Preparation of Chiral Carbon Quantum Dots and its Application.

Chiral carbon quantum dots (cCQDs) , as a new type of carbon nano-functional material with tunable emission wavelength, superior photostability, low toxicity, biocompatibility and chirality, are playing an increasingly important role in the fields of chemistry, biology and medicine. This paper reviews the preparation methods (one-step and two-step), optical properties (UV, fluorescence, chirality) and applications in chiral catalysis, chiral recognition, targeted imaging as well as other fields, while lists some of the issues and challenges in the research of chiral carbon quantum dots. Finally, due to its good fluorescence and other properties, it is expected that chiral carbon quantum dots will have broad commercial prospects in future applications.

Preparation of amino acid chiral ionic liquid and visual chiral recognition of glutamine and phenylalanine enantiomers.

In this paper, the amino acid chiral ionic liquid (AACIL) was prepared with L-phenylalanine and imidazole. It was characterized by CD, FT-IR, 1H NMR, and 13C NMR spectrum. The chiral recognition sensor was constructed with AACIL and Cu(II), which exhibited different chiral visual responses (solubility or color difference) to the enantiomers of glutamine (Gln) and phenylalanine (Phe). The effects of solvent, pH, time, temperature, metal ions, and other amino acids on visual chiral recognition were optimized. The minimum concentrations of Gln and Phe for visual chiral recognition were 0.20 mg/ml and 0.28 mg/ml, respectively. The mechanism of chiral recognition was investigated by FT-IR, TEM, SEM, TG, XPS, and CD. The location of the host-guest inclusion or molecular placement has been conformationally searched based on Gaussian 09 software.

One-step hydrothermal preparation of chiral carbon quantum dots and enantioselective sensing of glutamine enantiomeric isomers.

A novel method for chiral identification of glutamine enantiomers based on chiral carbon quantum dots (cCQDs) fluorescent probes. cCQDs were prepared using a one-step hydrothermal method with L-tryptophan as the carbon source and chiral source, producing spherical nanoparticles exhibiting a blue colour luminescence. The fluorescence intensity (F) of cCQDs was enhanced or quenched following the addition of chiral enantiomeric glutamine (L/D-Gln), and therefore cCQDs, as a fluorescence probe, could be used for enantioselective sensing of the L/D-Gln. The fluorescence enhancement value (∆FE ) exhibited good linearity with L-Gln concentration in the range 0.23-10.00 mM, and the limit of detection was 0.14 mM. The fluorescence quenching value (∆FQ ) showed a good linear relationship with D-Gln concentration in the range 0.29-10.00 mM, and the detection limit was 0.18 mM. The mechanism of fluorescence enhancement/quenching was explored by molecular modelling and the type of quenching. The method was applied to the determination of L-Gln content in real samples, and the recovery rate was satisfactory. This study provided a novel approach for the synthesis of cCQDs and the recognition of amino acid enantiomers.

Ni-MOF Functionalized Carbon Dots with Fluorescence and Adsorption Performance for Rapid Detection of Fe (III) and Ascorbic Acid.

In this work, an "on-off-on" fluorescent probe based on Ni-MOF functionalized Nitrogen-doped carbon quantum dots (Ni-MOF-NCDs) was developed. Ni-MOF-NCDs was characterized by FT-IR, TEM, SEM, and XPS. The presence of Fe (III) will reduce the fluorescence intensity of Ni-MOF-NCDs and "turn off" the fluorescence signal at emission peak of 390 nm, while the signal can be "turn on" after the addition of ascorbic acid (AA). The Ni-MOF-NCDs was established as an "on-off-on" fluorescent probe for the detection of Fe (III) and AA with the linear ranges of 0.029-8.0 µg/mL and 0.263-18.0 µg/mL, respectively. The method has been successfully applied to the detection of water samples and foods with satisfactory recovery. The experimental results showed that Ni-MOF-NCDs not only had the fluorescence properties of NCDs, but also had the adsorption performance of Ni-MOF.

Choline Proline Ionic Liquid-Functionalized Fe3O4@SiO2 Nanoparticle Magnetic Solid Phase Extraction Coupled with High-Performance Liquid Chromatography for Analysis of Allura Red in Lipstick Sample.

