Dye Absorption Research Articles

Implanting N-doped CQDs into rGO aerogels with diversified applications in microwave absorption and wastewater treatment

In this work, water-soluble nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by a one-step hydrothermal method, and then implanted into graphene aerogels to obtain N-CQDs/rGO composites. Herein, N-CQDs, as connection sites and channels in rGO, can effectively promote electron jumping and migration and greatly enhance the conduction loss of rGO. As expected, the composites exhibit excellent microwave absorption performance with ultra-wide effective absorption bandwidth of 7.36 GHz and ultra-high minimum reflection loss (RLmin) of −69.42 dB at an ultra-low filler loading of 5 wt%. An ultra-low bulk density of the N-CQDs/rGO composite reach as 4.24 mg/cm3. Actually, the outstanding performance of microwave absorption is attributed to the specific surface morphology and porous structure, enhanced conduction loss and good impedance matching. Meanwhile, the as-synthesized composites display the typical selective adsorption ability for dyes in the wastewater, where the maximum adsorption capacity for methylene blue (MB) dyes is 261 mg/g. Briefly, the study provides a new approach on the comprehensive environmental application of CQDs/graphene composites with both high-performance microwave absorption and high-efficiency removal of organic dyes in the wastewater.

Near-infrared absorption and photothermal properties of heptamethine pyrylium dyes with bistriflimide anion

Numerous research endeavors have focused on the near-infrared (NIR) absorption properties and applications of polymethine dyes. Herein, we synthesize two heptamethine pyrylium dyes, TBCY-5 and TBCY-6, containing 5- and 6-membered, respectively, rings in the π-conjugated bridge, thus producing NIR dyes with maximum absorption exceeding 1000 nm. The effect of counter anions on the NIR absorption property was examined by exchanging perchlorate (ClO4) anions with bistriflimide (TFSI) anions. TBCY dyes with TFSI possessed good solubility and a high molar extinction coefficient compared to the dyes with ClO4. TBCY-5 and TBCY-6 showed negative solvatochromism, exhibiting a hypsochromic shift of the NIR absorption in polar solvents. Photothermal experiments revealed that TBCY-5 and TBCY-6 were suitable as efficient photothermal materials.

Electrospun PVDF/ZnO Based Composite Fibers for Oil Absorption and Photocatalytic Degradation of Organic Dyes from Waste Water

Electrospun PVDF/ZnO Based Composite Fibers for Oil Absorption and Photocatalytic Degradation of Organic Dyes from Waste Water

1,6,7-Trisubstituted perylene bisimides with tunable optical properties for colorimetric and “turn-on” fluorescence detection of HCl

To elucidate the effect of different substituents on the optical and redox properties of perylene bisimide (PBI), a novel series of 1,6,7-trisubstituted PBIs (1–6) with a highly twisted perylene core was synthesized and characterized. By substituting the hydrogen atoms at the bay-positions with various substituents (dihexylamino, piperidinyl, morpholinyl, hexoxy, and bromo), the absorption and fluorescence wavelengths of 1–6 in cyclohexane were extensively tuned within the ranges of 551–646 and 586–720 nm, respectively, simply by harnessing the electron-donating strength of the substituents. Varying the substituents generated a new family of long-wavelength absorbing and fluorescent dyes. Moreover, PBI 2 exhibited colorimetric and “turn-on” fluorescence responses in extremely acidic medium (pH 1.0 to −0.6). Low-cost test strips containing 2 were easily prepared and could be used to detect HCl.

Chitosan- and Alginate-Based Hydrogels for the Adsorption of Anionic and Cationic Dyes from Water.

Novel hydrogel systems based on polyacrylamide/chitosan (PAAM/chitosan) or polyacrylic acid/alginate (PAA/alginate) were prepared, characterized, and applied to reduce the concentrations of dyes in water. These hydrogels were synthetized via a semi-interpenetrating polymer network (semi-IPN) and then characterized by Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), and their swelling capacities in water were measured. In the adsorption experiments, methylene blue (MB) was used as a cationic dye, and methyl orange (MO) was used as an anionic dye. The study was carried out using a successive batch method for the dye absorption process and an equilibrium system to investigate the adsorption of MO on PAAM/chitosan hydrogels and MB on PAA/alginate in separate experiments. The results showed that the target hydrogels were synthetized with high yield (more than 90%). The chemical structure of the hydrogels was corroborated by FTIR, and their high thermal stability was verified by TGA. The absorption of the MO dye was higher at pH 3.0 using PAAM/chitosan, and it had the ability to remove 43% of MO within 10 min using 0.05 g of hydrogel. The presence of interfering salts resulted in a 20–60% decrease in the absorption of MO. On the other hand, the absorption of the MB dye was higher at pH 8.5 using PAA/alginate, and it had the ability to remove 96% of MB within 10 min using 0.05 g of hydrogel, and its removal capacity was stable for interfering salts.

