Fluorescence sensor based on glutathione capped CdTe QDs for detection of Cr^3+ ions in vitamins

In this work,glutathione capped CdTe QDs(GSH-QDs)were prepared through a one-pot process and found to be quenched by Cr^3+,Ag^+and Cu^2+ions.Cr^3+and chromium(III)picolinate could be quantitatively measured after masking Cu^2+and Ag+ions by sulfide.Under optimal conditions,linear quenching was observed for Cr^3+in the ranges of 0–2.0M and the limit of detection was 3.0 nM.The recoveries for Cr^3+in vitamin supplements obtained were from 92.5%to 106%.The determination results of chromium(III)picolinate in vitamin supplement samples were compared to that obtained using flame atomic absorption spectrometry(FAAS)method,and the result showed good reliability.

Spectrophotometric Method for Determination of Chromium Ion in Aqueous Solution Using Ninhydrin

A simple, precise, inexpensive and reproducible spectrophotometric method was investigated for the determination of chromium ion (III) in aqueous media, this method based on the formation of a complex between chromium ion (III) and ninhydrin, a deep greenish-violet colored product in the presence of potassium hydroxide was obtained. The absorption of this product was measured at λmax = 375 nm. The reaction proceeds quantitatively at room temperature. The linear calibration curve was constructed over range of (4.8 × 10-4 - 1.6 × 10-2) mol/L of chromium ions with molar absorptivity of 2.90 × 102 and correlation coefficient R2 = 0.9989. The calculated Sandell’s sensitivity value is 0.179 μg/cm2, the limits of detection (LOD) and the limit of quantification (LOQ) are found to be 3.74 × 10-5 and 1.24 × 10-4 mol/L, respectively. The method was successfully applied for determination of the chromium ion in aqueous solution. The stoichiometry of the reactions was determined molar combining ratio of 1:2 between chromium and ninhydrin.

EFFECT OF THE EXISTING STATES OF CHROMIUM ION ON THE COLOR CHARACTERISTICS OF DOPED β-C_2S

According to the theory of crystal field, the existing state of chromium ions in β-C_2S was studied with optical spectra and EPR. The energy levels of chromium ions were calculated. Chromium ions exist in form of Cr^(4+) and Cr^(5+) coordinated with distorted octahedra. The reason of fading of β-C_2S hydrate is that the strength of light absorption declines be- cause of the valence change of chromium ions and chroninm dissolves out and loses in water.

Adsorption of Cr(III) from an Aqueous Solution by Chitosan Beads Modified with Sodium Dodecyl Sulfate (SDS)

This study is to prepare chitosan beads modified with sodium dodecyl sulfate (SDS) to effectively remove Cr(III) from an aqueous solution. The characterizations of SDS-chitosan by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Fourier transform-infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) proved the successful synthesis of the adsorbent. The adsorption of Cr(III) on the SDS material was investigated by varying experimental conditions such as pH, contact time and adsorbent dosage. The maximum adsorption capacity of SDS-chitosan for Cr(III) was estimated to be 3.42 mg?g-1. The results of adsorption kinetics and isothermal models show that the adsorption process conforms to the pseudo-second-order and Langmuir isotherm models, indicating that the adsorption is single-layer chemical adsorption. Thermodynamic analyses indicate that the adsorption of Cr(III) is an endothermic reaction. These results show that the new adsorbent has obvious application prospect to eliminate Cr(III).

Modulation of red-light emission from carbon quantum dots in acid-based environment and the detection of chromium(Ⅲ)ions

ⅢIn this study,the carbon quantum dots,which can emit sharp red light(R-CQDs)under optical excitation,were synthesized via simple heat treatment of wine lees.The features of the photoluminescence(PL)emission from R-CQDs in solutions with different p H values and with metal ions were examined.The intensity of the PL emission from R-CQDs depends sensitively on the p H values of the solutions with the R-CQDs.Interestingly,the p H-response of the PL intensity is reversible and can be enhanced linearly in the p H value range from 4 to 12,indicating that the R-CQDs can be applied for the p H sensor.Furthermore,the quench of the PL emission from R-CQDs can be observed when adding chromium(Ⅲ)ions into the solution with R-CQDs.This effect can be utilized for selective and quick detection of chromium(Ⅲ)ions in solutions simply via the standard PL measurement.The interesting and important findings from this work can be applied to explore more practical applications of the CQDs prepared cheaply and easily.

Novel Cr^(3+)-activated far-red emitting phosphors withβ-Ca_(3)(PO_(4))_(2)-type structure for indoor plant cultivation

Cr^(3+)-activated far-red and near-infrared phosphors have drawn considerable attention owing to their adjustable emission wavelengths and wide applications.Herein,we reported a series of Cr^(3+)-doped phosphors withβ-Ca_(3)(PO_(4))_(2)-type structure,of which Ca_(9)Ga(PO_(4))_(7):Cr^(3+) possessed the highest far-red emission intensity.At an excitation of 440 nm,the Ca_(9)Ga(PO_(4))_(7):Cr^(3+) phosphors exhibited a broad emission band ranging from 650 to 850 nm and peaking at 735 nm,and the broadband superimposed two sharp lines centering at 690 and 698 nm.The optimal sample Ca_(9)Ga_(0.97)(PO_(4))_(7):0.03 Cr^(3+) had an internal quantum efficiency of 55.7%.The luminescence intensity of the Ca_(9)Ga_(0.97)(PO_(4))_(7):0.03 Cr^(3+) phosphor obtained at 423 K could maintain 68.5%of that at room temperature,demonstrating its outstanding luminescence thermal stability.A phosphor-conversion light-emitting diode was fabricated,indicating that the Ca_(9)Ga(PO_(4))_(7):Cr^(3+) phosphor has potential applications in indoor plant cultivation.

Synthesis of Highly Stable Porous Metal-lminodiacetic Acid Gels from a Novel IDA Compound

In this work, a novel and simple flexible aromatic multi-carboxylate compound N,N＇（4,4＇-biphenylyl） iminodi- acetic acid （BP-IDA） was synthesized, with which two new stable metaMDA gels （denoted as MIGl and MlG2） with three-dimensional network structures have been prepared successfully by employing Cr^3＋ and Al^3＋ as the metal ions, respectively. The rheological performance was investigated by means of dynamic rheology measurement. The morphology and microstructure were characterized by scanning electron microscopy, transmission elec- tron microscopy, and X-ray diffraction technique. Nitrogen sorption isotherm measurement suggests that the MlG1 aerogel has considerable porosity with the Brunauer-Emmett-Teller specific surface area up to 760 m^2·g^-1. Owing to easy preparation, good stability, and three-dimensional network structure, the as-prepared metal-organic gels will possess potential applications in separation, catalysis, and drug delivery.