Presence Of Cr3 Research Articles

The role of thermal treatment and formulation on modifying the structural nature and optimizing certain physical features of coprecipitated superparamagnetic Co–Mn–Cr spinel ferrite

Examining the composition and heat treatment effects of co-precipitated Co0.7Mn0.3CrxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1) ferrite nanoparticles provides valuable insights into the structural, morphological, optical, magnetic, and electrical properties of these materials. X-ray diffraction (XRD) and Rietveld refinement analyses confirm the spinel cubic crystalline phase of the samples, indicating the formation of well-defined crystal structures. Transmission electron microscope micrographs manifest the nanoscale nature of the produced specimens and their narrow particle size distribution with a small standard deviation. This uniformity is often desirable in many applications because it confirms the similarity of the properties and behaviors of the nanoparticles. The Fourier transform infrared spectroscopy study suggests that the substitution of Cr3+ ions at octahedral sites influences molecular stability. Annealing causes a slight expansion in bond length and a subsequent decrease in stability. The presence of Cr3+ ions enhances the strength of the specimens, while annealing weakens them. This indicates a fine balance between composition and processing conditions in determining the strength of the materials. The estimated optical indirect bandgap undergoes a redshift by adding Cr3+ ions. Annealing at elevated temperatures reduces the bandgap due to the quantum confinement effect, indicating the tunability of optical properties through compositional and thermal control. Samples with x ≥ 0.6 exhibit nearly zero coercivity, indicating superparamagnetic behavior, which have promising applications. The preference of Cr3+ ions to occupy octahedral B-sites influences the magnetic behavior of the materials. The dielectric polarization and dielectric loss improved by adding Cr3+ ions, while the alternating current conductivity decreased. From impedance spectroscopy, the real and imaginary parts, Z’ and Z”, were increased by increasing Cr content. Furthermore, the annealing process greatly affects the electrical properties of the specimens. Overall, the study emphasizes the intricate relationship between composition, annealing conditions, and the resulting structural, magnetic, and electrical properties of Co–Mn–Cr ferrite nanoparticles, providing significant observations for the development of tailored materials for diverse applications in electronics, magnetics, and medicine.

Chromogenic recognition of Cr(III) and Cu(II) using a novel Schiff base and “turn-on” fluorescent detection of CO32− by its reduced scaffold in aqueous media

An upsurge of severe toxic inorganic ionic species in water arising due to anthropogenic activities, has caused global concern and detection of such harmful contaminants is a matter of supreme importance. In this regard, a novel trans-1,2-diaminocyclohexane containing Schiff base N,N′-di(4-acetamidophenylmethylene)-1,2-cyclohexanediamine (1) and its reduced scaffold N,N’-di(4-acetamidophenylmethyl)-1,2-cyclohexanediamine (2) have been synthesized and characterized by FT-IR and 1H & 13C NMR while the structures of both 1 and 2 have been determined by X-ray single crystal diffraction analysis. The detection response of 1 and 2 have been investigated toward same set of analytes and found to be entirely different both in absorption and emission studies. Compound 1 selectively and very sensitively detects Cr3+ and Cu2+via hydrolytic rupture of >C = N- bond as indicated by ratiometric change and emergence of an isosbestic point in UV–vis analysis. Further, the kinetic studies clearly suggested rapid hydrolysis of 1 (< 3.0 mins) in the presence of Cr3+ whereas it requires ∼1.0 h for complete hydrolysis with Cu2+. In contrast, the recognition of Cr3+ and Cu2+ not be observed through fluorescence technique. Moreover, 2 remains silent toward Cr3+/Cu2+in UV–vis analysis, however, it selectively recognizes CO32− through ‘turn-on’ fluorescence output in the background presence of several tested cations and anions. Job's plot and mass analysis suggested 1:2 (CO32−: 2) binding stoichiometry between CO32− and 2. Remarkably, the present findings demonstrate entirely different functionality of a Schiff base and its reduced form in presence of same analytes. The main objective of this report is to illustrate that how a subtle structural change of a molecule governs the analyte detection ability.

