scholarly journals Bathophenanthroline as Turn-off Fluorescence Sensors for Selective and Sensitive Tetection of Fe(II)

2021 ◽  
Author(s):  
D. A. K. Senanayake ◽  
P. P. P. Perera ◽  
M. D. P. De Costa ◽  
Senthilnithy R
Keyword(s):  
Fluorescence Intensity ◽  
Colorimetric Method ◽  
Bidentate Ligand ◽  
Acetate Buffer ◽  
Response Time Analysis ◽  
Temperature Dependent ◽  
Fluorescence Sensors ◽  
Detection Range ◽  
Ph Values ◽  
Extraction Step

Abstract Bathophenanthroline (BPhen) is a versatile bidentate ligand for transition metals, also frequently used as a universal colorimetric probe for Fe(II). The effect of pH on the fluorescence intensity of BPhen and quenching constant of Fe(II) were studied at different pH values using working solutions of 50% ethanol buffered with acetate buffer. Fluorescence intensity of a 3.0 μM Bphen solution in 50% ethanol buffered at pH 6.6 with acetate buffer was selectively quenched by Fe(II) at 25 °C. The LOD of 19 nM at 3.3 σ and the linear range of 63 nM – 224 nM with R2 = 0.9919 revealed that this method is more sensitive than the colorimetric method (detection range =1.8 μM - 18 μM). Quenching of the BPhen-Fe(II) complex is temperature-dependent, which may be due to the increased stability of the formed complex with temperature, supporting a static quenching mechanism. Interference from foreign ions on the fluorescence of the BPhen-iron(II) complex was also studied. A tolerance limit exceeding 5% was observed and recorded. The interference from cations, Ni(II), Co(II), and Cu(II), was relatively higher, while the most common anions showed only a little to no interference. In response time analysis, the fluorescence intensity, which remains constant after 10 minutes, reveals that the system approached equilibrium. This method would be quicker and more accurate than a colorimetric method due to the absence of a solvent extraction step.

Study on Influence of Silicate Morphology Based on pH Value

2012 ◽  
Vol 454 ◽  
pp. 324-328
Author(s):  
Yan He ◽  
Ya Jing Liu ◽  
Yong Lin Cao ◽  
Li Xia Zhou
Keyword(s):  
Silicic Acid ◽  
Ph Value ◽  
Colorimetric Method ◽  
Absorption Spectrometry ◽  
Degree Of Polymerization ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ph Values ◽  
The Stability

Infra-red absorption spectrometry, X-ray diffraction observations and characterization tests based on silicon molybdenum colorimetric method were used to investigate the optimal pH value controlling the stability of the silicic acid form. The experiment process was done by using sodium silicate as raw material. The results showed that the solution of silicate influenced the polymerization. The active silicic acid solution with a certain degree of polymerization was obtained by controlling the pH values.

Synthesis and Luminescence Properties of Tb3+-Doped Hydroxyapatites

2011 ◽  
Vol 399-401 ◽  
pp. 1582-1587
Author(s):  
Su Ping Huang ◽  
Jun Zhu ◽  
Ke Chao Zhou
Keyword(s):  
Aspect Ratio ◽  
Fluorescence Intensity ◽  
Doping Concentration ◽  
Doping Content ◽  
Fluorescent Properties ◽  
Strong Fluorescence ◽  
Active Growth ◽  
Ph Values ◽  
Structure Morphology ◽  
Ultraviolet Ray

In this paper, the terbium -doped nano-HA powders with strong fluorescence was prepared by hydrothermal synthesis and its crystal structure，morphology and fluorescent properties are characterized by XRD, TEM, XPS, ICP and PL spectroscopy. Results showed that with the doping concentration of Tb3+increasing, the aspect ratio of Tb3+-doped HA particles decreased, while the fluorescence intensity excited by ultraviolet ray at 272 nm is significantly enhanced. With pH values increased from 6.5 to 10.0, the aspect ratio of Tb3+-doped HA decreased greatly, and the morphology of nano-Tb:HA particles changes from rod particles to equiaxed particles and the actual doping content and the fluorescence intensity tends to increase correspondingly, which can be explained that under alkaline solution, Tb3+was more easier entering the HA crystal, and the Tb3+would substitute the Ca2+ in both hydroxyapatite Ca(Ⅰ) and Ca(Ⅱ) site, which may block the active growth sites of the seed crystals and resulted in the growth rate and the ratio of length to radius decreasing.

