 and KOH for use as Catalysts for Viscosity Reduction in Transesterification Reaction of Castor Oil

Natural Ca-Bentonite from Ebenebe in Anambra State, Nigeria, was successfully impregnated with Ca (NO3)2, Zn (NO3)2 and KOH and further calcined under different conditions of temperature and time using standard methods. Both the natural and impregnated bentonite clays were characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Fluorescence Spectroscopy (XRF) and Scanning Electron Microscopy (SEM) and then applied as catalysts in transesterification reaction of refined castor oil. Viscosity reduction test was used to ascertain the best catalyst for the transesterification. FTIR spectra of the activated clay catalysts show the formation of new functional groups, as the intensity of the Al-O-H stretching group (3633cm-1) of the natural clay increased with slightly higher wavelengths of 3640cm-1, 3644cm-1, 3644cm-1, 3644cm-1, 3640cm-1and 3644cm-1 for CaB2, CaB3, ZnB2, ZnB3 KB400, and KB700 catalysts respectively. XRF result identified the natural bentonite clay as Ca-bentonite clay with Ca-oxide having the most dominant component of 76.71%. XRF chemical compositions of the six activated Ca-bentonite clay catalysts when compared to the natural Ca-bentonite clay confirmed successful impregnation. The SEM images of all the prepared catalysts showed that impregnation and calcination changed the surface morphology of the natural clay. Finally, transesterification reactions of refined castor oil samples were done with 3%w/w natural and impregnated Ca-bentonite catalysts, methanol to oil ratio of 6:1, 2 hours reaction time and 65oC reaction temperature. Results obtained showed a descending order of catalyst viscosity reduction ability to be KB700 > CaB3 > CaB2 > ZnB3 >NCB > ZnB2 > KB400.

Exploring the structural, magnetic and magnetothermal properties of (CoFe2O4)x/(Ni0.8Zn0.2Fe2O4)1-x nanocomposite ferrites

The hard ferrite (CoFe2O4), soft ferrite (Ni0.8Zn0.2Fe2O4) and composite ferrite (CoFe2O4)x/(Ni0.8Zn0.2Fe2O4)1-x (hard/soft ferrite) with x = 0.2,0.4,0.6,0.8 were synthesized by sol-gel auto combustion method. X- Ray Diffraction analysis revealed the formation of the phases. The cubic structures of the samples were confirmed. The thermal analysis done using TGA/DSC confirmed the temperature of phase formation. The FTIR spectroscopy data for the samples were used to confirm the formation of functional groups and successful synthesis of the ferrites. The as-synthesized samples were characterized by SEM confirmed the overlapping spherical particles and elemental mapping was done with EDS. The FESEM and TEM analysis were done for the sample showing enhanced property of magnetic hyperthermia. The saturation magnetization (Ms), Coercivity (Hc) and the remanent magnetization (Mr) of the samples were studied using Vibrating Sample Magnetometry. The surface charge of the particles when dispersed in DI water was examined using Zeta potential measurement. Finally, we analysed the heating characteristics of the samples in an alternating magnetic field of frequency 350 kHz and field amplitude of 50 Oe. It has been concluded that the magnetic properties depend on the concentration of soft and hard ferrite in the samples and magnetic heating efficiency depends on the composition of the samples.

Functional traits of medicinal plant species under different ecological conditions

Medicinal plant species comprise 21% of the Slovakian native flora. Thirteen species, we focused on, grew at a control site (botanical garden) and three natural sites with different ecological conditions. We described effects of irradiance and soil organic matter content on leaf functional traits, such are specific leaf area and leaf dry matter content. For the formation of plant functional groups according to different leaf characteristics, the metric multidimensional scaling (MDS) ordination diagram was applied. Photosynthetically active radiation (PAR) had a more significant effect on studied leaf traits than content of soil organic matter (SOM). Moreover, we studied plasticity of these leaf functional traits and formed plant functional groups based on them. Urtica dioica and Geum urbanum possessed the greatest plasticity of all studied species.

Surface Modification of a Regenerated Cellulose Film Using Low-Pressure Plasma Treatment with Various Reactive Gases.

There is a growing interest in the fabrication of membranes and packaging materials from natural resources for a sustainable society. A regenerated cellulose (RC) film composed solely of cellulose has outstanding advantages including biodegradability, transparency, mechanical strength, and thermal stability. To expand the application of the RC film, various surface modification methods have been proposed. However, conventional chemical methods have disadvantages such as environmental burden and difficulty in controlling the reaction. In this work, low-pressure plasma treatment, a green, solvent-free, and easily controllable approach, was performed for surface modification of the RC film. The effects of three different plasma species (O2, N2, and CF4) and treatment conditions on the surface properties of RC films were investigated based on water contact angle measurements, chemical composition analysis, and surface topography. O2 and N2 plasma treatment slightly enhanced the surface wettability of RC films due to the etching by the plasma reactive species and the formation of new hydrophilic functional groups. In CF4 plasma treatments, the hydrophobic surface with a contact angle of 120.6° was obtained in a short treatment time (60 s) owing to the deposition of fluorocarbon groups on the surface. However, the treated surface in a longer reaction time resulted in increased wettability due to the diffusion and degradation of fluorine-containing bonds. The new insights could be valuable for further studies of surface modification and functionalization of RC films.

Unveiling the role of surface functional groups for the design of nickel manganese/reduced graphene oxide based composite electrode material for high performance asymmetric supercapacitor

Development of additive-free electrode material on conductive substrates is a cost-effective strategy and is essential for the fabrication of high-performance supercapacitor. Herein, the effect of transition metal ions on the preparation of bimetallic (Ni & Mn)/reduced graphene oxide (RGO) composites through multi-step electrodeposition technique was extensively analysed. Two different composites; nickel manganese oxide/RGO (NiMn-G/NF) and manganese nickel oxyhydroxide/RGO (MnNi-G/NF) were synthesized through step-wise electrodeposition technique. The NiMn-G/NF and MnNi-G/NF were prepared through interchanging the source of host transition metal ions (Ni and Mn). Various physicochemical characterization techniques confirmed that the crystal structure as well as the morphology and electrochemical performance of the composites were largely dependent on the host metal ions. The formation of surface functional groups may play a key role in the electrochemical performance of supercapacitors. The MnNi-G/NF electrode showed high specific capacitance of ~1525 F g−1 at 1.5 A g−1 current density compared to NiMn-G/NF (~1312.5 F g−1) and other synthesized electrode materials. An asymmetric supercapacitor (ASC) device was fabricated using MnNi-G/NF as positive and thermally-RGO as negative electrode materials. The fabricated device exhibited highest specific capacitance of ~173.3 F g−1 at 2 A g−1 current density and maximum energy density of ~54.1 Wh kg−1 and power density of 9 kW kg−1.