Delocalized cationic azo dyes containing a thiazole moiety

Several new delocalized cationic azo dyes incorporating a bathochromic thiazole moiety have been prepared in moderate to good yields. The synthesis involved the Knoevenagel condensation of an intermediate azo compound, bearing a terminal formyl group, with methylenic bases generated in situ from benzoazolium and quinolinium salts. All dyes display strong absorption around 700 nm and have shown negative solvatochromic behaviour.     

7-(2-Methoxycarbonylvinyl)-3-hydroxychromones: new dyes with red shifted dual emission

7-(2-Methoxycarbonylvinyl)-3-hydroxychromones have been synthesized using Heck coupling reaction from the corresponding 7-bromo-3-hydroxychromones. Introduction of the electron acceptor (2-methoxycarbonylvinyl) group at 7-position of 3-hydroxychromone results in a 30-40 nm red shift in absorption and >50 nm red shifts of both bands in emission. This derivatization allowed us to develop dyes with absorption maxima reaching 480 nm and dual emission in the red region of the spectrum. In comparison to the parent dyes, 7-acryl-3-hydroxychromones demonstrate significantly stronger solvatochromism. This is due to the acceptor group at 7-position, which increases the transfer character of the excited state of the dyes. The new dyes are highly prospective for the development of new fluorescent probes in biological research.     

Synthesis and fluorescence properties of naphthalimide-containing Tröger’s bases

Tröger’s bases based on the naphthalimide fluorophore have been prepared from N-alkyl-4-amino-1,8-naphthalimides. The fluorescence emission intensity of these dyes is highly medium dependent. In cyclohexane, these dyes emit near 440 nm with high quantum yields; addition of cosolvents reduces the fluorescence intensity near 440 nm and leads to increased fluorescence intensity around 480 nm.     

Photophysical properties and photostability of novel unsymmetric polycyclicphenazine-type D-π-A fluorescent dyes and the dye-doped films

Structural isomers of unsymmetric polycyclicphenazine-type D-π-A fluorescent dyes have been newly synthesized and characterized in both solution and polymer films. The dyes exhibited two strong absorption bands at around 328-401 nm and 516-532 nm, and an intense fluorescence band at around 595-629 nm (Φ = 0.32-0.84) in 1,4-dioxane. The dye-doped polymer films showed good ability of wavelength conversion; the films can efficiently convert ultraviolet and green-yellow lights into red light (Φ = 0.43-0.86). Moreover, the photostability of the dyes-doped PS, PMMA, and PLA films has been investigated.     

Fluorescent boron dipyrromethene (Bodipy) dyes having two and four vinyl residues

Several new extended fluorescent dyes have been prepared by stepwise functionalisation of the methyl groups located in the 1, 3, 5, and 7 substitution positions of Bodipy dyes. In one case, a ferrocene residue has been connected, giving rise to severe fluorescence quenching and a rich redox behavior. The stepwise syntheses were largely based on Knoevenagel reactions allowing the attachment of three different modules in a tetravinyl configuration. Most of these dyes exhibit reversible formation of radical cations and radical anions, as well as an irreversible formation of dications and dianions. Spectroscopic examination of the dyes under various conditions including the presence of acid leads to the conclusion that the delocalization is more effective in the 3,5-substitution positions than in the 1,7-positions. These novel dyes have absorption and emission wavelengths spanning the ranges of 573-718 nm and 585-778 nm, respectively.     

Synthesis and fluorescence properties of side-chain carboxylated 5,9-diaminobenzo[a]phenoxazinium salts

The efficient synthesis of a series of novel side-chain carboxylated 5,9-diaminobenzo[a]phenoxazinium salts is described. The ring system was prepared by the reaction of 5-alkylamino-2-nitrosophenol hydrochlorides with the appropriate N-alkylated-naphthylamine. Evaluation of the visible and fluorescence properties of the cationic dyes was carried out in ethanol and water at physiological pH. In both solvents they showed intense visible absorption maxima in the range 500-638 nm (ethanol) and 625-650 (water), and fluoresced strongly, with fluorescence maxima from 612 to 669 nm (ethanol) and from 654 to 685 nm (water). A wide variation in fluorescence quantum yields is observed, ranging from 0.051 to 0.50 and 0.065 to 0.32 in ethanol and water, respectively.     

New reactive fluorophores in the 1,2,3-triazine series

A one-pot synthesis of new fluorescent 2,5-dihydro-1,2,3-triazines with reactive functional groups and a large Stokes shift of 200 nm is described.     

