Improved OLED systems have great potential for next-generation display applications. Carbon nanotubes (CNTs) and the conductive polymers poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) have attracted great interest for advanced applications, such as optoelectronic products. In this paper, the simultaneous enhancement of the conductivity, roughness, and adhesion properties of transparent conductive films with PEDOT: PSS/CNTs is reported. These films prepared by a simple spin-coating process were successfully used to produce high-performance organic light-emitting diodes (OLEDs) with an improved lifetime. Addition of PEDOT: PSS lowered the film sheet resistance and CNTs helped to enhance the stability and maintain the lifetime of the OLEDs. In addition, treatment with methanol and nitric acid changed the morphology of the polymer film, which led to greatly reduced sheet resistance, enhanced substrate adhesion, and reduced film roughness. The best performance of the film (PEDOT: PSS: CNT = 110: 1, W/W) was 100.34 Ω/sq.@ 90.1 T%. High transmittance, low sheet resistance, excellent adhesion, and low roughness (3.11 nm) were achieved synchronously. The fabricated OLED demonstrated a low minimum operating voltage (3 V) and could endure high voltage (20 V), at which its luminance reached 2973 cd/m2. Thus, the incorporation of CNTs within PEDOT: PSS electrodes has great potential for the improvement of the performance of OLED devices.

Carbon nanotubes (CNTs) and graphene (Gr) are promising materials for flexible transparent conductive films (TCFs) in optoelectronic application because of their exceptional electrical, optical, and mechanical properties. Here, high-quality graphene nanosheets were synthesized by the one-step green method which using natural polyphenols-gallic acid (GA) as the exfoliation medium through high-pressure homogenization; besides, GA molecules can also be used as a non-covalent modifier to obtain GA modified CNTs (GCNTs). Then, the Au decorated Gr/GCNT-PET (Au-Gr/GCNT-PET) TCFs were obtained by a simple spray-coating process. The TCFs exhibited an excellent optoelectronic performance (Rs = 45.6 Omega/sq., T = ca. 80% at 550 nm), relatively flat surface (roughness = 12.43 nm), good bending resistance (the Delta R (Au-Gr/GCNT-PET TCF)/R-0 was 0.07 after 1000 times bending tests) and strong adhesion (the f(T) of all Au-Gr/GCNT PET films was higher than 0.8). Finally, the Au-Gr/ GCNT-PET films were used as an anode to prepare flexible green-light OLED devices; the maximum luminance of the Au-Gr/GCNT-PET device was 6554.1 cd/m(2) at 15V, and the maximum current efficiency was 4.03 cd/A. It confirmed that this type of TCFs has considerable potential application in photovoltaic devices.

A facile approach is reported to produce reduced graphene oxide (rGO) aerogel. The proposed approach involves the reduction of GO by utilizing the reduction capability of carbonic acid in soft drinks. The presence of carbonic acid reduces the oxygen functionalities in GO to produce rGO and simultaneously provides carboxyl groups for hydrogen bonding in the three-dimensional self-assembly of aerogel. It is also proven that the as-synthesized rGO aerogel possesses a pseudocapacitive effect, owing to the presence of carboxyl groups. This facile reduction approach by an easily available source successfully produces rGO aerogel with 20-fold charge storage capacity enhancement (121 F/g at 0.4 A/g) as compared to the GO. It suggests this facile approach has great potential to construct lightweight graphene aerogel for energy storage applications.

Herein, we demonstrated for the first time the green fabrication of graphene by wet ball milling method which utilizes natural honey as exfoliation medium, further the 3D conductive networks (Graphene/Carbon nanotubes/PEDOT:PSS, G/CNT/PEDOT:PSS) were integrated into the biodegradable Starch/Chitosan/Poly vinyl alcohol (S/C/PVA) substrates. This electrode possesses an excellent optoelectronic performance (Rs = 43.2 Omega/sq., T = ca. 80% at 550 nm), and a very low Root Mean Square (RMS) roughness (approximately 1.38 nm). The sheet resistance of the films changed slightly after 1000 bending cycles and adhesion tests. The flexible green light OLED using G/CNT/PEDOT:PSS-S/C/PVA film as anode was successfully fabricated, the luminance of the device was 5701 cd/m(2) at 15 V and the maximum current efficiency was 3.75 cd/A at 13 V. Moreover, this new type of OLED device degrades gradually within 10 min in 2 wt% lysozyme CH3COOH solution, which could be used to prepare the next generation of user-friendly, eco-friendly flexible wearable electronic devices. (C) 2020 Elsevier Ltd. All rights reserved.

