Structure Of Dyes Research Articles

Clean synthesis of disperse azo dyes based on peculiar stable 2,6-dibromo-4-nitrophenyl diazonium sulfate

The development of clean synthetic technology of disperse azo dyes is essential for the dye industry due to ecological and economical demands. In this study, a clean, safe, and low-energy-consumption method for preparing disperse azo dyes based on 2,6-dibromo-4-nitroaniline is presented with excellent yield and short reaction time. The peculiar stable diazonium sulfate of 2,6-dibromo-4-nitroaniline is precipitated from the organic reaction system, and the solid diazonium salt is directly used to synthesize disperse azo dyes. Compared with traditional method, the amount of sulfuric acid used is reduced by 80%, the amount of waste inorganic salt is reduced by 80.9% and the heat released from the reaction system is reduced by 88.5% in the proposed method. The dye structures are verified by 1H NMR, 13C NMR, Fourier transform infrared spectroscopy (FT-IR), and high resolution mass spectrometry (HR-MS). Compared with commercial dyes, the prepared dyes have the same dyeing properties that are sufficient for industrial applications.

Synthesis of symetrical near-infrared dyes containing benzo[c,d]indole system

Five symmetrical near infrared dyes having different linker between the two heterocycles were synthesized by condensation of N-alkylbenzo[c,d]indolium salts with either squaric acid or imine. All synthesized dyes showed strong absorbance in the near-infrared region of 850-1015 nm and can be used as nucleic acid detection or fluorescent labeling agents for proteins. Three of the dyes 21, 22 and 25 containing functionalized N-substituents (ester group) can be further modified or covalently attached to target. The structures of these cyanine dyes where characterized by virtue of NMR, UV, MALDI and Elemental analysis.Keywords: Synthesis, cyanine, Polymethine dyes, Near-IR dyes, Absorption, Chromophore.

Dye-sensitized graphitic carbon nitride (g-C3N4) for photocatalysis: a brief review

Photocatalytic semiconductors by solar light have received significant attention for their application on photocatalytic H2 evolution, degradation of pollutants, CO2 reduction, and so on. Among them, graphitic carbon nitride (g-C3N4) has the properties of earth rich, metal-free, high physicochemical stability, and suitable electronic band structure and band gap for many kinds of photocatalyst reactions. However, the energy conversion efficiency still limited due to the low utilization efficiency in the longer wavelength. Dye sensitization is currently one of promising methods to extend the absorption response region of semiconductors, and enhances the separation and transportation of photogenerated electrons and holes between dyes and semiconductors. It may be a good candidate strategy to enhance photocatalysis efficiency, even though lack of stability and repeatability for these composites. In this article, we have summarized dye-sensitized g-C3N4 with different mechanisms for variety of photocatalysis process, the relationship between structure of dyes and photocatalytic activity. Especially, dyes in H2 evolution process are divided into metal-free organic dyes, phthalocyanines, and porphyrins in detail. Comparing to metal-free organic dyes, the absorption of phthalocyanines and porphyrins can easily move to near-infrared region, which lead to the enhancement of H2 evolution activity. It may provide a guidance of the structure designing and constructing for highly effective dye-sensitized g-C3N4 photocatalysts for various applications. At last, we shared our opinions on the challenges and perspectives of dyes on g-C3N4 for photocatalyst.

Inverse Opal CuCrO2 Photocathodes for H2 Production Using Organic Dyes and a Molecular Ni Catalyst.

