Polycrystalline Nanoparticles Research Articles

Operando Characterization of CO2 Reduction Interfaces by Electrochemical Atomic Force Microscopy

The electrode-electrolyte interface is perhaps the most important interface of an electrochemical device. At this interface, the electrochemical reactions of interest occur, and the local microenvironment (e.g. pH, reactant concentrations, water activity) can differ significantly from bulk electrolyte conditions due to double layer formation, migration, mass transport effects, catalyst restructuring, and more. In addition, common electrode materials such as polycrystalline metal foils and nanoparticle catalyst layers are heterogeneous with regions of differing activity, making the interface vary across the surface of the electrode both spatially and temporally. Understanding the electrode-electrolyte interface, its local microenvironment, and the evolution of the heterogeneous electrode surface is crucial to the development of high performing electrochemical devices. However, traditional electrochemical methods average current and potential measurements across the electrode surface. Thus, combining electrochemistry with advanced in situ and operando is necessary for a holistic view of the electrode-electrolyte interface.Scanning probe techniques are well-suited for operando studies of electrode-electrolyte interfaces due to their compatibility with liquid environments and suitable spatial (µm to nm scale) and temporal (minutes to seconds) resolutions. One popular operando technique for the study of electrode-electrolyte interfaces is electrochemical atomic force microscopy (EC-AFM). EC-AFM measures the interaction forces between a sharp physical probe and sample surface to map the surface topography. These measurements can also extract information about the sample’s mechanical properties by generating force-distance curves across the surface. EC-AFM measurements are readily performed in a three-electrode cell under potential bias, thereby allowing spatially and temporally resolved imaging of the electrode-electrolyte interface in operando.Here, we applied EC-AFM to two studies of the electrode-electrolyte interface during the electrochemical CO2 reduction reaction (CO2RR). First, we present EC-AFM measurements of a common degradation mode for CO2RR electrolyzers: salt precipitation. CO2RR produces OH-, which accumulates at the electrode-electrode interface and causes the local pH to shift more alkaline. However, this alkaline environment also promotes the formation and precipitation of (bi)carbonate salts by the reaction of OH- and CO2. Herein, we conducted EC-AFM measurements on a Ag electrode in calcium-containing bicarbonate electrolytes. CO2RR was catalyzed at the Ag surface to cause a local pH shift at the electrode surface and result in the formation of CaCO3 crystallites on the electrode surface. Through EC-AFM measurements, we investigated the effect of applied current and bulk electrolyte pH on this deleterious mineralization process.Second, we studied the interactions between polyethylenimine (PEI) and a Ag catalyst. PEI is a polymer that can capture CO2 from the atmosphere by forming a carbamate. Recent work has shown that CO2 bound in PEI can be directly converted to CO without an intermediate CO2 release step. However, very little information is known about the interaction of the polymer with the electrode surface during CO2RR. We studied the morphology and mechanical properties of a Ag electrode surface in PEI-containing electrolytes as a function of applied potential and electrolyte composition for the conversion of CO2 to CO. Both variables significantly affected the mechanical properties (i.e. modulus) of the electrode surface, suggesting polymer chain reorganization at the interface due to interactions with electrolyte species and charged electrode surfaces. Overall, these examples demonstrate that EC-AFM is a powerful operando technique for building fundamental understanding of the electrode-electrolyte interface.

Investigating antibacterial activity of biosynthesized silver oxide nanoparticles using Phragmanthera Macrosolen L. leaf extract

