Nanoscience & Nanotechnology-Asia - Volume 12, Issue 3, 2022

MWCNTs are elongated cylindrical nanoobjects made of sp2 carbon. They have a diameter of 3–30 nm and can grow to be several centimetres long. Therefore, their aspect ratio can range between 10 to 10 million. Carbon nanotubes are the foundation of nanotechnology. It is an exceptionally fascinating material. CNTs possess excellent properties, such as mechanical, electrical, thermal, high adsorption, outstanding stiffness, high strength and low density with a high aspect ratio. These properties can be useful in the fabrication of revolutionary smart nanomaterials. The demand for lighter and more robust nanomaterials in different applications of nanotechnology is increasing every day. Various synthesis techniques for the fabrication of MWCNTs, such as CVD, arc discharge, flame synthesis, laser ablation, and spray pyrolysis, are discussed in this review article, as are their recent applications in a variety of significant fields. The first section presents a brief introduction of CNTs, and then the descriptions of synthesis methods and various applications of MWCNTs in the fields of energy storage and conversion, biomedical, water treatment, drug delivery, biosensors, bucky papers and resonance-based biosensors are provided in the second section. Due to their improved electrical, mechanical, and thermal properties, MWCNTs have been extensively used in the manufacturing and deployment of flexible sensors.

Water issues, including inaccessibility of a high percentage of freshwater, water pollution, water scarcity for drinking, etc., are major global concerns. Our research work aims to clean wastewater and treat it safely by applying nanotechnology. Nanotechnology has a broad range of applications. With the help of metal-based nanoparticles, advanced techniques can be developed for treating wastewater. Water purification generally employs methods that involve adsorption, breaking down waste and harmful materials, and nanoscale filtration techniques. This research review mainly discusses the synthesis of nanoparticles and the application of nanotechnology in wastewater treatment.

Background: In the nanometer regime, the impact of temperature is quite dominant in the device characteristics. Objectives: A comparative study of L-shaped Tunnel Field Effect Transistors (TFETs) and Ushaped TFETs with temperature variation. Methods: The effect of temperature has been studied for the device characteristics in terms of surface potential, electric field, and transfer characteristics using the Synopsys TCAD tool. Results: The ON current and OFF current of L-shaped and U-shaped TFETs structure shows the enhanced performance due to the large area of channel length. The addition of n-type pocket under the source enhances both devices ON current and OFF current. Both L-shaped and U-shaped TFETs structures are easy to fabricate and cost-effective due to the use of already established Si technology. Conclusion: In next-generation devices, the superior performance of L and U-shaped TFETs structure makes it a promising contender for low power applications as their subthreshold swing (SS) is less than 60 mV/decade is observed.

A simple hydrothermal method has been successfully employed to synthesize flower-like ZnO nanostructure. X-ray diffraction data confirm the formation of ZnO with a Wurtzite structure. FESEM images show the flower-like morphology of the synthesized nanostructures. The energy dispersive X-ray spectroscopic analysis confirms the stoichiometric composition.. X-ray fluorescence spectrum shows no impurity element in the synthesized ZnO. The synthesized ZnO exhibits low absorption in the visible region of wavelength. Band gap enhancement was also observed owing to the quantum confinement effect. The synthesized ZnO nanoflowers exhibit strong room-temperature photoluminescence with a broad emission peak at 429 nm arising due to the recombination of electrons at zinc interstitials and holes in the valence band. This defect-related photoluminescence is very important in the context of understanding the defect dynamics in ZnO. Background: Zinc oxide (ZnO) is a well-known multifunctional material possessing unique structural, electrical, and optical properties that are very useful in various device applications. Being a high and direct band gap semiconductor, it is potentially being used in various UV light sources and detectors fabrication. However, the emission and absorption properties strongly depend on the size of the ZnO nanoparticles which in turn depends on the morphology of the nanostructure. Therefore, it is very much important to understand the structure-property relationship for a predictable device performance. Objectives: Our objective of this work is to synthesize flower-like ZnO nanostructures using a simple hydrothermal method. The flower-like ZnO morphology offers a large surface area that will be very suitable for designing gas and chemical sensor devices. Another objective of this work is to study the crystallography of ZnO. Next, the optical properties (emission and absorption) have been investigated to understand the defect-related photoluminescence mechanism. Methods: A simple hydrothermal method has been deployed to synthesize flower-like ZnO nanostructures. A chloride decomposition scheme has been used to produce zinc hydroxide ions that will produce ZnO nuclide. At the onset of saturation, ZnO nanocrystals start to grow. The entire reaction was performed inside a Teflon cell stainless steel autoclave. The autoclave was placed in a horizontal tube furnace and maintained at 150 °C for 2 hr. resulting in the formation of white powder-like material. Results:The X-ray diffraction data confirm the formation of polycrystalline ZnO having a Wurtzite structure. Flower-like morphology was clearly observed in FESEM images. The EDS data confirm the composition of ZnO with proper stoichiometry. Gibb’s free energy calculation favors the reaction under the experimental condition. The absorption spectrum was used to calculate the band gap of the synthesized ZnO nanoflowers. The Tauc plot revealed the band gap of the synthesized ZnO to be∼ 3.69 eV. This enhancement of band gap compared to bulk ZnO occurs due to the quantum confinement effect. The synthesized ZnO nanoflowers exhibit broad photoluminescence peaked at 429 nm owing to the presence of interstitial zinc. Conclusion: A hydrothermal method has been successfully used to synthesize well-crystalline ZnO nanoflowers of proper stoichiometry. The flower-like nanostructure exhibits band gap enhancement due to the quantum confinement effect. Room temperature visible photoluminescence was observed from the ZnO nanoflowers with a board emission peak at 429 nm. This emission arises due to the presence of deep-level zinc interstitial states. This finding will be very useful in understanding the role of defects in the visible emission from ZnO nanostructures.

