Current Nanoscience - Volume 16, Issue 4, 2020

By collecting and analyzing relevant literature results, we demonstrate that the nanostructuring of polypyrrole (PPy) electrodes is a crucial strategy to achieve high performance and stability in energy devices such as fuel cells, lithium batteries and supercapacitors. In this critic and comprehensive review, we focus the attention on the electrochemical methods for deposition of PPy, nanostructures and potential applications, by analyzing the effect of different physico-chemical parameters, electro-oxidative conditions including template-based or template-free depositions and cathodic polymerization. Diverse interfaces and morphologies of polymer nanodeposits are also discussed.

Background: Deep eutectic solvents (DESs) represent a new generation of ionic liquids which are widely promoted as “green solvents”. They are gaining widespread application in materials chemistry and electrochemistry. DESs are defined as eutectic mixtures of quaternary ammonium salt with a hydrogen bond donor in certain molar ratios. Their use as solvents for electrochemical synthesis of conducting polymers could influence the polymer properties and reduce their economic cost. Objective: This review presents the most recent results regarding the electropolymerization of common conductive polymers involving choline chloride based ionic liquids. New findings from our laboratory on the electrochemical growth of conductive polymers are also discussed. Methods: The electrochemical polymerization mechanisms during synthesis of polypyrrole (PPy), polyaniline (PANI) and poly(3,4-ethylenedioxythiophene) (PEDOT) using various formulations of DESs are reviewed, as well as their characteristics, mainly from surface morphology view point. Results: Some general information related to the preparation and characterization of DESs is also presented, followed by an overview of the recent advances in the field of electropolymerization using DESs. Conclusion: Electropolymerization of conducting polymers involving DESs represents an attractive route of synthesis due to their compositional flexibility which makes possible the preparation of unlimited formulations further influencing the polymer morphology and properties. The use of these inexpensive eutectic mixtures has a large potential to contribute to the development of more sustainable technological processes meeting many of the required features characteristic to the green chemistry.

This review article focused on fabrication of sensors by using a combination of highly ordered photonic crystals and molecular imprinted polymers as artificial recognition materials. In this article, we have discussed fundamental principle of photonic crystals, various synthetic approaches and their use in sensing applications. Moreover, nanostructuring of recognition materials, by using photonic crystals, for sensor fabrication and sensing mechanism has also been discussed. Molecular imprinted photonic polymer layers have been applied for developing sensor devices for diverse analytes such as environmental toxins, nerve gas agents, explosives, drug molecules and others. A comprehensive comparison of molecular imprinted photonic polymers based sensor systems has also been summarized in the table which contains all the related information about colloidal structure, polymer system including monomer, cross-linker and initiator as well as target analytes. Finally, emerging strategies and current challenges involved in the design of more efficient molecular imprinted photonic sensors and their possible solutions are also briefly discussed.

With the emergence of non-conventional energy resources and development of energy storage devices, serious efforts on lithium (Li) based rechargeable solid electrolyte batteries (Li- SEBs) are attaining momentum due to their potential as a safe candidate to replace state-of-the-art conventionally existing flammable organic liquid electrolyte-based Li-ion batteries (LIBs). However, Li-ion conduction in solid electrolytes (SEs) has been one of the major bottlenecks in large scale commercialization of next-generation Li-SEBs. Here, in this review, various challenges in the realization of high-performance Li-SEBs are discussed and recent strategies employed for the development of efficient SEs are reviewed. In addition, special focus is laid on the ionic conductivity enhancement techniques for inorganic (including ceramics, glasses, and glass-ceramics) and polymersbased SEs. The development of novel fabrication routes with controlled parameters and highperformance temperature optimized SEs with stable electrolyte-electrode interfaces are proposed to realize highly efficient Li-SEBs.

Environmental pollutants are considered as the main concern for human life because it can affect health, especially via water sources. An enormous effort is needed to detect and monitor such contaminants from natural waters. Nanotechnology field offered combined benefits in regards to sensitive detection of environmental contaminants from water. This review describes the main types of water contaminants and recent approaches used for effective electrochemical detection of environmental pollutants with the aid of nanostructured materials.

