Current Nanoscience - Volume 17, Issue 1, 2021

A new kind of two-dimensional (2D) material MXene (early transition metal carbides, nitrides and carbonitrides) is obtained by selective etching the A element from the MAX phases. MXene exhibits both the metallic conductivity and the hydrophilic nature due to its metal layer structure and hydroxyl or oxygen terminated surfaces. This review provides an overview of the MXene used in the electrolytes and electrodes for the fuel cells and water splitting. MXene with functional groups termination could construct ion channels that significantly benefit ion conductivity through the electrolyte. The metal supported by MXene interaction offers electronic, compositional, and geometric effects that could enhance the catalytic activity and stability. MXene has already shown promising performance for fuel cells and water electrolysis. Herein, the etching and intercalation methods of MXene in recent years are summarized. The applications of MXene for fuel cells electrolyte, catalyst and water splitting catalyst are revealed to provide a more brief idea for MXene used as new energy materials.

Background: A semisolid gel-like preparation constitutes with the cross-linked polymers, which may easily swell in the presence of water and incorporate the amount of drug substance known as ‘Hydrogel.’ Objective: To prepare the review on the hydrogels, leading ennoblements, classification, mechanism, recent patents, and evaluation parameters. Methods: This review accrued by taking the help of online and offline journals, books, and other sources. This field includes new developments in the field of inventions in the novel drug delivery of hydrogels. Results: The impact of the formulation of hydrogels is attracting the focus of the researchers expeditiously because of their nature, three-dimensional structure, compatibility with the other excipients was found enormously useful in the biomedical applications and pharmaceutical industries, less time consuming, better sustained and prolonged the effect. Currently, hydrogels are growing expeditiously for the intensive work done by the use of natural, synthetic, and semi-synthetic polymers for the transformation of hydrophobic and hydrophilic drugs into hydrogels as compared to develop the conventional gels. Conclusion: The journey of hydrogel goes through with the numerous inventions research papers, reports, publications, and many other sources. The development arouses with the hydrogels in the use of wound dressing, making diapers, contact lens, etc. Nowadays, it is pivotally growing in the field of tissue engineering scaffolds, preparation of hydrophobic drugs into hydrogels, which is a critical challenge in prompt conditions.

Bacterial infections result in hundreds of million cases of severe illness annually worldwide. Rapidly increasing drug resistance of pathogens further aggravates this threat to human health and warrants the search for effective broad-spectrum antibacterial agents. Silver metal has a long history of application in human medicine and healthcare. In ancient times, silver was employed as a disinfectant for water purification and storage while it is still being used as an antimicrobial ingredient in some nanotechnology-based products. Encapsulation of antimicrobial substances such as silver nanoparticles in nanoliposomes could provide protection and targeting for the encapsulated or entrapped material. Nanoliposomes are biocompatible and biodegradable drug delivery systems with the ability to encapsulate both lipid-soluble and water-soluble compounds, as well as metal ions. Furthermore, nanoliposomes have been shown to be able to deliver encapsulated agents to target bacteria in vitro as well as in vivo. In this review, we present the use of nanoliposome-encapsulated silver nanoparticles as an efficient system for antibacterial applications.

Background: With the gradual decrease in fossil energy, the development of alternatives to fossil energy has attracted more and more attention. Biodiesel is considered to be the most potent alternative to fossil energy, mainly due to its green, renewable, and biodegradable advantages. The stable, efficient and reusable catalysts are undoubtedly the most critical in the preparation of biodiesel. Among them, nanoporous carbon-based acidic materials are very important biodiesel catalysts. Objective: The latest advances of acidic nanoporous carbon catalysts in biodiesel production was reviewed. Methods: Biodiesel is mainly synthesized by esterification and transesterification. Due to the important role of nanoporous carbon-based acidic materials in the catalytic preparation of biodiesel, we focused on the synthesis, physical and chemical properties, catalytic performance and reusability. Results: Acidic catalytic materials have a good catalytic performance for high acid value feedstocks. However, the preparation of biodiesel with acid catalyst requires relatively strict reaction conditions. The application of nanoporous acidic carbon-based materials, due to the support of carbon-based framework, makes the catalyst exhibit good stability and unique pore structure, accelerates the reaction mass transfer speed, which in turn accelerated the reaction. Conclusion: Nanoporous carbon-based acidic catalysts have the advantages such as, suitable pore structure, high active sites, and high stability. In order to make these catalytic processes more efficient, environmentally friendly and low cost, developing new catalytic materials with high specific surface area, suitable pore size, high acid density, and excellent performance would be an important research direction for the future biodiesel catalysts.

