Cr Nanoparticles Research Articles

How Cr doping influences on the properties of ZnO nanoparticles obtained by aqueous synthesis: Exploring at low Cr concentrations

A detailed physico-chemical study of Cr3+-doped ZnO nanoparticles (NPs) obtained via aqueous synthesis was carried out. The NPs acquire greenish tonality as the Cr concentration increased. High efficiency of Cr incorporation into the ZnO lattice was found up to approximately 1 at% Cr. The ZnO:Cr NPs show wurtzite hexagonal phase with a lattice compressed for low Cr concentration and tensed for higher concentrations. Structural, chemical and optical analyses indicate that for low Cr concentration Cr occupies the Zn vacancy sites, owing to the reduction in acceptor compensation by passivating the Zn vacancies and the contribution of the unpaired electron of Cr3+, which induces an increase of electron concentration, changes in the conductivity, transport of carriers, optical properties and ferromagnetic properties, among others. At higher Cr concentrations, the passivation of Zn vacancies by Cr atoms reduces the acceptor contribution, and substantial substitution of Zn atoms by Cr atoms in the ZnO lattice strengthens the retention of O atoms in the Cr-O bonds. This results in a reduction in O vacancy concentration, donor contribution, strain, electron concentration, and luminescence intensity.

Influence of Cr Nanoparticles on Plasma Electrolytic Oxidation Coatings on AM50 Mg Alloy

The addition of Cr nanoparticles to a plasma electrolytic oxidation (PEO) electrolyte offers the possibility of producing layers with a broader range of coating compositions and improved properties. In this study, the effects of nanoparticles and various voltages on coating formation, microscopic morphology, and phase composition were investigated with in situ incorporation of Cr nanoparticles into PEO-coated Mg alloy. The results show that the corrosion performance of the coating was significantly improved when the final voltage was set to 460 V and the concentration of Cr nanoparticles was 1 g/L. Compared to the particle-free coating, the corrosion current density of the coating with the addition of 1 g/L Cr nanoparticles was reduced by two orders of magnitude. The impedance at the low frequency (0.01 Hz) increased by more than one order of magnitude after one hour of immersion, indicating a considerable improvement in corrosion resistance. Due to the high temperature during the coating-formation process, the Cr nanoparticles were oxidized, resulting in the formation of Cr2O3. The existence of Cr2O3 slightly increased the growth rate of the coating and sealed the open pores of the coating.

Developing the Ferromagnetic Feature of ZnS:Cr Nanoparticles by Er Co-doping

Developing the Ferromagnetic Feature of ZnS:Cr Nanoparticles by Er Co-doping

Dietary exposure of Cr nanoparticles to Catla catla fingerlings: Effects on mineral digestibility and carcass composition

This research aimed to see how effectively chromium nanoparticles (Cr-NPs) improve minerals absorption and carcass composition in Catla catla fingerlings given sunflower meal based diets. In a 90-day experimental design, seven test diets were supplemented with graded levels of nano-Cr (0, 0.5, 1, 1.5, 2, 2.5, and 3 mg kg−1) and 15 fingerlings (initial weight; 6.83 ± 0.077 g) were kept in triplicate (25–28 °C). Feed was provided to fingerlings at the rate of 5% of their wet weight and fed twice a day. As an inert marker, chromic oxide was used. The highest effectiveness in minerals absorption (Ca, Na, K, Cu, Fe, Mn, P, Cr, Mg, Zn and Al) was observed at 2 mg kg−1 Cr-NPs supplementation. These levels were statistically more significant (p < 0.05) than the control and other experimental diets. The most optimum results in terms of carcass (crude protein; 62% and ether extraction; 14%) were observed in fingerlings given 2 mg kg−1 doses. In the current study, it was observed that feeding sunflower meal to C. catla fingerlings with supplementation of 2 mg kg−1 of Cr-NPs significantly (p < 0.05) improved mineral absorption and body composition.