Fluorine-Free Superhydrophobic Covalent-Organic-Polymer Nanosheet Coating for Selective Dye and Emulsion Separation.

Covalent organic polymer nanosheets (COPNs) endowed with porous networks and large surface areas in their structures offer great advantages over other materials in addressing environmental problems. In this study, fluorine-free superhydrophobic COPNs were designed and applied to selective dye absorption. Notably, COPNs selectively adsorb dyes with a high hydrophobic index (HI) and reject low HI dyes with maximum adsorption capacities of 361 and 263 mg/g for crystal violet and methylene blue, respectively. The adsorption isotherm model showed that the COPNs follow the Langmuir adsorption isotherm model and pseudo-second-order kinetics. Next, we explored the superhydrophobicity of the COPNs by in situ fabrication with melamine sponge (COPNs-MS), which incorporates the superhydrophobicity of COPNs [water contact angle (WCA) of >150°] with the structure and flexibility of the MS skeleton. The COPNs-MS shows various oil-adsorbing properties with good adsorption capacity (from 60 to 120 g/g) and also effectively separates various surfactant-stabilized emulsions with a separation efficiency of over 99%. The as-fabricated COPNs-MS retains its superhydrophobicity in various solvents and hazardous conditions (WCA ≥ 150°) and exhibits good flame retardancy and excellent compression properties with excellent antifouling property due to the superhydrophobic COPN coating. Furthermore, COPNs-MS also demonstrates excellent recyclability because the strong COPN coating in the MS skeleton retains its hydrophobicity. Therefore, our fluorine-free superhydrophobic COPNs are not only capable of selective dye adsorption but also exhibit very good oil adsorption and surfactant-stabilized emulsion separation performance.

Theoretical Study of the Vibronic Structure of the Absorption and Fluorescence Spectra of Thiazine Dyes

Theoretical Study of the Vibronic Structure of the Absorption and Fluorescence Spectra of Thiazine Dyes

Effective Removal of Reactive Yellow 145 (RY145) using Biochar Derived from Groundnut Shell

The decolorization of reactive yellow 145 from wastewater in batch mode of operation using groundnut shell-based biochar was studied in the present research. The adsorption process was studied by investigating the effects of different adsorption variables such as temperature, initial dye concentration, pH, and biochar dosage. The results showed that biochar dosage had a substantial impact on dye absorption potential. The equilibrium biochar dosage was determined to be 1 g/L, with an absorption capacity of 7.33 mg/g. The effect of pH was examined by varying between 2.0 and 5.0, and equilibrium pH was obtained at pH 2.0. The effect of temperature was examined by varying temperature ranges from 30 to 45°C, and the optimum condition was identified as 35°C. The characteristics of biochar were studied using analytical instruments, and results concluded that dye sorption onto biochar resulted in variation of biochar. Desorption studies were carried out to evaluate the biochar potential by examining various elutants and altering the solid to liquid ratio. Groundnut shell-generated biochar was reported to remediate dye-bearing Remazol wastewater with a removal effectiveness of about 62% based on the experimental data.

Integration of Chitosan and Sugar Cane Bagasse as Adsorbent for Remazol Red Dyes Removal

In this study, the sugarcane bagasse biomass was modified and purpose as a bio-adsorbent to remove Remazol red dye from wastewater. The sugarcane bagasse was calcined at 200˚C, followed by the treatment with 1% chitosan solution. The adsorbent was morphologically characterized using FTIR, SEM, XRD analysis to study further the effect of chemical modification techniques on calcined biomass of sugarcane bagasse. Treated calcined sugarcane showed an irregular surface and appearance of pores effects of an acidic chitosan solution. It also clarified the presence of an active site for dye absorption on the adsorbent's surface, which is necessary for the dye adsorption attachment site. The adsorption performance revealed that treated sugarcane bagasse performed better with an optimum adsorbent dosage of 150 mg at an equilibrium time of 60 min. Remazol Red removal favored acidic conditions at pH 4 and decreased as dye concentration increased. With an R2 value, the equilibrium data adsorption fitted well with the Langmuir adsorption isotherm.

