Dye Adsorption Ability Research Articles

A comparative study on the photocatalytic activities of two visible-light plasmonic photocatalysts: AgCl-SmVO4 and AgI-SmVO4 composites

Two novel plasmonic photocatalysts, AgCl-SmVO4 and AgI-SmVO4 composites, were prepared in this study. The two photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The results showed that the prepared samples have a similar phase composition. The two photocatalysts both consist of SmVO4, AgX (X=Cl, I), and Ag. However, their photocatalytic activities varied significantly. The photocatalytic testing result showed that the AgI-SmVO4 hybrid exhibited a photocatalytic activity approximately three times higher than that of AgCl-SmVO4 in the photodegradation of rhodamine B under visible-light illumination. In addition to the strong adsorption ability for dyes, the suitable band potential of AgI and SmVO4 was considered as another important reason for the higher photocatalytic activity of AgI-SmVO4. It was suggested that this excellent property would lead to a high separation efficiency of electron-hole pairs, improving the photocatalytic activity. This speculation was further verified by the photocurrent-time and active species trapping measurements.

An Amorphous Coordination Polymer with High Adsorption Ability for Anionic Dyes from Aqueous Solution

An Amorphous Coordination Polymer with High Adsorption Ability for Anionic Dyes from Aqueous Solution

Facile green synthesis of nickel nanostructures using natural polyol and morphology dependent dye adsorption properties

Ni nanostructures were synthesized using only castor oil (CSO), a natural polyol through green chemistry. CSO acts as multifunctional reagent (solvent, reducing agent, template, surface modifier) for the synthesis of the Ni nanostructures and imparts dye adsorption ability. The morphology of the nanostructures was found to be influenced by variations in the precursor concentration. A three molar concentration resulted in the formation of nanorods (ca. 11 × 75 nm) due to a higher nucleation rate as compared to growth rate, while a six molar concentration produces nanospheres (ca. 15 nm) due to a higher growth rate. The progress of the reaction, synthesis mechanism and surface functionalization of the Ni nanostructures were analyzed by Fourier transform infrared (FT-IR) spectroscopy. The interaction of Ni2+ with electron rich sites in the CSO resulted in the reduction of Ni2+ to Ni(0). The cubic lattice of the synthesized nanostructures, phase and preferred growth direction of the nanorods along the [200] plane were determined by correlation of X-ray diffraction (XRD) results with that of transmission electron microscopy (TEM) analysis. The adsorption ability of the magnetic Ni nanostructures was analyzed using parameters such as the adsorption kinetics (rate and order of adsorption), maximum adsorption capacity (250 mg g−1 (nanospheres) and 142 mg g−1 (nanorods)), effect of initial concentration of dye/adsorbent and contact time. The Langmuir and Freundlich adsorption isotherms were employed for an understanding of the nature (chemisorption or physisorption) of the dye adsorption. The magnetic nature of the adsorbent helps in the fast, economical separation of an adsorbed particle in comparison to non-magnetic dye adsorbents. The better and favorable adsorption (RL value) of the dye on the synthesized Ni nanostructures, makes them a potential adsorbent for the removal of toxic dyes from industrial effluents.

Use of Forestry Wastes for Biosorption of Dyes and Cr (VI)

The pine cone and oak cups pulp were used as low‐cost adsorbents for the removal of basic (Basic Red 18) and acidic (Acid Red 111) dyes and Cr (VI) from aqueous solutions. The adsorbents were modified by HNO3 to improve their biosorption capacity. The adsorbents were characterized using scanning electron microscopy and FTIR spectroscopy. The zeta potential was determined as a function of the pH, in order to explain the effect of pH on electrostatic adsorption ability of biosorbent. Modification of adsorbents with nitric acid led to an increase in accessibility of some functional groups on the surface or a decrease in negativity of surface charge. The modification of pine cone increased its adsorption capacity for the basic dye, whereas the modification of oak cups pulp decreased the adsorption ability for basic dye to some extent. The adsorption isotherms fitted the Langmuir model. The adsorption capacities were found to be 142.85, 158.73, and 156.20 mg g‐1 for modified and raw pine cone and oak cups pulp, respectively. The acidic dye and Cr (VI) adsorptions were much lower compared to basic dye on all tested adsorbents. The results indicated that the forest wastes (pine cone and oak cups pulp) were an attractive candidate for basic dyes from aqueous solution.

