UV Vis NIR Spectrum Research Articles

Synthesis and chiroptical properties of water-processable polyaniline using methylcellulose as a molecular template

Optically active polyaniline (PANI) was synthesized using methylcellulose (MC) as a stabilizer and molecular template in HCl solution, in which ammonium persulfate was used as an oxidant; that is, the optical activity (helical conformation) was successfully induced into PANI by a water-soluble, non-ionic polymer. The synthesized PANI–MC composite was investigated by UV–VIS–NIR, FTIR, TGA and circular dichroism (CD) measurements. The UV–VIS–NIR spectra indicated that the characteristic peaks of PANI were existed in the as-synthesized, purified PANI–MC dispersion and the film of PANI–MC. FTIR spectra and TGA thermograms also suggested the interaction between PANI and MC. Most importantly, the bisignate CD bands of PANI–MC in water at ca. 395 and 459 nm were found to be consistent with that of optically active PANI doped with optically active polymeric acid derivatives. When the PANI–MC film was heat treated with increasing temperature, the CD spectrum indicated that the intensity almost unchanged until 120 °C, although there is a progressive dedoping while heating progress. In addition, PANI was still kept the emeraldine salt form even after heating the film to 200 °C for 10 min. The effect of addition of urea on the synthesizing PANI–MC aqueous dispersion was also investigated; the CD band of PANI–MC was decreased with increasing the urea concentration. Optically active PANI–MC also can disperse in various organic solvents, such as methanol, ethanol, DMF, DMSO and NMP. The CD spectra of PANI–MC indicated loss of its characteristic bisignate CD band and a weaken band exists at ca. 460 nm in each of these organic solvents. It means that the conformation of optically active PANI–MC was obviously changed and almost lost its optical activity. And it also exhibited that the optical activity of the water-processable PANI–MC was sensitive to the environment of solvents.

Growth and characterization of 2-amino-5-chlorobenzophenone (2A-5CB) single crystals

Organic nonlinear optical single crystals of 2-amino-5-chlorobenzophenone (2A-5CB) were grown in ethanol by slow solvent evaporation technique. The grown crystals were characterized by single-crystal XRD, FTIR, FT-Raman and UV–vis–NIR techniques. The UV–vis–NIR spectrum ascertains the cut-off wavelength of the sample as 390 nm. The powder second harmonic generation (SHG) technique reveals that 2A-5CB crystal has its SHG efficiency nearly three times that of KDP. The dielectric response of the sample was studied in the frequency region of 50 Hz–1 MHz at varying temperatures. The photoconductivity studies indicate that the 2A-5CB crystal exhibits negative photoconductivity. TGA–DTA studies confirm the melting point of the sample as 101.5 °C.

The effect of composition on UV–vis–NIR spectra of iron doped glasses in the systems Na 2O/MgO/SiO 2 and Na 2O/MgO/Al 2O 3/SiO 2

Glasses with the compositions xNa 2O · 10MgO · (90 − x)SiO 2, 10Na 2O · xMgO · (90 − x)SiO 2, 5Na 2O · 15MgO · xAl 2O 3 · (80 − x)SiO 2, xNa 2O · 10MgO · 10Al 2O 3 · (80 − x)SiO 2, 10Na 2O · 10MgO · xAl 2O 3 · (80 − x)SiO 2, 10Na 2O · 5MgO · 10Al 2O 3 · (80 − x)SiO 2 were melted and studied using UV–vis–NIR spectroscopy in the wavenumber range from 5000 to 30 000 cm −1. At [Al 2O 3] > [Na 2O], the UV-cut off is strongly shifted to smaller wavenumbers and the NIR peak at around 10 000 cm −1 attributed to Fe 2+ in sixfold coordination gets narrower. Furthermore, the intensity of the NIR peak at 5500 cm −1 increases. This is explained by the incorporation of iron in the respective glass structures.

