Zener-like electrical transport in polyaniline–graphene oxide nanocomposites

The present study includes the fabrication and characterization and an investigation of the electrical transport properties of nanocomposites of n-PANI and graphene oxide (GO). The samples were prepared by loading different weight percentages D of GO during the chemical oxidative in situ polymerization of aniline monomers. Structural characterization by XRD, FTIR, FESEM, etc. confirmed that the nanocomposites exhibited superior morphology and thermal stability. The transport properties were studied by measuring the variation of conductivity with temperature T, V–I characteristics and the fundamental response V_f at different temperatures T. The dc conductance Σ showed a transition from insulator type behavior to weakly temperature dependent behavior at temperature T_D, which decreased with increasing D. The V–I characteristics were generally nonlinear and the nonlinearity increased with decreasing temperature. Moreover, at temperatures T ≥ T_D, the characteristics showed saturation of voltage for higher values of current, similar to Zener diodes. At lower temperatures (T ≤ T_D), a voltage maximum occurred, similar to thyristors. This behavior leads to the possibility of fabricating devices containing these nanocomposites. We have tried to analyze these results using the framework of scaling theory and the concept of inter-chain hopping conduction and tunneling between conducting grains separated by insulating regimes in the nanocomposite.

The present study includes the fabrication and characterization and an investigation of the electrical transport properties of nanocomposites of n-PANI and graphene oxide (GO).     

Ternary composites of Ni–polyaniline–graphene as counter electrodes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs), different in principle from the conventional solar cells based on p–n junctions, are competitively cost-effective. For development of this kind of emerging solar cell, it is very significant to reduce their cost and improve their energy conversion efficiency to the maximum extent. In this article, ternary composites (Ni–PANI–G composites) consisting of nickel nanoparticles, polyaniline (PANI), and graphene (G) were prepared for the first time and used as counter electrodes to replace the noble metal Pt in DSSCs. In the case of PANI, the introduction of Ni nanoparticles can improve the electrocatalytic ability for the reduction of triiodide ions in the counter electrode, while in the meantime, the addition of graphene in the Ni–PANI–G composites can increase the electrical conductivity of the counter electrode. The optimized DSSCs fabricated by using the Ni–PANI–G composites as the counter electrode exhibit an overall power conversion efficiency of 5.80% compared to 5.30% for reference platinum (Pt) counter-electrodes. Electrochemical impedance spectra (EIS) show that the charge-transfer resistance at the interface between electrolyte and counter-electrode in the case of the ternary composite is obviously decreased. These results are significant to develop low-cost counter electrode materials for DSSCs.

In this article, ternary composites (Ni–PANI–G composites) consisting of nickel nanoparticles, polyaniline (PANI), and graphene (G) were prepared for the first time and used as counter electrodes to replace the noble metal Pt in DSSCs.     

Fabrication of polyaniline–graphene/polystyrene nanocomposites for flexible gas sensors

This research work presents the fabrication of polyaniline (PANI) and graphene–polyaniline (graphene–PANI) nanocomposite-coated polystyrene (PS) nanofibre mats, as well as their application in flexible and highly sensitive gas sensors. The surface morphology of the flexible films is investigated using a number of techniques. The profilometry studies confirmed that the electrospun fibres are evenly distributed over a large surface area and there was no visible difference between coated and uncoated fibres. The SEM morphology studies revealed that a nanocomposite consisting of 10 nm PANI nanofibres and graphene forms a uniform coating around 3 μm diameter PS fiber. AFM showed differences in the 3D surface topography between plain PS nanofibres and coated ones, which showed an increased roughness. Moreover, conductive AFM has indicated an increase in the electrical current distribution from picoamperes to nanoamperes of the PS samples coated with PANI and graphene–PANI because of the applied voltage to the AFM tip that contacted the sample surface. The chemical properties of all the samples are analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD), which revealed the presence of chemical interactions between the nanocomposites and the polymeric backbones. The TGA study indicated that graphene–PANI coated fibres have the highest thermal stability compared to the pure fibres. The addition of the nanocomposite layer to the PS fibre significantly increased the electrical conductivity. Therefore, nanocomposite-coated flexible membranes are used to fabricate carbon dioxide gas sensors (sensing range: 20–100 ppm). Due to the higher surface area of the nanocomposite coated fibre the availability of adsorption area is also higher, which leads to an increase in sensitivity to carbon dioxide gas. The sensitivity increases with the increase in gas concentration. The average response time of the sensor is calculated to be 65 seconds, with good and uniform repeatability.