Effects of heat treatment on the dye adsorption of ZnO nanorods for dye-sensitized solar cells

Well-aligned ZnO nanorods for the photoelectrode of dye-sensitized solar cells (DSSCs) were grown via a sonochemical method, and the heat-treatment effects on the dye adsorption in the DSSCs were studied. The heat treatment of well-aligned ZnO nanorods was performed at 200 ∼ 500 °C for 1 h, which was immediately followed by the dye adsorption. The dye amounts adsorbed in the ZnO nanorods were estimated from the UV-Vis absorbance by using Beer-Lambert’s law. The efficiency of the DSSCs with ZnO nanorods was measured to investigate the heat-treatment effects of ZnO nanorods on the dye adsorption properties. The heat-treatment of ZnO nanorods was found to yield a change in their dye adsorption ability, resulting in a change in the efficiency of the DSSCs.

Effects of the aspect ratio on the dye adsorption of ZnO nanorods grown by using a sonochemical method for dye-sensitized solar cells

Well-aligned ZnO nanorods for the photoelectrode of dye-sensitized solar cells (DSSCs) were grown via a sonochemical method, and the effects of their aspect ratios on the dye adsorption in DSSCs were studied. The control of the aspect ratio of well-aligned ZnO nanorods was performed by tuning the mole concentration of zinc acetate dehydrate in the range of 0.04–0.06M. The dye amounts adsorbed in the ZnO nanorods were estimated from the UV-Visible absorbance by using the Beer-Lambert law. The efficiency of DSSCs with ZnO nanorods was measured to investigate the effects of the aspect ratio of the ZnO nanorods on the dye adsorption properties. A change in the aspect ratio of the ZnO nanorods was founded to yield a change in their dye adsorption ability, resulting in a change in the efficiency of the DSSCs.

Hierarchical TiO2 nanorod array for dye-sensitized solar cells

A novel hierarchical TiO2 nanorod array was obtained by fabricating corolla-like TiO2 nanorod array directly on the tips of TiO2 nonarod array through a facile two-step hydrothermal method and studied for improved energy conversion efficiency in dye-sensitized solar cells (DSSCs). The DSSC based on the hierarchical TiO2 nanorod array exhibited an energy conversion efficiency 2.7 times higher compared with the DSSC based on the pure nanorod array. The higher energy conversion efficiency was attributed to the remarkably enhanced short-circuit photocurrent density, which results from the larger dye adsorption and better light-scattering ability of the hierarchical TiO2 nanorod array.

Pore size and surface area control of MgO nanostructures using a surfactant-templated hydrothermal process: High adsorption capability to azo dyes

Dioctylsulfosuccinate sodium surfactant (AOT) was selected as a structure-directing agent to prepare mesoporous MgO adsorbent by a hydrothermal method. The anionic AOT surfactant combines with Mg(OH)2 crystallites to form AOT·Mg(OH)2 micelle colloids by hydrogen bonding and electrostatic attraction to template the mesopores with diameter of 10–20nm in MgO nanoplates The whole process is composed of three stages: nucleation, orientation growth, and porecreating. The results demonstrated that the presence of AOT surfactant was essential to produce the mesopores and to adjust the structural parameters of the nanoplates. Because of their higher specific surface area and porous structure, the MgO materials exhibit a satisfactory adsorptive property to three typical azo dye pollutants, Congo red (471–588mg/g), Methyl orange (∼370mg/g) and Sudan III (∼180mg/g), and good performance for decolorization of low-concentration dyes. The highly adsorption capacities of the adsorbents are ascribed to their mesoporous structures which can provide more interaction sites, facilitate the mass diffusion in pores and help the dye molecules to contact the adsorptive sites more easily. The present work provided an alternative approach for preparation of inorganic adsorbent with controlled porous structures and high adsorption ability for hazardous dyes.

Preparation of Al-doped ZnO nanocrystalline aggregates with enhanced performance for dye adsorption

Al-doped ZnO (AZO) nanocrystalline aggregates (NCAs) were prepared by a low cost colloid chemistry method and effects of the Al-doped concentration on the morphological and structural properties of the AZO NCAs were studied. The dye adsorption ability of the AZO NCAs with various Al-doped concentrations was also investigated. Results indicate that the doping of the Al ions not only does not change the wurtzite structure of the ZnO crystal but also can reduce the crystallite grain size and the particle size distribution of the NCAs, which gives them a higher specific surface area and dye adsorption ability than that of the ZnO NCAs. The as-prepared AZO NCAs would be a promising material to be applied in the dye sensitized solar cells and water treatment.