Nano-biotechnology is gaing attention in the field of agriculture because of its different applications such as release of nutrients, pesticides, nanosensors, veterinary care, detection of nutrient deficiencies and many more. Nanoparticles, measured in nano size, is used in variety of forms to improve the efficiency of nutrient utilization and reduces the costs of environmental protection. Nano fertilizer, one of the important aspect of nanoparticles. It facilitates incorporation of measured amount of nutrition to the crops which reduces the chance of nutrition loss, thus helps to improve crop fertility. Toxic waste from soil and water can also be reduced by the use of different agrichemicals. Nanotechnology has the potential to detect the disease at an early stage and also improves the ability of plants to uptake nutrients, thus improving agriculture and food industry. This review covers the use of different nanoparticles in agriculture as plant growth promoters and their use in controlling plant diseases.

Background: Polymeric nanomaterials are important for developing drug delivery systems. The control of nanoparticle size, polydispersity, and morphology in these systems are important goals. Therefore, different strategies have been explored depending on the type of materials used. Objective: To prepare biodegradable segmented poly(urea)urethane nanoparticles and to optimize the nanoparticle size and polydispersity using an experimental design methodology. Methods: In this work, a biodegradable segmented poly(urea)urethane (SPUU) was synthesized. This polymer was used for nanoparticle preparation by the nanoprecipitation technique in the context of the experimental design methodology Taguchi L9. SPUU and nanoparticles were characterized using Fourier transformed infrared, proton nuclear magnetic resonance, transmission electron microscopy, scanning electron microscopy, and dynamic light scattering. Results: This methodology produced polymeric nanoparticles with mean sizes in the range of 60 to 220 nm with polydispersity in the range of 0.077 to 0.233. The statistical analysis showed that the SPUU concentration and the stirring speed were the most influential parameters, while temperature, at the studied range, did not show a relevant effect. Conclusion: The analysis of Taguchi’s experimental design resulted in the optimization of parameters determining SPUU-NPs’ size. Nanoparticles from 60 nm of effective diameter were obtained at low polymer concentration and higher stirring speed.

Background: The existing methods of analyte detection by various biochemical processes have certain drawbacks including nonlinearity and detection limits. The nanotechnology has paved a way for the development of new devices i.e., nano-biosensors, by amalgamation of nanoparticles with recognition elements. These nano-biosensors have the capabilities to overcome the drawbacks of conventional methods. Objectives: Present study was planned to analyze the biosensing potential of indium tin oxide (ITO) electrode modified with gold nanoparticles synthesized using aqueous extract of S. podophyllum. Methods: In present study, first time rapid green synthesis of gold nanoparticles from leaf extract of Syngonium podophyllum is reported. The synthesized nanoparticles were then characterized physically by UV-Visible spectroscopy, particle size analysis, fluorescent spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy (TEM), and HR (High resolution)-TEM. Results: The particles were observed to be in average size range of 30-70 nm. Furthermore, the ITO electrode was modified with the prepared nanoparticles and analyzed by ellipsometry. The electrochemical characteristics of the modified electrodes were analyzed by cyclic voltammetry. Conclusion: The results exhibited a higher current gain, thus signifying a higher signal amplification at the electrodes and paves the way for their use in electrochemical nanobiosensors.