Selective colorimetric detection of trace chromium (III) based on silver nanoparticles aggregation via a domino-like reaction

A simple method for measuring and tracking Cr3+, particularly in water, are crucial for environmental protection and avoiding serious health implications. Herein, we report the synthesis of mannose functionalized silver nanoparticles (Ag@mannose NPs) for naked eye detection of Cr3+ ions. The Cr3+-induced selective stimuli on the surface of Ag@mannose NPs promote aggregation, resulting in a colour change from yellow to purple, which can be assessed by absorption spectroscopy. Zeta potential investigation revealed that the surface charge of Ag@mannose NPs was altered in the presence of Cr3+, resulting in aggregation, as validated by dynamic light scattering and transmission electron microscopy. Cyclic voltammetry study shows that the NPs surface stabilized with mannose was oxidized in the presence of Cr3+, causing a domino-like effect that resulted in NPs aggregation and colour change. The interference study demonstrated the selectivity and sensitivity of Ag@mannose NPs to Cr3+ over other metal ions. Ag@mannose NPs can detect Cr3+ in a wide pH range of 3–9. The lowest Cr3+ concentration detected by the naked eye is 0.6 μM (39 μg/L), under the World Health Organization permissible limit of chromium (50 μg/L) in drinking water. Finally, the Ag@mannose NPs sensing ability was demonstrated by detecting Cr3+ in tap and sewage water with a good recovery percentage.

Electron irradiation effects on the optical properties of Hf- and Zn-doped β-Ga2O3

Optical and electrical properties of Hf- and Zn-doped β-Ga2O3 samples, which are n-type and insulating, respectively, were altered via high-energy electron irradiation at 2.5 or 0.5 MeV. The β-Ga2O3:Hf samples irradiated with 2.5 MeV electrons experienced a color change from blue to yellow and a large drop in conductivity, attributed to the creation of gallium vacancies, which compensate donors. This irradiation resulted in the absence of free carrier absorption and the presence of Cr3+ photoluminescence (PL). PL mapping prior to irradiation revealed optically active ZnO precipitates that formed during the growth of β-Ga2O3:Zn. These precipitates have a 384 nm (3.23 eV) stacking fault emission in the core; in the outer shell of the precipitate, the PL blue-shifts to 377 nm (3.29 eV) and a broad defect band is observed. After 0.5 MeV electron irradiation, the defect band broadened and increased in intensity. The blue PL band (435 nm) of β-Ga2O3 was enhanced for both Hf- and Zn-doped samples irradiated with 0.5 MeV. This enhancement is correlated with an increase in oxygen vacancies.

New insights into the performance and durability degradation mechanisms of PEMFCs caused by Cr3+ contaminant

It is known that contamination ions stemming from the corrosive deterioration of vital subassemblies, such as bipolar plates (BPs) and sealing gaskets, exert a profound influence on the performance and durability degradation of PEM fuel cells. The impacts of Cr3+ on the catalyst layers (CLs) and single-cell performance were investigated by immersing the cathode catalyst layer (CCL) and anode catalyst layer (ACL) in a Cr3+ solution with different concentrations for contamination treatment. During the fuel cell test, polarization curves (PCs), electrochemical impedance spectroscopy (EIS), H+ transfer impedance, and cyclic voltammetry (CV) curve results were recorded. The effects of Cr3+ contamination on the kinetic for oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) were analyzed in a three-electrode system. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to explore the degradation mechanisms of Cr3+ contamination on fuel cell activity. The results indicate that the presence of Cr3+ increased the ohmic impedance from 0.200 Ω cm2 to 0.449 Ω cm2, resulting in a voltage attenuation rate as high as 55.21 %. Moreover, the presence of Cr3+ slowed the ORR reaction rate and changed the ORR reaction pathway. Cr3+ contamination caused irreversible damage to PEMFC performance and durability.