Structural, thermal and optical properties of a semiorganic nonlinear optical single crystal: Glycine zinc sulphate

Glycine zinc sulphate salt was synthesized and the solubility and metastable zonewidth were estimated from the aqueous solution. Single crystals of glycine zinc sulphate were grown by solvent evaporation method from aqueous solution. Grown crystals were characterized by X-ray diffraction and FT-IR spectral analyses. The range and percentage of optical transmission was ascertained by recording UV–vis–NIR spectrum. Thermal properties of the crystal were investigated by thermogravimetric analysis. Microhardness study was carried out on (0 1 −1) face of the grown crystal. Its powder second harmonic generation efficiency was measured using Nd:YAG laser and the value was observed to be 0.7 times that of potassium dihydrogen orthophosphate.

The effect of the inner particle structure on the electronic structure of the nano-crystalline Li–Ti–O spinels

The effect of the inner particle structure on Li insertion activity and electronic structure of the nano-crystalline Li–Ti–O spinels was studied on materials prepared by solid state and solvothermal synthesis. The high temperature prepared materials of composition corresponding to Li 4Ti 5O 12 feature particles with characteristic size of ca. 200 nm with randomly distributed defects. The products of solvothermal synthesis with composition Li 1.1Ti 1.9O 4+ δ , feature cubic particles of characteristic dimension of ca. 50 nm; the characteristic particle size differs from that of the coherent domain determined by X-ray diffraction. The reduction of the solvothermal and high temperature synthesized nano-crystalline spinels in Li containing solutions leads according to 6Li MAS NMR spectra to Li insertion into tetrahedral 8b and octahedral 16c position, respectively. Additional broad NMR signal attributable to a Knight shift was observed in spectra of partially reduced high temperature spinels. In the case of solvothermal spinels is the Knight shift signal less pronounced and appears only in spectra of samples in which the phase transition occurs on the local level. The UV–vis–NIR spectra of the partially reduced Li–Ti–O spinel samples correspond to expected semiconductor character of Li–Ti–O spinels. Both types of materials are characterized by band gap of 3.8 eV (high temperature spinel) and 3.5 eV (solvothermal material). Partial reduction accompanied with Li insertion causes additional optical transition in the visible to near infrared region, which can be attributed to formation of trivalent Ti, character of which changes with degree of reduction. The behavior observed for partially reduced high temperature spinels is similar to that reported for TiO 2 (anatase). The spectral behavior of the partially reduced solvothermal spinels is more complex and reflects suppressed phase transition.

Spectral and optical studies of 2-amino-5-nitropyridinium dihydrogen phosphate: A semiorganic nonlinear optical material

2-Amino-5-nitropyridinium dihydrogen phosphate (2A5NPDP) was synthesized and the molecular structure was elucidated by FT-IR, FT-Raman and FT-NMR. The proton and carbon configurations of 2A5NPDP was confirmed through FT-NMR technique. UV–vis–NIR spectrum was recorded and the optical transmittance region was identified as 350 nm. Single crystals were grown from ethanol by slow evaporation technique at 35 °C and the unit cell constants were determined. Bulk and powder second harmonic generation (SHG) measurements were carried out using Nd:YAG laser ( λ = 1064 nm) and its phase matching condition was determined.

Crystal growth, thermal and optical studies of nonlinear optical material: Glycine potassium sulphate

A new nonlinear optical material glycine potassium sulphate (GPS) has been synthesized and optical quality crystals were grown from aqueous solution. This material has positive temperature coefficient revealed from the solubility studies. The grown crystals were characterized by employing several techniques such as single crystal and powder X-ray diffraction, thermo gravimetric analysis, FTIR and UV–vis–NIR spectra. The etching studies have been done on the (1 0 0) plane of the grown crystal. Preliminary measurements to find second harmonic generation efficiency of GPS has been carried out.