The crude leaf extract of Phragmanthera macrosolen L. has been utilized for the first time as an effective reducing, capping and stabilizing agent to synthesize silver oxide nanoparticles (Ag2O NPs) through a green approach. The prepared Ag2O NPs were analyzed by scanning electron-microscopy (SEM), High Resolution Transmission electron microscope (HR-TEM), X-ray diffractions (XRD), Fourier transforms infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), and Ultra-violet visible spectrometry (UV-Vis). The biosynthesized Ag2O NPs applied on gram-positive (S. aureus) and gram-negative (E. coli) bacterial types. FTIR spectral peaks indicate that the phytochemicals in the extract are responsible for the formation of Ag2O nanoparticles. The XRD result shown, poly-crystalline nanoparticles and the average crystalline size calculated was 45.8 nm. UV-Vis analysis shows absorbance existed at 590.5 nm, and the energy band gap calculated through the Tauc relation was 2.1 eV. The SEM images gave a globular and some rod like morphology with diameter of particle obtained between 20.11 and 46.50 nm with some hollow cubic microstructure of Ag2O NPs which makes it suitable for antimicrobial application. The EDS confirms the elemental composition and existence of Ag and O2. The HR-TEM images, specific area electron diffraction (SAED), and XRD patterns confirmed the morphology of Ag2O NPs mean 45.84 nm and polycrystalline nature of the nanoparticles. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 15 and 30 µl respectively for the samples tested. In this study, it was observed that Ag2O NPs highly sensitive to E. coli than s. aureus. The present study revealed that the possible use of green synthesized Ag2O NPs as potential antibacterial agent.

Unsupervised Learning for the Automatic Counting of Grains in Nanocrystals and Image Segmentation at the Atomic Resolution.

Identifying the grain distribution and grain boundaries of nanoparticles is important for predicting their properties. Experimental methods for identifying the crystallographic distribution, such as precession electron diffraction, are limited by their probe size. In this study, we developed an unsupervised learning method by applying a Gabor filter to HAADF-STEM images at the atomic level for image segmentation and automatic counting of grains in polycrystalline nanoparticles. The methodology comprises a Gabor filter for feature extraction, non-negative matrix factorization for dimension reduction, and K-means clustering. We set the threshold distance and angle between the clusters required for the number of clusters to converge so as to automatically determine the optimal number of grains. This approach can shed new light on the nature of polycrystalline nanoparticles and their structure-property relationships.

Fabrication and characterization of NiO nanoparticles deposited via reactive DC magnetron sputtering technique

Nickel oxide (NiO) nanostructure was successfully prepared via reactive DC magnetron sputtering on the soda-lima glass substrate, which can be used for various applications. Xray diffraction (XRD) investigations were used to evaluate NiO with two annealing durations. The results revealed that the deposited films had a cubic structure and polycrystalline nanoparticles. A significant polycrystalline structure could be seen in the sputtered films as a diffraction peak oriented toward NiO (200). Field-emission Scanning Electron Microscopy (FE-SEM) analysis identified the surface morphology of NiO nanoparticles prepared at two different annealing times with the two average sizes (24 and 32 nm) respectively. The samples' roughness was assessed using atomic force microscopy (AFM). Increased annealing time was shown to result in a decrease in grain size. The energy band gap (Eg) expanded with increasing annealing time, according to UV-visible spectroscopy (UV-Vis). FTIR spectroscopy was used to determine the functional groups of NiO nanoparticles and their bonding nature. The results indicate that optical characterizations are more sensitive to the annealing period.

Fabrication and characterization of NiO nanoparticles deposited via reactive DC magnetron sputtering technique

Nickel oxide (NiO) nanostructure was successfully prepared via reactive DC magnetron sputtering on the soda-lima glass substrate, which can be used for various applications. Xray diffraction (XRD) investigations were used to evaluate NiO with two annealing durations. The results revealed that the deposited films had a cubic structure and polycrystalline nanoparticles. A significant polycrystalline structure could be seen in the sputtered films as a diffraction peak oriented toward NiO (200). Field-emission Scanning Electron Microscopy (FE-SEM) analysis identified the surface morphology of NiO nanoparticles prepared at two different annealing times with the two average sizes (24 and 32 nm) respectively. The samples' roughness was assessed using atomic force microscopy (AFM). Increased annealing time was shown to result in a decrease in grain size. The energy band gap (Eg) expanded with increasing annealing time, according to UV-visible spectroscopy (UV-Vis). FTIR spectroscopy was used to determine the functional groups of NiO nanoparticles and their bonding nature. The results indicate that optical characterizations are more sensitive to the annealing period.

