Search

To investigate the optimal gold colloid film properties for the in-situ detection of polycyclic aromatic hydrocarbon (PAH) in water using 671 nm excitation wavelength, gold substrates with selected sizes of gold nanoparticles were prepared. Heating of (3-aminopropyl)trimethoxysilane (APTMS) methanol solution allowed to control the surface plasmon resonance for surface enhanced Raman spectroscopy (SERS). Shifted excitation Raman difference spectroscopy (SERDS) was applied for effective background removal. Results for pyrene in aqueous solution demonstrate that there is a dependence of SERS activity on the size of gold nanoparticles even though their surface plasmon resonances are almost same and close to the excitation wavelengths, and also confirmed that the improved self-assembly method using controlling the temperature of APTMS solution way can work well. Appling the substrate with the average gold nanoparticles size of 35 nm, different concentrations of pyrene in aqueous solution were detected with SERS supported by SERDS technique. Raman signals of pyrene up to 5 nmol/l on this substrate can be obtained. The quantitative analysis shows the SERS intensities increase with the increasing concentration of pyrene, which is the foundation of quantitative analysis of pyrene in aqueous solution.

The aim of this study was to develop further surface-enhanced Raman scattering (SERS) substrates appropriate for the in situ environmental determination of chemicals in sea-water important for global environmental problems. By encapsulating silver colloids in a sol–gel-derived xerogel, SERS-active coatings were produced with the high mechanical and chemical stability required for underwater field measurements. A flow-through system was used which simulates measurements under real flow conditions. Substrates were optimized regarding sensitivity to different analytes and long-term stability by varying solvent type, pH and sol–gel precursors. The substrates were characterized by their SERS activity and calibration functions of the Langmuir isotherm type were found for a variety of aromatic hydrocarbons. Limits of detection as low as 9 ppb for phenylacetylene and 135 ppb for biphenyl were achieved. Detailed tests on long-term stability in sea-water yielded a substrate half-life of 13 days, which resulted in a substrate lifetime of at least 5 weeks. Copyright © 2000 John Wiley & Sons, Ltd.

Abstract:: The isotope shift (IS) and hyperfine structure (hfs) of nine levels (31720 to 38921 cm-1) assigned to the configuration 4 f 12 6 s 7 s in neutral erbium have been determined experimentally using Doppler-reduced saturation absorption spectroscopy in a gas discharge. We performed a fine structure analysis in the SL-coupling scheme of the single configuration 4 f 12 6 s 7 s, confirming and extending the classification of even parity Er I levels. We discriminated the different hfs contributions of the 4f12 core and the (6 s +7 s) outer electrons of the shell in a non-relativistic JJ-coupling approach and in the relativistic effective tensor operator formalism in SL-coupling. The relativistic one-electron parameters of the hfs for 167Er were fitted to the experimental data by a least squares fit procedure: [0pt] a 01 4f =-147(3) MHz, [0pt] a 10 6s + a 10 7s =-1840(30) MHz, [0pt] b 02 4f =6560(80) MHz. The level dependencies of the isotope shift were evaluated based on crossed second order (CSO) effects. We obtained the following results for the CSO parameters for the isotope pairs 170-168Er: d 6s7s =-740(30) MHz, z 4f = 0(5) MHz, ( g 3,6s ( f , 6 s )+ g 3, 7s ( f , 7 s ))= -24(15) MHz and for 170-166Er: d 6s7s =-1500(50) MHz, z 4f =0(10) MHz, ( g 3,6s ( f ,6 s )+ g 3,7s ( f +7 s ))=-50(29) MHz. The resulting parameters for the hfs are compared with those known for other configurations of the Er atom and ion.

The rotational dependence of pressure-induced shift and broadening of H2S absorption lines in the ν2band due to collisions between H2S molecules and atoms of noble gases (He, Ne, Ar, Kr, and Xe) were studied in the spectral region between 1050 and 1325cm−1. The measurements were carried out using an improved pulse-driven diode laser spectrometer, allowing a new tuning technique of the diode laser. The parameters of this set-up will be compared to the parameters of the previously used spectrometer. The data concerning collisional broadening and shift coefficients, γand δ, respectively, and their dependencies on the rotational quantum number, J″, mass, and the polarizability, α, of the noble gases are presented for 14 P-branch transitions (3≤J″≤8), seven Q-branch transitions (7≤J″≤10), and 18 R-branch transitions (2≤J″≤11). The broadening coefficients were determined with an accuracy of 1% (3.5×10−4cm−1/atm) and shift coefficients were determined with an uncertainty of less than 5×10−4cm−1/atm for the majority of lines and broadening gases. The qualitative explanation of experimental results was made based on the models and interactions also used in the ATC and CRB theories, respectively.

To complete our study concerning lineshift in the rovibrational spectrum of 14N16O2, a pulse-driven three-channel lead salt diode laser spectrometer was applied to record high-resolution spectra at room temperature in the 6.2-μm region corresponding to the ν3band at low NO2concentrations. The shift was studied for collisions with the noble gases He, Ne, Ar, Kr, and Xe. This paper extends our recently published data in order to analyze the quantum number dependence of the shift effect more precisely. Therefore, in this paper, additionally eight unresolved NO2doublets covering an enlarged quantum number range (10 ≤ N″≤ 34, 2 ≤ K″a≤ 6) were studied. For all doublets, shift coefficients δNO2–noble gasand additionally broadening coefficients γNO2–noble gaswere determined. Hereby, the experimental data confirm general trends published recently. In this study, in the case of broadening for the lighter rare gases helium, neon, and argon, only a slight decrease of γNO2–noble gaswas observed, whereas for the rare gases with a higher atomic weight, i.e., krypton and xenon, a pronounced decrease of γNO2–noble gaswith increasing rotational quantum number N″occurred. All measured lineshift coefficients were negative. The absolute value of the determined lineshift coefficient ‖δNO2–noble gas‖ increases with the mass of the noble gas perturber, i.e., ‖δNO2–He‖ < ‖δNO2–Ne‖ < ‖δNO2–Ar‖ < ‖δNO2–Kr‖ < ‖δNO2–Xe‖. Within the studied quantum number range, an increase ‖δNO2–noble gas‖ with increase of N″was observed. A typical trend of the shift and broadening data on the quantum number K″awas not observed.

A high-resolution three-channel diode-laser spectrometer was used to record a large number of spectra with 14N16O2and foreign gas pressures ranging from 0.1 to 0.4 and 20 to 150 Torr, respectively, at room temperature. The 6.2-μm region corresponding to the ν3band of NO2was analyzed and the broadening and shift coefficients were derived in the case of collisions between NO2and H2, D2, O2, N2, CO2, and SO2for 13 lines with 18 ≤ N″ ≤ 38 and 1 ≤ K″a≤ 5. This experimental study confirms general trends. The broadening coefficients decrease with an increase of the rotational quantum number N″ whereas the absolute values of the line-shift coefficient increase with increasing N″.In the case of the studied diatomic perturbers the size of the broadening coefficients corresponds to the size of the quadrupole moments. The only collision partner with nonvanishing dipole moment, SO2, shows the largest broadening effect as expected. All shift coefficients are negative for the lines under study.