Monolayer characteristics and spectroscopic study of benz(b)fluoranthene assembled in Langmuir Blodgett films mixed with stearic acid

Excellent Langmuir Blodgett (LB) films of benz(b)fluoranthene (B(b)F) have been prepared by mixing with stearic acid (SA). The surface pressure vs. area per molecule isotherms (π–A) of B(b)F mixed with SA at different mole fraction reveal that the area per molecule decreases with increasing mole fractions of B(b)F. The area per molecule vs. mole fraction shows that there is positive deviation of the experimental data to the idealized one. This indicates formation of aggregation of B(b)F molecules in the SA matrix. Spectroscopic properties of B(b)F in solution and in mixed LB films have been compared by absorption, steady state fluorescence, phosphorescence spectroscopy and lifetime measurements. Bathochromic shift in absorption and emission spectrum suggests the formation of some kind of aggregates in LB film. Decrease in fluorescence and phosphorescence lifetime is compared to that of pure B(b)F also supports the formation of different sized aggregates in the mixed film.     

Sensitive and Selective Detection of Antibiotic D-Penicillamine Based on a Dual-Mode Probe of Fluorescent Carbon Dots and Gold Nanoparticles

This paper reported a dual-mode probe for D-penicillamine on the basis of pH-mediated gold nanoparticles aggregation and fluorescence resonance energy transfer (FRET) from carbon dots. D-penicillamine is a zwitterionic compound and has different forms depending on specific pH ranges. The thiol group of D-penicillamine has high affinity towards the surface of gold nanoparticles and can replace other surface ligands. When pH values were close to its isoelectrical point (pH(I)), the D-penicillamine capped gold nanoparticles aggregated through hydrogen bonding or electrostatic interactions, resulting in the releasing of carbon dots from gold nanoparticles. The dual-mode probe consisted of fluorescent carbon dots and gold nanoparticles, and the fluorescence of carbon dots was quenched by the attached gold nanoparticles due to the FRET. Then, the fluorescence can be recovered in presence of D-penicillamine due to the gold nanoparticles aggregation in specific pH range. Under the optimum conditions, the probe has linear response for D-penicillamine in the 0.25–1.5 μM concentration range with a detection limit of 0.085 μM. This method provides a potential application in sensitive detection of D-penicillamine.     

Assembly of bioconjugated rod-nanotags and multilayer plasmonic nanorod-array for ultrasensitive SERS detection of <Emphasis Type="Italic">S. aureus</Emphasis> bacteria

A highly-efficient bioconjugation protocol of bimetallic rod-nanotags interacted with bacterial anti-S. aureus-IgG has been firstly demonstrated. Controllable fabrication of multilayer plasmonic nanorod-array (MPNRA) can be successfully obtained by facet functionalization of nanorods stacked on an activated Si/SiO₂ chip. Vancomycin coating of MPNRA is favorable to immobilize S. aureus bacteria via multiple hydrogen bonding interactions, i.e., peptidoglycan of the bacterial cell and carbonyl/amine groups of the vancomycin. Moreover, the bimetallic rod-nanotags can be assembled around MPNRA via a bacterial biointerface. Ultrasensitive SERS detection of S. aureus bacteria with limit-of-detection (LOD) can be achieved up to 17.8 cfu/mL via combination of rod-nanotag and multilayer plasmonic nanorod-array perpendicular a chip (MPNRA-perpendicular substrate), which could be ascribed to dual plasmonic enhancement from bioconjugated rod-nanotags aggregates and large-scaled plasmonic nanorod-array.     

Determination of heavy metals by inductively coupled plasma mass spectrometry after on-line separation and preconcentration

A method for the determination of Cu, As, Se, Cd, In, Hg, Tl, Pb and Bi in waters and in biological materials by inductively coupled plasma mass spectrometry, after an on-line separation, is described. The matrix separation and analyte preconcentration is accomplished by retention of the analytes complexed with the ammonium salt of O,O-diethyl dithiophosphoric acid in a HNO₃ solution on C₁₈ immobilized on silica in a minicolumn. Methanol, as eluent, is introduced in the conventional pneumatic nebulizer of the instrument. In order to use the best compromise conditions, concerning the ligand and acid concentrations, the analytes were determined in two separate groups. The enrichment factors were in the range from 5 to 61, depending on the analyte. The limits of detection varied from 0.43 ng L⁻¹ for Bi to 33 ng L⁻¹ for Cu. The sample consumption is only 2.3 mL for each group and the sampling frequency is 21 h⁻¹. The accuracy was tested by analysing five certified reference materials: water, riverine water, urine, bovine muscle and bovine liver. The agreement between obtained and certified concentrations was very good, except for As. The relatively small volume of methanol, used as eluent, minimizes the problems produced by the introduction of organic solvent into the plasma.     

Fluorescence from SF6 in highly excited vibrational states: An overview

The spectroscopy of SF₆, excited in its quasi-continuum by IR multiphoton absorption, has been recorded by IR fluorescence from ν = 700 to 1300 cm⁻¹ with a highly sensitive device. The far resonance fluorescence exhibits structures directly connected to the intramolecular couplings. A model of couplings has been developed, the parameters of which are fixed by the experimental results. The strongest couplings (orders k = 3 and 4) have a density so low that they produce only a perturbative redistribution of the ν₃ mode. The dissipative redistribution is produced by the highest orders k⩾5 and can be represented by a half-linewidth γ_d∼1.5 cm⁻¹ for E_vib∼ 15,000 cm⁻¹. The onset of the SF₆ quasi-continuum is also predicted by the model, with characteristics in full agreement with published data.     

Cyclooctatetraenyl-komplexe der frühen übergangsmetalle und lanthanoide: III. Cyclooctatetraenyl-lanthanoidtriflate und -iodide: Neue ausgangsmaterialien für die organolanthanoid-chemie

The dimeric complexes [(COT)Ln(μ-O₃SCF₃)(THF)₂]₂ (Ln  Ce (1), Pr (2), Nd (3), Sm (4)) are easily prepared by treatment of anhydrous lanthanide(III) triflates with equimolar amounts of K₂COT (COT = η⁸-cyclooctatetraenyl(2−)). The reaction of lanthanide triiodides with K₂COT affords monomeric complexes of the type (COT)Ln(I)(THF)₃ (Ln  Nd (5), Sm (6)). Due to their increased solubility in polar organic solvents these new precursors offer preparative advantages over the previously used chloro derivatives [(COT)Ln(μ-Cl)(THF)₂]₂. The molecular structures of 3 and 5 have been determined by X-ray diffraction.