A flexible thin membrane made of a graphene–PANI nanocomposite decorated PS electrospun fibre as a highly sensitive carbon dioxide gas sensor.     

A carbonised sieve-like corn straw cellulose–graphene oxide composite for organophosphorus pesticide removal

The development of efficient adsorbents for the removal of organophosphorus pesticides from water is a major challenge. In this work, we prepared an activated carbon derived from sieve-like cellulose/graphene oxide composites (ACCE/G) for the removal of several organophosphorus pesticides. We employed corn straw to produce a sieve-like cellulose–graphene oxide composite (CCE/G); then, by treating CCE/G with potassium hydroxide at high temperatures, the efficient adsorbent ACCE/G was prepared. The adsorption capacity of ACCE/G is higher than those of other sorbents, including a multi-wall carbon nanotube, graphitised carbon black, activated carbon, C18, and primary secondary amine adsorbent. The ACCE/G structure has been fully characterised via scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and Brunauer–Emmett–Teller analysis. The maximum adsorption capacity of ACCE/G is 152.5 mg g⁻¹ for chlorpyrifos. The mechanism, the thermodynamic properties, and the kinetics of the adsorption process have been investigated as well. Our findings demonstrate that the adsorption mechanism depends on the electron-donating abilities of the S and P atoms. Moreover, the Langmuir model gives the best fit for the isotherm data, and the adsorption efficiency of the ACCE/G is still over 80% after eight times of recycling, making ACCE/G a valuable candidate for the removal of OPPs.

Synthesizing a reusable adsorbent from waste corn straw is a sustainable way to utilize secondary resources and purify water.     

Optimization and characterization of magnetite–reduced graphene oxide nanocomposites for demulsification of crude oil in water emulsion

Oily wastewater from the oil and gas industry negatively affects the environment. Oily wastewater typically exists in the form of an oil-in-water emulsion. Conventional methods to treat oily wastewater have low separation efficiency and long separation time and use large equipment. Therefore, a simple but effective method must be developed to separate oil-in-water emulsions with high separation efficiency and short separation times. Magnetite–reduced graphene oxide (M–RGO) nanocomposites were used as a demulsifier in this work. Magnetite nanoparticles (Fe₃O₄) were coated on reduced graphene oxide (rGO) nanosheets via an in situ chemical synthesis method. The synthesized M–RGO nanocomposites are environmentally friendly and can be recovered after demulsification by an external magnetic field. M–RGO characterization was performed using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning microscopy, Raman spectroscopy, and vibrating sample magnetometry. Demulsification performance was evaluated in terms of M–RGO dosage, effects of pH, and brine concentration. The demulsification capability of M–RGO was determined based on the residual oil content of the emulsion, which was measured with a UV-vis spectrometer. The response surface method was used to determine the optimum conditions of the input variables. The optimum demulsification efficiency achieved at pH 4 and M–RGO dosage of 29 g L⁻¹ was approximately 96%. This finding demonstrates that M–RGO nanocomposites are potential magnetic demulsifiers for oily wastewater that contains oil-in-water emulsions. Also, the recyclability of this nanocomposite has been tested and the results shown that it is a good recyclable demulsifier.

Magnetite reduced graphene oxide were synthesized for separation of crude oil in water emulsion.     

