Quinone-Quinoneimine Tautomerism of 5, 8-Bis(donor) substituted 1, 4-Naphthoquinonoid Dyes

Quinone-quinoneimine tautomerism of 5, 8-bis(donor) substituted 1, 4-naphthoquinones have been investigated by means of their visible absorption spectra. Tautomerism was found to be influenced mainly by the nature of the substituents and the polarity of the solvents; the equilibrium shifted to the quinone form in the more polar solvents. The quinone tautomer absorbed visible light at much longer wavelengths (about 160–180 nm) than did the quinoneimine tautomer. Isosbestic points of the tautomerism were observed. The calculated absorption maximum of each tautomer, obtained by means of the PPP MO method, was correlated with the observed values to predict the principal tautomer in solution.     

Modification of polyethersulphone induced by high energy proton,C+, and Ne6+ ions: A spectroscopic study

Polyethersulphone (PES) was irradiated with 4 MeV proton, 3.6 MeV C⁺, and 145 MeV Ne⁶⁺ ions at different ion fluences. The linear energy transfer dependence on ion‐induced spectral changes was analyzed by ultraviolet–visible, Fourier transform infrared spectroscopy and fluorescence spectroscopy. The gradual red shift with the increase in optical absorption was observed in the region of 350–500 nm for proton and 400–800 nm for C⁺ and Ne⁶⁺ ions irradiated PES. The gradual shift in absorption may be attributed to the formation of carbonaceous clusters. The gradual decrease in optical band gap indicates increase in cluster sizes. When PES was irradiated with protons, loss in fluorescence emission intensity at 440 nm was observed, although there was no change in spectral shape. In contrast, C⁺ and Ne⁶⁺ ion irradiated PES showed blue shift with concomitant loss in intensity and the formation of new peak at 575 nm. In fact, heavier ions are found to be more effective in inducing physicochemical modifications in PES. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1591–1597, 2006     

Spectral characterisation and computational studies of some novel phenylazoindol‐2‐one dyes

A series of novel phenylazo disperse dyes were prepared by coupling selected diazotised 3‐ or 4‐anilines with indol‐2‐one. The structures of the synthesised dyes were determined by spectroscopic and analytical methods. Solvent effects on the ultraviolet–visible absorption spectra of these novel dyes were studied. The colour of the dyes was evaluated with respect to the substituent therein. Acid and base effects on the visible absorption maxima of the dyes were also reported. The tautomerism of 3‐(phenyldiazenyl)indol‐2‐one was modelled by density functional theory at the B3LYP level. The ultraviolet–visible absorption spectra for the tautomers were reproduced with the time‐dependent density functional theory and semi‐empirical Zerner’s intermediate neglect of differential overlap/spectroscopic (ZINDO/S) method. The predominance of the keto–hydrazone tautomer was confirmed experimentally and theoretically.     

Solvatochromism, tautomerism and dichroism of some azoquinoline dyes in liquids and liquid crystals

Absorption and emission spectra of three hetarylazoquinoline compounds with different substituents were examined in liquids and liquid crystalline solvents for the first time. The spectral features of the hetarylazoquinoline dyes were explained according to azo/hydrazone tautomerism in conjunction with the solvatochromic characteristic of the preferred tautomer. The nature and extent of solute-solvent interactions were described using Kamlet-Taft and Katritzky multiparameter polarity scales. It was observed that solvatochromic azo/hydrazone tautomerism depend on multiple solute-solvent interactions, in particular on specific interactions and the solvent ability to transport the hydrogen atom through the media. In addition, it was concluded that anisotropic hosts prevent shift of the tautomeric equilibrium toward the hydrazone form.     