Atomic Layer Deposition of Cu Catalysts on Gas Diffusion Electrodes for Electrochemical CO2 Reduction

Electrochemical CO2 conversion is gaining attention as an important process for carbon fixation through the use of renewable electricity to address the climate change crisis. Copper is a unique single-element catalyst that can induce C-C coupling reactions to generate high-value-added compounds. The triple phase boundary has been successfully controlled at the catalyst interface using gas diffusion electrodes (GDEs) over the past few years, resulting in high C-C coupling performance. Therefore, methods to engineer the catalyst interface on the 3D structure of GDE are of significant importance. Generally, the catalyst on the GDE is introduced through physical vaper deposition (PVD) using sputtering or E-beam evaporation, or through solution methods such as spray coating and drop-casting of nano-particles. However, the porous and tortuous 3D structure of the GDE often result in limited conformality and difficulty in obtaining a uniform and controlled infiltration of the catalyst into the support structure.In this study, we synthesized Cu catalysts directly onto GDE surfaces using plasma-enhanced atomic layer deposition (PE-ALD), which allowed for precise tuning of the catalyst size and loading at the nanoscale [1]. The synthesized catalysts were confirmed to be polycrystalline Cu nanoparticles using grazing incidence X-ray diffraction. To demonstrate the advantages of the conformal and tunable control of PE-ALD deposition, we deposited the same areal mass loading of Cu catalyst onto the GDE substrates using PVD, and compared the CO2 reduction activity in an H-cell environment. The PE-ALD Cu catalyst showed more than 3 times higher current density than the PVD catalyst at the same electrode potential, a low (~10%) Faradaic efficiency (FE) for the hydrogen evolution reaction (HER), and greater than 75% FE for C-C coupling to form C2+ products including ethylene and ethanol, which is comparable to the highest performances reported to date for metallic Cu catalysts in a H-cell environment. Furthermore, stable operation was observed for a duration of 15 hours, with minimal changes in activity and selectivity. In conclusion, the introduction of catalysts using PE-ALD on GDE electrodes represents a powerful new synthesis method that can increase both C-C coupling performance and selectivity compared to PVD deposition, due to its adjustable Cu nanoparticle size and high conformality. Reference 1) J. D. Lenef, S.Y. Lee, K. M. Fuelling, K. E. Rivera Cruz, A. Prajapati, D. O. D. Cornejo, T. H. Cho, K. Sun, E. Alvarado, T. S. Arthur, C. A. Roberts, C. Hahn, C. C. L. McCrory, N. P. Dasgupta, Nano Lett. 23, 10779-10787 (2023)

Multiphase transformation and mechanical analysis of polycrystalline [formula omitted] nanoparticle during lithiation via phase diagram-guided phase-field approach

The fabrication of tin (Sn)-based materials with exceptional electrochemical and mechanical properties requires a thorough understanding of the multiphase evolution that occurs during lithiation. However, predicting the microstructural changes during this process using analytical models is challenging due to the intricate interactions among electrode materials, cell operating parameters, complex geometries, and polycrystalline structures. To tackle this challenge, we propose the application of the phase-field method in a grand-potential formulation, that is combined with the smooth boundary method to apply constant-current (de-)lithiation boundary conditions. This approach effectively describes the migration of lithium and the multiphase transitions in polycrystalline electrodes with arbitrary geometries. To investigate nanoparticles with hundreds of grains in two/three dimensions efficiently, we have incorporated this model into the self-developed open-source phase-field solver package MInDes in a highly optimized manner. Further, comparing the output voltage of the simulated lithiation process of LixSn nanoparticles in three dimensions demonstrates an excellent correlation with experimental results. Based on this, we analyze the mechanical performance of polycrystalline nanoparticles with varying amounts of copper doping and evaluate the maximal von Mises stress during lithiation to predict the onset of crack formation.