Crystal structure of single crystals of nonlinear optical l-histidinium trichloroacetate

Single crystals of a new histidinium salt: l-histidinium trichloroacetate {abbreviated as LHTCA; [(C 3N 2H 4) CH 2CH (NH 3) (CO 2)] + CCl 3COO −} were grown by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in a non-centrosymmetric space group P2 1 of monoclinic system with cell parameters a = 5.4505(18) Å, b = 25.769(8) Å, c = 9.210(2) Å and β = 99.98(2)° with Z = 4. The structure has been refined to an R-value of 0.05 for 2539 observed reflections using three-dimensional X-ray diffraction data. The vibrational structure of the compound confirms the presence of various functional groups in the molecule. The UV–Vis–NIR spectrum shows a good transparency in the whole of the region from ultraviolet to near IR. The Kurtz–Perry powder SHG measurement confirms the frequency doubling of the crystal and its powder SHG efficiency was measured as d eff = 0.33 d eff (KDP).

Structural, spectral, linear and nonlinear optical properties of new nonlinear optical l-histidinium trichloroacetate crystals

Single crystals of a new histidinium salt: l-histidinium trichloroacetate {abbreviated as LHTCA; [(C 3N 2H 4)CH 2CH(NH 3)(CO 2)] +CCl 3COO −} were grown by slow evaporation of an aqueous solution at room temperature. The compound crystallizes in a non-centrosymmetric space group P2 1 of monoclinic system with cell parameters a = 5.4505(18) Å, b = 25.769(8) Å, c = 9.210 (2) Å and β = 99.98(2)°. The vibrational structure of the compound confirms the presence of various functional groups in the molecule. The UV–vis–NIR spectrum shows a good transparency in the whole of the region from ultraviolet to near IR. The Kurtz powder SHG measurement confirms the frequency doubling of the crystal. Thermal behaviour of the crystals has been investigated by DSC analysis. These preliminary results suggest that LHTCA crystal can act as a potential and promising candidate for frequency doubling applications even from the near UV region to the near IR.

Comparison of the bis(ferrocenylethynyl)phenylmethylium cation with bis(ferrocenylethenyl)methylium analogues

Several new ferrocenylethynyl derivatives, (FcCC) 2CHOH, (FcCC) 2CH 2, (FcCC) 2CPhOH have been synthesised from ethynylferrocene. Attempts to synthesise the corresponding bis(ferrocenylethynyl)-stabilised carbocations by hydroxyl or hydride abstraction from the bridging group was unsuccessful for (FcCC) 2CHOH and (FcCC) 2CH 2, respectively. In the case of (FcCC) 2CPhOH, the [(FcCC) 2CPh] + cation could be observed by 1H and 13C NMR, and by UV–Vis–NIR spectroscopy, but was too unstable for isolation or prolonged study in solution. The UV–Vis–NIR spectrum of [(FcCC) 2CPh] + is compared to that of the considerably more stable cations, [Fc(CHCH) 2CH] + and [(FcCHCH) 2CPh] +.

Spectroelectrochemical characterisation of Langmuir–Schaefer films of heteroleptic phthalocyanine complexes. Potential applications

