Elsevier

Materials Chemistry and Physics

Volume 193, 1 June 2017, Pages 316-328
Materials Chemistry and Physics

The influence of Triton X-100 surfactant on the morphology and properties of zinc sulfide nanoparticles for applications in azo dyes degradation

https://doi.org/10.1016/j.matchemphys.2017.02.040Get rights and content

Highlights

  • Triton X-100 was used as surfactant in ZnS nanopowders synthesis by two methods.

  • Triton X-capped ZnS nanoparticles with high specific surface area were synthesized.

  • A very high capacity for bleaching an azo dye solution was evidenced.

  • Some of ZnS powders properties were crucially modified by the synthesis technique.

Abstract

Herein we report the synthesis, by two different routes, of ZnS nanoparticles capped with Triton X-100 (TX), which were characterized by X-ray diffraction, transmission electron microscopy, high resolution electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy, FTIR spectroscopy, UV–visible spectroscopy, photoluminescence spectroscopy, and surface area measurements. The TX-capped ZnS nanopowders have a very good photocatalytic activity and high specific surface area, depending on the synthesis route; e.g. an azo dye solution is almost complete photobleached in only 60 min (a photocatalytic activity of 97.79%) using TX-capped ZnS nanopowder, with specific surface area of 191 m2/g, and further a photocatalytic activity of 99.75% was achieved in 120 min. Based on the photocatalytic results, the ZnS nanopowders can be considered suitable catalysts for a green, very efficient and quick strategy for removing of organic pollutants from wastewaters.

Introduction

Metal sulfides, mainly as nanoparticles, have applications in a variety of devices, such as solar cells, light-emitting diodes, sensors, thermoelectric devices, lithium-ion batteries, fuel cells and nonvolatile memory devices [1]. The synthesis of metal sulfide colloidal nanoparticles typically consists in a chemical reaction between a metal salt and a sulfide ion precursor, in the presence of capping agents, in order to stabilize the high energy surface of the nanoparticles and protect them from aggregation. The colloidal nanoparticles are synthesized and stabilized in solution by using of organic molecules or polymers which could bind on the particle surface; the linked molecules are often denoted as either surfactants, ligands, or capping agents in the literature [2], [3], [4].

Among metal sulfides, zinc sulfide has focused strong interest in many areas of research, being extensively studied, especially as nanomaterial [3], [4], [5]. However, new aspects are continuously evidenced and ZnS is still of interest for researchers. As an important II–VI semiconducting material, ZnS has wide band-gap energy (3.7 eV) and a large exciton energy (≈40 meV) [1]. Actually, zinc sulfide has band-gap energy mainly in the range of 3.6–3.9 eV, depending on its structure and morphology. Various shapes of ZnS, like spheres, rods, tubes and wires, were successfully prepared; the shape and also the size can be varied from bulk particle to nanocrystal, depending on synthetic route, hence the morphology of the particles can be tuned by varying the reaction parameters [4], [5].

Nanostructured ZnS has versatile potential applications in optoelectronic devices, due to its excellent properties of luminescence and photochemistry (e.g. flat-panel displays, injection lasers, ultraviolet light-emitting diodes, thin film electroluminescent displays, in solar energy power, etc.) [1], [5]. Owing to the highly negative reduction potentials of excited electrons and the rapid generation of electron–hole pairs, zinc sulfide is also used as semiconductor photocatalyst in green synthesis of organic compounds (like substituted tetrazoles [6], xanthene and its derivatives [7], etc.) and in the removing of water toxic organic pollutants (e.g. photocatalytic degradation of azo dyes like reactive black 5 [8], Ponceau S and crystal violet [9], malachite green [10], thymol blue [11], Victoria blue R [12], methyl violet [13], reactive red 43 [14], reactive blue 19 [15], or other pollutants) [1]. ZnS quantum dots doped with metal ions, like Fe3+ [10], [11], [13], Sm3+ [14], Pr3+ [15], etc., can prove superior catalytic activity compared to pure nanocrystals. Furthermore, nanoparticles of ZnS exhibit superior photocatalytic activity because of the increased surface/volume ratio with enhanced redox potential as compared to their bulk counterpart and trapped holes arising from surface defects [9].