Dye-sensitized photoelectrochemical (DSPEC) cells are an emerging approach to producing solar fuels. The recent development of delafossite CuCrO2 as a p-type semiconductor has enabled H2 generation through the coassembly of catalyst and dye components. Here, we present a CuCrO2 electrode based on a high-surface-area inverse opal (IO) architecture with benchmark performance in DSPEC H2 generation. Coimmobilization of a phosphonated diketopyrrolopyrrole (DPP-P) or perylene monoimide (PMI-P) dye with a phosphonated molecular Ni catalyst (NiP) demonstrates the ability of IO-CuCrO2 to photogenerate H2. A positive photocurrent onset potential of approximately +0.8 V vs RHE was achieved with these photocathodes. The DPP-P-based photoelectrodes delivered photocurrents of −18 μA cm–2 and generated 160 ± 24 nmol of H2 cm–2, whereas the PMI-P-based photocathodes displayed higher photocurrents of −25 μA cm–2 and produced 215 ± 10 nmol of H2 cm–2 at 0.0 V vs RHE over the course of 2 h under visible light illumination (100 mW cm–2, AM 1.5G, λ > 420 nm, 25 °C). The high performance of the PMI-constructed system is attributed to the well-suited molecular structure and photophysical properties for p-type sensitization. These precious-metal-free photocathodes highlight the benefits of using bespoke IO-CuCrO2 electrodes as well as the important role of the molecular dye structure in DSPEC fuel synthesis.

Excited state intramolecular proton transfer in hydroxyanthraquinones: Toward predicting fading of organic red colorants in art.

Compositionally similar organic red colorants in the anthraquinone family, whose photodegradation can cause irreversible color and stability changes, have long been used in works of art. Different organic reds, and their multiple chromophores, suffer degradation disparately. Understanding the details of these molecules' degradation therefore provides a window into their behavior in works of art and may assist the development of improved conservation methods. According to one proposed model of photodegradation dynamics, intramolecular proton transfer provides a kinetically favored decay pathway in some photoexcited chromophores, preventing degradation-promoting electron transfer (ET). To further test this model, we measured excited state lifetimes of substituted gas-phase anthraquinones using high-level theory to explain the experimental results. The data show a general structural trend: Anthraquinones with 1,4-OH substitution are long-lived and prone to damaging ET, while excited state intramolecular proton transfers promote efficient quenching for hydroxyanthraquinones that lack this motif.

Study of the multi-equilibria of red wine colorants pyranoanthocyanins and evaluation of their potential in dye-sensitized solar cells

Herein, a series of 3-O-glucosilated pyranoanthocyanin derivatives were synthesized following a bio-mimetic approach. The compounds were studied by means of UV–Vis spectroscopy in order to establish their chemical equilibria and determine the stability of the colored species over the pH range. The resistance of pyranoanthocyanins to hydration grants this family of compounds, closely related to anthocyanins, increased color stability. Finally, the synthetized compounds were successfully applied as light harvesters in DSSCs and relations between dye structure and cell efficiency were found. The influence of different linker units (carboxylate, catechol) and electron-donor groups (methoxy, hydroxyl, methyl), as well as the presence of sugar moieties have impact in the various parameters related to DSSC efficiency. An overall efficiency of 1.57% was obtained for the best performing compound, methylpyranocyanidin-3-O-glucoside. The impact of using different additives was also studied and the results compared with other families.

A Series of Ti6 Oxo Clusters Anchored with Arylamine Dyes: Effect of Dye Structures on Photocurrent Responses.

Dye molecules pre-anchored on titanium oxo clusters (dye-TOCs) are attractive as model compounds of dye-sensitized titanium oxide. To investigate the effects of the dye ligand structures of the dye-TOCs on photocurrent conversion, a series of dye-TOCs with the same Ti6 core structure and different antenna ligands (L) was synthesized and characterized crystallographically. The TOCs have the same structural formula of [Ti6 O4 L2 (O3 PPh)2 (OiPr)10 ]. Two types of dyes with para- or meta-substituted structures were designed and used as the ligands. The results show that charge transfer from the donor group to the TiO core of the TOCs with the para-substituted ligands is stronger than those with the meta-substituted ligands. The steric effect of the ligands also greatly influences the photocurrent density. Larger branched structures of the dye ligands reduce the coverage density of the dye-TOCs on TiO2 electrodes and also weaken the effective covalent bonding of the dye-TOCs on the electrode, and consequently, the photocurrent is decreased.