Solvatochromism,halochromism, and azo–hydrazone tautomerism in novel V‐shaped azo‐azine colorants – consolidated experimental and computational approach

The azo–hydrazone tautomerism, solvatochromism, and halochromism in four novel V‐shaped asymmetrical acceptor‐π‐donor‐π‐acceptor (A‐π‐D‐π‐A) compounds were examined. They contain 2,7,15,16‐functionalised benzophenazine cores connected to the anchoring electron‐deficient phenyl core via azo linkers and 2,7‐position fused with anthraquinone. These compounds derived from 2‐hydroxy‐1,4‐napthaquinone (lawsone) have been prepared in moderate to good yields. The synthesis involved the diazotisation of substituted aromatic amines, coupling onto 2‐hydroxy‐1,4‐napthaquinone, and further condensing the resulting azo compounds with 1,2‐diaminoanthraquinone in acetic acid. The absorption wavelengths of the dyes in different solvents were in the range 500–720 nm. The spectral changes of the synthesised azo‐azine compounds in different pH indicated the formation of hydrazone tautomer in acidic pH and of azo tautomer in alkaline pH. Density functional theory was used to assess the tautomers in terms of geometry and position of the tautomeric equilibrium. Time‐dependent density functional theory calculations allowed us to assign the electronic transitions (>90%) of the low‐energy bands.     

Absorption spectra and tautomerism of aminonaphthazarins

2-n-Butylaminonaphthazarin (2) absorbs at 499 and 532 nm in ethanol but at 539 and 577 nm in alkali solution, while 2, 6-bis(n-butylamino)naphthazarin (3) absorbs at 461, 500 and 540 nm in ethanol but at 511 and 545 nm in alkali solution, with only a small bathochromic shift of 5 nm. The absorption curve of 3 was changed by addition of alkali and the λD_max at around 461 nm completely disappeared. In the case of 2-bromo-3, 6-bis(n-butylamino)naphthazarin (4), tautomerism between the 1, 4-quinone and 1, 5-quinone forms was observed and the isosbestic point was observed at 480 nm. Dye 2 easily deprotonated to give the 1, 4-dianion, but dyes 3 and 4 existed as tautomeric mixtures in solution and shifted to 1, 5-quinone forms in alkali solution.     

Determination of critical micelle concentrations of some nonionic surfactants by Keto-Enol tautomerism of benzoylacetoanilide

The absorbances of benzoylacetoanilide, keto-enol tautomer, dissolved in aqueous solution of several concentration ranges below and above the CMC of the incorporating surfactants. Below the CMC, the absorbance of the band at 250 nm due to the ketonic form showed hardly any change and that of the band at 320 nm due to the enolic form could not be observed. In contrast, above the CMC, the spectral band of the enolic form appeared, and the absorbance increased abruptly and that due to the ketonic form decreased gradually. The changes at the CMC in absorbance for these nonionic surfactants were distinctly observed by plotting the absorbance at 250 and 320 nm as a function of the concentration of surfactants. These changes at the CMC were very noticeable with nonionic surfactants as well as with ionic surfactants. The concentrations corresponding to break points for these surfactants were in fairly good agreement with the published data of the CMC of each surfactant. This method of keto-enol tautomerism using benzoylacetoanilide has been confirmed CMC for most anionic, cationic, and nonionic surfactants.     

Observations of Twelve USEPA Priority Polycyclic Aromatic Hydrocarbons in the Aitken Size Range (10–32 nm D p )

Particle size distribution measurements of twelve USEPA priority pollutant polycyclic aromatic hydrocarbons (PAHs)—collected in Riverside, California, down to 10 nm aerodynamic diameter (D_p)—observed on integrated nocturnal samples (7:00 p.m.-6:30 a.m.) revealed that between 46 and 100% of the mass of particles in the Aitken size range was found in the 10–18 nm size bin. Particles in this size range have high alveolar deposition efficiency.     

Synthesis and characterization of CdSe nanocrystals in the presence of butylamine as a capping agent

TOPO-capped cadmium selenide (CdSe) nanocrystals of sizes between 3 and 8 nm have been synthesized, and the surface-capping molecule, trioctylphosphine oxide, was replaced by butylamine. The effects of changing the surface ligands of the synthesized CdSe nanocrystals on the structural, optical, and electrical properties were investigated. The shift toward shorter wavelength (higher energy) in the visible range of the optical absorption band edge was observed by UV-Vis spectroscopy, and a blue-shift of the photoluminescence peaks was observed with luminescent quenching. Surface modification was found to cause an increase in the surface energy of nanocrystals, resulting in the improvement in charge carrier separation and cell performance in applications towards bulk hetero-junction solar cells.     