scholarly journals Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 466
Author(s):  
Kaixin Chang ◽  
Qianjin Zhu ◽  
Liyan Qi ◽  
Mingwei Guo ◽  
Woming Gao ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Lactic Acid ◽  
Fluorescence Quenching ◽  
Functional Groups ◽  
Fluorescence Intensity ◽  
Carbon Quantum Dots ◽  
Nitrogen Doped ◽  
Ph Values ◽  
Wide Range ◽  
Nitrogen Doped Carbon

Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized in a one-step hydrothermal technique utilizing L-lactic acid as that of the source of carbon and ethylenediamine as that of the source of nitrogen, and were characterized using dynamic light scattering, X-ray photoelectron spectroscopy ultraviolet-visible spectrum, Fourier-transformed infrared spectrum, high-resolution transmission electron microscopy, and fluorescence spectrum. The generated N-CQDs have a spherical structure and overall diameters ranging from 1–4 nm, and their surface comprises specific functional groups such as amino, carboxyl, and hydroxyl, resulting in greater water solubility and fluorescence. The quantum yield of N-CQDs (being 46%) is significantly higher than that of the CQDs synthesized from other biomass in literatures. Its fluorescence intensity is dependent on the excitation wavelength, and N-CQDs release blue light at 365 nm under ultraviolet light. The pH values may impact the protonation of N-CQDs surface functional groups and lead to significant fluorescence quenching of N-CQDs. Therefore, the fluorescence intensity of N-CQDs is the highest at pH 7.0, but it decreases with pH as pH values being either more than or less than pH 7.0. The N-CQDs exhibit high sensitivity to Fe3+ ions, for Fe3+ ions would decrease the fluorescence intensity of N-CQDs by 99.6%, and the influence of Fe3+ ions on N-CQDs fluorescence quenching is slightly affected by other metal ions. Moreover, the fluorescence quenching efficiency of Fe3+ ions displays an obvious linear relationship to Fe3+ concentrations in a wide range of concentrations (up to 200 µM) and with a detection limit of 1.89 µM. Therefore, the generated N-CQDs may be utilized as a robust fluorescence sensor for detecting pH and Fe3+ ions.

Improved radioimmunoassay of urinary estriol.

1979 ◽  
Vol 25 (1) ◽  
pp. 99-102 ◽  
Author(s):  
M J Jawad ◽  
E A Wilson ◽  
H L Kincaid
Keyword(s):  
Incubation Time ◽  
Colorimetric Method ◽  
Detection Range ◽  
Standard Curve ◽  
Double Antibody ◽  
Analytical Recovery ◽  
Urinary Glucose

Abstract We report a rapid double-antibody radioimmunoassay for urinary estriol. Advantages over other current methods include: (a) 30-min hydrolysis; (b) total incubation time, 55 min; (c) assay unaffected by urinary glucose; (d) no degradation of estriol evident during hydrolysis; (e) superior (85%) analytical recovery of estriol conjugates; (f) linear standard curve by logit-log extrapolation; (g) good correlation (r = 0.83) with total estrogen determination by a generally accepted colorimetric method; (h) only 20 muL of urine required; and (i) the detection range is 1.9 to 100.5 mg/24-h urine.

scholarly journals Silver ion-doped CdTe quantum dots as fluorescent probe for Hg2+ detection

RSC Advances ◽  
2020 ◽  
Vol 10 (64) ◽  
pp. 38965-38973
Author(s):  
Huazheng Li ◽  
Wangwei Lu ◽  
Gaoling Zhao ◽  
Bin Song ◽  
Jing Zhou ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Fluorescent Probe ◽  
Fluorescence Intensity ◽  
Silver Ion ◽  
Cdte Quantum Dots ◽  
Detection Range ◽  
Cdte Qds ◽  
Linear Relationships ◽  
The Relationship

Ag-doped CdTe QDs emit multiple-fluorescence peaks, and the relationship between fluorescence intensity and the concentration of Hg2+ is established. Two linear relationships are obtained, which is benefit to the extension of detection range.