Nickel OxideNanoparticles with and without Metallic Doping: Synthesis Structure, Conductivity, Dielectric, and Optical Properties

NiO and NiO metal-doped nanoparticles (NPs) were synthesized using a two-step process. These NPs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption desorption. The cubic structure of the NiO was validated from the similarity of the X-ray diffraction peaks and that all the metallic dopants (Cu and Cr) were stabilized in their sites within NiO structure. TEM revealed the configuration whereby the NiO NPs were arranged side by side and aligned along the same direction, forming a small array shaped agglomerates with around 500 nm length and 50–70 nm diameter. Adsorption-desorption isotherms for N2 indicated that NiO NPs could be characterized by type IV isotherms with a hysteresis loop at relative pressures between 0.5 and 1.0. The Hysteresis loop’s pattern was of H2 type which is a characteristic pattern for inckbottle shaped pores. Dielectric properties and electrical conductivity were conducted at 25 °C – 110 °C and within the frequency range between 100 Hz and 0.3 MHz. Optical properties (e.g. refractive index, optical energy gap, the molar refractivity) for NiO, NiO:Cu, and NiO:Cr NPs were investigated. The data reveal that, the energy gap and the metallization criterion were the lowest for the NiO:Cu NP sample. On the contrary, the refractive index, molar refractivity were the highest for NiO:Cu NP sample.

Speciation of macro- and nanoparticles of Cr2O3 in Hordeum vulgare L. and subsequent toxicity: A comparative study

Chromium (Cr) is reported to be hazardous to environmental components and surrounding biota when levels exceed allowable thresholds. As Cr is extensively utilized in different industries, thereby comprehensively studied for its toxicity. Along with Cr, the applications of nano-Cr or chromium oxide nanoparticles (Cr2O3-NPs) are also expanding; however, the literature is scarce or limited on their phytotoxicity. Thereby, the current work investigated the morpho-physiological insights of macro- and nanoparticles of Cr in Hordeum vulgare L. plants. The increased accumulation and translocation of Cr under the exposure of both forms disturbed the cellular metabolism that might have inhibited germination and growth as well as interfered with the photosynthesis of plants. The overall extent of toxicity was noticeably higher under nanoparticles’ exposure than macroparticles of Cr. The potential cue for such phytotoxic consequences mediated by Cr nanoparticles could be an increased bioavailability of Cr ions which was also supported by their total content, mobility, and factor toxicity index. Besides, to support further these findings, synchrotron X-ray technique was used to reliably identify Cr-containing compounds in the plant tissues. The X-ray spectra of the near spectral region and the far region of the spectrum of K-edge of Cr were obtained, and it was established that the dominant crystalline phase corresponds to Cr2O3 (eskolaite) from the recorded observations. Thus, the obtained results would allow revealing the mechanism of macro- and nanoparticles of Cr induced impacts on plant at the tissue, cellular- and sub-cellular levels.

Combination of cobalt, chromium and titanium nanoparticles increases cytotoxicity in vitro and pro-inflammatory cytokines in vivo

The mixture of different metallic nanoparticles released from intended and unintended wearing of orthopaedic implants such as the Co/Cr cup and head, Co/Cr sleeves or tapers and their interface with Ti stems in the case of hip prostheses are a leading cause of adverse inflammatory responses and cytotoxicity to the host. This study assessed the in vitro cytotoxic effects of three metallic nanoparticles (Co, Cr and Ti) separately and in combination on macrophages. The in vivo effects were also evaluated after peri-tibial soft tissue injection in mice. The results demonstrated that Co, Cr, and Ti nanoparticles and their combination were phagocytosed by macrophages both in vitro and in vivo. High doses of nanoparticles from each individual metal caused a variable rate of cell death in vitro. However, the mixture of Co/Cr/Ti nanoparticles was more toxic than the Co, Cr or Ti metals alone at low doses. Intracellular distribution of Co, Cr, and Ti in the combined group was heterogeneous and associated with distinct morphological features. The results from in vivo experiments showed a significant increase in the mRNA levels of interleukin (IL)-1β, IL-6, IL-8 and tumour necrosis factor (TNF)-α in peri-tibial soft tissue following the administration of Co alone as well as the combination of nanoparticles. This study demonstrated that the combination of Co/Cr/Ti nanoparticles was more cytotoxic than any of the individual metals in vitro and induced higher expression of genes encoding pro-inflammatory cytokines than single metals in vivo. The in vivo model utilised in this study might provide a useful tool for rapid assessment of the effects of unintended release of metal nanoparticles from implants in pre-/post-marketing studies. This study highlights the importance of preclinical assessments of potential nanoparticles produced by wear and tear of metal implants using macrophages and animal models, in particular their combinational toxicity in addition to the assessments of the bulk metallic materials.

