Cr Nanoparticle Research Articles

Chromium Metal Nanoparticles, Their Reactivity and Reactions

AbstractZerovalent chromium nanoparticles (2.2±0.2 nm in size) are prepared in the liquid phase (THF) by reduction of CrCl2 with lithium naphthalenide ([LiNaph]). The deep black Cr(0) nanoparticle suspensions in THF are colloidally and chemically highly stable. On the other hand, the Cr(0) nanoparticles are highly reactive, e. g., when in contact to O2, H2O, or other oxidizing agents. To probe the reactivity of the Cr(0) nanoparticles in the liquid phase near room temperature (50–80 °C), they are reacted with different coordinatively demanding, N−H, S−H or O−H acidic reactants. This includes the amines 2,2′‐dipyridylamine (HDPA), 2‐(1H‐imidazol‐2‐yl)pyridine (HImPy) and carbazole (HCbz), the thiol 2‐mercaptopyridine (HMPy), and benzoic acid (HBz) as a carboxylate. As a result, the five novel compounds [Cr(DPA)3], [Cr(ImPy)3] ⋅ HImPy, [Cr(MPy)3] ⋅ 0.5 Tol (Tol: toluene), [Na2Cr(Cbz)4(THF)3], and [Cr2(Bz)4(THF)2] are obtained. [Cr(DPA)3] and [Cr(ImPy)3] ⋅ HImPy show Cr(III) coordinated by nitrogen only; [Cr(MPy)3] ⋅ 0.5 Tol shows a coordination of Cr(III) by both N and S atoms. [Na2Cr(Cbz)4(THF)3] and [Cr2(Bz)4(THF)2] contain Cr(II) and exhibit an infinite chain‐like structure and pairs of chromium atoms with fourfold binding.

Enhancing Stability of Tannic Acid-FeIII Nanofiltration Membrane for Water Treatment: Intercoordination by Metal-Organic Framework.

Tannic acid (TA)-FeIII nanofiltration (NF) membrane has been demonstrated to possess more favorable removal of trace organic contaminants (TrOCs) over the conventional polyamide NF membrane. However, the drawback of acid instability severely hinders the practical application of TA-FeIII NF membrane in the treatment of (weak) acidic wastewater containing TrOCs (e.g., pharmaceutical wastewater, surface water, and drinking water). Herein, we introduced the MIL-101(Cr) nanoparticle, a kind of metal-organic framework (MOF), into the TA-FeIII selective layer to enhance the membrane acid stability. The acid-tolerance parameter of MIL-101(Cr)-stabilized TA-FeIII membrane (TA-FeIII-MOF membrane, 12,000 ppm/s-1) was two orders of magnitude larger than that of the TA-FeIII membrane (50 ppm/s-1), and the TA-FeIII-MOF membrane can withstand acid treatment at pH = 4 for more than 30 days. Meanwhile, the TA-FeIII-MOF membrane displayed increased water permeance from 9.5 to 12.7 L/(m2·h·bar) after the MOF addition, without compromising the selectivity. The enhanced acid stability for the TA-FeIII-MOF membrane was ascribed to an intercoordination mechanism, where FeIII centers (from TA-FeIII complex) coordinated with -COOH groups (from terephthalic acid of MOF) and CrIII centers (from MOF) coordinated with -OH groups (from TA of TA-FeIII complex), which was verified by the density functional theory calculation. This study highlights a new approach for the development of a TA-FeIII-based NF membrane with markedly enhanced acid stability, which is important for its real application in wastewater treatment and water reuse.

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.