The Langmuir–Schaefer technique has been used to fabricate ordered monolayers of novel heteroleptic double and triple-decker phthalocyanine derivatives. The molecules studied include a double-decker mixed porphyrinate and naphthalocyaninate lanthanum(III) compound and a europium triple-decker molecule where one of the rings is a substituted porphyrin and the two remaining rings are substituted phthalocyanine macrocycles. The materials and their films have been characterised using UV–vis–NIR spectroscopy and electrochemistry. The UV–vis–NIR spectra of the solutions show the expected features corresponding to the aromatic rings present in each molecule. The absorption spectra of LS films show broadenings and important shifts to higher wavelengths when compared to the electronic absorption spectra of solutions or disordered cast films. Thin films are sensitive to electron acceptor gases, such as NOx as observed by modifications in the electronic absorption spectra of the films. These fast and reversible changes can be the basis of optical sensors based on thin films of heteroleptic phthalocyanines (Pc). Cyclic and square wave voltammograms of dichloromethane solutions lead to rich curves where a variety of peaks are observed. The voltammogrames of the corresponding films also reflect the rich electrochemical properties of the studied compounds. Electrochromism has been found with LB and cast films electrodes in KCl and KClO 4 solutions: important changes in the UV–vis–NIR spectra registered in situ simultaneously to the application of the electrical potential have been observed. The rich electrochemistry and the electrochromism observed, opens the possibility of using such films in multicolour electrochromic devices. Films prepared onto ITO glass show characteristic electrochemical responses when exposed to solutions of organic compounds, such as ascorbic and vanillic acid, providing a high degree of cross-selectivity. This effect can be used in the development of arrays of sensors used in electronic tongues. In summary Langmuir–Schaefer films of heteroleptic double and triple-decker phthalocyanines could be of interest at least in three potential applications: thin film electrochromic devices, optical gas sensors and voltammetric sensors.

The role of counterions (Mo, Nb, Sb, W) in Cr-, Mn-, Ni- and V-doped rutile ceramic pigments: Part 2. Colour and technological properties

Industrial rutile pigments are manufactured using several chromophores: Cr (giving an orange hue), Mn (tan), Ni (yellow) and V (gray); a second element, the so-called counterion (i.e. Mo, Sb, Nb or W) is always added in order to achieve the desired coloration and/or improve the technological properties (e.g. chemico-physical resistance in ceramic bodies and glazes). The colour of these pigments is determined by both metal–ligand charge transfer (Ti 4+ ↔ O 2−) and crystal field effects (transition metals substituting Ti 4+ in octahedral coordination). Though the absorbance bands are broad and frequently overlapped, the UV–vis–NIR spectra suggest the occurrence of Cr 3+, Mn 2+, Mn 3+, Ni 2+, V 3+, and V 4+ as chromophores. Rutile pigments are suitable for through-body (up to 1250 °C) and glaze applications (up to 1100 °C). The best coloration of porcelain stoneware bodies is achieved with Sb or W as counterions, though the higher stability is ensured by Sb, but in the Ti–Ni–W system. The best glaze colours are accomplished by W-bearing pigments, which however are less stable than Nb- or Sb-containing ones, except than for the V + W coupling. This latter represents a new and very interesting Co-free and Cr-free black pigment for low temperature applications.

Hydrothermal synthesis, characterization and magnetic properties of (N 4C 6H 21)·(Co(H 2PO 4)(HPO 4) 2)

The title compound, (N 4C 6H 21)·(Co(H 2PO 4)(HPO 4) 2), was prepared hydrothermally (473 K, 10 days, autogenous pressure), in the presence of the tris(2-aminoethyl)amine as organic template. Its structure is built up from a network of four membered-rings, formed by the vertex linkages between [CoO 4] and [H 2PO 4] tetrahedra with [HPO 4] moieties hanging from the Co center. Hydrogen bonds involving the cobalt phosphate units and the triply protonated amine molecule, contribute to the stability of the structure. The IR spectrum shows bands characteristic of the (N 4C 6H 21) 3+ cations and the (H 2PO 4) − and (HPO 4) 2− phosphate anions. The UV–Visible–NIR spectrum confirms the tetrahedral coordination of Co 2+ ions. The TGA analysis indicates that the dehydration of (N 4C 6H 21)·(Co(H 2PO 4)(HPO 4) 2) occurs in one step. Magnetic measurements from 4.5 to 305 K show a weak antiferromagnetic character of this compound.