Deep eutectic solvent - loaded Fe3O4@MIL-101(Cr) with core–shell structure for the magnetic solid phase extraction of non-steroidal anti-inflammatory drugs in environmental water samples

A novel deep eutectic solvent - loaded magnetic solid phase extraction (DES-L-MSPE) method was proposed, which was based on the direct loading of a hydrophobic DES composed of L-menthol and lactic acid (1:2) into the pores of core–shell magnetic Fe3O4@MIL-101(Cr) nanoparticles. The function of DES was to condition the Fe3O4@MIL-101(Cr) and promote liquid phase microextraction for the analytes. Through coupling with HPLC-UV analysis, this method was utilized for the determination of six non-steroidal anti-inflammatory drugs (NSAIDs), including ketoprofen, naproxen, flurbiprofen, diclofenac sodium, ibuprofen, and mefenamic acid in environmental water samples. The influencing parameters such as type and ratio of DES, amount of adsorbent, sample solution pH, salt concentration, extraction time, elution solvent and time were investigated and optimized in detail. Under the optimal conditions, the method exhibited good linearity (5.0–1000 μg/L for ketoprofen, ibuprofen, 1.5–600 μg/L for flurbiprofen, mefenamic acid, 2.5–1000 μg/L for naproxen and 3.0–600 μg/L for diclofenac sodium with the correlation coefficients ranging from 0.9972 to 0.9993), low limits of detection (0.20–1.1 μg/L), and high precision (RSD < 8.2 %). Besides, the recoveries in spiked lake and river water samples were 89.8 %–110.4 % and 83.8 %–109.0 %, respectively. Taken together, the established method was proved to be simple, fast, highly sensitive and accurate for the determination of NSAIDs from aqueous matrices.

Water stable MIL-101(Cr)/polyacrylonitrile/agarose aerogel for efficient 2, 4-dichlorophenoxyacetic acid adsorption

In this work, novel MIL-101(Cr)/polyacrylonitrile/agarose aerogels (MIL-101(Cr)/PANNs/AG) as efficient adsorbents with hierarchical pores were prepared via a facile physical mixture method combining hydrogen bond self-crosslinking without any chemical linkers. The water stability and underwater compressible of the composite aerogel are improved by incorporating polyacrylonitrile nanofibers. MIL-101(Cr)/PANNs/AG aerogels are well characterized systematically and the adsorption performance for 2, 4-dichlorophenoxyacetic acid (2, 4-D) is also measured and investigated. The well-preserved micropores and accessibility of MIL-101(Cr), endow the composite aerogels excellent absorption ability in water treatment and purification. When the mass loading of MIL-101(Cr) nanoparticles is 50%, the composite aerogels reach the large specific surface area of 356.91 m2·g−1. The composite aerogels demonstrate high adsorption ability towards for 2, 4-D (339.87 mg·g−1).