Zwitterionic metal-organic frameworks modified polyamide membranes with enhanced water flux and antifouling capacity

Antifouling properties are considered to be crucial parameter to polyamide (PA) composite nanofiltration (NF) membranes for practical applications. In this study, an antifouling material, surface zwitterionization of Metal-organic frameworks (Z-MIL-101 (Cr)) was firstly prepared by decorating zwitterionic polymer onto the MOFs surface. Subsequently, a novel type of MOFs-based hybrid membranes were fabricated via mixing the Z-MIL-101 (Cr) nanoparticle with the organic matrix by interfacial polymerization technique. The most optimal hybrid membrane had a high water permeation of 26 L m−2 h−1 bar−1, which was 2.1 times higher than that pristine PA membrane, while the retention for Na2SO4 was still kept at a considerably high value of 93%. The significant increased water flue can attribute to the existence of water channels generated by the Z-MIL-101 (Cr). More important, the antifouling property of the hybrid membrane was much better than that pristine PA, which was due to the formation of superhydrophilic liquid layer surrounding the zwitterionic groups. The combination of the micropore structure of the MOFs and the excellent antifouling properties of the decorated zwitterionic polymer effectively improved separation performances and antifouling ability, which makes these hybrid membranes promising for water purification.

Fabrication of magnetic Au/Fe3O4/MIL-101(Cr) (AF-MIL) as sensitive surface-enhanced Raman spectroscopy (SERS) platform for trace detection of antibiotics residue

Fabrication of a magnetic substrate based on metal–organic frameworks (MOFs) with high sensitivity and stability for surface-enhanced Raman scattering (SERS) analysis were reported in this paper. MIL-101(Cr) nanoparticle prepared via a traditional hydrothermal reaction, which was combined with Fe3O4 to synthesize the Fe3O4/MIL-101(Cr) composites. Then, the concentration of chloroauric acid and the time of reduction reaction were adjusted to acquire the optimal Au/Fe3O4/MIL-101(Cr) (AF-MIL) SERS substrate. The detection ability of the substrate can down to 10-8 mol/L for Rhodamine 6G (R6G) as probe molecule, and the relative standard deviation (RSD) is only about 4.48 %, which indicates that it possesses wonderful SERS performance and uniformity. Finally, the as-synthesized substrate has been adopted to test the trace level sulfapyridine, with its desirable detection ability can down to 10-6 mol/L. Such desirable SERS substrate with facile and effective operation holds great promise in the fast sensitive detection of the antibiotic residue and some other pollutants in environment.

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.

Super-resolution imaging of plasmonic nanostructures by microsphere-assisted microscopy.

We fabricate both triangularly and circularly shaped Au, Ag, and Cr nanoparticle arrays and observe the imaging properties of these plasmonic nanostructures by BaTiO3 glass (BTG) microsphere-assisted microscopy. We experimentally find that the resolution of triangularly shaped Ag nanoparticle arrays is higher than that of Au and Cr ones, and a gap resolution of ∼λ/7.7 is demonstrated for the circularly shaped Au, Ag, and Cr nanostructures. Numerical simulations show that when a fully immersed BTG microsphere is dispersed on the surface of a plasmonic nanostructure sample, an enhanced electric field is generated in the vicinity of the sample, especially at the gap of the microsphere and the sample, due to the focusing effect of the microsphere and the excitation of localized surface plasmon resonance in the plasmonic nanostructure. The enhanced electric field in Ag nanostructures is significantly stronger than that in Au and Cr ones. Besides, the microsphere collects, amplifies, and propagates the enhanced near-field information to the far field, resulting in the improvement of imaging resolution.

Graphene-wrapped microspheres decorated with nanoparticles as efficient cathode material for lithium-sulfur battery