Excitations of safranin and phenosafranin in aqueous solution: Comparative theoretical analysis

In the present work, the excitations of safranin (SAF) and phenosafranin (PheSAF) in an aqueous solution are analyzed by DFT/TD-DFT, considering the vibronic transitions and hydration. The frontier orbitals, transitions between which cause the absorption and emission of dyes in the visible region of the spectrum, almost do not cover benzene rings and methyl groups of molecules. As a consequence, benzene rings, aromatic hydrogen atoms, as well as SAF methyl groups are not covered by the change in electron density. These features explain the same excitation energies of SAF and PheSAF observed experimentally. At the same time, during relaxation to an excited equilibrium state, the changes in the vast majority of atomic charges again turn out to be different for SAF and PheSAF, which causes a slight difference between the emission energies of dyes. Excitations of both dyes do not lead to twisting of their benzene rings relative to the chromophores - the dihedrals between them are strictly φ = 90°. The thermal twisting of these dihedrals is practically free up to Δφ∼±30°, and then it is sharply hampered. The heights of potential barriers separating their energy minima are very high (∼400 kT). The increase in the dipole moments upon excitation is due to the greatest extent to the significant increase in the electron densities at the N10 atoms of both dyes. All five H-bonds of each of the dyes with water are strengthened upon excitation. The strongest and most enhanced due to excitation are the H-bonds of waters with the N10 atoms. There is a strong photoinduced polarization of water molecules bound to the N10 atoms of the dyes. H-bonds with water of amino groups are stronger in PheSAF, and with the N10 atom, in SAF. The influence of hydrating water molecules leads to significant bathochromic shifts of the maxima of the calculated spectra (23 nm for SAF and 22 nm for PheSAF) relative to the purely implicit specification of the solvent.

Application of Achillea millefolium extract as a reducing agent for synthesis of silver nanoparticles (AgNPs) on the cotton: antibacterial, antioxidant and dyeing studies.

The phyto-synthesis of silver nanoparticles and cotton dyeing with natural colorants can reduce the environmental impact of the process considerably. In this study, the extraction of natural colorants from Achillea millefolium petals was optimized by ultrasound technique. The AMP extract was applied for synthesis of silver nanoparticles (Ag NPs) on the cotton fabrics. The dyeing, antibacterial and antioxidant characteristics of cotton samples were investigated to optimize the process and evaluate its efficiency. The AMP extract had good substantivity towards cotton fabrics and the presence of tannic acid, as an environmentally-friendly mordant, further improved the absorption of AMP dye. The antibacterial and antioxidant activities of the dyed samples with AMP extract of were 50%and 60%, respectively. The addition of TA and Ag enhanced the antibacterial and antioxidant activities on the cotton samples to over 99%.

Theoretical Modeling of Absorption and Fluorescent Characteristics of Cyanine Dyes

The rational design of cyanine dyes for the fine-tuning of their photophysical properties undoubtedly requires theoretical considerations for understanding and predicting their absorption and fluorescence characteristics. The present study aims to assess the applicability and accuracy of several DFT functionals for calculating the absorption and fluorescence maxima of monomethine cyanine dyes. Ten DFT functionals and different basis sets were examined to select the proper theoretical model for calculating the electronic transitions of eight representative molecules from this class of compounds. The self-aggregation of the dyes was also considered. The pure exchange functionals (M06L, HFS, HFB, B97D) combined with the triple-zeta basis set 6-311+G(2d,p) showed the best performance during the theoretical estimation of the absorption and fluorescent characteristics of cyanine dyes.

Plasmonic Bipyramidal Au Nanoparticles Enhance Near-Infrared Nonlinear Absorption of Dyes Confined in Sol–Gel Materials: Implications for the Safe Utilization of Lasers

Plasmonic Bipyramidal Au Nanoparticles Enhance Near-Infrared Nonlinear Absorption of Dyes Confined in Sol–Gel Materials: Implications for the Safe Utilization of Lasers

Indirect Spectrophotometric Determination of Famotidine and Ciprofloxacin Hydrochloride in Pharmaceuticals Using N-Bromosuccinimde and Janus Green B Dye.

An indirect simple and sensitive spectrophotometric method has been developed for the determination of famotidine (FAM) and ciprofloxacin hydrochloride (CIP) in pure and pharmaceutical dosages. The method is based on the oxidation of FAM and CIP with known excess of N-Bromosuccinimde in acidic medium and subsequent occupation of unreacted oxidant in decolorization of Janus green B dye and measure the absorbance of residual dye at 618 nm. Calibration curves of residual Janus green B dye in the presence of FAM or CIP were rectilinear over the ranges 1.0-10.0 and 1.0-7.5 µg/ml with molar absorptivity 3.61×104 and 5.14×104 l.mol-1.cm-1 respectively. The accuracy (average recovery) was ranged between 99.68 and 100.23% and precision (RSD%) is less than 3.80%. The developed method was successfully applied for the determination of the studied drugs in their pharmaceutical preparations. The results obtained are in agreement with certified values of pharmaceutical preparations and also with standard addition procedure and standard method applied in state company for drugs industry and medical appliance,SDI.

