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.     

Growth, structural, spectral, mechanical, thermal and dielectric characterization of phosphoric acid admixtured L-alanine (PLA) single crystals

Phosphoric acid admixtured L-alanine (PLA) single crystals were grown successfully by solution method with slow evaporation technique at room temperature. Crystals of size 18 mm×12 mm×8 mm have been obtained in 28 days. The grown crystals were colorless and transparent. The solubility of the grown samples has been found out at various temperatures. The lattice parameters of the grown crystals were determined by X-ray diffraction technique. The reflection planes of the sample were confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. Fourier transform infrared (FTIR) studies were used to confirm the presence of various functional groups in the crystals. UV-visible transmittance spectrum was recorded to study the optical transparency of grown crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz-Perry powder technique and a study of its second harmonic generation efficiency in comparison with potassium dihydrogen phosphate (KDP) has been made. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to thermo gravimetric and differential thermal analysis (TG/DTA). The dielectric behavior of the sample was also studied.     

Investigation on the growth and characterization of nonlinear optical single crystal of bis thiourea iron(II) sulphate

Single crystal of bisthiourea iron(II) sulphate was grown by slow evaporation technique at 303?K. The structural properties of the grown crystals were characterized by FTIR spectroscopy, UV spectroscopy and powder X-ray diffraction. FTIR and UV spectra provide information about the presence of functional groups. Thermal analysis confirms the crystal is thermally stable up to 167.02?°C.     

Growth and characterization of a new metal-organic nonlinear optical bis (thiourea) cadmium zinc chloride single crystals

A new semiorganic nonlinear optical bis (thiourea) cadmium zinc chloride (BTCZC) crystal has been synthesized. BTCZC single crystals were grown from aqueous solution by slow evaporation technique. The solubility of BTCZC has been determined for various temperatures. Single crystal X-ray diffraction (XRD) study has been carried out to identify the lattice parameters. Fourier transform infrared (FTIR) studies confirm the various functional groups present in the grown crystal. The transmission and absorption spectra of this crystal show that the lower cut off wavelength lies at 260nm. The thermal analyses confirmed that the crystal is stable upto 201 degrees C. The nonlinear optical (NLO) property of the grown crystal has been confirmed by Kurtz-powder second harmonic generation (SHG) test.     

Crystal growth, structural, optical, spectral and thermal studies of tris(L-phenylalanine)L-phenylalaninium nitrate: a new organic nonlinear optical material

Tris(L-phenylalanine)L-phenylalaninium nitrate, C(9)H(12)NO(2)(+)·NO(3)(-)·3C(9)H(11)NO(2) (TPLPN), a new organic nonlinear optical material was grown from aqueous solution by slow evaporation solution growth at room temperature. The grown crystals were subjected to powder X-ray diffraction and single crystal X-ray diffraction studies to confirm the crystalline nature and crystal structure. The modes of vibration of different molecular groups present in TPLPN have been identified by FTIR spectral analysis. The presence of hydrogen and carbon in the grown crystal were confirmed by using proton and carbon nuclear magnetic resonance (NMR) spectral analyses. The optical transmission spectral study establishes good transmitting ability of the crystal in the entire visible region. The thermogravimetric (TG) and differential thermal analyses (DTA) were carried out to understand the thermal stability of the sample. The nonlinear optical property of the compound observed using Kurtz powder second harmonic generation test assets the suitability of the grown material for the frequency conversion of laser radiation of Nd:YAG.     