Over the past few years, significant advances in science and technology have occurred in the field of Perovskite-based Solar Cells (PSC), which has sparked significant interest in nextgeneration photovoltaic technologies. Perovskite solar cells, which have a current certified power conversion efficiency of 25.5 %, are the first solution processed photovoltaic to outperform silicon- based photovoltaic technologies. Perovskite solar cells are comparable to Silicon-based solar cells due to their low-cost fabrication techniques and high efficiency. Nevertheless, the research community is still concerning about future design optimization, series degradation issues, stability, and practical efficiency restrictions. As a result, comprehensive knowledge of the perovskite solar cell's operating mechanism and operating principles is more important than ever before applying these technologies in the real world for future optimization. Recent research findings in the material science of innovative halide perovskites, as well as numerous architectures based on alternative materials for lead-free perovskites, band-gap engineering, impact of materials on various Electron Transport Layers (ETL) and Hole Transport Layers (HTL), the device instability and J-V hysteresis issues of perovskite solar cells are the focus of this study. In order to better understand the potential of perovskite solar cell, factors such as hysteresis-inducing factors, interface engineering, device stability, and a variety of recombination processes are being investigated. For future optimization of perovskite solar cells, the following review findings provide a clear focus for current research needs and future research directions to address issues and understand the working potential of the perovskite solar cell.

Background: Prolonged treatment with fixed orthodontic appliances tend to compromise oral hygiene maintenance in patients, increasing their susceptibility to white spot lesions and caries. Incorporating silver nanoparticles into adhesives and orthodontic appliances is known to improve its antimicrobial properties. Aim and Objectives: The aim of the present study was to assess and compare the bond strength of orthodontic adhesive when silver nanoparticles were added in varying concentrations and also to assess their cytotoxicity on periodontal ligament fibroblasts. Materials and Methods: Various concentrations of silver nanoparticles (1%, 5%, 10%w/w) were incorporated into Transbond XT composite adhesive and their shear bond strength and cytotoxicity were compared to a control group. Brackets were bonded to extracted premolar teeth and shear bond strength was assessed using Instron Universal Testing Machine. The viability of periodontal ligament fibroblasts was assessed after incubating with the experimental composite for 24 hours and 1 week using an MTT assay. Results: There was a decrease in the shear bond strength when 1% and 5% of silver nanoparticles were incorporated into the adhesive. However, it was within the clinically recommended range for bonding brackets. When the concentration was increased to 10%, the SBS was not acceptable for orthodontic bonding. The composite incorporated with silver nanoparticles was cytotoxic to fibroblasts at all concentrations at both time intervals. Conclusion: The shear bond of orthodontic adhesive with nanosilver is comparable to plain Transbond XT in low concentrations, however, the addition of silver nanoparticles seems to increase the time-bound cytotoxicity of orthodontic adhesive.

Background and Objective: In the past several decades, the gastro-retentive drug delivery system is considered a novel approach which has gained immense popularity in the field of novel drug delivery systems. Among several approaches to achieving gastric retention raft-forming system which comes under the classification of floating drug delivery system is a subject of special research interest. This advanced drug delivery system has the potential to attain a prolonged and predictable drug delivery at specific sites of the GI tract mainly in the stomach and intestine thereby exhibiting a relatively constant plasma profile. Thus, the floating raft-forming system finds usefulness over conventional therapeutics to treat several gastrointestinal disorders viz., gastroesophageal reflux disorder, acid reflux, peptic ulcer, esophagitis, etc. Methods: In this current manuscript, an extensive search is performed for original research papers using databases viz., Google Scholar, PubMed, Science Direct, etc. Further, painstaking efforts are made to compile and update the recent findings of the formulation scientists working exclusively in the area of raft-forming systems. This article portrays a detailed survey about several applications of raft-forming systems in the form of tables. Conclusion: The floating raft-forming system has the potential for controlled drug release in the upper part of the GI tract and exerts improved bioavailability of the medications having a narrow absorption window. Thus, it is concluded that this advanced dosage form is the caliber candidate for the treatment of several gastrointestinal ailments.