Modified Eu3+ doped Y2O3 Nanoparticles as Turn-on Fluorescence Sensor for Sensitive Determination of Methamphetamine

Journal of Analytical Chemistry - In this article, a new spectrofluorometric method was developed for the determination of methamphetamine based on a turn-on luminescence response of captopril...     

Laser based fabrication of chitosan mediated silver nanoparticles

We report fabrication of silver nanoparticles (Ag NPs) by laser ablation technique in different concentrations of aqueous chitosan solution. The ablation process of silver plate was carried out by using a nanosecond Q-switched Nd:YAG pulsed laser and the characterization of Ag NPs was done by Transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction. UV-visible plasmon absorption spectra revealed that the formation efficiency as well as the stability of nanoparticles was increased by addition of chitosan. On the other hand, the size decrement of nanoparticles was more remarkable in the higher chitosan concentration.     

Fabrication of a highly sensitive electrochemiluminescence lactate biosensor using ZnO nanoparticles decorated multiwalled carbon nanotubes

ZnO nanoparticles (nanoZnO) were decorated on multiwalled carbon nanotubes (MWCNTs) and then the prepared nano-hybrids, nanoZnO-MWCNTs, were immobilized on the surface of a glassy carbon electrode (GCE) to fabricate nanoZnO-MWCNTs modified GCE. The prepared electrode, GCE/nanoZnO-MWCNTs, showed excellent electrocatalytic activity towards luminol electrochemiluminescence (ECL) reaction. The electrode was then further modified with lactate oxidase and Nafion to fabricate a highly sensitive ECL lactate biosensor. Two linear dynamic ranges of 0.01-10 μmol L⁻¹ and 10-200 μmol L⁻¹ were obtained for lactate with the correlation coefficient better than 0.9996. The detection limit (S/N = 3) was 4 nmol L⁻¹ lactate. The relative standard deviation for repetitive measurements (n = 6) of 10 μmol L⁻¹ lactate was 1.5%. The fabrication reproducibility for five biosensors prepared and used in different days was 7.4%. The proposed ECL lactate biosensor was used for determination of lactate in human blood plasma samples with satisfactory results.     

Enhanced electrochemiluminescence from luminol at multi-walled carbon nanotubes decorated with palladium nanoparticles: a novel route for the fabrication of an oxygen sensor and a glucose biosensor

Incorporation of palladium nanoparticles on the surface of multi-walled carbon nanotubes and modification of glassy carbon electrode with the prepared nano-hybrid material led to the fabrication of a novel electrode. The modified electrode showed attractive electrocatalytic activity and sensitizing effect on luminol-O(2) and luminol-H(2)O(2) electrochemiluminescence (ECL) reactions at neutral media. The sensitized luminol-O(2) and luminol-H(2)O(2) reactions were successfully applied for the ECL determination of dissolved O(2) and glucose, respectively. Under the optimal conditions for luminol-O(2) system, the ECL signal intensity of luminol was linear with the concentration of dissolved oxygen in the range between 0.08 and 0.94 mM (r=0.9996) and for luminol-H(2)O(2) system, the ECL signal intensity of luminol was linear with the concentration of glucose in the range between 0.1 and 1000 μM (r=0.9998). The limits of detection (S/N=3) for dissolved oxygen and glucose were 0.02 mM and 54 nM, respectively. The relative standard deviations (RSD) for repetitive measurements of 0.50 mM oxygen (n=10) and 10 μM glucose (n=30) were 3.5% and 0.3%, respectively. Also, under the optimal conditions for luminol-H(2)O(2) system, the ECL signal intensity of luminol was linear with the concentration of H(2)O(2) in the range between 1 nM and 0.45 mM (r=0.9997). The limit of detection (S/N=3) for H(2)O(2) detection was 0.5 nM and the relative standard deviation for repetitive measurements of 10 μM H(2)O(2) (n=10) was 0.8%.     

Elemental compositions from daughter ion spectra of m1+ and [m1 + 1]+: Some applications of the method

The elemental compositions of ions can be determined in tandem mass spectrometry by comparing the daughter ion spectra of the m₁⁺ and [m₁ + 1]⁺ ions. The method is demonstrated for mass-analyzed ion kinetic energy spectra but is applicable to all types of daughter ion spectra, including complex collisionally activated dissociation spectra. In this work, the method is applied to compounds that produce daughter ions of known elemental compositions, and the errors and limitations are evaluated. Following that test, the procedure is applied to a compound that may produce daughters of more than one possible elemental composition. The method is sometimes useful even if the formula of the parent is not known; that is, the formulae of unknown parent and daughter ions may be found. Locating a specific atom in an isotopically labeled molecule is another capability of the method. The basic equation of the method was generalized and incorporated into a computer program for performing the calculations.     