Competitive Effect of Zinc and Cadmium on the Biosorption of Chromium by Orange Waste

Batch experiments were conducted to test orange waste (OW), an agricultural solid waste byproduct from the orange juice manufacturing industry, as adsorbent for binary solutions of Cd2+-Cr3+ and Zn2+-Cr3+. Fourier transform infrared spectroscopy (FTIR) and the point of zero charge (pHpzc) were used to identify the functional groups on the OW surface involved in biosorption. The biosorption equilibrium data for both binary-metal solutions were obtained and fitted to various isotherm models. The extended Sips and the non-modified Redlich-Peterson isotherm models gave the best fit for the experimental data. According to the extended Sips model, the maximum biosorption capacity of OW was 0.573 mmol·g−1 for Cd2+, 0.453 mmol·g−1 for Zn2+, and 1.96 mmol·g−1 for Cr3+. The sorption capacity dropped to 0.061 mmol·g−1 for Cd2+ and to 0.101 mmol·g1 for Zn2+ in their binary systems with Cr3+ for the higher initial metal concentrations in the solution. However, the maximum sorption capacity of chromium was only slightly affected by the presence of Cd2+ or Zn2+. For both binary systems, the presence of a second metal ion in the solution always conduces to a reduction in the sorption of the other metal in the solution. The presence of Cr3+ decreased the sorption of Cd2+ and Zn2+ more than vice versa. Conclusively, effective removal of Cr3+ ions from an aqueous solution can still be achieved in the presence of Cd2+ or Zn2+.

Chromium activated Ca9Al (PO4)7 nanophosphors: synthesis, morphology and dosimetry characteristics

In this article, a sol–gel route was employed to prepare nanophosphor materials including Ca9−x CrxAl (PO4)7 series (where 0.05 ≤ x ≤ 0.5 (mol%)). All subseries were irradiated to a γ- test dose of 5 Gy and the thermoluminescence (TL) response of Cr-activated (0.1 mol%) Ca9Al (PO4)7 sample has the best TL response and was chosen for investigations. The phase, particle size, surface morphology, and elemental mapping of the chosen sample Cr0.1 in comparison with other ones (Cr0.05 and Cr0.5) were scrutinized using x-ray diffraction (XRD), transmission electron microscope (TEM), SEM-EDX mapping, and XPS techniques. XRD profiles showed that all diffraction peaks assigned to the trigonal R 3 c space group and the average of particle sizes obtained by the modified Scherer method and TEM data are closely related. The presence of Cr3+ ions in the Ca9Al (PO4)7 lattice was assured by XPS spectra. Cr0.1 chosen sample was studied after irradiation to different γ-doses and displayed a prominent glow curve at 205 °C ± 3.97 °C. It showed a linear dose–response curve from 200 mGy up to 10 Gy with fading of 24% upon 24 h and almost no significant signal loss for further interval times. The average Zeff value was ∼11 at both 662 and 1250 keV energies making this sample a bone-equivalent material (11.3–11.8). Values of activation energies (eV) calculated by different methods were comparable. Results the dosimetric properties of that the Cr0.1 sample can be surely considered as an additional recommended detector as other available ones in marketing.

A New Efficient Deep-Red-Emission Phosphor Y3Al4.9Sb0.1O12: Ce3+, Cr3+ with Application Potential in Plant Growth

Aiming at a system of more efficient plant growth, cationic substitutions for garnet-structure host crystal activated by Ce3+ and Cr3+ are investigated. A series of Y3Al5O12: Ce3+-Cr3+, red-emitting materials excited by near-ultraviolet and blue light with a peak emission near 693 nm, are synthesized using a solid-state method. The substitution of Sb3+ for Y3Al5O12: Ce3+, Cr3+ is found to increase the emission intensity of deep red about +80% because it improves the energy transfer from Ce3+ to Cr3+, where yellow emission of Ce3+ is depressed and deep red of Cr3+ increased. It also enhances the intensity-ratio of zero phonon line (ZPL) vs phonon assisted side band. It is induced that the substitution of Sb3+ having strong covalent property influences symmetric Ce3+O2– 6 octahedron, significantly increasing the intensity of 2E→4A2 ZPL of Cr3+ under the resonance energy transfer of Ce3+ to Cr3+. From the ratio of Ce3+ emission intensity in the absence and presence of Cr3+, the energy transfer has a mechanism of dipole-quadrupole interaction. By using Sb3+ substitution and flux AlF3, the original emission intensity of Y3Al5O12: Ce3+, Cr3+ is increased about +183%. The new phosphor has application potential for plant growth in both methods of using LED and converting Sunlight.