Synthesis and multifunctional characterizations of Gd2 O3 and Sm2 O3 modified ZnO nanoparticles

In the present communication multifunctional characterizations suitable for spintronics and memory storage devices are described. Double doped (Gd3+, Sm3+) ZnO nanoparticles are prepared from Sol-Gel method using poly vinyl alcohol (PVA) as chelating agent. The as prepared powders are annealed at 500 °C–1000 °C with a step size of 100 °C. The genesis of single phase hexagonal wurtzite structure, morphological and topographical changes, optical, magnetic and mechanical properties were studied with XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), EDS (energy dispersive spectroscopy), UV- DRS (ultraviolet diffuse reflective spectroscopy), PL (photoluminescence), VSM (vibrating sample magnetometer) and pin on disc tribometer. XRD study untangled the crystallite size and found to be in the range23-50nm. Polycrystalline nanoparticles of spherical geometry with induced porosity is observed from SEM study. The particle size associated with the samples annealed at 500 °C and 900 °C is 24 nm and 27 nm respectively from TEM study. Analyzed the proximity of functional groups, molecular vibrations in the range of 400-4000 cm−1 employing FTIR (Fourier transform infrared spectroscopy). EDS results revealed the stoichiometry of the produced samples. The pronounced optoelectronic applications of Zn1-x Gdx Smx O (ZGS) can be attributed to the large band gap (3.50–3.02 eV) associated with the materials with rise in annealing temperature. The room temperature ferromagnetism was evidenced with double doped ZnO nanomaterials. The wear coefficient, and friction coefficient were evaluated using pin-on-disc tribometer. The utility of materials as solid state lubricants was confiscated from the range of frictional coefficient values (0.067–0.893).

Catalyst-On-Hotspot Nanoarchitecture: Plasmonic Focusing of Light onto Co-Photocatalyst for Efficient Light-To-Chemical Transformation.

Plasmon-mediated catalysis utilizing hybrid photocatalytic ensembles promises effective light-to-chemical transformation, but current approaches suffer from weak electromagnetic field enhancements from polycrystalline and isotropic plasmonic nanoparticles as well as poor utilization of precious co-catalyst. Here, efficient plasmon-mediated catalysis is achieved by introducing a unique catalyst-on-hotspot nanoarchitecture obtained through the strategic positioning of co-photocatalyst onto plasmonic hotspots to concentrate light energy directly at the point-of-reaction. Using environmental remediation as a proof-of-concept application, the catalyst-on-hotspot design (edge-AgOcta@Cu2O) enhances photocatalytic advanced oxidation processes to achieve superior organic-pollutant degradation at ≈81% albeit having lesser Cu2O co-photocatalyst than the fully deposited design (full-AgOcta@Cu2O). Mass-normalized rate constants of edge-AgOcta@Cu2O reveal up to 20-fold and 3-fold more efficient utilization of Cu2O and Ag nanoparticles, respectively, compared to full-AgOcta@Cu2O and standalone catalysts. Moreover, this design also exhibits catalytic performance >4-fold better than emerging hybrid photocatalytic platforms. Mechanistic studies unveil that the light-concentrating effect facilitated by the dense electromagnetic hotspots is crucial to promote the generation and utilization of energetic photocarriers for enhanced catalysis. By enabling the plasmonic focusing of light onto co-photocatalyst at the single-particle level, the unprecedented design offers valuable insights in enhancing light-driven chemical reactions and realizing efficient energy/catalyst utilizations for diverse chemical, environmental, and energy applications.

