Unraveling the effect of Gd doping on the structural, optical, and magnetic properties of ZnO based diluted magnetic semiconductor nanorods

Fine-Tuning the Photocatalytic Activity of the Anatase {1 0 1} Facet through Dopant-Controlled Reduction of the Spontaneously Present Donor State Density

The present study highlights the importance of the net density of charge carriers at the ground state on photocatalytic activity of the faceted particles, which can be seen as a highly underexplored problem. To investigate it in detail, we have systematically doped {1 0 1} enclosed anatase nanoparticles with Gd3+ ions to manipulate the charge carrier concentration. Furthermore, control experiments using an analogical Nb5+ doped sample were performed to discuss photocatalytic activity in the increased range of free electrons. Overall results showed significant enhancement of phenol degradation rate and coumarin hydroxylation, together with an increase of the designed Gd/Ti ratio up to 0.5 at. %. Simultaneously, the mineralization efficiency, measured as a TOC reduction, was controlled between the samples. The observed activity enhancement is connected with the controlled decrease of the donor state density within the materials, being the net effect of the spontaneously present defects and introduced dopants, witch reduce hydroxylation and the hole trapping ability of the {1 0 1} facets. This allows to fine-tune multi-/single-electron processes occurring over the prepared samples, leading to clear activity maxima for 4-nitrophenol reduction, H2O2 generation, and ·OH formation observed for different donor densities. The optimized material exceeds the activity of the TiO2 P25 for phenol degradation by 52% (377% after surface normalization), showing its suitable design for water treatment. These results present a promising approach to boost photocatalyst activity as the combined result of the exposed crystal facet and dopant-optimized density of ground-state charge carriers.

Preparation and characterization of sulphur and zinc oxide Co-doped graphitic carbon nitride for photo-assisted removal of Safranin-O dye

Recently, there has been significant interest in photocatalytic reactions involving graphitic carbon nitride (g-C3N4) due to its sp2-hybridized carbon and nitrogen content and it is an ideal candidate for blending with other materials to enhance performance. Here, we have synthesized and analyzed both doped and undoped g-C3N4 nanoparticles. Specifically, we co-doped sulfur (S) into g-C3N4, integrated it with ZnO particles, and investigated the photocatalytic potential of these nanocomposites to remove Safranin-O dye. The initial step involved the preparation of pure g-C3N4 through calcination of urea. Subsequently, S-g-C3N4 was synthesized by calcining a mixture of urea and thiourea with a 3 : 1 ratio. Finally, the ZnO-S-g-C3N4 composite was synthesized using the liquid exfoliation technique, with distilled water serving as the exfoliating solvent. These samples were characterized by advanced techniques, including UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), energy dispersive X-ray (EDX) and scanning electron microscopy (SEM), to assess their crystallinity, morphology, optical properties, and phase purity. Subsequently, these nanocomposites were employed in catalytic and photocatalytic processes to remove the Safranin-O dye (SO). The results highlighted the formation of Z-scheme junction responsible for ZnO-S-g-C3N4's significant performance improvement. The comparison of results demonstrated that S-g-C3N4 and ZnO-S-g-C3N4 composites revealed an effective removal of Safranin-O dye in the presence of UV-light as compared to pure g-C3N4, as it was attributed to the phenomenon of improved separation of photogenerated charge carriers as a result of heterojunction formation between S-g-C3N4 and ZnO interfaces. In addition to improving photocatalytic performance, this study presents a facile route for producing ZnO-S-g-C3N4 composite with superior adsorption capabilities and selectivity.

Noninvasive treatment of psoriasis and skin rejuvenation using an akermanite-type narrowband emitting phosphor

Psoriasis is a noncontagious, long-lasting skin infection that affects many people around the world. Numerous therapeutic artificial treatments are available for the treatment of psoriasis, such as photodynamic therapy using broadband ultraviolet (UV) lamps, which have harmful effects on human skin. Similarly, the natural healing systems such as sunlight have a higher risk of sunburn and can cause dangerous forms of skin cancer. Significant light emission of a specific wavelength (in the UV range), and phosphor-based devices demonstrate the effectiveness of treating psoriasis without damaging the skin. Gd3+ -doped calcium magnesium silicate [Ca2 MgSi2 O7 :Gd3+ ,(CMS:Gd3+ )] phosphor is one of the ideal phosphors that emit specific narrow UV wavelengths for curing psoriasis and is in great demand in the field of dermatology. Photoluminescence analysis at room temperature (~25°C) shows that the synthesized CMS:Gd3+ phosphor emits narrowband UV-B light with a peak intensity at 314 nm. Comparative studies of the standard action spectrum of psoriasis with the emission spectrum of the CMS:Gd3+ phosphor show that the synthesized phosphor was the most suitable material for treating a variety of diseases, including psoriasis, vitiligo, type-1 diabetes, dental disease, sleep and mood disorders, and other skin diseases.