Use of conducting polypyrrole blends as gas sensors

We discuss the use of polymeric blends formed by the controlled growth of doped polypyrrole chains in the interior of films of different dielectric polymers as sensors of the presence of representative examples of volatile organic compounds. The dielectric films (of either (poly(caprolactone), poly(ethylene oxide), poly(methyl-methacrylate), poly(vinyl alcohol), or poly(vinyl-acetate)) containing an appropriate oxidizing agent were prepared atop a conducting glass substrate and the polymerization of polypyrrole was induced through the vapor phase technique, after exposure of the desired matrix to pyrrole vapor. The UV–vis–NIR spectra of the films were used to monitor the increase of their conductive character through the assessment of the intensity of the polaron band characteristic of the doped form of polypyrrole. The change of conductivity upon exposure to the volatile compounds used (methanol, ethanol, carbon tetrachloride and benzene) was adopted as a measure of the corresponding sensitiveness of the films. Differently to the previous case in which doped films of polypyrrole were examined as sensors (when a similar low level of response was found towards apolar compounds), now we have found that some of the blends (PMMA/PPY and PVA/PPY, in special) exhibit a particular sensitiveness to the polarity of the molecule of the vapor tested. We therefore suggest that the simultaneous use of such polypyrrole blends in an arrangement pattern can improve the efficiency of electronic nose devices.

Analysis of Fe species in zeolites by UV–VIS–NIR, IR spectra and voltammetry. Effect of preparation, Fe loading and zeolite type

Three procedures were employed for the preparation of Fe-zeolites with ZSM-5 (MFI), ferrierite (FER) and beta (BEA) structures: ion exchange from FeCl 3 solution in acetyl acetonate and solid-state ion exchange from FeCl 2 using an oxygen or nitrogen stream. A combination of UV–VIS–NIR spectra, IR spectra of skeletal vibrations and of adsorbed NO, as well as voltammetry provided information on the type of Fe species introduced. Single Fe(III) ion complexes (Fe(H 2O) 6− x OH x ) in hydrated zeolites were reflected in the charge-transfer bands at 33 100, 37 300 and 45 600 cm −1. The single Fe(II) ions at cationic sites in evacuated zeolites yielded (through perturbation of framework T–O bonds) characteristic bands (910–950 cm −1) in the region of the skeletal window. These Fe(II) ions with adsorbed NO were also reflected in vibrations at 1880 cm −1. Dinuclear Fe–oxo complexes yielded the Vis band at 28 200 cm −1. Voltammetry indicated the presence of Fe oxides (hematite) through the reduction peak at −0.7 V. Such oxide-like species were also reflected in the absorption edge at 19 800 cm −1, and a doublet at 11 000 and 11 800 cm −1 in the Vis spectra. Fe(II)–NO vibrations at 1840, 1810 and 1760 cm −1 belonged to the undefined exposed Fe cations, probably originating from supported oxides. Using an ion exchange procedure, employing FeCl 3 in acetyl acetonate, exclusively Fe ions at cationic sites could be introduced at low concentrations (Fe/Al < 0.1). At higher Fe loadings, dinuclear Fe–oxo complexes were formed preferably in Fe-ZSM-5, but were absent in Fe-beta. Exclusively single Fe species could not be prepared at Fe concentrations above Fe/Al > 0.2; all three types of Fe species, single Fe ions, dinuclear Fe–oxo complexes and Fe oxides were formed.

Langmuir Layers and Langmuir–Blodgett Films of Bis-tetrathiafulvalene Annelated Macrocycle