Theoretical and experimental study of valence photoelectron spectrum of D,L-alanine amino acid

In this work, the He-I (21.218 eV) photoelectron spectrum of D,L-alanine in the gas phase is revisited experimentally and theoretically. To support the experiment, the high level ab initio calculations were used to calculate and assign the photoelectron spectra of the four most stable conformers of gaseous alanine, carefully. The symmetry adapted cluster/configuration interaction (SAC-CI) method based on single and double excitation operators (SD-R) and its more accurate version, termed general-R, was used to separately calculate the energies and intensities of the ionization bands of the L- and D-alanine conformers. The intensities of ionization bands were calculated based on the monopole approximation. Also, natural bonding orbital (NBO) calculations were employed for better spectral band assignment. The relative electronic energy, Gibbs free energy, and Boltzmann population ratio of the conformers were calculated at the experimental temperature (403 K) using several theoretical methods. The theoretical photoelectron spectrum of alanine was calculated by summing over the spectra of individual D and L conformers weighted by different population ratios. Finally, the population ratio of the four most stable conformers of alanine was estimated from the experimental photoelectron spectrum using theoretical calculations for the first time.     

Synthesis, growth and characterization of a new nonlinear optical material: 4-phenylpyridinium hydrogen squarate (4PHS)

A novel organic non-linear optical organic single crystal of 4-phenylpyridinium hydrogen squarate (4PHS) has been synthesized and successfully grown from aqueous solutions by slow evaporation solution growth method. In the present investigation the title compound has been synthesized by taking equimolar quantity of 4-phenylpyridine and squaric acid and mixed thoroughly using double distilled water as the solvent. The prepared concentrated solution was placed in an undisturbed condition, and then the solution was periodically inspected. The good quality single crystals have been harvested in a time span of 3 weeks. Then the grown crystal was characterized as single crystal XRD, differential thermal analysis, thermogravimetric analysis, FTIR, UV-vis-NIR, SHG, (1)H NMR and (13)C NMR analyses, respectively. The observed results from the characterization analyses show its suitability for NLO applications when compared with some of the existing organic crystals. The relative second harmonic generation of this grown crystal was found to be five times higher than that of KDP crystal. The UV cut-off wavelength and decomposition temperature of this grown crystal were also comparatively better. (1)H NMR and (13)C NMR spectroscopic studies were employed to elucidate the structure of the grown specimen.     

Dinuclear chromium(V) amino acid complexes from the reduction of chromium(VI) in the presence of amino acid ligands: XAFS characterization of a chromium(V) amino acid complex

The first synthesis and characterization of Cr(V) complexes of non-sulfur-containing amino acids are reported. The reduction of Cr(VI) in methanol in the presence of amino acids glycine, alanine, and 2-amino-2-methylpropanoic acid (alpha-aminoisobutyric acid, Aib) yielded several Cr(V) EPR signals. For the reaction involving glycine, the only Cr(V) EPR signals detected were those of the Cr(V)-intermediate methanol complexes, which were also observed in the absence of amino acids. The reaction involving alanine yielded one Cr(V) signal with a g(iso) value of 1.9754 (a(iso) = 4.88 x 10(-4) cm(-1) and A(iso)(53Cr) = 17.89 x 10(-4) cm(-1)). However, a solid product isolated from the reaction solution was EPR silent and was characterized as a dioxo-bridged dimeric species, [Cr(V)2(mu-O)2(O)2(Ala)2(OCH3)2](2-), by multiple-scattering XAFS analysis and electrospray mass spectrometry. The EPR spectrum of the reduction reaction of Cr(VI) in the presence of Aib showed several different Cr(V) signals. Those observed at lower g(iso) values (1.9765, 1.9806) were assigned to Cr(V)-methanol intermediates, while the relatively broad six-line signal at g(iso) = 2.0058 was assigned as being due to a Cr(V) complex with coupling to a single deprotonated amine group of the amino acid. This was confirmed by simplification of the superhyperfine coupling lines from six to three when the deuterated ligand was substituted in the reaction. The reduction of Cr(VI) with excess alanine or Aib ligands resulted in the formation of tris-chelate Cr(III) complexes, which were analytically identical to complexes formed via Cr(III) synthesis methods. The fac-[Cr(Aib)3] complex was characterized by single-crystal X-ray diffraction.     