Boron/nitrogen co-doped carbon synthesized from waterborne polyurethane and graphene oxide composite for supercapacitors

We report B/N co-doped carbon materials synthesized by an efficient and easy one-step carbonization method with ferric catalyst treatment from a precursor with boric acid treatment after the formation of the composite between waterborne polyurethane (WPU) and graphene oxide (GO). The nitrogen content was improved with the introduction of numerous melamine in the synthetic process of WPU. In addition, WPU possessed a repetitive basic unit urethane bond (–NHCOO); thus, nitrogen heteroatom could be efficiently introduced into the WPU/GO composite from WPU as a nitrogen-rich carbon. In addition, the specific surface area was increased by the boric acid treatment and washing process. The ferric catalyst treatment could prevent the formation of inert B–N bonds. Thus, the synthesized B/N co-doped carbon materials exhibited high specific capacitance (330 F g⁻¹ at 0.5 A g⁻¹), superior rate performance, and excellent cycling stability. Furthermore, the assembled symmetric supercapacitor displayed a good energy density (7.9 W h kg⁻¹ at 505 W kg⁻¹) and a good capacitance retention of about 89.9% after 5000 charge–discharge cycles in 6 M KOH electrolyte. Therefore, the as-prepared B/N co-doped carbon materials show a promising future in supercapacitor application.

We report B/N co-doped carbon materials synthesized by a carbonization method with ferric catalyst treatment from a precursor with boric acid treatment after the formation of the composite between waterborne polyurethane and graphene oxide.     

Self-assembly preparation of lignin–graphene oxide composite nanospheres for highly efficient Cr(vi) removal

Recently, research interest in the application of lignin is growing, especially as adsorbent material. However, single lignin shows unsatisfactory adsorption performance, and thus, construction of lignin-based nanocomposites is worth considering. Herein, we introduced graphene oxide (GO) into lignin to form lignin/GO (LGNs) composite nanospheres by a self-assembly method. FTIR and ¹H NMR spectroscopy illustrated that lignin and GO are tightly connected by hydrogen bonds. The LGNs as an environmental friendly material, also exhibit excellent performance for Cr(vi) removal. The maximum sorption capacity of LGNs is 368.78 mg g⁻¹, and the sorption efficiency is 1.5 times than that of lignin nanospheres (LNs). The removal process of Cr(vi) via LGNs mainly relies on electrostatic interaction, and it also involves the reduction of Cr(vi) to Cr(iii). Moreover, LGNs still have high adsorption performance after repeating five times with the sorption capacity of 150.4 mg g⁻¹ in 200 mg g⁻¹ Cr(vi) solution. Therefore, the prepared lignin–GO composite nanospheres have enormous potential as a low-cost, high-absorbent and recyclable adsorbent, and can be used in wastewater treatment.

Lignin/GO (LGNs) composite nanospheres were prepared by self-assembly method, which showed excellent adsorption performance for Cr(vi) removal.     

A 2D metal–organic framework/reduced graphene oxide heterostructure for supercapacitor application

Metal organic frameworks (MOFs) with two dimensional (2D) nanosheets have attracted special attention for supercapacitor application due to their exceptional large surface area and high surface-to-volume atom ratios. However, their electrochemical performance is greatly hindered by their poor electrical conductivity. Herein, we report a 2D nanosheet nickel cobalt based MOF (NiCo-MOF)/reduced graphene oxide heterostructure as an electrode material for supercapacitors. The NiCo-MOF 2D nanosheets are in situ grown on rGO surfaces by simple room temperature precipitation. In such hybrid structure the MOF ultrathin nanosheets provide large surface area with abundant channels for fast mass transport of ions while the rGO conductive and physical support provides rapid electron transport. Thus, using the synergistic advantage of rGO and NiCo-MOF nanosheets an excellent specific capacitance of 1553 F g⁻¹ at a current density of 1 A g⁻¹ is obtained. Additionally, the as synthesized hybrid material showed excellent cycling capacity of 83.6% after 5000 cycles of charge–discharge. Interestingly, the assembled asymmetric device showed an excellent energy density of 44 W h kg⁻¹ at a power density of 3168 W kg⁻¹. The electrochemical performance obtained in this report illustrates hybridization of MOF nanosheets with carbon materials is promising for next generation supercapacitors.