Abstract The Langmuir layers of amphiphilic bis(tetrathiafulvalene) [bis(TTF)] annelated macrocycle (1) and those of the (1)[2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane (F4-TCNQ)]2 charge-transfer (CT) complex were evaluated. The neutral molecule of 1 recognized Cs+ ion at the air–water interface forming a domain structure. Contrastingly, (1)(F4-TCNQ)2 did not recognize Cs+ ion at the air–water interface. The Langmuir layers of 1 were deposited on a mica surface, resulting in the formation of fibrils. The highly oriented structure of the fibrils at the molecular level was confirmed by a large dicroism in the IR spectra. The (1)(F4-TCNQ)2 layer deposited on the mica surface consisted of nanowires oriented in specific directions. The UV–vis–NIR spectra revealed an intramolecular dimer structure of the donor 1 cation radical in the CT complex. An extended nanowire network structure was obtained when the K+ cation was introduced into the subphase. The stacking of intramolecular TTF dimers and intermolecular F4-TCNQ dimers directed the formation of nanowires, which are oriented on mica by recognizing fully occupied hexagonal K+ sites at the surface. The nanowire orientation was readily disturbed by varying film deposition conditions such as subphase temperature, deposition speed, or surface pressure, indicating that the fluidity of Langmuir layer was important for obtaining nanowire structure.

Fibrillar polyaniline/diatomite composite synthesized by one-step in situ polymerization method

A fibrillar polyaniline/diatomite composite was prepared by one-step in situ polymerization of aniline in the dispersed system of diatomite, and was characterized via Fourier-transform infrared spectra (FT-IR), UV–vis–NIR spectra, wide-angle X-ray diffraction (WXRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM), as well as conductivity. Morphology of the composite is uniform nanofibers, which the diameters of nanofibers are about 50–80 nm. The conductivity of polyaniline/diatomite composite contained 28% polyaniline is 0.29 S cm −1 at 25 °C, and temperature of thermal degradation has reached 493 °C in air. The composite has potential commercial applications as fillers for electromagnetic shielding materials and conductive coatings.

Synthesis, crystal structure and photoconductivity of new molecular complex of C 60 with tetrabenzo(1,2-bis[4H-thiopyran-4-ylidene]ethene): Bz 4BTPE C 60

A new molecular complex of C 60 with tetrabenzo(1,2-bis[4H-thiopyran-4-ylidene]ethene), Bz 4BTPE C 60 ( 1) has been obtained. The complex has a layered structure in which closely packed hexagonal layers of C 60 alternate with the layers composed of Bz 4BTPE molecules. The complex has a neutral ground state according to UV–vis–NIR spectrum. It has been found that single crystals of 1 show low ‘dark’ conductivity of σ∼10 −10 (Ω cm) −1. A 10 2 increase in photocurrent has been observed upon illuminating the crystal with white light. Photoconductivity of 1 is sensitive to magnetic field with B 0<1 T and increases up to 5% in magnetic field. The photoconductivity spectra of the complex indicate that free charge carriers are generated in the UV–visible range mainly by the Bz 4BTPE excitation (the peaks at 622, 562, 472 and 348 nm) with a possible contribution of charge transfer excitations between neighboring C 60 molecules (the peak at 472 nm).

Microhardness, FTIR and transmission spectral studies of Mg 2+ and Zn 2+ doped nonlinear optical BTCC single crystals

Pure, Mg 2+ and Zn 2+ doped BTCC single crystals are grown from their aqueous solutions at 301 K. The grown crystals are characterized by single crystal XRD, FTIR and UV–Vis-NIR spectral studies. The preliminary investigations of the UV–Vis-NIR spectra on the doped samples suggest an increased percentage of transmission in comparison to pure BTCC crystals. The SHG efficiency of the metal doped BTCC crystals is found better than the pure ones. It is estimated from the microhardness studies that the mechanical strength of the BTCC crystals are improved due to the metallic (Mg 2+ and Zn 2+) substitutions.

Synthesis, growth and characterization of new mixed analogs of LAP family crystals

New mixed compounds of l-arginine phosphate monohydrate (LAP) have been synthesized with the partial substitution of HF, HBr, CH3COOH and H3BO3, and single crystals were grown successfully. The addition of HF in LAP inhibits the microbial growth up to 40 days. Boric acid-mixed LAP is reported for the first time. The grown crystals were characterized by powder XRD, FTIR, UV–vis–NIR spectra. The preliminary work of powder SHG using Kurtz and Perry technique confirms the second harmonic generation effect in the grown crystals.