• Graphene-wrapped microspheres decorated with metal nanoparticles was developed. • Cr-Ni-NDs@G is an efficient multifunctional sulfur host material for Li-S batteries. • The interaction and conversion kinetic of lithium polysulfide were studied. • The sulfur cathode exhibits high specific capacity and cycling performance. Lithium-sulfur (Li-S) battery is now a promising technology for energy storage. However, the commercialization of Li-S battery was hindered by the shuttle effect of lithium polysulfide and the slow reaction kinetics of sulfur. In this study, MIL-101(Cr) with graphene oxide was composited together through spray-drying. Then, a graphene microsphere composite consisted of three-dimensional conductive network decorated with Cr-Ni-based nanodots (Cr-Ni-NDs) was developed through a facile heat treatment. The microsphere composite was denoted as Cr-Ni-NDs@G, which offers a porous structure and high surface area to increase the accommodation and uniform distribution of sulfur in the cathode. Meanwhile, the three-dimensional conductive network embedded by Cr and Ni nanoparticle not only improved the transportation of electrons, but also act as the active site strengthening the adsorption of lithium polysulfide, promoting the catalytic transformation of lithium polysulfide to Li 2 S. Due to these complementary features, the S/Cr-Ni-NDs@G cathode exhibited a high initial specific capacity (1222.3 mAh·g −1 at 0.2C) and good rate performance (706 mAh·g −1 at 3.0C). In addition, after 500cycles at 1.0C, the faded rate of per cycle of the Li-S battery is only 0.059%. The result demonstrated that S/Cr-Ni-NDs@G composite can be a promising energy storage material in the development of Li-S batteries.

Acute oral toxicity and repeated dose 28-day oral toxicity studies of MIL-101 nanoparticles

Metal-organic frameworks (MOFs) nanoparticles are a class of porous crystalline materials constructed from the bonding metal ions or clusters linked with organic ligands to form frameworks. MIL-101(Cr), one of the most representative MOFs, is a three-dimensional chromium terephthalate-base porous material consisted of chromium (III)-trimers cross-linked by 1,4-benzene dicarboxylate. The present study focused on determining the safety of MIL-101(Cr) nanoparticle. The acute oral toxicity and 28-day oral toxicity in mice were investigated. An acute oral toxicity test of MIL-101(Cr) nanoparticle for female mice showed that no mortality or any significant change observed at 2000 mg/kg body weight. A dose-dependent 28-day oral toxicity evaluation of MIL-101(Cr) nanoparticle for male and female mice revealed no significant effects on mortality, feed consumption, body weight, organ weight, and behavior. Assessments of hematology, clinical biochemistry, and histopathology revealed no adverse effects in mice treated with MIL-101(Cr) nanoparticle (10–1000 mg/kg). These results suggest that MIL-101(Cr) nanoparticle has no significant acute and subacute toxicity. The no observed adverse effect level of MIL-101(Cr) nanoparticle was defined as at least 1000 mg/kg/day orally for 28 days for male and female mice.

Using precipitated Cr on the surface of Cu-Cr alloy powders as catalyst synthesizing CNTs/Cu composite powders by water-assisted CVD

Given that the conventional catalyst is easily soluble in the matrix to result in the poor performance of the CNTs/Cu composite materials, the Cr nano-particles precipitated on the surface of Cu-Cr particles are first used as catalysts to prepare the CNTs/Cu composite powders by means of water-assisted chemical vapor deposition in situ synthesis. The results show that the morphological difference of the precipitated Cr nano-particle is obvious with the change of solution and aging treatment, and the morphology, length and diameter of the synthetic CNTs are also different. The catalyst of Cr nano-particle has the best morphology and the synthesized CNTs had a good wettability with Cu particles when the Cu-Cr composite powders was solution-treated at 1023 K for 60 min and then was aged at 723 K for 120 min. The length, diameter, yield and purity of the synthesized CNTs can be also affected by the moisture content in the reaction gas. It is the most suitable for the growth of CNTs when the moisture content is 0.4%, and the high purity and defect-free CNTs with the smooth pipe wall, a diameter of 20 ∼ 30 nm and a length of up to 1800 nm can be obtained. The yield of CNTs with the moisture content of 0.4% reached to 138%, which was increased by 119% to compare with that without moisture. In this paper, a feasible technology was offered for the preparation of high performance CNTs/Cu composites.