The extraction and the removal of Cd(II) using polymer inclusion membrane containing symmetric room temperature ionic liquid as ion carrier

Since cadmium is a hazardous material for environment, various techniques have been developed for safe removal of cadmium. Among these techniques, ionic polymer inclusion membranes (IPIMs) have a higher membrane structural stability that can be used to separate and recover cadmium ions with a higher selectivity. Also, the ion transport capacity of IPIMs can be further increased by selecting suitable ion carriers and plasticizers. In this study, preparation of IPIMs was accomplished by selecting newly synthesized symmetric and having different alkyl chain room temperature ionic liquids as ion carriers for selective the separation of cadmium from iodide-containing acidic solutions. The highest mass transport was determined as 0.958 μmol s−1 cm−2 from 25 mg L−1 and 2.02 μmol s−1 m−2 from 75 mg L−1 Cd(II) solution, respectively, when using the optimized IPIM containing 24.97% (w/w) 2-nitrophenyl octyl ether as plasticizer and 35.12% (w/w) 1,3-decyl-1 H-imidazol-3-ium bromide as carrier. The mass transport of cadmium was determined as 0.567 μmol s−1 m−2 in the presence of Cr3+, Fe2+, Co2+, Ni2+ and Zn2+. Surface analyses were explored by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), while the structural analysis was carried on by Fourier infrared spectroscopy (FTIR) before/after Cd transport experiments.

Continuous Ultra‐Broadband Near‐Infrared Sc2O3‐Based Nanophosphor Realized by Spectral Bridge of Cr3+‐Yb3+‐Cr4+ for Multiple Optical Applications

AbstractCr3+‐activated near‐infrared (NIR) phosphors are one of the most influential candidates for the new generation of intelligent NIR phosphor‐converted light‐emitting diode (pc‐LED) light sources. For spectral analysis, the broader the spectrum, the more useful information it contains. Herein, ultra‐broadband Cr‐activated Sc2O3 nanophosphors, which exhibit NIR ultra‐broadband from 650 to 1600 nm, are developed by the sol–gel method. This ultra‐broadband emission originates from the presence of Cr3+ and Cr4+, two luminescent centers confirmed by diffuse reflection spectra, electron paramagnetic resonance, time‐resolved photoluminescence spectra, and temperature‐dependent emission spectra. The nanophosphor exhibits excellent temperature‐sensing performance with SA = 4.102% K−1 and SR = 1.855% K−1. Co‐doping Yb3+ into Sc2O3 nanophosphors builds the Cr3+‐Yb3+‐Cr4+ model to bridge the spectral gap located at 1000 nm, forming a continuous NIR ultra‐broadband spectrum ranging from 650 to 1600 nm for the first time. Moreover, the introduction of Yb3+ improves the thermal stability of nanophosphors from 29.49% to 50.65% at 150 °C. The NIR transmission spectra of water, ethanol, and peanut oil demonstrate that Sc2O3:Cr3+‐Yb3+‐Cr4+ NIR nanophosphors favor potential applications in spectral analysis. The construction of a Cr3+‐Yb3+‐Cr4+ spectral bridge for realizing NIR ultra‐broadband phosphors based on cheap blue LEDs provides novel and effective insights.