Photoacoustic effect of azo derivatives modified by click reagents and parceled by liposomes

Photoacoustic (PA) imaging has been highlighted as one of the latest and the most promising biophotonic diagnostic modalities. As promising contrast agents, near-infrared (NIR) light-absorbing agents are highly in great demand. Here, the PA and photothermal (PT) effects of a series of NIR absorbing azo derivatives were characterized. Interestingly, compared with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquiodimethane (TCNQ), the click reagent 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquiodimethane (F4-TCNQ) caused the red shift to near infrared (NIR) region for the peaks of PA intensity of molecules. Moreover, symmetrical molecular structure of NIR dyes had better PA effect. The M2a (clicked by TCNQ) molecules were embedded into hydrophobic phospholipid bilayer of liposomes (M2a⊂L) and internalized into human breast cancer Michigan Cancer Foundation-7 (MCF-7) cell. The toxicity of the cell was low, because the cell viability reached amost 100%, which was evaluated through CCK-8 assays to determine the metabolic viability of MCF-7 cells, while the cell PA intensity was high (1.5 × 103). The systematical research of the NIR dyes not only provided a series promising NIR dyes for imaging and treatment, but also guided the design of contrast agents and PT agents which had high PA and PT effects.

Synthesis of new thiophene dyes clubbed with sulfonamide for the creation of antibacterial polyester fabrics

The current study targets to synthesize some new sulfonamido-hydroxythiophene dyes for dyeing polyester fabrics with estimated antibacterial activity. The structure of sulfonamide dyes was adapted by conducting with sulfadimidine and sulfamethaxole through the coupling reaction. The synthesized derivatives were established by spectroscopic tools (Fourier transform infrared spectroscopy, proton nuclear magnetic resonance). Hydroxy-thiophene-containing sulfonamides were utilized for dyeing polyester fabric. The prepared sulfonamido-hydroxythiophene dyes were applied on polyester fabrics after establishing the optimum dye conditions, and afterward their dyeing properties, light, washing, perspiration, rubbing and sublimation fastness were determined. Meanwhile, the improved dyes demonstrated respectable fastness results and antibacterial properties against some gram-positive and gram-negative bacteria.

Solid-phase microextraction based on nickel-foam@polydopamine followed by ion mobility spectrometry for on-site detection of Sudan dyes in tomato sauce and hot-pot sample

Sudan dyes are one kind of synthetic azo dyes that are forbidden to use in foodstuffs according to the European Union Rule. In this work, considering the structure of Sudan dyes, nickel-foam@polydopamine (NF@PDA) was prepared through the self-polymerization of dopamine on the nickel-foam surface under weak alkaline conditions and used as SPME material to selectively extract the Sudan dyes. With the feature of three dimension (3D) cross-linked grid structure, large porosity and specific surface area, Ni-foam was selected as carrier material which can increase mass adsorption capacity. The primary parameters affecting extraction efficiency such as extraction time, extraction temperature, stirring speed, pH value, ionic strength and desorption time were investigated and optimized. After the Sudan dyes were eluted from the NF@PDA, the eluate was detected by IMS with a corona discharge (CD) ionization source. Thus, an innovative and rapid screening method coupling the NF@PDA to ion mobility spectrometry (IMS) was developed. Under the optimal extraction conditions, the detection limits for Sudan dyes were in the range from 0.005 μg g−1 to 0.25 μg g−1. The spiked recoveries were in the range from 81% to 91.3% by testing tomato sauce and hot-pot sample and validated by the UPLC-MS. Based on the results, the PDA coating has great ability for the extraction of Sudan dyes, mainly due to the catechol structure, electron-deficient quinones and amine groups on its surface. Thus, the developed method has great potential for on-site rapid screening of the Sudan dyes in food quarantine field.

Dependence of Dye Molecules Adsorption Behaviors on Pore Characteristics of Mesostructured MOFs Fabricated by Surfactant Template.

