Laser Based Optical Emission Studies of Zinc Oxide (ZnO) Plasma

We present the optical emission characteristics of the zinc oxide (ZnO) plasma produced by the first (1,064 nm) and second (532 nm) harmonics of a Q switched Nd: YAG laser. The target material was placed in front of laser beam in air (at atmospheric pressure).The experimentally observed line profiles of neutral zinc (Zn I) have been used to extract the electron temperature using the Boltzmann plot method, whereas, the electron number density has been determined from the Stark broadening. The electron temperature is calculated by varying distance from the target surface along the line of propagation of plasma plume and also by varying the laser irradiance. Beside we have studied the variation of number density as a function of laser irradiance as well as its variation with distance from the target surface. It is observed that electron temperature and electron number density increases as laser energy is increased.     

用可见激光在聚(氨酯-酰亚胺)表面制备周期性亚微米结构

由于含有偶氮苯染料侧基,聚(氨酯-酰亚胺)(PUI)对532nm的光具有较强的吸收.采用该波长的可见偏振脉冲激光(Nd∶YAG激光器的倍频输出),在PUI薄膜表面制备了激光诱导周期性表面微结构(LIPSS).研究了染料引入方式以及染料侧基含量对微结构形成过程的影响,讨论了入射角、激光脉冲数、激光脉宽等激光辐射条件对LIPSS形成过程以及对微结构形貌和周期性的影响.     

Growth and characterization of organic nonlinear optical crystal of 1-chloro-2,4-dinitrobenzene (CDNB)

Organic nonlinear optical crystal of 1-chloro-2,4-dinitrobenzene has been successfully grown by low temperature solution growth technique. Good optical quality single crystals of size 28 mm x 11 mm x 5mm are obtained. Grown crystals were subjected to X-ray powder diffraction analysis, FT-IR, FT-Raman, proton nuclear magnetic resonance (PNMR) and etching studies. Thermal properties of the grown crystals were studied by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). UV-vis studies show the cutoff wavelength is less than 400 nm. Nonlinear optical property of the crystal was studied by Kurtz powder technique using Nd:YAG laser and the crystal exhibits second harmonic generation property.     

Effect of Laser Pulse Energy on the Characteristics of Cu Nanoparticles Produced by Laser Ablation Method in Acetone

The effect of laser fluence on the characteristics of Cu nanoparticles, prepared by laser ablation method, is investigated experimentally. 1–6 nm Cu nanoparticles were synthesized by the pulsed laser ablation of a high purity copper bulk in acetone. Effect of laser fluence on the size, morphology and structure of produced nanoparticles has been studied. Pulses of a Q-switched Nd:YAG laser of 1,064 nm wavelengths at 7 ns pulse width at different fluences was employed to irradiate the Cu target in acetone. The UV–Vis–NIR absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the visible region. TEM and SEM micrographs indicate that with increasing the laser fluence the average size of spherical Cu nanoparticles is decreased and only the sample which is produced with the highest fluence shows exceptional behavior. It is found that Cu nanoparticles exhibit photoluminescence emission with single peak due to its interband transition.     

4,5-二(2',4'-二硝基苯硫基)-1,3-二硫杂环戊烯-2-酮的合成, 晶体结构及其激光倍频性质

首次合成了具有激光倍频性质的BNPT-DTO,并测定了结构.BNPT-DTO是电子给体-受体型手性分子,它的两个苯环几乎与二硫杂环戊烯的平面垂直,用1064nm YAG:Nd激光照射晶体产生532nm的倍频光,其强度与KDP的倍频光强度相当     

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry of polychlorinated biphenyls

A sample mixture of polychlorinated biphenyls (PCBs) was measured by gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) using four types of laser sources. When a fourth harmonic emission (266 nm) of a picosecond Nd:YAG laser (1064 nm) was utilized, highly chlorinated PCBs larger than hepta-CBs were not observed. A fifth harmonic emission (213 nm) of the picosecond Nd:YAG laser allowed the measurement of PCBs from di-CBs to octa-CBs, and the limit of detection (LOD) was several pg for each component of PCBs. The LOD for the total amount of PCBs, which was calculated using the protocol provided by the Ministry of the Environment, Japan, was 1000 pg. The signal intensity of the congeners with chlorine atoms at the ortho positions (non-coplanar PCBs) was enhanced by using the fifth harmonic emission. When the fourth harmonic emission remaining after fifth harmonic generation was simultaneously used, the LOD for total PCBs was improved to 667 pg. The PCB sample was also measured using a third harmonic emission (267 nm) of a femtosecond Ti:sapphire laser (800 nm), providing an LOD of 677 pg. Thus, the two-color beam (266/213 nm) of a picosecond Nd:YAG laser had a comparable, or even slightly superior, performance to the more expensive femtosecond Ti:sapphire laser.     