Organic and inorganic nanomaterials: fabrication, properties and applications

Nanomaterials and nanoparticles are a burgeoning field of research and a rapidly expanding technology sector in a wide variety of application domains. Nanomaterials have made exponential progress due to their numerous uses in a variety of fields, particularly the advancement of engineering technology. Nanoparticles are divided into various groups based on the size, shape, and structural morphology of their bodies. The 21st century's defining feature of nanoparticles is their application in the design and production of semiconductor devices made of metals, metal oxides, carbon allotropes, and chalcogenides. For the researchers, these materials then opened a new door to a variety of applications, including energy storage, catalysis, and biosensors, as well as devices for conversion and medicinal uses. For chemical and thermal applications, ZnO is one of the most stable n-type semiconducting materials available. It is utilised in a wide range of products, from luminous materials to batteries, supercapacitors, solar cells to biomedical photocatalysis sensors, and it may be found in a number of forms, including pellets, nanoparticles, bulk crystals, and thin films. The distinctive physiochemical characteristics of semiconducting metal oxides are particularly responsible for this. ZnO nanostructures differ depending on the synthesis conditions, growth method, growth process, and substrate type. A number of distinct growth strategies for ZnO nanostructures, including chemical, physical, and biological methods, have been recorded. These nanostructures may be synthesized very simply at very low temperatures. This review focuses on and summarizes recent achievements in fabricating semiconductor devices based on nanostructured materials as 2D materials as well as rapidly developing hybrid structures. Apart from this, challenges and promising prospects in this research field are also discussed.

Characterization and evaluation of the therapeutic benefits of pure and lanthanides mono- and co-doped zinc oxide nanoparticles

The effect of Lanthanides-doping on the structural, optical, morphological, antibacterial and anticancer properties of zinc oxide (ZnO) nanoparticles was investigated. Pure ZnO, Zn_0.9La_0.1O, Zn_0.9Ce_0.1O, and Zn_0.9La_0.05Ce_0.05O were fabricated through the chemical co-precipitation route. The structural and morphological properties were studied using the X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The optical properties were analyzed by photoluminescence spectroscopy (PL). The inhibitory effect of the synthesized nanoparticles (NPs) was assessed against six bacterial strains using the agar well diffusion and broth micro-dilution methods. The anticancer potential of the synthesized NPs was assessed against two human colon cancer cell lines Caco-2 and HCT-116. The appearance of the La₂O₃ and CeO₂ secondary phases upon doping La³⁺ and Ce³⁺ ions induced structural and morphological changes. The large distorted hexagonal morphology of pure ZnO is transformed into small sized distorted hexagonal form. The photoluminescence spectra revealed the point defects resulting from Lanthanum (La) and cerium (Ce) doping. The prepared NPs significantly inhibited the growth of the six investigated bacteria and induced cytotoxic effects and morphological changes against Caco-2 and HCT-116 cell lines. This study showed that doping ZnO with lanthanide ions such as La³⁺ and Ce³⁺ provide promising biological applications. These NPs showed a potent antibacterial and anticancer effect towards the investigated bacterial strains and colon cancer cell lines. These findings point to the importance of the biological applications of NPs, and the possibility of investigating other biomedical applications for NPs.

Effect of Al Concentration on Structural, Optical and Electrical Properties of (Gd, Al) Co-Doped ZnO and Its n-ZnO/p-Si (1 0 0) Heterojunction Structures Prepared via Co-Sputtering Method

Heterojunction structures of n-ZnO/p-Si were prepared through the growth of undoped ZnO and (Gd, Al) co-doped ZnO films onto p-type Si (1 0 0) substrates, using a co-sputtering method. The structural and optical properties of the Gd-doped ZnO films were studied as a function of different Al doping concentrations. The X-ray diffraction profiles indicated that the films had a nanocrystalline structure of ZnO with a (0 0 2) preferential orientation. An increase in the Al doping concentration deteriorated the (0 0 2) diffraction peak intensity. The transmittance measurements in the UV-Vis wavelength range indicated that the film's optical gap increased with increase in Al doping concentration. The heterojunction parameters were evaluated using the current-voltage (I-V) characterization carried out of the fabricated n-ZnO/p-Si heterostructure, in dark conditions at room temperature. From these measurements, the n-ZnO-based DMS/p-Si heterojunction diode with the use of (Gd, Al) co-doped ZnO film showed the lowest leakage current of 1.28 × 10^-8 A and an ideality factor η of 1.11, close to the ideal diode behavior of η = 1, compared to the n-Gd-doped ZnO/p-Si and n-undoped ZnO/p-Si heterojunction diodes.