Treatment of colored effluent of the textile industry in Bangladesh using zinc chloride treated indigenous activated carbons

The adsorption of colored compounds from the textile dyeing effluents of Bangladesh on granulated activated carbons produced from indigenous vegetable sources by chemical activation with zinc chloride was studied. The most important parameters in chemical activation were found be the chemical ratio of ZnCl₂ to feed (3:1), carbonization temperature (450-465 °C) and activation time (80 min). The adsorbances at 511 nm (red effluent) and 615 nm (blue effluent) were used for color estimation. It is established that at optimum temperature (50 °C), time of contact (30-40 min) and adsorbent loading (2 g l⁻¹), activated carbons developed from Segun saw-dust and water hyacinth showed substantial capability to remove coloring materials from the effluents. It is observed that adsorption of reactive dyes by all sorts of activated carbons is higher than disperse dyes. It is explained that activated carbon, because of its acidic nature, can better adsorb reactive dye particles containing large number of nitrogen sites and -SO₃Na group in their structure. The use of carbons would be economical, as saw-dust and water hyacinth are waste products and abundant in Bangladesh.     

Star-shaped panchromatic absorbing dyes based on a triazatruxene platform with diketopyrrolopyrrole and boron dipyrromethene substituents

The engineering of photoactive arrays built from a flat, functionalized triazatruxene (TAT) platform is described. The primary synthetic strategy involved the step by step connection of one, two or three bis(thienyl)diketopyrrolopyrrole (DPP) modules. Subsequent bromination of the pendent thiophene ring was not selective and provided a mixture of regioisomers. However, selective grafting of boron dipyrromethene (Bodipy) units via Pd-catalysed cross couplings enabled the construction of TAT/DPP/Bodipy arrays. As well, direct coupling of two green F-Bodipy units to dibromoTAT provided a substrate suitable for reaction with hydroxyl-propargyl-substituted red Bodipy dyes to give ready access to O-Bodipy linked multichromophoric systems. All the new dyes displayed strong absorption in the near-UV and visible region of the solar spectra (400–750 nm), with intramolecular cascade energy transfer enabling photon concentration and fluorescence at approximately 740 nm.     

Condensed heterocycles with a thiazole nucleus. 8. Thiazolo[4,3-a]pyrimido[5,4-e]pyrimidines

Condensation of 4-amino-2-methylthiothiazolium salts with 2,4,6-trichloro-5-formylpyrimidine or 3-R-2,4-dioxo-6-chloro-5-formyl-1,2,3,4-tetrahydropyrimidines yielded mesoionic derivatives of a new heterocyclic system — thiazolo[3,4-a]pyrimido[5,4-e]-pyrimidine — which can be used for the synthesis of polymethine dyes. The absorption maxima of these dyes are bathochromically shifted by 10–20 nm relative to the maxima of the thiazolopyrimidine analogs. The structure of the compounds synthesized was demonstrated by the PMR and IR spectra.For communication 7, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1126–1128, August, 1984.     

A cloud point extraction approach using Triton X-100 for the separation and preconcentration of Sudan dyes in chilli powder

A CPE-HPLC (UV) method was developed for the determination of Sudan (I-IV) dyes, non-ionic surfactant Triton X-100 was used to extract and preconcentrate Sudan dyes from chilli powder prior to their determination by HPLC-UV. The separation and determination of Sudan dyes was then carried out in the HPLC-UV system with isocratic elution, and the detector was set at 500 nm. The parameters and variables that affect the extraction were investigated. Under optimum conditions: 3% of Triton X-100 (W/V), 10% of Na₂CO₃ (W/V), heat-assisted at 70 °C for 30 min. Recoveries of the Sudan dyes ranged from 80.70% to 85.45% in chilli powder by CPE method, with all the relative standard deviations of less than 3%. Limit of detection (LOD) and limit of quantification (LOQ) were in the range of 2.0-4.0 and 7.0-12.0 μg kg⁻¹ in chilli powder, respectively.     

Absorption and emission spectroscopic characterization of some azo dyes and a diamino-maleonitrile dye

A linear and nonlinear optical spectroscopic characterization is carried out on three azo dyes (Reactive orange 1, Reactive violet 8, and Acidproof purplish red), and on N-(p-hydroxybenzylidene)-diamino-maleonitrile. Fluorescence quantum distributions, fluorescence quantum yields, and fluorescence lifetimes are measured. The saturable absorption is studied by nonlinear transmission measurements with intense picosecond laser pulses. The ground-state absorption recovery is studied by picosecond time-resolved pump and probe measurements. Absolute ground-state absorption cross-sections, excited-state absorption cross-sections, and dye concentrations are extracted from saturable absorption studies. The azo dyes have fluorescence lifetimes and ground-state absorption recovery times of around 2 ps and their excited-state absorption cross-sections are small (measured at 527 nm) making them good mode-locking dyes for picosecond and femtosecond lasers. The investigated diamino-maleonitrile dye exhibits sub-picosecond fluorescence lifetime and slow ground-state absorption recovery (>1 ns).     