Laser photolysis of silver colloid prepared by citric acid reduction method

By irradiating a silver colloid, prepared via the citric reduction method, using the second harmonic of a Nd:YAG laser, lambda = 532 nm, with laser fluence more than about 0.2 J/cm(2), we prepared a colloid consisting of small spherical silver nanoparticles with d(p) = 8 nm. The process of particle formation can be divided into three steps. First, large particles that existed in the initial colloid evaporate fully, producing a large amount of silver atoms. Next, primary particles with d(p) = 2-4 nm are formed in mini plumes. Finally, these primary particles grow up to 8 nm, as silver atoms diffuse to them through water.     

Photogeneration of Benzhydryl Cations by Near-UV Laser Flash Photolysis of Pyridinium Salts

Laser flash irradiation of substituted N-benzhydryl pyridinium salts yields benzhydryl cations (diarylcarbenium ions) and/or benzhydryl radicals (diarylmethyl radicals). The use of 3,4,5-triamino-substituted pyridines as photoleaving groups allowed us to employ the third harmonic of a Nd/YAG laser (355 nm) for the photogeneration of benzhydryl cations. In this way, benzhydryl cations can also be photogenerated in the presence of aromatic compounds and in solvents which are opaque at the wavelength of the quadrupled Nd/YAG laser (266 nm). To demonstrate the scope and limitations of this method, the rate constants for the bimolecular reactions of benzhydryl cations with several substituted pyridines were determined in acetonitrile and with water in acetone. The obtained data agree with results obtained by stopped-flow UV-vis spectroscopic measurements. The rate constants for the reaction of the 4,4'-bis[methyl(2,2,2-trifluoroethyl)amino]benzhydrylium ion with 4-(dimethylamino)pyridine were also determined in dimethyl sulfoxide, N,N-dimethylformamide, and acetone. From the second-order rate constants, we derived the nucleophilicity parameters N and s(N) for the substituted pyridines, as defined by the linear free energy relationship, log k(2) = s(N)(N + E).     

Spatial determination of elements in green leaves of oak trees (Quercus robur) by laser ablation-ICP-MS

Laser ablation inductively coupled plasma mass spectrometry (laser ablation-ICP-MS) has been applied to the spatially resolved determination of the elements Mg, Ca, Cu, Ni, Ba, Al, Pb, Sr and Mn in green leaves of oak trees. Instrument operating parameters such as the laser wavelength and the pulse energy have been optimized to provide the sensitivity and reproducibility required for the analysis. The method provides spatial resolution down to 300 microm with the use of the 355 nm wavelength (3rd harmonic of the 1,064 nm Nd:YAG laser wavelength) and the pulse energy of 50 mJ. Plant standards and cellulose, doped with multi element solution standards, dried and pressed to pellets were used as calibration samples. To compensate for signal fluctuations caused by the variation of the ablated sample mass 13C was used as a "natural" internal standard. The accuracy of the calibration was verified with selected samples analyzed by ICP-MS (high pressure digestion, 170 degrees C, 10(7) Pa, HNO3, 2 h) and by laser ablation-ICP-MS. Recovery rates between 93% (Cu) and 108% (Mn) were obtained. Leaves taken from oak trees (Quercus robur) were analyzed.     

Studies on the growth, spectral, optical, and thermal aspects of a NLO crystal

Nonlinear optical single crystal l-tryptophan hydrogen selenite (LTHS) has been synthesized by slow evaporation solution growth technique from aqueous solution at ambient temperature. The grown nonlinear optical crystals were subjected to single crystal XRD analysis to find the structure parameters. The formation of the product was confirmed from the FTIR and ¹HNMR spectral analysis. The UV–Vis spectral studies showed that the cutoff wavelength for LTHS was less than 400 nm. The thermal behavior of the grown crystals was investigated from thermogravimetry and differential thermal analysis. Its nonlinear optical property has been tested by Kurtz–Perry powder technique using Nd:YAG laser, and the crystal exhibited second harmonic generation property.     