In this 2D NiCo-MOF/rGO hybrid, the MOF nanosheets provide abundant active sites while the conductive rGO provide rapid electron transport.     

Preparation and characterization of antibacterial dopamine-functionalized reduced graphene oxide/PLLA composite nanofibers

Electrospun poly(l)-lactide (PLLA) ultrafine fibers are a biodegradable and biocompatible scaffold, widely used in tissue engineering applications. Unfortunately, these scaffolds have some limitations related to the absence of bioactivity and antibacterial capacity. In this study, dopamine-functionalized reduced graphene oxide (rGO)/PLLA composite nanofibers were fabricated via electrospinning. The morphology and the physicochemical and biological properties of the composite nanofibers were investigated. The results indicate that incorporating rGO improves the hydrophilic, mechanical, and biocompatibility properties of PLLA nanofibers. Tetracycline hydrochloride (TC)-loaded rGO/PLLA composite nanofibers showed better controlled drug release profiles compared to GO/PLLA and PLLA nanofibrous scaffolds. Drug-loaded nanofibrous scaffolds showed significantly improved antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Additionally, rGO/PLLA composite nanofibers exhibited enhanced cytocompatibility. Thus, it can be concluded that rGO/PLLA composite nanofibers allow the development of multifunctional scaffolds for use in biomedical applications.

Antibacterial dopamine-functionalized reduced graphene oxide (rGO)/PLLA composite nanofibers for biomedical applications.     

Electrodeposited nickel–graphene nanocomposite coating: effect of graphene nanoplatelet size on its microstructure and hardness

In this study, the effect of graphene nanoplatelet (GNP) size on the microstructure and hardness of the electrodeposited nickel–graphene nanocomposite coatings were investigated. GNPs with different sizes were prepared by using a high energy ball milling technique. The experimental result revealed the high energy ball milling technique could reduce the size, increase the surface area, and improve the dispersion ability of GNPs. The microstructure, hardness, and components of the nanocomposite coatings were greatly affected by GNP sizes. The highest microhardness was measured to be 273 HV for the nanocomposite coatings containing 5 h-milled GNPs, which is increased up to ∼47% compared to pristine Ni coating. The enhancement in the hardness is attributed to the uniform dispersion of the small GNP sizes inside the Ni matrix and the Ni grain size reduction when using milled GNPs.

The effect of graphene nanoplatelet size on the microstructure and hardness of electrodeposited nickel–graphene nanocomposite coatings was investigated.     

Synthesis of graphene via electrochemical exfoliation in different electrolytes for direct electrodeposition of a Cu/graphene composite coating

Directly dispersing graphene into an electrolyte still remains a crucial difficulty in electrodepositing a graphene enhanced composite coating onto electrical contact materials. Herein, graphene was synthesized via electrochemical exfoliation in an N,N-dimethylformamide (DMF)/H₂O solution containing (NH₄)₂SO₄. The electrochemically exfoliated graphene nanosheets (GNs) were directly dispersed by sonication. In comparison with graphene synthesized from aqueous solution, the GNs electrochemically exfoliated in the DMF/H₂O–(NH₄)₂SO₄ solution exhibit a lower degree of oxidation. Cu/graphene composite coatings were subsequently electrodeposited onto Cu foils by adding Cu²⁺ into the as-fabricated graphene solution. The surface nanostructure of the Cu/graphene composite coatings was transformed from loose pine needles to a uniform and compact structure with an increase in the concentration of Cu²⁺, which indicated that the controllable synthesis of Cu/graphene composite coatings with different performances could be achieved in graphene dispersions after adding Cu²⁺. In order to synthesize graphene via electrochemical exfoliation and directly electrodeposit a Cu/graphene composite coating without adding CuSO₄ or any other additive, an attempt was made to directly electrodeposit a Cu/graphene composite coating in CuSO₄/DMF/H₂O solution after electrochemical exfoliation.

Electrochemically exfoliated graphene was directly dispersed in the DMF/H₂O solution for electrodeposition of a Cu/graphene composite coating.     