Due to its various advantages, colloidal quantum dots (CQDs) carry a prodigious deal of interest in low-cost photovoltaics. The possibility of tailored band gaps via quantum confinement effect facilitates photovoltaic devices to be tuned to allow their optical absorption bandwidths to match with the solar spectrum. Size, shape, and material composition are some of the significant factors which affect the optical and electronic properties of QDs. Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) are some of the most resourceful methods available for the microstructural characteristics of solid materials. These techniques can provide useful information about the structural, morphological and compositional properties of the specimen. In this focused review, we analyze the several types of QDs, their synthesis and characterization, exclusively morphological studies carried out on quantum dots for solar cell applications. Despite various advantages and techniques used for morphological characterization of QDs, very few reviews are reported in the past years. In this review, we have compiled the important and latest findings published on morphological analysis of QDs for photovoltaic applications which can provide the guideline for the research for the future work in the field.

Background: The photo-absorption and light trapping through the different layers of the organic solar cell structures are a growing concern now-a-days as it affects dramatically the overall efficiency of the cells. In fact, selecting the right material combination is a key factor in increasing the efficiency in the layers. In addition to good absorption properties, insertion of nanostructures has been proved in recent researches to affect significantly the light trapping inside the organic solar cell. All these factors are determined to expand the absorption spectrum and tailor it to a wider spectrum. Objective: The purpose of this investigation is to explore the consequence of the incorporation of the Ag nanostructures, with different sizes and structures, on the photo absorption of the organic BHJ thin films. Methods: Through a three-dimensional Maxwell solver software, Lumerical FDTD, a simulation and comparison of the optical absorption of the three famous organic materials blends poly(3- hexylthiophene): phenyl C71 butyric acid methyl ester (P3HT:PCBM), poly[N-9″-heptadecanyl-2,7- carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDTBT:PCBM) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt- 4,7-(2,1,3-benzothiadiazole)]: phenyl C71 butyric acid methyl ester (PCDPDTBT:PCBM) has been conducted. Furthermore, FDTD simulation study of the incorporation of nanoparticles structures with different sizes, in different locations and concentrations through a bulk heterojunction organic solar cell structure has also been performed. Results: It has been demonstrated that embedding nanostructures in different locations of the cell, specifically in the active layer and the hole transporting layer had a considerable effect of widening the absorption spectrum and increasing the short circuit current. The effect of incorporation the nanostructures in the active layer has been proved to be greater than in the HTL. Furthermore, the comparison results showed that, PCDTBT:PCBM is no more advantageous over P3HT:PCBM and PCPDTBT:PCBM, and P3HT:PCBM took the lead and showed better performance in terms of absorption spectrum and short circuit current value. Conclusion: This work revealed the significant effect of size, location and concentration of the Ag nanostructures while incorporated in the organic solar cell. In fact, embedding nanostructures in the solar cell widen the absorption spectrum and increases the short circuit current, this result has been proven to be significant only when the nanostructures are inserted in the active layer following specific dimensions and structures.

Background: The accurate energy yield prediction of a PV system under various environmental conditions is important for designing a high-performance PV system. Objective: The robust and cost-effective digital simulation studies on PV systems have the advantage in comparison to studies based on measurements because they provide the opportunity for sensitivity analysis on various design parameters of the PV system. Methods: Herein, we present the development and implementation of a generalized photovoltaic computational model using Matlab/Simulink software package. The model is based on the equivalent diode circuit approach. It is designed to simulate two ubiquitous and high performing 2nd generation photovoltaic (PV) modules constructed with Cadmium Telluride (CdTe) and Copper Indium Gallium di-Selenide (CIGS) photoactive thin films, respectively. The values of key input parameters to the simulator, i.e., parallel resistor (Rp) and series resistor (Rs) have been computed by an efficient Newton-Raphson iteration method. Results: The output current-voltage (I-V) and power-voltage (P-V) characteristic curves of the aforementioned PV modules have been simulated by taking two input variables (ambient irradiance and temperature) into consideration. The electrical performance of both PV modules under various environmental conditions have been mathematically investigated by the solution of classical non-linear equations. Conclusion: The developed PV model has been validated with the experimental results obtained from standard PV module datasheets provided by manufacturers. The relative error between the simulated and experimental values of various photovoltaic parameters for CdTe and CIGS PV modules at Standard Test Conditions (STC) has been observed to be below 3%.