Study of Optical Properties of <Emphasis Type="Italic">Macrophomina phaseolina</Emphasis> Impregnated Sol-gel Derived Silica Matrices

In the present frame of work, Macrophomina phaseolina is encapsulated in silica matrices at various concentrations by low temperature sol-gel technique using tetraethylorthosilicate (TEOS) as precursor. The optical and photophysical properties of these samples have been studied by second harmonics of Nd:YAG laser at 532 nm. UV-visible absorption spectra of samples have been recorded and it is found that the absorption increases with increase in concentration of fungus. Further, a decrease in output transmission intensity of the laser has been observed with increase in fungus concentration. The temporal response of these samples has also been examined. The results show that the fungus concentration can be measured within ∼15–20 min. This method of optical sensing of fungus in test sample is faster than other techniques, such as the conventional colorimetric method which takes about 1 h.     

Laser induced breakdown spectrometry of vanadium in titania supported silica catalysts

The capability of laser induced breakdown spectrometry (LIBS) for vanadium determination in a xV-2TiO(2)-SiO(2) catalyst is presented. The microplasma was generated onto the sample surface using a pulsed Nd:YAG laser operating in the second harmonic (532 nm). Laser produced plasmas were collected and detected using a charge-coupled device (CCD). In order to minimize the complex spectral interferences of emission lines and matrix effects a wide spectral range (210-660 nm) was studied. The focusing of the laser beam on the surface was optimized to improve the signal-to-background ratio, and consequently the limit of detection. The analytical lines selected were used to evaluate the calibration curve. The detection limit for V was estimated to be 38 mug g(-1) in 2TiO(2)-SiO(2). The method precision expressed as relative standard deviation (RSD) was better than 6% in the concentration range 200-1000 mug g(-1).     

Basic investigations for laser microanalysis: IV. The dependence on the laser wavelength in laser ablation

The fourth harmonic wavelength at 266 nm as well as the fundamental radiation at 1.06 m of a pulsed Nd: YAG laser has been used for ablation of solid samples. Using different buffer gases and different samples, the ablated masses and plasma temperatures obtained with the two different laser wavelengths are compared. The analytical application of 266-nm laser pulses is studied by the measurement of aluminium and manganese in steel and boraxglass (Na₂B₄O₇) samples.     

Post-source decay of alkylated and functionalized polycyclic aromatic compounds

Post-source decay (PSD) is a valuable tool for providing structural information from large molecules by time-of-flight mass spectrometry (TOFMS). We used PSD to obtain this type of data from small molecules in the laser desorption/ionization (LDI) study of diesel engine exhaust particles. As the original nitrogen laser (lambda = 337 nm, E = 3.5 eV/photon) of our TOF mass spectrometer does not yield sufficient energy to ionize polycyclic aromatic hydrocarbons (PAHs), a second laser with a shorter wavelength has been coupled to the instrument. The fourth harmonic of a Nd:YAG laser (lambda = 266 nm, 4.6 eV/photon) has been chosen to achieve two-photon single-step desorption/ionization of PAHs. The PSD fragmentation of functionalized, alkylated and sulfur PAHs is discussed. Diesel engine exhaust particles are also studied as an example of a real complex sample. This technique is presented herein as a way to identify small molecules in environmental samples. Information provided by LDI-PSD-TOFMS can be a way to distinguish pollutants with very close molecular weights even if the resolving power of a TOF mass spectrometer is not sufficient.     

金属硫氰酸根配合物FeHg(SCN)~4, MnHg(SCN)~4的合成、晶体结 构与非线性光 学性质的研究

合成了配合物晶体FeHg(SCN)~4和MnHg(SCN)~4。用单晶X射线衍射方法测定了这两个晶体的结构。以尿素为标准样品用粉末晶体倍频1064nm的Nd:YAG激光,测得其倍频光强度分别为:FeHg(SCN)~4,0.6倍于尿素;MnHg(SCN)~4,50倍于尿素,后者显示了作为新的非线性光学材料的发展前景。     

金属硫氰酸根配合物FeHg(SCN)_4,MnHg(SCN)_4的合成、晶体结构与非线性光学性质的研究

合成了配合物晶体FeHg(SCN)_4和MnHg(SCN)_4用单晶X射线衍射方法测定了这两个晶体的结构.以尿素为标准样品用粉末晶体倍频1064nm的Nd:YAG激光,测得其倍频光强度分别为:FeHg(SCN)_4,0.6倍于尿素;MnHg(SCN)_4,50倍于尿素.后者显示了作为新的非线性光学材料的发展前景.     