Entrapped Molecule-Like Europium-Oxide Clusters in Zinc Oxide with Nearly Unaffected Host Structure

Nanocrystalline ZnO sponges doped with 5 mol% EuO_1.5 are obtained by heating metal-salt complex based precursor pastes at 200-900 °C for 3 min. X-ray diffraction, transmission electron microscopy, and extended X-ray absorption fine structure (EXAFS) show that phase separation into ZnO:Eu and c-Eu₂ O₃ takes place upon heating at 700 °C or higher. The unit cell of the clean oxide made at 600 °C shows only ≈0.4% volume increase versus undoped ZnO, and EXAFS shows a ZnO local structure that is little affected by the Eu-doping and an average Eu³⁺ ion coordination number of ≈5.2. Comparisons of 23 density functional theory-generated structures having differently sized Eu-oxide clusters embedded in ZnO identify three structures with four or eight Eu atoms as the most energetically favorable. These clusters exhibit the smallest volume increase compared to undoped ZnO and Eu coordination numbers of 5.2-5.5, all in excellent agreement with experimental data. ZnO defect states are crucial for efficient Eu³⁺ excitation, while c-Eu₂ O₃ phase separation results in loss of the characteristic Eu³⁺ photoluminescence. The formation of molecule-like Eu-oxide clusters, entrapped in ZnO, proposed here, may help in understanding the nature of the unexpected high doping levels of lanthanide ions in ZnO that occur virtually without significant change in ZnO unit cell dimensions.

Ultrafast Ambient-Air Exsolution on Metal Oxide via Momentary Photothermal Effect

The process of exsolution for the synthesis of strongly anchored metal nanoparticles (NPs) on host oxide lattices has been proposed as a promising strategy for designing robust catalyst-support composite systems. However, because conventional exsolution processes occur in harsh reducing environments at high temperatures for long periods of time, the choice of support materials and dopant metals are limited to those with inherently high thermal and chemical stability. Herein, we report the exsolution of a series of noble metal catalysts (Pt, Rh, and Ir) from metal oxide nanofibers (WO₃ NFs) supports in an entirely ambient environment induced by intense pulsed light (IPL)-derived momentary photothermal treatment (>1000 °C). Since the exsolution process spans an extremely short period of time (<20 ms), unwanted structural artifacts such as decreased surface area and phase transition of the support materials are effectively suppressed. At the same time, exsolved NPs (<5 nm) with uniform size distributions could successfully be formed. To prove the practical utility of exsolved catalytic NPs functionalized on WO₃ NFs, the chemiresistive gas sensing characteristics of exsolved Pt-decorated WO₃ NFs were analyzed, exhibiting high durability (>200 cyclic exposures), enhanced response (R_air/R_gas > 800 @ 1 ppm/350 °C), and selectivity toward H₂S target gas. Altogether, we successfully demonstrated that ultrafast exsolution within a few milliseconds could be induced in ambient conditions using the IPL-derived momentary photothermal treatment and contributed to expanding the practical viability of the exsolution-based synthetic approaches for the production of highly stable catalyst systems.

Magnetic Domain Characterization and Physical Properties of Gd-Doped and (Gd, Al) Co-Doped ZnO Thin Films

Undoped ZnO, Gd-doped ZnO with various doping concentration (1, 3, 5, and 7 at%), and 3 at% (Gd, Al) co-doped ZnO films were prepared on a glass substrate using the co-reactive sputtering method. The influence of the doping and co-doping process on the films was characterized using X-ray diffraction, FESEM, EDX, MFM, VSM, UV-VIS spectroscopy, and the Hall Effect measurement at room temperature. XRD study confirmed that the Gd and Al ions are incorporated into a ZnO lattice. EDX analysis confirmed the existence of Zn, O, Al, and Gd elements in the prepared Gd-doped ZnO and (Gd, Al) co-doped ZnO films, which suggests the successful doping procedure. All the deposited films obtained maximum optical transmittance above 80%, showing a high transparency of the films in the visible region. The optical band gap was found red-shifted from 3.11 to 3.21 eV with the increase in Gd doping concentration. The increase in band gap energy from 3.14 eV to 3.16 eV was obtained for 3 at% Gd and 3 at% (Gd, Al) co-doped ZnO films. The MFM measurement proved the existence of room-temperature ferromagnetism and spin polarization in Gd and (Gd, Al) co-doped ZnO films. By co-doping with Al, the result obtained from MFM shows the enhancement of magnetic properties, as it exhibited a smaller domain size with a shorter magnetic correlation length L, a larger phase shift Φ_rms, and the highest value of δf_rms compared to the sample with 3 at% Gd incorporated into ZnO. The carrier concentration and electrical conductivity increased with the increase in Gd concentration, whereas the electrical resistivity and hall mobility showed a reverse trend. The similar trend of results obtained for 3 at% (Gd, Al) co-doped ZnO as compared to 3 at% Gd-doped ZnO also indicates greater electrical properties after a shallow donor such as aluminum was incorporated into Gd-doped ZnO thin films. In conclusion, for future applications, one should consider the possible influence of other types of shallow donor incorporation in an attempt to enhance the properties of new types of diluted magnetic semiconductors (DMSs).