In this paper, we used tannic acid (TA) functionalized carbon nanotubes (TCNTs), and silver nanowires (AgNWs) to construct a new type of transparent conductive film (TCF) with a double-layered conductive network structure. The hybrid film exhibits excellent light transmittance, high electrical conductivity, ultra-flexibility, and strong adhesion. These outstanding performances benefit from the filling and adhesion of hydrophilic TCNT layers to the AgNW networks. Besides, we introduced the post-treatment process of mechanical pressing and covering polymer conductive polymer PEDOT:PSS, which obtained three layers of TCNT/AgNW/PEDOT hybrid film and greatly improved the comprehensive properties. The hybrid film can reach a sheet resistance of 9.2 Ω sq−1 with a transmittance of 83.4% at 550 nm wavelength, and a low root mean square (RMS) roughness (approximately 3.8 nm). After 10 000 bends and tape testing, the conductivity and transmittance of the hybrid film remain stable. The resistance of the film has no significant degradation after 14 d of exposure to high temperature of 85 °C and humidity of 85%, indicating excellent stability. The organic light-emitting diodes (OLEDs) with TCNT/AgNW/PEDOT hybrid film as anode exhibit high current density and luminosity, confirming this process has considerable potential application in photovoltaic devices.

In this paper, the eco-friendly plant polyphenol, tannic acid (TA) was demonstrated as a non-covalent modifier for carbon nanotubes (CNTs), as well as a stripping medium to achieve exfoliated graphite to graphene by microfluidization. High-performance transparent flexible heater (TFH) with an embedded structure had been successfully fabricated by integrating conductive nanocomposites (TA-functionalized grapheme/TA-functionalized CNT/PEDOT:PSS; TG/TCNT/PEDOT) into waterborne polyurethane (WPU) film. Such a film exhibited favorable optical transmittance and sheet resistance (T = ca. 80% at 550 nm, Rs = 62.5 Ω/sq.), low root mean square (rms) roughness (approximately 0.37 nm), excellent adhesion and mechanical stability (the sheet resistance remained almost constant after 1000 bending cycle test for the bending radius of 10 mm), which are ideal as transparent heaters with high thermal efficiency. For TG/TCNT/PEDOT-WPU TFHs, the temperature increased rapidly and reached a steady state within 20 s with the maximum temperature reached to 116 °C, when the applied voltage was 20 V. Moreover, no variation in temperature was observed after the repeated heating-cooling tests and long-time stability test, indicating that TG/TCNT/PEDOT-WPU TCFs can be used as high performance TFHs. These TFH's are expected to be suitable for vehicle defrosting, smart windows, portable heating, smart wearable devices, etc.

In this study, the degradation of phenolic compounds was performed in the presence of pure and Cu doped nickel oxide (Cu-NiO) nanocatalysts. A wet chemical method was utilized for the catalyst preparation. The crystallinity and phase were determined using X-ray diffraction, optical properties were analyzed by UV-Vis spectroscopy and morphology was analyzed by a transmission electron microscope. Fourier transform infrared spectroscopy confirms the formation of pure NiO and the existence of copper in doped nanocatalyst samples. Cu-NiO nanocatalyst samples showed a reduction in average crystallite size as compared to pure NiO sample, where it was 24.0, 22.8 and 19.03 nm for 2Cu-NiO and 4Cu-NiO, respectively. The average particle size as determined by using transmittance electron microscopy were about 28.0, 26.6 and 22.8 nm for NiO, 2Cu-NiO and 4Cu-NiO, respectively. In addition, the energy bandgap values were found to be 3.26, 3.64 and 3.87 eV for undoped NiO, 2Cu-NiO and 4Cu-NiO, respectively. Comparative study of the photocatalytic performance of Cu-NiO and pure NiO were systematically performed at various reaction times and Cu doping ratios (2-4 wt.%). Different molar concentrations of phenol were also considered for this study. The obtained results showed that the Cu-NiO nanocatalyst exhibited the highest phenol degradation efficiency as compared to their undoped counterpart. This material is first reported and successfully used in efficient removal of phenol from real industrial effluent. The nanocatalyst efficiency for phenol removal was tested in real leather industrial wastewater effluent which could remove about 85.7% within 150 min.