Improvement in Cr Nanoparticle Content in Ni–Cr Film by Co-deposition with Combined Surfactant HPB and CTAB

The effects of single surfactant hexadecylpyridinium bromide (HPB) and cetyltrimethylammonium bromide (CTAB) and the combination of HPB and CTAB on the Cr nanoparticle content in the Ni–Cr film prepared by co-deposition were investigated. Single HPB/CTAB addition inhibited the oxidation and amorphous transformation of the Cr nanoparticles in the plating bath and effectively stabilized the Cr nanoparticles content at approximately 10 mass% as a function of time. Moreover, the combination of HPB and CTAB formed a cylindrical micelle structure on the Cr nanoparticle surface, which prompted the formation of a layer of NiCr2O4. As a result, the Cr nanoparticle content increased sharply to 20 mass%.

Biosynthesis of Cr(III) nanoparticles from electroplating wastewater using chromium-resistant Bacillus subtilis and its cytotoxicity and antibacterial activity

The aim of this study was to synthesize and characterize Cr(III) nanoparticles using wastewater from electroplating industries and chromium-resistant Bacillus subtilis. Formation of Cr(III) nanoparticles was confirmed by UV–visible (UV–Vis) spectroscopy at 300 nm. The size of the nanoparticles varied from 4 to 50 nm and energy dispersive spectroscopy profile shows strong Cr peak approximately at 4.45 and 5.2 keV. The nanoparticles inhibited the growth of pathogenic bacteria Staphylococcus aureus and Escherichia coli. The cytotoxic effect of the synthesized Cr(III) nanoparticle was studied using HEK 293 cells, and the cell viability was found to decrease with increasing concentration of Cr(III) nanoparticles.

Electronic structure of chromium-containing amorphous hydrogenated carbon thin films studied by X-ray absorption spectroscopy

C K-, Cr L3.2-, and K-edge X-ray absorption near-edge structure (XANES) analysis, high-resolution transmission electron microscopy examination, and optical absorptance have been examined to obtain a correlation between the optical absorptance and electronic structure of chromium-containing amorphous hydrogenated carbon thin films (a-C:H/Cr) deposited using a dc magnetron sputter deposition technique. It was found that the C 2pCr 3d hybridization gradually increases as the Cr nanoparticle (NP) size decreases, accompanied by a C 2p interband transition. The amount of CH bonding and the change in crystalline structure are the main factors affecting the optical absorptance of the thin films. The size of the Cr NP affects the absorption wavelength range of the films. The optical absorptance and C K-edge XANES spectra indicate that a decrease in the size of Cr NP raises the conduction-band-minimum and may also increase the bandgap.

Surface morphology and transport properties of Cr nanoparticles in single electron tunneling regime

We have carried out an investigation of surface structures of Cr nanoparticles grown on a MgO layer for studying single electron tunneling (SET). Reflection high-energy electron diffraction pattern changes from spotty to streak with decreasing Cr nominal thickness, while Cr forms nano size particles with the size of around 3.5 nm in diameter for all the samples. The double tunnel junctions for the Cr nominal thickness of 0.1 nm show clear Coulomb blockade with the threshold voltage of 50 mV, indicating that this Cr nanoparticle satisfies the condition for the appearance of SET. The relatively large volume of the Cr nanoparticles may be related with the fact that tunnel magnetoresistance due to spin accumulation in Cr nanoparticles is small.

Nitric oxide gas sensing at room temperature by functionalized single zinc oxide nanowire

We report on room temperature detection of nitric oxide (NO) gas at low-ppm level by Cr nanoparticle decorated single zinc oxide nanowire (ZNW) sensor. In this sensor device Cr nanoparticles, act as catalyst to transform NO into NO2 and results in change in current value through ZNW, corresponding to NO gas concentration. The sensor exhibits average sensitivity of ∼46% for 10 ppm of NO gas. The lowest detection limit of the sensor is ∼1.5 ppm for NO gas. Sensor shows selectivity towards NO gas during a cross-sensitivity test with N2, CO and CO2 gases. Recovery of the sensor is achieved by ultraviolet light induced desorption of gases from ZNW surface.

