Cerium Oxide Nanoparticles: Synthesis and Characterization for Biosafe Applications

Due to its excellent physicochemical properties, cerium oxide (CeO2) has attracted much attention in recent years. CeO2 nanomaterials (nanoceria) are widely being used, which has resulted in them getting released to the environment, and exposure to humans (mostly via inhalation) is a major concern. In the present study, CeO2 nanoparticles were synthesized by hydroxide-mediated method and were further characterized by Scanning Electron Microscopy (SEM), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction Spectroscopy (XRD). Human lung epithelial (Beas-2B) cells were used to assess the cytotoxicity and biocompatibility activity of CeO2 nanoparticles. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) and Live/Dead assays were performed to determine the cytotoxicity and biocompatibility of CeO2 nanoparticles. Generation of reactive oxygen species (ROS) by cerium oxide nanoparticles was assessed by ROS assay. MTT assay and Live/Dead assays showed no significant induction of cell death even at higher concentrations (100 μg per 100 μL) upon exposure to Beas-2B cells. ROS assay revealed that CeO2 nanoparticles did not induce ROS that contribute to the oxidative stress and inflammation leading to various disease conditions. Thus, CeO2 nanoparticles could be used in various applications including biosensors, cancer therapy, catalytic converters, sunscreen, and drug delivery.

Equations for the Electron Density of the Two-Dimensional Electron Gas in Realistic AlGaN/GaN Heterostructures

This paper presents equations for the electron density of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures in three realistic scenarios: (1) AlGaN/GaN heterostructure with surface exposed to ambient with mobile ions, (2) metal gate deposited on the AlGaN surface, and (3) a thick dielectric passivation layer on the AlGaN surface. To derive the equations, we analyzed these scenarios by applying Gauss’s law. In contrast to the idealistic models, our analysis shows that the 2DEG charge density is proportional to the difference between spontaneous polarization of AlGaN and GaN, whereas surprisingly, it is independent of the piezoelectric polarization.

Influence of the Physico-Chemical Properties of Model Compounds on the Mean Sizes and Retention Rate of Gliadin Nanoparticles

Vegetal proteins have emerged as appealing starting materials for the development of various drug delivery systems, and their use for obtaining polymeric nanoparticles has been profitably exploited in multidisciplinary fields. Wheat gliadin, the water-insoluble storage protein of gluten, is characterized by a great amount of hydrophobic amino acid residues and notable mucoadhesive features. This biopolymer can be easily manipulated to form colloidal carriers, films and fibers by means of bio-acceptable solvents and easy preparation procedures. In this investigation, four model compounds characterized by different octanol/water partition coefficient (logP) values were encapsulated in gliadin nanoparticles, with the aim of investigating the influence of their physico-chemical properties on the cargo features and technological characteristics of the protein nanocarriers. The results demonstrate that the chemical structure, solubility and molecular weight of the compounds used are able to dramatically modulate the mean sizes and the entrapment efficiency of gliadin nanoparticles. This demonstrates the importance of a preformulation investigation when a molecule needs to be encapsulated in this type of polymeric carrier.

Synthetic Approach to Rice Waste-Derived Carbon-Based Nanomaterials and Their Applications