Bio-mediated electrochemically synthesis of silver nanoparticles using green tea (Camellia sinensis) leaves extract and their antibacterial activity

Since the antibacterial properties of silver nanoparticles are well established, the synthesis method for AgNPs, which provides excellent antibacterial activity, is highly promising. The study investigated the inexpensive, fast, and environmentally friendly synthesis of silver nanoparticles (AgNPs) using green tea leaf extract as a bio-mediated electrochemical synthesis. The green tea extract solution acts as an electrolyte in the system, ensuring that the electrolyte occurs and facilitating the formation of AgNP. The AgNP formation was indicated by a single peak at 421 nm. FTIR spectra revealed that green tea extract plays a dual role as a reducing and stabilizing agent. The method produces polycrystalline nanoparticles with sizes ranging from 8 to 26 nm, a mostly spherical shape, and a high purity (96.25 % in mass). Antibacterial assay of AgNP against E. coli and S. aureus showed the highest activity compared to Ag+ ions, green tea extract, and synthesized AgNP using NaBH4. The results provide a new method for producing AgNPs with excellent antibacterial activity.

Defect Rich MoSe2 2H/1T Hybrid Nanoparticles Prepared from Femtosecond Laser Ablation in Liquid and Their Enhanced Photothermal Conversion Efficiencies.

MoSe2 2H/1T hybrid nanoparticles are prepared by femtosecond laser ablation of MoSe2 powder in isopropyl alcohol with different laser powers and ablation times, and their formation mechanisms and photothermal conversion efficiencies (PTCEs) are studied. Two types of spherical nanoparticles are observed. The first type are onion-structured nanoparticles that are formed by nucleation on the surfaces of melted droplets followed by inward growth of {002} planes of MoSe2 . The second type are polycrystalline nanoparticles, formed by coalescence of crystalline nanoclusters fragmented from the powder during the laser ablation. The nanoparticle size in all samples shows a bimodal distribution, corresponding to different fragmentation mechanisms. The 2H-to-1T phase transition in the nanoparticles is likely caused by electron doping from the laser-induced plasma. The PTCEs of the nanoparticles increase with laser power and ablation time, the highest PTCE is around 38%. After examining the bandgaps and the Urbach energies of the nanoparticles, it is found that the high PTCEs are primarily attributed to defects and structural disorder in the laser-synthesized nanoparticles, which allow absorption of photons with energies smaller than the bandgap energy and facilitate non-radiative recombination of photo-excited carriers. This article is protected by copyright. All rights reserved.

Lanthanum substituted Ni-Zn ferrite (Ni0.75Zn0.25Fe2O4) nanomaterial and its composite with rGO for degradation of binary dyes under visible light irradiation

Magnetically separable lanthanum modified Ni-Zn spinel ferrite nanoparticles (Ni0.75Zn0.25La0.06Fe1.94O4) and Ni0.75Zn0.25La0.06Fe1.94O4@rGO nanocomposites were successfully synthesized by the sol-gel auto-combustion and sonication methods respectively, for the degradation of binary organic pollutants. The results of x-ray Diffraction (XRD) analysis confirmed the formation of the face centered cubic (FCC) ferrites with the crystallite sizes ranging between 29.74 and 44.94 nm. The optical bandgap of the nano-composite was found to be 1.691 eV as revealed by the diffused reflectance spectral (DRS) study. The formation of the desired composition nanoparticles with a nearly spherical shape and their homogeneous distribution on sheets of rGO were verified by the scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDAX) instrument. The HR-TEM/SEAD analysis also revealed the formation of spherical polycrystalline nanoparticles and their uniform dispensability with a little agglomeration on the sheet of rGO. The degradation studies were conducted using binary dyes (MB and MO) under the irradiation of visible light in the presence of peroxide. The effects of catalyst dose, irradiation time, initial dye concentration, pH value, and recyclability of nanocomposites have been systematically studied. The findings showed that as compared to La3+ substituted Ni-Zn ferrite nanoparticles (78% for MB and 85 % for MO), the magnetic Ni0.75Zn0. 25La0.06Fe1.94O4@rGO nanocomposite exhibited as a potential photocatalyst towards the simultaneous degradation of both dyes (95% for MB and 98% MO) within 40 min under the optimized conditions. The hydroxyl radical (·OH) play a key role for Ni0.75Zn0.25La0.06Fe1.94O4@rGO nanocomposite photocatalyst for photocatalytical degradation of the binary dyes (methyl orange and methylene blue).