A separation/analysis of allura red based on magnetic solid-phase extraction-high-performance liquid chromatography was developed. The extractant was prepared by functionalizing choline proline ionic liquid on Fe3O4@SiO2(Fe3O4@SiO2@[Ch][Pro]). Infl uences of experimental variables including extraction condition (material amount, pH, time, temperature, ionic strength, and sample volume) and elution conditions (eluent selection, amount, time) were evaluated. Under the optimal conditions, good linear calibration curves were obtained in the range of 0.02-5.0 µg/mL, and limits of detection was 9.0 ng/mL. The proposed method was successfully applied for the determination of allura red in lipstick sample.

Synthesis of Poly-Amino Acid Ionic Liquid Up-Conversion Fluorescent Probe and its Application in Fe(II)/Fe(III) Speciation Analysis.

The poly amino acid ionic liquid (poly-1-vinyl-3-butylimidazolium glutamate acid, p-1-VbmGlu), with a stable up-conversion fluorescence(UCF) probe, was firstly prepared and the synthesis conditions were optimized. The UCF were found to be specifically quenched by Fe(III), but not respond to Fe(II). In H2O2 medium, Fe(II) posed strong quenching effect on the UFC owing to Fe(III) produced by redox between H2O2.and Fe(II). Therefore p-1-VbmGlu was employed as a UFC for Fe(II)/Fe(III) speciation analysis under the control of H2O2. The detection limits of Fe(II)/Fe(III) were 6.16 ng/mL and 4.48 ng/mL, with relative standard deviations of 1.1% and 2.0%, respectively. This method was successfully utilized in the analysis of Fe(II)/Fe(III) in multiple real samples.

Use of Ionic liquids as additives in ion exchange chromatography for the analysis of cations.

The behavior of acids (citric acid, nitric acid, oxalic acid, tartaric acid) as a mobile phase and imidazolium ionic liquids (the bromides, tetrafluoroborates and hexafluorophosphates of 1-ethyl, 1-butyl, and 1-hexyl-3-methylimidazolium) as additives in ion exchange chromatography for cations (Na+ , K+ , Mg2+ , Ca2+ ) separation were studied. The results showed that nitric acid and 1-hexyl-3-methyl-imidazolium hexafluorophosphate offered the most interesting features in the separation of cations, such as lower retention time and better resolution. The selected optimal conditions were achieved by adding 0.10 mM 1-hexyl-3-methyl-imidazolium hexafluorophosphate in 4.0 mM HNO3 mobile phase for the separation of four cations with the flow rate of 0.9 mL/min at room temperature (25°C). The linear regression equations of Na+ , K+ , Mg2+ , Ca2+ were S = 4.4763c + 0.0209, S = 3.8903c - 0.0087, S = 6.3974c - 0.0173, and S = 7.601c - 0.0339 and the limits of detection of Na+ , K+ , Mg2+ , Ca2+ were 0.296, 4.98, 0.0970, and 1.22 µg/L, respectively. In this work, four cations in samples were successfully detected.

Methyl-ß-Cyclodextrin /Cetyltrimethyl Ammonium Bromide Synergistic Sensitized Fluorescence Method for the Determination of Levofloxacin.

A novel method of methyl-ß-cyclodextrin (methyl-ß-CD) and cetyltrimethyl ammonium bromide (CTAB) synergistic sensitized fluorescence analysis to determine levofloxacin (LVFX) was developed. The results were shown that the fluorescence intensity of LVFX was increased a lot in the system of methyl-ß-cyclodextrin-CTAB medium. Under the conditions of λ(ex/em )= 330/507 nm and pH 4.5, the linear range and the detection limit for LVFX were found to be 0.040 ~ 4.0 µg/mL and 0.3 ng/mL, respectively. The mechanism of sensitized fluorescence method was discussed by the solubilization capacity and the microenvironment of medium. The proposed method has been applied for the determination of LVFX in eye drops real samples and human serum with satisfactory recovery.

[Fe3O4-ß-Cyclodextrin Polymer Nano Composites Solid-Phase Extraction-UV-Vis Spectrophotometry for Separation Analysis Malachite Green].

