Adsorption of different types of surfactants on graphene oxide

Sha

Adsorption Science & Technology

et al. 2021

Endocrine-disrupting chemicals (EDCs) have attracted much attention in recent years. Graphene-based materials (GMs) have been deemed as excellent adsorbents for the removal of EDCs. The objective of the present study was to understand how the cationic surfactants (CTAB; cetyltrimethylammonium nitrate) affect the adsorption of EDCs (17α-ethinyl estradiol (EE2) and bisphenol A (BPA)) on graphene oxide (GO), reduced graphene oxides (RGOs), and the few-layered commercial graphene (CG). It was observed that the presence of CTAB showed different effects on the adsorption of EDCs to different GMs. The adsorption of EDCs on GO was enhanced because of the enhanced hydrophobicity of GMs after the adsorption of CTAB and the newly formed hemimicelles by the adsorbed CTAB, which could serve as the partition phase for EDCs. Moreover, the electron donor-acceptor interaction and cation bridging effect of the –NH4+ group of the adsorbed CTAB between EDCs and GMs could also enhance the adsorption of EDCs to GMs. With the increase of the extent of GM reduction, the adsorption enhancement by the presence of CTAB weakened. This could be attributed to the competition and pore blockage effect caused by the adsorbed CTAB. It is worth noting that the enhancement of CTAB on the adsorption of BPA to GMs was more profound than that of EE2. This is likely because the pore blockage effect plays a less important role in the adsorption of BPA due to its smaller molecular diameter and deformable structure.

Section: Effects Of Ctab On Adsorption Of Edcs Were Varied Onmentioning

confidence: 75%

Adsorption of 17α-Ethinyl Estradiol and Bisphenol A to Graphene-Based Materials: Effects of Configuration of Adsorbates and the Presence of Cationic Surfactant

Sha

Adsorption Science & Technology

et al. 2021

“…The order of the assay buffer preparation steps was important; the initial non-covalent modification of GO with SDS before its exposure to BSA was key to preventing GO aggregation. SDS may have stronger adsorption to GO than other surfactants [55]; however, as a blocking agent, it did not inhibit probe DNA adsorption. Our results were consistent with observations that the use of GO surface-blocking agents could increase DNA biosensor sensitivity [59].…”

Section: Discussionmentioning

confidence: 85%

“…Among a range of common surfactants spanning cationic, anionic, non-ionic and zwitterionic states, Triton X-100, Tween-20 (both neutral and non-ionic) and SDS (anionic), unlike zwitterionic or positively charged alternatives, maintained a good oligonucleotide biosensor response [54]. Hydrophobic interactions played an important role in the binding of either SDS or Triton X-100 to GO [55]. However, above 1 mM MgCl 2 , the oligonucleotides were strongly bound to the GO and both Triton X-100 and Tween-20 were only partially effective at relinquishing this strong binding.…”

Section: Discussionmentioning

confidence: 99%

“…However, above 1 mM MgCl 2 , the oligonucleotides were strongly bound to the GO and both Triton X-100 and Tween-20 were only partially effective at relinquishing this strong binding. Thus, this set of conditions was criticized as establishing GO-oligonucelotide binding that may be too strong for establishing effective desorption-based biosensors [55]. An additional concern was that Mg 2+ ions may assist DNAse I binding activity [56], destabilizing the DNA sensor performance.…”

Section: Discussionmentioning

confidence: 99%

“…SDS could markedly reduce non-specific binding in hybridization reactions [57], with the additional benefit of an ability to suppress nuclease activity. This surfactant was preferred to Triton X-100 or Tween-20 for maintaining GO as a stable colloid [55,58] and, above a 40 µM concentration, SDS could maintain stable graphenic colloidal suspensions for over a year [21]. The order of the assay buffer preparation steps was important; the initial non-covalent modification of GO with SDS before its exposure to BSA was key to preventing GO aggregation.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Oligonucleotide Detection and Optical Measurement with Graphene Oxide in the Presence of Bovine Serum Albumin Enabled by Use of Surfactants and Salts

2020

As graphene oxide-based oligonucleotide biosensors improve, there is a growing need to explore their ability to retain high sensitivity for low target concentrations in the context of biological fluids. Therefore, we innovatively combined assay milieu factors that could influence the key performance parameters of DNA hybridization and graphene oxide (GO) colloid dispersion, verifying their suitability to enhance oligonucleotide–GO interactions and biosensor performance. As a model system, we tested single-strand (ss) DNA detection in a complex solution containing bovine serum albumin (BSA) and salts with surfactants. A fluorescein conjugated 30-mer oligonucleotide ssDNA probe was combined with its complementary cDNA target, together with solute dispersed GO and either non-ionic (Triton X-100 and Tween-20) or anionic sodium dodecyl sulfate (SDS) surfactants. In this context, we compared the effect of divalent Mg2+ or monovalent Na+ salts on GO binding for the quench-based detection of specific target–probe DNA hybridization. GO biosensor strategies for quench-based DNA detection include a “turn on” enhancement of fluorescence upon target–probe interaction versus a “turn off” decreased fluorescence for the GO-bound probe. We found that the sensitive and specific detection of low concentrations of oligonucleotide target was best achieved using a strategy that involved target–probe DNA hybridization in the solution with a subsequent modified “turn-off” GO capture and the quenching of the unhybridized probe. Using carefully formulated assay procedures that prevented GO aggregation, the preferential binding and quenching of the unhybridized probe were both achieved using 0.1% BSA, 0.065% SDS and 6 mM NaCl. This resulted in the sensitive measurement of the specific target–probe complexes remaining in the solution. The fluorescein-conjugated single stranded probe (FAM–ssDNA) exhibited linearity to cDNA hybridization with concentrations in the range of 1–8 nM, with a limit of detection equivalent to 0.1 pmoles of target in 100 µL of assay mix. We highlight a general approach that may be adopted for oligonucleotide target detection within complex solutions.

Use of MCM‐41 as an Efficient Adsorbent for Removal of Nonionic Surfactant from Aqueous Solutions

Benghar

Zanjanchi

Sohrabnezhad

2021

CLEAN Soil Air Water

The as‐synthesized MCM‐41 and its modified forms are used as adsorbents for the removal of nonylphenol ethoxylate (NP‐10) from aqueous solutions. The partial template containing MCM‐41 is prepared by treating the as‐synthesized sample with ethanolic ammonium nitrate solution. Complete removal of the template is performed using the calcination process. The prepared adsorbents are characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and nitrogen physisorption techniques. The effect of adsorbent weight, pH, contact time, and initial concentration on the adsorption efficiency is studied. The equilibrium adsorption data are well defined, and they are fitted with Langmuir isotherm model. The maximum adsorption capacities (qm) and pseudo‐second‐order rate constants (k2) are calculated. The best adsorbent, in terms of removal efficiency, results to be the thermally treated MCM‐41, characterized by the highest surface area, and thus with the largest porosity. Specifically, the removal efficiency for NP‐10 is around 84% (558 mg g−1) with an initial concentration of 700 mg L−1, which is increased to 91% (455 mg g−1) for a 500 mg L−1 initial concentration. Thermodynamic studies depict that the adsorption of NP‐10 onto MCM‐41 is an endothermic process and the spontaneity is controlled by entropy.