Varying Dye Concentration Research Articles

Improving Quantum Yield of Upconverting Nanoparticles in Aqueous Media via Emission Sensitization.

We demonstrate a facile method to improve upconversion quantum yields in Yb,Er-based nanoparticles via emission dye-sensitization. Using the commercially available dye ATTO 542, chosen for its high radiative rate and significant spectral overlap with the green emission of Er3+, we decorate the surfaces of sub-25 nm hexagonal-phase Na(Y/Gd/Lu)0.8F4:Yb0.18Er0.02 upconverting nanoparticles with varying dye concentrations. Upconversion photoluminescence and absorption spectroscopy provide experimental confirmation of energy transfer to and emission from the dye molecules. Upconversion quantum yield is observed to increase with dye sensitization, with the highest enhancement measured for the smallest particles investigated (10.9 nm in diameter); specifically, these dye-decorated particles are more than 2× brighter than are unmodified, organic-soluble nanoparticles and more than 10× brighter than are water-soluble nanoparticles. We also observe 3× lifetime reductions with dye adsorption, confirming the quantum yield enhancement to result from the high radiative rate of the dye. The approach detailed in this work is widely implementable, renders the nanoparticles water-soluble, and most significantly improves sub-15 nm nanoparticles, making our method especially attractive for biological imaging applications.

Wool dyeing with binary mixture of natural dyes

Purpose – This paper aims to focus on the absorption behaviour of single and binary mixtures of natural dyes on wool. Natural dyes are multi-components with different structures and properties. Design/methodology/approach – In this research, the absorption behaviour of single and binary mixtures of natural dyes was investigated on wool fibre. Study was conducted via some natural dyes, including pomegranate peel as a yellow natural dye with tannin, weld as a yellow natural dye without tannin and madder as a red natural dye without tannin. Applied mordant was alum, which was used in the pre-mordant method. Different shades were obtained by varying dye concentration in the binary mixture. The effect of tannin on absorption behaviour of binary mixture of natural dyes was investigated by spectral reflectance and colour parameters of dyed samples measurements. Findings – Obtained results indicate that tannin affects the absorption behaviour of natural dyes in binary mixtures. Practical implications – Because natural dyes are multi-components with different structure and properties, the study of compatibility and absorption behaviour of natural dyes in binary mixture on wool is important in applied researches. Originality/value – The study of compatibility and absorption behaviour of binary mixture of natural dyes on wool is novel.

Equilibrium and kinetic studies for the removal of cationic dye using banana pith

The large quantity of green cull bananas has the potential of being used industrially and, thereby, to improve banana economics and eliminate the large environmental problem presented by banana waste. Wastewaters from textile, cosmetics, printing, dying, food colouring, and paper-making industries are polluted by dyes. The adsorption of basic dye by waste banana pith was investigated by varying dye concentrations, adsorbent dose, particle size and agitation rate. The adsorption capacity was found to be maximum value of removal by using 0.1 g of sorbent with particle size 1mm at mixing speed 200 rpm for initial concentration 25 mg/l to reach value of approximate 89%. The Langmuir, Temkin and Freundlich adsorption models were used for mathematical description of the adsorption equilibrium and it was found that experimental data fitted very well to these models except Langmuir model. Adsorption of dye was applied on (pseudo-first and pseudo-second-order kinetics), and the experimental data was more fitted to pseudo second order. The results of this study showed that banana pith could be employed as effective and low-cost materials for the removal of dyes from aqueous solutions.

Relative performance of biofilm configuration over suspended growth operation on azo dye based wastewater treatment in periodic discontinuous batch mode operation

Functional role of biofilm and suspended growth bioreactor configurations in response to the treatment of azo-dye (C.I. Acid Black 10B) bearing wastewater was evaluated in periodic discontinuous batch mode operation at varying dye concentrations. The biofilm system depicted higher dye removal efficiency (93.14%) compared to suspended mode (84.29%) at 350 mg dye/l operation. Both the reactor configurations did not show much process inhibition at higher dye loads studied. Azo reductase and dehydrogenase enzyme activities showed significant variation indicating the different metabolic capabilities of the native-microflora, stable proton shuttling between metabolic intermediates and differences in the delivery of reducing powers from the substrate metabolism towards dye removal. Voltammograms visualized marked variations in electron discharge properties with the function of reactor configuration, time intervals and dye load. Higher redox catalytic currents, lower Tafel slopes and polarization resistance showed good correlation with enzyme activities and dye removal.

Liquid crystal-directed assembly and phase morphology of a squaraine dye

The squaraine (SQ) dye, 2,4-bis [4-(N,N-di-n-hexylamino)-2-hydroxyphenyl]squaraine was synthesised, and a series of SQ dye/cholesteryl pelargonate binary mixtures with varying dye concentrations (1%, 3%, 7.5%, 10.8%, 15% and 20% w/w) were prepared. Their phase transitions were investigated using differential scanning calorimetry, polarised light microscopy and X-ray diffraction. The SQ dye itself exhibited no liquid crystalline behaviour. The concentration of the dye in the cholesteric compound proved to have a significant effect on the dye aggregation behaviour and phase transitions in cholesteryl pelargonate, resulting in the appearance of new mesophases and the formation of J- and H-aggregates. The texture morphology, X-ray diffraction data and UV–vis absorbance spectra provide strong evidence of the viability of liquid crystal-directed assembly of the SQ dye.

