Strong oxygen-content dependence of the magnetic excitations in antiferromagnetic NiO nanoparticles: A Raman probe

Nanostructured antiferromagnetic (AFM) NiO has attracted much attention from both the fundamental and applied perspectives. Understanding the two-magnon (2 M) is of great significance in NiO applications such as spin valves and next-generation magnetic random access memories (MRAM). We investigated the phonon modes and antiferromagnetically ordered states of NiO nanoparticles prepared by empirically controlled measurements. An intensity enhancement of the 2 M mode was observed by Raman spectroscopy as the NiO nanoparticles were vacuum annealed at 650 ℃. The increased 2 M peak intensity in NiO nanoparticles is explained by the local symmetry conversions from NiO₅ to NiO₆ configurations due to the oxygen redistribution during the vacuum annealing. The change of the splitting of anisotropic transverse optical (TO) phonon with different oxygen contents was also revealed by the Raman spectroscopy. We have shown that the changes in the oxygen environment underlie both the change in the 2 M intensity and the splitting of TO phonon in the NiO nanoparticles. Our work offers an efficient avenue to strengthen the AFM ordering and emphasizes the effect of vacuum annealing of the NiO nanoparticles, opening the interesting possibility of individual parameter control in practical applications.

Transparent Electronics for Wearable Electronics Application

Recent advancements in wearable electronics offer seamless integration with the human body for extracting various biophysical and biochemical information for real-time health monitoring, clinical diagnostics, and augmented reality. Enormous efforts have been dedicated to imparting stretchability/flexibility and softness to electronic devices through materials science and structural modifications that enable stable and comfortable integration of these devices with the curvilinear and soft human body. However, the optical properties of these devices are still in the early stages of consideration. By incorporating transparency, visual information from interfacing biological systems can be preserved and utilized for comprehensive clinical diagnosis with image analysis techniques. Additionally, transparency provides optical imperceptibility, alleviating reluctance to wear the device on exposed skin. This review discusses the recent advancement of transparent wearable electronics in a comprehensive way that includes materials, processing, devices, and applications. Materials for transparent wearable electronics are discussed regarding their characteristics, synthesis, and engineering strategies for property enhancements. We also examine bridging techniques for stable integration with the soft human body. Building blocks for wearable electronic systems, including sensors, energy devices, actuators, and displays, are discussed with their mechanisms and performances. Lastly, we summarize the potential applications and conclude with the remaining challenges and prospects.

The Schiff base hydrazine copper(II) complexes induce apoptosis by P53 overexpression and prevent cell migration through protease-independent pathways

Although chemotherapy has increased the life expectancy of cancer patients, its toxic side effects remain a major challenge. Recently, organometallic compounds, such as Schiff base copper complexes, have become promising candidates for next-generation anticancer drugs owing to their unique anticancer activities. In this study, binuclear copper(II) complex-1 and mononuclear copper(II) complex-2 were examined to analyze their anticancer mechanisms further. For this purpose, a viability test, flow cytometry analysis of apoptosis and the cell cycle, migration assay, and gene expression analysis were performed. According to our results, complex-1 was more cytotoxic than complex-2 at 24/48-h intervals. Our findings also demonstrated that both complexes induced apoptosis at IC50 concentrations and arrested the cell cycle at the G1-S checkpoint. However, complex-1 accelerates cell cycle arrest at the sub-G0/G1 phase more than complex-2 does. Furthermore, gene expression analysis showed that only complex-1 induces the expression of p53. Interestingly, both complexes induced Bcl-2 overexpression. However, they did not affect MMP-13 expression. More interestingly, both complexes inhibited cell migration in different ways, including amoeboid and collective, by recruiting protease-independent pathways. This study confirmed that adding several metal cores and co-ligands increased the activity of the complex. It also appeared that Cu-containing complexes could prevent the migration of cancer cells through protease-independent pathways, which can be used for novel therapeutic purposes.

Two-dimensional correlation spectroscopy analysis of Raman spectra of NiO nanoparticles

We report two-dimensional correlation spectroscopy (2D-COS) analyses of the Raman spectra of NiO nanoparticles over a temperature range from 100 to 300 K. 2D-Raman correlation spectra suggest strong correlation of the phonon spectral intensity variation with the magnetic ordering in NiO nanoparticles. It is revealed that the antiferromagnetic ordering affects the TO phonon anisotropy in NiO nanoparticles. We elucidate the complex spectral features of two-magnon (2 M) bands by performing appropriate 2D-COS model simulations. Significant spin-phonon coupling in NiO nanoparticles is supported by our results. High energy magnon-magnon interaction tails are also found to be involved in the spin-phonon coupling. 2D-COS analyses provide rich information regarding the nature of the phonon and magnon excitations of NiO nanoparticles.