OPTIMIZATION OF REACTIVE DYEING PROCESS FOR CHITOSAN TREATED COTTON FABRIC

The colour of textiles plays an important role in the marketability of fabrics, due to its psychological and eye-catching effects on consumers. Synthetic dyes are widely used in the textiles industry due to their ability to reproduce different colours and shades, easy application method and huge production to fulfill the demands of ever-increasing population. Reactive dyes are most commonly used for cotton fabric, due to their brilliant colours and good washing fastness. However, the major problem with reactive dyes is that they consume huge amounts of alkali or salts as mordant for the fixation of dyes on cotton fabric. Most of the commercial dyeing units and textile export houses have started seeking possibilities to use safe synthetic dyes for dyeing different textiles for targeting the niche market. For that purpose, appropriate standardized scientific dyeing techniques and procedures need to be adopted. In the present study, the use of chitosan as mordant, instead of alkali or salt, was investigated for dyeing cotton fabric with reactive red dye, and the dyeing variables were optimized to attain the maximum colour strength value. The results of study showed that higher percent dye absorption (78.90%), colour strength (18.72) and good wash fastness rating (4/5) were achieved for the chitosan treated dyed fabric, compared to the alkali treated dyed sample (68.36% and 13.03, respectively).

Synthesis and characterization of solid-state Fe-exchanged nano-bentonite and evaluation of methyl orange adsorption.

A new adsorbent was synthesized using ion-exchange between iron salts and bentonite modified with acetyl trimethylammonium bromide (CTAB) in the solid phase. Ion-exchange was performed in the solid state at a temperature of 100°C for 2min. Various analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), porosity measurement (BET), infrared Fourier transform (FT-IR), transmission electron microscopy (TEM), X-ray energy diffraction (EDX), and thermal weighing (TGA) were used to characterize the synthesized nano-adsorbents. Under optimal conditions (pH = 7, time 60min, concentration of dye solution 150ppm, and amount of nano-adsorbent 0.75g/l), the modified nano-adsorbent absorbed 73% of the methyl orange (MO) dye. Adsorption isotherm studies and kinetic model showed that the pseudo-second-order model and Langmuir equation agree with the obtained results. After three reductions of the modified nano-adsorbent in the photo-Fenton process, the dye absorption percentage was 69.50%.

Influence of Sequential Liquid Ammonia and Caustic Mercerization Pre-Treatment on Dyeing Performance of Knit Cotton Fabric.

A two-stage sequential pretreatment including caustic mercerization (CM) and liquid ammonia (LA) treatment was applied to investigate the influence on dyeing performance and handle of knit cotton fabric, and the relationship between dye size and dyeing properties. Various techniques were applied to characterize all the treated fabrics. X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analyses of the treated fabrics confirmed that both sequential treatments decreased the crystallinity of cotton fabric more than only the CM or LA treatment. The pattern of cellulose I was transferred to a mixed configuration of cellulose II and cellulose III after the CM/LA or LA/CM treatment. Thermal performances measured by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) techniques showed that the thermal stability of the treated cotton only marginally decreased. The wicking height increased after the sequential CM/LA treatment, indicating that the hydrophilicity of the fabric increased. The dye absorption and color uniformity were better for the reactive dye with a smaller molecular weight (Reactive Red 2) compared with the one with a larger molecular weight (Reactive Red 195). The total dye fixation efficiency (T%) increased to 72.93% and 73.24% for Reactive Red 2 dyeings of CM/LA- and LA/CM-cotton fabric from 46.75% of the untreated fabric, respectively; the T% increased to 65.33% and 72.27% for Reactive Red 195 dyeings of CM/LA- and LA/CM-cotton fabric from 35.17% of the untreated fabric, respectively. The colorfastness and dye exhaustion and fixation percentages of the samples were enhanced after the treatments. Furthermore, compared to the single CM or LA treatment, the softness handle properties were further improved after the fabrics were sequentially treated by CM/LA. The developed pre-treatment of CM/LA can be used in the textile industry to promote the dyeability, handle, and mechanical properties of knit cotton fabrics.