Fabrication of Nanosheet/Nestlike Nanoarray Hierarchical TiO<sub>2</sub> Film for Dye-Sensitized Solar Cell

A hierarchical configuration of TiO2 nanoarray film, comprising a nestlike TiO2 nanoarray layer integrated with a nanosheet network overlayer, was constructed. The hierarchical TiO2 film was obtained by the post-hydrothermal treatment with NaOH solution on hydrothermally synthesized TiO2-derived nanostructured arrays grown on fluorine-doped tin oxide substrate (FTO). The TiO2 films were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy, and absorbance spectroscopy. FE-SEM shows that the hierarchical TiO2 film with a thickness of 1.5 mu m is composed of a nanosheet overlayer (similar to 0.2 mu m height) and the nestlike nanoarray layer (similar to 1.3 mu m height). XRD patterns display that the TiO2 films have pure anatase phase structure. UV-Vis spectra reveal enhanced light scattering and dye adsorption ability of the hierarchical TiO2 film. For the dye-sensitized solar cell (DSSC) based on the nanosheet/nestlike nanoarray hierarchical TiO2 film, a short-circuit current (J(sc)) of 7.79 mA.cm(-2), open-circuit voltage (V-oc) of 0.80 V, fill factor (FF) of 0.40, and photoelectric conversion efficiency (eta) of 2.48% are achieved. Within the dye-sensitized solar cell, the photoelectric conversion efficiency of the hierarchical TiO2 film was nearly ten times higher than that of nanostructured array film.

Research on Photoelectric Properties of Nanowires Doped DSSC

TiO2light anode film is one of the most important part of DSSC. But the microscopic structure of nano-Tio2is not perfect,it exists the problem such as big or small size, excessive internal, insufficient specific surface area which dye and electronic adsorption ability is limited. The micron ball mainly constituted by nanowires is manufactured through experiments in this article,and it is doped into P25 paste in appropriate proportion. The new method that improving the efficiency of DSSC can be summarized by improving TiO2film microstructure through analysising and contrasting in experiments.

Increase in efficiency of dye-sensitized solar cells by porous TiO 2 layer modification with gadolinium-containing thin layer

Modified with gadolinium-containing layer, nanoporous titania electrode and its application in dye-sensitized solar cells were reported. The electrode prepared was characterized with UV-Vis and X-ray diffraction (XRD) techniques. The amount of gadolinium was measured with inductively coupled plasma-optical emission spectrometry (ICP-OES) experiments. The modified electrode showed reduced N3 dye adsorption ability, but increased light conversion efficiency in comparison with the non-modified electrode. The overall conversion efficiencies, determined under 400 W/m 2 irradiation with tungsten-halogen lamp at room temperature, were 0.55% for non-modified and 0.74% for modified electrodes.

Performance Improvement of Zinc Oxide Photoanode-Based Dye-Sensitized Solar Cells by Multi-Walled Carbon Nanotube

Unique electrical and surface-to-volume properties of carbon nanotubes have made these conductive molecules highly attractive in many applications. In this work, the influence of multi-walled carbon nanotubes into a zinc oxide active layer of dye-sensitized zinc oxide solar cell has been investigated. With this method, a significant improvement in the performance of the solar cell has been achieved. Compared to the typical zinc oxide photoelectrochemical cells, the photocurrent-voltage characteristics of the fabricated cell containing 0.05 percent by weight of carbon nanotubes in the metal oxide film displayed a higher short-circuit photocurrent, consequently caused an increase of the solar-to-electricity conversion efficiency by a factor of approximately 1.4. Further increase of the conductive carbon material resulted in a decrease of the energy conversion of the photovoltaic cell. The enhancement of the energy conversion at this optimum carbon nanotube loading may be attributed to the dye-adsorption ability and the electrochemical activity of the composite photoanodes. The fabricated photovoltaic cells with the highest efficiency exhibited the maximum dye adsorption intensity and the minimum charge transfer resistance, as measured by ultraviolet-visible spectroscopy and electrochemical impedance spectroscopy, respectively.