Enhanced photocatalytic degradation of 4-nitrophenol using polyacrylamide assisted Ce-doped YMnO3 nanoparticles

This research article mainly reports on the precise structural, optical, and photocatalytic properties of cerium (Ce)-substituted yttrium manganite (YMnO3) nanoparticles synthesized by the polyacrylamide gel method. The characteristics of YMnO3 were investigated by the substitution of Ce into the Y site at various molar percentages. The Raman and X-ray diffraction (XRD) analyses confirmed the pure phase of hexagonal YMnO3, supported by the Rietveld refinement. The microstructural studies indicate inhomogeneous and irregular particle distribution. The X-ray photoelectron spectroscopy (XPS) results show the presence of two ionic states of Mn and Ce along with Y3+ state and oxygen vacancies. Extensive optical exploration using photoluminescence (PL) spectroscopy and UV–Vis–NIR analysis indicates that the intensity of absorption peak increases in the visible region, while the bandgap decreases from 1.42 to 1.30 eV with the Ce ion doping (5 mol%–15 mol%). Photocatalytic properties of the polycrystalline nanoparticles were investigated by degradation of the pollutant 4-nitrophenol. The process of amplified photocatalysis process was elucidated by the lowered bandgap and rate of charge carrier recombination. It can be conjugated from this study that the synthesized nanoparticles may be employed as highly efficient (92.8%) visible light-triggered photocatalysts in a variety of real-world applications.

Research progress of quantum coherence performance and applications of micro/nano scale rare-earth doped crystals

Rare-earth ion doped crystals possess stable solid state physicochemical properties and long optical coherence time and spin coherence time, thus showing important development prospect in quantum information science and technology area. Investigations on macroscopic bulk rare-earth single crystals have obtained many promising results, especially in the field of optical quantum memory. With the rapid development of quantum information science, a variety of new functions or multifunctional integrations are found in rare earth crystal systems, such as on chip quantum storage, microwave to optical frequency conversion, scalable quantum single photon sources, and quantum logic gates. As a result, beyond the macroscopic bulk rare-earth single crystals, micro/nano-scale rare-earth crystals have received much attention in recent years and they are regarded as promising candidates in highly integrated hybrid quantum systems and miniaturized quantum devices. Moreover, wet chemical method synthesized micro/nano-scale rare-earth crystals have lower growth difficulty and more flexible manipulation in volume, shape and composition. Therefore, exploring high-performance micro/nano-scale rare-earth crystals and precisely manipulating their quantum states have become one of the important directions in today’s quantum information science and technology research. In this review, we first briefly introduce the basic concepts and high resolution spectroscopic techniques that are commonly used in rare earth ion doped crystals for quantum information science and technologies, such as hole burning technique and photon echo technique. Then we summarize comprehensively recent research status and development trends of rare earth ion doped polycrystalline nanoparticles, thin films, single crystal based micro systems, and some other micro/nano-scale rare earth platforms in terms of material fabrication, quantum coherence property, dephasing mechanisms, and also quantum device explorations. The latest research advances in quantum information applications such as quantum storage, quantum frequency conversion, quantum single photon sources and quantum logic gates are given. Finally, we discuss the possible optimization directions and strategies to improve the component design, material synthesis and quantum performance of micro/nano-scale rare earth crystals and their related quantum devices. This review highlights that the micro/nano-scale rare earth crystals may offer many new possibilities for designing quantum light-matter interfaces, thus are promising quantum systems to develop scalable and integrated quantum devices in the future.