In this work, mesostructured metal-organic frameworks (MOFs) of MIL-101-Crs with different specific surface areas were synthesized successfully under solvothermal conditions using cationic surfactant cetyltrimethyl ammonium bromide (CTAB) as a structural template. It was found that crystallinity degrees, specific surface areas, and pore size distributions strongly depended on the loading of CTAB. Nitrogen adsorption and positron annihilation lifetime spectroscopy (PALS) results showed that the mean mesopore size increased with loading more CTAB due to the formation of larger templated mesopores. Although Langmuir adsorption of both methylene blue (MB) and methyl orange (MO) was confirmed in MIL-101-Crs, the experimental results showed different adsorption behaviors for them depending on the dye molecular size, pore structure, and charge properties of dye molecules/MOFs in solution. The MB molecules were found to be mainly adsorbed in the interspaces between grains and the templated mesopores, whereas the MO molecules were adsorbed in the inherent pores as well as the templated ones in MOFs due to the unsaturated metal sites' electrostatic attraction on them. Remarkably, MO adsorption capacity was observed to be proportional to the specific surface area, which allowed one to get a good linear fitting of experimental data. Interestingly, the good consistence between the fitting experimental parameter, that is, the number of adsorbed MO-s per unit specific surface area, and the calculated one according to our rough estimation strongly suggests that MO-s are electrostatically attracted and rotating around the unsaturated metal sites on MOFs' inner surfaces, which exclude other MO-s to be adsorbed around due to the "hindering effect" of the rotating motion.

Colorimetric and Fluorescence-Based Detection of Mercuric Ion Using a Benzothiazolinic Spiropyran

A merocyanine dye as a p-toluenesulfonate salt was synthesized. The structure of the dye was characterized using IR, NMR, HR-MS and single crystal X-ray crystallography. The X-ray crystallographic studies revealed the formation of a stacked aggregated structure of the merocyanine dye. The stacking interactions were investigated using the Crystal Explorer program, which estimated the strength of the interactions between different molecular pairs. The merocyanine dye was screened for affinity towards heavy metal ions, which revealed a color change from pink to colorless in the presence of mercuric ions, while other metal ions did not produce a similar change in color. In addition, the fluorescence spectroscopy indicated a change in the fluorescence intensity upon addition of mercuric ions. Both techniques displayed a good limit of detection value towards mercuric ions. In addition, the pixel intensity-based detection technique was also employed for the determination of limit of detection value with the help of a smartphone. The dynamic light scattering (DLS) studies indicated that the optical change occurred in the spectra of the receptor is due to the disaggregation of the receptor induced by mercuric ions. In addition, 1H-NMR studies were also used for investigating the mechanism of interaction between the receptor and the mercuric ions. The density functional theory (DFT) studies were used to investigate the formation of the complex at the molecular level, while time dependent density functional theory (TD-DFT) studies were used to understand the observed absorption spectra through the calculation of electronic excitation parameters, which indicated an increase in the energy difference between ground and the excited state.

Squaraine Dyes: Molecular Design for Different Applications and Remaining Challenges.

Squaraine dyes are a class of organic dyes with strong and narrow absorption bands in the near-infrared. Despite high molar absorptivities and fluorescence quantum yields, these dyes have been less explored than other dye scaffolds due to their susceptibility to nucleophilic attack. Recent strategies in probe design including encapsulation, conjugation to biomolecules, and new synthetic modifications have seen squaraine dyes emerging into the forefront of biomedical imaging and other applications. Herein, we provide a concise overview of (1) the synthesis of symmetrical and unsymmetrical squaraine dyes, (2) the relationship between structure and photophysical properties of squaraine dyes, and (3) current applications of squaraine dyes in the literature. Given the recent successes at overcoming the limitations of squaraine dyes, they show high potential in biological imaging, in photodynamic and photothermal therapies, and as molecular sensors.