The utilization of biomass waste to produce valuable products has extraordinary advantages as far as both the economy and climate are concerned, which have become particularly significant lately. The large-scale manufacturing of agricultural waste, mainly rice by-products (rice husk, rice straw, and rice bran), empowers them to be the most broadly examined biomasses as they contain lignin, cellulose, and hemicellulose. Rice waste was first used to incorporate bulk materials, while the manufacturing of versatile nanostructures from rice waste at low cost has been developed in recent years and attracts much consideration nowadays. Carbon-based nanomaterials including graphene, carbon nanotubes, carbon dots, fullerenes, and carbon nanofibers have tremendous potential in climate and energy-related applications. Various methods have been reported to synthesize high-value carbon nanomaterials, but the use of green technology for the synthesis of carbon nanomaterials is most common nowadays because of the abundant availability of the starting precursor, non-toxicity, low fabrication cost, ease of modification, and eco-friendly nature; therefore, reusing low-value biomass waste for the processing of renewable materials to fabricate high-value products is remarkable. Carbon nanomaterials derived from rice waste have broad applications in various disciplines owing to their distinctive physicochemical, electrical, optical, mechanical, thermal, and enhanced biocompatibility properties. The main objective of this review and basic criteria of selecting examples and explanations is to highlight the green routes for the synthesis of carbon nanomaterials—i.e., graphene, carbon nanotubes, and carbon dots—from rice biomass waste, and their extensive applications in biomedical research (bio-imaging), environmental (water remediation), and energy-related (electrodes for supercapacitors, Li-ion battery, fuel cells, and solar cells) applications. This review summarizes recent advancements, challenges, and trends for rice waste obtained from renewable resources for utilization in the fabrication of versatile carbon-based nanomaterials.

The Influence of Alkanethiols on the Production of Hydrophobic Gold Nanoparticles via Pulsed Laser Ablation in Liquids

The ability to suspend plasmonic metal nanoparticles in apolar environments is an important feat towards harnessing their optical properties for use in amphiphilic biological environments. Pulsed laser Ablation in Liquids (PLAL) is a well-established method for the production of gold nanoparticles (AuNPs) in aqueous environments; however, ablation in organic liquids for the synthesis of hydrophobic AuNPs still has many unknowns, such as the relationship between colloidal stability and the ligand shell. In this study, hydrophobic AuNPs were produced by PLAL of gold in a 1-alkanethiol/n-decane solution and treated with laser fragmentation. Results demonstrate that longer chain length ATs produced particles with a smaller average size; however, there was no strong correlation between alkanethiol (AT) concentration and particle size. Stability was investigated by monitoring the temporal evolution of the extinction spectra which revealed that lower concentrations of AT stabilize the colloids while higher concentrations tend to result in quicker particle aggregation. Furthermore, longer chain length ATs demonstrated improved stability. Additionally, vibrational spectroscopy was employed to examine the AuNP surface chemistry, which pointed to the presence of oxidized carbon species and graphitic carbon.

Advances with Molecular Nanomaterials in Industrial Manufacturing Applications

Molecular nanomaterials are of prodigious reputation for their uses in the numerous industries. This article highlights established industrial potential application areas for nanoparticles. The success of nanomanufacturing depends on the strong cooperation between academia and industry in order to be informed about current needs and future challenges, to design products directly translated to the industrial sector. The selection of the appropriate method, combining synthesis of nanomaterials with required properties and limited impurities as well as scalability of the technique, is of paramount importance. Varieties of molecular nanomaterials and their synthesis, characterization, and important applications are of current interest in several industries. Improved synthetic routes and advanced characterization methods will be important to advance molecular nanomaterials for their rapid translation to industries, manufacturing many useful products, and their implication in global economic development. Nanomaterials have emerging applications in almost all modern industries including construction, textile, water, aeronautics, food, medicine, environment cosmetics, machinery, oil and gas and computer. In the current review, we have chosen some leading industries world-wide that use nanomaterials. Besides the important applications of nanomaterials in almost all spheres of human life and environment, their toxicological effects must be addressed properly to utilize these applications. There are also some obstacles to a greater impact of nanotechnology in industry including its toxicological effects in human and surrounding environments and regulations of nanomaterials use. This review addresses molecular nanomaterials synthesis strategies, characterization methods developments, and their novel industrial and other relevant application fields.