Oxygen octahedra distortion‐induced multiferroic properties of Er and Zr co‐doped BiFeO3 nanoparticles

AbstractThe present work unveiled the distortion of oxygen octahedra influencing magnetic and magnetoelectric properties of novel Bi1−xErxFe1−yZryO3 (x = 0, .05, .1, y = .02, .05) polycrystalline nanoparticles by sol–gel route. X‐ray diffraction patterns analysis reveals that pristine BiFeO3 and doped BiFeO3 are crystalized in the rhombohedral structure (R3c). The Fe–O–Fe bond angle of Bi1−xErxFe1−yZryO3 (x = 0, .05, .1, y = .02, .05) varies between 141° and 159.62° as the concentration of Er (via Bi site) and Zr (via Fe site) ions increases in BiFeO3. As a result, the tilt angle of oxygen octahedra and the canting angle of spiral spin arrangement increase. Hence, the maximum magnetization varies between .03144 and .37558 emu/g in Er and Zr co‐doped BiFeO3 system. The number of electrons per unit cell of Bi1−xErxFe1−yZryO3 (x = 0, .05, .1, y = .02, .05) lies between 733.38 and 831, respectively. Further, the number of coherently diffracting domains increases from 3.07 to 5.21, and then it decreases when Er and Zr are increased in BiFeO3. Consequently, the magnetoelectric coupling coefficient varies between .0265 and .2511 mV/cm Oe, respectively. Particularly, Bi0.95Er0.05Fe0.98Zr0.02O3 shows enhanced magnetic and magnetoelectric behaviors compared to other samples.

Band Gap Reduction and Improved Ferromagnetic Ordering via Bound Magnetic Polarons in Zn(Al, Ce)O Nanoparticles

ABSTRACT Polycrystalline nanoparticles of Al-doped and Ce-co-doped ZnO were processed through sol-gel co-precipitation. Crystallite sizes determined from XRD were in the range of 10.90 to 48.77 nm. FTIR spectra indicated a stretching mode of Zn-O bond. The insertion of Al and Ce at Zn-O site created Al-O and Ce-O bonds. UV-vis spectra favoured the formation of impurity levels by doping and co-doping. Their overlapping with the conduction band edge led to the reduction of band-gap. Blue-green emission which arises from radiative recombination of a photogenerated hole with an electron occupying oxygen vacancy was observed in photoluminescence spectra. FESEM suggested granular growth in undoped ZnO which changed to diverse structures such as nano-bar and cluster of elongated grains. Significant improvement in room temperature ferromagnetism (RTFM) was noticed by co-doping of Ce in Al-doped ZnO. Formation of bound magnetic polarons (Ce3+-Vo-Ce3+) was the primary mechanism responsible for the improvement in RTFM.

Scanning pulsed laser ablation in liquids: An alternative route to obtaining biocompatible YbFe nanoparticles as multiplatform contrast agents for combined MRI and CT imaging

Ytterbium ferrites are being used in many promising applications, such as visible-light photocatalysis, solar cells, magnetooptic devices, electro-magnetic equipment, etc., due to their fantastic ferroelectric and ferromagnetic properties. However, despite their good magnetic and radiopaque features, the use of ytterbium ferrites as multiplatform contrast agents in magnetic resonance imaging (MRI) and X-ray computed tomography (CT) is still under-developed. This is mainly due to difficulties in obtaining stable and biocompatible aqueous colloidal dispersions of ytterbium ferrite nanoparticles. In order to overcome this limitation, this work explores an eco-friendly method to directly synthesize such dispersions by liquid-assisted pulsed laser ablation of ytterbium ferrite massive targets. First, orthorhombic bulk YbFeO3 targets were obtained by a reaction-sintering method. Then, colloidal dispersions of nanoparticles were produced directly in both distilled water and ethanol by irradiating the bulk YbFeO3 targets with high-power infrared nanosecond lasers pulses. A battery of techniques has been used to characterize the as synthesized YbFeO3 targets and colloidal dispersions of YbFe nanoparticles to determine their composition, structure, magnetic properties, X-ray attenuation potentials, and colloidal properties. Moreover, the biocompatibility of the systems was also analysed by MTT cell viability assay. Results indicated that the use of distilled water as ablation medium yields colloidal dispersions consisted mainly of paramagnetic ytterbium ferrite nanoparticles. Contrarily, the use of ethanol as solvent leads to colloidal dispersions of polycrystalline nanoparticles with both ferromagnetic and paramagnetic behaviour, due to the coexistence, in each nanoparticle, of ytterbium ferrite, ytterbium oxide, and iron oxide crystalline phases. Both colloidal dispersions exhibit also high biocompatibility and suitable X-ray attenuation properties. Moreover, they show bio-safe hydrodynamic sizes (lower than 200 nm) with acceptable overall hydrodynamic polydispersity index values (under 0.4), being stable in water for several weeks. These results pave the way for the future evaluation of Yb–Fe based nanoparticles as multiplatform contrast agents in multimodal MRI and CT imaging.

