Geometry transformation of ionic surfactants and adsorption behavior on water/n-decane-interface: calculation by molecular dynamics simulation and DFT study

Multi-stage adsorption of methyl orange on the nitrogen-rich biomass-derived carbon adsorbent: DFT and MD evaluation

Dyes that are released into the environment may have negative effects on living organisms. To address this issue, a biomass-derived carbon adsorbent made from Enteromorpha was tested for its ability to remove methyl orange (MO) from wastewater. The adsorbent was found to be effective in removing MO, with a 1:4 impregnation ratio producing an adsorbent that could remove 96.34% of MO from a 200 mg/L solution using only 0.1 g of adsorbent. At higher concentrations, the adsorption capacity increased up to 269.58 mg/g. Through molecular dynamics simulations, it was discovered that after mono-layer adsorption reached saturation, the remaining MO molecules in solution formed hydrogen bonds with the adsorbed MO, which led to further aggregation on the adsorbent surface and increased adsorption capacity. Additionally, theoretical investigations revealed that the adsorption energy of anionic dyes increased with Nitrogen-doped carbon materials, with the pyrrolic-N site having the highest adsorption energy for MO. The carbon material derived from Enteromorpha showed promise in treating wastewater containing anionic dyes, thanks to its high adsorption capacity and strong electrostatic interaction with the sulfonic acid groups of MO.

Methionine-Derived Organogels as Lubricant Additives Enhance the Continuity of the Oil Film through Dynamic Self-Healing Assembly

(S)-2-((1-(Hexadecylamino)-4-(methylthio)-1-oxobutan-2-yl)carbamoyl)benzoic acid (HMTA) was efficiently synthesized and successfully applied as an additive to several types of blank lubricant oils. Initially, HMTA self-assembles to fibrous structures and traps blank lubricant oils to form gel lubricants. The prepared gel lubricants show thermo-reversible properties and enhanced lubricating performance by 3∼5-fold. X-ray photoelectron spectrometry of the metal surface and the quartz crystal microbalance illustrated that there are no obvious interactions between HMTA and the metal surface. The results of Fourier transform infrared spectroscopy and X-ray diffraction further confirm that inter/intro-molecular H-bonding interactions are the main driving force for the self-healing of HMTA. Finally, molecular dynamics (MD) simulations show that the number of noncovalent H-bonding interactions fluctuates with time, and this highly dynamic H-bonding network could regulate the self-assembly process and result in the self-healing property of the HMTA organogel, which is consistent with the results of the step-strain tests. Especially, the Hirshfeld independent gradient model method at the quantum level demonstrated that C8/C9 aromatics of 500SN have strong π-π stacking interactions with the aromatic heads of HMTA and van der Waals interactions with the hydrophobic tails of HMTA, which disrupt the self-assembly behavior of the 500SN model. Therefore, the calculation studies offer a rational explanation for the superior lubricant property of the PAO10 gel as compared to that for 500SN.

Layer-by-Layer Assembly of Polystyrene/Ag for a Highly Reproducible SERS Substrate and Its Use for the Detection of Food Contaminants

Polystyrene (PS) spheres were prepared through an emulsifier-free emulsion polymerization method, in which the reaction time, ionic strength, concentrations of copolymer were studied in detail. The resulting PS microspheres and Ag nanoparticles were used to construct a surface enhanced Raman scattering (SERS) substrate by a layer-by-layer assembly method. A relatively uniform distribution of PS/Ag in the films was obtained, and the multilayer substrate presented excellent SERS reproducibility and a tunable enhancement effect. The SERS substrate was used for detecting harmful pesticides (malachite green and dimetridazole) in food samples, with a limit of detection as low as 3.5 ppb. The obtained plasmonic composite has a promising future in the field of SERS sensing.