Background: The development of new bioimplants with enhanced mechanical and biomedical properties have great impetus for researchers in the field of biomaterials. Metallic materials such as stainless steel 316L (SS316L), applied for bioimplants are compatible to the human osteoblast cells and bear good toughness. However, they suffer by corrosion and their elastic moduli are very high than the application where they need to be used. On the other hand, ceramics such as hydroxyapatite (HAP), is biocompatible as well as bioactive material and helps in bone grafting during the course of bone recovery, it has the inherent brittle nature and low fracture toughness. Therefore, to overcome these issues, a hybrid combination of HAP, SS316L and carbon nanotubes (CNTs) has been synthesized and characterized in the present investigation. Methods: CNTs were acid treated to functionalize their surface and cleaned prior their addition to the composites. The mixing of nano-hydroxyapatite (HAPn), SS316L and CNTs was carried out by nitrogen gas purging followed by the ball milling to insure the homogeneous mixing of the powders. In three compositions, monolithic HAPn, nanocomposites of CNTs reinforced HAPn, and hybrid nanocomposites of CNTs and SS316L reinforced HAPn has been fabricated by spark plasma sintering (SPS) technique. Results: SEM analysis of SPS samples showed enhanced sintering of HAP-CNT nanocomposites, which also showed significant sintering behavior when combined with SS316L. Good densification was achieved in the nanocomposites. No phase change was observed for HAP at relatively higher sintering temperatures (1100°C) of SPS and tricalcium phosphate phase was not detected by XRD analysis. This represents the characteristic advantage with enhanced sintering behavior by SPS technique. Fracture toughness was found to increase with the addition of CNTs and SS316L in HAPn, while hardness initially enhanced with the addition of nonreinforcement (CNTs) in HAPn and then decrease for HAPn-CNT-SS316L hybrid nanocomposites due to presence of SS316L. Conclusions: A homogeneous distribution of CNTs and SPS technique resulted in the improved mechanical properties for HAPn-CNT-SS316L hybrid nanocomposites than other composites and suggested their application as bioimplant materials.

Background: Al5083 has been basically used in marine and aerospace applications where it is intended for higher corrosion resistance and better weldability. Again this, Al5083 matrix has not been suitable for various other applications such as electrical contact brushes, cylinder liners, artificial joints and helicopter blades due to its poor wear resistance properties. Objective: The aim of this research is the optimization of wear rate of the composite with Al5083 matrix, reinforced with B4C (Boron carbide) particles, and it is achieved through the investigation of the subsequent effect: wt.% of the reinforcement, applied load and sliding speed. Methods: The material used for specimen is Al5083 and Al5083/B4C composite which is melted at 750°C in an induction furnace; the composite is prepared by stir casting technique. It was developed by an ex-situ technique. The liquid melt poured into preheated cast iron mould for carrying out the specimen preparation of wear testing. Results: The wear rate of Al5083/B4C composite is less than Al5083, the most influencing factor on wear rate is applied load and mechanism of deformation induced in the sliding surface of the pin was analysed by SEM (scanning electron microscope). Conclusion: Wear rate of Al5083 and Al5083/B4C composite increases with the increase of applied load, sliding speed and decreases as the wt. % B4C increases. The contribution of applied load is more in wear rate as compared to the other two factors and the value predicted by Taguchi, obtained by RSM (Response surface methodology) and evaluated by experiment are almost similar.

Catalysed by the success of mechanical exfoliated free-standing graphene, two dimensional (2D) semiconductor materials are successively an active area of research. Silicene is a monolayer of silicon (Si) atoms with a low-buckled honeycomb lattice possessing a Dirac cone and massless fermions in the band structure. Another advantage of silicene is its compatibility with the Silicon wafer fabrication technology. To effectively apply this 2D material in the semiconductor industry, it is important to carry out theoretical studies before proceeding to the next step. In this paper, an overview of silicene and silicene nanoribbons (SiNRs) is described. After that, the theoretical studies to engineer the bandgap of silicene are reviewed. Recent theoretical advancement on the applications of silicene for various field-effect transistor (FET) structures is also discussed. Theoretical studies of silicene have shown promising results for their application as FETs and the efforts to study the performance of bandgap-engineered silicene FET should continue to improve the device performance.