Investigations on structural, electronic and optical properties of ZnO in two-dimensional configurations by first-principles calculations

The electronic structures and optical properties of two-dimensional (2D) ZnO monolayers in a series of configurations were systematically investigated by first-principles calculations with HubbardUevaluated by the linear response approach. Three types of 2D ZnO monolayers, as planer hexagonal-honeycomb (Plan), double-layer honeycomb (Dlhc), and corrugated tetragonal (Tile) structures, show a mechanical and dynamical stability, while the Dlhc-ZnO is the most energetically stable configuration and Plan-ZnO is the second one. Each 2D ZnO monolayer behaves as a semiconductor with that Plan-, Dlhc-ZnO have a direct band gap of 1.81 eV and 1.85 eV at theΓpoint, respectively, while Tile-ZnO has an indirect band gap of 2.03 eV. Interestingly, the 2D ZnO monolayers all show a typical near-free-electron character for the bottom conduction band with a small effective mass, leading to a tremendous optical absorption in the whole visible and ultraviolet window, and this origination was further confirmed by the transition dipole moment. Our investigations suggest a potential candidate in the photoelectric field and provide a theoretical guidance for the exploration of wide-band-gap 2D semiconductors.

Lanthanide (Eu, Tb, La)-Doped ZnO Nanoparticles Synthesized Using Whey as an Eco-Friendly Chelating Agent

Strategies for production and use of nanomaterials have rapidly moved towards safety and sustainability. Beyond these requirements, the novel routes must prove to be able to preserve and even improve the performance of the resulting nanomaterials. Increasing demand of high-performance nanomaterials is mostly related to electronic components, solar energy harvesting devices, pharmaceutical industries, biosensors, and photocatalysis. Among nanomaterials, Zinc oxide (ZnO) is of special interest, mainly due to its environmental compatibility and vast myriad of possibilities related to the tuning and the enhancement of ZnO properties. Doping plays a crucial role in this scenario. In this work we report and discuss the properties of undoped ZnO as well as lanthanide (Eu, Tb, and La)-doped ZnO nanoparticles obtained by using whey, a by-product of milk processing, as a chelating agent, without using citrate nor any other chelators. The route showed to be very effective and feasible for the affordable large-scale production of both pristine and doped ZnO nanoparticles in powder form.

A closed local-orbital unified description of DFT and many-body effects

Density functional theory (DFT) is usually formulated in terms of the electron density as a function of positionn(r). Here we discuss an alternative formulation of DFT in terms of the orbital occupation numbers {n_α} associated with a local-orbital orthonormal basis set {ϕ_α}. First, we discuss how the building blocks of DFT, namely the Hohenberg-Kohn theorems, the Levy-Lieb approach and the Kohn-Sham method, can be adapted for a description in terms of {n_α}. In particular, the total energy is now a function of {n_α},E[{n_α}], and a Kohn-Sham-like Hamiltonian is derived introducing the effects of the electron-electron interactions via effective potentials,{Vαeff=∂Eee[{nβ}]/∂nα}. In a second step we consider the Hartree and exchange energies and discuss how to describe them, in the spirit of a DFT approach, in terms of the orbital occupation numbers. In this contribution special attention is paid to the description of the (intra-atomic) correlation energy and corresponding correlation potentials {V_corr,α}. For this purpose, a model system is analyzed in detail, whereby an atomic Hamiltonian interacts with the environment via a simplified model; the use of this model allows us to obtain the correlation energy and potentials (in terms of {n_α}) for different cases corresponding to low, intermediate and high electron correlations.