Tuning the band gap of M-doped titanate nanotubes (M = Fe, Co, Ni, and Cu): an experimental and theoretical study

Herein, we report a systematic experimental and theoretical study about a wide-ranged band gap tuning of protonated titanate nanotubes H₂Ti₃O₇ (Ti-NT) by an easy ion-exchange method using a low concentration (1 wt%) of transition metal cations. To characterize and describe the effect of M doping (M = Cu²⁺, Ni²⁺, Co²⁺, and Fe³⁺) on the electronic, optical and structural properties, semiconductors were analyzed by a combination of experimental methods and density functional theory (DFT) calculations. The nanotube band gap can be modified from 1.5 to 3.3 eV, which opens the possibility to use them in several optoelectronic applications such as photocatalysts under solar light irradiation.

Rapid Green Synthesis of Biogenic Silver Nanoparticles Using Cinnamomum tamala Leaf Extract and its Potential Antimicrobial Application Against Clinically Isolated Multidrug-Resistant Bacterial Strains

Cinnamomum tamala is Indian bay leaves also known as Tej patta commonly used in the preparation of delicious food for its sweet aroma and tremendous medicinal values. In this study, the significant concentration-dependent free radical scavenging and antioxidant efficacy of the aqueous extracts of bay leaves has been determined using DPPH (2, 2-diphenyl-l-picrylhydrazyl) radical scavenging, ferric ion-reducing power assay, and hydrogen peroxide radical scavenging assay. The leaf extract has also been utilized in the rapid synthesis of silver nanoparticles (AgNPs) under mild conditions (30 min reaction time at 70 °C) without the addition of extra stabilizing or capping agents. Mostly spherical shaped particles were formed with diameter ranging from 10 to 12 nm as evident by HRTEM imaging. The silver nanoparticles were also characterized using FTIR, XRD, and UV-visible spectroscopic techniques. The antibacterial effect of the synthesized AgNPs was studied against three clinically isolated multidrug-resistant bacterial strains (Escherichia coli (EC-1), Klebsiella pneumonia (KP-1), and Staphylococcus aureus (SA-1)). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNPs against EC-1 were 12.5 and 15 μg/mL and in SA-1 were 10 and 50 μg/mL, and in the case of KP-1, both values were 12.5 μg/mL. It was also noted that 8 h treatment duration using AgNPs was sufficient to eliminate all types of bacterial growth as evidenced by time-dependent killing kinetic assays. The biocompatibilities of AgNPs were also tested against human health RBCs, and it was observed that it did not show any significant toxicity up to 50 μg/mL concentration.

Poly(3-hydroxybutyrate)/poly(amine)-coated nickel oxide nanoparticles for norfloxacin delivery: antibacterial and cytotoxicity efficiency

Sustained release dosage forms enable prolonged and continuous release of a drug in the gastrointestinal tract for medication characterized by a short half lifetime. In this study, the effect of blending polyamine on poly(3-hydroxybutyrate) (PHB) as a carrier for norfloxacin (NF) was studied. The prepared blend was mixed with different amounts of NiO nanoparticles and characterized using FTIR analysis, X-ray diffraction analysis, thermogravimetric analysis, dynamic light scattering, transmission electron microscopy and scanning electron microscopy. It was found that the drug released from the nanocomposite has a slow rate in comparison with NiO, PHB, and PHB/polyamine blend. The highest ratio of NiO content to the matrix (highest NF loading), leads to a slower rate of drug release. The release from the nanocomposites showed a faster rate at pH = 2 than that at pH = 7.4. The mechanisms of NF adsorption and release were studied on PHB/polyamine-3% NiO nanocomposite. In addition, the antimicrobial efficacy of nanocomposites loaded with the drug was determined and compared with the free drug. Inclusion of NiO into PHB/polyamine showed a higher efficacy against Streptococcus pyogenes and Pseudomonas aeruginosa than the free NF. Moreover, the cytotoxicity of PHB/polyamine-3% NiO against HePG-2 cells was investigated and compared with PHB and PHB/polyamine loaded with the drug. The most efficient IC50 was found for NF@PHB/polyamine-3% NiO (29.67 μg mL-1). No effect on cell proliferation against the normal human cell line (WISH) was observed and IC50 was detected to be 44.95 and 70 μg mL-1 for NiO nanoparticles and the PHB/polyamine-3% NiO nanocomposite, respectively indicating a selectivity of action towards tumor cells coupled with a lack of cytotoxicity towards normal cells.