Influence of adsorption orientation of methyl orange on silver colloids by Raman and fluorescence spectroscopy: pH effect

This work seeks to characterize the UV–Vis absorption, SRES and fluorescence of methyl orange (MO) on silver colloids at different pH. The gradual changes of SERS signals indicate differing adsorption orientations of dyes on silver surface when pH changed and thus, results in different energy transfer efficiencies, i.e., the fluorescence quenching at 428 nm and synchronous enhancement at 560 nm changed gradually with pH increased by step-up. Both experimental evidence and theoretic analysis indicate that, different molecular structures and differing adsorption orientations of dyes on silver surface were existence when pH changed, and thereat caused the diverse spectral phenomena.     

Development and validation of ultra-high performance supercritical fluid chromatography method for determination of illegal dyes and comparison to ultra-high performance liquid chromatography method

A novel simple, fast and efficient ultra-high performance supercritical fluid chromatography (UHPSFC) method was developed and validated for the separation and quantitative determination of eleven illegal dyes in chili-containing spices. The method involved a simple ultrasound-assisted liquid extraction of illegal compounds with tetrahydrofuran. The separation was performed using a supercritical fluid chromatography system and CSH Fluoro-Phenyl stationary phase at 70 °C. The mobile phase was carbon dioxide and the mixture of methanol:acetonitrile (1:1, v/v) with 2.5% formic acid as an additive at the flow rate 2.0 mL min⁻¹. The UV–vis detection was accomplished at 500 nm for seven compounds and at 420 nm for Sudan Orange G, Butter Yellow, Fast Garnet GBC and Methyl Red due to their maximum of absorbance. All eleven compounds were separated in less than 5 min. The method was successfully validated and applied using three commercial samples of chili-containing spices – Chili sauce (Indonesia), Feferony sauce (Slovakia) and Mojo sauce (Spain). The linearity range of proposed method was 0.50–9.09 mg kg⁻¹ (r ≥ 0.995). The detection limits were determined as signal to noise ratio of 3 and were ranged from 0.15 mg kg⁻¹ to 0.60 mg kg⁻¹ (1.80 mg kg⁻¹ for Fast Garnet) for standard solution and from 0.25 mg kg⁻¹ to 1.00 mg kg⁻¹ (2.50 mg kg⁻¹ for Fast Garnet, 1.50 mg kg⁻¹ for Sudan Red 7B) for chili-containing samples. The recovery values were in the range of 73.5–107.2% and relative standard deviation ranging from 0.1% to 8.2% for within-day precision and from 0.5% to 8.8% for between-day precision. The method showed potential for being used to monitor forbidden dyes in food constituents. The developed UHPSFC method was compared to the UHPLC-UV method. The orthogonality of Sudan dyes separation by these two methods was demonstrated. Benefits and drawbacks were discussed showing the reliability of both methods for monitoring of studied illegal dyes in real food constituents.     

Thiophene-fused coplanar sensitizer for dye-sensitized solar cells

We have designed and synthesized a novel ladder-type heteroacene dye consisting uniquely of thiophene segments as a photosensitizer for the dye-sensitized solar cells (DSSCs). The onset of the IPCE spectrum for the dye not only reaches up to 700 nm with a high IPCE (>60%) but also a solar energy-to-electricity conversion efficiency of 2.31% is achieved. Even though the efficiency is slightly lower than those of other dyes reported previously, this work opens up a new strategy to design heteroaromatic fused photosensitizers for DSSCs.     

Supercritical Propanol-Water Synthesis and Comprehensive Size Characterisation of Highly Crystalline anatase TiO2 Nanoparticles

Highly crystalline anatase TiO₂ nanoparticles have been synthesised in less than 1 min in a supercritical propanol-water mixture using a continuous flow reactor. The synthesis parameter space (T, P, concentration) has been explored and the average particle size can be accurately controlled within 10-18 nm with narrow size distributions (2-3 nm). At subcritical conditions amorphous products are obtained, whereas a broad range of T and P in the supercritical regime gives 11-14 nm particles. At high temperature and pressure, the particles size increase to 18 nm. The nanoparticles have been extensively characterised with powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) with excellent agreement on size and size distribution parameters. The SAXS analysis suggests disk-shaped particles with diameters that are approximately double the height. For comparison, a series of conventional autoclave sol-gel syntheses have been carried out. These also produce phase-pure anatase nanoparticles, but with much broader size distributions and at much longer synthesis times (hours). The study demonstrates that synthesis in supercritical fluids is a very promising method for manipulating the size and size distribution of nanoparticles, thus removing one of the key limitations in many applications of nanomaterials.     