Correlating cluster size and NLO response of complexes aggregated with bifurcated metal bonds: a DFT study

In the present work, the cooperativity effect on the NLO response of clusters aggregated with bifurcated metal bonds is reported by DFT calculations at the CAM-B3LYP/6-311++G(d,p) level. Linear clusters of (LiN(CHO)₂)_1-5 and (NaN(CHO)₂)_1-5 which are connected with bifurcated metal bonds have been selected as model systems. Stabilization energies, polarizability, first hyperpolarizability, energy gap of HOMO and LUMO, and charge transfer (CT) were obtained at the same level of optimization. In the studied clusters, first hyperpolarizability is increased by cluster size and its values were obtained in ranges of 606.1–1327.4 and 1239.4–2071.1 a.u. for (LiN(CHO)₂)_1-5 and (NaN(CHO)₂)_1-5 clusters, respectively. The many-body analysis was carried out to determine two-body and many-body contributions in total interaction-induced properties. TD-DFT calculations were performed to compute the crucial electronic transitions of the related clusters. UV–vis spectra exhibit red shift due to cooperativity effects.     

Ionic Liquid Based Ultrasound-Assisted Emulsification Microextraction for Preconcentration of Phenol Using Central Composite Design

In this work, phenol reacted with 4-aminoantipyrine (4-AAP) reagent in presence of potassium hexacyanoferrate(III) and then was extracted using ultrasound-assisted emulsification microextraction via 1-hexyl-3-methyl imidazolium hexafluorophosphate as an environmentally friendly solvent. Effects of the main experimental variables were investigated and optimized by central composite design. Under the optimum conditions (pH 9.5, 100 mg/L 4-AAP, 100 μL of ionic liquid as extraction solvent, 0.2 g/L K₃Fe(CN)₆ and 0.2 M NH₄Cl) the dynamic linear range, limit of detection and relative standard deviation were obtained as 0.2?25 μg/L, 0.07 μg/L and 2.6%, respectively. Finally, the applicability of the proposed ultrasoundassisted emulsification microextraction was examined and very good results were obtained. The results confirmed the applicability of the proposed method as a versatile, low cost and sensitive preconcentration method for determination of very low concentrations of phenol in aqueous solutions.     

Micelle-mediated extraction for simultaneous spectrophotometric determination of aluminum and beryllium using mean centering of ratio spectra

A new micelle-mediated extraction method for preconcentration of ultra-trace quantities of beryllium and aluminum as a prior step to their simultaneous spectrophotometric determination has been developed. Chrome Azurol S (CAS), cetyltrimethylammonium bromide (CTAB) and Triton X-114 were used as chelating agent, cationic surfactant for extraction and co-extraction agent, respectively. Mean centering (MC) of ratio spectra has been used for simultaneous analysis of beryllium and aluminum. The optimal extraction and reaction conditions were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 5-40 ng mL⁻¹ of beryllium and 3-100 ng mL⁻¹ of aluminum. The detection limit of the method is 0.98 and 0.52 ng mL⁻¹ for beryllium and aluminum, respectively. The interference effect of some anions and cations was also tested. The method was applied to the simultaneous determination of beryllium in water samples.     

Catalytic reactions of chlorofluoroethanes at fluorinated alumina and chromia aerogels and xerogels: A comparison of reaction pathways in alumina- and chromia-based catalysts

The differences in the dynamic behaviour of 1,1,2-trichlorotrifluoroethane over fluorinated alumina or chromia catalysts at moderate temperatures are significant. Alumina-based catalysts favour the isomerization of CCl₂FCClF₂ followed by the dismutation of CCl₃CF₃ so formed. Fluorinated chromias are less selective since halogen exchange and isomerization reactions both occur. An explanation in terms of the differences in Al---X, X=Cl or F, bond energies compared with their Cr---X counterparts is suggested. The identity of the catalyst precursor has little effect in the chromium case and no effect in the case of aluminium.     

A Coordination Polymer from HAMTTO with Silver(I) (HAMTTO = 4‐Amino‐6‐methyl‐1,2,4‐triazine‐3‐thione‐5‐one)

The reaction of 4‐amino‐6‐methyl‐1,2,4‐triazine‐3‐thione‐5‐one, HAMTTO, with silver (I) nitrate in methanol led under deprotonation to the polymeric compound [(AMTTO)Ag]_n. The coordination polymer {[Ag(HAMTTO)]ClO₄}_n ( 1 ) is synthesized from the reaction of the latter polymeric compound with perchloric acid. Both compounds were characterized by elemental analysis and IR spectroscopy. Single‐crystal X‐ray diffraction studies on compound 1 showed that HAMTTO acts as a bidentate ligand and chelates the silver atom via its hydrazine nitrogen atom and its sulfur atom. Crystal data for 1 at ?90 °C: space group P2₁, Z = 2, a = 629.3(1), b = 748.7(1), c = 1071.7(1) pm, β = 98.28(1)°, R₁ = 0.0533.