In this paper, carboxymethyl-hydroxypropyl-ß-cyclodextrin polymer modified magnetic particles Fe3O4 (CM-HP-ß-CD- CP-MNPs) were prepared and applied to magnetic solid phase extraction of malachite green combined with UV-Visible spectrom- etry detection. The synthesized magnetic particles were characterized by element analysis, Fourier transform infrared spectra and transmission electron microscopy. Several variables affecting the extraction and desorption of malachite green such as pH, the amount of adsorbent, the type and volume of eluent, extraction and desorption time, and temperature were investigated. Under the optimum conditions, malachite green could be adsorbed by CM-HP-ß-CDCP-MNPs (RE% = 92), and elution by C2H5OH (EE% = 90). the preconcentration factor of the proposed method was approximately 7.5, the CM-HP-ß-CDCP-MNPs could be used repeatedly for 5 times and offered better recovery. The linear range and detection limit (DL) were found to be 0.08~8.00 µg · mL⁻¹ and 5.6 ng · mL⁻¹ respectively. This technique had been successfully applied to the determination of malachite green in real samples. The inclusion interaction of CM-HP--CDCP-MNPs with malachite green was studied through FTIR.

[Determination of clopidogrel sulfate in pharmaceutical formulation and biological fluids by extraction spectrofluorimetric method].

A simple and sensitive spectrofluorimetric method has been developed for the determination of clopidogrel sulfate in pharmaceutical formulation and human urine/serum. It is based on the formation of ion-pair complex between clopidogrel sulfate and alizarin red in 0.3 mol x L(-1) hydrochloric acid solution. The ion pair complex was extracted in dichloromethane and the fluorescence intensity was measured at 550 nm after excitation at 428 nm. The various factors influencing ion-pair complex formation and fluorescence determination were discussed. Under the optimized conditions, the fluorescence value showed a good linear relationship with the clopidogrel sulfate concentration ranging from 1.0 to 11.0 µg x mL(-1). The equation of calibration curve was F = 53.32 + 35.01c (µg x mL(-1)), r = 0.994, and the detection limit was found to be 0.11 µg x mL(-1). No interference was observed from common co-existing substances or pharmaceutical excipient. The determination recoveries of clopidogrel sulfate in pharmaceutical formulation and human urine/serum samples were 90.6%-99.3%, 104.6%-109.3%, 96.3%-105.0%, respectively. The method was successfully applied to detect clopidogrel sulfate in clopidogrel sulfate tablet and human urine/ serum. The obtained results of clopidogrel sulfate tablet were in good agreement with the results of HPLC. Therefore, it is concluded that the proposed method is simple, sensitive and rapid for the determination of clopidogrel sulfate in real samples.

Synthesis of CoFe2O4@SiO2-NH2 and its application in adsorption of trace lead.

In this work, an amine functionalized CoFe2O4 magnetic nanocomposite material CoFe2O4@SiO2-NH2 was prepared successfully by modifying coated-CoFe2O4@SiO2 magnetic nanoparticles with 3-aminopropyltriethoxysilane (APTES) and became an efficient adsorbent for the separation and analysis of trace lead in water. The CoFe2O4@SiO2-NH2 magnetic nanoparticles were characterized using SEM, TEM, XRD, FTIR, VSM and BET techniques. Then, the adsorption mechanism was preliminarily investigated through ZETA, XPS, and adsorption kinetic experiments. The adsorption process was fitted by pseudo-second-order kinetics and a Langmuir isotherm model. The main adsorption mechanism of CoFe2O4@SiO2-NH2 towards lead ions was the chelation between the amino groups of CoFe2O4@SiO2-NH2 and lead cations, as well as the strong Coulomb interaction between the electron donor atoms O and N in the surface of CoFe2O4@SiO2-NH2 and lead cations. The adsorption capacity is 74.5 mg g-1 and the adsorbent can be reused 5 times. Hence, this prepared CoFe2O4@SiO2-NH2 could find potential applications for the removal of trace metal ions in surface water.

ß-Cyclodextrin sensitized spectrofluorimetry for the determination of abiraterone acetate and abiraterone.