Liquid-chromatographic separation of urinary 5-hydroxy-3-indoleacetic acid, with measurement at 254 nm.

1980 ◽  
Vol 26 (7) ◽  
pp. 910-912
Author(s):  
P S Draganac ◽  
S J Steindel ◽  
W G Trawick
Keyword(s):  
High Performance ◽  
Indoleacetic Acid ◽  
Colorimetric Method ◽  
Internal Standard ◽  
High Performance Liquid Chromatographic ◽  
Reversed Phase ◽  
Acetate Buffer ◽  
Nitrobenzoic Acid ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic

Abstract A "high-performance" liquid-chromatographic procedure for 5-hydroxy-3-indoleacetic acid is described and compared with a colorimetric method in which 1-nitroso-2-naphthol is used. The analyte and an internal standard, p-nitrobenzoic acid, were extracted into diethyl ether from urine at pH 4.0 (acidified with HCl) to which sodium chloride had been added, and the ether was back-extracted with acetate buffer, pH 9.2. Aliquots of this extract were injected into a reversed-phase liquid-chromatographic column and eluted with pH 3.5 acetate buffer/methanol (95/5 by vol); the effluent was monitored at 254 nm. The precision (CV) of the method was 11.8% at 1.8 mg/L, 5.5% at 92 mg/L. Analytical recovery averaged 84%. The colorimetric method gave higher values for the analyte than did the chromatographic method for all patients' urines.

Heat stability of milk: interrelationship between assay temperature, pH and agitation

1981 ◽  
Vol 48 (1) ◽  
pp. 123-129 ◽  
Author(s):  
Douglas B. Hyslop ◽  
Patrick F. Fox
Keyword(s):  
Heat Stability ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Total Solids ◽  
Ph Values ◽  
Assay Procedure ◽  
Concentrated Milk ◽  
The Stability ◽  
Ph Curve ◽  
Maximum Minimum

SummaryAs determined by the standard subjective assay procedure, the minimum in the heat stability–pH curve of milk persisted down to at least 116 °C. However when samples were not agitated during heating the minimum became progressively less pronounced as the assay temperature was lowered and it disappeared at approximately 116 °C. Activation energies (Ea) for unagitated samples were approximately 30 Kcal/mole at pH 6·87 (maximum) and at pH 7·18, throughout the temperature range 116–145 °C and for the pH 6·95 (minimum) sample at 116–125 °C; however Eα for the pH 6.95 sample increased to approximately 100 Kcal/mole in the range 127–135 °C suggesting that some highly temperature-dependent reaction had occurred and caused premature coagulation at certain pH values, i.e. to a heat stability minimum. The stability of concentrated milk (20% total solids) was very low at pH values above 6·9, regardless of whether the samples were agitated or not during heating and the maximum/minimum in the heat stability–pH curve persisted down to at least 90 °C in both agitated and quiescent samples.

Investigation of Cu(II) adsorption from aqueous solutions by NKF-6 zeolite

2011 ◽  
Vol 63 (3) ◽  
pp. 395-402 ◽  
Author(s):  
H. Zhang ◽  
D. Zhao ◽  
L. Chen ◽  
X. J. Yu
Keyword(s):  
Aqueous Solutions ◽  
Outer Sphere ◽  
Low Ph ◽  
Ambient Conditions ◽  
Temperature Dependent ◽  
Ph Values ◽  
Batch Technique ◽  
Negative Effect ◽  
High Level ◽  
Positive Effect