Background: Photocatalytic oxidation of organic pollutants in the environment is being studied for more than half a century. Titanate has the activity on the degradation of organic pollutants under UV light illumination. Template directed sol-gel method is capable of producing porous structure in titanate during high temperature thermal treatment. Methods: The materials were characterized using X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, surface area and pore size analyses, UV-Visible spectrometry, and Xray photoelectron spectroscopy. Photocatalytic activity of the CeTi2O6 material was evaluated through ofloxacin degradation. Results: Brannerite structured CeTi2O6 was the major component in the samples, and the addition of CTAB caused a slight growth of CeTi2O6 crystals. Porous structure formed in the porous sample after the removal of CTAB template, and the surface area and pore volume were greatly enlarged. The first order reaction rate constant for photocatalytic degradation of ofloxacin was 9.60×10^-3 min-1 on the nonporous CeTi2O6 sample, and it was as large as 2.44×10^-2 min^-1 on the porous CeTi2O6 sample. The addition of CTAB can influence the physico-chemical properties of the porous CeTi2O6, such as the improved activity on photocatalytic degradation of ofloxacin. Conclusion: The CeTi2O6 samples composed of majority brannerite CeTi2O6, and CeTi2O6 crystallite sizes for the nonporous and porous samples were 38.1 and 43.2 nm. The burning up of CTAB during calcination produced abundant pores in the porous material. After 50 min of reaction, photocatalytic degradation efficiencies on the nonporous and porous CeTi2O6 samples were 38.1% and 70.5%.

Background: The study on explosive boiling phenomenon has received increasing attention because it involves many industries, such as advanced micro-, nano-electromechanical and nano-electronic cooling systems, laser steam cleaning, and so on. Objective: In the present work, the explosive boiling of ultra-thin liquid film over two-dimensional nanomaterial surface in confined space with particular emphasis under the three different influencing factors: various heights of nanostructures, various wetting conditions of solid-liquid interface as well as various heat source temperatures. Methods: Molecular Dynamics simulations (MDs) in present work have been adopted to simulate the whole explosive boiling process. Results: For different heat source temperature case, the higher the heat temperature is, the less time the explosive boiling spends after relaxation. For nanostructure case, nanostructure surface significantly increases heat transfer rate and then leads to the increase of phase transition rate of explosive boiling. For different wetting property case, the increase of surface wettability results in an increase of phase transition to some degree. Conclusion: The addition of nanostructures, the higher heat source temperature and good wettability between thin liquid film and substrate surface dramatically improve thermal heat transfer from solid surface to liquid film, which will give rise to explosive boiling occur. In addition, the non-vaporized argon layer still exists in these three factors despite continuous thermal transmission from the substrate surface to liquid argon film adjacent to the solid surface even other vaporized argon atoms.

Background: One-dimensional titania nanotubes (TNT) have attracted increasing scientific and technological attention due to their physical properties and their potential applications. Dimensionality and well-aligned ordered structure have a crucial role in determining the properties and performance of titania nanotubes. Therefore, an understanding of the transformation and growth mechanisms to explain the origin of this nanomaterial symmetry is of great importance. Objectives: The relationship between the direction of current flow and the morphology of the anodized foil was investigated to understand the influence of a compact oxide layer formation on the growth of nanotubes. Methods: To achieve the purpose, single (SA) and double-sided anodization (DA) were performed to control the direction of the current flow in this experiment by immersing one side and both sides, respectively in the electrolyte containing 0.6 wt% of NH4F, 1.0 wt% of H2O2, and 98.4 wt% of ethylene glycol (EG) at 60V. Results: It was found that the channeling of current flow into axial and radial directions influenced the effectiveness of oxygen species in the formation of an initial oxide layer. The field-assisted dissolution of the compact oxide layer resulted in a low-symmetry nanotube arrangement, whereas the growth at the interface, which is governed by the plastic flow mechanism, resulted in high-symmetry nanotube arrangement in a hexagonal form. These findings offer an integrated perspective when determining whether the plastic flow mechanism or field-assisted dissolution occurs during anodization. Octahedral titania crystals were also found on the surface of the anodized film, indicating the possibility of forming facet structures via anodization. Conclusion: This research successfully showed the influence of current flow via SA & DA on the growth of TiO2 nanotubes. An axial flow of current in Ti foil during SA resulted in disordered nanotubes, while the radial flow of current during DA stemmed the growth of nanotubes from the Ti-TiO2 interface to form well oriented hexagonal nanotube structures.