Volatile Species Generation for Trace Element and Speciation Analysis – Current State and Future Perspectives

Volatile Species Generation for Trace Element and Speciation Analysis – Current State and Future Perspectives

Forced hydrolysis of FeCl3 solutions in the presence of Cr3+ ions and hexamethylenetetramine

Forced hydrolysis of FeCl3 solutions in the presence of Cr3+ ions and hexamethylenetetramine

Smartphone-assisted colorimetric biosensor for on-site detection of Cr3+ ion analysis

A simple and low-cost biosensor has been established for the detection of Cr3+ ion by using the image processing function of the smartphone. In the presence of Cr3+ ion, its dependent DNAzyme can specifically cleave the substrate strand, resulting in the release of ligation probe, which will trigger hyperbranched rolling circle amplification (HRCA) to produce hydrogen ions, causing the color change of the solution containing cresol red. A free APP named "Pixel Picker" has been further used to measure the RGB values. It can be well found that the R/G values correlate with Cr3+ ion concentrations with a linear detection range of 0.5 μM–500 μM and a lowest detection limit of 0.12 μM. In addition, the proposed biosensor has been successfully applied to determine Cr3+ ions in various milks. In a word, the constructed smartphone-assisted colorimetric biosensor has the advantages of simplicity, low cost, high specificity and anti-interference ability.

Near-Infrared Phosphorescent Hybrid Organic-Inorganic Perovskite with High-Contrast Dielectric and Third-Order Nonlinear Optical Switching Functionalities.

Hybrid organic–inorganic perovskites providing integrated functionalities for multimodal switching applications are widely sought-after materials for optoelectronics. Here, we embark on a study of a novel pyrrolidinium-based cyanide perovskite of formula (C4H10N)2KCr(CN)6, which displays thermally driven bimodal switching characteristics associated with an order–disorder phase transition. Dielectric switching combines two features important from an application standpoint: high permittivity contrast (Δε′ = 38.5) and very low dielectric losses. Third-order nonlinear optical switching takes advantage of third-harmonic generation (THG) bistability, thus far unprecedented for perovskites and coordination polymers. Structurally, (C4H10N)2KCr(CN)6 stands out as the first example of a three-dimensional stable perovskite among formate-, azide-, and cyanide-based metal–organic frameworks comprising large pyrrolidinium cations. Its stability, reflected also in robust switching characteristics, has been tracked down to the Cr3+ component, the ionic radius of which provides a large enough metal–cyanide cage for the pyrrolidinium cargo. While the presence of polar pyrrolidinium cations leads to excellent switchable dielectric properties, the presence of Cr3+ is also responsible for efficient phosphorescence, which is remarkably shifted to the near-infrared region (770 to 880 nm). The presence of Cr3+ was also found indispensable to the THG switching functionality. It is also found that a closely related cobalt-based analogue doped with Cr3+ ions displays distinct near-infrared phosphorescence as well. Thus, doping with Cr3+ ions is an effective strategy to introduce phosphorescence as an additional functional property into the family of cobalt-cyanide thermally switchable dielectrics.

SPR based gold nano-probe as optical sensor for cysteine detection via plasmonic enhancement in the presence of Cr3+

A selective and sensitive detection of L-cysteine (Cys) is an important tool for various biological studies. Here, Au nanoparticles (NPs) were prepared by chemical reduction technique. The probe was developed to detect and quantify Cys in the presence of Cr3+ ions which acts as a cross linker. The citrate capped Au NPs probe was analyzed by UV–visible spectrophotometry, TEM, EDAX, FTIR, DLS, XPS and zetasize. The zeta potential and effective size of Au NPs were −41.22 mV and 12 nm, respectively. The Cys interaction with Au NPs showed drastic colour variation from red to purple and colourless with rapid response time of 1 min. The limit of detection (LOD) of Au NPs probe was as low as 0.012 nM. The TEM image of Au NPs after Cys interaction verified the aggregation that resulted in colour change. The XPS core level scans of Au 4f showed 0.3 eV red shift when Cyswas interacted. The Au NPs sensor is highly selective for Cys with excellent reproducibility. Acidic pH slightly favored Cys detection. Further, the probe was applied to estimate Cys quantity from milk, urine, blood and environmental augmented samples in the presence of other amino acids . The study suggests that the proposed Au NPs could detect Cys with high accuracy from various biological samples.