Synthesis of biodiesel from waste cooking oil catalyzed by β-cyclodextrin modified Mg–Al–La composite oxide

In this study, Mg–Al–La composite oxide loaded with ionic liquid [Bmim]OH was used as a catalyst for the synthesis of fatty acid isobutyl ester (FAIBE) via transesterification between waste cooking oil and isobutanol. Mg–Al–La composite oxide was synthesized from the β-cyclodextrin (β-CD) intercalation modification of Mg–Al–La layered double hydroxides. The structure of the catalyst was characterized via XRD, BET and EDS. The results showed that the interlayer space of the catalyst was increased due to β-CD intercalation modification. The IL/CD–Mg–Al–La catalyst exhibited significant catalytic activity and regeneration performance in transesterification due to large interlayer space and strongly alkaline ionic liquid. The yield of FAIBE achieved was 98.3% under the optimum reaction condition and 95.2% after regeneration for six times. The viscosity–temperature curve of FAIBE was determined and the phase transition temperature was −1 °C. The pour point of FAIBE was only −10 °C, which exhibited excellent low temperature fluidity.

In this study, Mg–Al–La composite oxide loaded with ionic liquid [Bmim]OH was used as a catalyst for the synthesis of fatty acid isobutyl ester (FAIBE) via transesterification between waste cooking oil and isobutanol.     

An ionic liquid–molecularly imprinted composite based on graphene oxide for the specific recognition and extraction of cancer antigen 153

Molecularly imprinted polymers with graphene oxide (GO) as a carrier (GMIPs) were synthesized to selectively recognize and capture cancer antigen 153 (CA153). The results show that the MIP has good selectivity and adsorption for CA153, and has strong anti-interference ability. Molecularly imprinted solid phase extraction (MISPE) combined with ultra performance liquid chromatography (UPLC) for the specific adsorption of CA153 was also established, and showed great potential for the analysis of CA153 in clinics in the future.

In this research, we used GO as the support material, IL as the stabilizer, CA153 as the template and DA as the functional monomer for the preparation of GMIPs. The GMIP was successfully used as an enrichment agent for the selective enrichment of CA153.     

A novel fabrication method of copper–reduced graphene oxide composites with highly aligned reduced graphene oxide and highly anisotropic thermal conductivity

Recently, metals with graphene and graphene oxide have been extensively used to enhance the mechanical and anisotropic thermal properties of composites. A novel facile fabrication approach of layer by layer self-assembly followed by hot press sintering was adopted to make copper–reduced graphene oxide composites. The microstructure and heat dissipation properties of pure copper and copper–reduced graphene oxide composites were analyzed with the help of SEM and continuous laser machine analysis. Thermal diffusivity of pure copper and copper–reduced graphene oxide composites was examined in different directions to measure the anisotropic thermal properties by using different volumetric percentages of reduced graphene oxide in the composites. Extraordinarily high anisotropic thermal conductivity of the copper–reduced graphene oxide composites was obtained at a very low concentration of 0.8 vol% reduced graphene oxide, with the difference between the thermal conductivity in-plane and through-plane being a factor of 8.82. Laser test results confirmed the highly anisotropic behavior of our copper–reduced graphene oxide composite with the remarkable property of heat dissipation. The three point bending test was also performed to check the flexural strength of the composites. At 0.6 vol% rGO, the flexural strength was noted (∼127 MPa), and it is 22% higher than that of pure sintered Cu. The high value of anisotropic thermal conductivity and higher flexural strength exhibited by the copper–reduced graphene oxide composite produced using a simple two-step fabrication method give us new hope to use these materials as heat sinks in thermal packaging systems.

Highly aligned rGO with anisotropic thermal conductivity was obtained in this work.     

Microstructure,friction and corrosion resistance properties of a Ni–Co–Al2O3 composite coating

Ni–Co–Al₂O₃ composite coatings were prepared by pulsed electrodeposition and electrophoresis–electrodeposition on aluminum alloy. The content of Al₂O₃ particles of the Ni–Co–Al₂O₃ composite coating prepared by electrophoresis–electrodeposition was significantly higher than the composite coating prepared by pulsed electrodeposition. The composite coating prepared by electrophoresis–electrodeposition exhibited a better anti-wear performance than that prepared by pulsed electrodeposition. The morphology, composition and microstructure of the composite coatings were determined by means of X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The hardness and friction properties of the samples were tested on the microhardness tester and the friction and wear loss tester respectively.