Background: Different photocatalysts such as TiO2, ZnO and WO3 have been used for the degradation of organic pollutants. However, these materials have some limitations, which have been affected the catalytic efficiency in the various transformations. The composites of these materials with other oxides can produce better results by tuning structural as well as optoelectrical properties. The composite of TiO2 with ZrO2 has attracted attention due to its use in different areas, as ZrO2 and TiO2 have similar physicochemical features. Methods: This research contains the preparation of ZrO2-TiO2 nanocomposites by hydrothermal method and analysis of photocatalytic activity for the degradation of methylene blue and a mixture of dyes under visible light irradiation. Results: Physicochemical characterization of ZrO2-TiO2 nanocomposites has been studied by using different techniques. Prepared catalysts has shown anatase phase of TiO2 and tetragonal phase of ZrO2. XRD, FESEM and HRTEM have supported the nanocrystalline nature of the composites. The photocatalytic activity of composites and bare TiO2 samples were demonstrated for the degradation of methylene blue dye. Enhanced activity has been shown by composite having Ti:Zr 3:1 molar proportion, i.e., Ti3Zr. Effect of concentration of methylene blue, pH of the solution and catalyst loading have been studied by using Ti3Zr. In addition, the degradation of a mixture of three dyes, namely methylene blue, rhodamine B and methyl orange, has been studied. Conclusion: In summary, prepared ZrO2-TiO2 composites found to be nanocrystalline and visible light active. These catalysts have shown activity for photocatalytic degradation of methylene blue and a mixture of dyes.

Background: In this study, experimentally, we fabricated the FASnI3 perovskite solar cells based on the SnF2 and SnF4-doped FASnI3 nano-thin film materials, and obtained the photoelectric conversion efficiency (PCE) as 6.5 % and 5.59 %, respectively. Theoretically, we wanted to know why the PCE of SnF2-doped FASnI3 is higher than the SnF4-doped FASnI3. Methods: We built three kinds of model structures by the CASTEP; they were undoped and SnF2 and SnF4 doped FASnI3 perovskite structure models, respectively. The method was ultrasoft to calculate the interaction between electron and ion, including an electron exchange correction method of generalized gradient approximation and Perdew-Burke-Emzerhof method. Results: We found the probabilities of energy transfer between SnF2 molecules and the surrounding molecules and these were found to be the lowest among the three structures. By analyzing optical properties, band structures, effective masses, and density of states (DOS), etc., we found SnF2 doping to be superior to SnF4 doping in maintaining photoelectric properties of FASnI3. In addition, SnF2- doped FASnI3 possessed smaller hole effective mass than SnF4-doped FASnI3, adding Sn4+ ion into perovskite, as a shallow acceptor energy level can effectively reduce the optical absorption properties, however, adding Sn²⁺ ion into perovskite at an appropriate proportion enhanced photoelectric performance of FASnI3. Conclusion: Sn⁴⁺ doping exhibited a negative effect, while Sn²⁺ doping showed a positive effect in promoting the photoelectric performance of FASnI3 perovskite. We found SnF2 doping to be superior to SnF4 doping in maintaining photoelectric properties of FASnI3 . Our results may help to deeply understand the role of Sn²⁺ and Sn⁴⁺ ions in promoting the stability and high efficiency of FASnI3, and help in developing lead-free perovskite solar cells.

Background: Filamentous bacteriophages such as M13 are an important class of macromolecular assembly, rich in chemical moieties that can be used to impart modifiable positions at the nanoscale. Objective: To explore the structurally more complex Pf1 bacteriophage with respect to a diverse set of bioconjugation reactions and to prepare novel fluorescently-labelled Pf1-based composite biomembranes for future applications in areas such as nanoporous filtration biofilms and photoconducting nanocomposite materials. Methods: Pf1 was characterized with respect to amine (N-terminal, Gly1 and Lys20), carboxylate (aspartate, glutamate), and aromatic (tyrosine) modification and its extension to the creation of functional biomaterials. Modification with an amine reactive fluorophore was carried out with Pf1. Results: The reaction profiles between M13 and Pf1 differ, with M13 capable of modification at two primary amines on its major coat protein, while Pf1 is capable of a single reaction per coat protein. Subsequent to the production of dye-functionalized Pf1, a biocomposite of wild type and functionalized Pf1 could be fabricated into a bulk material by glutaraldehyde (amine-reactive) crosslinking. These biomaterials were characterized by scanning electron and confocal microscopy, showing a distribution of patches of functionalized Pf1 within the main Pf1 construct. Conclusion: The current study provides a framework for future fabrication of advanced bionanomaterials based on the Pf1 bacteriophage.