A novel spectrofluorimetric method to determine abiraterone acetate and its active metabolite, abiraterone was developed, based on the fact that fluorescence intensity of abiraterone acetate and abiraterone could be enhanced in ß-cyclodextrin (ß-CD) due to the formation of the inclusion complex. The inclusion interaction of ß-CD and abiraterone acetate and the ß-cyclodextrin sensitized spectrofluorimetry was examined. The various factors influencing fluorescence were discussed in details. The results showed that under the optimized conditions, the linear range of calibration curve for the determination of biraterone acetate and abiraterone was 0.20 ~ 6.0 µg/mL, and the detection limit (LOD) was 6.8 (r = 0.997) or 6.6 ng/mL (r = 0.996), respectively. No interference was observed from common co-existing substances or pharmaceutical excipient. The method was successfully applied to the analysis of abiraterone acetate in pharmaceutical formulation and abiraterone in human serum/urine.

Imidazole ionic liquid functionalized ZIF-67 molecularly imprinted solid-phase extraction coupled with high performance liquid chromatography for analysis of bisphenol A.

An effective method based on an imidazole ionic liquid functionalized ZIF-67 molecularly imprinted solid-phase extractant (ZIF-67@[Bmim][Br]@MIP) coupled with high performance liquid chromatography (HPLC) for the separation/analysis of bisphenol A (BPA) was established. ZIF-67@[Bmim][Br]@MIP was characterized by FTIR, XRD, SEM, TEM and BET. Several important factors, such as pH, amount of extractant, extraction time, and types of eluents were investigated in detail. Under the optimal conditions, the linear range of the method was 0.01-20.00 µg mL-1, the detection limit was 5.0 ng mL-1, and the linear correlation was good (R2 = 0.9994). The detection of BPA in mineral water bottles, milk cartons and milk tea cups proved that the method was simple and effective, and could be used to separate and analyze BPA in real samples.

Pyridine ionic liquid functionalized bimetallic MOF solid-phase extraction coupled with high performance liquid chromatography for separation/analysis sunset yellow.

An effective method based on the pyridine ionic liquid functionalized bimetallic MOF solid-phase extractant (Cu/Co-MOF@[PrPy][Br]) coupled with high performance liquid chromatography (HPLC) for the separation/analysis sunset yellow was established. Cu/Co-MOF@[PrPy][Br] was characterized by FTIR, XRD, SEM and TEM. Several important factors, such as pH, amount of extractant, extract time, and types of eluents were investigated in detail. Under the optimal conditions, linear range of the method was 0.05-40.00 µg mL-1, the detection limit was 0.02 µg mL-1, and the linear correlation was good (R 2 = 0.9992). The analysis of sunset yellow in soda, effervescent tablet and jelly proved that the method was simple and effective.

Determination of nickel(II) by CTAB sensitized fluorescence quenching method of the derivatives of calix[4]arene.

The fluorescence quenching effect of Ni(2+) on the derivatives of p-tert- butyl-calix[4]arene with o-phenanthroline(TBCP) was studied in cetyltrimethyl- ammonium bromide (CTAB) medium. Ni(2+) reacted with the TBCP to form inclusion complex. The fluorescence quenching was sensitized in CTAB. The linear range of calibration curve for the determination of Ni(2+) was 0.050 µg/mL ~ 1.00 µg/mL. The detection limit estimated (S/N = 3) was 5.3 ng/mL. It has been applied for the determination of Ni(II) in samples with satisfactory results.

Determination of iron(III) by room temperature ionic liquids/surfactant sensitized fluorescence quenching method.

A new method for the determination of iron (III) has been described. The analytical procedure was based on the fluorescence quenching of salicylfluorone (SAF) by iron (III) and the fluorescence quenching value (ΔF) could be increased in the medium of room temperature ionic liquids (RTILs) (1-ethyl-3-methylimidazolium ethyl sulfate)/SDS (sodium dodecyl sulfate). The main factors influencing the fluorescence quenching (ΔF) were investigated in detail. Under the optimal conditions, the linear equation was [Formula: see text](c:µg·mL(-1), r = 0.9936). The linear range of calibration curve was 0.2-1.1 µg·mL(-1) and the detection limit was 8.3 ng·mL(-1). The preliminary sensitized mechanism was discussed with distribution coefficient and fluorescence quantum yield in different media. The method has been applied to the determination of Fe (III) in water samples with satisfactory results.