Light scattering enhanced photoanodes for dye-sensitized solar cells prepared by carbon spheres/TiO 2 nanoparticle composites

Incorporating scattering centers in the nanocrystalline photoanode or additional scattering layers on the nanocrystalline photoanode is an effective way to enhance the light harvest efficiency (LHE) of the photoanode and the performance of dye-sensitized solar cells (DSSCs). In this work, mesoporous photoanodes were fabricated based on the composites of anatase TiO 2 nanoparticles and carbon spheres. The holes were left after calcination thus serving as the light scattering centers in the photoanode. The size and the amounts of the holes were adjusted by changing the size (250, 500 and 700 nm) and concentration (5, 10, 15 and 20 wt% of the TiO 2 nanocrystallines) of the carbon spheres in the slurry. The light scattering ability and the dye adsorption of the photoanodes with holes of varied size and contents were investigated. The holes left by calcinating the carbon spheres increased the light scattering of the photoanode. However, the increased light scattering ability offset the dye adsorption ability of the photoanode by high amounts of carbon spheres modification. The performances of the DSSCs are investigated under the simulated sunlight and the incident light (400–780 nm). The DSSC with photoanode made from the slurry with 500 nm and 15 wt% carbon spheres exhibited the opitimized performance (Jsc = 14.8 mA cm −2, Voc = 0.657 V, FF = 0.703 and η = 7.2%), much better than the DSSCs with photoanode made by the pure TiO 2 nanocrystalline (Jsc = 11.7 mA cm −2, Voc = 0.645V, FF = 0.699 and η = 5.55%) and other photoanodes, indicating it best balanced the controversy of the enhanced light scattering ability and the decreased dye adsorption. The incident-photo-to-electric conversion efficiency test indicated the highest LHE of the 500 nm and 15 wt% carbon spheres modified photoanode.

Shape-Controlled Synthesis of Cuprous Oxide Nanocrystals via the Electrochemical Route with H<SUB>2</SUB>O-Polyol Mix-Solvent and Their Behaviors of Adsorption

With H2O-polyols (glycerol, ethylene glycol and polyethylene glycol 400) mix-solvent as media in the NaCl-NaOH-NaNO3 electrolytic system, we developed a simple and efficient electrochemical route for the synthesis of Cu2O nanocrystals with different morphology. The SEM results indicated that electrolytic media and current density had a great influence on the shape of Cu2O crystals. The mono-disperse and uniform sphere Cu2O nanoparticles could be readily obtained in H2O-glycerol (or H2O-ethylene glycol) mix-solvent (1:1 volume ratio) and current density 5 mA/cm2. The sphere Cu2O nanoparticles exhibit excellent adsorption ability for organic dyes (methyl orange, fuchsin acid and methyl blue), which is obviously superior to that of the irregular shape Cu2O crystals prepared in H2O-PEG400 (polyethylene glycol 400) mix-solvent. The present work further confirmed that the adsorption ability of Cu2O crystals was related to their size and shape.

Preparation of sub-micron size anatase TiO2 particles for use as light-scattering centers in dye-sensitized solar cell

The sub-micron size anatase TiO2 particles with size about 0.2-0.3 μm were synthesized with basic peptizing agent and hydrothermal method and added into TiO2 film as light scattering center. The addition of the sub-micron size anatase TiO2 particles enhanced light scattering and dye adsorption abilities of the TiO2 film. When the weight proportion of the sub-micron size/nano-size TiO2 particles in the TiO2 film attained to 1.25/10, the highest energy conversion efficiency about 7.41% was obtained, which was 23% enhancement comparing with the TiO2 film containing pure nano-size TiO2 particles. It presented an efficient way for improving the photovoltaic performance of dye-sensitized solar cell.