Improving high temperature properties of Cu-Cr-Y alloy by residual Cr particles and nano-Y2O3 dispersions

Advanced Cu-Cr alloys with high strength and thermal conductivity are promising heat dissipation materials but their applications are restricted to low and medium temperatures (<450 °C) due to the coarsening of Cr nanoparticles and grain recrystallization. In this study, a Cu-Cr-Y alloy strengthened by nano-Y2O3 dispersion (ODS Cu-Cr-Y alloy) was prepared by mechanical alloying using atomized Cu-Y alloy, Cr and Cu2O as Y source, microalloying element and oxidant material, respectively. The microstructure and high temperature (600 °C) properties of ODS Cu-Cr-Y alloy were investigated. It was found Y2O3 nanoparticles with ultrafine particle size (8.35 nm) and high number density (2.16 × 1023/m3) were distributed homogeneously in Cu matrix and residual Cr particles (50–100 nm) were formed on grain boundaries. The high temperature tensile strength and softening resistance of ODS Cu-Cr-Y alloy far exceeded that of traditional Cu-Cr alloys, which can be attributed to the thermodynamic stability of nano-Y2O3 dispersions and the inhibition of Cr nanoparticle growth by Y addition and residual Cr particles. The ODS Cu-Cr-Y alloy provides an optimal combination of strength and thermal conductivity at high temperature, showing great promises to be used as heat dissipation material under severe conditions like those in fusion plants and rocket engines.

Transport of polymer-coated metal–organic framework nanoparticles in porous media

Injecting fluids into deep underground geologic structures is a critical component to development of long-term strategies for managing greenhouse gas emissions and facilitating energy extraction operations. Recently, we reported that metal–organic frameworks are low-frequency, absorptive-acoustic metamaterial that may be injected into the subsurface to enhance geophysical monitoring tools used to track fluids and map complex structures. A key requirement for this nanotechnology deployment is transportability through porous geologic media without being retained by mineral-fluid interfaces. We used flow-through column studies to estimate transport and retention properties of five different polymer-coated MIL-101(Cr) nanoparticles (NP) in siliceous porous media. When negatively charged polystyrene sulfonate coated nanoparticles (NP-PSS-70K) were transported in 1 M NaCl, only about 8.4% of nanoparticles were retained in the column. Nanoparticles coated with polyethylenimine (NP-PD1) exhibited significant retention (> 50%), emphasizing the importance of complex nanoparticle-fluid-rock interactions for successful use of nanofluid technologies in the subsurface. Nanoparticle transport experiments revealed that nanoparticle surface characteristics play a critical role in nanoparticle colloidal stability and as well the transport.

NIR photoluminescence of ZnGa2O4:Cr nanoparticles synthesized by hydrothermal process

NIR photoluminescence of ZnGa2O4:Cr nanoparticles synthesized by hydrothermal process

Investigation of 3D flow of magnetized hybrid nanofluid with heat source/sink over a stretching sheet

The thermal processes with inclusion of nanomaterials provide a wide range of applications pertaining to heat exchangers and cooling of compact heat density devices. The current research investigates the three-dimension flow of hybrid nanofluid comprising TC4(Ti-6A-14V) and Nichrome 80% Ni and 20% Cr nanoparticles mixed within engine oil as the base fluid for the enhancement of heat and mass transfer rate. The effects of homogeneous-heterogeneous processes and thermal radiation are incorporated. The heat transfer occurs due to a rotating inclined stretched sheet is discussed against prominent factors such as thermal radiation, inclined angle parameter, rotation parameter, and heat source/sink. The leading mathematical formulation consists of a set of PDEs, which are then transmuted into ordinary differential equations using suitable similarity transformation. The numerical solutions are obtained by using MATLAB's built-in function bvp4c. The results for velocity profile, temperature profile and concentration distribution are evaluated for suitable ranges of the controlling parameters. The graphical result shows that when the angle of inclination, magnetic parameter, and the volumetric concentration of hybrid nanomaterials increase the axial flow profile of the hybrid nanofluid is reduced. However, the rotation parameter reveals the opposite response. The temperature is intensified with an increment of heat source/sink, shape factors, and magnetic field parameter. For enhanced nanoparticle volumetric concentration, the temperature of the fluid rises up. The graphical validation is also illustrated using streamlines and statistical plots for hybrid nanofluid.