Seed coat suberin forms a barrier against chromium (Cr3+) during early seed germination in Arabidopsis thaliana

The Arabidopsis seed coat contains various lipid-based (suberin and cutin), carbohydrate-based (mucilage) and phenolic-based (proanthocyanidin) polymers that may influence seed permeability to various solutes. We investigated the roles of these polymers in protection against a potential soil contaminant, chromium (Cr3+), during seed germination in Arabidopsis thaliana. Wild-type and mutants impaired in one or more of these seed coat polymers were exposed to different Cr3+ concentrations (0, 50, 100, 200, 400 and 800 mg L−1) during seed stratification and early imbibition. Mutants with significant reductions in seed coat suberin were highly sensitive to Cr3+. Suberin-altered mutants demonstrated reduced seed germination with increasing Cr3+ concentrations. At the highest level of Cr3+ (800 mg L−1), mutants deficient in suberin showed reduced embryo viability, indicating that chromium was directly damaging the embryo. This was correlated with increased seed coat permeability of the suberin-deficient mutants to tetrazolium salts. A cutin mutant that is reduced in seed coat C16-C18 α,ω-dicarboxylic fatty acids of the polyester was not affected by Cr3+. Mutants that were strongly reduced in rhamnose, a component of rhamnogalacturonan-I (RG-I), had moderate sensitivity to Cr3+ in terms of seed germination rates. Although many proanthocyanidin mutants displayed reduced seed germination in the presence of Cr3+, the viabilities of their embryos were only slightly reduced at high Cr3+ concentrations. We speculate that Cr3+ exposure induced germination arrest in proanthocyanidin mutants, which have a defective endosperm-associated cuticle. Our findings provide evidence that various polymer types in Arabidopsis seed coat provide protection against Cr3+ by different mechanisms and degrees. Seed coat suberin was identified as the main physical barrier against Cr3+ toxicity. The results also highlight the risks associated with Cr3+ toxicity on the persistence of seeds that have relatively low seed coat suberin in soils contaminated with high levels of chromium.

Single-particle cadmium(Ⅱ) and chromium(Ⅲ) ions assay using GNP@Ag core−shell nanoparticles with dark-field optical microscopy

Heavy metal pollution is a serious environmental problem in some regions. Regular monitoring heavy metal contaminations in the environment is quite significant for human life and health. In this work, we utilize GNP@Ag nanoparticles (NPs) as the probe for sensitively detecting Cd2+ and Cr3+ in aqueous solution by dark-field optical microscopy (DFM) based single-particle detection (SPD) method. Herein, Cd2+ will cause the probe aggregation and exhibit an obvious red-shift of the localized surface-plasmon resonance (LSPR) peak. In the presence of Cr3+, noticeable increase in scattering intensity from the probe together with a weak red-shift of its LSPR peak is shown. Moreover, Cd2+ and Cr3+ can be quantified statistically through calculating the ratio of color change by DFM. Under optimal conditions, the linear dynamic ranges are obtained from 1 to 5 and 2 to 10 μM with detection limit of 11.5 and 26.8 nM for Cd2+ and Cr3+, respectively. Due to the ultra-high sensitivity and excellent specificity, this method is expected to have broad applications such as environmental monitoring and groundwater analysis in the future.