Fabrication and wear properties of co-deposited Ni-Cr nanocomposite coatings

Ni-Cr nanocomposite coatings with different Cr particles contents were developed by electrodeposition method from a nickel sulfate solution containing different concentrations of Cr nanoparticle with an average particle size of 40 nm. The characteristics of the coatings were assessed by scanning electron microscopy and microhardness test. The friction and wear performances of Ni-Cr nanocomposite coatings and pure Ni film were comparatively investigated, with the effect of the Cr content on the friction and wear behaviors to be emphasized. The results indicate the microhardness, friction and wear behaviors of Ni-Cr nanocomposite coatings are closely related with Cr particles content. The Ni-Cr nanocomposite coating with a lower Cr content of 4.0% shows somewhat increased microhardness and wear resistance than the pure Ni coating, while the Ni-Cr nanocomposite coating with a higher Cr content has much better wear resistance than the pure Ni coating. The effect of Cr nanoparticles on the microhardness and wear resistance was discussed.

Magnetic behaviour of Fe–Cr nanoparticle systems

The low-temperature magnetic properties of Fe 1− x Cr x nanoparticles with various chromium content ( x=2.4−83.0 at%) have been studied. The multiphase particles (α-FeCr, σ-FeCr and Fe/Cr oxides) have a core (metallic)–shell (oxide) structure. The magnetic properties of the Fe–Cr systems depend on the chromium content as well as on the types and relative contributions of the constituent crystalline phases but, in particular, they are determined by long-range interparticle dipolar interactions. The role of the weakly magnetic σ-FeCr phase is also discussed.

Effects of chromium nanoparticle dosage on growth, body composition, serum hormones and tissue chromium in Sprague-Dawley rats

This 6-week study was conducted to evaluate the effects of seven different levels of dietary chromium (Cr) (0, 75, 150, 300, 450, 600, and 1 200 ppb Cr) in the form of Cr nanoparticle (CrNano) on growth, body composition, serum hormones and tissue Cr in Sprague-Dawley (SD) rats. Seventy male SD rats (average initial body weight of (83.2+/-4.4) g) were randomly assigned to seven dietary treatments (n=10). At the end of the trial, body composition was assessed via dual energy X-ray absorptiometry (DEXA). All rats were then sacrificed to collect samples of blood, organs and tissues for determination of serum hormones and tissue Cr contents. The results indicated that lean body mass was significantly increased (P<0.05) due to the addition of 300 and 450 ppb Cr from CrNano. Supplementation of 150, 300, 450, and 600 ppb Cr decreased (P<0.05) percent body fat significantly. Average daily gain was increased (P<0.05) by addition of 75, 150, and 300 ppb Cr and feed efficiency was increased (P<0.05) by supplementation of 75, 300, and 450 ppb Cr. Addition of 300 and 450 ppb Cr decreased (P<0.05) the insulin level in serum greatly. Cr contents in liver and kidney were greatly increased (P<0.05) by the addition of Cr as CrNano in the dosage of from 150 ppb to 1 200 ppb. In addition, Supplementation of 300, 450, and 600 ppb Cr significantly increased (P<0.05) Cr content in the hind leg muscle. These results suggest that supplemental CrNano has beneficial effects on growth performance and body composition, and increases tissue Cr concentration in selected muscles.

Morphological alteration upon phase transition and effects of oxygen impurities of chromium nanoparticles

The morphological alteration from δ - to α -Cr nanoparticles and the phase transition temperature were directly observed by in situ experiment using a transmission electron microscope. The icositetrahedral nanoparticle of δ -Cr transformed into a rhombic dodecahedral nanoparticle of α -Cr upon heating at 550 ∘ C . It was demonstrated that the most stable shape of the α -Cr nanoparticle is the rhombic dodecahedron. Upon heating the α -Cr nanoparticle at 650 ∘ C , the (1 1 3) layer of Cr 2 O 3 grew topotactically in the direction of [ 1 0 0 ] of α -Cr nanoparticle. We concluded that the α -Cr nanoparticle includes about 20–30 at% oxygen, as estimated from the volume of the Cr 2 O 3 surface layer.