A comparative study on the nitrate determination in airborne dust

Summary Two analytical methods for determination of nitrate in airborne dust samples — spectrophotometry and direct potentiometry with ionselective electrodes — are compared. Different aerosol samples collected by an impaction cascade device and a high-volume filter sampler and model powdered dust samples were analysed. It was shown that direct potentiometry is quite satisfactory for nitrate determination irrespective of collecting technique if the known addiMikrochim. Acta 1977 II-6 tion procedure is used. The spectrophotometric determination of impaction-collected aerosol samples suffers from interference by the copper foil used for collection. The advantage of the spectrophotometric method is that concentrations as low as 0.25g/ml can be determined reliably. The advantage of potentiometry is that it gives a simple analytical technique for samples containing down to 1 ppm NO₃ ^– and it can readily be automated.

---

Zusammenfassung Zur Bestimmung von Nitrat in Staubproben wurden die UV-Spektrophotometrie und die Direkt-Potentiometrie mit ionenselektiven Elektroden verglichen. Die Untersuchung erfolgte an standardisierten Staubproben und an Proben, die mit High Volume Filter Samplern (Sartorius) und mit Kaskadenimpaktoren gesammelt worden waren. Die Direktpotentiometrie konnte bei alien mit verschiedenen Methoden gesammelten Stauben erfolgreich mit einem Standardadditionsverfahren eingeScizt werden. Die UV-spektrophotometrische Methode konnte bei den Impaktorproben nicht eingeScizt werden, da die Sammlung auf Kupferfolien erfolgte und Kupfer die Bestimmung stört. Der Vorteil der UV-Spektrophotometrie liegt in der Bestimmung sehr kleiner Nitratmengen (bis 0,25g/ml). Der Vorteil der ionenselektiven Elektroden liegt hingegen in der einfachen analytischen Vorgangsweise bei Proben bis zu 1 ppm Nitrat.

---

---

On leave from Faculty of Chemistry, University of Sofia, Sofia, Bulgaria.     

A comparative study of the nonlinear optical properties of molecular J- and H-aggregates in thin films

A comparative study of the dispersion of nonlinear absorption in thin films of molecular J- and H-aggregates of polymethine dyes was performed with the use of the Z-scan (Z-scan technique) over the range 625–825 nm under conditions close to resonance absorption at nanosecond duration of excitation. The measurements were made on film samples of J- and H-aggregates prepared by spin-coating and having identical absorption spectra. The H- and J-aggregates were formed by the synthetic thioflavylium DT-3 and benzothiazole BTC18H dyes, respectively. It was found that the samples of different types of aggregates exhibit nonlinear susceptibility of the same order of magnitude with allowance for the width of exciton absorption peaks.     

Factor group analysis and hyperpolarizability studies of nonlinear optical L-asparaginium picrate (LASP) crystals

The factor group analysis and the hyperpolarizability study were carried out for the L-asparaginium picrate (LASP) single crystals to explore the possible vibrational modes and the microscopic nonlinearity by the density functional triply parameter hybrid model DFT/B3LYP using GAUSSIAN 98W, respectively. The HF/6-31G (d,p) basis set has been employed. The calculated first order hyperpolarizability of LASP is 4.815 x 10(-29)esu. The Fourier transform infrared (FTIR) spectroscopic studies were performed for identifying different functional groups present in the compound.     

Electrosynthesis,characterization and optical sensing application of amino acid functionalized polyfluorene

An amino acid side chain functionalized polyfluorene derivative poly[N-(9-fluorenylmethoxycarbonyl)-glycine](P9FG) was facilely electrosynthesized and characterized, and the structure, properties and optical sensing application of the obtained polymer were described and discussed. The electropolymerization occurred at C2 and C7 positions of fluorene units, and amino acid side chain groups were not cleaved from polyfluorene backbone in mixed electrolytes of boron trifluoride diethyl etherate and dichloromethane. Thermal analysis demonstrated good thermal stability of P9 FG. Fluorescent spectra indicated that P9 FG was a good blue light emitting material that could be employed as optical sensors. The soluble P9 FG as a turn-off fluorescent sensor could realize the detection of Fe3+, Cu2+ and Cr2O72?, respectively. In addition, P9 FG as a turn-off ultraviolet sensor could realize the detection of Cu2+ while as turn-on ultraviolet sensors could also realize the determination of Fe3+ and Cr2O72?, respectively. All results indicate that P9 FG is a promising candidate for optical sensing.     