Experimental and modeling study of ZnO:Ni nanoparticles for near-infrared light emitting diodes

This work is devoted to the synthesis and study of the different properties of ZnO nanoparticles (NPs) doped with the Ni element. We have used a simple co-precipitation technique for the synthesis of our samples and various structural, morphological and optical techniques for their analysis. Energy-Dispersive X-ray spectroscopy (EDX) confirms the stoichiometry of the samples. The X-Ray Diffraction (XRD) patterns reveal the hexagonal wurtzite phase of polycrystalline ZnO with a P63mc space group. Debye Scherrer and Williamson–Hall methods show that the average size of crystallites is around 40 nm. Transmission electron microscopy (TEM) images confirm the XRD results. The optical spectrum of Zn_0.95Ni_0.5O shows the presence of near-band-edge (NBE) ultraviolet emission. The absorption defect bands appearing near the blue–green region and near infrared emission are attributed to the Ni²⁺ intra-3d luminescence. The electronic structure of the Ni²⁺ doped ZnO NPs confirms the T_d site symmetry of Ni²⁺ in the ZnO host crystal and leads to a perfect correlation between calculated and experimental energy levels.

This work is devoted to the synthesis and study of the different properties of ZnO nanoparticles (NPs) doped with the Ni element.

Diluted magnetic semiconductor properties in TM doped ZnO nanoparticles

The hydrothermal method was used to create dilute magnetic semiconductor nanoparticles of Zn_1−xCo_xO (x = 0, 0.01, 0.05, 0.09). The effect of cobalt doping on the microstructure, morphological and optical properties of Zn_1−xCo_xO was also studied and the Co doping to host ZnO was confirmed from XRD and EDX analysis. The structural analysis showed that doping of cobalt into ZnO decreased the crystallinity, but the preferred orientation didn't change. SEM analysis revealed that the cobalt dopant did not have a strong influence on the shape of the synthesized nanoparticles. No defect-related absorption peaks were observed in the UV-Vis spectra. The crystallinity of the doped samples was improved by high growth temperature and long growth time. Ferromagnetic behavior above room temperature was detected in co-doped ZnO nanoparticles. The ferromagnetic behavior increased with increasing Co (up to x = 0.05) doping. The ferromagnetic behavior declined when the Co content was further increased. Related research shows that doped ZnO nanoparticles have better dielectric, electrical conductivity, and magnetic properties than pure ZnO. This high ferromagnetism is usually a response reported for dilute magnetic semiconductors. These semiconductor nanoparticles were further used to designed spintronic based applications.

The enlarged central part M–H loop shows for the Co = 0.09 doped ZnO sample, the ferromagnetic (FM) behavior increased, i.e., a M_r of 0.2412 emu g⁻¹ with a H_c of 85 Oe.

Excited states of modified oxygen-deficient centers and Si quantum dots in Gd-implanted silica glasses: emission dynamics and lifetime distributions

The emission centers and excited state characteristics of silica glasses implanted with Gd ions were studied by time-resolved pulsed cathodoluminescence. It was found that in the process of ion implantation, two types of new emission centers associated with Gd ions as well as Si quantum dots are formed in glassy silica. The distributions of excited states over the lifetime were found for both new centers and Si quantum dots. The nature of dispersion of the emission decay time was discussed in terms of structural disorder in the matrix. Thermal annealing and an increase in the ion fluence lead to the stimulation of the formation of Gd-related new centers and Si quantum dots. The micromechanisms for the formation of new Gd-related centers and two types of Si quantum dots were proposed on the basis of two scenarios for the introduction of Gd ions into the SiO₂ network: insertion of Gd into interstitial voids near oxygen-deficient centers and Gd  →  Si substitution with subsequent expulsion of Si atoms to the interstitial voids. New emission oxygen-deficient centers and quantum dots created by ion-beam technology in silica glasses are of interest for the development of new functional materials for photonics, and micro- and opto-electronics.

Iron-Doped ZnO Nanoparticles as Multifunctional Nanoplatforms for Theranostics

Zinc oxide nanoparticles (ZnO NPs) are currently among the most promising nanomaterials for theranostics. However, they suffer from some drawbacks that could prevent their application in nanomedicine as theranostic agents. The doping of ZnO NPs can be effectively exploited to enhance the already-existing ZnO properties and introduce completely new functionalities in the doped material. Herein, we propose a novel synthetic approach for iron-doped ZnO (Fe:ZnO) NPs as a multifunctional theranostic nanoplatform aimed at cancer cell treatment. Pure ZnO and Fe:ZnO NPs, with two different levels of iron doping, were synthesized by a rapid wet-chemical method and analyzed in terms of morphology, crystal structure and chemical composition. Interestingly, Fe:ZnO NPs featured bioimaging potentialities thanks to superior optical properties and novel magnetic responsiveness. Moreover, iron doping provides a way to enhance the electromechanical behavior of the NPs, which are then expected to show enhanced therapeutic functionalities. Finally, the intrinsic therapeutic potentialities of the NPs were tested in terms of cytotoxicity and cellular uptake with both healthy B lymphocytes and cancerous Burkitt's lymphoma cells. Furthermore, their biocompatibility was tested with a pancreatic ductal adenocarcinoma cell line (BxPC-3), where the novel properties of the proposed iron-doped ZnO NPs can be potentially exploited for theranostics.