Adsorption of Cu(II) from aqueous solutions using NKF-6 zeolite was investigated by batch technique under ambient conditions. The adsorption was investigated as a function of pH, ionic strength, fulvic acid (FA), foreign ions and temperature. The results indicated that the adsorption of Cu(II) on NKF-6 zeolite gradually increases from 0 to 90% with increasing pH at pH<6.5, and maintains high level at pH>6.5. Outer-sphere complexation or ion exchange may be the main adsorption mechanism of Cu(II) to NKF-6 zeolite at low pH values, whereas the adsorption of Cu(II) at pH>6.5 is mainly dominated by inner-sphere complexation or precipitation. A positive effect of FA on Cu(II) adsorption onto NKF-6 zeolite is observed at low pH values, while a negative effect of FA is observed at high pH values. The thermodynamic parameters (i.e., ΔH0, ΔS0 and ΔG0) for the adsorption of Cu(II) were determined from the temperature dependent isotherms at 20, 40 and 60°C, respectively, and the results indicated that the adsorption reaction is favoured at low temperature. The results suggested that the adsorption process of Cu(II) on NKF-6 zeolite is spontaneous and exothermic.

scholarly journals Study of the Intrinsic Fluorescence of a Highly Branched Cationic Dendrimer, Poly(Ethyleneimine) (PEI)

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3690
Author(s):  
Viktória Tóth ◽  
Péter Hermann ◽  
Dániel Végh ◽  
Tivadar Zelles ◽  
Zoltán Géczi
Keyword(s):  
Solar Cell ◽  
Fluorescence Intensity ◽  
Mass Concentration ◽  
Reliable Method ◽  
Direct Method ◽  
Molar Concentration ◽  
Amino Groups ◽  
Molecular Weights ◽  
Ph Values ◽  
Tertiary Amino

Poly(ethyleneimine) (PEI) is a weakly basic, synthetic, polycationic polymer, due to the presence of primary, secondary, and tertiary amino groups. The amino groups are responsible for the variety of applications of PEI (e.g., transfection, bioimaging, solar cell, etc.). Our study presents some new and reproducible methods for the quantification of molecular or mass concentration of highly branched PEI of different molecular weights (800–2000–25,000–750,000 MW PEI). In the course of the direct method, spectrophotometry and fluorometry were applied to determine the absorption and fluorescence of PEI dilution series. An increase in the MW at the same concentration produces a higher count number because of the higher number of amino groups in PEI molecules. The character of increment in fluorescence intensity is essentially different in the case of mass concentrations and molar concentrations. The increment of the fluorescence intensity related to the molar concentration is non-linear. In the case of mass concentration, the slope is linear. Moreover, their fluorescence is enhanced with the decrease in pH values. The spectrophotometry is a reliable method for measuring the quantity of PEI molecules in solution. Our data help in recognizing the detailed properties of PEI in dendrimer research.

Analysis of conditions for the preparation of BSA/MMT composites

2013 ◽  
Vol 20 (3) ◽  
pp. 221-226 ◽  
Author(s):  
Yinghai Lv ◽  
Xiaolu Su ◽  
Fuli Ren ◽  
Hong-qiang Kan ◽  
Ying Kong
Keyword(s):  
Ionic Strength ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Buffer Solution ◽  
Experimental Conditions ◽  
Ph Values ◽  
Fixation Effect ◽  
The Impact ◽  
Adsorption Quantity ◽  
Better Than

AbstractThis study describes a new method for protein fixation that has high, stable, and good repeatable fixation effect without deactivating protein. This method involves intercalating bovine serum albumin (BSA) into montmorillonite (MMT) under different experimental conditions, i.e., the concentration of coupling agent KH570, pH values, ionic strength, and the impact of buffers. The study showed the interaction of buffer systems with pH values had the most significant influence on adsorption quantity. The existence of the buffer increased the adsorption quantity and helped with slow protein releasing, while the phosphate buffer worked better than acetate buffer. More BSA was adsorbed on KH570 treated than untreated MMT, and among the treated samples the most protein released was on MMT treated with KH570 in 100% ethanol and in the acetate buffer solution. Adsorption quantity of the BSA initially increased and then decreased with the increase of the ionic strength. The research on the preparation of MMT/BSA materials provides further information on the study of protein composites.

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