Quantum-chemical study of oxophosphorus dipyrromethene (PODIPY) fluorophore coordination environment

Boron dipyrrin (BODIPY) fluorophores possess a range of excellent spectral characteristics, making their parent structure a useful scaffold for design of optically active molecules. Recently, new oxophosporus dipyrrin (PODIPY) compounds were introduced. They were shown to possess spectroscopic properties similar to those of corresponding BODIPY dyes. However, better solubility in polar solvents makes PODIPY better candidate for in vitro and in vivo fluorescent diagnostics. Here we give further insight into the structure and spectroscopic properties of the PODIPY dye. Theoretically predicted coordination center geometries correspond to the ones found experimentally for phosphorus phthalocyanines, corrolazines and other known P(V) heterocyclic complexes. DFT and WFT methods are employed to study geometrical, energetical and resulting spectral characteristics of the structural isomers.

Enhanced intramolecular charge transfer of organic dyes containing hydantoin donor: A DFT study

As a key factor for promoting electron transfer to the semiconductor, the intramolecular charge transfer (ICT) process in dye-sensitized solar cells (DSSCs) is crucial to enhancing the conversion efficiency. In this study, the effects of anchoring groups on charge transfer during dye excitation and interfacial electron injection from the dyes to the semiconductor were theoretically investigated. The calculation results indicate that the sensitizers with hydantoin anchoring groups, namely HY-4, HY-3, HQ-4, and HQ-3, can significantly adjust the orbital energy levels and increase the HOMO-LUMO energy gaps. Importantly, the ICT process of sensitizers before and after binding TiO2 cluster were detected via frontier molecular orbitals, electronic transition processes and transferred charges on the basis of the excitation (qCT), the transferred charge distance (dCT) and the dipole moment (μCT). The calculation results confirm that HY-4 and HY-3 greatly improve ICT performances relative to CA-4, which successfully interprets the experimentally observed efficiency difference. Moreover, the inserting acceptor moiety quinoxaline and hydantoin anchoring groups, namely HQ-4 and HQ-3, play an important role in raising the efficiency of ICT process. The finding can promote further understanding of the relationship between structure and performance of organic dyes containing hydantoin anchoring groups, so as to help them become more efficient dyes for DSSCs.

Dye-sensitized photocatalytic and photoelectrochemical hydrogen production through water splitting

This review points out some of our recent advancements in dye-sensitized photocatalytic and photoelectrochemical hydrogen production. The dye sensitization of a semiconductor (SC) surface plays a central role. The dye has the task to improve the light harvesting of the system and guarantees a fast charge transfer to the SC, while avoiding charge recombination reactions that might reduce its efficiency. The introduction of different features and exploitation of molecular designs led to the development of twelve new dyes with a “push–pull” di-branched structure. The design of the molecular structure and geometry improves light harvesting, stability under long-term irradiation, and surface properties. The dyes have been investigated in a photocatalytic device, and then the most representative molecules have been studied also in photoelectrochemical cells (PEC), in the presence either of a sacrificial electron donor (SED), or of a water oxidation catalyst (WOC). The planar structure of the carbazole-based dye enhanced the photocatalytic hydrogen production activity almost tenfold compared to the phenothiazine derivative characterized by a butterfly-like structure; the latter was endowed with a better performance in the photoelectrochemical hydrogen production.

Conformable Holographic Photonic Ink Sensors Based on Adhesive Tapes for Strain Measurements.

Buildings, bridges, and aircrafts are frequently exposed to fluctuation loads, which could start with a fine crack that instantly leads to unpredictable structure failures. The stationary strain sensors can be utilized, but they are costly and only detect limited deformation forms and sizes. Here, we fabricated photonic strain sensors on adhesive tapes, which can provide real-time monitoring of irregular surfaces. Holographic interference patterning was used to produce nonlinear curved nanostructures of one dimensional (1D) (900 nm × 880 nm) and two dimensional (2D) from a black dye film on a robust uniform adhesive layer and heat resistance tape. The patterned structure of the black dye was stable in broad pH environments. Diffracted light from the curved nanostructure detected the signal during structural damage, a shift or material tear of 5 με at less than 1.3 N cm-2. Additionally, the 2D nanostructure detected a surface change from x or y axis. Tilting the 1D structure within a range of 0.3° to 14.2° provided visible wavelength changes under broadband light to reveal early deflection signs. The curved nanopatterns could be also used for transferable holographic symbol design. Photonic nanopatterns on an adhesive tape could be used as a rapid response, conformable, lightweight, and low-cost dynamic strain sensor.