A local-orbital density functional formalism for a many-body atomic Hamiltonian: Hubbard-Hund's coupling and DFT + U functional

In the conventional DFT + U approach, the mean field solution of the Hubbard Hamiltonian associated with thedorf(iσ) electrons of a transition metal atom is used to define the DFT + U potential acting on theiσ-electrons. In this work, we go beyond that mean field solution by analyzing the correlation energy and potential for a multi-level atom described by a Kanamori Hamiltonian connected to different channels representing the environment. As a first step, we analyze the many-body solution of our model, using a local-orbital density functional formalism that takes as independent variables the orbital occupancies,n_iσ, of the atomic orbitals; accordingly, we present the corresponding density functional solution describing the correlation energy and potential as a function ofn_iσ. Then, we use this analysis to introduce a DFT + U potential extending previous proposals to materials with arbitrarily high correlation. In particular, we find that this potential mainly screens the conventional mean field potential contribution, and also yields new terms associated with the number of atomic electrons. Our results show that the atomic correlation effects enhance the role played by the intra-atomic exchange interaction and favor the formation of magnetic solutions.

Effective antimicrobial activity of ZnO and Yb-doped ZnO nanoparticles against Staphylococcus aureus and Escherichia coli

Nanostructured Zn_1-xYb_xO (0.0 ≤ x ≤ 0.1) powders were prepared by the solution method using polyvinyl alcohol (PVA) and sucrose. The effect of the ytterbium doping content on the structural, morphological, optical and antimicrobial properties was analyzed. X-ray diffraction (XRD) analysis revealed that the hexagonal wurtzite structure was retained, and no secondary phases due to doping were observed. The crystallite size was under 20 nm for all the Zn_1-xYb_xO (0.0 ≤ x ≤ 0.1) powders. The optical band gap was calculated, and the results revealed that this value increased with the ytterbium content, and the E_g values varied from 3.06 to 3.10 eV. The surface chemistry of the powders was analyzed using X-ray photoelectron spectroscopy (XPS), and the results confirmed the oxidation state of ytterbium as 3+ for all the samples. Zn_1-xYb_xO (0.0 ≤ x ≤ 0.1) nanoparticles were tested as antimicrobial agents against Staphylococcus aureus and Escherichia coli, resulting in a potential antimicrobial effect at most of the tested concentrations. These results were used in an artificial neural network (ANN). The results showed that it is possible to generate a model capable of forecasting the absorbance with good precision (error of 1-2%).

Enhancing the UV Emission in ZnO-CNT Hybrid Nanostructures via the Surface Plasmon Resonance of Ag Nanoparticles

The crystal quality and surface states are two major factors that determine optical properties of ZnO nanoparticles (NPs) synthesized through nonaqueous sol-gel routes, and both are strongly dependent on the growth conditions. In this work, we investigate the influence of the different growth temperatures (240 and 300 °C) on the morphology, structural and crystal properties of ZnO NP. The effects of conjoining ZnO NP with carbon nanotubes (CNT) and the role of surface states in such a hybrid nanostructure are studied by optical emission and absorption spectroscopy. We demonstrate that depending on the synthesis conditions, activation or passivation of certain surface states may occur. Next, silver nanoparticles are incorporated into ZnO-CNT nanostructures to explore the plasmon-exciton coupling effect. The observed enhanced excitonic and suppressed defect-related emissions along with blue-shifted optical band gap suggest an intricate interaction of Burstein-Moss, surface plasmon resonance and surface band-bending effects behind the optical phenomena in hybrid ZnO-CNT-Ag nanocomposites.

Unravelling the human triple negative breast cancer suppressive activity of biocompatible zinc oxide nanostructures influenced by Vateria indica (L.) fruit phytochemicals