Background: Drug delivery technologies adjust drug release profile, absorption, distribution, and elimination for benefiting to the improvement of product efficacy, effectiveness, and safety. The IONPs release drugs via enzymatic activity, changes in physiological conditions such as pH, osmolality radiation, or temperature. In the case of nanoparticles that respond to the magnetic stimulus, the drug directs its action towards the site of a detected magnetic field. Objective: In this study, the synthesis of a specific drug-delivery system based on magnetic nanocarrier for teniposide as an anticancer drug is reported. The iron oxide@SiO2 core-shell nanoparticles were functionalized with APTS as a spacer then coupling to the DOTA molecules. Anticancer drug of teniposide conjugated to the acidic group of DOTA via an amide bond. Multi-purpose magnetic nanoparticles were synthesized for targeted delivery of teniposide. Methods: Iron oxide nanoparticles were firstly coated with silica and their surface was then modified with aminopropyltriethoxysilane (APTES) through an in situ method. DOTA-NHS was also coupled to Fe3O4@SiO2-APTES via an amide bond formation. In the final step, teniposide as an anti-cancer drug was conjugated with DOTA through ester bonds, and the final compound of Fe3O4@SiO2- APTES-DOTA-Teniposide was obtained. The obtained nanocarrier was evaluated by various analyses. Results: The multifunctional Fe3O4@SiO2-APTES-DOTA nanocarriers were successfully synthesized and characterized by XRD, FTIR, TGA, and UV-vis techniques. The silica-coated magnetic nanoparticle functionalized with aminopropyl triethoxysilane (APTES) was reacted with an acid group of DOTA, and teniposide was then coupled to DOTA through ester formation bonds. Drug release experiments showed that most of the conjugated teniposide were released within the first 12h. Conclusion: The fabricated nano-carriers exhibited pH-sensitive drug release behavior, which can minimize the non-specific systemic spread of toxic drugs during circulation whilst maximizing the efficiency of tumor-targeted anticancer drug delivery for this purpose. The prepared teniposidegrafted Fe3O4@SiO2-APTES-DOTA core–shell structure nanoparticles showed a magnetic property with exposure to magnetic fields, indicating a great potential application in the treatment of cancer using magnetic targeting drug-delivery technology and multimodal imaging techniques.

Background: 4-nitrophenol (4-NP) is one of the pollutants in sewage and harmful to human health and the environment. Cu is a non-noble metal with catalytic reduction effect on nitro compounds, and has the advantages of simple preparation, abundant reserves, and low price. Carbon nanotubes (CNT) are widely used for substrate due to their excellent mechanical stability and high surface area. In this study, a simple method to prepare CNT-Cu2O by controlling different reaction time was reported. The prepared nanocomposites were used to catalyze 4-NP. Methods: CNTs and CuCl2 solution were put into a beaker, and then ascorbic acid and NaOH were added while continuously stirring. The reaction was carried out for a sufficiently long period of time at 60°C. The prepared samples were dried in a vacuum at 50°C for 48 h after washing with ethyl alcohol and deionized water. Results: Nanostructures of these composites were characterized by scanning electron microscope and transmission electron microscopy techniques, and the results at a magnification of 200 nanometers showed that Cu2O was distributed on the surface of the CNTs. In addition, X-ray diffraction was performed to further confirm the formation of Cu2O nanoparticles. The results of ultraviolet spectrophotometry showed that the catalytic effect of the compound on 4-NP was obvious. Conclusions: CNTs acted as a huge template for loading Cu2O nanoparticles, which could improve the stability and cycle performance of Cu2O. The formation of nanoparticles was greatly affected by temperature and the appropriate concentration, showing great reducibility for the 4-NP reduction reaction.