Chemically modified sugarcane bagasse as a potentially low-cost biosorbent for dye removal

The use of adsorbent prepared from sugarcane bagasse, an agro waste from sugar industries has been studied as an alternative substitute for activated carbon for the removal of dyes from wastewater. Adsorbents prepared from sugarcane bagasse were successfully used to remove the methyl red (MR) from an aqueous solution in a batch reactor. This study investigates the potential use of sugarcane bagasse, pretreated with phosphoric acid (SBC), for the removal of methyl red from simulated wastewater. Phosphoric acid treated sugarcane bagasse was used to adsorb methyl red at varying dye concentration, adsorbent dosage, pH and contact time. A similar experiment was conducted with commercially available powdered activated carbon (PAC) and untreated sugarcane bagasse (SB) in order to evaluate the performance of SBC. The adsorption efficiency of different adsorbents was in the order PAC > SBC > SB. The initial pH 3 to 6 favoured the adsorption of synthetic dyes by both SBC and SB. This prepared adsorbent was very efficient in decolorized diluted solution. It is proposed that SBC, in a batch or stirred tank reactors could be employed as a low-cost alternative in wastewater treatment for dyes removal.

Effects of Dye Loading Conditions on the Energy Conversion Efficiency of ZnO and TiO2 Dye-Sensitized Solar Cells

In this paper, we report the significant effects of dye loading conditions on the overall light conversion efficiency of zinc oxide (ZnO) film electrodes in dye-sensitized solar cells. A comparison of the ZnO film electrodes was also made with TiO2 film electrodes prepared with similar dye loading conditions. It was found that using a higher and lower dye concentration requires a shorter and longer immersion time, respectively, for optimal sensitization of ZnO to obtain maximum efficiencies. A similar trend was found for the TiO2 film electrode as well; however, smaller differences in the overall light conversion efficiencies were observed with varying dye concentration and immersion time. It was found that the chemical stability was an issue for the ZnO film electrodes but was not pertinent for the TiO2 film electrodes. The film quality and structure of the ZnO film differed after prolonged immersion in high dye concentration, where the formation of N3 dye and Zn2+ aggregates and/or the deterioration of ...

Decolorization and partial degradation of monoazo dyes in sequential fixed-film anaerobic batch reactor (SFABR)

Decolorization of two monoazo dyes, acid orange 6 (AO6) and acid orange 7 (AO7), were studied in sequential fixed-film anaerobic batch reactor (SFABR) with varying dye concentrations and 500 mg/L glucose as the co-substrate. More than 90% dye decolorization could be achieved, even at 300 mg/L, with both AO6 and AO7 and dye decolorization rates were 168 mg/L/d and 176 mg/L/d, respectively. COD removals with these two monoazo dyes were significantly different, as 75% and 35% decrease were observed with AO6 and AO7, respectively. UV–visible spectral as well as HPLC analysis of SFABR treated effluent showed the accumulation of 4-aminobenzenesulfonate (4-ABS) from AO6 and AO7. Aminoresorcinol (AR) formed from AO6 decolorization could not be detected at the end of SFABR cycle. This along with high COD removal indicated its further degradation. Formation of pink coloration on exposure to air indicated the presence of 1-amino-2-naphthol (AN) in AO7 fed reactor effluent. Thus both 4-ABS and AN were resistant to further degradation under anaerobic conditions. Presence of nitrate did not decrease the observed decolorization at the end of 24 h SFABR cycle, although initial rate was decreased. This indicates the suitability of SFABR configuration for the treatment of azo-dye containing wastewaters in the presence of nitrate.

Dye Removal from Aqueous Solution by using Adsorption on Treated Sugarcane Bagasse

The use of cheap and ecofriendly adsorbents has been studied as an alternative substitution of activated carbon for the removal dyes from wastewater. Adsorbents prepared from sugarcane baggase-an agro industries waste was successfully used to remove the methyl red from an aqueous solution in a batch reactor. This study investigates the potential use of sugarcane baggase, pretreated with formaldehyde (PCSB) and sulphuric acid (PCSBC), for the removal of methyl red from simulated wastewater. Formaldehyde treated and sulphuric acid treated sugarcane bagasse were used to adsorb methyl red at varying dye concentration, adsorbent dosage, pH and contact time. Similar experiment was conducted with commercially available powdered activated carbon (PAC), in order to evaluate the performance of PCSB and PCSBC. The adsorption efficiency of different adsorbents was in the order PAC>PCSBC>PCSB. The initial pH of 6-10 flavors the adsorption of both PCSB and PCSBC. Adsorbents are very efficient in decolorized diluted solution. It is proposed that PCSB and PCSBC, in a batch or stirred tank reactors could be employed as a low cost alternative in wastewater treatment for the dye removal.