Novel photoluminescent lanthanidomesogens forming bilayer smectic phase derived from blue light emitting liquid crystalline, one ring O-donor Schiff-base ligands

A series of new mononuclear lanthanide(III)-salicylaldimine complexes of the type [Ln(LH)₃(NO₃)₃] (Ln = La, Pr, Sm and Gd; LH = N-(2-hydroxyethyl)-4n-alkoxysalicylaldimine, n = 14, 18) have been synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR, UV-Vis, FAB-mass and magnetic susceptibility measurements. The ligand (LH) coordinate to lanthanide ions in zwitterionic form via the phenolic-oxygen with the proton shifted to the imine-nitrogen. The nitrato groups occurring in chelated bidentate fashion complete a nine-coordinate geometry. Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) show that the ligands are monotropic and their complexes exhibit enantiotropic highly viscous smectic A (SmA) mesophase in the temperature range 60-185 °C. A bilayer self organized assembly of the molecules in the mesophase are proposed on the basis of the small angle XRD study. The ligands are blue light emitters with a broad emission maxima at ∼447 nm while the lanthanide complexes show intense emission in the visible range (∼465-679 nm) at 350 nm excitation. The samarium(III) complex, [Sm(LH)₃(NO₃)₃] is distinct from the rest in emitting bright orange light (∼660 nm, Φ = 48%). The S_o-S₁ excitation band being stronger than the direct f-f excitation in the samarium complex clearly suggests that the Schiff-base ligands efficiently sensitize the luminescence of Sm³⁺. DFT calculations have been performed using DMol3 program at BLYP/DNP level to obtain the stable electronic structure of the ligand and complex.     

Synthesis of short and long-wavelength functionalised probes: amino acids' labelling and photophysical studies

Fluorescent labelling of α-amino acids at their N or C terminals in the main and lateral chains at short and long wavelengths was carried out in different ways. The N-[3-(naphthalen-1-ylamino)propanoyl]amino acid methyl esters synthesised showed strong fluorescence in the visible region (∼415 nm) of the electromagnetic spectrum. Condensation of these compounds with 5-diethylamino-2-nitrosophenol or 5-ethylamino-4-methyl-2-nitrosophenol produced the benzo[a]phenoxazine derivatives, with maximum emission wavelengths shifted to values higher than 644 nm. The synthesis of novel functionalised 5,9-diaminobenzo[a]phenoxazinium salts, by reaction of 5-ethylamino-4-methyl-2-nitrosophenol and N-substituted 1-naphthylamine and their use in the covalent labelling of the N or C terminals of valine, produced derivatives with long-wavelength emissions (644-653 nm). Photophysical studies using the synthesised compounds both in different solvents and in controlled pH were undertaken. Preliminary evaluation of photostability of the cationic polycyclic heterocycles in ethanol and water at physiological pH was also performed.     

Design of very transparent fluoropolymer resists for semiconductor manufacture at 157 nm

Photolithography at 157 nm requires development of new photoresists that are highly transparent at this wavelength. Transparent fluoropolymer platforms have been identified which also possess other materials properties required for chemically amplified imaging and aqueous development. Polymers of tetrafluoroethylene (TFE), a fluoroalcohol-substituted norbornene and an acid-labile acrylate ester show the best combination of properties. A solution, semibatch, free-radical polymerization process was developed allowing synthesis of the terpolymers on a multikilogram scale. Further property enhancements may arise from replacing the norbornene with functionalized tricyclononenes. Formulated resists have been imaged in a 157 nm microstepper.     

Synthesis and characterization of vanadium oxides nanorods

Vanadium oxides nanorods with high crystallinity and high surface area were synthesized by hydrothermal method using laurylamine hydrochloride, metal alkoxide and acetylacetone. The samples characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and SAED. Uniformly sized B phase VO₂ nanorods had widths about 40-80 nm and lengths reaching up to 1 μm. V₂O₅ rodlike structured with the widths about 100-500 nm and the lengths of 1-10 μm were obtained by calcination at 400 °C for 4 h. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides under mild conditions.