High performance, flexible transparent conductive films with a structure similar to that of reinforced concrete and constructed by sandwiching single-walled carbon nanotubes (SWCNT) between poly (3,4-ethylene dioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) and polydopamine functionalized reduced graphene oxide (PDA-RGO) were fabricated using simple spray coating. Mussel-inspired polydopamine was introduced as a graphene oxide reducing agent and modifier; the obtained PDA-RGO improved the interfacial adhesion between the conductive coating layers and substrate, and an effective post fabrication treatment method was performed on the hybrid film to achieve better conductivity. It was found that the resulting electrode exhibited a low sheet resistance of 52.2 Omega/sq. with a high optical transmittance of 88.7% at 550 nm. Moreover, the transparent film exhibited long-term stability with a relatively low roughness (ca. 2.41 nm), and its architectural structure sustained the flexibility of the film during bending. The organic light emitting diodes which using PDA-RGO/SWCNT/PEDOT:PSS film as anode was successfully fabricated, the luminance of the device was 2032 cd/cm(2) at 15 V and the maximum current efficiency was 2.13 cd/A at 14 V, indicating the strong potential of this type of transparent electrode for flexible electroluminescent devices.

Carbon nanotubes (CNTs) and poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) were employed to prepare sandwich-structured CNT/PEDOT:PSS/CNT transparent conductive films (TCFs) on flexible polyethylene terephthalate (PET) substrate by a spraying method. Based on the film morphology, we suggest that the CNTs were embedded in PEDOT:PSS. The structured film was more stable and did not peel off during post-processing nitric acid treatment. Ethylene glycol (EG) was used to improve the conductivity of the film, and the best ratio of PEDOT:PSS to EG was 10:5. XPS and Raman spectroscopy studies revealed that the non-conductive sodium dodecylbenzene sulfonate and PSS were removed during the nitric acid treatment. TCF sheet resistance as low as 95.15 Ω/sq at 87.72% transmittance (at a wavelength of 550 nm) was obtained. When the CNT/PEDOT:PSS/CNT-TCF was used as an anode in an organic light emitting diode, the high luminance of the device was 1598 cd/cm2 at 14 V, and the maximum current efficiency was 1.5 cd/A at 13 V.

This work reports variation of Cu doping concentration in NiO nanoparticles (NiO: Cu NPs) synthesized via chemical co-precipitation from solution by using NiCl2.6H(2)O as precursor, CuSO4.5H(2)O as dopant and NaOH as surfactant. We studied optical and thermal stability of prepared NiO: Cu NPs by UV-Vis absorbance, Diffuse Reflectance Spectroscopy (DRS), Atomic Absorption Spectroscopy (AAS), and Thermo Gravimetric/Differential Scanning Calorimetry (TGA/DSC) analyses. Optical absorption data of NiO: Cu NPs indicated strong absorption peaks shifted towards blue with respect to the peak of undoped NiO NPs due to quantum confinement effect. The bandgap estimated via Tauc plot first increased from 3.32eV (undoped NiO NPs) to 3.37 eV (8 at % of Cu in NiO NPs) and further increase of Cu doping to 10 at% reduced the bandgap to 3.35 eV. Such behavior of the bandgap clearly indicates that the size of NiO NPs first reduces with Cu doping up to 8 at % and then increases with further Cu doping to 10 at %. This behavior of reduction in particle size with increased doping can be attributed to the dislocation density and microstrain developed in NiO: Cu NPs. Thermal stability analysis demonstrated that in addition undoped NiO NPs, all NiO: Cu nanoparticle samples exhibited good thermal stability.

Graphene-based metal oxides such as Cu2O, SnO2, CuO, Fe3O4, MnO2 are promising candidates for many applications because of their advantageous properties. Amongst all, CuO has been widely studied because of its excellent electrocatalytic activity. Although many methodologies have been developed for the synthesis of CuO/graphene nanostructures with different morphologies including nanorods, nanoparticles, nanosheets, flower, urchin; not many investigations have been done on one pot synthesis method for CuO/reduced graphene oxide (rGO) nanocomposites to achieve different morphologies. Therefore in the present work effort has been made to synthesize various CuO-rGO nanocomposites via surfactant (CTAB) assisted hydrothermal method. Detailed study was performed to monitor the effect of various reaction parameters like temperature, reaction time, reactant concentration on the synthesized nanocomposites. Several analytical tools, including XRD, SEM, FTIR and UV-Vis spectroscopy have been utilized to characterize the samples. XRD results showed formation of monoclinic structure of CuO along with presence of rGO. Calculated optical bandgap studies indicate decrease in the bandgap of synthesized CuO (E-g= 4.5eV-4.34eV) with increase in temperature from 120 degrees C to 180 degrees C. Our results clearly demonstrate that reaction parameters play a key role to bring out the optical and morphological changes in the CuO-rGO nanocomposites.