Growth, structural, vibrational, optical, laser and dielectric aspects of L-alanine alaninium nitrate single crystal

Bulk single crystals of l-alanine alaninium nitrate [abbreviated as LAAN], an intriguing material for frequency conversion has been grown from its aqueous solution by both slow solvent evaporation and by slow cooling techniques. The optimized pH value to grow good quality LAAN single crystal was found to be 2.5. The grown crystals were subjected to single crystal X-ray diffraction studies to determine the unit cell dimensions and morphology. Vibrational frequencies of the grown crystals by Fourier transform infrared spectroscopic technique were investigated. Also, the presence of hydrogen and carbon atoms in the grown sample was confirmed using proton and carbon NMR analyses. The dielectric constant and dielectric loss measurements of the as grown crystal at different temperatures and frequencies of the applied field are measured and reported. LAAN has good optical transmission in the entire visible region with cutoff wavelength within the UV region confirms its suitability for device fabrications. The existence of second harmonic generation signals was observed using Nd:YAG laser with fundamental wavelength of 1064 nm. Its Laser Damage Threshold (LDT) was measured and also tested by using a Q-switched Nd:YAG laser and the value of LDT of LAAN is 17.76GW/cm2 respectively, is found to be better than certain organic and semiorganic materials.     

Spatial determination of elements in green leaves of oak trees (Quercus robur) by laser ablation-ICP-MS

Laser ablation inductively coupled plasma mass spectrometry (laser ablation-ICP-MS) has been applied to the spatially resolved determination of the elements Mg, Ca, Cu, Ni, Ba, Al, Pb, Sr and Mn in green leaves of oak trees. Instrument operating parameters such as the laser wavelength and the pulse energy have been optimized to provide the sensitivity and reproducibility required for the analysis. The method provides spatial resolution down to 300 μm with the use of the 355 nm wavelength (3rd harmonic of the 1064 nm Nd:YAG laser wavelength) and the pulse energy of 50 mJ. Plant standards and cellulose, doped with multi element solution standards, dried and pressed to pellets were used as calibration samples. To compensate for signal fluctuations caused by the variation of the ablated sample mass ¹³C was used as a “natural” internal standard. The accuracy of the calibration was verified with selected samples analyzed by ICP-MS (high pressure digestion, 170?°C, 10⁷ Pa, HNO₃, 2 h) and by laser ablation-ICP-MS. Recovery rates between 93% (Cu) and 108% (Mn) were obtained. Leaves taken from oak trees (Quercus robur) were analyzed.     

Comparison of Single Pulse and Double Simultaneous Pulse Laser Induced Breakdown Spectroscopy

A simple and cost-effective variant of laser induced breakdown spectroscopy is presented that involves a double simultaneous pulse configuration employing a single laser source. Its performance is compared with conventional single pulse configuration. Double simultaneous pulses were accomplished by splitting a Nd:YAG laser (1064 nm, 6 ns, 360 mJ) beam into two components that were focused on the sample surface to produce two concurrent breakdowns. Experiment was repeated for single pulse and double simultaneous pulses under different ambient pressures. The performance was evaluated on the basis of self-absorption, signal-to-noise ratio (SNR), and relative standard deviation (RSD) of the Mg II doublet (280.2704 nm, 279.553 nm). Optically thin emission lines of better profiles with higher signal-to-noise ratio resulted from double simultaneous pulses. The lowest relative standard deviations obtained by single pulse and double simultaneous pulse configurations were 18.89% and 12.01%, respectively. In fact, double simultaneous pulses have performed better than single pulse in all respects within the studied regime.     

Time-resolved laser-induced plasma spectrometry for determination of minor elements in steelmaking process samples

A pulsed Nd:YAG laser operating on the fourth (266 nm) and second (532 nm) harmonics has been used to generate plasmas on the target surface in air at atmospheric pressure. The influence of wavelength on quantitative analysis of 4 minor elements in stainless steel samples (Si, Ti, Nb and Mo) was investigated. Stainless steel samples with different elemental concentrations were prepared and analyzed by laser-induced plasma spectrometry (LIPS). The effect of laser wavelength on analytical figures of merit (calibration curves, correlation coefficients, linear dynamic ranges, analytical precision, and accuracy values) was found to be negligible when internal standardization (an Fe line) and time-resolved laser-induced plasma are employed. For both wavelengths, the calibration curves presented a good linearity and an acceptable linear dynamic range in the concentration interval investigated. For the four elements studied, limits of detection lower than 150 microg g(-1) were achieved. To evaluate the influence of wavelength on precision and accuracy, a set of fifteen high-alloyed steel samples from different stages of steelmaking process have been analyzed. Finally, the long-term stability of the analytical measurements for Mo with 532 nm wavelength has been discussed. RSD values were lower than 5.3% for the elements studied.