The synthesis routes for zinc sulfide are one-pot synthesis, sol-gel technique, hydrothermal method, solid state reaction, etc. [3], [4], [5], [16]. For semiconductors nanoparticles synthesis, various surfactants can be employed in order to form a monolayer on the nanoparticles surface, e.g. carboxylates, sodium citrate, oleic acid, etc., and synthetic polymers (polyethylene glycol, Triton X-100, polyvinyl alcohol, etc.), whose nature may strongly influence the nanoparticles properties [17]. The capping agents play a versatile role in colloidal synthesis of nanoparticles other than stabilizers, often acting as ligands for metal ions forming coordination compounds. The particles shape could be modified in the capping agents presence and, in many cases, capping agents act as a physical barrier to restrict the free access of reagents to catalytically active sites on the particle surface. The so-called “surface clean” nanoparticles generally are not truly naked but they are free of long-chain organic compounds, being stabilized by small molecules, including intentionally added small adsorbates, solvent molecules, solute ions, and gases from the nanoparticle growth or storage surroundings; those small molecules are easily displaced by reactants during catalytic reactions [2].

Having in view the importance of surfactants in the properties of ZnS nanoparticles, herein we report the synthesis of capped ZnS nanoparticles in order to optimize the properties, including photocatalytic properties, which evidenced the surfactant importance (Triton X-100) in nanoparticles structure and properties. All synthesized ZnS samples exhibited good catalytic properties in the discoloration of Congo red solution.

The azo dyes are used in large quantities in textile industry and wastewaters from this contain high amount of dyestuff. The textile dyes often have aromatic structure and do not degrade easily under natural conditions because of their highly photostability; as well, very small amounts of dye in water (less than 1 ppm for some dyes) are visible and undesirable [9].

The Triton X-100 capped ZnS nanoparticles can be used in the organic pollutants photocatalytic degradation from wastewaters.

Section snippets

Materials

The high purity reagents from Sigma-Aldrich (zinc acetate, Zn(CH3COO)2·2H2O; Triton X-100, TX; ammonia aqueous solution, 25%; Congo red; sodium hydroxide, NaOH) and Merck (thioacetamide, TAA; hydrochloric acid 37%, HCl) were used as received, without further purification. Congo red is denoted the disodium salt of 3, 3′-([1,1′-biphenyl]-4,4′-diyl)bis(4-aminonaphthalene-1-sulfonic acid) (CR, C.I. Direct Red 28, M.W. = 696.67 g mol−1, C32H24N6O6S2Na2).

Synthesis of ZnS nanopowders

For the synthesis of zinc sulfide sample

Results and discussion

The influence of capping agents in the synthesis of colloidal metal sulfides nanoparticles was studied in last years. According to some authors, ligands are necessary to stabilize nanoparticles during synthesis but, once the particles have been deposited on a substrate, the presence of the ligands is detrimental for catalytic activity [24], thus the removing of capping agents will be required for a good catalytic activity.

In the present study, we used a very efficient surfactant, Triton X-100

Conclusions

We obtained TX-capped ZnS nanopowders with high catalytic activity by one pot synthesis using thioacetamide as sulfide ion source and Triton X-100 as surfactant. The syntheses were performed in aqueous solution, respective in Triton X-100 as solvent, through two experimental techniques and varying the reaction time.

All the synthesized samples have cubic structure, with the crystallites size under 10 nm, entitling them as nanocrystals. The nanoparticles obtained in absence of water as solvent

References (47)

  • A. Dumbrava et al.

    Properties of PEG-capped CdS nanopowders synthesized under very mild conditions

    Powder Technol.

    (2015)
  • N. Soltani et al.

    Photocatalytic degradation of methylene blue under visible light using PVP-capped ZnS and CdS nanoparticles

    Sol. Energy

    (2013)
  • J. Saien et al.