In the present study, NiO and Cu-doped NiO nanoparticles were successfully synthesized by wet chemical method at room temperature using sodium hydroxide (NaOH) as precipitating agent. The as-prepared Cu-doped NiO powder samples were subjected to three different calcination temperatures such as, 350°C, 450°C and 550°C in order to investigate the impact of calcined temperatures on the phase formation, particle size and band gap evolution. The phase formation and crystal structure information of the prepared nanomaterials were examined by X-ray powder diffraction (XRD). XRD revealed the face-centered cubic (FCC) structure. Average crystalline size of pure and doped samples estimated using Scherer formula was found to be 15nm and 9nm respectively. With increase in the calcination temperature from 350°C to 550°C for the Cu doped NiO samples the particle size of the nanoparticles was found to increase from 4nm to 9nm respectively. The optical study for both pure and doped NiO nanoparticles was performed using an UV–Vis spectrophotometer in the wavelength range of 200–800nm. The strong absorption in the UV region confirms the band gap absorption in NiO and was estimated from the UV–Vis diffuse reflectance spectra via Tauc plot. Systematic studies were also carried out to study the effect of calcination on the optical transmittance. Samples were also investigated using Raman and Fourier Transform Infrared Spectroscopy (FTIR). Furthermore, morphology of the pure NiO and Cu-doped NiO Nanoparticles were examined by scanning electron microscope (SEM).

Carbon nanospheres derived from a natural source using a green approach were reported. Lablab purpureus seeds were pyrolyzed at different temperatures to produce carbon nanospheres for supercapacitor electrode materials. The synthesized carbon nanospheres were analyzed using SEM, TEM, FTIR, TGA, Raman spectroscopy, BET and XRD. They were later fabricated into electrodes for cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy testing. The specific capacitances were found to be 300, 265 and 175 F g-1 in 5 M KOH electrolyte for carbon nanospheres synthesized at 800, 700 and 500 °C, respectively. These are on a par with those of prior electrodes made of biologically derived carbon nanospheres but the cycle lives were remarkably higher than those of any previous efforts. The electrodes showed 94% capacitance retention even after 5200 charge/discharge cycles entailing excellent recycling durability. In addition, the practical symmetrical supercapacitor showed good electrochemical behaviour under a potential window up to 1.7 V. This brings us one step closer to fabricating a commercial green electrode which exhibits high performance for supercapacitors. This is also a waste to wealth approach based carbon material for cost effective supercapacitors with high performance for power storage devices.

The present work demonstrates the operation and performance of double barrier Graphene Antidot Resonant Tunnel Diode (DBGA-RTD). Non-Equilibrium Green's Function (NEGF) frame work with tight-binding Hamiltonian and 2-D Poisson equations were solved self-consistently for device study. The interesting feature in this device is that it is an all graphene RID with band gap engineered graphene antidot tunnel baniers. Another interesting new finding is that it shows negative differential resistance (NDR), which involves the resonant tunneling m the graphene quantum well through both the electron and hole bound states. The Graphene Antidot Lattice (GAL) harriers in this device efficiently improved the Peak to Valley Ratio to approximately 20 even at room temperature. A new fitting model is developed for the number of antidots and their corresponding effective barrier width, which will help in determining effective barrier width of any size of actual antidot geometry.

A unique way to control the size and antibacterial activities of silver nanoparticles (Ag NPs) using three different leaf conditions (fresh, oven-dried and sun-dried) of Alstonia scholaris has been reported in this paper. The extract of the A. scholaris leaf acts both as a reducing and stabilizing agent in the formation of Ag nanoparticles. The characteristic surface plasmon peak (415nm), X-ray diffraction (XRD) studies and energy dispersive spectroscopy (EDS) confirmed the formation of crystalline green Ag nanoparticles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that there was a difference in size for the Ag NPs synthesized from different leaf conditions. Antibacterial studies with both Gram-positive and Gram-negative bacteria showed that Ag NPs synthesized from the fresh leaves displayed the best antibacterial activity, which can be attributed to the size effect of the nanoparticles.