Azo dye location in textiles: a novel UV–vis approach

Ultraviolet–visible spectra of Orange II exhibit blue shifts in apolar solvents due to the formation of the azo tautomer. Upon absorption to cotton, Orange II remains as the hydrazone tautomer and, like other phenylazonaphthol dyes or Methyl Orange, exhibits small red spectral shifts. Two superimposed spectra – characteristic of the azo and hydrazone tautomeric forms – are detected when dye 1 ( X = p -MeO) absorbs onto cotton. Only the azo form is observed on nylon; all other dyes, except Orange II, give blue shifts. A model is developed in which the more apolar moiety of the dye binds to pockets formed in the non-crystalline (amorphous) regions of cotton, with those parts containing the sulphonate group protruding into aqueous pores. In nylon, the binding sites are more apolar with the sulphonate groups bound electrostatically.     

阳极氧化纳米膜上酶固定技术的验证与应用

对阳极氧化纳米膜烷硅化和活化的表面处理后,通过与赖氨酸进行取代反应达到固定酶的目的。以蔗糖和葡萄糖为反应物,在被固定的转化酵素-葡萄糖氧化酶-辣根过氧化物酶的催化作用下,利用实时检测510 nm波长下醌亚胺的光吸收,验证了上述酶固定法在生物反应器应用中的可行性。     

氨基酸的光化学诱导动态核极化

维生素B_2与氨基酸和氨基酸衍生物水溶液体系的光化学诱导动态核极化(photo chemically induced dynamic nuclear polarization, CIDNP)研究表明,在维生素B_2作为光敏化剂的体系中,N-乙酰-L-酪氨酸和N_α-乙酰-L-组氨酸显示很强的极化信号,     

Synthese und Charakterisierung von Stilbazoliumfarbstoffen mit mesoionischer 1,2-Diaziniumstruktur

Synthesis and Characterization of Stilbazolium Dyes with Mesoionic 1,2-Diazinium Structure Pyridazinium salts of typ 1 react with substituted aromatic and heteroaromatic aldehydes 2a , e–h , 8a–c and trans-p-dimethylamino-cinnamaldehyde 3a to the charge transfer dyes 4a–h , 5a–d , 9a–c . They absorb in the range between 380 and 660°nm. The dehydratisation of the aldoxime group in 4, 5 to the nitril group under formation of 6 , 7a–d causes a bathochromic shift of the absorption band up to 110 nm. The UV-VIS data are discussed dependent on the structure of the dyes.     

Proton magnetic resonance spectra of some naphthalene derivatives in DMSO-d6

The chemical shifts of the ring protons of 14 naphthalenesulfonic acid derivatives have been assigned from 250 MHz spectra. In addition, the spectra of a large number of monosubstituted naphthalenes were recorded using DMSO-d₆ as solvent. It is clear from this latter part of the study that DMSO-d₆ often causes an upfield (to a lower δ value) shift (relative to those in CDCl₃) in the δ values of the protons in this ring system. It is also clear that a number of signals are less resolved when DMSO-d₆ is used in lieu of CDCl₃, at the field strength of 250MHz.     

The synthesis and optical properties of quinoxalines bearing 2,2′:6′,2″-terpyridine

4′-(4-{2-[6,7-Bis-dodecyloxy-3-(2-substituted-phenyl-vinyl)-quinoxalin-2-yl]-vinyl}-phenyl)-[2,2′:6′,2″]terpyridine was prepared by the Horner–Wadsworth–Emmons reaction of 4-[2,2′:6′,2″]terpyridin-4′-yl-benzaldehyde with various quinoxaline derivatives. The absorption and fluorescence maxima of the compounds were observed at 398–443 nm and 484–586 nm, respectively; the compounds offer potential as optical sensors for protons and metal ions.     