Background: Multi-walled carbon nanotubes (MWCNTs) were filled with dialkyl pentasulfide (DPS) to prepare MWCNTs-DPS composite (nanocomposite) additives for use in nanofluid- based machining. Methods: The nanocomposite was prepared by employing a liquid phase wet chemistry method, and was then added in pure water with a surfactant to form the nanofluids. The present study comprehensively reveals the effects of additive concentration, acid treatment time, testing temperature and electrowetting conditions on the electrical conductivity and wettability of nanofluids. Results: The nanocomposite was successfully produced with a maximum filling rate of 27.4%. Its additives displayed an optimal performance at a concentration of about 0.1%. Consequently, the electrical conductivity and wettability of the nanofluids were increased by over 13.7% and 6.35%, respectively in comparison with individual MWCNTs additives. Under the electro-wettability conditions, the wetting performance of the nanofluids produced by the nanocomposite increased with the increase in charging voltage. Moreover, due to higher conductivity and greater charge capacity, the nanofluids with a higher additive concentration displayed better wetting performance. Conclusion: The modification and filling enhanced properties such as the surface activity, electrical conductivity and capacitance of the MWCNTs, thereby improving the performance.

Background: Metal oxide nanomaterial such as ZnO shows novel structural, optical, electrical and antibacterial properties due to its wide bandgap (3.37 eV) and high excitonic binding energy (60 meV). Probing these inherent properties of nanosized ZnO with different morphologies has generated new interest among researchers. Objective: To investigate the size-dependent functional attributes, ZnO nanorods were prepared by hydrothermal method and the photocatalytic (PC) efficiency was studied. The photoluminescence (PL) property of ZnO nanorods was also studied by recording the emission spectrum under photoexcitation. These nanorods (NRs) were coated on cotton fabric to study the effectiveness of these NRs in defending and inhibiting the growth of different bacteria. Methods: The crystallographic structure and morphology of the ZnO samples were investigated by X-ray diffraction (XRD) and field emission scanning electron microscopic (FESEM) measurements. PL measurement at room temperature was undertaken by exciting the sample with light of wavelength 350 nm. The PC property of ZnO NRs was studied in degrading organic dyes like methylene blue. Bacteria like Staphylococcus aureus, Escherichia coli and Bacillus subtilis were cultured and the inhibition of growth of these bacteria was studied by the application of ZnO. To enhance the microbe defence mechanism of fabric, we coated these NRs on fabric test samples and investigated the bacterial growth on it. Results: XRD and FESEM studies reveal the dimension of the synthesized products in the nano range. These nanorods are of high density and have surface roughness as per the FESEM study. PL measurement shows the presence of strong UV emission at 382 nm with defect emissions in the bluegreen region opening up the path for ZnO to be used in the fabrication of optoelectronic devices. PC study reveals that 89% degradation of methylene blue (MB) dye is achievable in 180 min using these ZnO catalysts. The anti-bacterial study shows that the minimum inhibitory concentration (MIC) of ZnO nanorods coated on the fabric against S. aureus is found to be 3.5 mg/ml which is the minimum as compared to E. coli (7.5 mg/ml) and B. subtilis (5.5 mg/ml). The study further enunciates that fabric coated with ZnO samples exhibited considerably high inhibition activity towards S. aureus. Conclusion: The study shows that ZnO NRs can be effectively used for the fabrication of UVLASER/ LED. The photocatalytic efficiency of ZnO will be useful for the degradation of organic dyes controlling environmental pollution. It further enunciates that fabric coated with ZnO samples exhibited considerably high inhibition activity toward S. aureus (skin bacteria) which will be helpful in defending microbes if used in surgical cotton bandages.