Metal-Free Oxide-Nitride Heterostructure as a Tunable Hyperbolic Metamaterial Platform

Metal-free plasmonic metamaterials with wide-range tunable optical properties are highly desired for various components in future integrated optical devices. Designing a ceramic-ceramic hybrid metamaterial has been theoretically proposed as a solution to this critical optical material demand. However, the processing of such all-ceramic metamaterials is challenging due to difficulties in integrating two very dissimilar ceramic phases as one hybrid system. In this work, an oxide-nitride hybrid metamaterial combining two highly dissimilar ceramic phases, i.e., semiconducting weak ferromagnetic NiO nanorods and conductive plasmonic TiN matrix, has been successfully integrated as a unique vertically aligned nanocomposite form. Highly anisotropic optical properties such as hyperbolic dispersions and strong magneto-optical coupling have been demonstrated under room temperature. The novel functionalities presented show the strong potentials of this new ceramic-ceramic hybrid thin film platform and its future applications in next-generation nanophotonics and magneto-optical integrated devices without the lossy metallic components.

Dental Adhesive Interfaces Reinforced with Magnetic Nanoparticles: Evaluation and Modeling with Micro-CT versus Optical Microscopy

Dental adhesives are used in a wide range of applications, including to place direct composite restorations in frontal or posterior teeth. One of the most frequent causes for the failure of composite resin restorations is microleakages. The first aim of this work is to introduce a new type of self-etched dental adhesive doped with magnetic nanoparticles (MPs) synthetized in the laboratory. The scope is to produce adhesives with a minimized width/thickness to decrease the risk of microleakages. The second aim is to assess the width/thickness of the adhesive layer in all the characteristic areas of the teeth using both the less precise but most common optical microscopy and the more accurate and volumetric micro-Computed Tomography (CT) investigations. Twenty extracted teeth have been divided into four groups: Group 1 includes 'blank' samples with adhesives that are not doped with MPs; Group 2 includes samples with adhesives doped with MPs; Groups 3 and 4 include samples with adhesives doped with MPs that are subjected to an active magnetic field for 5 and 10 min, respectively. Microscopy investigations followed by micro-CT and EDAX are performed on the adhesive. While a rather good agreement is obtained between the microscopy and micro-CT results, the capability of the latter to offer a full volumetric reconstruction of the layer is exploited to analyze the adhesion of the four considered dental materials. Thus, from micro-CT results the graphs of the surface areas as functions of the adhesive layer width are modeled mathematically, as well as the volume of sealants, for each of the four groups. To our knowledge, it is the first time that such a methodology is used. Characteristic parameters are extracted and the ascertainment of the optimal parameter that should be utilized for such assessments is discussed. The study demonstrates the adhesion improvement produced for Groups 3 and 4, where MPs are used. It also concludes that the magnetic field should be applied to the adhesive material for the longest possible exposure time (with a trade-off with the clinical duration of the treatment).

Magnetic Nanoparticles for Biomedical Purposes: Modern Trends and Prospects

The presented paper is a review article discussing existing synthesis methods and different applications of nanosized magnetic nanoparticles. It was shown that, in addition to the spectrum of properties typical for nanomaterials (primarily a large specific surface area and a high fraction of surface atoms), magnetic nanoparticles also possess superparamagnetic properties that contribute to their formation of an important class of biomedical functional nanomaterials. This primarily concerns iron oxides magnetite and maghemite, for which in vitro and in vivo studies have shown low toxicity and high biocompatibility in comparison with other magnetic nanomaterials. Due to their exceptional chemical, biological, and physical properties, they are widely used in various areas, such as magnetic hyperthermia, targeted drug delivery, tissue engineering, magnetic separation of biological objects (cells, bacteria, viruses, DNA, and proteins), and magnetic diagnostics (they are used as agents for MRS and immunoassay). In addition to discussing the main problems and prospects of using nanoparticles of magnetic iron oxides for advanced biomedical applications, information is also reflected on their structure, production methods, and properties.

Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

In this work, the effect of carbon dots (C-dots) on the performance of NiO-based dye-sensitized solar cells (DSSCs) was explored. NiO nanoparticles (NPs) with a rectangular shape (average size: 11.4 × 16.5 nm²) were mixed with C-dots, which were synthesized from citric acid (CA) and ethylenediamine (EDA). A photocathode consisting of a composite of C-dots with NiO NPs (NiO@C-dots) was then used to measure the photovoltaic performance of a DSSC. A power conversion efficiency (PCE) of 9.85% (430 nm LED@50 mW/cm²) was achieved by a DSSC fabricated via the adsorption of N719 sensitizer with a C-dot content of 12.5 wt % at a 1.5:1 EDA/CA molar ratio. This PCE value was far larger than the PCE value (2.44 or 0.152%) obtained for a NiO DSSC prepared without the addition of C-dots or N719, respectively, indicating the synergetic effect by the co-adsorption of C-dots and N719. This synergetically higher PCE of the NiO@C-dot-based DSSC was due to the larger amount of sensitizer adsorbed onto the composites with a larger specific surface area and the faster charge transfer in the NiO@C-dot working electrode. In addition, the C-dots bound to the NiO NPs shorten the band gap of the NiO NPs due to energy transfer and give rise to faster charge separation in the electrode. The most important fact is that C-dots are the main sensitizer, while N719 tightly adsorbs on C-dots and NiO behaves as an accelerator of a positive electron transfer and a restrainer of the electron-hole recombination. These results reveal that C-dots are a remarkable enhancer for NiO NPs in DSSCs and that NiO@C-dots are promising photovoltaic electrode materials for DSSCs.

Surface modification minimizes the toxicity of silver nanoparticles: an in vitro and in vivo study

Currently toxicological research in Silver nanoparticle is a leading issue in medical science. The surface chemistry and physical dimensions of silver nanoparticles (Ag-NPs) play an important role in toxicity. The aim of this present study was to evaluate the in vitro and in vivo toxicity of Ag-NPs as well as the alteration of toxicity profile due to surface functionalization (PEG and BSA) and the intracellular signaling pathways involved in nanoparticles mediated oxidative stress and apoptosis in vitro and in vivo system. Ag-NPs released excess Ag⁺ ions leads to activation of NADPH oxidase and helps in generating the reactive oxygen species (ROS). Silver nanoparticles elicit the production of excess amount of ROS results activation of TNF-α. Ag-NPs activates caspase-3 and 9 which are the signature of mitochondrial pathway. Ag-NPs are responsible to decrease the antioxidant enzymes and imbalance the oxidative status into the cells but functionalization with BSA and PEG helps to protect the adverse effect of Ag-NPs on the cells. This study suggested that Ag-NPs are toxic to normal cells which directly lead with human health. Surface functionalization may open the gateway for further use of Ag-NPs in different area such as antimicrobial and anticancer therapy, industrial use or in biomedical sciences.

Bio-fabricated silver nanoparticles preferentially targets Gram positive depending on cell surface charge

Recently bio-inspired experimental processes for synthesis of nanoparticles are receiving significant attention in nanobiotechnology. Silver nanoparticles (Ag NPs) have been used very frequently in recent times to the wounds, burns and bacterial infections caused by drug-resistant microorganisms. Though, the antibacterial effects of Ag NPs on some multi drug-resistant bacteria specially against Gram positive bacteria has been established, but further investigation is needed to elicit its effectiveness against Gram negatives and to identify the probable mechanism of action. Thus, the present study was conducted to synthesize Ag NPs using Andrographis paniculata leaf extract and to investigate its antibacterial efficacy. After synthesis process the biosynthesized nanoparticles were purified and characterized with the help of various physical measurement techniques which raveled their purity, stability and small size range. The antimicrobial activity of Ag NPs was determined against both Gram-positive Enterococcus faecalis and Gram-negative Proteus vulgaris. Results showed comparatively higher antibacterial efficacy of Ag NPs against Gram positive Enterococcus faecalis strains. It was found that greater difference in zeta potential values between Gram positive bacteria and Ag NPs triggers better internalization of the particles. Thus the cell surface charge played vital role in cell killing which was confirmed by surface zeta potential study. Finally it may be concluded that green synthesized Ag NPs using Andrographis paniculata leaf extract can be very useful against both multi drug resistant Gram-positive and Gram-negative bacteria.

S, G. R, D. S, P. R, J. W, Rajendran S, Alwarappan S. Cerium doped nickel-oxide nanostructures for riboflavin biosensing and antibacterial applications

Electrochemical detection of riboflavin and antibacterial activities of Ce doped NiO nanostructures synthesized by the mild temperature wet chemistry approach.

Defect induced ferromagnetic interaction in nanostructured nickel oxide with core–shell magnetic structure: the role of Ni2+ and O2− vacancies

O²⁻ vacancies act as donor impurities and mediate ferromagnetic interaction between spins associated with uncompensated and partially compensated Ni²⁺ vacancies.