Optical degradation of polydimethylsiloxane under 150 keV proton exposure

The optical degradation of polydimethylsiloxane (PDMS) was investigated under exposure of 150 keV protons to reveal the damage behavior of organic silicone in space. The exposure was performed in a ground‐based simulation for space protons. The experimental results show that the optical degradation mainly occurs in the visible region. With increasing proton fluence, the absorption band shifts toward longer wavelengths (red‐shift) and the solar absorptance α_s ascends. The analysis of Fourier transform infrared spectroscopy indicates that under the exposure, the degradation of the PDMS occurs to form hexamethylcyclotrisiloxane, the amount of which increases with increasing the proton fluence. This could cause an increase in delocalization degree of the σ electrons, resulting in the red‐shift of absorption bands. Also, the energy for valence electrons to be excited decreases and the n→π* jump is intensified, increasing the probability of optical absorption. As a result, the solar absorptance α_s of the PDMS increases under exposure of 150 keV protons. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Plasmon-induced photothermal effect of sub-10-nm Cu nanoparticles enables boosted full-spectrum solar H2 production

Distinguishing the contributions from localized surface plasmon resonance (LSPR)induced photothermal effect is a significant challenge in the study of solar hydrogen production. Herein, a well-defined one-dimensional Cu/TiO₂ heterostructure with Cu size of 3–6 nm is designed to address such issue. Cu nanoparticles present notable LSPR absorption from visible to near-infrared light, while no hydrogen is produced in the presence of simulated light with λ ≥ 700 nm. Interestingly, a remarkable improvement of hydrogen evolution under full-spectrum light was observed which is almost twice of that under only ultraviolet–visible light irradiation, implying the critical yet auxiliary role of LSPR-induced photothermal effect in promoting photocatalytic performance. Significantly, a notable reduction of the apparent activation energy and strengthened charge separation efficiency are observed due to the increased local temperature of catalyst surface caused by the plasmon-induced photothermal effect. The kinetic and thermodynamic changes should be responsible for the enhanced hydrogen production.     

Studies on conformational transition of the maleic acid copolymer with styrene in aqueous salt solution by derivative spectroscopy

The first and second derivative spectra for the optical absorption of maleic acid copolymer with styrene were measured in aqueous 0.09 m NaCl at 25°C within a wavelength range of 240–280 nm, where contributions of groups, other than the phenyl ones, to the second derivatives seem to be negligible. The normal absorption spectra in the range were composed of seven absorption bands and the peak position of each band was determined from the derivative spectra. The peak position of the coiled form copolymer was found to shift to the shorter wavelength range compared with the compact form of the copolymer. From the extent of such blue shifts for each peak, the environment near the phenyl groups in the compact copolymer form was concluded to be similar to aqueous ethanol (40–50 vol%), by comparing with the derivative spectra for $\text{N-}\text{acetyl-}\text{l}\text{-rmphenylalanine}$ in a water-ethanol mixture. However, the first and second derivative spectra and various first derivative spectra were found to have 12 isoderivative points, and all the bands of the different spectra displayed the two-state character of the transition. The degree of transition was determined from the change in the peak height of each band and this coincided well with the pH-titration data.     

Electrical and optical properties of polymer‐Au nanocomposite films synthesized by magnetron cosputtering

Polymer‐Au nanocomposite films were prepared by co‐sputtering from two independent magnetron sources. By sputtering from gold and polytetrafluoroethylene (PTFE) magnetrons, we prepared homogenous composite films using a rotatable sample holder. The microstructure of the nanocomposites was studied by transmission electron microscopy (TEM). The resistivity drops from 10⁷ to 10^?3 Ohm cm over a narrow range of metal content. The thin composite films show a strong optical absorption in the visible region due to surface plasmon resonances. The optical absorption has a strong dependence on the metal content, showing a red shift of the absorption peak from 550 nm to more than 700 nm with increasing gold content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The Effect of Annelation on the Colour of 1, 4-Disubstituted Benzoanthraquinone Disperse Dyes

The visible spectra of a series of 1,4-disubstituted benzoanthraquinone dyes in benzene solution has been measured. The position of the absorption maxima of the dyes has been found to be well correlated with a mean ionization potential of the substituent groups. An annelation of anthraquinone dyes in the position of 2, 3 or 6, 7produced a small hypsochromic shift, while 5,6-annelation produced a large bathochromic shift. The additive properties on the absorption maximum of dibenzoanthraquinone dyes were also observed.