Green synthesis of gold nanoparticles (AuNPs) using Caulerpa racemosa and evaluation of its antibacterial and cytotoxic activity against human lung cancer cell line

The present study reports the synthesis of gold nanoparticles (AuNPs) using ‘sea grapes’ (Macroalgae) of Caulerpa racemosa extract in a simple, fast and environmentally friendly biogenic method. The formation of spherical, stable, polycrystalline nanoparticles with an average size of 18–45 nm was demonstrated by UV–vis spectroscopy, SEM, high-resolution transmission electron microscopy and X-ray diffraction measurements. Furthermore, FTIR analysis confirmed the presence of phytochemical constituents in the form of functional groups involved in AuNPs synthesis. Antimicrobial activities confirmed that Gram-negative bacteria, here represented by Escherichia coli, were found to be more sensitive to synthesized AuNPs than Gram-positive bacteria, represented by Staphylococcus aureus. The synthesized nanoparticles also showed cytotoxicity against human lung cancer cells (H460) with an IC50 value of 25 µg/mL. Furthermore, our findings show that AuNPs derived from C. racemosa extract are able to induce apoptosis activation via extrinsic and intrinsic pathways and mitochondrial pathways. These findings lay the groundwork for future research against emerging multi-drug resistant bacterial pathogens, as well as lung cancer treatment.

Tuning Ag-modified NaTaO3 to achieve high CO selectivity for the photocatalytic conversion of CO2 using H2O as the electron donor

Ag-loaded NaTaO3 was used for the photocatalytic conversion of CO2 using H2O as the electron donor, and the effect of the nanoparticle size, Ag loading, and crystal structure on the photocatalytic activity and CO selectivity were investigated. The sizes of the Ag nanoparticles could be tuned by controlling the photodeposition time, and relatively larger Ag nanoparticles were found to show higher CO selectivity. During the photocatalytic reaction, the initially polycrystalline Ag nanoparticles became single crystalline owing to the dissolution and redeposition of Ag, and the change in morphology reduced the CO selectivity. To solve this problem, Ag-Cr dual cocatalysts having a core–shell structure were developed. Subsequently, the locations and sizes of the Ag nanoparticles on the surfaces of NaTaO3 were maintained during the reaction because of the protection by the chromium shell, thus providing stable and selective CO production via the photocatalytic conversion of CO2 by H2O.

Effectiveness of Silver Nanoparticles Deposited in Facemask Material for Neutralising Viruses.

Cloth used for facemask material has been coated with silver nanoparticles using an aerosol method that passes pure uncoated nanoparticles through the cloth and deposits them throughout the volume. The particles have been characterized by electron microscopy and have a typical diameter of 4 nm with the atomic structure of pure metallic silver presented as an assortment of single crystals and polycrystals. The particles adhere well to the cloth fibers, and the coating consists of individual nanoparticles at low deposition times, evolving to fully agglomerated assemblies in heavy coatings. The cloth was exposed to Usutu virus and murine norovirus particles in suspension and allowed to dry, following which, the infectious virus particles were rescued by soaking the cloth in culture media. It was found that up to 98% of the virus particles were neutralized by this contact with the silver nanoparticles for optimum deposition conditions. The best performance was obtained with agglomerated films and with polycrystalline nanoparticles. The work indicates that silver nanoparticles embedded in masks can neutralize the majority of virus particles that enter the mask and thus increase the opacity of masks to infectious viruses by up to a factor of 50. In addition, the majority of the virus particles released from the mask after use are non-infectious.