[Hydrophobic ionic liquid extraction-flame atomic absorption spectrophotometry for separation/analysis trace gold].

In the present paper, the hydrophobicity ionic liquid 1-butyl-3- methylimidazolium hexafluorophosphate ([C4mim] [PF6]) was synthesized with 1-methylimidazole and butylbromide and equimolar ammonium hexafluorophosphate, which was applied to preconcentration for trace gold. The factors which may affect preconcentration of gold were investigated. The experimental results showed that the absorbance was linear when the concentration of gold was in the range of 0.40-16.00 microg x mL(-1), with linear equation A = 0.007 63c + 0.073 87(c:microg x mL(-1)), correlation coefficient r = 0.999 1, and detection limit 0.072 microg x mL(-1). The method was applied to the determination of trace gold in water samples satisfactorily.

A facile green and one-pot synthesis of grape seed-derived carbon quantum dots as a fluorescence probe for Cu(ii) and ascorbic acid.

In this study, an on-off-on fluorescence probe for the detection of trace Cu(ii) and ascorbic acid (AA) based on biomass-derived sulfur and nitrogen double heteroatom-doped carbon dots (N,S-CDs) was designed. For the first time, the probe (N,S-CDs) was prepared from grape seeds and thiourea as the precursor. Cu(ii) was added to the carbon point solution, the fluorescence intensity (FL) of N,S-CDs was strongly quenched (switch OFF) and the fluorescence probe turned to "ON" (switch ON) with the addition of AA. Under the optimal conditions, the as-synthesized N,S-CDs had a good detection performance for Cu(ii) and AA assay with the linearity ranges from 150-500 µg mL-1 and 0.1-400 µg mL-1, and the LODs were 0.048 mg L-1 and 0.036 mg L-1, respectively. The as-prepared N,S-CDs exhibited a low cytotoxicity and a good biocompatibility, which show their potential for application in the biological imaging of living cells.

On-line separation/analysis of Rhodamine B dye based on a solid-phase extraction high performance liquid chromatography self-designed device.

A special self-designed device based on poly-1-vinyl-3-pentylimidazole hexafluorophosphate (PILs-C5) solid-phase extraction and high performance liquid chromatography (HPLC) is proposed as a novel method for the on-line separation and analysis of Rhodamine B (RhB) dye. Single factor experiment design and orthogonal experiment design were used to optimize the experimental parameters, such as pH, the amount of PILs-C5, sample volume, flow rate, eluent type, eluent concentration, eluent volume, and the flow rate of eluent. Under the optimized conditions, the linear range was 0.02-2.4 µg mL-1, with the correlation coefficients (R 2) of 0.997. The limit of detection (LOD) and limit of quantification (LOQ) were 0.004 µg mL-1 and 0.02 µg mL-1, respectively. The extraction capacity was 6.22 mg g-1, and enrichment ratio was 15. The extraction mechanism and the post-treatment method of PILs-C5 were also studied. This method was applied to analyze RhB in a wide variety of real samples with satisfactory results.

Modified nano-TiO2 coupled with fluorescence spectroscopy for the separation/analysis of L-tryptophan.

A novel adsorbent of carboxymethyl-beta-cyclodextrin modified nanometer TiO(2) (CM-beta-CD/TiO(2)) was prepared and used as a solid-phase extraction (SPE) material coupled to fluorescence spectroscopy determination of l-tryptophan (l-Trp) in biological samples. The experimental conditions for modified nanometer TiO(2) separation/preconcentration of l-Trp were optimized. The adsorption capacity of CM-beta-CD/TiO(2) for l-Trp was 75.2 microg/g. The linear range, detection limit (DL), and the relative standard deviation (RSD) were 0.10-1.20 microg/mL, 18.8 ng/mL, and 0.67% (n=3, 1.0 microg/mL), respectively, with a preconcentration factor of 10. The developed method was applied to determination of l-Trp in real samples and the recoveries were found to be in the range of 99.2-100.3%. For validation, a comparison material of NIC-140686 sample was analyzed and the determined value was in good agreement with the certified value.