To make use of exceptional properties of graphene in Field effect Transistor (FETs) for switching devices a band gap must be introduced in order to switch-off the device, Through periodic nano perforations a semi-metallic graphene is converted into semiconducting graphene. To understand the device physics behind the reported experiments theoretical simulations has been carried out, The present paper illustrates nano perforated semiconducting graphene Field effect Transistor (FETs) with micron scale dimensions, The simulation has been performed using drift-diffusion semi-classical and tight-binding based non-equilibrium green's function (NEGF) methods, The obtained simulation results are compared with previously reported experimental work. The device dimensions considered for simulations and the experiment are similar with neck width, hole periodicity and channel length of 6.3 nm, 16.3 nm and 1 mu m respectively. The interesting and new finding in this work is the p-type I-V characteristics for small band gap devices and n-type behavior for large band gap devices.

In this article a double-barrier resonant tunnelling diode (DBRTD) has been modelled by taking advantage of single-layer hexagonal lattice of graphene and hexagonal boron nitride (h-BN). The DBRTD performance and operation are explored by means of a self-consistent solution inside the non-equilibrium Green’s function formalism on an effective mass-Hamiltonian. Both p- and n-type DBRTDs exhibit a negative differential resistance effect, which entails the resonant tunnelling through the hole and electron bound states in the graphene quantum well, respectively. The peak-to-valley ratio of approximately 8 (3) for p-type (n-type) DBRTD with quantum well of 5.1 nm (4.3 nm) at a barrier width of 1.3 nm was achieved for zero bandgap graphene at room temperature.

The present work is focused on the investigation of thioglycerol (TO) stabilized Zinc Sulfide Quantum dots (ZnS QDs) in the hybrid electroluminescence (EL) device. Optical absorption spectroscopy clearly indicates the formation of narrow size distributed ZnS in the quantum confinement regime. X-ray Diffraction (XRD), Photoluminescence (PL), Energy Dispersive X-ray Spectroscopy (EDS) data supports the same. The hybrid EL device with structure of ITO (indium tin oxide)//PEDOT:PSS ((poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)//HTL (alpha NPD- N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-phenyl)-4,4'-diamine//PVK:ZnS QDs//EIL(PBD-2-tert-butylpheny15-biphenyl-1,3,4-oxadiazole)//LiF:Al (Device 1) was fabricated. Reference device without the ZnS QDs were also prepared (Device 2). The results show that the ZnS QDs based device exhibited bright electroluminescence emission of 24 cd/m(2) at a driving voltage of 16 Volts under the forward bias conditions as compared to the reference device without the ZnS QDs, which showed 6 cd/m(2) at similar to 22 Volts.

Removal of heavy metals from industrial wastes has been an important environmental research area. In the present study a mixture of two different types of biosorbent for removal of copper from water was investigated. Three types of biosorbents were tested i.e. EG, UA and a combination of both (EG+UA). The batch scale studies were carried out to study the effect of pH, metal concentration and contact time on adsorption capacity. Maximum removal percentage of Cu (II) by EG was about 99% at pH 5 UA and EG+UA got the maximum removal of Cu of about 68%, 74% at pH 8 respectively. In the metal concentration studies EG and UA adsorbed the increased concentration of Cu (II), the combination of adsorbents showed 79.8% adsorption for Cu at 100mg/L and for other concentrations of 200mg/L, 300mg/L, 400mg/L and 500mg/L it showed 68.6%, 67.6%, 58.8 and 57.1% respectively. The maximum Cu (II) removal exhibited by the EG+UA combination was 79.85% obtained for the optimal contact time of 120 min. EG showed Cu (II) removal was maximum up to 99% and UA showed the removal was maximum up to 84% with the contact time 120 min. The morphology characterization of the three adsorbent systems was investigated using the Scanning Electron Microscope (SEM). The Langmuir isotherm was found to be the best-fitting isotherm which indicates the experimental values match with the theoretical reported values. In the kinetic studies the higher R2 values confirm that the adsorption data are well explained by pseudo second order kinetics.