Recyclable CMC/PVA/MIL-101 aerogels with tailored network and affinity sites for efficient heavy metal ions capture

A novel CMC/PVA/MIL-101(Cr) aerogel bead (CPMB) was prepared by the green polymer matrix of CMC and PVA and nanofiller of MIL-101(Cr) through the simple complexing with the ionic crosslinking agent, which could be an adsorptive platform for effectively capturing of Co(II) and Ni(II) ions in wastewater. The morphology, surface chemistry, and textural characteristics were investigated by varied characterization methods to reveal behind mechanisms for the dissimilarity in adsorption performance. The optimal modifying dosage of MIL-101(Cr) nanoparticles was determined to form an optimal tailored network with abundant MIL-101 clusters and hydroxyl/carboxyl groups inside the network that greatly achieved the most accessible heavy metals to CPMB-1. Meanwhile, the influences of temperature, adsorption dosage, pH, and interfering cations on the capacity of CPMB-1 were investigated, while adsorption behaviors of adsorbents were also explored. Analytic results indicated that the capture of two targeted ions by CPMB-1 could favorably comply with the Pseudo-second-order kinetic model and Freundlich isothermal adsorption model. The maximum adsorption capacities of two targeted ions calculated by data were 180.3 mg/g and 261.9 mg/g, respectively. According to the results of XPS and FTIR analysis, the electrostatic attraction and chelating effect could be the main mechanisms for improved performance, and contributing groups were the hydroxyl and carboxylic acid introduced into CPMB-1. Moreover, the as-designed CPMB-1 exhibited excellent recyclability and stability in eight cycles. The encouraging results exhibited by CPMB-1 might bring a new idea for integrating multiple functionalities of MOFs and biomass components for designing functional composites for efficient remediations of wastewater.

Green synthesis of Hesperitin dihydrochalcone glucoside by immobilized α-l-rhamnosidase biocatalysis based on Fe3O4/MIL-101(Cr) metal-organic framework

In this study, α-l-rhamnosidase was immobilized on magnetic Fe3O4/MIL-101 (Cr) nanoparticles using MIL-101(Cr) as precursor by crosslinking method. The crosslinking agent concentration ratio and crosslinking time were EDC/NHS 1:1 and 2 h, respectively. The immobilized materials were characterized by FT-IR, XRD, SEM and VSM. The saturation magnetization of the prepared magnetic nanoparticles was 46.2 emu/g. The optimum pH and temperature of immobilized enzyme were 6 and 60 °C. The application of immobilized enzyme in the preparation of hesperidin dihydrochalcone glucoside (HMGDC) by hydrolysis of hesperidin dihydrochalcone (HSDDC) was studied. The results showed that immobilized enzyme had better temperature resistance, repeatability and stability than free enzyme. The immobilized enzyme activity was 293.55 U/g, and the recovery was 116.03%. After treatment at 60 °C for 4 days, the enzyme activity remained at 24.6%. The conversion rate of HSDDC reached 93.1%.

Metal-organic aerogel derived hierarchical porous metal-carbon nanocomposites as efficient bifunctional electrocatalysts for overall water splitting

An efficient strategy to construct non-noble metal-base electrocatalysts for water splitting is the direct carbonization of metal–organic aerogel composites. Herein for the first time, a novel tube-like metal–carbon nanocomposite with encapsulated small-size individual Fe, Cr and Ni nanoparticles, is prepared by the carbonization of a FeCr-doped Ni-benzenetricarboxylate aerogel. The slender skeleton of the aerogel, supercritical drying and Cr doping alleviates metal aggregation and facilitates the in-situ growth of carbon tubes. This nanocomposite exhibits remarkably low overpotential of the hydrogen evolution reaction (137 mV) and oxygen evolution reaction (220 mV). Further, the cell voltage could be as low as 1.54 V with the current density of 10 mA cm−2 and illustrates excellent stability under a continuous operation for 50 h. This non-noble metal-base electrocatalyst is comparable to noble metal-based electrocatalysts and the impressive performance is ascribed to the abundant active catalytic sites and short reactant diffusion pathways. This work demonstrates great capability of aerogel derivation in the highly active electrocatalyst design for promising electrochemical applications.