Collagen stabilization and modification using a polyepoxide, triglycidyl isocyanurate

This paper reports a study on the crosslinking behaviour of dermal collagen with the polyepoxide triglycidyl isocyanurate (TEPIC), which is thought to introduce a specific stabilization effect into a collagen matrix. TEPIC shows a higher reactivity towards collagen compared to glycerol triglycidyl ether, a water-soluble epoxide with the same tri-functionality but having an aliphatic backbone in its molecular structure, and one of the most commonly used epoxide monomers reported in the literature. Significant stabilization of the collagen matrix treated with TEPIC has been shown in our work, based on the examination of hydrothermal properties, thermal degradation and enzyme degradation properties, amino acid analysis and measurement of mechanical properties. Collagen's dimensional stability was also found to be improved, from tensile testing and fibre morphology observations (here by scanning electron microscopy). The overall stabilization effect of TEPIC is comparable or better than the conventionally used crosslinker, glutaraldehyde, and so implies that a stable three-dimensional, covalent network is formed by the TEPIC within the collagen supermolecule, instead of the two-dimensional crosslinked bridging systems in the case of glutaraldehyde. These results also suggest that the additional stabilization by TEPIC may relate to its triazine nucleus, which introduces a more rigid conformation into the collagen polypeptide chains. In addition, the treated collagen matrix has been found to have increased adsorption ability for anionic dyes. This study has shown that TEPIC can be considered as one of the more effective aldehyde alternatives, which could have a potential significance in leather and textile industrial applications.

Dipeptide‐Based Low‐Molecular‐Weight Efficient Organogelators and Their Application in Water Purification

The development of new low-molecular-weight gelators for organic solvents is motivated by several potential applications of gels as advanced functional materials. In the present study, we developed simple dipeptide-based organogelators with a minimum gelation concentration (MGC) of 6-0.15 %, w/v in aromatic solvents. The organogelators were synthesized using different L-amino acids with nonpolar aliphatic/aromatic residues and by varying alkyl-chain length (C-12 to C-16). The self-aggregation behavior of these thermoreversible organogels was investigated through several spectroscopic and microscopic techniques. A balanced participation of the hydrogen bonding and van der Waals interactions is crucial for efficient organogelation, which can be largely modulated by the structural modification at the hydrogen-bonding unit as well as by varying the alkyl-chain length in both sides of the hydrophilic residue. Interestingly, these organogelators could selectively gelate aromatic solvents from their mixtures with water. Furthermore, the xerogels prepared from the organogels showed a striking property of adsorbing dyes such as crystal violet, rhodamine 6G from water. This dye-adsorption ability of gelators can be utilized in water purification by removing toxic dyes from wastewater.

Transformation of layered titanate nanosheets into nanostructured porous titanium dioxide in polycation solution

Nanostructured porous TiO 2 particles constructed from nanorod-like crystals were prepared from a layered titanate nanosheet precursor. The synthesis process includes two steps: construction of a porous nanostructure by assembling the nanosheets with poly (diallyldimethylammonium) (PDDA) polycations, and topotactic transformation of the nanostructured titanate nanosheets into anatase-type TiO 2 nanocrystals by hydrothermal reaction. The reaction process and nanostructured porous particles were characterized by XRD, DTA-TG, SEM, TEM analyses, and measurements of specific surface area, pore size distribution, ruthenium dye (N719) adsorption, and photocatalytic activity. The morphology of the porous particles is dependent on the PDDA concentration in the reaction system. Spherical particles constructed from nanorod-like anatase crystals can be prepared under the high PDDA concentration conditions. The topotactic transformation reaction from the titanate nanosheet to anatase resulted in the formation of anatase nanocrystals which preferentially expose the (0 1 0) plane of anatase on the surface. The surface of the nanostructured porous anatase particles shows high N719 dye adsorption ability and high photocatalytic activity, which have potential application in dye-sensitized solar cells.

Novel PAAm/Laponite clay nanocomposite hydrogels with improved cationic dye adsorption behavior

A nanocomposite (NC) hydrogel was prepared by incorporating the nanoclay (Laponite (Lap) XLS) into a poly(acrylamide) (PAAm) hydrogel by the in situ polymerization method without any organic cross-linker. The parameters pertaining to the swelling ( Q) and diffusion ( D) of water for the PAAm/Lap NC hydrogels were estimated. The crystal violet (CV) dye adsorption properties of the PAAm/Lap NC hydrogels were investigated. The adsorption of CV dye by the hydrogel increases as the concentration of the dye increases. The cationic dye adsorption ability of the NC hydrogel increased with increasing clay content in the NC hydrogel. The NC hydrogels containing CV dye were characterized by FT-IR. A sigmoidal type of adsorption isotherm was observed for the CV-NC hydrogels. The effects of heat treatment on the dye adsorption behavior of the NC hydrogels were studied.