The present study delineates the biosynthesis of ZnOVI nanostructures by using aqueous fruit extract of V. indica. The study has disclosed the role of V. indica fruit extract as both reducing and capping agents, ushering the formation of ZnOVI nanostructures with distinct morphologies. The formation of ZnOVI nanostructures was corroborated by FT-IR and UV-visible spectroscopy which was further substantiated by the elemental composition study through EDS spectroscopy. The nanostructures were also investigated by Rietveld refinement of PXRD data, FE-SEM, and BET analysis. The morphology, size, and surface area were found to be precursor stoichiometry dependent. The in-vitro cytotoxicity study of ZnOVI nanostructures carried out on MDA-MB468 human triple-negative breast cancer (TNBC) cells has revealed their potential cytotoxicity (91.18 ± 1.98). MTT assay performed on the NIH3T3 mouse fibroblast cells has unfolded the non-toxic nature of ZnOVI nanostructures. Additionally, the results of the AO-EB dual staining assay indicated early apoptosis in TNBC cells by displaying greenish yellow-fluorescence in the nuclei. Reactive oxygen species (ROS) measurement study has confirmed the elevated intracellular levels of ROS, supporting the oxidative-stress induced cytotoxicity in ZnOVI nanostructures treated TNBC cells. Furthermore, the haemocompatibility of ZnOVI nanostructures was evaluated using human erythrocytes. Thus, the obtained results have shown greater potential in the anticancer activity of bio-fabricated ZnOVI nanostructures.

Structural refinement and electrochemical properties of one dimensional (ZnO NRs)1-x(CNs)x functional hybrids for serotonin sensing studies

Herein, the efficient serotonin (5-HT) sensing studies have been conducted using the (ZnO NRs)1-x(CNs)x nanocomposites (NCs) having appropriate structural and electrochemical properties. Initially, the different compositions of ZnO nanorods (NRs), with varying content of carbon nanostructures (CNs=MWCNTs and RGO), are prepared using simple in-situ wet chemical method and thereafter these NCs have been characterized for physico-chemical properties in correlation to the 5-HT sensing activity. XRD Rietveld refinement studies reveal the hexagonal Wurtzite ZnO NRs oriented in (101) direction with space group 'P63mc' and both orientation as well as phase of ZnO NRs are also retained in the NCs due to the small content of CNs. The interconnectivity between the ZnO NRs with CNs through different functional moieties is also studied using FTIR analysis; while phases of the constituents are confirmed through Raman analysis. FESEM images of the bare/NCs show hexagonal shaped rods with higher aspect ratio (4.87) to that of others. BET analysis and EIS measurements reveal the higher surface area (97.895 m2/g), lower charge transfer resistance (16.2 kΩ) for the ZCNT 0.1 NCs to that of other NCs or bare material. Thereafter, the prepared NCs are deposited on the screen printed carbon electrode (SPCE) using chitosan as cross-linked agent for 5-HT sensing studies; conducted through cyclic voltammetry (CV) and square wave voltammetry (SWV) measurements. Among the various composites, ZCNT0.1 NCs based electrodes exhibit higher sensing activity towards 5-HT in accordance to its higher surface area, lower particle size and lower charge transfer resistance. SWV measurements provide a wide linear response range (7.5-300 μM); lower limit of detection (0.66 μM), excellent limit of quantification (2.19 μM) and good reproducibility to ZCNT 0.1 NCs as compared to others for 5-HT sensing studies.

Doped Zinc Oxide Nanoparticles: Synthesis, Characterization and Potential Use in Nanomedicine

Smart nanoparticles for medical applications have gathered considerable attention due to an improved biocompatibility and multifunctional properties useful in several applications, including advanced drug delivery systems, nanotheranostics and in vivo imaging. Among nanomaterials, zinc oxide nanoparticles (ZnO NPs) were deeply investigated due to their peculiar physical and chemical properties. The large surface to volume ratio, coupled with a reduced size, antimicrobial activity, photocatalytic and semiconducting properties, allowed the use of ZnO NPs as anticancer drugs in new generation physical therapies, nanoantibiotics and osteoinductive agents for bone tissue regeneration. However, ZnO NPs also show a limited stability in biological environments and unpredictable cytotoxic effects thereof. To overcome the abovementioned limitations and further extend the use of ZnO NPs in nanomedicine, doping seems to represent a promising solution. This review covers the main achievements in the use of doped ZnO NPs for nanomedicine applications. Sol-gel, as well as hydrothermal and combustion methods are largely employed to prepare ZnO NPs doped with rare earth and transition metal elements. For both dopant typologies, biomedical applications were demonstrated, such as enhanced antimicrobial activities and contrast imaging properties, along with an improved biocompatibility and stability of the colloidal ZnO NPs in biological media. The obtained results confirm that the doping of ZnO NPs represents a valuable tool to improve the corresponding biomedical properties with respect to the undoped counterpart, and also suggest that a new application of ZnO NPs in nanomedicine can be envisioned.