Effects of auxiliary electron-withdrawing moieties on the photovoltaic properties of D-π-A’-π-A phosphonic acid-based DSSCs

Dye-Sensitized Solar Cells (DSSCs) that are based on a donor-bridge-acceptor-bridge-donor (D-π-A’-π-A) oligothiophene dye-containing benzothiadiazole mono-functionalized by a phosphonic acid were theoretically studied during the changing of the auxiliary acceptor (A’) by six other auxiliary acceptors. To further understand the molecular structure of these series of dyes, a density functional theory (DFT) calculation was performed to study the molecular geometries, frontier molecular orbitals (FMO) by employing the method B3PW91 with the basis set 6-311G(d) for the soft atoms (H, C, N, O, P, Si, S) and LANL2DZ for the heavy atoms (Se, Te). The optical properties of the free and the adsorbed dyes were modelled using TD-DFT simulations employing the functional BHandH. The calculated absorption spectra of the designed dyes indicate that the change of electron-withdrawing groups increases the absorption wavelength significantly. Our results showed that the BTD, BXD, BTED, BSED, BIA, and BSD dyes exhibit a narrower HOMO–LUMO energy gap than BTZ dye. This led to a broader optical absorption and lower oscillator strength in dyes containing Benzimidazole, Benzosiladiazole, Benzoselenodiazole, and Benzotellurodiazole moieties that were verified to be better auxiliary acceptor units. The simulated absorption spectra of the adsorbed dyes on (TiO2)9 are red-shifted compared to the free dye. The adsorption energies of all dyes are similar which reveals that the adsorption energy is not depending on the auxiliary moiety but rather on the anchor group. Therefore, it is expected that the results obtained from this investigation will have a substantial impact on the development of DSSC of phosphonic acid-based dyes.

Highly efficient oxidative degradation of organic dyes by manganese dioxide nanoflowers

MnO2 nanoflowers were synthesized using one pot chemical precipitation method. The MnO2 nanoflowers consisted of intersected nanosheets. XRD, HRTEM and BET analyses indicate that the MnO2 nanoflowers contained amorphous structure with surface area of 253 m2/g and pores size of 79.3 Å. The catalytic performance of MnO2 nanoflowers to degrade Rhodamine (RhB) without optical light source was examined. It performed well under acidic condition (pH 3) with 99.0% of removal efficiency in 10 min. The oxidative degradation mechanism of RhB by MnO2 nanoflowers was proposed based on a few findings. First, the crystal defects in the amorphous structure facilitated a series of oxidative degradation process. Second, the formation of Mn2+ in acidic condition catalysed the formation of hydroxyl free radicals for the degradation of RhB. Third, the high surface area-to-volume ratio of nanoflowers provided large area for the absorption of RhB dye. From practical perspectives, the MnO2 nanoflowers showed excellent repeatability on its removal performance by recording 98.4% removal efficiency even after 5 repeated cycles. The MnO2 nanoflowers also showed good removal efficiency on industrial dye waste sample. This catalyst is envisioned to hold great promise for organic wastewater treatment with virtues of high efficiency and excellent repeatability performance.

Natural Dyeing of Modified Cotton Fabric with Cochineal Dye.

Natural dyes are not harmful to the environment owing to their biodegradability. For dye application to textiles, salts are necessary as mordant or electrolytes and make an environmental impact. In this paper, the influence of cationization during mercerization to the dyeing of cotton fabric with natural dye from Dactylopius coccus was researched. For this purpose, bleached cotton fabric as well as fabric cationized with Rewin OS was pre-mordanted using iron(II) sulfate heptahydrate (FeSO4·7H2O) and dyed with natural cochineal dye with and without electrolyte addition. For the characterization of surface changes after cationization, an electrokinetic analysis on SurPASS was performed and compared to pre-mordanting. For determination of dye exhaustion, the analysis of dye solution was performed on a UV/VIS spectrophotometer Cary 50 Solascreen. Spectrophotometric analysis was performed using a Datacolor 850 spectrophotometer, measuring remission ”until tolerance” and the whiteness degree, color parameters, color depth (K/S), and colorfastness of dyed fabric were calculated. Levelness was determined by visual assessment. Cationized cotton fabrics showed better absorption and colorfastness. Pre-mordanting and cationization showed synergism. The electrolytes improved the process of dye absorption. However, when natural dyeing was performed on cotton fabric cationized during mercerization, similar chromacity, uniform color, and colorfastness were achieved with and without electrolyte, resulting in pure purple hue of cochineal. For achieving a violet hue, pre-mordanting with Fe-salt was needed. Therefore, salt can be reduced or even unnecessary, which makes this process of natural dyeing more environmentally friendly.