Synthesis, structure and photocatalytic degradation of organic dyes of a copper(II) metal-organic framework (Cu-MOF) with a 4-coordinated three-dimensional CdSO4 topology.

Metal-organic frameworks (MOFs) have attracted much interest in the fields of gas separation and storage, catalysis synthesis, nonlinear optics, sensors, luminescence, magnetism, photocatalysis gradation and crystal engineering because of their diverse properties and intriguing topologies. A Cu-MOF, namely poly[[(μ2-succinato-κ2O:O'){μ2-tris[4-(1,2,4-triazol-1-yl)phenyl]amine-κ2N:N'}copper(II)] dihydrate], {[Cu(C4H4O4)(C24H18N10)]·2H2O}n or {[Cu(suc)(ttpa)]·2H2O}n, (I), was synthesized by the hydrothermal method using tris[4-(1,2,4-triazol-1-yl)phenyl]amine (ttpa) and succinate (suc2-), and characterized by IR, powder X-ray diffraction (PXRD), luminescence, optical band gap and valence band X-ray photoelectron spectroscopy (VB XPS). Cu-MOF (I) shows a twofold interpenetrating 4-coordinated three-dimensional CdSO4 topology with point symbol {65·8}. It presents good photocatalytic degradation of methylene blue (MB) and rhodamine B (RhB) under visible-light irradiation. A photocatalytic mechanism was proposed and confirmed.

Mechanisms of the Photodissociation of Aminoazobenzene Rydimers into Monomers, According to Data from Ultrafast Laser-Probing Spectroscopy

The results from ultrafast laser-probing spectroscopy of photoexcited states of trans-aminoazobenzene (t-AAB) by means of ultrafast transient lens (UTL) and transient absorption spectroscopy (TAS) are analyzed. The analysis relies on earlier elaborated views of the rydimeric structure of azo dyes. It is shown that earlier reported UTL and TAS signals of aminoazobenzene (solutions in ethanol and heptanol) obeying the same laws of kinetic attenuation (a drop in the photo-induced refractive index of solvents for UTL and transient photoexcited Vis states of the dye for TAS) are in reality the mechanism of rydimer dissociation into two monomeric pairs. One of these pairs (consisting of neutral monomers) relaxes into the initial t-AAB2 rydimer according to two exponential kinetic curves with constants (characteristic times) of 0.7 and 2 ps (UTL) or 0.6 and 1.9 ps (TAS). The other pair consists of a t-AAB monomer and a monomer with two phenylaminyl-type cations and Vis absorption at 600–750 nm; it undergoes trans–cis isomerization according to a mono-exponential kinetic law with constants of 0.3 ps (UTL) and 0.2 ps (TAS).

Determination of the color removal efficiency of laccase enzyme depending on dye class and chromophore.

The aim of this article was to clarify which type of dye chromophores could be decolorized efficiently with the use of laccase enzyme. For this purpose, enzymatic degradation of different type of dye classes (4 reactive, 2 acid and 1 basic dye) having various chromophore groups was investigated by using commercial laccase from Cerrena unicolor. It was observed that the chromophore structure of dye is very important on enzymatic color removal efficiency. According to the experimental results, it was found that color removal efficiencies (20 mg/L initial dye) were 98.7% for RB220 (0.1 g/L enzyme after 6 h), 95.1% for RB19 (0.1 g/L enzyme after 48 h), 90.8% for AR42 (0.1 g/L enzyme after 48 h) while they were 60.9% for AR114 (0.25 g/L enzyme), 58.6% for RB21 (0.5 g/L enzyme), 39.7% for RR239 (0.25 g/L enzyme) even after seven days. As a result, it can be said that the highest decolorization rate was achieved for the reactive dye having formazan copper complex (RB220) chromophore. On the other hand, the enzymatic degradation of basic dye (BB9) was found to be rather difficult compared to the acid and reactive dyes used in this study and the maximum color removal was 42.8% after seven days.