Background: Porous carbon materials are promising candidate supports for various applications. In a number of these applications, doping of the carbon framework with heteroatoms provides a facile route to readily tune the carbon properties. The oxygen reduction reaction (ORR), where the reaction can be catalyzed without precious metals is one of the common applications for the heteroatom-doped carbons. Therefore, heteroatom doped catalysts might have a promising potential as a cathode in Microbial fuel cells (MFCs). MFCs have a good potential to produce electricity from biological oxidization of wastes at the anode and chemical reduction at the cathode. To the best of our knowledge, no studies have been yet reported on utilizing Sulfur trioxide pyridine (STP) and CMK-3 for the preparation of (N and S) doped ordered porous carbon materials. The presence of highly ordered mesostructured and the synergistic effect of N and S atoms with specific structures enhance the oxygen adsorption due to improving the electrocatalytic activity. So the optimal catalyst, with significant stability and excellent tolerance of methanol crossover can be a promising candidate for even other storage and conversion devices. Methods: The physico-chemical properties of the prepared samples were determined by Small Angle X-ray Diffraction (SAXRD), N2 sorption-desorption, Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM) and X-ray Photoelectron Spectroscopy (XPS). The prepared samples were further applied for oxygen reduction reaction (ORR) and the optimal cathode was tested with the Microbial Fuel Cell (MFC) system. Furthermore, according to structural analysis, The HRTEM, and SAXRD results confirmed the formation of well-ordered hexagonal (p6mm) arrays of mesopores in the direction of (100). The EDS and XPS approved that N and S were successfully doped into the CMK-3 carbon framework. Results: Among all the studied CMK-3 based catalysts, the catalyst prepared by STP precursor and pyrolysis at 900°C exhibited the highest ORR activity with the onset potential of 1.02 V vs. RHE and 4 electron transfer number per oxygen molecule in 0.1 M KOH. The high catalyst durability and fuel-crossover tolerance led to stable performance of the optimal cathode after 5000 s operation, while the Pt/C cathode-based was considerably degraded. Finally, the MFC system with the optimal cathode displayed 43.9 mW·m-2 peak power density showing even reasonable performance in comparison to a Pt/C 20 wt.%.cathode. Conclusion: The results revealed that the synergistic effect of nitrogen and sulfur co-doped on the carbon substrate structure leads to improvement in catalytic activity. Also, it was clearly observed that the porous structure and order level of the carbon substrate could considerably change the ORR performance.

Background: Active scholars in the nanofluid field have continuously attempted to remove the associated challenge of the stability of nanofluids via various approaches, such as functionalization and adding a surfactant. After preparing a stable nanofluid, one must measure the properties, as this is vital in the design of thermal systems. Objective: Authors aimed to investigate the stability and viscosity of refrigeration lubrication oilbased nanofluids containing functionalized MWCNTs. The effects of concentration and temperature on viscosity were studied. Furthermore, the present study focused on the effect of sonication time on the stability and viscosity of the prepared samples. Methods: After the preparation of chemically functionalized MWCNTs, solutions were dispersed with an ultrasonic homogenizer for 2, 4 and 8 hours sonication at maximum power. Viscosity measurements for all samples were made 10 minutes after sonication by adjusting the proper spinning velocity using a digital rotary viscometer. Results: The first part deals with the stability of the nanofluid as a nanolubricant, and the second one investigates the viscosity of the nanofluid and the effects of various parameters on it. The last one is related to the validation of the measured viscosity values by means of well-known empirical correlations. The measured data are given for validation issues. Conclusion: The samples will have higher stability by increasing the time of sonication. The viscosity of a nanofluid does not change with the increase of sonication time to two hours and higher. Up to mass concentration of 0.1%, the effective viscosity increases with adding nanotubes linearly.

Objective: The influence of Manganese (Mn2+) and Cobalt (Co2+) ions doping on the optical and magnetic properties of ZnO nanoparticles was studied. Methods: Nanoparticle samples of type ZnO, Zn0.97Mn0.03O, Zn0.96Mn0.03Co0.01O, Zn0.95Mn0.03 Co0.02O, Zn0.93Mn0.03Co0.04O, and Zn0.91Mn0.03Co0.06O were synthesized using the wet chemical coprecipitation method. Results: X-ray powder diffraction (XRD) patterns revealed that the prepared samples exhibited a single phase of hexagonal wurtzite structure without any existence of secondary phases. Transmission electron microscope (TEM) images clarified that Co doping at high concentrations has the ability to alter the morphologies of the samples from spherical shaped nanoparticles (NPS) to nanorods (NRs) shaped particles. The different vibrational modes of the prepared samples were analyzed through Fourier transform infrared (FTIR) measurements. The optical characteristics and structural defects of the samples were studied through Photoluminescence (PL) spectroscopy. PL results clarified that Mn2+ and Co2+ doping quenched the recombination of electron-hole pairs and enhanced the number of point defects relative to the undoped ZnO sample. Magnetic measurements were carried out at room temperature using a vibrating sample magnetometer (VSM). (Mn, Co) co-doped ZnO samples exhibited a ferromagnetic behavior coupled with paramagnetic and weak diamagnetic contributions. Conclusion: Mn2+ and Co2+ doping enhanced the room temperature Ferromagnetic (RTFM) behavior of ZnO. In addition, the signature for antiferromagnetic ordering between the Co ions was revealed. Moreover, a strong correlation between the magnetic and optical behavior of the (Mn, Co) co-doped ZnO was analyzed.