Microstructure and electrical properties of xY2O3-(1-x)LaCrO3 thermosensitive ceramics prepared by spark plasma sintering

The high temperature, negative temperature coefficient (NTC), thermosensitive ceramics xY2O3-(1-x)LaCrO3 (x = 0.4, 0.5, 0.6, 0.7) were prepared via spark plasma sintering. The effects of components, sintering temperature, and sintering pressure on the electrical properties of the composite ceramics were studied. The composite NTC ceramics were composed of orthogonal perovskite structure LaCrO3 and Y2O3. The presence of Cr3+ and Cr4+ was confirmed using X-ray photoelectron spectroscopy, which may be responsible for the hopping conduction. The composite NTC ceramics sintered at 1500 °C had good electrical properties. The resistivities and the coefficient of temperature sensitivity (B) increased with the rise in Y2O3 content. The values of ρ250, ρ700, B400/700, and activation energy of xY2O3-(1-x)LaCrO3 composite NTC ceramics sintered at 1500 °C were 1.7 × 1010–5.51 × 1010 Ω cm, 4.32 × 104–6.16 × 106 Ω cm, 14,111–16,223 K, and 1.221–1.403 eV, respectively. The composite NTC ceramics prepared at different sintering pressures displayed identical electrical properties.

Forced hydrolysis of FeCl3 solutions in the presence of Cr3+ ions

Forced hydrolyses of FeCl3 solutions in the presence of Cr3+ ions without alkali addition were investigated at 160 and 200 °C. These precipitation systems were compared to corresponding reference systems. The isolated precipitates were characterized with XRD, 57Fe Mössbauer, FT-IR, FE SEM and photocatalytic measurements. Although chromium was not detected by EDS (Energy Dispersive X-ray Spectroscopy), the analysis of samples precipitated in the presence of Cr3+ ions showed several effects which can be attributed to the presence of these ions in the starting solutions. These effects are specifically well pronounced for samples obtained at 200 °C. For the highest concentration of Cr3+ ions and upon heating at 200 °C the transformation kinetics β-FeOOH to α-Fe2O3 was impeded. Relative intensities of prominent diffraction lines 104 and 110 of α-Fe2O3 changed as a result of the presence of Cr3+ ions. Changes in the size and formation of lemon-like particles instead of cube-like α-Fe2O3 particles were also noticed. The presence of Cr3+ ions in hydrolysing FeCl3 solution influenced the photocatalytic degradation of rhodamine B. Since no specific adsorption of Cr3+ ions occurred in the acidic pH medium, it was inferred that traces of Cr3+ ions enter into the structural tunnels of β-FeOOH crystals. The associates Cl−-Cr3+ are formed, which in the next step destabilize the crystal structure of β-FeOOH particles. Cr3+ ions leave the crystal structure upon dissolution of β-FeOOH. It can be assumed that α-Fe2O3 crystals start to grow on very fine and thin β-FeOOH crystallites which were not completely dissolved, but were previously affected by Cr3+ ions.

Effect of additives on cadmium chemical vapor generation and reliable quantification of generation efficiency

Chemical vapor generation (CVG) of cadmium was optimized based on response from atomic absorption spectrometry (AAS) with a heated quartz tube atomizer (QTA). Effect of several modifiers on analytical performance was studied. These additives were: inorganic salts of Cr3+, Ti4+ and Co2+ and their on-line synthesized complexes with KCN and thiourea, respectively. The use of these additives resulted in sensitivity enhancement, better repeatability and correspondingly in improvement of overall CVG efficiency. The latter was quantified by two independent approaches: a) by means of 115mCd radioactive indicator, b) from comparison of sensitivities obtained with conventional solution nebulization and with CVG, both coupled simultaneously to inductively coupled plasma mass spectrometry. Both approaches provided comparable results. The highest efficiency, between 60 and 70%, was reached in the presence of Cr3+/KCN and Ti4+/KCN while 19% was achieved in Co2+/ascorbic acid/thiourea environment. Highly irreproducible results with low CVG efficiency ranging from 2.5 to 15% were reached in the absence of any additives. The generated cadmium species were identified to be mostly free atoms regardless of the additives presence or their absence. Cr3+/KCN environment was selected as the most robust for CVG of Cd reaching sensitivity of 6.6 s ng−1 Cd and limit of detection of 60 pg mL−1 Cd (9 pg Cd absolute) with detection by QTA-AAS.