Effect of Cr nanoparticle dispersions with various contents on the oxidation and phase transformation of alumina scale formation on Ni2Al3 coating

In this work, the NiCr nanocomposite films were fabricated with various contents of Cr nanoparticle dispersions and then subsequently aluminized to obtain the Cr nanoparticle-dispersed Ni2Al3 coating at temperature 620 °C. For comparison, the samples without Cr nanoparticle dispersions were prepared under the same experimental condition. The results showed that the Ni2Al3 coating with Cr nanoparticle dispersions has a lower oxidation rate than the Cr-free Ni2Al3 coating after oxidation. The result also indicates that Cr nanoparticle dispersions in the Ni2Al3 coating promoted the transformation of θ-into-α alumina phase and surface microstructure evolution based on the investigations of photo-stimulated luminescence spectroscopy (PSLS) and scanning electron microscopy (SEM), respectively. Furthermore, with increasing the content of Cr nanoparticle dispersions from 2.5 wt% to 5 wt% in the Ni2Al3 coatings can significantly reduce the oxidation rate through accelerated phase transformation of metastable to stable alumina. In addition, the Cr nanoparticles in Ni2Al3 not only mitigate the cavities formation at the interface, but also grow an adherent alumina scale on aluminide.

Interaction of norfloxacin and hexavalent chromium with ferrihydrite nanoparticles: Synergistic adsorption and antagonistic aggregation behavior

The co-existence of hexavalent chromium (Cr(VI)) and norfloxacin (NOR) can be detected in natural environments. However, the interaction of the co-existing Cr(VI), NOR and ferrihydrite nanoparticles (FNPs, a ubiquitous natural iron oxide nanoparticle) is lacking investigation. Figuring out this interaction could help us better predict the transport and fate of the relevant contaminants. Here, the adsorption and aggregation of FNPs in the presence of Cr(VI) and NOR were investigated. Comparing to FNPs interaction with Cr(VI) or NOR alone, the co-existence of Cr(VI) and NOR could lead to a synergistic effect to increase their adsorption onto FNPs. This observation can be attributed to the complexation between Cr(VI) and carboxyl or amino groups from NOR. Furthermore, the aggregation of FNPs could be accelerated by Cr(VI) through charge neutralization since the adsorption of Cr(VI) could decrease the surface potential of FNPs (positive charge). However, the presence of NOR will increase the surface charge, and thus stabilize FNPs. In general, the aggregation state of FNPs in the presence of co-existing Cr(VI) and NOR depends on their ratio. Overall, these understandings help us predict the transport and fate of FNPs and the associated contaminants in natural environments.

Mn, Cu and Cr nanoparticles in Li2B4O7 glass: Radiation shielding and optical properties

Lithium tetraborate (Li2B4O7) glass matrices doped with Manganese (Mn), Copper (Cu) and Chromium (Cr) were synthesized, using the melt-quenching method. Radiation shielding and optical parameters are studied in this work. High-resolution Transmission Electron Microscopy confirms formation of Mn, Cu and Cr nanoparticles in the samples. Absorption spectra of the samples show the characteristic surface-plasmon bands of these transition-metals nanoparticles. Their bandgaps were calculated from the absorption spectra. The fluorescence bands of each transition-metal nanoparticle ensembles in the tetraborate glass matrices are identified by recording the fluorescence spectrum. Emission spectra under 405 nm pumping show bands with a peak at 591 nm from nanoparticles of Mn, a peak at 750 nm of Cu, and a peak at 735 nm of Cr. The fluorescence lifetimes are measured, and the stimulated emission and absorption cross-section are calculated. The theoretical values of radiation shielding parameters mass attenuation coefficient (MAC), half value layer (HVL), tenth value layer (TVL), mean free path (MFP) and effective atomic number (Zeff) were calculated for the glass samples to analyze which sample has the best radiation shielding response. It should be noted that the samples made in this work present a better response than high-performance heavyweight concrete mixes using the coarse aggregates of magnetite.

Photoresponse enhancement in TiO2 thin films by incorporation Ni and Cr nanoparticles using sol–gel method

Photoresponse enhancement in TiO2 thin films by incorporation Ni and Cr nanoparticles using sol–gel method