Solvent-Mediated Structural Evolution Mechanism from Cs4PbBr6 to CsPbBr3 Crystals

The study of the solvent-mediated structural evolution mechanism of the Cs4PbBr6 powders prepared using the solvothermal method is presented. The Cs4PbBr6 powders with a rhombohedral structure and an intense green emission (i.e., mainly due to the presence of complex defect states in the forbidden gap), which is stable in its solid-state form, but a distinct behavior is observed in different dispersions, easily detectable when irradiated with ultraviolet (UV) light. Depending on the polarity of the solvent, a change in the emission color from green to red is observed, easily detectable when irradiated with ultraviolet (UV) light. Our findings suggest that the solvent polarity affects the surface decomposition process, leading to a different change in composition, structure and crystal shape. This peculiar behavior plays a pivotal role in the control of the properties of Cs4PbBr6, and this study, therefore, offers a fundamental understanding needed for Cs4PbBr6 potential future applications.

Effectiveness of Different Cellulose-Based Filtration Materials against Inhalation of SARS-CoV-2-Like Particles

The respiratory protection equipment (RPE) used by health professionals consists of an essential device to prevent infectious diseases, especially those caused by biological agents such as the coronavirus (SARS-CoV-2). The current epidemiological panorama is worrying, and the context of creation and production of the mask has emerged as an alternative to RPE to face the public health crisis worldwide. The aim of this work is to present a low-cost alternative as an FFP2-like filter for a reusable respirator face mask. This study presents the comparison of different cellulose-based filtering materials performed by retention testing, time saturation testing, aerosol penetration testing, nanoparticle (~140 nm) filtration testing, bacterial filtration efficiency (BFE), analysis of material morphology and usability. The reusable respirator face mask used in this study is an open-source innovation, using 3D printing. Cotton disc proved to be the best filter material for the reusable mask, with satisfactory results and a performance similar to that shown by the N95-type mask. The cotton disc ensured effectiveness over 6 h of use, and after that, the reusable respirator face mask (here, Delfi-TRON®) needed to be sanitized and replenished with a new cotton disc. Upon preliminary analyses of filtration efficiency, the selected filter was shown to be a low-cost biodegradable and biocompatible alternative.

Heated Assembly and Transfer of Van der Waals Heterostructures with Common Nail Polish

Recent advances in the manipulation and control of layered, two-dimensional materials has given way to the construction of heterostructures with new functionality and unprecedented electronic properties. In this study, we present a simple technique to assemble and transfer van der Waals heterostructures using common nail polish. Commercially available nail polish acts as a resilient sticky polymer, allowing for the fabrication of complex multi-material stacks without noticeable fatigue. Directly comparing four commercially available brands of nail polish, we find that one stands out in terms of stability and stacking characteristics. Using this method, we fabricate two top-gated devices and report their electrical properties. Our technique reduces the complexity in assembling van der Waals heterostructures based on the proven van der Waals pick up method.

Two-Dimensional Nanograting Fabrication by Multistep Nanoimprint Lithography and Ion Beam Etching

The application of nanopatterned electrode materials is a promising method to improve the performance of thin-film optoelectronic devices such as organic light-emitting diodes (OLEDs) and organic photovoltaics. Light coupling to active layers is enhanced by employing nanopatterns specifically tailored to the device structure. A range of different nanopatterns is typically evaluated during the development process. Fabrication of each of these nanopatterns using electron-beam lithography is time- and cost-intensive, particularly for larger-scale devices, due to the serial nature of electron beam writing. Here, we present a method to generate nanopatterns of varying depth with different nanostructure designs from a single one-dimensional grating template structure with fixed grating depth. We employ multiple subsequent steps of UV nanoimprint lithography, curing, and ion beam etching to fabricate greyscale two-dimensional nanopatterns. In this work, we present variable greyscale nanopatterning of the widely used electrode material indium tin oxide. We demonstrate the fabrication of periodic pillar-like nanostructures with different period lengths and heights in the two grating directions. The patterned films can be used either for immediate device fabrication or pattern reproduction by conventional nanoimprint lithography. Pattern reproduction is particularly interesting for the large-scale, cost-efficient fabrication of flexible optoelectronic devices.