Synthesis growth and characterization of L-Valinium Picrate a new nonlinear optical crystal

New nonlinear optical (NLO) single crystal of l-Valinium Picrate (LVP) was grown by slow evaporation solution growth technique at room temperature. The cell parameters of the grown crystal were estimated by single crystal X-ray diffraction analysis. The presence of functional groups was identified from Fourier transform infrared spectrum. The transmission and absorption spectra of this crystal show that the lower cut-off wavelength lies at 380nm. Thermal analysis was performed to study the thermal stability of the grown crystal. The powder second harmonic generation efficiency of the grown crystal measured by Kurtz technique is 2 times efficient of Potassium dihydrogen orthophosphate (KDP).     

A comparative study of HPLC and TLC separation of amino acids using Cu(II) ion

Separation of amino acids using Cu(II) by RP-HPLC and impregnated TLC is reported. For HPLC the sample mixture of amino acids containing copper (II) was injected into the column while for TLC the silica gel plates were impregnated with Cu(II). The mobile phase used in HPLC was acetate buffer (0.3 M , pH 6.0)-acetonitrile (9:1, v/v), and that in TLC was acetate buffer (0.3 M , pH 6.0):acetonitrile-n-butanol (12:5:10, by vol.). The results have been compared and discussed.     

不对称二苯乙炔系列衍生物的二阶非线性光学性质的ZINDO-SOS 研究

在ZINDO方法基础上,按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数β~i~j~k,β~μ的程序;研究了不对称二苯乙炔系列衍生物的结构和非线性光学性质;计算了不对称二苯乙炔系列衍生物的UV光谱,偶极矩,β~μ,β~0,μβ,μβ~0,及激发态电荷转移;考察了分子共轭链长、给电子基团对β~μ的影响。并对上述结果在微观上给予了解释。     

Selective and direct detection of free amino acid using the optical birefringent patterns of confined nematic liquid crystals

Detection of amino acid (AA) is an essential step to understand various biological processes. In this study, we used innovative optical birefringent patterns of nematic liquid crystals (LCs) for the detection of several AAs. We attempted to use capillary-confined nematic LCs as sensor for AA analysis because their three-dimensional micro-scale architecture of LCs allowed better performance than that of mainly reported LC thin film sensors owing to the effect on the formation and dynamics of point defect. The sensing system was built by disrupting the alignment of a nematic LC, 4-cyano-4′-pentylbiphenyl (5CB), using the dopant of dodecyl aldehyde. Detection principle is based on the chemical analytical method of aldehyde titration for AAs, wherein the reaction between AAs and aldehyde group generates Schiff bases that could alter the configuration of nematic LCs at the aqueous/LC interface. The patterns generated in the reaction are captured by polarising optical microscopy (POM) and are visible to the naked eye. The functionalised LCs detected glycine at concentrations as low as 1 pM. There was a surprising result that it can selectively detect D-AAs against their L-isomers, however, further efforts are required to explain the mechanism.     

Growth and characterization of nonlinear optical material: l-alanine thiourea

The title compound of l-alanine thiourea, a semi organic material, has been grown from slow evaporation solution growth technique at room temperature. It is a potential material for nonlinear optical applications. The grown single crystals have been analyzed using powder X-ray diffraction. It belongs to monoclinic crystal system, and its lattice dimensions were determined. The presence of functional groups was identified from FTIR spectral analysis. The title compound has good optical transmission in the entire visible region. Thermal stability of the grown crystal was investigated by thermogravimetric and differential thermal analysis.