    Homogeneous and heterogeneous AOPs for rapid degradation of Triton X-100 in aqueous media via UV light, nano titania hydrogen peroxide and potassium persulfate

    Chem. Eng. J.

    (2011)
  • S.G. Dixit et al.

    Some aspects of the role of surfactants in the formation of nanoparticles

    Colloid. Surf. A

    (1998)
  • N.S. Das et al.

    Effect of film thickness on the energy band gap of nanocrystalline CdS thin films analyzed by spectroscopic ellipsometry

    Phys. E

    (2010)
  • R. Rusdi et al.

    Preparation and band gap energies of ZnO nanotubes, nanorods and spherical nanostructures

    Powder Technol.

    (2011)
  • A. Dumbrava et al.

    Investigations on the influence of surfactant in morphology and optical properties of zinc oxide nanopowders for dye-sensitized solar cells applications

    Mat. Sci. Semicon. Proc.

    (2013)
  • S. Kakarndee et al.

    Low temperature synthesis, characterization and photoluminescence study of plate-like ZnS

    Mater. Lett.

    (2016)
  • E. Mosquera et al.

    Low temperature synthesis and blue photoluminescence of ZnS submicron particles

    Mater. Lett.

    (2014)
  • J. Liqiang et al.

    Review of photoluminescence performance of nano-sized semiconductor materials and its relationships with photocatalytic activity

    Sol. Energ Mat. Sol. Cells

    (2006)
  • J. Fowsiya et al.

    Photocatalytic degradation of Congo red using Carissa edulis extract capped zinc oxide nanoparticles

    J. Photochem. Photobiol. B

    (2016)
  • H. Lachheb et al.

    Photocatalytic degradation of various types of dyes (alizarin S, crocein orange G, methyl red, Congo red, methylene blue) in water by UV-irradiated titania

    Appl. Catal. B Environ.

    (2002)
  • U. Jabeen et al.

    Photo catalytic degradation of Alizarin red S using ZnS and cadmium doped ZnS nanoparticles under unfiltered sunlight

    Surf. Interfaces

    (2017)
  • Cited by (10)

    • Novel ZnO-biochar nanocomposites obtained by hydrothermal method in extracts of Ulva lactuca collected from Black Sea

      2023, Ceramics International
      Citation Excerpt :

      The same observations are also for ZnO samples. In absence of any photocatalyst, the concentration of CR under the visible and UV irradiation remained almost constant for 120 min, with a very low decrease of 3.07% under visible [48], respective 1% under UV treatment. The photocatalytic activity of ZnO@C samples is comparable with that of ZnO nanopowders obtained in ULE, being slightly superior to pristine ZnO obtained in the similar conditions; the highest photocatalytic activity was determined for ZnO@C 2 sample, obtained by a two-stages method and assumed to have a higher carbon and lower capping molecules concentration compared to ZnO@C 1.

    • Synthesis of nano-ZnS by lyotropic liquid crystal template method for enhanced photodegradation of methylene blue

      2022, Inorganic Chemistry Communications
      Citation Excerpt :

      As a wide bandgap semiconductor sulfide, zinc sulfide(ZnS) has two structures of hexagonal wurtzite (α-ZnS) and cubic sphalerite (β-ZnS)[5]. Compared with TiO2, ZnS has a similar bandgap width (3.7 eV) and a larger exciton binding energy (40 meV)[6]. Due to its high negative reduction potential and holes formed by its defects, ZnS shows good photocatalytic degradation property[7], which has been widely used in the field of photocatalysis[8–11].

    • Electrophoretic deposition of carbon/ZnS composite electrode layers

      2020, Materials Chemistry and Physics
      Citation Excerpt :

      Zinc sulphide is a semiconductor which is widely employed in fields like batteries [1], solar cells [2–4], fuel cells [5], photocatalysts [6–9], photoactive materials for waste water treatment [10], sensors [11,12] and as protective material or band gap modifier in core–shell materials.

    View all citing articles on Scopus
    View full text