Ni–Co–Al₂O₃ composite coatings were prepared by pulsed electrodeposition and electrophoresis–electrodeposition on aluminum alloy.     

生物可降解聚氨酯的合成及应用

生物可降解聚氨酯材料具有优异的机械性能,良好的血液相容性、组织相容性和生物可降解性,因而在生物医学上得到了广泛的应用.聚氨酯的设计自由度很大,可以通过选择不同嵌段和调节软硬段间的比例,从而合成出具有不同化学结构、机械性能和热性能的聚氨酯以满足不同的应用要求.生物可降解聚氨酯在医学上的应用主要集中在药物缓释载体材料、手术缝合线、人造皮肤、伤口敷料、医用粘合剂、组织工程修复及细胞培养支架等.     

Plasticity control of poly(vinyl alcohol)–graphene oxide nanocomposites

Composite films containing poly(vinyl alcohol) filled with different amounts of graphene oxide (2 and 4 wt%) were prepared by the solution casting technique, and the mechanical properties of the resulting materials were modified with different amounts of glycerol as a plasticizer. Two series of pure poly(vinyl alcohol) and graphene oxide-loaded films with fixed amounts of water were used for modification with glycerol, since water can also serve as a plasticizer for poly(vinyl alcohol). The morphology and physical properties of the plasticized and non-plasticized composites were studied; tensile tests were performed to investigate and compare their mechanical properties. Glycerol addition does not affect the excellent compatibility of the filler with the polymer matrix and uniform distribution of graphene oxide in poly(vinyl alcohol). For poly(vinyl alcohol)/graphene oxide films an increase of the Young''s modulus and yield stress was found with an increase of the filler content; the Young''s modulus for poly(vinyl alcohol) filled with 4 wt% of graphene oxide is almost two times higher than that of the pure polymer. Simultaneously, a sharp decrease of the elongation at break from 80% for pure PVA to about 5% for the PVA/GO composite with 4 wt% of GO is observed, and the film''s brittleness dramatically increases. It was shown that the addition of glycerol to the composite films leads both to the Young''s modulus decrease and tensile energy at break increase; here the Young''s modulus decreases by 18 times after addition of 20 wt% of glycerol to the poly(vinyl alcohol) film filled with 4 wt% of graphene oxide. Thus, the use of plasticizer results in a significant increase of the ductile properties of graphene oxide filled poly(vinyl alcohol) composite films, and the higher the water content in the composite film, the more drastic the increase of the ductile properties observed.

The plasticity of poly(vinyl alcohol)–graphene oxide nanocomposites was significantly improved and the failure mechanism changed from brittle to ductile failure.     

Sol–gel-assisted micro-arc oxidation synthesis and characterization of a hierarchically rough structured Ta–Sr coating for biomaterials

Tantalum (Ta) is an element with high chemical stability and ductility that is used in orthopedic biomaterials. When utilized, it can produce a bioactive surface and enhance cell–material interactions, but currently, there exist scarce effective methods to introduce the Ta element onto the surface of implants. This work reported a sol–gel-assisted approach combined with micro-arc oxidation (MAO) to introduce Ta onto the surface of the titanium (TC4) substrate. Specifically, this technique produced a substrate with a hierarchically rough structured topography and introduced strontium ions into the film. The films were uniform and continuous with numerous crater-like micropores. Compared with the TC4 sample (196 ± 35 nm), the roughness of Ta (734 ± 51 nm) and Ta–Sr (728 ± 85 nm) films was significantly higher, and both films (Ta and Ta–Sr) showed increased hydrophilicity when compared with TC4, promoting cell attachment. Additionally, the in vitro experiments indicated that Ta and Ta–Sr films have the potential to enhance the recruitment of cells in the initial culture stages, and improve cell proliferation. Overall, this work demonstrated that the application of Ta and Ta–Sr films to orthopedic implants has the potential to increase the lifetime of the implants. Furthermore, this study also describes an innovative strategy to incorporate Ta into implant films.