Facile Chemical Synthesis of Doped ZnO Nanocrystals Exploiting Oleic Acid

Zinc oxide nanocrystals (ZnO-NCs) doped with transition metal elements or rare earth elements can be probed for magnetic resonance imaging to be used as a molecular imaging technique for accurate diagnosis of various diseases. Herein, we use Mn as a candidate of transition metal elements and Gd as a presenter of rare earth elements. We report an easy and fast coprecipitation method exploiting oleic acid to synthesize spherical-shaped, small-sized doped ZnO-NCs. We show the improved colloidal stability of oleate-stabilized doped ZnO-NCs compared to the doped ZnO-NCs synthesized by conventional sol-gel synthesis method, i.e., without a stabilizing agent, especially for the Mn dopant. We also analyze their structural, morphological, optical, and magnetic properties. We are able to characterize the persistence of the crystalline properties (wurtzite structure) of ZnO in the doped structure and exclude the formation of undesired oxides by doping elements. Importantly, we determine the room-temperature ferromagnetism of the doped ZnO-NCs. This oleate-stabilized coprecipitation method can be subjected as a standard procedure to synthesize doped and also co-doped ZnO-NCs with any transition metal elements or rare earth elements. In the future, oleate-stabilized Gd/Mn-doped ZnO-NCs can be exploited as magnetic resonance imaging (MRI) contrast agents and possibly increase the signal intensity on T1-weighted images or reduce the signal intensity on T2-weighted images.

Strain and electric field tuning of semi-metallic character WCrCO2MXenes with dual narrow band gap

Motivated by the recent successful synthesis of double-M carbides, we investigate structural and electronic properties of WCrC and WCrCO2monolayers and the effects of biaxial and out-of-plane strain and electric field using density functional theory. WCrC and WCrCO2monolayers are found to be dynamically stable. WCrC is metallic and WCrCO2display semi-metallic character with narrow band gap, which can be controlled by strain engineering and electric field. WCrCO2monolayer exhibits a dual band gap which is preserved in the presence of an electric field. The band gap of WCrCO2monolayer increases under uniaxial strain while it becomes metallic under tensile strain, resulting in an exotic 2D double semi-metallic behavior. Our results demonstrate that WCrCO2is a new platform for the study of novel physical properties in two-dimensional Dirac materials and which may provide new opportunities to realize high-speed low-dissipation devices.

A Bibliometric Analysis of the Publications on In Doped ZnO to be a Guide for Future Studies

This study aims to examine the studies regarding In doped ZnO published in the Web of Science database. A total of 777 articles were reached (31 March 2020). The articles were downloaded for the bibliometric analysis and collected in a file. The file was uploaded to VOSViewer programme in order to reveal the most used keywords, words in the abstracts, citation analyses, co-citation and co-authorship and countries analyses of the articles. The results showed that the most used keywords were “ZnO”, “photoluminescence”, “optical properties”, “thin films” and “doping”. These results indicate that the articles mostly focus on some characteristics of In doped ZnO thin films such as structural, optical and electrical features. When the distribution of the number of articles using the keywords by year was searched, it was found that recent articles focus mainly on synthesis of In doped ZnO film via chemical routes such as sol-gel and hydrothermal syntheses, and on ZnO-based device applications such as solar cells and gas sensors. The most used keywords were also found to be films, X-ray, glass substrate, X-ray Diffraction (XRD), spectra and layer. These results indicate that the studies mostly focus on In doped ZnO thin films as transparent conductive oxide (TCO) material used in device applications like solar cells. In this context, it was found that structural, topographical, optical, electrical and magnetic properties of In doped ZnO films were characterized in terms of defected structure or defect type, substrate temperature, film thickness and In doping content. When the distribution of these words is shown on a year-by-year basis, it is evident that more recent articles tend to focus both on efficiency and performance of In doped ZnO films as TCO in solar cells, diodes and photoluminescence applications both on nanostructures, such as nanoparticles, and nanorods for gas sensor applications. The results also indicated that Maldonado and Asomoza were the most cited authors in this field. In addition, Major, Minami and Ozgur were the most cited (co-citation) authors in this field. The most cited journals were found to be Thin Solid Films, Journal of Materials Science Materials in Electronics and Journal of Applied Physics and, more recently, Energy, Ceramics International, Applied Physics-A, Optik, Material Research Express, ACS Applied Materials and Interfaces and Optical Materials. The most co-cited journals were Applied Physics Letters, Thin Solid Films, Journal of Applied Physics, Physical Review B, and Applied Surface Science. Lastly, the countries with the highest number of documents were China, India, South Korea, USA and Japan. Consequently, it is suggested that future research needs to focus more on synthesis and characterization with different growth techniques which make In doped ZnO suitable for device applications, such as solar cells and diodes. In this context, this study may provide valuable information to researchers for future studies on the topic.

First-principles investigation of nonmetal doped single-layer BiOBr as a potential photocatalyst with a low recombination rate

Nonmetal doping is an effective approach to modify the electronic band structure and enhance the photocatalytic performance of bismuth oxyhalides.