Decolorization Screening of Synthetic Dyes by Anaerobic Methanogenic Sludge Using a Batch Decolorization Assay

The nonspecific ability of anaerobic sludge bacteria obtained from cattle dung slurry was investigated for 17 different dyes in a batch assay system using sealed serum vials. Experiments using Reactive Violet 5 (RV 5) showed that sludge bacteria could effectively decolorize solutions having dye concentrations up to 1000 mg l−1 with a decolorization efficiency of above 75% during 48 h of incubation. Headspace gas composition of anaerobic batch systems for varying dye concentration revealed that lower concentrations of RV 5 (upto 500 mg l−1) were found to be stimulatory to the methanogenic activity of sludge bacteria. However at higher dye concentrations, the headspace gas composition was found to be similar to batch assay controls without dye, indicating that dye at higher concentrations was inhibitory to methanogenic bacteria of sludge. The optimum inoculum and incubation temperature for maximum decolorization of RV 5 was found to be 9.0 g l−1(in terms of total solids) and 37°C, respectively. Of sixteen other dyes tested, nine (Reactive Black 5, Reactive Blue 31, Reactive Blue 28, Reactive Red HE8B, Reactive Yellow, Reactive Golden Yellow, Mordant Orange, Novatic Olive R S/D & Navilan Yellow GL) were decolorized with more than 88% efficiency; three (Orange II, Navy Blue HER & Novatic Blue BC S/D) were decolorized with about 50–65% efficiency, whereas other three dyes (Procion Orange H2R, Procion Brilliant Blue HGR & Novatic Blue BC S/D) were decolorized with less than 40% efficiency. Though Ranocid Fast Blue was decolorized with about 92.5% efficiency, this was merely due to sorption, whereas the other dyes were decolorized due to biotransformation.

Dye removal from aqueous solution by adsorption on treated sawdust

Formaldehyde treated and sulphuric acid treated saw dusts were used to adsorb malachite green at varying dye concentration, adsorbent dose, pH and agitation time. Similar experiments were conducted with laboratory grade activated carbon to compare the results. The adsorption efficiency of sulphuric acid treated sawdust (SD) was higher than formaldehyde treated SD. The adsorption followed first order rate expression and Lagergren equation. An initial pH in the range of 6–9 was favorable for the dye removal by both the adsorbents. Dilute solutions were effectively decolorized by the adsorbents. It is proposed that in batch or stirred tank reactors, both adsorbents can be an attractive option for dye adsorption.

Plasma polymerized hexamethyldisiloxane (HMDS) barrier layers

The number of applications employing polymeric optical materials is growing rapidly due to recent advances in telecommunications, display, and laser markets. For a number of these applications, organic dyes (chromophores) are added to the polymer host to add linear or nonlinear optical properties to the system. In homogeneous systems, dye diffusion is not an issue; however in multiple stacks of polymer films with different dye concentrations or in films with a spatially varying dye concentration, diffusion becomes important. We report here on initial studies to control the diffusion of the dye, zinc octabromylporpyhrin (ZnOBP), doped in poly(dimethylsiloxane) films, from diffusing into other layers in multiple stack systems. Plasma enhanced chemical vapor deposition (PECVD) was utilized to deposit thin films (60–240nm) of hexamethyldisiloxane (HMDS) at the interface of two separate polymer layers, one with and one without ZnOBP. The diffusion of the chromophore to the outside surface of the undoped layer was examined with and without the plasma polymerized barrier layer. The thin but highly crosslinked interlayer is found to be an effective barrier to diffusion as measured using X-ray photoelectron spectroscopy to track bromine diffusion.

Equilibrium binding of DAPI and 7-aminoactinomycin D to chromatin of cultured cells.

The binding of 4',6-diamidino-2-phenylindole (DAPI) and 7-aminoactinomycin D (7-AAMD) to chromatin of intact cultured fibroblast nuclei was studied by cytofluorometry. Staining was performed at equilibrium at varying dye concentrations. By using large volumes of dye solutions, the free dye concentration became approximately equal to total dye concentration, and the estimation of affinity and number of binding sites was performed by Scatchard analysis. Since all Scatchard plots showed a definite curvature, indicating more than one class of binding sites, a two component regression was performed, although only the highest affinity binding sites were determined. The observed affinity constants did not change substantially between different preparational procedures for any of the dyes. The number of DAPI binding sites increased about 30% after detergent extraction. No such increase was observed for 7-AAMD. Fixation in formaldehyde, instead of ethanol, after detergent extraction had no effect on DAPI binding, but decreased the number of 7-AAMD binding sites with about 50%. Extraction of basic proteins with HCl resulted in about 100% increase of the number of binding sites for both dyes. It should be feasible to use this technique as an assay for the identification of proteins or other nuclear components important for the maintenance of chromatin structure.