A hierarchically rough structured Ta–Sr coating for biomaterials fabricated by a sol–gel-assisted micro-arc oxidation technique.     

Synthesis and characterisation of heteroatom-doped reduced graphene oxide/bismuth oxide nanocomposites and their application as photoanodes in DSSCs

Semiconductor materials have been recently employed in photovoltaic devices, particularly dye-sensitized solar cells (DSSCs), to solve numerous global issues, especially the current energy crisis emanating from the depletion and hazardous nature of conventional energy sources, such as fossil fuels and nuclear energy. However, progress for the past years has been mainly limited by poor electron injection and charge carrier recombination experienced by DSSCs at the photoanode. Thus, novel semiconductor materials such as bismuth oxide (Bi₂O₃) have been investigated as an alternative photoanode material. In this study, Bi₂O₃ was integrated with nitrogen- or boron-doped reduced graphene oxide (N-rGO or B-rGO, respectively) via a hydrothermal approach at a temperature of 200 °C. Various instrumental techniques were used to investigate the morphology, phase structure, thermal stability, and surface area of the resulting nanocomposites. The incorporation of N-rGO or B-rGO into Bi₂O₃ influenced the morphology and structure of the nanocomposite, thereby affecting the conductivity and electrochemical properties of the nanocomposite. B-rGO/Bi₂O₃ exhibited a relatively large surface area (65.5 m² g⁻¹), lower charge transfer resistance (108.4 Ω), higher charge carrier mobility (0.368 cm² V⁻¹ s⁻¹), and higher electrical conductivity (6.31 S cm⁻¹) than N-rGO/Bi₂O₃. This led to the fabrication of B-rGO/Bi₂O₃ photoanode-based DSSCs with superior photovoltaic performance, as revealed by their relatively high power conversion efficiency (PCE) of 2.97%, which outperformed the devices based on N-rGO/Bi₂O₃, rGO/Bi₂O_3, and Bi₂O₃ photoanodes. Therefore, these results demonstrate the promising potential of heteroatom-doped rGO/Bi₂O₃-based nanocomposites as photoanode materials of choice for future DSSCs.

Semiconductor materials have been employed in photovoltaic devices to solve several global issues, especially the energy crisis emanating from the depletion and hazardous nature of conventional energy sources, such as fossil fuels and nuclear energy.     

Direct electrodeposition of cationic pillar[6]arene-modified graphene oxide composite films and their host–guest inclusions for enhanced electrochemical performance

In the present work, electrochemically reduced graphene oxide-cationic pillar[6]arene (ErGO-CP6) composite films on glassy carbon electrodes (GCEs) were prepared directly from graphene oxide-cationic pillar[6]arene (GO-CP6) dispersions by a facile one-step pulsed electrodeposition technique. The preparation of GO-CP6 and its subsequent electrochemical reduction were confirmed by Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy (UV-vis), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), zeta potential, Raman spectroscopy, and scanning electron microscopy (SEM). SEM result reveals that ErGO-CP6 could form a homogeneous film when GO-CP6 was electrodeposited on the surface of a GCE. Furthermore, Raman and XPS results confirm the removal of oxygen-containing functional groups present on the GO-CP6 surface after electrochemical reduction. Electrochemical results reveal that ErGO-CP6 films could show much higher electrochemical response to theophylline (TP), ascorbic acid (AA), acetaminophen (APAP), and folic acid (FA) than unmodified ErGO films and bare GCE, which is considered to be the synergistic effect of the graphene (excellent electrical properties and large surface area) and CP6 molecules (high inclusion complexation and enrichment capability).

Cationic pillar[6]arene functionalized graphene films with enhanced host–guest electrochemical recognition performance were fabricated directly from GO-CP6 dispersions by a one-step pulsed electrodeposition technique.